Lessios HA, Robertson DR.. Crossing the impassable: genetic connections in 20 reef fishes across the eastern Pacific barrier. Proc R Soc B Biol Sci 273: 2201-2208

Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Panama.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 10/2006; 273(1598):2201-8. DOI: 10.1098/rspb.2006.3543
Source: PubMed


The 'impassable' Eastern Pacific Barrier (EPB), ca 5000 km of deep water separating the eastern from the central Pacific, is the World's widest marine biogeographic barrier. Sequencing of mitochondrial DNA in 20 reef fish morphospecies encountered on both sides of the barrier revealed cryptic speciation in two. Among the other 18 species only two showed significant differentiation (as revealed by haplotype networks and FST statistics) between the eastern and the central Pacific. Coalescence analyses indicated that genetic similarity in the 18 truly transpacific species resulted from different combinations of ages of most recent invasion and of levels of recurrent gene flow, with estimated times of initial separation ranging from approximately 30000 to 1 Myr (ago). There is no suggestion of simultaneous interruptions of gene flow among the species. Migration across the EPB was previously thought to be exclusively eastward, but our evidence showed two invasions from east to west and eight cases in which subsequent gene flow possibly proceeded in the same direction. Thus, the EPB is sporadically permeable to propagules originating on either side.

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Available from: Harilaos Lessios, May 12, 2014
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    • "For all species, we targeted the mtDNA control region (CR) to infer genetic patterns using DNA extraction and amplification protocols detailed inMirams et al. (2011). A suitable length of CR proved difficult to amplify for A. triostegus, so we used ATPase subunit 6 and 8 (ATP6-8) amplified with ATP8.2 and CO3.2 (Lessios & Robertson, 2006). Amplicons were purified, sequenced, and sequences were manually checked and aligned as perLiggins et al. (2015). "
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    ABSTRACT: AimTo determine which seascape features have shaped the spatial genetic patterns of coral reef fishes, and to identify common patterns among species related to dispersal traits [egg type and pelagic larval duration (PLD)].LocationIndian and Pacific Oceans, including the Indo-Australian Archipelago.Methods We sampled coral reef fishes with differing dispersal traits (Pomacentrus coelestis, Dascyllus trimaculatus, Hailchoeres hortulanus and Acanthurus triostegus) and characterized spatial (mtDNA) genetic patterns using AMOVA-clustering and measures of genetic differentiation. Similarity in the spatial genetic patterns among species was assessed using the congruence among distance matrices method and the seascape features associated with the genetic differentiation of each species were identified using multiple regression of distance matrices (MRDM) and stepwise model selection.ResultsSimilar spatial genetic patterns were found for P. coelestis and H. hortulanus, despite their differing egg type (benthic versus pelagic). MRDM indicated that geographical distance was underlying their correlated genetic patterns. Species with pelagic eggs (A. triostegus and H. hortulanus) also had correlated patterns of genetic differentiation (Dest); however, a common underlying seascape feature could not be inferred. Additionally, the common influence of the Torres Strait and the Lydekker/Weber's line was identified for the genetic patterns of differentiation for P. coelestis and A. triostegus, despite their differing dispersal traits, and the uncorrelated spatial genetic patterns of these species.Main conclusionsOur study demonstrates the value of a quantitative, hypothesis-testing framework in comparative phylogeography. We found that dispersal traits (egg type and PLD) did not predict which species had similar spatial genetic patterns or which seascape features were associated with these patterns. Furthermore, even in the absence of visually similar, or correlated spatial genetic patterns, our approach enabled us to identify seascape features that had a common influence on the spatial genetic patterns of co-distributed species.
    Full-text · Article · Feb 2016 · Journal of Biogeography
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    • "Flotsam may function as a habitat substitute for fish in transition from a pelagic to a demersal life stage (Hunter & Mitchell, 1967), acting as a nursery refuge for juvenile reef fishes that have not yet located the reef habitat at the end of the pelagic-larval stage (Kingsford, 1993; Wells & Rooker, 2004). Large expanses of open ocean represent essentially impassable barriers to terrestrial and near-shore marine organisms that are unable to survive in the pelagic realm, or that have either no pelagic dispersal stage or one of short duration (Lessios & Robertson, 2006; Kleiber et al., 2011). For reef fishes, rafts can provide a suitable substratum at the stage when they would normally settle into benthic habitats, and thus can potentially enhance the probability of long-distance dispersal (Mora et al., 2001; Robertson et al., 2004). "
