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Stephen R. Wing Louis W. Botsford Lance E. Morgan Jennifer M. Diehl Carolyn J. Lundquist 《Estuarine, Coastal and Shelf Science》2003,57(5-6):859-872
We investigated sources of inter-annual variability in larval supply to crab and sea urchin populations at Bodega Head and Point Reyes in northern California. During the spring and summer upwelling seasons of the years 1992 through 1997 we monitored the weekly settlement rates of nine species of crabs and two species of sea urchins. As observed in previous studies, daily values of alongshore windstress, temperature and salinity provided evidence for the poleward flow of relatively warm, low salinity water from south of Point Reyes, an apparent retention zone, during upwelling relaxation events. In years dominated by these events (1992, 1993, 1995 and 1996) we observed that alongshore windstress, temperature and salinity were coherent and temperature was significantly correlated with cancrid crab settlement. During these years the magnitude of cancrid crab settlement and the fraction of cancrid crabs relative to other crab species settling were high. Over four years of concurrent sampling there was consistently greater cancrid crab settlement at the Point Reyes site, within the retention zone, than at Bodega Head. Settlement of non-cancrid crabs (porcellanids, grapsids, pagurids and majids) was not as closely linked to intra-annual patterns of upwelling and relaxation, possibly due to the shorter seasonal availability of larvae allowing for the influence of fewer relaxation events. Settlement of this group among years was positively correlated with environmental indicators of strong seasonal upwelling; high salinity, Bakun upwelling index and low temperature. Sea urchin settlement events were observed in June and July of 1992, 1994 and 1997 during warming periods when salinity and temperature were increasing and alongshore windstress was low. Across the six years of the study, we found that cancrid crab larvae had a more even seasonal availability than larvae of non-cancrid species, which settled in greatest numbers during the early portion of the upwelling season. Sea urchins settled in greatest numbers during the later part of the upwelling season. Together these patterns demonstrate the taxon-specific way that inter-annual variability in larval supply is forced by the coincidence of larval availability with favorable physical transport mechanisms. 相似文献
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In coastal populations of invertebrates and fishes, the distribution of discrete subpopulations is influenced by adult and larval dispersal, as well as by the effects of habitat heterogeneity on site fidelity or connectivity. Here, we examine evidence for spatial structure of sea perch, Helicolenus percoides, populations among four fjords in the Fiordland region of southwestern New Zealand. We examine patterns in adult morphology, length-at-age, δ13C and δ15N of muscle tissue, and trace elemental composition of whole otoliths as proxies for population isolation among the four inner fjord regions. A multivariate analysis of morphometrics reveals significant differences among populations from each of the four sites, suggesting existence of four distinct subpopulations. These patterns are consistent with observed differences in δ13C and δ15N, and length-at-age estimates among the four subpopulations. Differences in whole otolith concentrations of Sr, Ba, Mg and Li, and high classification scores based on the whole otolith elemental fingerprint are also consistent with significant subdivision among areas. Patterns across all four markers are consistent with discrete subpopulation structure of adult sea perch among the four study sites. These data indicate that the newly implemented network of marine protected areas in Fiordland is likely to contain discrete populations of sea perch. 相似文献
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Douglas T. Fischer J. Wilson White Louis W. Botsford John Largier David M. Kaplan 《The Professional geographer》2013,65(4):489-513
Increasing efforts to implement marine protected areas (MPAs) as a means of managing marine ecosystems have created a need for evaluating potential spatial management plans. Almost all marine populations are metapopulations, connected reproductively by the dispersal of pelagic larvae. Models of marine population dynamics must account for larval connectivity, but despite recent advances connectivity patterns are still poorly understood. To allow more informed decision making when complete information on dispersal is lacking, we have developed a method based on geographic information systems (GIS) for representing larval dispersal distributions based on bathymetry and typical flows in the coastal ocean. These distributions reflect (1) generally greater flow in directions along, rather than across, lines of constant bathymetry and (2) lesser flow in shallow near-shore waters. We demonstrate how to parameterize this two-dimensional method for depicting larval dispersal based on comparisons to local oceanographic data. We then compare the predictions of the two-dimensional method to those of a simpler one-dimensional alternative in a population model used to evaluate proposed MPAs along the coast of central California. The method produces reasonable larval dispersal patterns and appears to include the effects of bathymetry on population dynamics better than commonly used one-dimensional methods and without requiring the significantly greater investment of developing particle-tracking circulation models. An important advantage of a two-dimensional approach is more realistic portrayal of the dependence of population persistence on the cross-shelf dimension of available habitat. 相似文献
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Laura R. Lewis 《The Professional geographer》2013,65(3):377-394
Sahelian Africa makes up the native range of pearl millet and the impact of domestication on the genetic diversity of wild, intermediate, and cultivated subspecies is still poorly understood. Wild populations are known to spontaneously germinate throughout this range and hybridize with cultivated material. To investigate genetic structure, populations of pearl millet from several African countries were analyzed at the morphological and molecular levels for diversity. Results demonstrate how little differentiation there is between subspecies and populations. It appears that pearl millet throughout the Sahel remains a metapopulation with large hybrid zones. These results have important implications for conservation of pearl millet. 相似文献
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Larval dispersal is critical for the maintenance of species populations in patchy and ephemeral hydrothermal vent habitats. On fast‐spreading ridges, such as the East Pacific Rise, rates of habitat turnover are comparable to estimated lifespans of many of the inhabiting species. Traditionally, dispersal questions have been addressed with two very different approaches, larval studies and population genetics. Population genetic studies of vent‐endemic species have been informative for determining whether patterns of dispersal are suggestive of stepping stone or island models and estimating rates of gene flow (effective migrants per generation) over broad geographic ranges. However, these studies leave fundamental questions unanswered about the specific mechanisms by which larvae disperse and species maintain their populations and biogeographic ranges. With the goal of examining genetic structure and elucidating alternative larval dispersal mechanisms, we employed a genomic DNA fingerprinting technique, amplified fragment length polymorphisms (AFLPs). To assess the potential utility of AFLPs, and genetic structure of the hydrothermal vent tubeworm Riftia pachyptila, genomic ‘fingerprints’ were recovered from 29 individuals from five vent fields spanning a distance of up to c. 5000 km along the East Pacific Rise. In contrast to previous population genetic studies that found little to no genetic structure using allozymes and mitochondrial DNA, genetic analyses of 630 polymorphic AFLP loci identified distinct subclades within R. pachyptila populations. Significant levels of differentiation were observed among populations from all vent regions as well as within each region. Discrete assemblages of tubeworms separated by as little as c. 400 m within a given vent region were genetically distinguishable and cohorts (based on size‐frequency distribution) within an aggregation were found to be most closely related. These results suggest that mechanisms of larval dispersal act to retain cohort fidelity in R. pachyptila. 相似文献
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