Genetics and geography in Pacific coast chitons (Mollusca: Polyplacophora).

摘要

Molecular methods provide fine-scale resolution into the mechanisms underlying biological complexity. Here, I apply these methods to a variety of chiton (Mollusca: Polyplacophora) species from the intertidal to shallow subtidal zones of the eastern Pacific at the population, species, and genus levels in order to uncover patterns and processes of intertidal biodiversity across multiple scales. This study consists of four parts. First, I introduce a method of DNA barcoding that complements and outperforms existing approaches to DNA sequence-assisted taxonomy and species identification. Second, I estimate the phylogeny of a chiton genus (Mopalia) for the first time using multilocus molecular data. Mopalia represents a marine species flock, likely the result of a rapid and relatively recent radiation, and has implications for the understanding of biogeography and speciation in the marine environment. Third, I compare population genetics and phylogeographic patterns of approximately 30 Pacific chiton species, revealing a latitudinal gradient in population connectivity and a cryptic barrier to gene flow along the coast. These patterns are expected to be similar in many other intertidal invertebrates with lecithotrophic larval development, and have not been reported elsewhere. Finally, I synthesize the abovementioned results and discuss them in the larger context of marine genetics research.