The fundamental research goal of this project is to understand the relative roles of evolutionary history, geography, and ecology in producing the morphological and behavioral diversity of the antbirds (Thamnophilidae), a species-rich group of birds that inhabit lowland tropical forests of South and Central America. The integration of genetic data with morphological, behavioral, ecological, geographic, and environmental data for every species in the group will allow increased understanding of differences in vocalizations, shapes, sizes, and species numbers within the antbirds.
Understanding why some groups of organisms are more diverse than others, and why some groups exhibit more behavioral and morphological variation, is a central goal of evolutionary biology. It is well known that diversity does not evolve uniformly over time, and that differences in morphological and behavioral diversity are often correlated with the number of species in the group. It remains unclear, however, to what extent the evolution of behavioral and morphological diversity promotes the creation of new species. The integration of genetic, geographic, ecological, behavioral and morphological information, along with cutting-edge analytical approaches, in this project will allow insights into the mechanisms that generate and maintain biological diversity in the Neotropics.
INTELLECTUAL MERIT A pervasive goal in evolutionary biology has been to address why some clades are richer in species or phenotypic diversity than others. This study used an integrative approach that combined phylogenetic, phenotypic, distributional, and ecological data to investigate large-scale patterns of evolution in a species-rich family of Neotropical birds. The Thamnophilidae is a large family of insectivorous passerine birds that provides great opportunities to study variation in species and phenotypic diversity. It comprises ca. 220 species that are mostly restricted to the lowlands and lower montane forests of the Neotropics. Its species are diverse in body size and shape, and the family exhibits high species richness, especially in Amazonian forests, where as many as 40 species may co-occur. By providing the first well-resolved phylogeny of the Thamnophilidae this study brought us closer to understanding diversity patterns in the Neotropics, and confirmed that the antbirds are not only a species-rich radiation of birds, but also a phenotypically diverse group that has accumulated species diversity in a near-constant fashion. Their species diversity patterns in space and time can be explained by the interaction of the effects of time with evolutionary processes that have affected net diversification rates over time. Observed patterns of phenotypic diversity are likely the result of various evolutionary mechanisms acting over time. Some environmental features, such as niche breadth and climatic heterogeneity, account for some of the variation that is observed in net diversification rates. Phenotypic diversification in the Thamnophilidae has occurred differently across phenotypic traits. Temporal patterns of phenotypic diversification in the family are consistent with an important role of adaptive evolution in the Thamnophilidae, which supposes an important role of the interaction between phenotype and the environment during the evolutionary history of the group. Diversification within the family led to highly specialized groups with conserved morphologies, such as dead-leaf searching and army-ant following birds, that not only are ecomorphologically adapted for specialized foraging, but also have constrained their vocal signals within optimal values of sound propagation in specific habitat and microhabitat conditions. Finally, my results open a window to understand the current geographical distribution of the Thamnophilidae, and provide an explanation for their absence in certain areas of the Neotropics. Their inability to disperse into or survive in different environmental conditions prevents colonization of subtropical regions where lowest temperatures as well as temperature seasonality are extreme relative to the tropics. Their absence in certain Neotropical regions (High Andes, Patagonia, xeric regions of Peru and Chile) might be associated with extreme environmental conditions that indirectly affect food resources, habitat, or microhabitat requirements of antbirds. A second possibility is that environmental conditions, especially low temperatures, are physiologically challenging, and therefore limit antbird successful survival. These ideas represent preliminary explanations for the absence of antbirds in these extreme environments that deserve further investigation. Finally, the genus and species-level taxonomic classifications of the Thamnophilidae have been subject to various changes due to the novel information revealed by the integrative approach followed here. It can be argued then, that this research has made various contributions in the fields of evolutionary biology, systematics, and taxonomy of Neotropical birds, and will allow a better understanding of how species richness and phenotypic diversity is created and maintained in the Neotropics. BROADER IMPACTS This project enhanced the collaborative relationships between Louisiana State University Museum of Natural Science and other institutions in the United States and Latin America. First, results of this project provided the baseline for further research on systematics and evolution of Suboscine passerines that will incorporate Next-Generation sequence data and a broader taxonomic scale. This project is currently conducted as part of a NSF Collaborative Research Grant and the Sao Paulo Research Foundation – FAPESP, and involves researchers from various institutions in the US and Brazil. PIs of this project continue to be active researchers in this initiative. Additionally, this project provided important training in laboratory and analytical skills to two Louisiana State University undergraduate students and provided the opportunities for two Colombian Masters students to successfully conduct and publish their work. All of these students continued with their graduate studies and became active members of the ornithological research community. Finally, through the description of new species to science, the formal documentation that the family represents a highly diverse radiation of birds, and the highlighted importance of certain dry habitats in their evolutionary history, it has called attention to immediate conservation issues that must be addressed as soon as possible. Therefore, this research has benefited future activities in the field of Conservation Biology.
