Abstract
BackgroundMajor factors influencing the phenotypic diversity of a lineage can be recognized by characterizing the extent and mode of trait evolution between related species. Here, we compared the evolutionary dynamics of traits associated with floral morphology and climatic preferences in a clade composed of the genera Codonanthopsis, Codonanthe and Nematanthus (Gesneriaceae). To test the mode and specific components that lead to phenotypic diversity in this group, we performed a Bayesian phylogenetic analysis of combined nuclear and plastid DNA sequences and modeled the evolution of quantitative traits related to flower shape and size and to climatic preferences. We propose an alternative approach to display graphically the complex dynamics of trait evolution along a phylogenetic tree using a wide range of evolutionary scenarios.ResultsOur results demonstrated heterogeneous trait evolution. Floral shapes displaced into separate regimes selected by the different pollinator types (hummingbirds versus insects), while floral size underwent a clade-specific evolution. Rates of evolution were higher for the clade that is hummingbird pollinated and experienced flower resupination, compared with species pollinated by bees, suggesting a relevant role of plant-pollinator interactions in lowland rainforest. The evolution of temperature preferences is best explained by a model with distinct selective regimes between the Brazilian Atlantic Forest and the other biomes, whereas differentiation along the precipitation axis was characterized by higher rates, compared with temperature, and no regime or clade-specific patterns.ConclusionsOur study shows different selective regimes and clade-specific patterns in the evolution of morphological and climatic components during the diversification of Neotropical species. Our new graphical visualization tool allows the representation of trait trajectories under parameter-rich models, thus contributing to a better understanding of complex evolutionary dynamics.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0527-6) contains supplementary material, which is available to authorized users.
Highlights
Major factors influencing the phenotypic diversity of a lineage can be recognized by characterizing the extent and mode of trait evolution between related species
We investigate the evolutionary history of floral morphology and climatic preferences in a clade of epiphytic plants belonging to the genera Codonanthopsis, Codonanthe, and Nematanthus of the Gesneriaceae family
Models of continuous trait evolution We examined the patterns of trait evolution by using the maximum clade credibility (MCC) tree and multiple models, which span from a single Brownian motion rate of evolution (BM with single σ2), BM with variable rate through time including early burst (EB) to OrnsteinUhlenbeck models
Summary
Major factors influencing the phenotypic diversity of a lineage can be recognized by characterizing the extent and mode of trait evolution between related species. Initially rapid morphological evolution followed by relative stasis [5] could be the result of new ecological opportunities accompanied by density-dependent slowdowns in species diversification [6, 7] To explore this process, trait evolution can be reconstructed along the branches of phylogenetic trees to detect heterogeneity in evolutionary rates through time, across lineages or in relation to discrete characters [8,9,10]. Ornstein-Uhlenbeck (OU) models can be used to describe bounded phenotypic evolution, where single or multiple selective regimes pull phenotypes towards optimum values [11] In plants, these models have helped to understand the evolutionary dynamics of flower morphology [12] and climatic niche [13]. The fit between the current models and the real evolutionary processes is widely discussed [5, 18], and the power for selecting models depends on the number of taxa, the shape of the phylogeny, and the presence of measurements errors [19]
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