Bat-pollinated Plants Research Articles

Floral morphology and pollen placement strategies of bat-pollinated flowers: a comparative analysis within a guild of chiropterophilous plants in a neotropical dry forest

BackgroundSynchronopatric plant species, coexisting and flowering simultaneously, often engage in intense competition for pollen deposition on shared pollinators. This study focuses on the intricate dynamics of chiropterophilous flowers within the neotropical bat-pollination plant guild, specifically investigating the mechanical fit of reproductive structures to pollinating bats at the community level.MethodsUtilizing a diverse guild of bat-pollinated plant species from the Caatinga, the largest dry forest in the Neotropics, our research integrates various key components. Initially, we identified specific contact sites for floral reproductive structures on the bat's body, exploring diverse pollen placement strategies. Subsequent efforts involved characterizing floral traits within the guild and examining their associations with different pollen placement strategies. Precision in the contact of floral reproductive structures was estimated, and findings were integrated by associating pollen placement strategies and precision with the investment in pollen production.ResultsWe found that certain bat body parts, particularly the face and neck, were more frequently contacted by reproductive structures. The three identified categories of pollen placement strategies were evenly distributed among plant species, each linked to specific floral traits. Notably, the absence of oriented herkogamy prevailed in 70% of the species. Morphometric analyses unveiled significant variations in operative distances among species, emphasizing exceptional variability in certain outliers. While precision in pollen transfer was influenced by key factors, surprisingly, investment in pollen production did not differ among plants with distinct pollen placement strategies. Furthermore, it showed no correlation with fundamental accuracy.ConclusionsThe subsequent exploration delves into the intricate associations between distinct floral characteristics and various pollen placement strategies, shaping the complex pollen landscape on bat bodies. This research provides valuable insights into the community-level dynamics of chiropterophilous flowers in the Caatinga Dry Forest, emphasizing the role of different pollen deposition strategies in facilitating the coexistence of multiple plant species within the chiropterophilous guild.

Bat or bee pollination? Floral biology of two sympatric Cayaponia species (Cucurbitaceae) in Southeast Brazil

The evolution of pollination systems is unclear for many plant taxa due to the scarcity of field observations on floral visitors. Supposed bat- and bee-pollination is reported for species of the genus Cayaponia, but <5 % of these were observed in the field and their pollinators recorded. We studied the pollination biology of two early diverging sister species of Cayaponia, C. cabocla and C. pilosa, recording the floral biology, phenology, breeding system, floral visitors, and floral scent chemistry. Both species are monoecious and have bell-shaped white to greenish flowers. The length of the C. cabocla flowers was 2.33 ± 0.52 cm and of the C. pilosa flowers it was 2.75±0.95 cm. In C. cabocla nectar volume of male flowers was 180±57.15 μl and sugar concentration was 28.75±0.95%, whereas in female flowers the average volume was 46.5 ± 10.24 μl and sugar concentration was 22.5 ± 0.57%. Cayaponia cabocla flowers opened at late night, around 03:30 h, whereas those of C. pilosa opened around noon. Both species bloom in the austral summer (January-February) and depend on bees to set fruit, in addition to having a few floral visitor species in common. Whereas some of the flower traits resemble those of bat-pollinated plants (most notably the large nectar volume and nocturnal anthesis), the floral volatiles of both C. cabocla and C. pilosa are typical of flowers pollinated by bees. This study clarifies the pollination system of two Cayaponia species and provides new information that can be used to reconstruct pollination system transitions in this rich genus of cucurbits.

