Based on recent molecular work by Paudyal & al., the generic limits of the Neotropical woody genus Exostema are reassessed with a view of making them more compatible with traditional, ...morphology‐based generic concepts. A wide circumscription is favoured, congruent with Paudyal & al.'s “clade B” (the Exostema‐Solenandra‐Coutarea‐Hintonia group). Thus defined, Exostema is a genus with 40 species and five natural sections and incorporates three generic splits that were proposed by Paudyal & al. To minimise nomenclatural disruption, a proposal to conserve the name Exostema Rich. against Coutarea Aubl. has been presented separately. Two new combinations at sectional rank are proposed.
Pathogen transmission mode is a key determinant of epidemiological outcomes. Theory shows that host density can influence the spread of pathogens differentially depending on their mode of ...transmission. Host density could therefore play an important role in determining the pathogen transmission mode. We tested theoretical expectations using floral arrays of the alpine carnation Dianthus pavonius in field experiments of spore dispersal of the anther‐smut fungus, Microbotryum, by vector (pollinator)‐based floral transmission and passive aerial transmission at a range of host densities. Pollinators deposited fewer spores per plant at high host density than at lower density (ranging from a 0.2–2 m spacing between plants), and vector‐based spore deposition at higher densities declined more steeply with distance from diseased plant sources. In contrast, while aerial spore deposition declined with distance from the diseased source, the steepness of this decline was independent of host density. Our study indicates that the amount and distance of vector‐based transmission are likely to be a nonmonotonic function of host density as a result of vector behavior, which is not readily encapsulated by fixed dispersal functions. We conclude that the spatial spread of pathogens by vectors is likely to be greater at lower and intermediate densities, whereas the spatial spread of aerially transmitted pathogens would be greater at high densities. These contrasting patterns could lead to differential importance of each transmission mode in terms of its contribution to subsequent infections across host densities.
Unrelated organisms that share similar niches often exhibit patterns of convergent evolution in functional traits. Based on bimodal distributions of hawkmoth tongue lengths and tubular white flowers ...in Africa, this study hypothesized that long-tongued hawkmoths comprise a pollination niche (ecological opportunity) that is distinct from that of shorter-tongued hawkmoths.
Field observations, light trapping, camera surveillance and pollen load analysis were used to identify pollinators of plant species with very long-tubed (>8 cm) flowers. The nectar properties and spectral reflectance of these flowers were also measured. The frequency distributions of proboscis length for all captured hawkmoths and floral tube length for a representative sample of night-blooming plant species were determined. The geographical distributions of both native and introduced plant species with very long floral tubes were mapped.
The convolvulus hawkmoth Agrius convolvuli is identified as the most important pollinator of African plants with very long-tubed flowers. Plants pollinated by this hawkmoth species tend to have a very long (approx. 10 cm) and narrow flower tube or spur, white flowers and large volumes of dilute nectar. It is estimated that >70 grassland and savanna plant species in Africa belong to the Agrius pollination guild. In South Africa, at least 23 native species have very long floral tubes, and pollination by A. convolvuli or, rarely, by the closely related hawkmoth Coelonia fulvinotata, has been confirmed for 11 of these species. The guild is strikingly absent from the species-rich Cape floral region and now includes at least four non-native invasive species with long-tubed flowers that are pre-adapted for pollination by A. convolvuli.
This study highlights the value of a niche perspective on pollination, which provides a framework for making predictions about the ecological importance of keystone pollinators, and for understanding patterns of convergent evolution and the role of floral traits in plant colonization.
Orchid conservation Fay, Michael F.; Pailler, Thierry; Dixon, Kingsley W.
Annals of botany,
09/2015, Letnik:
116, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Orchidaceae, one of the largest families of flowering plants, present particular challenges for conservation, due in great part to their often complex interactions with mycorrhizal fungi, pollinators ...and host trees. In this Highlight, we present seven papers focusing on orchids and their interactions and other factors relating to their conservation.
