Tag: pollinators

Rodents and Other Non-Flying Mammal Pollinators

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist, CMNS, Department of Entomology
*Assistant Professor, CMNS, Department of Entomology. Twitter: @Analyssi

Note: This is the eighth article of our series on pollinators. Initial articles can be found in the vegetable and fruit headline news June, July, August and September 2020 special editions and Maryland Agronomy News Blog.

Introduction

There are multiple species and groups of pollinators; and those capable of going airborne are generally more efficient at transferring pollen. Among which, flying insects (e.g., bees, butterflies), birds and bats are the most common, well recognized and intensively studied. Howbeit, many non-flying mammals are also important pollinators; and research in multiple continents (Australia, Africa, South America, etc.) has shown that non-flying mammals (i.e., marsupials, primates and rodents) visit and are quite successful at pollinating flowers. They tend to be more ubiquitous in the tropics where they help pollinate large trees and also assist in the dissemination of their fruits.

Therophily or pollination by non-flying mammals (NFMs) was first described in the 1930s; and worldwide these pollinators have been reported to visit at least 85 plant species. Incidentally, therophilous pollinators were characterized as NFMs mainly to distinguish them from bats. Arguably, the best examples of this pollinator group are marsupials (e.g., honey possum) prevalent in Australia, and primates (e.g., monkeys, lemurs) found in territories such as Madagascar. Funnily enough, of the plenteous interactions between plants and their animal pollinators, one of the least foreseeable surprises is represented by rodents (e.g., mice, rats, gerbils, squirrels). Who would have thought that among rodents’ duties are delivering pollen to plants? Yet, rodents are important pollen vectors of many plants. The first description of these animals as pollinators date from the early 1970s in South Africa, where they were observed to pollinate a shrub from the sugarbush genus Protea (Proteaceae, Fig. 1a, b). Since then, they have been reported pollinating other plant families (e.g., Colchicaceae, Cytinaceae, Fabaceae, Melastomataceae, Hyacinthaceae and Ericaceae). Despite these interesting observations, not much research has been directed at determining whether or not flowers are indeed pollinated by these rodents. This article will summarize some known facts about NFM pollinators with a greater emphasis on rodents.

Fig. 1a. Protea flower in Australia, Attribution: 10ixta02 (CC).
Fig. 1b. Protea flower in South Africa, Attribution: icelight (CC).

General floral traits associated with Non-Flying Mammal pollinators

Because plants adapted to pollination by NFMs tend to converge in their morphologies (what is called a “pollination syndrome”), it is generally possible to predict whether plants are pollinated by NFMs by evaluating their floral characteristics. Indeed, plants adapted to pollination by NFMs display some unique vegetative and floral traits that helps protect their valuable pollen and nectar from birds, insects and other non-therophilous pollinators. These flowers are generally large and robust, which is thought to be an acclamation that allows them to withstand the teeth of hungry and aggressive feeders, and are typically arranged as multi-flower inflorescences. Contrasting those pollinated by birds, flowers pollinated by NFMs are often drab in color, but exude a pungent odor sometimes described as musty or yeasty, which assists in their discovery by mammals (e.g., rodents and shrews) that rely mostly on their sense of smell. Flowers generally contain protruded styles and stamens, an abundance of sugar-rich nectar and large amounts of pollen. This structure allows for increased precision in pollen delivery and transfer by NFMs, whom because of their large size are clumsy flower handlers. Some additional clues that suggest plants are adapted to pollination by NFMs include: i) evidence of nondestructive feeding on flower; ii) infrequent insect or bird visitation, and iii) nectar secretion, scent production and floral anthesis synchronized with the most active periods of the interacting NFMs.

Pollination syndromes are specific combinations of floral traits having evolved in adaptation to special pollinator guilds; and traits listed in the aforesaid paragraph represent the pollination syndromes of NFMs. However, NFMs have varying morphologies and foraging behaviors, suggesting that floral features may still differ according to the specific pollinator species within this non-flying guild. For instance, the ability of different species to pollinate a flower may vary according to their size, mode of locomotion, frequency of visitation and constancy to a particular plant species. Non-flying mammals can range in size from miniscule (pygmy possum) to large (monkey) creatures, and their foraging habits differ between nocturnal (e.g., marsupials and most rodents) and diurnal (e.g., primates). Regarding floral features, primate pollinated flowers tend to be unscented and very large, marsupial pollinated flowers are typically in the canopy, and flowers pollinated by rodents are generally at ground level and can be smelly. Further, many floral features associated with the NFM pollination syndrome (e.g., copious amounts of sugar-rich nectar) can be shared with those present in other pollination syndromes, such as those associated with insects and bats. It is for this reason that flowers once thought to be pollinated by bats based on their morphology were eventually discovered to be pollinated by NFMs. This is the case of Mucuna birdwoodiana, which was determined to be primarily pollinated by the masked palm civets, Paguma larvata and the Pallas’s squirrel (aka red-bellied tree squirrel, Callosciurus erythraeus styani, Fig. 2).

Fig. 2. Pallas’s squirrel (Callosciurus erythraeus), aka red-bellied tree squirrel Attribution: news.cgtn.com.

Primate and marsupial pollination

Fig. 3. Red-bellied lemur (Eulemur rubriventer) Attribution: Matt Francey (CC).

Some of the best-known groups of NFM pollinators are those formed by the primates of Madagascar and South America, and the marsupials of Australia. Primate nectar feeding and cross-pollination of flowers was not widely known in the past but is well acknowledged today; and there may be more species of primates involved in pollination than any other group. Specifically, on the island of Madagascar, there are some unique primate pollinators. Some of which include the red-bellied (Eulemur rubriventer, Fig. 3) and black-and-white ruffed (Varecia variegate, Fig. 4) lemurs. The red-bellied lemur has a brush-shaped tongue that helps it effortlessly forage nectar from flowers, and indirectly pollinate Vahimberona and guava. This lemur has been observed browsing on flowers and leaves of over 70 plant species (e.g., the traveler’s palm Ravenala), which makes them also potential pollinators of those plants as well. Interestingly, they also feed at night on eucalyptus flowers, whose flowers are nocturnal. The black-and-white ruffed lemur, which also resides in Madagascar, is the world’s largest pollinator and main pollinator of traveler’s palm. For this, they are uniquely equipped to open their flowers, using their prehensile hands to pull open the tough flower bracts and then stick their long snouts and tongues inside to feed on the nectar. While doing so, pollen sticks to their muzzle and fur, and is subsequently transferred to the next flower where they repeat these motions. Because they feed on fruits, lemurs contribute to plant reproduction and survival also through seed-dispersal, passing viable fruit seeds in their feces. Another unique primate pollinator is the bush baby (galagos) which are among the smallest primates. Bush babies have very large eyes which are advantageous to their nocturnal habits. These tiny primates feed on the white flowers of baobab (Adansonia) trees, eating parts of the flower and, while doing so, transferring pollen. In addition to flowers, bush babies feed on insects, acacia gum, seeds, bird eggs and fruits.

