BJT Postdoctoral Research:
Comparative Phylogeography and Phylogenetic Community Ecology of Freshwater Fishes of the Cerrado
This research was funded by a BJT, or Young Talent Fellow (Atração de Jovens Talentos – BJT), award from Brazil’s CNPq Science Without Borders program (Ciência Sem Fronteiras) and we are in final stages of analyses and preparation of manuscripts resulting from the project. What follows is an overview that closely mirrors the Abstract from the original proposal, which is available from the drop-down menu above, or link at the bottom of the page.
The greatest diversity of freshwater fishes worldwide (~4600/13,000 species, or ~35% of all freshwater fishes) is concentrated in the rivers and lakes of the South American Neotropics. Within the Cerrado biodiversity hotspot of central-eastern Brazil, freshwater fish communities are highly diversified (~1200 species), endemic, and threatened by human activities. Fishes of the Araguaia-Tocantins, Upper Paraná, and São Francisco basins are respectively 44%, 48%, and 59% endemic, and each basin contains 181-346 species. Despite this, Cerrado freshwater fishes have been largely overlooked in studies of biodiversity and conservation relative to Amazonian taxa. Thus, basic geographical and biological data are lacking or incomplete for many Cerrado species: Cerrado fishes exemplify “Linnean” and “Wallacean” shortfalls in systematics and taxonomy, due to incomplete knowledge of species and their distributions, respectively. Moreover, the ecological and evolutionary processes that generate and maintain Cerrado fish biodiversity and species interactions remain poorly documented.
The objective of my present postdoctoral research project is to provide a groundbreaking perspective on the ecology and evolution of freshwater fishes communities from Cerrado headwater streams by integrating 1) comparative phylogeography and 2) phylogenetic community ecology. This project expands my research program to leverage genomic data from Next-Generation Sequencing (e.g. single nucleotide polymorphisms, or ‘SNPs’, from Rad tag reads) to test hypotheses about historical and ecological processes driving Neotropical fish community assembly and responses to past geological and climate changes, with a focus on headwater fishes. Moreover, through mentored collaborations with undergraduates, I integrate phylogeography and morphological analyses to strengthen the integrity and stability of regional fish taxonomy through testing hypotheses of species boundaries and formally describing new species using integrative taxonomy.
In the comparative phylogeography component of the project, I develop genomic datasets for headwater populations of three fish species/lineages (Hasemania hanseni, Hypostomus sp., Characidium fasciatum) codistributed in the major drainage basins of the Cerrado: the Upper Tocantins, Upper Paraná, and São Francisco basins. Mitochondrial DNA gene sequences and SNPs are analyzed while drawing on recent advances in coalescent modeling, statistical phylogeography, and phylogenomics, in order to test for shared biogeographic responses to drainage history, especially geological changes in drainage configurations due to headwater river-capture events. This work is elucidating general evolutionary patterns, including whether historical processes have causes speciation and/or extinction to co-occur across multiple lineages. Also, genetic data contribute to descriptions of new species discovered during our fieldwork and genetic analyses.
The phylogenetic community ecology component of the project combines data on community composition from 30 sites with a multilocus phylogeny developed for the regional fish assemblage in order to test several hypotheses. First, we examine whether fish species coexisting in headwater streams tend to be more or less related than expected by chance. Second, we re-test whether communities in basin areas hypothesized to have been captured more recently in geological time (i.e. in the Upper Tocantins) are also evolutionarily younger, with lower phylogenetic diversity than other community samples. Third, we test whether phylogenetic structuring depends on species richness or mean body size of coexisting species. Fourth, we test the hypothesis that functional traits such as body size are phylogenetically conserved in community ecological samples. Last, we test the influence of mode of speciation in a clade on phylogenetic community structure by investigating whether species with correlated phylogenetic relatedness and co-occurrence are congeners from clades that underwent allopatric speciation then came into secondary contact, or members of faster radiations that could be sufficiently dissimilar to coexist. Here, evidence for phylogenetic clustering of related species can be taken as evidence of environmental filtering, whereas the opposite pattern, phylogenetic evenness, indicates that limiting similarity and competition have influenced community structure.
This project is facilitating multi-institutional collaborations between a network of investigators at the Universidade de Brasília in the federal capital of Brazil, Universidade Estadual Paulista located in São Paulo state, and Universidade Federal do Amazonas, in Manaus, Brazil. Indeed, this is leading to unforeseen outcomes; for example, we have been able to develop additional collaborations ancillary to the main project, and one of these uses anchored phylogenomics data to test the relative contributions of ecological versus historical processes in generating the diversity of Cerrado herpetofauna through a comparative phylogeographical analysis of three species of Cerrado lizards. Another recently spawned project is an international collaboration testing for the population genetic effects of deforestation at the “Arc of Deforestation” ecotone between the Amazonia and Cerrado biomes, also using phylogeography of herpetofauna.
Bagley JC, Aquino PPU, Hernandez S, Hrbek T, Colli GR, Langeani F (in revision.) Using ddRAD-seq phylogeography to test for genetic effects of headwater river capture in suckermouth armored catfish (Loricariidae: Hypostomus) from the central Brazilian Shield. Molecular Ecology.
Domingos FMCB, Bagley JC, Lemmon A, Colli GR, Beheregaray LB (in prep.) A comparative phylogeographical test of effects of ecology and history on the evolution of a Neotropical biodiversity hotspot using three lizard species. Systematic Biology.
Disclosure: partial funded proposal abstract in English and Portuguese