The Organization for Tropical Studies (OTS) has played a pivotal role in our understanding of tropical ecosystems' structure and function. For more than fifty years, OTS has contributed to the ...training of three generations of tropical biologists and facilitated, supported, and promoted leading-edge research in its field stations. Plant reproductive ecology and genetics have been a significant focus of OTS research since the early 1960s, and Dr. K.S. Bawa made a significant contribution to the advancement of this field. His work improved our understanding of the diversity and evolution of breeding systems in tropical forests, their phenology and pollination ecology, and their mating and genetic structure. We argue that his work inspired other tropical biologists' work and used the work of one of the authors for illustration when appropriate. We point out the need for research in critically important topics to slow down biodiversity loss, prevent the collapse of tropical systems in a changing climate, and the emergence of zoonotic disease. We suggest future research topics for the OTS field stations, including in plant reproductive biology.
Ecological systematic reviews and meta‐analyses have significantly increased our understanding of global biodiversity decline. However, for some ecological groups, incomplete and biased datasets have ...hindered our ability to construct robust, predictive models. One such group consists of the animal pollinators. Approximately 88% of wild plant species are thought to be pollinated by animals, with an estimated annual value of $230–410 billion dollars. Here we apply text‐analysis to quantify the taxonomic and geographical distribution of the animal pollinator literature, both temporally and spatially. We show that the publication of pollinator literature increased rapidly in the 1980s and 1990s. Taxonomically, we show that the distribution of pollinator literature is concentrated in the honey bees (Apis) and bumble bees (Bombus), and geographically in North America and Europe. At least 25% of pollination‐related s mention a species of honey bee and at least 20% a species of bumble bee, and approximately 46% of s are focussed on either North America (32%) or Europe (14%). Although these results indicate strong taxonomic and geographic biases in the pollinator literature, a large number of studies outside North America and Europe do exist. We then discuss how text‐analysis could be used to shorten the literature search for ecological systematic reviews and meta‐analyses, and to address more applied questions related to pollinator biodiversity, such as the identification of likely interacting plant–pollinator pairs and the number of pollinating species.
Premise
Understanding the factors that limit reproductive success is a key component of plant biology. Carnivorous plants rely on insects as both nutrient sources and pollinators, providing a unique ...system for studying the effects of both resource and pollen limitation on plant reproduction.
Methods
We conducted a field experiment using wild‐growing Dionaea muscipula J. Ellis (Droseraceae) in which we manipulated prey and pollen in a factorial design and measured flower production, number of fruits, and number of seeds. Because understanding reproduction requires knowledge of a plant species' reproductive and pollination biology, we also examined the pollination system, per‐visit pollinator effectiveness, and pollen‐ovule (P/O) ratio of D. muscipula.
Results
Plants that received supplemental prey produced more flowers than control plants. They also had a higher overall fitness estimate (number of flowers × fruit set (total fruits/total flowers) × seeds per fruit), although this benefit was significant only when prey supplementation occurred in the previous growing season. Neither pollen supplementation nor the interaction between pollen and prey supplementation significantly affected overall plant fitness.
Conclusions
This study reinforces the reliance of D. muscipula on adequate prey capture for flower, fruit, and seed production and a mobile pollen vector for reproduction, indicating the importance of considering insects as part of an effective conservation management plan for this species.