Fig. 4. Black-and-white ruffed lemur (Varecia variegata) Attribution: Tambako The Jaguar (CC).

Small marsupials tend to be nocturnal and cryptic, which makes it an arduous task to monitor them directly. Speaking of small, among marsupial pollinators is the tiny honey possum (Tarsipes rostratus, Fig. 5) of Australia which ranges in mass from 6 to 18 g (0.2 to 0.6 oz) and has a body length of 60 to 90 mm (2.4 to 3.5 in). Honey possums devour pollen and nectar from a variety of flowering plants. Large amounts are consumed from plants belonging to the families Proteaceae, Epacridaceae and Myrtacae. They are the only flightless animal that feeds exclusively on pollen and nectar. Honey possums are adapted morphologically and physiologically to their unique nectar and pollen diet. As such, they have several physical features handy for pollination including grasping feet and a prehensile tail used to wrap around tree branches, which allow them to hang while searching for flowers. It also has an extremely long and specialized extensible tongue, which has a brush-like tip adapted to gathering pollen and nectar. While feeding, its long-pointed snout gets dusted with pollen, which can then be transferred to a different flower. These tiny marsupials are known to pollinate the very specious Australian plant genera Banksia and Eucalyptus.

Fig. 5. Honey possum feeding on banksia. Attribution: Ross Bray (bushheritage.org.au).

Another marsupial pollinator is the sugar glider (Petaurus breviceps), which gliding technique has been compared to that of flying squirrels. Sugar gliders have a flexible diet that may vary according to location and season. For this reason, in addition to nectar and pollen, they feed on plant sap and gum (e.g., from Acacia and Eucalyptus), spiders, small birds, insects and the honeydew secretion of sap-sucking insects. Sugar gliders are important pollinators of native Australian flowering plants. Another glider, the yellow-bellied glider (Petaurus australis) feeds on the nectar of Banksia and Eucalyptus, and their diet consists largely of nectar, pollen and the sap of eucalypts.

Rodent pollination

Multiple species of gerbils, mice, rats and shrews visit flowers, and as they move into a flower to feed on nectar, their heads get dusted in pollen, which can then be transferred to other flowers. Generally, several plant features are linked to the rodent pollination syndrome. Among these traits are robust dull-colored flowers (lack colorful petals that attract insects or birds), yeasty or musty scent, flowering in the winter-spring, the presence of stiff reproductive organs, and easy access to nectar. Inflorescences of plants pollinated by rodents may be hidden deep inside the branches (e.g., Protea nana, P. cordata, Leucospermum arenarium) and are often at or near ground level where they are readily accessible to rodents (aka geoflory). This latter trait is indeed one of the most-commonly present traits in rodent-pollinated plants. Additional features in these rodent-pollinated flowers are abundant pollen, and easily-accessible and copious nectar secreted in the evening and during winter flowering. The latter characteristic is understood to serve the large caloric needs of small mammals, especially during the food-scarce winter time. Therophilous plants that flower in spring are recognized to provide nectar during rodents’ breeding period, when caloric intake can be a major limiting factor. Because of their abundant pollen and nectar, rodent flowers are a popular commodity to rodents due to them being sources of protein (pollen) and sugars (nectar). A great example of a plant being adapted to fulfil the nutritional requirements of their rodent pollinators is certain species of Protea. These flowers present copious amounts of xylose sugars in their nectars, which is rejected by birds but is uniquely adapted to the nutritional abilities of their specialized rodents, the spiny mice. These plant species are not only good nutritional sources for the spiny mice, but they also provide those resources during a period when other food sources are scarce. From this respect, these plants are specifically adapted to allowing the subsistence of these very specific mammal pollinator.

Plant/floral features associated with the rodent pollination syndrome are often used to accurately determine whether plants are rodent-pollinated. For example, the Pagoda lily, Whiteheadia bifolia was hypothesized to be pollinated by rodents on the basis of containing most features listed in the aforesaid paragraph. Later, a study confirmed that the Namaqua Rock Mouse (Aethomys namaquensis, Fig. 6a, b) uses their snout to transfer pollen between Pagoda lily plants. The Pagoda lily period of winter flowering was shown to correspond with a time of food shortage and breeding season of the Namaqua rock mouse. Its flowers are close to the ground and thus reachable by mice. The plant is very robust, especially the stamens, such that they are not damaged during mice visitation. It is not conspicuously colored making it unnoticeable to other pollinators, but which is also adapted to the nocturnal activity of the Namaqua rock mouse.

Fig. 6a. Namaqua rock mouse (Aethomys namaquensis) pollinating Protea humiflora. Attribution: biodiversityexplorer.info).

Though colorless flowers are a well-known trait of the rodent floral syndrome, color plays a role in attracting rodents in some cases. For example, the Chinese orchid, Cymbidium serratum which is pollinated by wild mountain mice, Rattus fulvescens uses color and odor as attractants. The smell is however, stronger at night. Similar to the Pagoda lily, the Chinese orchid flowers when mice are active and other food resources are in short supply, which occurs in early spring. Notwithstanding, uncharacteristic of this rodent pollinated flower, the Chinese orchid doesn’t contain nectar. The food reward is its labellum which is slightly sweet while other flower parts are bitter. While feeding on the labellum, the mountain mouse comes in contact with stigmas and pollinia.

Fig. 6b. Namaqua rock mouse with pollen on nose feeding on Pagoda lily nectar. Attribution: Petra Wester (CC).

Evidence for rodent pollination

Although it is becoming more widely-accepted that rodents are important pollinators, the fact that they are mostly nocturnal poses a challenge in observing their behavior and suggests that the contribution of rodents to plant pollination is currently underestimated. A clear sign that a rodent is indeed involved in a pollination interaction with their preferred plant(s) can be obtained if pollen is found in their feces (ingested through the process of grooming). On this, a study found the hedgehog lily, Massonia depressa pollen on snouts and in the feces of captured rodents. Another clear test for rodent pollination is the observed reduction of seed production in flowers experimentally excluded from rodents. This has been shown in plants such as Leucospermum arenarium.

