Convergence, divergence, and homogenization in the ecological structure of emydid turtle communities: the effects of phylogeny and dispersal

Phylogenetic conservation in plant phenological traits varies between temperate and subtropical climates in China

Phenological traits, such as leaf and flowering dates, are proven to be phylogenetically conserved. The relationship between phylogenetic conservation, plant phenology, and climatic factors remains unknown. Here, we assessed phenological features among flowering plants as evidence for phylogenetic conservatism, the tendency for closely related species to share similar ecological and biological attributes. We use spring phenological traits data from 1968-2018 of 65 trees and 49 shrubs in Xi'an (temperate climate) and Guiyang (subtropical climate) to understand plant phenological traits' relationship with phylogeny. Molecular datasets are employed in evolutionary models to test the phylogenetic conservatism in spring phenological characteristics in response to climate-sensitive phenological features. Significant phylogenetic conservation was found in the Xi'an plant's phenological traits, while there was a non-significant conservation in the Guiyang plant species. Phylogenetic generalized least squares (PGLS) models correlate with phenological features significantly in Xi'an while non-significantly in Guiyang. Based on the findings of molecular dating, it was suggested that the Guiyang species split off from their relatives around 46.0 mya during the middle Eocene of the Tertiary Cenozoic Era, while Xi'an species showed a long evolutionary history and diverged from their relatives around 95 mya during the late Cretaceous Mesozoic Era. First leaf dates (FLD) indicative of spring phenology, show that Xi'an adjourned the case later than Guiyang. Unlike FLD, first flower dates (FFD) yield different results as Guiyang flowers appear later than Xi'an's. Our research revealed that various factors, including phylogeny, growth form, and functional features, influenced the diversity of flowering phenology within species in conjunction with local climate circumstances. These results are conducive to understanding evolutionary conservation mechanisms in plant phenology concerning evolutionary processes in different geographical and climate zones.

Macroevolutionary dynamics in the transition of angiosperms to aquatic environments

Angiosperm lineages in aquatic environments are characterized by high structural and functional diversity, and wide distributions. A long-standing evolutionary riddle is what processes have caused the relatively low diversity of aquatic angiosperms compared to their terrestrial relatives. We use diversification and ancestral reconstruction models with a comprehensive > 10 000 genus angiosperm phylogeny to elucidate the macroevolutionary dynamics associated with transitions of terrestrial plants to water. Our study reveals that net diversification rates are significantly lower in aquatic than in terrestrial angiosperms due to lower speciation and higher extinction. Shifts from land to water started early in angiosperm evolution, but most events were concentrated during the last c. 25 million years. Reversals to a terrestrial habitat started only 40 million years ago, but occurred at much higher rates. Within aquatic angiosperms, the estimated pattern is one of gradual accumulation of lineages, and relatively low and constant diversification rates throughout the Cenozoic. Low diversification rates, together with infrequent water transitions, account for the low diversity of aquatic angiosperms today. The stressful conditions and small global surface of the aquatic habitat available for angiosperms are hypothesized to explain this pattern.

Phylogenetic patterns of trait and trait plasticity evolution: Insights from tadpoles

Environmental heterogeneity has led to the widespread evolution of phenotypic plasticity in all taxonomic groups. Although phenotypic plasticity has been examined from multiple perspectives, few studies have examined evolutionary patterns of plasticity within a phylogeny. We conducted common-garden experiments on 20 species of tadpoles, spanning three families, exposed for 4 weeks to a control, predator cues, or reduced food (i.e., increased intraspecific competition). We quantified tadpole activity, growth, and relative morphology and found widespread differences in species responses to predator cues and reduced food. We detected pervasive phylogenetic signals in traits within each environment, but the phylogenetic signal was much less common in the trait plasticities. Among different models of continuous character evolution, Brownian Motion and Ornstein Uhlenbeck models provided better fits to the data than the Early Burst model. Tadpole activity level in predator environments had much higher evolutionary rates than in the control and reduced-food environments; we did not see this pattern in the other traits. In comparing traits versus trait plasticities, activity evolved much faster than the plasticity of activity whereas morphological traits evolved much slower than morphological plasticities. Collectively, these results suggest that traits and trait plasticities can exhibit dramatically different evolutionary patterns.

Anuran forelimb muscle tendinous structures and their relationship with locomotor modes and habitat use

The interaction between organisms and their environment is central in functional morphology. Differences in habitat usage may imply divergent morphology of locomotor systems; thus, detecting which morphological traits are conservative across lineages and which ones vary under environmental pressure is important in evolutionary studies. We studied internal and external morphology in 28 species of Neotropical anurans. Our aim was to determine if internal morphology (muscle and tendons) shows lower phylogenetic signal than external morphology. In addition, we wanted to know if morphology varies in relation to the habitat use and if there are different functional groups. We found differences in the degree of phylogenetic signal on the groups of traits. Interestingly, postaxial regions of the forelimb are evolutionarily more labile than the preaxial regions. Phylomorphospace plots show that arboreal (jumpers and graspers) and swimmer frogs cluster based on length of fingers and the lack of sesamoid, also reflected by the use of habitat. These functional clusters are also related to phylogeny. Sesamoid and flexor plate dimensions together with digit tendons showed to be important to discriminate functional groups as well as use of habitat classification. Our results allow us to identify a "grasping syndrome" in the hand of these frogs, where palmar sesamoid and flexor plate are absent and a third metacarpal with a bony knob are typical. Thus, a lighter skeleton, long fingers and a prensile hand may be key for arboreality.

