Barber Paul H.

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Barber
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Paul H.
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  • Article
    Rapid recovery of genetic diversity of stomatopod populations on Krakatau : temporal and spatial scales of marine larval dispersal
    (Royal Society, 2002-07-09) Barber, Paul H. ; Moosa, M. K. ; Palumbi, S. R.
    Although the recovery of terrestrial communities shattered by the massive eruption of Krakatau in 1883 has been well chronicled, the fate of marine populations has been largely ignored. We examined patterns of genetic diversity in populations of two coral reef-dwelling mantis shrimp, Haptosquilla pulchella and Haptosquilla glyptocercus (Stomatopoda: Protosquillidae) , on the islands of Anak Krakatau and Rakata. Genetic surveys of mitochondrial cytochrome oxidase c (subunit 1) in these populations revealed remarkably high levels of haplotypic and nucleotide diversity that were comparable with undisturbed populations throughout the Indo-Pacific. Recolonization and rapid recovery of genetic diversity in the Krakatau populations indicates that larval dispersal from multiple and diverse source populations contributes substantially to the demographics of local populations over intermediate temporal (tens to hundreds of years) and spatial scales (tens to hundreds of kilometres). Natural experiments such as Krakatau provide an excellent mechanism to investigate marine larval dispersal and connectivity. Results from stomatopods indicate that marine reserves should be spaced no more than 50-100 km apart to facilitate ecological connectivity via larval dispersal.
  • Article
    Episymbiotic microbes as food and defence for marine isopods : unique symbioses in a hostile environment
    (Royal Society, 2005-06-14) Lindquist, Niels ; Barber, Paul H. ; Weisz, Jeremy B.
    Symbioses profoundly affect the diversity of life, often through novel biochemical services that symbionts provide to their hosts. These biochemical services are typically nutritional enhancements and less commonly defensive, but rarely both simultaneously. On the coral reefs of Papua New Guinea, we discovered unique associations between marine isopod crustaceans (Santia spp.) and episymbiotic microbes. Transmission electron microscopy and pigment analyses show that episymbiont biomass is dominated by large (20–30μm) cyanobacterial cells. The isopods consume these photosymbionts and ‘cultivate’ them by inhabiting exposed sunlit substrates, a behaviour made possible by symbionts' production of a chemical defence that is repulsive to fishes. Molecular phylogenetic analyses demonstrated that the symbiotic microbial communities are diverse and probably dominated in terms of population size by bacteria and small unicellular Synechococcus-type cyanobacteria. Although largely unknown in the oceans, defensive symbioses probably promote marine biodiversity by allowing niche expansions into otherwise hostile environments.
  • Preprint
    Limited genetic variation and structure in softshell clams (Mya arenaria) across their native and introduced range
    ( 2008-06) Strasser, Carly A. ; Barber, Paul H.
    To offset declines in commercial landings of the softshell clam, Mya arenaria, resource managers are engaged in extensive stocking of seed clams throughout its range in the northwest Atlantic. Because a mixture of native and introduced stocks can disrupt locally adapted genotypes, we investigated genetic structure in M. arenaria populations across its current distribution to test for patterns of regional differentiation. We sequenced mitochondrial cytochrome oxidase I (COI) for a total of 212 individuals from 12 sites in the northwest Atlantic (NW Atlantic), as well as two introduced sites, the northeast Pacific (NE Pacific) and the North Sea and Europe (NS Europe). Populations exhibited extremely low genetic variation, with one haplotype dominating (65-100%) at all sites sampled. Despite being introduced in the last 150-400 years, both NE Pacific and NS Europe populations had higher diversity measures than those in the NW Atlantic and both contained private haplotypes at frequencies of 10% to 27% consistent with their geographic isolation. While significant genetic structure (FST = 0.159, p<0.001) was observed between NW Atlantic and NS Europe, there was no evidence for genetic structure across the pronounced environmental clines of the NW Atlantic. Reduced genetic diversity in mtDNA combined with previous studies reporting reduced genetic diversity in nuclear markers strongly suggests a recent population expansion in the NW Atlantic, a pattern that may result from the retreat of ice sheets during Pleistocene glacial periods. Lack of genetic diversity and regional genetic differentiation suggests that present management strategies for the commercially important softshell clam are unlikely to have a significant impact on the regional distribution of genetic variation, although the possibility of disrupting locally adapted stocks cannot be excluded.