In some cases, rodents work in concert with other pollinator groups. An example of this is that of hummingbirds and rodents pollinating Meriania sanguinea. Another fascinating case is the one of the chestnut spiny rat (Niviventer fulvescens) and short-nosed fruit bat (Cynopterus sphinx) pollinating Mucuna championii through “explosive” flower openings. Specifically, flowers of these plants remain closed, with their reproductive organs tightly packed within the closed flower. Once a sufficiently-heavy pollinator (e.g., rat, bat) reaches the flower and tries to access its nectar, they trigger with their weight, the release of the pressure built in the flower, which leads to an explosive opening. Through this, the pollen which was tightly packed in the flower prior to the explosion is expelled and lands directly on the pollinator’s face, which transfers it to a different flower during a future flower visit.

Are there any benefits to invasive rodent pollinators?

Fig. 7. Rattus rattus. Attribution: Patricio Novoa Quezada (CC)

Non-native rodents have invaded about 80% of the world’s islands, posing a severe threat to native insular biodiversity. Though invasive species can be disruptive, by feeding on or competing with native organisms and severely disrupting biodiversity; in some instances, it has been suggested that invasive rodents may fulfill pollination niches vacated by endemic pollinators which may have become extinct or threatened because of their invasion. A study conducted in New Zealand suggested that the invasive black rat (aka ship rat, Rattus rattus) partly maintained pollination of three forest plant species, which without this compensation would be currently significantly more pollen-limited. Thus, while the ship rat is known to have a negative impact on biodiversity overall, evidence showed that it contributed to a crucial ecosystem function (i.e., pollination) for some plants on some of the invaded islands. Likewise, another study examining the potential of the same alien black rat (Fig. 7) to pollinate the Australian native plant Banksia ericifolia (Fig. 8), found that although black rats frequently visit B. ericifolia, they were unable to properly compensate for the pollination loss associated to the extinction of their native mammal pollinator. Though these findings suggest that invasive rats may remediate in some cases the loss of pollination associated to the invasion events, many investigations demonstrate that their destruction outweighs their benefits on these islands. This is due to their strong negative effects on other aspects of the native biodiversity and human well-being.

Fig. 8. Banksia ericifolia (Proteaceae), Woody shrub that is native to Australia. Attribution: Alex Proimos (CC)

Summary

Non-flying mammals do not garner much notoriety and excitement as pollinators, and are often overshadowed by showy flying pollinators such as bats, birds and insects (e.g., bees, moths and butterflies). This may be partially due to the fact that these non-flying pollinators are often nocturnal and cryptic, which may cause their contribution to pollination to be underestimated. Despite this, increasing numbers of studies indicate that NFM pollinators are important for dispersing pollen and fruits, and that multiple family of plants have vegetative and floral traits adapted specifically to their pollination. Non-flying mammal pollinators are represented by three main groups: primates, marsupials and rodents. Because of their large size and energy requirements, plants pollinated by these pollinators often contain copious amounts of nectar and pollen. Most plant species pollinated by these animals are present in Africa, South America, South East Asia and Australia. Among all these species, the plant family Proteaceae was the first reported NFM pollinated plant family and is one of the most studied to date. However, with the increase in awareness of the existence of these pollinators, new examples appear regularly, demonstrating that their contribution to pollination may be more common than initially thought. Finally, recent works have shown that invasive rodents can be extremely detrimental to most biodiversity processes on islands and are capable of causing the extinction of native pollinators. Notwithstanding, some invasive rodents are capable of partially compensating for lost pollination services associated with the extinction of native pollinators.

Financial support for the publication of this article is via USDA NIFA EIPM grant award numbers 2017-70006-27171.

 

Bats and Pollination

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist and *Assistant Professor, CMNS, Department of Entomology; twitter: @Analyssi

Note: This is the fourth article of our series on pollinators. Initial articles can be found within the Vegetable and Fruit Headlines News June and July special editions and Maryland Agronomy News Blog.

Introduction

bat upside down in tree
Fig. 1. Flying fox bat hanging from a tree. Photo John (CC)

Bats are the only mammals capable of sustained flight. They make up 20% of all known mammals and consist of at least 1,411 species. Bats live on nearly every corner of the globe and occupy multiple food niches. They play a vital role in insect control, seed dispersal and pollination. Although we tend to think of bats as insectivorous, many of them feed on fruits, and others on nectar and pollen. It is about these latter ones that we will discuss in this article. Most New World nectar bats are highly gregarious, living in colonies of a few hundred to tens of thousands of individuals. Their residences include caves, mines, hollow trees and abandoned buildings. Some Old World nectar bats live in groups within caves and others live solitary lives in trees or may just use a tree to chill for a while (Fig. 1). Nectar bats are long-lived (lifespans of up to 12 years or more) and as pollinators they are essential to the maintenance of ecosystem health, rainforests and global economies, as they ensure the reproduction of many plants. Indeed, bats contribute strongly to the pollination of plants, especially in the tropics, where they are considered pollinators of 1,000 plant species in at least 92 genera and 28 orders. Among these, over 530 species of flowering plants in at least 67 families rely on bats as their major or exclusive pollinators. Similar to moths, bats are nocturnal pollinators; and are just as important in pollinating crops as diurnal pollinators (birds, butterflies and bees). In fact, besides contributing to the reproduction of wild plants, bats also provide pollination services to plants of socio‐economic importance such as durian and mango. Bats play a vital role in maintaining healthy and productive habitats around the world.

Sources of Nutrients

Each bat species has food preferences, and different species may rely on fruits, flowers and/or insects for their survival. Some bats – many of them pollinators – may feed on flowers of economically important commercial crops, such as dates, mangoes and peaches. Other non-nectarivorous species consume massive quantities of insects every night. Insectivorous bats consume very large volumes of insects, including some economically damaging agricultural pests, such as codling moths in California walnut orchards and corn earworm moths that causes damage to cotton, soybeans and tomatoes, as well as June beetles, stink bugs and mosquitos. A single bat can eat hundreds of insects each night. A USGS study conducted in 2011 found that “Insect-eating bats provide pest-control services that save the U.S. agricultural industry over $3.7 billion per year.” A single colony of 150 big brown bats (Eptesicus fuscus) in Indiana was estimated to eat nearly 1.3 million insect pests annually. Thus, bats are arguably the primary predators of night flying insects. Pregnant or nursing mothers of some bat species feed more aggressively, consuming up to their body weight in insects every night. Notwithstanding, the pollinating role of nectar-feeding bats may be of greater importance than the contribution to insectivorous bats to insect reduction.

Bats as vital pollinators

Bats’ importance as pollinator vectors is felt globally. Nectar-feeding bats are found in every continent with tropical ecosystems. Similar to other pollinators, bat contribution to pollination is not equally distributed around the globe, with some regions displaying a higher diversity than others. To this point, most flower-visiting bats are found in Africa, Southeast Asia and the Pacific Islands. As pollinators, bats play a key role in contributing to the reproduction and fruit formation of an extremely large number of plant species. Many of these play key ecological roles and contribute to the subsistence of indigenous human communities around the world, while a couple are also economically important, such as the fruits of the columnar cactus, and the Agaves central to fiber and tequila production. Indeed, some products facilitated by bat pollination include fruits, fibers and timbers.