Bat pollinators: a decade of monitoring reveals declining visitation rates for some species in Thailand

Bats are important pollinators, but they are difficult to study since they are volant and nocturnal. Thus, long-term studies of nectarivorous bats are scarce, despite their potential to help assess trends in bat populations and their pollination services. We used capture rates of nectarivorous bats at chiropterophilous flowers in order to examine temporal trends in bat visitation in an area that is undergoing extensive land use change. We mist-netted at five bat-pollinated plant taxa (Durio zibethinus, Musa acuminata, Oroxylum indicum, Parkia speciosa, and Sonneratia spp.) in southern Thailand over six years between 2011 and 2021. We found that the most common bat species, Eonycteris spelaea, was the main visitor at all five plant taxa and had consistent visitation rates across all study years. In contrast, two other important pollinators, Macroglossus minimus and M. sobrinus, showed 80% declines in the number of individuals netted at mangrove apple (Sonneratia spp.) and banana (Musa acuminata) flowers, respectively. These findings suggest that E. spelaea (a large, cave-roosting species with a broad diet) is more tolerant of anthropogenic change than are Macroglossus bats (small, foliage-roosting species with specialized diets), which may in turn affect the reproductive success of plants pollinated by these species. Our study demonstrates how decade-long monitoring can reveal species-specific temporal patterns in pollinator visitation, emphasizing the need for tailored conservation plans. While the conservation status of most nectarivorous bats in the area is Least Concern, our results indicate that population studies in Southeast Asia are urgently needed for updated bat species conservation assessments.

An ultrasound absorbing inflorescence zone enhances echo-acoustic contrast of bat-pollinated cactus flowers.

Flowering plants have evolved an extraordinary variety of signaling traits to attract their pollinators. Most flowers rely on visual and chemical signals, but some bat-pollinated plants have evolved passive acoustic floral signals. All known acoustic flower signals rely on the same principle of increased sonar reflectivity. Here we describe a novel mechanism that relies on increased absorption of the area surrounding the flower. In a bat-pollinated cactus (Espostoa frutescens) we found a hairy inflorescence zone, a so called cephalium. Flowers solely emerge out of this zone. We measured the echoes of cephalia, flowers and unspecialized column surfaces and recorded echolocation calls of approaching bats. We found that the cephalium acts as strong ultrasound absorber, attenuating the sound by -14 dB. The absorption was highest around the echolocation call frequencies of approaching bats. Our results indicate that, instead of making flowers more reflective, plants can also evolve structures to attenuate the background echo, thereby enhancing the acoustic contrast with the target.

Acoustic traits of bat-pollinated flowers compared to flowers of other pollination syndromes and their echo-based classification using convolutional neural networks.

Bat-pollinated flowers have to attract their pollinators in absence of light and therefore some species developed specialized echoic floral parts. These parts are usually concave shaped and act like acoustic retroreflectors making the flowers acoustically conspicuous to the bats. Acoustic plant specializations only have been described for two bat-pollinated species in the Neotropics and one other bat-dependent plant in South East Asia. However, it remains unclear whether other bat-pollinated plant species also show acoustic adaptations. Moreover, acoustic traits have never been compared between bat-pollinated flowers and flowers belonging to other pollination syndromes. To investigate acoustic traits of bat-pollinated flowers we recorded a dataset of 32320 flower echoes, collected from 168 individual flowers belonging to 12 different species. 6 of these species were pollinated by bats and 6 species were pollinated by insects or hummingbirds. We analyzed the spectral target strength of the flowers and trained a convolutional neural network (CNN) on the spectrograms of the flower echoes. We found that bat-pollinated flowers have a significantly higher echo target strength, independent of their size, and differ in their morphology, specifically in the lower variance of their morphological features. We found that a good classification accuracy by our CNN (up to 84%) can be achieved with only one echo/spectrogram to classify the 12 different plant species, both bat-pollinated and otherwise, with bat-pollinated flowers being easier to classify. The higher classification performance of bat-pollinated flowers can be explained by the lower variance of their morphology.

