Abstract
Comparing many species' population genetic patterns across the same seascape can identify species with different levels of structure, and suggest hypotheses about the processes that cause such variation for species in the same ecosystem. This comparative approach helps focus on geographic barriers and selective or demographic processes that define genetic connectivity on an ecosystem scale, the understanding of which is particularly important for large-scale management efforts. Moreover, a multispecies dataset has great statistical advantages over single-species studies, lending explanatory power in an effort to uncover the mechanisms driving population structure. Here, we analyze a 50-species dataset of Pacific nearshore invertebrates with the aim of discovering the most influential structuring factors along the Pacific coast of North America. We collected cytochrome c oxidase I (COI) mtDNA data from populations of 34 species of marine invertebrates sampled coarsely at four coastal locations in California, Oregon, and Alaska, and added published data from 16 additional species. All nine species with non-pelagic development have strong genetic structure. For the 41 species with pelagic development, 13 show significant genetic differentiation, nine of which show striking FST levels of 0.1–0.6. Finer scale geographic investigations show unexpected regional patterns of genetic change near Cape Mendocino in northern California for five of the six species tested. The region between Oregon and Alaska is a second focus of intraspecific genetic change, showing differentiation in half the species tested. Across regions, strong genetic subdivision occurs more often than expected in mid-to-high intertidal species, a result that may reflect reduced gene flow due to natural selection along coastal environmental gradients. Finally, the results highlight the importance of making primary research accessible to policymakers, as unexpected barriers to marine dispersal break the coast into separate demographic zones that may require their own management plans.
Highlights
Uncovering mechanisms that determine gene flow is critical for understanding population ecology, the scale of natural selection across environmental gradients, and decisions about sustainable exploitation
Among 41 species with pelagic larvae, we found genetic differentiation in 13 (32%)
Comparison of similar data sets among many species in a similar geographic context allows tests of hypotheses about the factors associated with genetic structure and low gene flow
Summary
Uncovering mechanisms that determine gene flow is critical for understanding population ecology, the scale of natural selection across environmental gradients, and decisions about sustainable exploitation This is especially true where conservation strategies emphasize the creation of management zones such as wildlife parks or marine protected areas [see 1]. Instead, understanding the population genetic patterns and the processes that create them for a wide set of species within a habitat has become an important part of the goal [5] Such data are relevant in marine ecosystems because of the possibility that many species have wide dispersal [6], and the increasing focus on marine protected areas as a management strategy [1]. Comparing population genetic patterns across the same seascape for many species can allow initial identification of species with different levels of structure, and test hypotheses about the processes that create dispersal variation for species in the same ecosystem
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