As indicated earlier, bat pollination occurs in the New and the Old World tropics. In the Old World tropics, several studies have examined the pollination effectiveness of bat pollinators. Flying fox bats (Fig. 1), for instance, are known to pollinate roughly 168 flower species in 100 genera and 41 families. Bats in Australia, pollinate the dry eucalyptus (Myrtaceae) forests, which provides timber and oils to consumers around the world. In the New World, pollinating bats are found in the family Phyllostomidae, and are known as leaf-nosed bats. Balsa trees, which produce the world’s lightest timber, is also bat pollinated. Beyond timber, over 300 species of fruit depend on bats for pollination. Their role as pollinators of tropical crops has been verified for species such as durian, bitter beans, and the fleshy fruits of mangoes, guavas and jackfruit, to name some. Further, some wild bananas are also almost exclusively pollinated by bats (Fig. 2). Indeed, some chiropterophilous (bat-pollinated) plants are so specialized that their reproductive success depends almost completely on bats.

bat visiting a flower
Fig. 2. Eonycteris spelaea visiting a very large banana inflorescence. Photo: ecologyasia.com

In bat-pollinated crops, bats can have a direct impact on crop yield. For example, it was discovered that when the primary pollinators of pitayas – nectarivorous bats in the genus Leptonycteris – were excluded from flowers and flowers were pollinated by other taxa (i.e., diurnal birds and insects), pitaya yield among different cultivars decreased by 35% overall. Further, in the absence of bat pollination, fruit quality decreased markedly within all evaluated cultivars. More specifically, fruits were 46% lighter and 13% less sweet when pollinated by other taxa. Additionally, seed set was markedly lower in the absence of bat pollinators. All of this strongly indicates that the quality of the pollination service was suboptimal when pollination was provided by other organisms. As such, for some plants, birds, rodents or insect pollinators cannot be used as stand-ins for bats.

Bats, Agaves and Tequila. In the New World, nectarivorous bats such as the Mexican long-nosed bats have a very close relationship with Agaves. This species is one of only three nectar-feeding bats in the US, with a range that covers Mexico and the southern parts of Texas, California, New Mexico and Arizona. Mexican long-nose bats can fly extensive distances to gather nectar from specific plants and may visit up to 30 flowers each night to feed on nectar and transport pollen. Although we observe this species in the USA, they are migratory, spending their summers in Arizona and New Mexico, and migrating south into central and southern Mexico for the winter. Nectar is so important to them, that during migration, they follow a “nectar trail” so as to ensure that “fuel” (the sugar in nectars) is available to them along their travels. Interestingly, this species is one of the main pollinators of saguaro, the state cactus of Arizona.

bat visiting a flower at night
Fig. 3. Agave desmettiana being visited by a bat Photo: M. Machado (CC)

Among the many Agaves, one that is at the base of a multimillion-dollar industry, is the tequila blue Agave, which is also bat-pollinated. As in many other pollination interactions, bats are important to the tequila industry (Fig. 3) and the tequila industry is important to bats, and this is so in a pretty interesting way. Tequila is produced using the sugars obtained from the leaves of certain Agaves, and tequila Agaves are pollinated specifically by an endangered species of bats, the lesser long-nose bat (Leptonycteris yerbabuenae; Fig. 4). In fact, the relationship between bats and tequila Agaves is so strong that these bat populations fluctuate in accordance with the success of Agave plants and Agave plants rely solely on bats to pollinate its flowers and reproduce. To boost production, tequila producers do not let their Agaves flower, this takes away a key food resource from bats as well as hinders sexual reproduction in Agaves. Over time, this practice led to two bad situations: bats started to decline and are now endangered of extinction, and the Agave plants lost genetic diversity and became susceptible to diseases that started decimating plantations (more than a third of the plants in some areas were killed-off because of disease!). Recent new management practices have however found a solution to both problems, which is currently supporting the survival of this industry in many regions of Mexico. In participating plantations, some Agaves are allowed to flower, which provides nectar to bats and contributes to their conservation, as well as increases the genetic diversity of Agave plants, protecting plantations from disease outbreaks. This has led to the production of what is today marketed under the label of “bat-friendly tequila”, which is now available across the USA.

bat visiting a flower
Fig. 4. Lesser long-nosed bat. Leptonycteris yerbabuenae) Credit: M. Tschapka/Univ. Ulm

Bat-pollination adaptations

Pollination by bats may be described as a four-step process: 1) bats fly to a plant to drink nectar from their flowers, 2) pollen sticks to the hairs on their body, 3) bats fly to another plant for more food, and 4) bat transfers the pollen from their body to the next plant. Though the process sounds simple, the relationship between bats and plants is one of give-and-take. In fact, over time, plants and their bat pollinators have shared a dependency on one another that is mutually beneficial. For instance, even though bats display many very impressive adaptations for nectar feeding, their contributions to cross-pollination are usually considered to fall in the category of “messy feeders”. In fact, when seeking the nectar, their faces and heads become covered with pollen, which is then transferred to another flower in their next visit. Further, because they are usually much larger than other pollinators, bat pollination tends to strongly damage the flowers, which has led to a number of counter-adaptations in bat pollinated plants.

Pollination interactions usually involve morphological and behavioral adaptations by plants and their pollinators; which is also true for bat-pollination. Starting on the bat side, bats that act as pollinators are adapted to obtain their energy from nectar, and also sometimes from pollen. To do this, they have evolved extremely well-adapted characteristics, such as long tongues (reaching sometimes up to 1.5x the bat’s body length!), “hairy” tongue tips that allow for fast and efficient nectar collection, and hairiness in regions that will eventually come in touch with the plant pollen. Relative to plants pollinated by bats, they have evolved special features to make their nectar and pollen attractive to these nocturnal visitors, and most importantly, easily accessible (Fig. 5). Plants that rely primarily on bat pollinators have thus evolved different morphologies, such as usually hanging ‘pincushion type’ flowers with multiple extended stamens, or ‘bell shaped’ flowers that are able to support the force applied by a bat flying directly into the flower. While pincushion flowers facilitate bat perching while feeding on nectar, bell-shaped flowers vary in size (1 to 3.5 inches) but are usually sturdy enough to support the bat visit. Importantly, while some large bat flowers can be exploited by unspecialized bats, only specialized bats can exploit nectar within small, bell shaped flowers. A common character of bat flowers is that they are white, pale- or dull-colored, and they are usually exposed well-away from the foliage (e.g., on stalks), which makes them stand out from the dark background at night. Bat flowers also tend to open after sunset, just as bats leave their day roosts to feed, and stay usually receptive throughout the night. They are naturally-large, wide-mouthed and sturdy to accommodate a bat’s face and resist its push without being (too) damaged. Thus, many bat-pollinated flowers are shaped like a vase, although some are flat and brushy so as to load a bat’s whiskers with pollen. In addition to their sight, bats use a keen sense of smell to find nectar-producing flowers. While many bat flowers contain a fermenting or fruit-like scent; some have evolved a musty or rotten odor, associated with sulphur-containing compounds. Because bats are not able to hover for long periods of time, nectar offered by bat-flowers is usually very dilute (not viscous) and copious, making it easy to collect and abundant. Further, to make visits to plants more attractive, bat-pollinated plants are suspected to synthesize specifically two bat essential amino acids, thus directly improving their health.

