Evolutionary transition between bee pollination and hummingbird pollination in Salvia : Comparing means, variances and covariances of corolla traits

Variation in the Floral Morphology of Prosthechea karwinskii (Orchidaceae), a Mexican Endemic Orchid at Risk

Prosthechea karwinskii is an orchid endemic to Mexico, threatened by the destruction of its habitat and the extraction of specimens to meet its demand for ornamental and religious use. Most of its populations, including the most locally abundant ones, are found in Oaxaca state. Variations in some floral traits have been observed in these populations. We implemented a morphometric analysis to assess their floral variation and identify the most significant characters in the morphological patterns of this orchid. Floral samples were collected from 17 populations of P. karwinskii in Oaxaca, as well as from specimens used as ornaments during Easter in an Oaxacan community (Zaachila), whose origin is unknown. Sampling of natural populations covered the environmental, geographic, and morphological variation of the species. We performed an analysis of variance (ANOVA), principal component analysis (PCA), canonical variate analysis (CVA), and cluster analysis, including 185 individuals and 45 variables (12 of them were discarded in the multivariate analyses due to high correlation). Characters of the column, lateral sepal, and labellum were most informative for the observed morphological patterns. Albarradas showed the greatest morphological differentiation, mainly due to the column. In general, individuals from the same locality tended to overlap more, especially the populations of Jaltianguis and Yahuiche, which were different from the geographically close population of Etla. Teposcolula presented the highest values in perianth characters, unlike Sola_Rancho Viejo. The specimens recovered from religious ornaments were morphologically more similar to those from Yanhuitlan and Etla. This morphometric analysis identified characters as potential taxonomic markers for P. karwinskii and related species, showing its potential to associate specimens of unknown origin with their probable geographical region. Our work encourages working on collaborative conservation strategies to ensure the long-term permanence of both the species and its traditional uses.

Floral Diversity and Pollination Syndromes in Agave subgenus Manfreda

The genus Agave is an ecological keystone of American deserts and both culturally and economically important in Mexico. Agave is a large genus of about 250 species. The radiation of Agave is marked by an initial adaptation to desert environments and then a secondary diversification of species associated with pollinator groups, such as hummingbirds and nocturnal moths. Phylogenetic analyses place Agave subgenus Manfreda, or the "herbaceous agaves," in a monophyletic clade that likely evolved in part as an adaptation to novel pollination vectors. Here, we present a morphological and observational study assessing the evolution of floral form in response to pollinator specialization within this understudied group. We found significant visitation by hummingbirds and nocturnal moths to several species within the Agave subgenus Manfreda. These observations also align with our morphological analyses of floral organs and support the evolution of distinct pollination syndromes. We found that not all floral morphology is consistent within a pollination syndrome, suggesting hidden diversity in the evolution of floral phenotypes in Agave. We also characterize the morphological variation between herbarium and live specimens, demonstrating that special consideration needs to be made when combining these types of data. This work identifies the potential for studying the functional evolution of diverse floral forms within Agave and demonstrates the need to further explore ecological and evolutionary relationships to understand pollinator influence on diversification in the genus.

Local adaptation to hummingbirds and bees in Salvia stachydifolia: insights into pollinator shifts in a Southern Andean sage

BACKGROUND AND AIMS

Differences among populations in pollinator assemblages can lead to local adaptation mosaics in which plants evolve different floral morphologies and attractive traits. Mountain habitats may promote local adaptation because of differences in environmental conditions with altitude, causing changes in pollinators, and because mountaintops can act as isolated habitats. We studied if the differences in floral shape, size and nectar traits in Salvia stachydifolia can be attributed to variations in the relative contribution of hummingbirds and insects.

METHODS

We studied eight populations of S. stachydifolia in natural and under common garden conditions, to assess whether population differences have a genetic component. We recorded pollinators, their behaviour and visitation rates, and characterized pollinator assemblages. In addition, we measured nectar volume and concentration, and collected flowers to describe floral shape and size variation using geometric morphometric methods. We then applied an unsupervised learning algorithm to identify ecotypes based on morphometric traits. Finally, we explored whether populations with different pollinator assemblages had different climatic and/or elevation preferences.