A nectar oasis for urban Glossophaginae bats: Temporal resource dynamics of the chiropterophilous Crescentia cujete (Bignoniaceae)

Pollinator-friendly plants are often a necessary component of the management of urban ecosystem that aim to reduce the impact of the artificial urban matrix on natural pollinator populations. Nectarivorous bats are neglected components of the urban pollinator community and there is a paucity of assessments on pollinator-friendly plants that may provide urban bats with reliable, year-long resources. Crescentia cujete is a bat-pollinated Bignoniaceae with very distinctive chiropterophilous features that is often used as an ornamental species in tropical urban areas worldwide. Its flowers are large and produce copious amounts of nectar, which accumulates in the flower’s storage-shaped flowers. Thus, the species is a potential bat-friendly urban plant. We assessed the species’ year-round flower emission and nightly nectar production dynamics in a green area in northeastern Brazil, and described the behavior of its floral visitors. C. cujete showed a steady, year-round flowering pattern, with no significant seasonality. Its flowers secreted copious amounts of diluted nectar and were visited exclusively by the Pallas long-tongued bat Glossophaga soricina throughout the night at high visiting frequencies, delivering successive visits to individual flowers spaced by short intervals. Our results suggest overexploitation of floral resources from C. cujete by urban bats. Moreover, its continuous flowering and copious nectar production may become a reliable resource in an artificial environment generally lacking bat-pollinated plants, thus mitigating the effects of food shortage for urban nectar bats.

Free amino acids in nectar: its composition and variability among bat-pollinated plants

Regardless of the low concentrations at which amino acids are present in floral nectar of bat-pollinated plants, their role as nectar flavor providers and their influence on bats’ foraging decisions have been recognized. Nevertheless, variation in the free amino acids among bat-pollinated plant species has been less studied. The goal of this study was to analyze the nectar free amino acids and to determine its variability among 8 bat-pollinated plant species from 5 families in a Tropical Dry Forest in Mexico. Nectar collections were made opportunistically depending on plants flowering season. We quantified 17 amino acids by HPLC. All 17 free amino acids were present in nectar from the 8 analyzed plant species. The concentration of 12 amino acids is explained by plant species by 19-58%. Analyses showed that Ceiba grandiflora (Malvaceae) was significantly different in asparagine content when compared to Bahuinia pauletia (Fabaceae) and Ceiba aesculifolia (Malvaceae), and in glutamic acid when compared to Ipomoea ampullacea (Convolvulaceae). We discuss the importance of free amino acids in nectar among plant species and their influence on bat pollination ecology.

Bioinspired sonar reflectors as guiding beacons for autonomous navigation

Sonar sensors are universally applied in autonomous vehicles such as robots and driverless cars as they are inexpensive, energy-efficient, and provide accurate range measurements; however, they have some limitations. Their measurements can lead to ambiguous estimates and echo clutter can hamper target detection. In nature, echolocating bats experience similar problems when searching for food, especially if their food source is close to vegetation, as is the case for gleaning bats and nectar-feeding bats. However, nature has come up with solutions to overcome clutter problems and acoustically guide bats. Several bat-pollinated plants have evolved specially shaped floral parts that act as sonar reflectors, making the plants acoustically conspicuous. Here we show that artificial sonar beacons inspired by floral shapes streamline the navigation efficacy of sonar-guided robot systems. We developed floral-inspired reflector forms and demonstrate their functionality in 2 proof-of-principle experiments. First we show that the reflectors are easily recognized among dense clutter, and second we show that it is possible to discern different reflector shapes and use this identification to guide a robot through an unfamiliar environment. Bioinspired sonar reflectors could have a wide range of applications that could significantly advance sonar-guided systems.

Discrimination of small sugar concentration differences helps the nectar-feeding bat Leptonycteris yerbabuenae cover energetic demands.

Every day nectar-feeding animals face an energetic challenge during foraging: they must locate and select flowers that provide nectar with adequate amounts of sugar to cover their very high energy needs. To understand this decision-making process, it is crucial to know how accurately sugar concentration differences can be discriminated. In a controlled laboratory setting, we offered the nectar-specialist bat Leptonycteris yerbabuenae the choice between different sugar solutions covering the entire concentration range of bat-pollinated plants (3-33%). When feeding on solutions below 10% sugar concentration, L. yerbabuenae were unable to cover their energetic demands because of physiological constraints. Their ability to discriminate sugar concentrations was better than that of any other nectar-feeding animal studied to date. At sugar concentrations below 15%, L. yerbabuenae can discriminate solutions differing by only 0.5%. The bats may utilize this fine-tuned ability to select nectar from flowers with reward qualities that provide them with the necessary amount of energy to survive.