Understanding the relative contributions of wild and managed pollinators, and the functional contributions made by a diverse pollinator community, is essential to the maintenance of yields in the 75% ...of our crops that benefit from insect pollination. We describe a field study and pollinator exclusion experiments conducted on two soft-fruit crops in a system with both wild and managed pollinators. We test whether fruit quality and quantity is limited by pollination, and whether different pollinating insects respond differently to varying weather conditions. Both strawberries and raspberries produced fewer marketable fruits when insects were excluded, demonstrating dependence on insect pollinators. Raspberries had a short flowering season which coincided with peak abundance of bees, and attracted many bees per flower. In contrast, strawberries had a much longer flowering season and appeared to be much less attractive to pollinators, so that ensuring adequate pollination is likely to be more challenging. The proportion of high-quality strawberries was positively related to pollinator abundance, suggesting that yield was limited by inadequate pollination on some farms. The relative abundance of different pollinator taxa visiting strawberries changed markedly through the season, demonstrating seasonal complementarity. Insect visitors responded differently to changing weather conditions suggesting that diversity can reduce the risk of pollination service shortfalls. For example, flies visited the crop flowers in poor weather and at the end of the flowering season when other pollinators were scarce, and so may provide a unique functional contribution. Understanding how differences between pollinator groups can enhance pollination services to crops strengthens the case for multiple species management. We provide evidence for the link between increased diversity and function in real crop systems, highlighting the risks of replacing all pollinators with managed alternatives.
Altitudinal gradients are interesting models to test the effect of biotic and abiotic drivers of floral colour diversity, since an increase in UV irradiance, decrease of pollinator availability and ...shifts from bee- to fly-pollination in high relative to low altitudes are expected. We tested the effect of altitude and phylogeny, using several chromatic and achromatic colour properties, UV reflectance and pollinators’ discrimination capacity (Apis mellifera, Bombus terrestris, Musca domestica and Eristalis tenax), to understand the floral colour diversity in an alpine altitudinal gradient. All colour properties were weakly related to phylogeny. We found a shift from overdispersed floral colours and high chromatic contrast with the background (for bees) in the low altitude, to clustered floral colours (UV and green range for bees and flies) and clustered chromatic and achromatic properties in the high altitude. Different from flies, bees could discriminate floral colours in all altitudinal ranges. Low altitudes are likely to exhibit suitable conditions for more plant species, increasing competition for pollinators and floral colour divergence. Conversely, the increase in UV irradiance in high altitudes may filter plants with specific floral UV-reflectance patterns. Overall, floral colour diversity suggests that both biotic (pollinator fauna) and abiotic (UV irradiance) drivers shape floral communities, but their importance changes with altitude.
The Convolvulaceae is a large family containing species exhibiting a range of breeding systems and pollinated by diverse animal taxa. We studied the pollination ecology of 15 Convolvulaceae species, ...representing seven genera (Argyreia Lour., Camonea Raf., Evolvulus L., Hewittia Wight & Arn., Ipomoea L., Merremia Dennst. ex Endl., and Operculina Silva Manso), in northeastern Thailand, a family that is highly diverse yet understudied in the paleotropics. Specifically, we studied their compatibility systems and degrees of pollinator dependency using pollination experiments, examined pollinator composition and visitation rates using video observation, and determined if there is an association between pollinator visitation rates and degree of pollinator dependence. Our results showed that most species are self-compatible, but the degree of pollinator dependence varies. Six species were found to be highly dependent on pollinators, as two are self-incompatible and four are self-compatible but had reduced seed set when pollinators were excluded, possibly due to herkogamy. Seven species showed low dependence on pollinators and seed set remained high when pollinators were excluded. Pollinator dependence was inconclusive for two species as seed set was low in all pollination treatments. We also found an association between pollinator visitation rates and degree of pollinator dependence. Specifically, species exhibiting high pollinator dependence received frequent visits from pollinators, while species exhibiting low pollinator dependence either received frequent visits from pollinators (and received high amounts of xenogamous pollen) or infrequent visits from pollinators (and received significantly lower amounts of xenogamous pollen). Most of our study species were primarily visited by bees (e.g., Lasioglossum, Amegilla, Apis, and meliponines), with the exception of one night-blooming species that was visited primarily by crepuscular butterflies and hawkmoths. The cumulative findings of this study demonstrate how pollinator dependence is influenced by breeding system, and suggest that pollinator visitation is consistently high for species exhibiting high pollinator dependence but varies across species exhibiting low pollinator dependence. Our findings are also important for assessing the conservation risks of paleotropical Convolvulaceae.
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