Abstract
Life‐history traits, especially the mode and duration of larval development, are expected to strongly influence the population connectivity and phylogeography of marine species. Comparative analysis of sympatric, closely related species with differing life histories provides the opportunity to specifically investigate these mechanisms of evolution but have been equivocal in this regard. Here, we sample two sympatric sea stars across the same geographic range in temperate waters of Australia. Using a combination of mitochondrial DNA sequences, nuclear DNA sequences, and microsatellite genotypes, we show that the benthic‐developing sea star, Parvulastra exigua, has lower levels of within‐ and among‐population genetic diversity, more inferred genetic clusters, and higher levels of hierarchical and pairwise population structure than Meridiastra calcar, a species with planktonic development. While both species have populations that have diverged since the middle of the second glacial period of the Pleistocene, most P. exigua populations have origins after the last glacial maxima (LGM), whereas most M. calcar populations diverged long before the LGM. Our results indicate that phylogenetic patterns of these two species are consistent with predicted dispersal abilities; the benthic‐developing P. exigua shows a pattern of extirpation during the LGM with subsequent recolonization, whereas the planktonic‐developing M. calcar shows a pattern of persistence and isolation during the LGM with subsequent post‐Pleistocene introgression.
Highlights
Life-history traits, such as location of fertilization, egg mass deposition, and mode of larval development, have long been thought to be the primary factors governing micro- and macro-evolutionary processes and patterns in the sea (Jablonski, 1986, 2000; Palumbi, 1994; Strathmann, 1990, 1993)
All else being equal, these differences in reproductive and developmental modes make clear predictions about the degree of gene flow and scale of population genetic structure expected in comparisons of these two species, but results of such comparisons have been somewhat mixed to date
We showed on several different hierarchical levels and across three different types of genetic markers that the benthic larval development of P. exigua leads to higher levels of genetic structure and consistently lower levels of genetic diversity when compared to M. calcar, a sympatric species with planktonic development
Summary
Life-history traits, such as location of fertilization (i.e., broadcast spawning vs. direct sperm delivery), egg mass deposition (i.e., benthic vs. pelagic), and mode of larval development (i.e., feeding vs. nonfeeding), have long been thought to be the primary factors governing micro- and macro-evolutionary processes and patterns in the sea (Jablonski, 1986, 2000; Palumbi, 1994; Strathmann, 1990, 1993). Recent applications of landscape (seascape)-based analyses have shown that other factors such as habitat (Selkoe et al, 2010), ocean currents (White et al 2010), and even proximity to coastal pollution (Puritz & Toonen, 2011) can significantly impact the population connectivity of marine species (reviewed in Selkoe et al, 2016) These studies highlight that sweeping generalizations about the role of pelagic larval duration are difficult to make and do not alone explain the observed variation among populations (Liggins et al, 2016; Riginos, Douglas, Jin, Shanahan, & Treml, 2011; Riginos & Liggins, 2013; Selkoe, Gaggiotti, Bowen, & Toonen, 2014; Weersing & Toonen, 2009). We conclude that inferred gene flow and genetic diversity of these two species conform better to previous work using allozymes than to conclusions based solely on mitochondrial COI data
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