Flowers up! The effect of floral height along the shoot axis on the fitness of bat-pollinated species.

Bat-pollination is an important system in terms of occurrence and distribution, although it remains little studied. Thus, the role of particular flower traits in this interaction remains uncertain. Flower height along the shoot axis, associated with flower exposure, has often been deemed a key trait in this system, but its effect on fitness has not previously been assessed. We aimed to test its role and propose that taller flowers attain higher fitness due to a higher degree of accessibility and conspicuity to foraging bats. We assessed the effect of floral height on bat visiting rates to individual flowers of Crescentia cujete (Bignoniaceae), a cauliflorous model bat-pollinated species with a marked gradient in flower height along the shoot axis. Additionally, we tested the effect of this variable on seed/ovule ratio measurements from seven other species from different families along a herb-tree gradient. Hypotheses were tested through mixed-effect linear models. Bat visiting rates varied positively as a function of flower height in C. cujete, but significance was found only for the subset of flowers located on the trunk, closer to the ground. Similarly, seed/ovule ratios were positively correlated with flower height only for the three species with the shortest statures along the height gradient and shortest average floral heights. These results suggest that proximity to the ground, associated with herbaceous or bushy surrounding vegetation, may be an obstacle to the foraging of nectar-feeding bats, which in turn should explain the morphological convergence of inflorescence length and exposure strategies of short-statured bat-pollinated plants. Flower height has a species-specific effect on plant fitness. This study provides a novel numerical perspective to the role of an unexplored trait in bat-pollination, and has elucidated some aspects of the adaptive importance of flower height based on limitations imposed by ecologically complex pollinators.

What Do Nectarivorous Bats Like? Nectar Composition in Bromeliaceae With Special Emphasis on Bat-Pollinated Species.

Floral nectar is the most important reward for pollinators and an integral component of the pollination syndrome. Nectar research has mainly focused on sugars or amino acids, whereas more comprehensive studies on the nectar composition of closely related plant species with different pollination types are rather limited. Nectar composition as well as concentrations of sugars, amino acids, inorganic ions, and organic acids were analyzed for 147 species of Bromeliaceae. This plant family shows a high diversity in terms of floral morphology, flowering time, and predominant pollination types (trochilophilous, trochilophilous/entomophilous, psychophilous, sphingophilous, chiropterophilous). Based on the analyses, we examined the relationship between nectar traits and pollination type in this family. Nectar of all analyzed species contained high amounts of sugars with different proportions of glucose, fructose, and sucrose. The total concentrations of amino acids, inorganic cations, and anions, or organic acids were much lower. The analyses revealed that the sugar composition, the concentrations of inorganic cations and anions as well as the concentration of malate in nectar of bat-pollinated species differed significantly from nectar of species with other pollination types. Flowers of bat-pollinated species contained a higher volume of nectar, which results in a total of about 25-fold higher amounts of sugar in bat-pollinated species than in insect-pollinated species. This difference was even higher for amino acids, inorganic anions and cations, and organic acids (between 50 and 100-fold). In general, bat-pollinated plant species invest large amounts of organic and inorganic compounds for their pollinators. Furthermore, statistical analyses reveal that the characteristics of nectar in Bromeliaceae are more strongly determined by the pollinator type rather than by taxonomic groups or phylogenetic relations. However, a considerable part of the variance cannot be explained by either of the variables, which means that additional factors must be responsible for the differences in the nectar composition.

Comment on "Cognition-mediated evolution of low-quality floral nectars".

Nachev et al (Reports, 6 January 2017, p. 75) present dilute nectar in bat-pollinated plants as "paradoxical" because bats prefer concentrated nectar, but paradox disappears with realistic assumptions about nectar evolution. We argue that they make unrealistic assumptions about the cognitive abilities of bat pollinators, invoke Weber's law inappropriately, and cannot predict observed nectar concentrations of bat flowers or negative correlations between pollinator body size and average concentration.

