Baja California disjunctions and phylogeographic patterns in sympatric California blennies

Giacomo Bernardi

doi:10.3389/fevo.2014.00053

Abstract

Baja California disjuncts, which are marine species that are present in the northern Sea of Cortez and along the Pacific Coast of California and Baja California, but absent from the south, have been shown to be interesting models of allopatric speciation. While at least 19 species of fish are Baja California disjuncts, no study has ever evaluated the genetic patterns of closely related species. Here, we used three sympatric California blennies (genus Hypsoblennius), where two species have disjunct populations and one does not. Based on one mitochondrial and one nuclear molecular marker, we found that the two disjunct species exhibit different genetic patterns, one species showing disjunct populations as reciprocally monophyletic assemblages, while the other species showed evidence of gene flow between disjunct populations. In addition, the non-disjunct species, H. gilberti, exhibits high gene flow along the California and Baja California coasts. I hypothesized that adult habitat and historical vicariant events, more so than pelagic larval duration, played major roles in shaping the currently observed distribution and genetic patterns for these species.

Highlights

Phylogeographic approaches provide insight in understanding the processes leading to speciation (Avise, 2000; Bernardi, 2013)
Based on one mitochondrial and one nuclear molecular marker, we found that the two disjunct species exhibit different genetic patterns, one species showing disjunct populations as reciprocally monophyletic assemblages, while the other species showed evidence of gene flow between disjunct populations
While the three focal Hypsoblennius species seem superficially very similar in most respects, some unique characteristics must have played a role in defining differences in distribution and population genetics

Summary

Introduction

Phylogeographic approaches provide insight in understanding the processes leading to speciation (Avise, 2000; Bernardi, 2013) Such approaches are powerful when used in comparative ways either by employing different molecular markers, or several species that share common geographic distributions (Bernardi et al, 2003; Eble et al, 2009; Toonen et al, 2011; Von der Heyden et al, 2011; Dawson, 2012). An alternative way to address complex scenarios is to use comparative methods with closely related species. This is rarely done because there are few cases where related species that are amenable to a comparative phylogeographic approach live in sympatry (Crow et al, 2010; Bird et al, 2011). Two of those species have Baja California disjunct populations, which are isolated in the northern Sea of Cortez (Gulf of California)

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