KEY RESULTS

We found that variation in the identity of the main pollinators was associated with differences among populations in all traits, as expected under a local adaptation scenario. These differences persisted in the common garden, suggesting that they were not due to phenotypic plasticity. We found S. stachydifolia populations were pollinated either by bees, by hummingbirds or had mixed pollination. We identified two ecotypes that correspond to the identity of the main pollinator guilds, irrespective of climate or altitude.

CONCLUSIONS

Variation in S. stachydifolia floral traits did not follow any evident association with bioclimatic factors, suggesting that populations may have diverged as the product of historical isolation on mountaintops. We suggest that differences among populations point to incipient speciation and an ongoing pollinator shift.

Evolutionary convergence on hummingbird pollination in Neotropical Costus provides insight into the causes of pollinator shifts

The evolution of hummingbird pollination is common across angiosperms throughout the Americas, presenting an opportunity to examine convergence in both traits and environments to better understand how complex phenotypes arise. Here we examine independent shifts from bee to hummingbird pollination in the Neotropical spiral gingers (Costus) and address common explanations for the prevalence of transitions from bee to hummingbird pollination. We use floral traits of species with observed pollinators to predict pollinators of unobserved species and reconstruct ancestral pollination states on a well-resolved phylogeny. We examine whether independent transitions evolve towards the same phenotypic optimum and whether shifts to hummingbird pollination correlate with elevation or climate. Traits predicting hummingbird pollination include small flower size, brightly colored floral bracts and the absence of nectar guides. We find many shifts to hummingbird pollination and no reversals, a single shared phenotypic optimum across hummingbird flowers, and no association between pollination and elevation or climate. Evolutionary shifts to hummingbird pollination in Costus are highly convergent and directional, involve a surprising set of traits when compared with other plants with analogous transitions and refute the generality of several common explanations for the prevalence of transitions from bee to hummingbird pollination.

Artificial Light at Night Drives Earlier Singing in a Neotropical Bird

Simple Summary

Urban birds have to cope with dominant stressors as anthropogenic noise and artificial light at night by adjusting their song traits. However, evidence of such adjustments has been studied thus far in temperate cities, rather than tropical cities. Here, I tested whether noise and light pollution influence earlier singing behavior in a tropical bird, the Saffron Finch. Birds in highly urbanized sites sang earlier at dawn and this timing difference was driven by light pollution instead of anthropogenic noise. Overall, these results suggest that light pollution could have a detrimental impact on the circadian rhythms of urban tropical birds such as daily singing routines.

Abstract

Anthropogenic noise and artificial light at night (ALAN) can disrupt the morning singing routines of urban birds, however, its influence on tropical species remains poorly explored. Here, I assessed the association between light and noise pollution with the dawn chorus onset of the Saffron Finch (Sicalis flaveola) in a city in Colombia. I studied 32 sites comprised of different conditions of urban development based on built cover. I recorded the time of the first song of the Saffron Finch, the conspecific density and measured anthropogenic noise and ALAN using smartphone apps. The findings of this study show that Saffron Finches living in highly developed sites sang earlier at dawn than those occupying less urbanized sites. Unexpectedly, this timing difference was related to ALAN instead of anthropogenic noise, suggesting that light pollution could drive earlier dawn chorus in a tropical urban bird. Saffron Finches could take advantage of earlier singing for signaling territorial ownership among neighbors. Future studies need to assess the influence of ALAN on the dawn chorus timing of Neotropical urban birds.

Judge it by its shape: a pollinator-blind approach reveals convergence in petal shape and infers pollination modes in the genus Erythrina

PREMISE

Pollinators are thought to exert selective pressures on plants, mediating the evolution of convergent floral shape often recognized as pollination syndromes. However, little is known about the accuracy of using petal shape for inferring convergence in pollination mode without a priori pollination information. Here we studied the genus Erythrina L. as a test case to assess whether ornithophyllous pollination modes (hummingbirds, passerines, sunbirds, or mixed pollination) can be inferred based on the evolutionary analysis of petal shape.