Field evidence of strong differential pollen placement by Old World bat-pollinated plants.

Sympatric plant species that share pollinators potentially compete for pollination and risk interspecific pollen transfer, but this competition can be minimized when plant species place pollen on different areas of the pollinator's body. Multiple studies have demonstrated strong differential pollen placement by sympatric plant species under laboratory conditions; however, field evidence collected in natural settings is less common. Furthermore, it is unknown whether precise pollen placement on the pollinator's body remains constant throughout the foraging period, or if such patterns become diffused over time (e.g. due to grooming). To test the prevalence of differential pollen placement in the wild, we examined a community of five night-blooming plant species in southern Thailand that share common bat pollinators. We mist-netted wild foraging nectar bats and collected pollen samples from four body parts: the crown of the head, face, chest and ventral side of one wing. We also noted the time of pollen collection to assess how pollinator pollen loads change throughout the foraging period. Our findings revealed that most of our plant study species placed pollen on precise areas of the bat, consistent with experimental work, and that patterns of differential pollen placement remained constant throughout the night. This study demonstrates how diverse floral morphologies effectively limit interspecific pollen transfer among Old World bat-pollinated plants under natural conditions. Additionally, interspecific pollen transfer is probably minimal throughout the entire foraging period, since patterns of pollen on the bats' bodies were consistent over time.

Differential pollen placement on an Old World nectar bat increases pollination efficiency.

Plant species that share pollinators are potentially subject to non-adaptive interspecific pollen transfer, resulting in reduced reproductive success. Mechanisms that increase pollination efficiency between conspecific individuals are therefore highly beneficial. Many nocturnally flowering plant species in Thailand are pollinated by the nectar bat Eonycteris spelaea (Pteropodidae). This study tested the hypothesis that plant species within a community reduce interspecific pollen movement by placing pollen on different areas of the bat's body. Using flight cage trials, pollen transfer by E. spelaea was compared between conspecific versus heterospecific flowers across four bat-pollinated plant genera. Pollen from four locations on the bat's body was also quantified to determine if pollen placement varies by plant species. It was found that E. spelaea transfers significantly more pollen between conspecific than heterospecific flowers, and that diverse floral designs produce significantly different patterns of pollen deposition on E. spelaea. In the Old World tropics, differential pollen placement is a mechanism that reduces competition among bat-pollinated plant species sharing a common pollinator.

The floral bat lure dimethyl disulphide does not attract the palaeotropical Dawn bat

In the neotropics, dimethyl disulphide (DMDS) is innately attractive to flower-visiting bats, and acts as a powerful bat lure in the scent bouquets of many bat-pollinated flowers. At first, DMDS appeared to be part of a general bat pollination syndrome. However, DMDS is absent in many bat-pollinated flowers of West Africa, and it is unclear whether palaeotropical flower-visiting bats are also attracted to it. Furthermore, DMDS was previously observed in neotropical, but not palaeotropical, populations of Ceiba pentandra (Malvaceae, Bombacoideae). We tested for an attraction to DMDS in the most common flower-visiting bat in Thailand, the dawn bat Eonycteris spelaea. We gave bats choices of Ceiba pentandra flowers, where one random flower was scented with DMDS. Rather than preferring the DMDS-treated flower, 21 of 22 bats chose an untreated flower, showing no attraction to DMDS. Alongside past evidence, this result suggests that the role of DMDS in bat pollination syndromes may result from an adaptive convergence that is limited to the neotropics. This hypothesis could be tested through comparative studies of (1) attraction across bats, (2) floral DMDS presence across bat-pollinated plants in Asia, and (3) floral DMDS measures across New and Old World populations of Ceiba pentandra.

