Applying integrative multispecies coalescent models to tackle the long-standing problem of species delimitation in allopatrically distributed populations

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Multispecies coalescent-based models (MSC) were proposed as a solution for the crucial problem of species delimitation. But recent work suggested that these models tend to over-split allopatric populations as they are affected by population structure rather than species divergence alone. We propose to address the problem of species delimitation using allopatric populations of a Neotropical fish family, the Anablepidae, in which taxonomy and systematics have been in flux in the last years and several new species have been recently described, also by us. This family provides an interesting system to study general species delimitation problems as it contains both described species whose populations occur in drainages that have been isolated for several million years (i.e., negligible gene flow), whereas some pairs of species are parapatric within drainages (i.e., potential for gene flow). Additionally, these fish are easy to breed under controlled conditions, allowing to do specific crosses to test if reproductive isolation, the major requirement for the completion of speciation according to the Biological Species Concept, has indeed evolved between separate coalescent lineages. We aim to integrate whole-genome resequencing data (the Vertebrate Genome Project will soon release a reference genome for the family) and phenotypic data (> 70 morphological characters and geometric morphometrics) to apply newly developed coalescent-based integrative taxonomic approaches that combine these data sets, as well as use genomic data to conduct Bayesian parameter estimation combined with heuristic genealogical divergence index. Then, we will validate the output of the MSC-based species delimitations by contrasting it to the empirically determined degree of reproductive isolation among species pairs. Finally, we will partition our molecular data to study the impact of locus selection on MSC-based species delimitation. The familiy Anablepidae constitutes a relatively small family of fish with only about 20 taxa and provides a manageable, but evolutionary highly interesting test case in which one can compare, and exhaustively test, these new methods to aid in the identification, classification and description of new species that can be later scaled up to other more species-rich lineages.