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    ABSTRACT: AimRafting with natural flotsam is an important mechanism of long-distance oceanic dispersal for many near-shore marine organisms. Identifying the species-level traits associated with this behaviour would aid in understanding and predicting a species' capacity for dispersal between isolated areas of benthic habitat.LocationThe tropical and subtropical Atlantic.Methods We assessed the relationships between species-level traits (habitat use, position in water column, diet, body size, schooling activity) and rafting behaviour among 985 species of reef fish using generalized linear mixed-effect modelling. To assess whether the relationships between rafting behaviour and species traits were mediated by raft type, our analysis included interactions between raft type and our predictor variables.ResultsThe following species-level traits are positively associated with rafting for reef fishes: (1) position in water column above reef substratum, which indicates a species' dependency on the substratum; (2) schooling behaviour, a trait linked to predation avoidance; (3) large adult size, which may be associated with enhanced survivorship and growth of rafting juveniles; and (4) broad habitat use, which may facilitate use of atypical habitats, including flotsam. Some correlations varied depending on the type of flotsam – broad habitat use is only positively correlated with the use of seaweed rafts, which may resemble patches of benthic macroalgal and seagrass beds that the reef fishes often use as ancillary habitat. In contrast, schooling behaviour is only positively correlated with rafting among logs and similar objects, perhaps because they represent poor refuges from predation.Main conclusionsA species' propensity to use rafts is associated with specific ecological traits, some of which are contingent on characteristics of the raft. Thus, our findings suggest that increasing amounts of man-made flotsam entering the ocean may differentially influence future rafting opportunities among tropical reef fishes, depending on their traits, which may have important implications for their biogeographical distributions.
    Full-text · Article · Jul 2015 · Journal of Biogeography
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    • "The SST over the latter period averaged ∼ 0.6 °C warmer than the preceding 15 years (consistent with Figure 14d in Rayner et al., 2006). The colonisation of an oceanic archipelago by a littoral species in historical times represents a notable example of the effectiveness of sporadic larval dispersal events in suitable climatic conditions (Lessios and Robertson, 2006). The temperature rise that affected the North-East Atlantic sea surface waters caused an impact on the circulation patterns around the Azores. "
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    ABSTRACT: The processes and timescales associated with ocean-wide changes in the distribution of marine species have intrigued biologists since Darwin’s earliest insights into biogeography. The Azores, a mid-Atlantic volcanic archipelago located 41000 km off the European continental shelf, offers ideal opportunities to investigate phylogeographic colonisation scenarios. The benthopelagic sparid fish known as the common two-banded seabream (Diplodus vulgaris) is now relatively common along the coastline of the Azores archipelago, but was virtually absent before the 1990s. We employed a multiple genetic marker approach to test whether the successful establishment of the Azorean population derives from a recent colonisation from western continental/island populations or from the demographic explosion of an ancient relict population. Results from nuclear and mtDNA sequences show that all Atlantic and Mediterranean populations belong to the same phylogroup, though microsatellite data indicate significant genetic divergence between the Azorean sample and all other locations, as well as among Macaronesian, western Iberian and Mediterranean regions. The results from Approximate Bayesian Computation indicate that D. vulgaris has likely inhabited the Azores for ∼40 (95% confidence interval (CI): 5.5–83.6) to 52 (95% CI: 6.32–89.0) generations, corresponding to roughly 80–150 years, suggesting near-contemporary colonisation, followed by a more recent demographic expansion that could have been facilitated by changing climate conditions. Moreover, the lack of previous records of this species over the past century, together with the absence of lineage separation and the presence of relatively few private alleles, do not exclude the possibility of an even more recent colonisation event.
    Full-text · Article · Jul 2015 · Heredity
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