Differences in foraging times between two feeding guilds within Old World fruit bats (Pteropodidae) in southern Thailand

Abstract:Bats are important but understudied pollinators in the Palaeotropics, and much about their interactions with night-blooming, bat-pollinated plant species is still unknown. We compared visitation times to flowering and fruiting plant resources by nectarivorous bat species (obligate pollinators) and frugi-nectarivorous bat species (facultative pollinators) throughout the night to examine the temporal variability that occurs within Pteropodidae foraging. Timing of pollination is an important determinant of plant reproductive success and more temporally restrictive than fruit dispersal. We netted 179 nectarivorous bats and 209 frugi-nectarivorous bats across 367 total mist-net h at five plant species providing floral resources and six plant species providing fruit resources. We found that all three nectarivorous bat species in southern Thailand forage significantly earlier in the evening (20h30 versus 22h00), and over a significantly shorter time interval (1.73 h versus 3.33 h), than do the five most commonly netted frugi-nectarivorous species. These results indicate that the two feeding guilds may be imposing different selective pressures on bat-pollinated plant species and may comprise different functional groups. We propose that the observed differences in bat foraging times are due to temporal constraints imposed by the rewards of the plant species that they visit.

Plant–animal communication

There are numerous excellent books about plant–pollinator and plant–herbivore interactions, and books about plant defence, but none of these covers the process of communication between plants and animals as comprehensively as this volume. The authors define communication as occuring ‘if traits of the sender stimulate the sensory systems of the receiver in such a way as to cause a change in the behaviour of the receiver’. In most cases the signal – visual, olfactory, gustatory or acoustic – is released by the plant. The focus in this book is on olfactory and visual signals. In addition, the authors give examples of how insects can detect plant quality just by walking on it and sensing the taste with gustatory sensors in their legs. Acoustic communication is exemplified by the noise of fruit falling into water, where fruit-feeding fish are alerted to this food source, eat the fruit and subsequently disperse seeds. Acoustic communication is also linked to bat-pollinated plants, which have mirror-like structures in their flowers to strongly reflect bat echolocation calls back to the sender. The authors have taken an evolutionary ecological approach, setting the key questions of whether communication between plants and animals is primarily adaptive or whether it is a by-product of other selective pressures. The book has eleven chapters, including ones on animal sensory ecology and biochemistry, animals as seed dispersers, visual and non-visual fruit traits, floral communication and pollination, plant crypsis, aposematism and mimicry, chemical communication between plants and herbivores, and sensory aspects of carnivorous plants. Chapter 7 is devoted to the potential for leaf colouration to communicate to animals. When the evolutionary biologist W. D. Hamilton and colleagues presented the co-evolutionary theory to explain the autumn colouration of temperate tree foliage, it stimulated research on leaf colouration and provoked a rather heated debate between supporters and critics. Theory suggests that intensity of colouration is a signal revealing the defensive commitment of the individual plant, and autumn-migrating insects use this signal to select less-defended plants. Of the book's authors, Schaefer has shown a critical attitude towards the autumn leaf co-evolution hypothesis in his earlier publications, but the review and analysis of the issue in this book is very balanced. The authors suggest more choice trials to test the hypothesis and to assess different selective pressures that might contribute to the relationship between leaf colouration and insect choice. The four-page colour plates in the book give good examples of visual communication. The illustration of functional camouflage, showing how differently coloured, folivorous insects can take advantage of the variable colours of leaf venation when positioned on leaves, is particularly educational. The redrawn black and white figures are clear and informative throughout the book. The book covers most of the aspects related to biological communication between plants and animals, particularly in terrestrial ecosystems. As the ecosystems of our planet are facing extremely rapid changes due to human activity, the impacts of environmental disturbance on plant–animal communication ought to have deserved its own chapter, or better treatment in the future perspectives section of each chapter. Changes in plant–animal interactions are considered one of the most sensitive indicators of environmental and climatic change, and the change is often attributed to a dramatic decline in communication. A good example is the function of plant scents as long-distance communication signals in ecological communities, with essential roles in a range of interactions. These molecules display sensitivity to present-day atmospheric pollutants resulting in much faster degradation of molecular structure and shorter communication ranges than in pre-industrial atmospheres (e.g. McFrederick et al., 2009). When this loss of communication by long-distance olfactory signals is combined with the current trend for faster fragmentation of the natural habitats of many plant and animal species, we may better understand ecologically important trends such as the swift decline of pollinators across the world. Perhaps the next edition of this book could discuss if evolution of plant–animal communication is fast enough to respond to this anthropogenic challenge. Otherwise, the authors have put together an excellent book on communication, ranging from sensory ecology to plant physiology, evolution and the behavioural sciences. For researchers it will give a critical synthesis of the current literature in the diverse field of biological communication research. For students it will be an excellent source of information for advanced courses related to botany, zoology, pollination biology, evolution and ecology.