pink flower on a cactus
Fig. 5. Venezuelan Mezcalito columnar cactus (Stenocereus griseus) have evolved in size and shape to accommodate bat pollinators. Photo: colombia.inaturalist.org

Extreme adaptations. Some bats have adaptations that allow them to reach the nectar at the bottom of very deep flowers. The tube-lipped nectar bat of Ecuador (Fig. 6) and the banana bat living on the Pacific coast of Mexico have extraordinarily long tongues to extract nectar from deep within the flower. The rare Anoura fistulata, a nectar-feeding bat from South America, has the longest tongue (proportionally) of all mammals. A. fistulata’s tongue is ~ 8.5 cm long, which is 150% of its body length. It is of no surprise that this species’ tongue is too long for its mouth. Thus, it is kept in their chest cavity between the heart and sternum. Further, there is a subfamily of leaf-nosed bats (Glossophaginae) which contain species that are highly specialized in procuring nectar. Similar to hummingbirds, they can hover in front of a flower while using their extremely long tongue to lap up even small amounts of nectar. These bats also have brushy hairs at the tip of their tongues, which increases the speed at which they can collect nectar during one flower visit, significantly increasing the energetic efficiency of their visits.

bat with tongue out
Fig. 6. Tube-lipped nectar bat. (R. L M. Novaes) Reddit.com

Also falling within the category of extreme cases of adaptation is how echolocation is used to facilitate pollination. It is well known that bats use echolocation when hunting insects. Echolocation is the location of objects by reflected sounds. Practically, bats that rely on echolocation use a sonar system, through which the echoes of sound waves allow them to determine the shapes of surrounding objects. Because the powerful echoes emit higher frequencies and vibrations, bats can use their sonar system to detect the presence of swift flying predators. Less known is bats’ ability to use this highly sophisticated system to find nectar-producing plants. This highly developed system enables some bats to maneuver in dense and clutter-rich vegetation. Recognition of motionless prey and specific plants can be difficult to locate in densely-rich vegetative habitats. Amazingly, some plants have evolved acoustic features in their flowers that acts as sound reflectors, amplifying the echo of the bat’s ultrasonic calls and assisting the bats in finding them even within the dense foliage in tropical rainforests. An exception to this is the case of the mega-bats (Megachiroptera; Fig. 7), who lack a sonar system. This group, relies instead on sight and sense of smell to locate food.

face of a bat
Fig. 7. Tube-nosed bat (Megabat: Pteropodidae). Photos: J. Joel (CC).

Differences with insect pollinators

In comparison to insect pollinators, bats are unique in that they are highly mobile, which makes them invaluable pollen dispersers. For example, the Phyllostomid family of bats can transport pollen up to 800m between trees in Puerto Rico, and leaf-nosed bats (Phyllostomus sp.) in Brazil can transport pollen up to 18 km between trees. Further, because they are covered in fur, bats are able to transport very large amounts of pollen. Related to this, many bats fly tens of kilometers from their day roosts to feeding areas each night, transferring pollen between plants that may be very distant from each other or that grow at very low densities. For this reason, bats are vitally important to maintaining gene flow and genetic diversity among (isolated) plant populations. As we saw earlier, this can have very real consequences on protecting crops from disease spreads and from monumental losses.

Besides pollination, bats provide other services that insect pollinators cannot provide, such as land restoration and plant dispersal. For example, through their droppings, fruit-eating bats (some nectar feeding bats may feed on fruits) spread seeds that are needed to restore cleared or damaged tropical rainforests. Some species of bats swallow large amounts of small seeds while consuming fruits (Fig. 8) which are passed out over clear-cut areas resulting in reforestation. Their travels are believed to continually introduce new plants to various habitats where some establish successfully, helping keep areas of growth highly diversified. Bats known as flying foxes are of particular importance in oceanic islands as they are often the only animals in these areas large enough to transport larger seeds. In some tropical areas of the world, over 90% of the regrowth of the rainforest is due to bat dispersed seeds. An estimated 186 plant products used by humans rely upon fruit bats for pollination and seed dispersal.

bat feeding on fruit
Fig. 8. Bat eating Chiku fruit. Green Baron Pro (CC)

Finally bat droppings (also known as bat guano) serve as a natural fertilizer, contributing high levels of NPK to the soil in which they are integrated. It is common practice in regions where bats roost in colonies to collect their droppings and apply them to fields as fertilizers.

Bat conservation

Bat populations are severely threatened in many parts of the world; and it was suggested that 80% of bat species need research or conservation attention. This is important because as bat populations continue to decline, agriculture, the economies of tropical countries and access to food from many indigenous populations suffer. Two species of nectar-feeding bats, the lesser long-nosed bat and the Mexican long-tongued bat, which migrate from Mexico into Arizona, New Mexico and Texas every spring are currently listed as federally endangered species. The fact that bats contribute so much to pollination is partially why they are protected in many areas. For example, nectarivorous bats are essential to the functioning of agricultural and natural ecosystems in the tropics, yet they are declining due to hunting, and habitat alterations and loss.

Hunting is a major contributor to bat decline. Many species of the large-bodied flying foxes, including important pollinators and seed dispersers, are at considerable risk from hunting pressure, particularly on South Pacific islands and the Asian mainland. In eastern Australia, fruit farmers consider flying foxes to be ‘vermin’ and have eliminated many large roosts. In this respect, establishing and enforcing clear and well-informed educational program and policies can be a game changer for bat protection.