Phylogenetic patterns of trait and trait plasticity evolution: Insights from amphibian embryos

Environmental variation favors the evolution of phenotypic plasticity. For many species, we understand the costs and benefits of different phenotypes, but we lack a broad understanding of how plastic traits evolve across large clades. Using identical experiments conducted across North America, we examined prey responses to predator cues. We quantified five life-history traits and the magnitude of their plasticity for 23 amphibian species/populations (spanning three families and five genera) when exposed to no cues, crushed-egg cues, and predatory crayfish cues. Embryonic responses varied considerably among species and phylogenetic signal was common among the traits, whereas phylogenetic signal was rare for trait plasticities. Among trait-evolution models, the Ornstein-Uhlenbeck (OU) model provided the best fit or was essentially tied with Brownian motion. Using the best fitting model, evolutionary rates for plasticities were higher than traits for three life-history traits and lower for two. These data suggest that the evolution of life-history traits in amphibian embryos is more constrained by a species' position in the phylogeny than is the evolution of life history plasticities. The fact that an OU model of trait evolution was often a good fit to patterns of trait variation may indicate adaptive optima for traits and their plasticities.

Evolutionary conservatism and convergence both lead to striking similarity in ecology, morphology and performance across continents in frogs

Many clades contain ecologically and phenotypically similar species across continents, yet the processes generating this similarity are largely unstudied, leaving fundamental questions unanswered. Is similarity in morphology and performance across assemblages caused by evolutionary convergence or by biogeographic dispersal of evolutionarily conserved ecotypes? Does convergence to new ecological conditions erase evidence of past adaptation? Here, we analyse ecology, morphology and performance in frog assemblages from three continents (Asia, Australia and South America), assessing the importance of dispersal and convergent evolution in explaining similarity across regions. We find three striking results. First, species using the same microhabitat type are highly similar in morphology and performance across both clades and continents. Second, some species on different continents owe their similarity to dispersal and evolutionary conservatism (rather than evolutionary convergence), even over vast temporal and spatial scales. Third, in one case, an ecologically specialized ancestor radiated into diverse ecotypes that have converged with those on other continents, largely erasing traces of past adaptation to their ancestral ecology. Overall, our study highlights the roles of both evolutionary conservatism and convergence in explaining similarity in species traits over large spatial and temporal scales and demonstrates a statistical framework for addressing these questions in other systems.

Phylogeny meets ecotoxicology: evolutionary patterns of sensitivity to a common insecticide

Pesticides commonly occur in aquatic systems and pose a substantial challenge to the conservation of many taxa. Ecotoxicology has traditionally met this challenge by focusing on short-term, single-species tests and conducting risk assessments based on the most sensitive species tested. Rarely have ecotoxicology data been examined from an evolutionary perspective, and to our knowledge, there has never been a phylogenetic analysis of sensitivity, despite the fact that doing so would provide insights into patterns of sensitivity among species and identify which clades are the most sensitive to a particular pesticide. We examined phylogenetic patterns of pesticide sensitivity in amphibians, a group of conservation concern owing to global population declines. Using the insecticide endosulfan, we combined previously published results across seven species of tadpoles and added eight additional species from the families Bufonidae, Hylidae, and Ranidae. We found significant phylogenetic signal in the sensitivity to the insecticide and in the existence of time lag effects on tadpole mortality. Bufonids were less sensitive than hylids, which were less sensitive than the ranids. Moreover, mortality time lags were common in ranids, occasional in hylids, and rare in bufonids. These results highlight the importance of an evolutionary perspective and offer important insights for conservation.

Phylogeny, life history, and ecology contribute to differences in amphibian susceptibility to ranaviruses

Research that identifies the potential host range of generalist pathogens as well as variation in host susceptibility is critical for understanding and predicting the dynamics of infectious diseases within ecological communities. Ranaviruses have been linked to amphibian die-off events worldwide with the greatest number of reported mortality events occurring in the United States. While reports of ranavirus-associated mortality events continue to accumulate, few data exist comparing the relative susceptibility of different species. Using a series of laboratory exposure experiments and comparative phylogenetics, we compared the susceptibilities of 19 amphibian species from two salamander families and five anurans families for two ranavirus isolates: frog virus 3 (FV3) and an FV3-like isolate from an American bullfrog culture facility. We discovered that ranaviruses were capable of infecting 17 of the 19 larval amphibian species tested with mortality ranging from 0 to 100%. Phylogenetic comparative methods demonstrated that species within the anuran family Ranidae were generally more susceptible to ranavirus infection compared to species from the other five families. We also found that susceptibility to infection was associated with species that breed in semi-permanent ponds, develop rapidly as larvae, and have limited range sizes. Collectively, these results suggest that phylogeny, life history characteristics, and habitat associations of amphibians have the potential to impact susceptibility to ranaviruses.