Analysis of acoustic echoes from a bat-pollinated plant species: insight into strategies for radar and sonar target classification

Automatic target classification under all conditions is a key challenge for modern radar and sonar systems. Echolocating nectar feeding bats are able to detect and select flowers of bat-pollinated plants even in highly cluttered environments. It is thought that these flowers have evolved to ease classification by bats, and that their echo-acoustic signatures contain critical information that aids the bat in choosing the most suitable flowers. In investigating the features of these flowers that aid the bats search for nectar, the strategy underpinning the task of classification of static targets by bats may be understood and this may additionally offer lessons for radar and sonar systems. Here, we analyse a real set of data containing high range resolution profiles of unpollinated corollas of Cobaea scandens, which is a flower of the type that is pollinated by bats. These were collected by transmitting a synthetic wideband linear chirp with an acoustic radar capable of very high range resolution. Classification performance of a k-NN classifier and a Naïve Bayesian classifier is assessed using information available in both the time and frequency domains. This facilitates quantification of the differences in these echoes because of the flower wilting process and lack of physical parts.

Flower classification by bats: Radar comparisons

In recent years, with the development of high-range resolution radars, the desire to identify targets under all weather and clutter conditions has become of great importance. This is an activity carried out with great success by echo-locating mammals such as nectar feeding bats that are able to detect and select flowers of bat-pollinated plants, even in a dense clutter environment. Herein, data consisting of acoustically-generated high-range resolution profiles of four bat-pollinated flower heads are analysed. Multi-perspective classification performance is assessed and compared with the radar case. There are close parallels that suggest lessons can be learnt from nature.

Reproductive biology of Datura wrightii: the benefits of a herbivorous pollinator

A deeper understanding of mutualism can be reached by studying systems with measurable costs and benefits. Most studies of this type focus on an unusual class of obligate, species-specific pollination mutualisms. The interaction between Datura wrightii (Solanaceae) and the hawkmoth Manduca sexta offers similar advantages but greater generality. Adult moths both nectar at and deposit eggs on the same plant; larvae are herbivorous. The antagonistic component of this interaction has been well studied. Here the role of M. sexta as a pollinator of D. wrightii, particularly in the context of this moth's frequent nectaring visits to the bat-pollinated plant Agave palmeri, is documented. Hand-pollinations were used to determine breeding system and the reproductive consequences of mixed loads of A. palmeri and D. wrightii pollen. Plants and moths were caged overnight to assess whether nectaring visits led to fruit and seed set. Finally, pollen deposited on field-collected stigmas was identified, with a particular focus on documenting the presence of D. wrightii and A. palmeri grains. Datura wrightii is highly self-compatible, and a visit that deposits either outcross or self pollen almost doubles fruit and seed set compared with unvisited flowers. Manduca sexta transferred enough pollen to produce fruit and seed sets comparable to hand-pollination treatments. Agave palmeri did not interfere with D. wrightii success: in the field, stigmas received almost pure D. wrightii pollen, and hand-addition of large quantities of A. palmeri pollen had no measurable effect on fruit and seed set. The floral visitation component of the D. wrightii-M. sexta interaction is indeed mutualistic. This finding is essential background to future development of this interaction as a model system for studying mutualism's costs and benefits. It is already proving valuable for dissecting third-species effects on the outcome of mutualism. Results indicate that M. sexta's heavy visitation to A. palmeri has no negative effect on the benefits conferred to D. wrightii. However, it can be predicted to augment M. sexta populations to the point where the costs of the interaction begin to exceed its benefits.