METHODS

We characterized the two-dimensional dissected shape of standard, keel, and wing petals from 106 Erythrina species using geometric morphometrics and reconstructed a phylogenetic tree of 83 Erythrina species based on plastid trnL-F and nuclear ribosomal ITS sequences. We then used two phylogenetic comparative methods based on Ornstein-Uhlenbeck models, SURFACE and l1OU, to infer distinct morphological groups using petal shape and identify instances of convergent evolution. The effectiveness of these methods was evaluated by comparing the groups inferred to known pollinators.

RESULTS

We found significant petal shape differences between hummingbird- and passerine-pollinated Erythrina species. Our analyses also revealed that petal combinations generally provided better inferences of pollinator types than individual petals and that the method and optimization criterion can affect the results.

CONCLUSIONS

We show that model-based approaches using petal shape can detect convergent evolution of floral shape and relatively accurately infer pollination modes in Erythrina. The inference power of the keel petals argues for a deeper investigation of their role in the pollination biology of Erythrina and other bird-pollinated legumes.

The influence of floral traits on insect foraging behaviour on medicinal plants in an urban garden of eastern India

Understanding the pollination biology of medicinal plants and their important insect pollinators is necessary for their conservation. The present study explored the complex interactions between pollinator visitation and effect of floral traits on pollinator behaviour on seven medicinal plant species grown in an urban garden in West Bengal, an eastern Indian state. The observations revealed 30 morphospecies of insect flower visitors (Diptera, Lepidoptera and Hymenoptera) that touched floral reproductive parts on the selected plants during visitation. Additionally, it was observed that floral traits (e.g., corolla length and corolla opening diameter) were important predictors of the behaviour of insects when visiting the flowers. Plant–pollinator interactions were analysed using a bipartite network approach which explored the important links between insect and plants in the network revealing the key interactions, and species which are crucial to system maintenance. This piece of work contributes to our ability to understand and maintain a stable medicinal plant–pollinator network which will support efforts to conserve native flora and insects.

Pollination syndromes in the 21st century: where do we stand and where may we go?

Pollination syndromes, recurring suites of floral traits appearing in connection with specific functional pollinator groups, have served for decades to organise floral diversity under a functional-ecological perspective. Some potential caveats, such as over-simplification of complex plant-animal interactions or lack of empirical observations, have been identified and discussed in recent years. Which of these caveats do indeed cause problems, which have been solved and where do future possibilities lie? I address these questions in a review of the pollination-syndrome literature of 2010 to 2019. I show that the majority of studies was based on detailed empirical pollinator observations and could reliably predict pollinators based on a few floral traits such as colour, shape or reward. Some traits (i.e. colour) were less reliable in predicting pollinators than others (i.e. reward, corolla width), however. I stress that future studies should consider floral traits beyond those traditionally recorded to expand our understanding of mechanisms of floral evolution. I discuss statistical methods suitable for objectively analysing the interplay of system-specific evolutionary constraints, pollinator-mediated selection and adaptive trade-offs at microecological and macroecological scales. I exemplify my arguments on an empirical dataset of floral traits of a neotropical plant radiation in the family Melastomataceae.

Pollinator shifts, contingent evolution, and evolutionary constraint drive floral disparity in Salvia (Lamiaceae): Evidence from morphometrics and phylogenetic comparative methods

Switches in pollinators have been argued to be key drivers of floral evolution in angiosperms. However, few studies have tested the relationship between floral shape evolution and switches in pollination in large clades. In concert with a dated phylogeny, we present a morphometric analysis of corolla, anther connective, and style shape across 44% of nearly 1000 species of Salvia (Lamiaceae) and test four hypotheses of floral evolution. We demonstrate that floral morphospace of New World (NW) Salvia is largely distinct from that of Old World (OW) Salvia and that these differences are pollinator driven; shifts in floral morphology sometimes mirror shifts in pollinators; anther connectives (key constituents of the Salvia staminal lever) and styles co-evolved from curved to linear shapes following shifts from bee to bird pollination; and morphological differences between NW and OW bee flowers are partly the legacy of constraints imposed by an earlier shift to bird pollination in the NW. The distinctive staminal lever in Salvia is a morphologically diverse structure that has evolved in concert with both the corolla and style, under different pollinator pressures, and in contingent fashion.