Emerging patterns in the comparative analysis of phylogenetic community structure

The analysis of the phylogenetic structure of communities can help reveal contemporary ecological interactions, as well as link community ecology with biogeography and the study of character evolution. The number of studies employing this broad approach has increased to the point where comparison of their results can now be used to highlight successes and deficiencies in the approach, and to detect emerging patterns in community organization. We review studies of the phylogenetic structure of communities of different major taxa and trophic levels, across different spatial and phylogenetic scales, and using different metrics and null models. Twenty-three of 39 studies (59%) find evidence for phylogenetic clustering in contemporary communities, but terrestrial and/or plant systems are heavily over-represented among published studies. Experimental investigations, although uncommon at present, hold promise for unravelling mechanisms underlying the phylogenetic community structure patterns observed in community surveys. We discuss the relationship between metrics of phylogenetic clustering and tree balance and explore the various emerging biases in taxonomy and pitfalls of scale. Finally, we look beyond one-dimensional metrics of phylogenetic structure towards multivariate descriptors that better capture the variety of ecological behaviours likely to be exhibited in communities of species with hundreds of millions of years of independent evolution.

Evolutionary history and the effect of biodiversity on plant productivity

Loss of biological diversity because of extinction is one of the most pronounced changes to the global environment. For several decades, researchers have tried to understand how changes in biodiversity might impact biomass production by examining how biomass correlates with a number of biodiversity metrics (especially the number of species and functional groups). This body of research has focused on species with the implicit assumption that they are independent entities. However, functional and ecological similarities are shaped by patterns of common ancestry, such that distantly related species might contribute more to production than close relatives, perhaps by increasing niche breadth. Here, we analyze 2 decades of experiments performed in grassland ecosystems throughout the world and examine whether the evolutionary relationships among the species comprising a community predict how biodiversity impacts plant biomass production. We show that the amount of phylogenetic diversity within communities explained significantly more variation in plant community biomass than other measures of diversity, such as the number of species or functional groups. Our results reveal how evolutionary history can provide critical information for understanding, predicting, and potentially ameliorating the effects of biodiversity loss and should serve as an impetus for new biodiversity experiments.

Testing the role of interspecific competition in the evolutionary origin of elevational zonation: an example with Buarremon brush-finches (Aves, Emberizidae) in the neotropical mountains

Interspecific competition might drive the evolution of ecological niches and result in pairs of formerly competing species segregating along ecological gradients following a process of character displacement. This mechanism has been proposed to account for replacement of related species along gradients of elevation in many areas of the world, but the fundamental issue of whether competition is responsible for the origin of elevational replacements has not been tested. To test hypotheses about the role of interspecific competition in the origin of complementary elevational ranges, I combined molecular phylogenetics, phylogeography, and population genetic analyses on Buarremon torquatus and B. brunneinucha (Aves, Emberizidae), whose patterns of elevational distribution suggest character displacement or ecological release. The hypothesis that elevational distributions in these species changed in opposite directions as a result of competition is untenable because: (1) a historical expansion of the range of B. brunneinucha into areas occupied by B. torquatus was not accompanied by a shift in the elevational range of the former species; (2) when B. brunneinucha colonized the range of B. torquatus, lineages of the latter distributions had already diverged; and (3) historical trends in effective population size do not suggest populations with elevational ranges abutting those of putative competitors have declined as would be expected if competition caused range contractions. However, owing to uncertainty in coalescent estimates of historical population sizes, the hypothesis that some populations of B. torquatus have declined cannot be confidently rejected, which suggests asymmetric character displacement might have occurred. I suggest that the main role of competition in elevational zonation may be to act as a sorting mechanism that allows the coexistence along mountain slopes only of ecologically similar species that differ in elevational distributions prior to attaining sympatry. The contrasting biogeographic histories of B. brunneinucha and B. torquatus illustrate how present-day ecological interactions can have recent origins, and highlights important challenges for testing the hypothesis of character displacement in the absence of data on population history and robust reconstructions of the evolution of traits and geographic ranges.

The Shapes of Phylogenetic Trees of Clades, Faunas, and Local Assemblages: Exploring Spatial Pattern in Differential Diversification

Life on Earth is characterized by strong diversity skewness: related lineages typically show pronounced variation in diversification success, and clades contain hyperdiverse and depauperate subclades. Previous studies have documented diversity skewness only for entire (global) clades. We demonstrate methods for measurement and significance testing of diversity skewness of local assemblages and regional biotas; we illustrate this with an analysis of geographic structure in diversity skewness of primate assemblages. For primates, continental faunas differ in diversity skewness from expectations based on the global phylogeny: South American faunas have significantly low skewness and African faunas have significantly high skewness. However, no local assemblage has diversity skewness different from that expected based on sampling the continental fauna. We also document a latitudinal gradient in diversity skewness for the African assemblages and test for (but do not find) associations of skewness with longitude, local species richness, and net primary productivity. Our data suggest that continental-scale biogeographic events rather than local-scale processes have shaped diversity skewness in modern primate faunas.