  • Preprint
    Evolutionary variation in the expression of phenotypically plastic color vision in Caribbean mantis shrimps, genus Neogonodactylus
    ( 2006-03-07) Cheroske, Alexander G. ; Barber, Paul H. ; Cronin, Thomas W.
    Many animals have color vision systems that are well suited to their local environments. Changes in color vision can occur over long periods (evolutionary time), or over relatively short periods such as during development. A select few animals, including stomatopod crustaceans, are able to adjust their systems of color vision directly in response to varying environmental stimuli. Recently, it has been shown that juveniles of some stomatopod species that inhabit a range of depths can spectrally tune their color vision to local light conditions through spectral changes in filters contained in specialized photoreceptors. The present study quantifies the potential for spectral tuning in adults of three species of Caribbean Neogonodactylus stomatopods that differ in their depth ranges to assess how ecology and evolutionary history influence the expression of phenotypically plastic color vision in adult stomatopods. After 12 weeks in either a full-spectrum “white” or a narrow-spectrum “blue” light treatment, each of the three species evidenced distinctive tuning abilities with respect to the light environment that could be related to its natural depth range. A molecular phylogeny generated using mitochondrial cytochrome oxidase C subunit 1 (CO-1) was used to determine whether tuning abilities were phylogenetically or ecologically constrained. Although the sister taxa N. wennerae and N. bredini both exhibited spectral tuning, their ecology (i.e. preferred depth range) strongly influenced the expression of the phenotypically plastic color vision trait. Our results indicate that adult stomatopods have evolved the ability to undergo habitat-specific spectral tuning, allowing rapid facultative physiological modification to suit ecological constraints.
  • Article
    Genetic identity determines risk of post-settlement mortality of a marine fish
    (Ecological Society of America, 2007-05) Vigliola, Laurent ; Doherty, Peter J. ; Meekan, Mark G. ; Drown, Devin M. ; Jones, M. Elizabeth ; Barber, Paul H.
    Longitudinal sampling of four cohorts of Neopomacentrus filamentosus, a common tropical damselfish from Dampier Archipelago, Western Australia, revealed the evolution of size structure after settlement. Light traps collected premetamorphic individuals from the water column (“settlers”) to establish a baseline for each cohort. Subsequently, divers collected benthic juveniles (“recruits”) at 1–3-month intervals to determine the relative impacts of post-settlement mortality during the first three months. Growth trajectories for individual fish were back-calculated from otolith records and compared with nonlinear mixed-effects models. Size-selective mortality was detected in all cohorts with the loss of smaller, slower growing individuals. Three months after settlement, recruits showed significantly faster growth as juveniles, faster growth as larvae, and larger sizes as hatchlings. The timing and intensity of post-settlement selection differed among cohorts and was correlated with density at settlement. The cohort with the greatest initial abundance experienced the strongest selective mortality, with most of this mortality occurring between one and two months after settlement when juveniles began foraging at higher positions in the water column. Significant genetic structure was found between settlers and three-month-old recruits in this cohort as a result of natural selection that changed the frequency of mtDNA haplotypes measured at the control region. The extent of this genetic difference was enlarged or reduced by artificially manipulating the intensity of size-based selection, thus establishing a link between phenotype and haplotype. Sequence variation in the control region of the mitochondrial genome has been linked to mitochondrial efficiency and weight gain in other studies, which provides a plausible explanation for the patterns observed here.