Alterations in habitats due to land-use can result in losses in roosting sites and floral resources, which are major contributors to bat pollination decline. Specifically, landscape fragmentation, habitat loss and degradation can disrupt the mutualistic interactions between bats and plants they pollinate and subsequently negatively impact the establishment and reproduction of full ecosystems. Further, bats of several migratory tree-dwelling species can be killed by wind turbines if they are not properly managed (blades stopped by about 90% of their speed during bat migration times has been recommended). As for all species, conservation success depends on improved conservation practices to ensure bats have access to healthy habitats. Some states with large bat populations are working to ensure that bats have a roosting site after a nighttime of feeding. Protecting feeding habitats and roost sites is critical to their recovery.

Summary

Though usually forgotten as pollinators, bats play a key role in the pollination of many wild plants and crops from tropical regions. Bats and the plants that they pollinate have been engaged in coevolutionary processes for millions of years, and some of their morphological, physiological, and behavioral adaptations are among the most impressive in the world of pollinators. In addition to contributing to plant reproduction, bats play a key role in maintaining plant genetic diversity, and connecting isolated plant populations and promoting their survival.

In relation to direct human benefits, bats contribute to the production of wholesome foods that are at the basis of the nutrition of many indigenous communities around the tropical world. From an industrial perspective, bats play an instrumental role in the agricultural industry. In 2011, it was estimated that the value of all bats to the agricultural industry is ~ $22.9 billion annually, which includes reduced costs of pesticides required to managed insects eaten by bats. From this respect, it is simple to understand why their conservation has been deemed in the best interest of national and international economies.

Financial support for the publication of this article is via USDA NIFA EIPM grant award numbers 2017-70006-27171.

Moths, Butterflies, and Pollination

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist and *Assistant Professor, CMNS, Department of Entomology
University of Maryland

Insect pollinators play an essential role in the maintenance of wild plant diversity and agricultural productivity. Indeed, global studies have shown that the vast majority of plants require animal pollination to produce fruit and seed. In temperate regions, major pollinator groups include bees (Hymenoptera), syrphid (Diptera), as well as butterflies and moths (Lepidoptera). In contrast to bees, Lepidoptera are not considered efficient pollinators of most cultivated plants. Nevertheless, they are vital pollinators of many flowering plants, especially in the wild as well as managed lands such as parks and yards.

Fig. 1. Hawkmoth. Photo: J. Patrick (CC)

The pollinating taxa of Lepidoptera are mainly in the moth families Sphingidae (hawk moths; Fig. 1), Noctuidae (owlet moths) and Geometridae (geometer moths), and the butterfly families Hesperiidae (skippers) and Papilionoidea (common butterflies). The adult stage of these lepidopterans obtains their nutrients and water from nectar of various flowers; and while exploiting flowers for food, pollination may occur. Moths and butterflies have different pollinator niches, as butterflies are very active during the day (diurnal) and visit open flowers during the morning hours and under full sunlight. Contrarily, moths are more active during the evening and night hours (nocturnal). As a response to this, some flowers may seek to increase pollination by changing color during a 24-hour period to attract butterflies during the day and moths at night. For example, Quisqualis indica flowers change color from white to pink to red which may be associated with a shift from moth to butterfly pollination (Fig. 2). A study conducted in China verified that different pollinators are attracted to each floral color stage; primarily moths at night and bees and butterflies during the day. Further, fruit set was higher for white than pink or red flowers indicating that moths contributed more to its reproductive success. While adult butterflies and moths are important pollinators, their larvae – often called caterpillars – may be economically important pests in agricultural, forest and urban environments. In some instances, their status as agricultural villains as caterpillars override their positive image as ecosystem service providers as adults.

Fig. 2. Quisqualis indica. Photo: D. Valke (CC)

Nectar and pollen consumption

Adult butterflies diet choice varies between species, populations, generations, sexes, age groups and individuals. Most adult lepidopterans feed on fluid resources such as nectar, decomposing animals, dung and fruit sap (Fig. 3) and others may not feed at all as adults. Butterflies consume nectar by active suction using their elongated mouthparts (called proboscis), and usually avoid highly concentrated nectar because of its high viscosity.

Fig. 3. Butterfly feeding on fruit – Photo: mrkittums (CC)

Nutritionally, nectar serves as a source of water, carbohydrates and amino acids; the latter allowing butterflies to meet their nitrogen requirements. Interestingly, butterfly-pollinated flowers tend to have higher concentrations of amino acids than do flowers pollinated by bees and other animals. This is remarkable since insects like butterflies, whose larval stages feed on plant foliage and adult stages on nectar have long been assumed to obtain most or all of their nitrogen-rich compounds needed for reproduction from larval feeding. Going against this assumption, it has been shown that both nectar consumption and larval food intake can affect the life span and fecundity (number of offsprings produced) of some butterfly species. For example, a recent study found that nitrogen-rich compounds (amino acids) present in nectar significantly increased the fecundity of the nectar-feeding butterfly Araschnia levana. However, their fecundity was enhanced only if the female fed on a poor-quality plant as a larva. This suggests that nectar can act as a necessary dietary complement if a butterfly fed on a nitrogen-poor plant as a larva.

Another nitrogen-rich floral reward is pollen. Nectar-consuming butterflies come into contact with pollen while visiting flowers, but the vast majority of butterflies is unable to feed on pollen. However, butterflies of the neotropical genera Heliconius and Laparus (Lepidoptera: Nymphalidae; Fig. 4) evolved a feeding technique in which amino acids are extracted from pollen grains, rather than fortuitously during their pursuit of nectar. These butterflies collect and accumulate large pollen loads, and the production of saliva helps keep it attached to their proboscis while they gently chew the pollen to consume its amino acids. Pollen feeding is thought to increase Heliconius longevity and egg production.

 

Fig. 4. Heliconius numata with pollen load -Photo: http://www.heliconius.org

Butterflies efficiency as pollinators

It has been suggested that for most plant species, butterflies visit flowers less frequently than bees and deposit less pollen per visit. With a few notable exceptions such as yucca moths, adult lepidopterans show little floral specialization, preferring flowers with large landing surfaces, deep, narrow corollas that can accommodate their elongated mouths, and plants displaying many flowers in close proximity. Butterflies prefer visiting large flower heads, and when searching flowers for nectar, pollen grains attach to various body extremities (e.g., mouth parts, head) depending on the plant’s floral architecture. However, because butterflies’ legs and mouth parts are elongated, most of their body does not enter in direct contact with the plant’s pollen. Consequently, butterflies pick up less pollen on their bodies than bees, and most of it is usually deposited on or around their heads and mouth parts. This pollen is then transferred to the surface of the stigma when the butterfly reaches for nectar in a new flower. Because little pollen is usually carried by butterflies, and the fact that – unlike bees – they don’t have specialized structures for carrying pollen, butterflies are less successful than bees at moving pollen between flowers. Although not as efficient as bees, butterflies can be very effective pollinators, and among the insect fauna they qualify as essential pollinators. In many instances, a decline in the butterfly fauna is attributed to a decrease in nectar-rich and economically or culturally important wild plant species. Further, butterflies can be important in agricultural systems. For example, a survey of pollinators associated with macadamia in NE Brazil found that macadamia yields mainly benefited from pollination by butterflies rather than bees. Consequently, butterflies were responsible for > 50% of floral visits to macadamia flower. Moreover, their pollination of some vegetable crops contributes strongly to seed production.

