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Living in the past: phylogeography and population histories of Indo-Pacific wrasses (genus Halichoeres) in shallow lagoons versus outer reef slopes.

Ludt WB, Bernal MA, Bowen BW, Rocha LA - PLoS ONE (2012)

Bottom Line: The outer reef species showed significantly less population structure, consistent with longer pelagic larval durations.Mismatch distributions and significant negative Fu's F values indicate Pleistocene population expansion for all species, and (contrary to expectations) shallower histories in the outer slope species.We conclude that lagoonal wrasses may persist through glacial habitat disruptions, but are restricted to refugia during lower sea level stands.

View Article: PubMed Central - PubMed

Affiliation: Department of Marine Science, University of Texas, Austin, Texas, United States of America. wbludt@gmail.com

ABSTRACT
Sea level fluctuations during glacial cycles affect the distribution of shallow marine biota, exposing the continental shelf on a global scale, and displacing coral reef habitat to steep slopes on oceanic islands. In these circumstances we expect that species inhabiting lagoons should show shallow genetic architecture relative to species inhabiting more stable outer reefs. Here we test this expectation on an ocean-basin scale with four wrasses (genus Halichoeres): H. claudia (N = 194, with ocean-wide distribution) and H. ornatissimus (N = 346, a Hawaiian endemic) inhabit seaward reef slopes, whereas H. trimaculatus (N = 239) and H. margaritaceus (N = 118) inhabit lagoons and shallow habitats throughout the Pacific. Two mitochondrial markers (cytochrome oxidase I and control region) were sequenced to resolve population structure and history of each species. Haplotype and nucleotide diversity were similar among all four species. The outer reef species showed significantly less population structure, consistent with longer pelagic larval durations. Mismatch distributions and significant negative Fu's F values indicate Pleistocene population expansion for all species, and (contrary to expectations) shallower histories in the outer slope species. We conclude that lagoonal wrasses may persist through glacial habitat disruptions, but are restricted to refugia during lower sea level stands. In contrast, outer reef slope species have homogeneous and well-connected populations through their entire ranges regardless of sea level fluctuations. These findings contradict the hypothesis that shallow species are less genetically diverse as a consequence of glacial cycles.

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Simulated mismatch distributions for each species and molecular marker.Observed mismatch distributions are represented by the bar graphs, while the curve represents the simulated distribution. P-values are reported for each marker. A) Halichoeres claudia, B) H. ornatissimus, C) H. trimaculatus, D) H. margaritaceus.
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pone-0038042-g005: Simulated mismatch distributions for each species and molecular marker.Observed mismatch distributions are represented by the bar graphs, while the curve represents the simulated distribution. P-values are reported for each marker. A) Halichoeres claudia, B) H. ornatissimus, C) H. trimaculatus, D) H. margaritaceus.

Mentions: All Fu’s F values were significant (P<0.001) and ranged from −31.71 to −14.55 (Tables 1 and 2). These values result from an excess of rare haplotypes, and indicate selection or population expansion [33]. Comparing the observed distribution of pairwise differences to simulated pairwise differences under a population expansion model [34], [35] failed to reject the model of sudden expansion in all species (P>0.13), except for CO1 in H. trimaculatus (P = 0.03, Fig. 5).


Living in the past: phylogeography and population histories of Indo-Pacific wrasses (genus Halichoeres) in shallow lagoons versus outer reef slopes.

Ludt WB, Bernal MA, Bowen BW, Rocha LA - PLoS ONE (2012)

Simulated mismatch distributions for each species and molecular marker.Observed mismatch distributions are represented by the bar graphs, while the curve represents the simulated distribution. P-values are reported for each marker. A) Halichoeres claudia, B) H. ornatissimus, C) H. trimaculatus, D) H. margaritaceus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368945&req=5

pone-0038042-g005: Simulated mismatch distributions for each species and molecular marker.Observed mismatch distributions are represented by the bar graphs, while the curve represents the simulated distribution. P-values are reported for each marker. A) Halichoeres claudia, B) H. ornatissimus, C) H. trimaculatus, D) H. margaritaceus.
Mentions: All Fu’s F values were significant (P<0.001) and ranged from −31.71 to −14.55 (Tables 1 and 2). These values result from an excess of rare haplotypes, and indicate selection or population expansion [33]. Comparing the observed distribution of pairwise differences to simulated pairwise differences under a population expansion model [34], [35] failed to reject the model of sudden expansion in all species (P>0.13), except for CO1 in H. trimaculatus (P = 0.03, Fig. 5).

Bottom Line: The outer reef species showed significantly less population structure, consistent with longer pelagic larval durations.Mismatch distributions and significant negative Fu's F values indicate Pleistocene population expansion for all species, and (contrary to expectations) shallower histories in the outer slope species.We conclude that lagoonal wrasses may persist through glacial habitat disruptions, but are restricted to refugia during lower sea level stands.

View Article: PubMed Central - PubMed

Affiliation: Department of Marine Science, University of Texas, Austin, Texas, United States of America. wbludt@gmail.com

ABSTRACT
Sea level fluctuations during glacial cycles affect the distribution of shallow marine biota, exposing the continental shelf on a global scale, and displacing coral reef habitat to steep slopes on oceanic islands. In these circumstances we expect that species inhabiting lagoons should show shallow genetic architecture relative to species inhabiting more stable outer reefs. Here we test this expectation on an ocean-basin scale with four wrasses (genus Halichoeres): H. claudia (N = 194, with ocean-wide distribution) and H. ornatissimus (N = 346, a Hawaiian endemic) inhabit seaward reef slopes, whereas H. trimaculatus (N = 239) and H. margaritaceus (N = 118) inhabit lagoons and shallow habitats throughout the Pacific. Two mitochondrial markers (cytochrome oxidase I and control region) were sequenced to resolve population structure and history of each species. Haplotype and nucleotide diversity were similar among all four species. The outer reef species showed significantly less population structure, consistent with longer pelagic larval durations. Mismatch distributions and significant negative Fu's F values indicate Pleistocene population expansion for all species, and (contrary to expectations) shallower histories in the outer slope species. We conclude that lagoonal wrasses may persist through glacial habitat disruptions, but are restricted to refugia during lower sea level stands. In contrast, outer reef slope species have homogeneous and well-connected populations through their entire ranges regardless of sea level fluctuations. These findings contradict the hypothesis that shallow species are less genetically diverse as a consequence of glacial cycles.

Show MeSH
Related in: MedlinePlus