Meeting Abstract
The rate of DNA substitution is an essential parameter as it offers evolutionary biologists the ability to put a timescale on the history of life. Calibration of this rate requires independent information on the timing of species divergence. The final closure of the Isthmus of Panama, approximately 2.7 to 3.5 mya, created a nearly impenetrable barrier to gene flow for thousands of marine taxa. By far the most cited transisthmian-based molecular clock calibrations comes from the snapping shrimp genus Alpheus. Most transisthmian molecular clock calibrations have been limited to nucleotide sequence data from mitochondrial genes. The development of reduced representation library techniques, such as Genotype-by-Sequencing (GBS), offers powerful tools for both identifying and genotyping genome-wide loci for use in phylogeographic studies. Basic information regarding the rate and patterns of nucleotide substitutions across loci targeted by approaches like GBS are needed to fully make use of genome-wide polymorphism data in population genetic and phylogeographic studies. We conducted a comparative genomic study on three transisthmian Alpheus species pairs to examine rates and patterns of molecular divergence across the nuclear genome. GBS datasets were generated for three species pairs, A. malleator/ A. wonkimi, A. formosus/ A. panamensis, and A. colombiensis /A. estuarensis. Previous work suggested that divergence times for these taxa were contemporaneous and likely to have resulted from the final closure of the Isthmus. Coalescent-based Bayesian methods, including G-PhoCS, were used to examine the rates of DNA substitutions that accumulated across the nuclear genome. To our knowledge this is the first use of transisthmian species pairs to calibrate the rate of molecular evolution across the nuclear genome.