Many flowers, including some orchids, are completely dependent on butterflies for pollination, and a member of the pea family, the peacock flower (Caesalpinia pulcherrima; Fig. 5) is largely dependent on butterflies for pollination, with pollen being mainly carried on their wings. In addition to butterflies, some moths have a special relationship with specific plants. For example, the yucca plant (Hesperoyucca whipplei) is pollinated by the yucca moth (Tegeticula maculata) with which it has a symbiotic relationship. The gravid female moth gathers pollen grains from flowers at night and forms them into a ball. She carries the ball in her mouth to another yucca flower. She then inserts her ovipositor into the ovary wall of the flower and deposits a single egg and then pushes the pollen into the stigma, thus pollinating the flower. The larva hatches in late spring or summer, and feeds on some of the developing seeds. Emergence of the adult moth occurs while yucca plants are again in bloom, allowing the cycle to continue.

Fig. 5. Orange sulphur butterfly feeding on peacock flower Caesalpinia pulcherrima – Photo: Anne Reeves (CC)

Flower structure and mouthparts

The body architecture (e.g., body size, mouth shape) and behavior of pollinators with respect to the flower’s dimension and morphology, are some of the factors that define which floral visitors are effective pollinators. Many studies of plant-pollinator interactions provide evidence that the morphological match between the flower shape and size, and the length of pollinators’ mouthparts influences pollination success. In relation to this, it has been observed that flowers and their pollinators engage in a series of reciprocal adaptive or coevolutionary cycles. In these cycles, plants that have the “best” floral shape for a specific pollinator are capable of producing more seeds, while pollinators that are capable of obtaining more nectar from an individual flower visit will also obtain greater energy required to produce more offsprings. When the pollinator and plant requirements align like this, plants tend to evolve floral shapes that match their “best” pollinator, while pollinators tend to evolve specific floral preferences and morphologies that match the plant. Over many generations, this leads to the establishment of floral preferences in pollinators, and a convergence in floral shapes of flowers visited by a given type of pollinator. It is for this reason that butterflies and hummingbirds are seen more often visiting long-necked or trumpet shaped flowers, than other pollinators; and these flower types are better pollinated by butterflies or hummingbirds than other pollinator groups. The result of these coevolutionary processes can be seen in many cases of pollination, but some of the most impressive examples are those having led to the evolution of extremely long proboscides (up to 14 inches) in some lepidopterans (Fig. 6), which match the length of the floral tube of their preferred flowers.

Fig. 6. Malagasy hawk moth visiting the ghost orchid. Photo: Minden Pictures / SuperStock.

How do moths and butterflies locate flowers

In order to locate floral resources, lepidopterans use a series of cues, such as specific colors, shapes, sizes and odors. As stated previously, moths are major nocturnal pollinators of a diverse range of plant species but have been historically considered to contribute little to overall pollination. However, recent research has rejected this notion, demonstrating that nocturnal moths contribute strongly to pollination, even to the point of compensating for poor pollination by diurnal pollinators. Moths are attracted to pale or white flowers with an open cup or tubular shape, heavy with fragrance and dilute nectar, and typically open in late afternoon to night. In turn, these plants are also specialized in pollination by moths, with these attractive traits having evolved through millions of years of coevolution. An example of these plants includes the creeping buttercup or honeysuckle, which tend to emit a strong fragrance at night.

Unlike moths, butterflies are diurnal and typically visit flowers under heavy sunlight, preferring those displayed in clusters and offering large nectar rewards (Fig. 7). Flowers specialized in pollination by butterflies are often brightly colored (red, yellow, orange), lack an apparent scent and secrete relatively dilute nectar in narrow elongated floral tubes. Examples of butterfly flowers are goldenrods and Asters, which provide a large landing surface as well as abundant and accessible nectar. Some of these preferences in butterflies are due to the butterfly’s good perception of color, which in most cases covers a wider range of the spectrum than human vision. Indeed, various studies have demonstrated that some pollinators rely strongly on color to make their foraging decisions, and this is certainly the case of butterflies. Similar to hummingbirds, butterflies have a good perception of the color red and as such, are attracted to red flowers. Further, many lepidopterans are able to distinguish various shades of yellow. To this point, an experiment consisting of potted daylily and nightlily showed that swallowtail butterflies preferentially visited reddish or orange-colored flowers and hawkmoths favored yellowish flowers. Similar to many insects, butterflies are capable of seeing ultraviolet light, which allows them to follow special nectar markings present on flowers that are only visible under that type of light. Correspondingly to how butterflies and moths are able to sense odors of their preferred flowers, studies have shown that butterflies may also sense the nectar amino acid content of different flowers, preferring those with high versus low amino acid content. For instance, studies found that, when given the choice, the cabbage white butterfly (Pieris rapae) preferred feeding on artificial flowers containing sugar-amino acid mixes, versus sugar-only nectar of Lantana camara (a perennial shrub).

Fig. 7. Fritillary butterfly feeding on goldenrod – Photo: hedera.baltica (CC)

Butterfly flower avoidance

As with all organisms, butterflies have their own natural enemies at the immature and adult stages. Egg, larva and pupa of butterflies and moths are vulnerable to parasitism and predation. Adult stages may suffer mortality from mammalian and arthropod predation. For instance, when visiting flowers, butterflies may be vulnerable to arthropod predators such as mantises and spiders (Fig. 8). Studies have shown that butterflies are capable of avoiding flowers with predator cues. For example, similar to bees, they have been shown to avoid flowers with artificial spiders and models of spider forelimbs. In another study conducted in a butterfly pavilion, visiting butterflies stayed away from flowers containing dead mantises.

Fig. 8. Crab spider feeding on a skipper butterfly – Photo: MattysFlicks (CC)

Howbeit, it is debatable whether butterflies were responding to the mantis’s cues or were simply avoiding flowers containing foreign objects. Still, some studies seem to agree that at least some avoidance is due to visual recognition. Interestingly, the degree of avoidance recorded in these studies indicated that it was weaker in butterflies reared in the pavilion than in wild butterflies. This tends to indicate that a part of this avoidance is learned and a reflection of previous predation experiences.

Butterfly conservation

Drivers of pollinator and butterfly losses. Many insect pollinators that provide vital services are declining and multiple factors have been implicated. In Europe, noticeable drops have been observed for butterflies, wild bees and hoverflies. Similarly, lepidopterists in the US are reporting that butterflies are in decline. Butterflies face a wide range of threats including habitat loss, changes in land management and land use, climate change, disease, pesticides and invasive organisms. Another driver of pollinator decline is agriculture intensification, which results in loss and fragmentation of pollinator-diverse habitats such as semi-natural grasslands, and is also associated with increased chemical use. Other factors associated with human activity have also been identified as contributors to pollinator loss. For instance, pollutants and urbanization can negatively affect the richness and abundance of native plant species used by pollinators, and thus lead to poor pollinator communities. Anthropogenic changes in the landscape can sometimes affect pollinators in surprising and indirect ways. For instance, changes in land use can lead to increased encroachment of plants such as some shrubs that are not congenial to butterflies and an associated decrease in butterfly richness and abundance by negatively impacting herbaceous plant cover and diversity. Further, enhanced shrub covering may indirectly affect pollinators by increasing their predation by perching birds.

Should bee and butterfly conservation plans be the same? The ecology of lepidopterans differs from that of bees. For example, bees require nectar and pollen throughout their life, while butterflies only utilize nectar as adults. Further, most caterpillars are leaf-feeders and do not require any parental care, while bees must collect pollen and nectar to support their brood and themselves. Moreover, while most bee species develop in relatively protected habitats (i.e., their nests), caterpillars are exposed while feeding on their host plants, vulnerable to predation, parasitism and climatic factors. These differences may require some alterations in conservation efforts aimed at protecting butterflies and bees. For example, butterfly-friendly environments must contain plants that support the larval and adult stages, and land management practices need to be appropriate for preserving plant species needed in caterpillar diets. Failing to do so would lead to low caterpillar survival or death, and the eventual loss of the butterfly population.

Conserving butterflies. To help save butterflies and other pollinators, it is recommended that a diversity of colorful, wildlife-friendly plants full of nectar be planted in gardens, yards, urban and recreational areas and on/nearby arable lands. Floral diversity is a pre-requisite for enhancing butterfly conservation, especially in urban environments. To better ensure butterflies have access to resources throughout the year, flowers with a range of bloom time (early spring through fall) and morphological features should be planted. Further, a habitat hospitable to butterflies and moths provides food for caterpillars, nectar-bearing flowers for adults, and consists of at least some native species. Indeed, although a few can feed on exotic plants, most caterpillar species are specialized on native plant species. Likewise, although some caterpillars are polyphagous, most are restricted to a few or just one plant species. Protecting land for butterflies does not equate to transforming all land into a fully protected area. Indeed, land in public settings, such as roadway medians, roadsides, landscaped parks, and even railway embankments have the potential to support large populations of pollinators. Confirming this, studies found that bee and butterfly species richness and abundance were higher in railway embankments than in grasslands. Further, they demonstrated that in that context non-vegetated ground negatively affected butterfly populations, since their diversity positively depended on species richness of native plants. For this same reason, open forests also tend to harbor higher pollinator diversity than forests with a very closed canopy. Further, actions can be taken to improve the pollinator friendliness of different public lands. For instance, roadside management plans can be designed to benefit pollinators (Fig. 9). Roadsides with abundant and diverse native wildflowers managed with judicious mowing and herbicide use can become diverse pollinator habitats. Furthermore, research indicates that roadsides with high-quality habitat reduce pollinator mortality as insects remain in the roadside as opposed to leaving in search of flowers.

Fig. 9. Roadside pollinator habitat – Photo: Minnesota Department of Transportation

Land management tactics for increasing plant diversity (intercropping, cover cropping, insectary plants, flower borders, etc.) are often used to enhance populations of natural enemies in cropping systems. When this practice is used to augment natural enemy efficacy, it is often called conservation biological control. However, this same tactic can be used to concomitantly conserve biocontrol agents and pollinators, while enhancing other services to cropping system (i.e., pest suppression). In a similar context, the idea of companion planting can also represent a way to combine production with pollinator protection in agricultural landscapes. Companion planting is a traditional husbandry practice whereby a second plant species is planted alongside a crop with the goal of improving yield. Using a flowering species as a companion plant can make arable lands more congenial to pollinators resulting in improved pollination services and crop yield. A recent study examined the use of borage, Borago officinalis (Fig. 10), as a companion plant in strawberry. Borage plants were found to significantly increase yield and quality of strawberries, suggesting an increase in insect pollination per plant.

Fig. 10. Butterfly visiting a borage plant. Photo: www.seedvilleusa.com

Summary

Immature stages of some moths and butterflies are viewed negatively because of their harm to agriculture. However, adult lepidopterans are mostly cherished for their aesthetic beauty, and less recognized for their contribution to pollination. Howbeit, lepidopterans are vital contributors to the pollination of wild plants and domesticated crops; and though their efficiency at crop pollination does not reach the level of bees in most systems, there are instances in which their services are of greater value (as for pollination of macadamia nuts), or compensating diurnal pollination (as shown for nocturnal moths). Moreover, while bees are more likely to pollinate fruit crops, butterflies are primary pollinators for many vegetables and herbs, especially those in the carrot, sunflower, legume, mint and Brassica family. Although pollination of these vegetable crops is not needed for producing the edible portion of the crop, it is required for seed production, in which future plantings require. This suggests that efforts being directed to protect bee pollinators should similarly integrate moth and butterfly conservation. To this point, because the ecology of bees and lepidopterans differ especially with respect to resource requirements during their immature stage, plans directed at conserving bee and lepidopteran pollinators should take these differences into consideration. Financial support for the publication of this article is via USDA NIFA EIPM grant award numbers 2017-70006-27171.

Protecting Pollinators in Ag Landscapes

Veronica Johnson, Maryland Department of Agriculture

A pollinator is any organism that transfers pollen –the male genetic material of plants- from one flower to the next, resulting in the production of fertile seeds. Pollinators include birds, bats, bees, butterflies, beetles and some small mammals. Bees are the most efficient of the pollinators, with some species capable of visiting up to 6 thousand flowers in a single day. This high rate of flower visitation is important considering between 75% and 95% of all flowering plants on Earth need help with pollination. These plants include the countless fruits, vegetables and nuts that constitute an important part of our diets. In fact, pollinators are responsible for one out of every three bites of food that we eat. Honey bees alone contribute between $1.2 and $5.4 billion in agricultural productivity in the U.S. Unfortunately, pollinator populations are changing. Many populations are in decline, primarily due to loss of feeding and nesting habitats. However, pollution, chemical misuse, disease and changing weather patterns are also contributing to shrinking pollinator populations. Continue reading Protecting Pollinators in Ag Landscapes