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Marine Populations (marine + population)
Selected AbstractsA developmental bottleneck in dispersing larvae: implications for spatial population dynamicsECOLOGY LETTERS, Issue 4 2003Daniel W. Schneider Abstract We found evidence for a critical population bottleneck at a developmental-stage transition in larvae of the zebra mussel Dreissena polymorpha Pallas from field estimates of mortality. Identification of this critical period in the field was made possible by closely tracking cohorts of larvae over 5 days of development as they dispersed 128 km in a river system. The presence of a survival bottleneck during development was confirmed in laboratory studies of zebra mussel larvae. Development-specific mortality has important implications for spatial population dynamics of the zebra mussel in particular, and all species with indirect development in general. Marine reserves that do not take development-specific mortality into account may dramatically underestimate reserve size needed to protect rare and/or exploited marine populations. Conversely, for the zebra mussel, the lower contribution of dispersing individuals to population growth downstream of reserves can lead to more feasible control through the blocking of dispersal. [source] Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful factsFISH AND FISHERIES, Issue 4 2008Lorenz Hauser Abstract By providing new approaches to the investigation of demographic and evolutionary dynamics of wild populations, molecular genetics has led to fundamental changes in our understanding of marine ecology. In particular, genetic approaches have revolutionized our understanding in three areas: (i) most importantly, they have contributed to the discovery of extensive genetic population structure in many marine species, overturning the notion of large, essentially homogenous marine populations limiting local adaptation and speciation. (ii) Concomitant differences in ecologically important traits now indicate extensive adaptive differentiation and biocomplexity, potentially increasing the resilience to exploitation and disturbance. Evidence for rapid adaptive change in many populations underlies recent concerns about fisheries-induced evolution affecting life-history traits. (iii) A compilation of recent published research shows estimated effective population sizes that are 2,6 orders of magnitude smaller than census sizes, suggesting more complex recruitment dynamics in marine species than previously assumed. Studies on Atlantic cod are used to illustrate these paradigm shifts. In our synthesis, we emphasize the implications of these discoveries for marine ecology and evolution as well as the management and conservation of exploited marine fish populations. An important implication of genetic structuring and the potential for adaptive divergence is that locally adapted populations are unlikely to be replaced through immigration, with potentially detrimental consequences for the resilience to environmental change , a key consideration for sustainable fisheries management. [source] Seascape genetics and the spatial ecology of marine populationsFISH AND FISHERIES, Issue 4 2008Kimberly A Selkoe Abstract Molecular tools perform at their best when integrated with other data and approaches. The value of integrating approaches is especially high when the underlying genetic signal is relatively weak, as occurs in many marine species. Recently, studies combining genetic, oceanographic, behavioural and modelling approaches have provided new insights into the spatial ecology of marine populations, in particular regarding larval migration, barriers to dispersal and source-sink population dynamics. In this perspectives piece, we explore the advantages of a multidisciplinary approach to marine population genetics by (i) providing a synthesis of what has been learned about connectivity from studies that combine genetic data with other tools, (ii) discussing how incorporation of ecological and oceanographic information into alternative hypotheses can boost inference when genetic power is low, and (iii) summarizing recent innovations in statistical population genetics that enable seamless integration of ecological, environmental and genetic data. These topics are covered in the context of how genetic inferences of connectivity and dispersal can contribute to pressing questions facing marine conservation and management. [source] Extinction vulnerability in marine populationsFISH AND FISHERIES, Issue 1 2003Nicholas K Dulvy Abstract Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53-year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low-detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large-scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non-target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species. [source] Myths and moderation in marine ,metapopulations'?FISH AND FISHERIES, Issue 1 2002R Kent Smedbol Abstract The metapopulation concept is appearing with increasing frequency in the marine population dynamics and genetics literature, though its applicability to marine systems remains an open question. Moreover, in recent years, the meaning of the term ,metapopulation' has become blurred, concomitant with its increasing use. In this paper, we summarize the concept of metapopulation dynamics and the associated theoretical assumptions. We call for a stricter definition and use of the term ,metapopulation', critically evaluate the applicability of metapopulation theory to marine population dynamics and its use in the related literature, and consider two published case-studies that investigate metapopulation structuring in specific marine populations. Finally, we urge scientists to carefully articulate what is meant by the term ,metapopulation' and to use appropriate citations in the primary literature to circumvent the potential for nebulous (and possibly damaging) conclusions in the future. [source] The importance of episodic weather events to the ecosystem of the Bering Sea shelfFISHERIES OCEANOGRAPHY, Issue 2 2005NICHOLAS A. BOND Abstract Climate variability on decadal time scales is generally recognized to influence high-latitude marine populations. Our recent work in studying air,sea interactions in the Bering Sea suggests that interannual to decadal climate variability is important through its modulation of the frequencies and magnitudes of weather events on intraseasonal time scales. We hypothesize that it is these weather events that directly impact the marine ecosystem of the Bering Sea shelf. The linkages between the event-scale weather and the ecosystem are illustrated with three examples: walleye pollock (Theragra chalcogramma), Tanner crabs (Chionoecetes bairdi), and coccolithophorid phytoplankton (Emiliania huxleyi). We hypothesize that the strong recruitment of walleye pollock that occurred in 1978, 1982, and 1996 can be attributed in part due to the seasonably strong storms that occurred in the early summer of those years. These storms caused greater than normal mixing of nutrients into the euphotic zone which presumably led to sustained primary productivity after the spring bloom and, possibly, enhanced prey concentrations for pollock larvae and their competitors. Recruitment of Tanner crab was particularly strong for the 1981 and 1984 year-classes. These years had periods of prominent east wind anomalies along the Alaska Peninsula during the previous winter. Such winds promote flow through Unimak Pass, and hence an enhanced flux of nutrient-rich water onto the shelf. This mechanism may have ultimately resulted in favorable feeding conditions for Tanner crab larvae. Finally, an unprecedented coccolithophorid bloom occurred over the Bering Sea shelf in the summer of 1997. This summer featured lighter winds and greater insolation than usual after a spring that included a very strong May storm. This combination brought about a warm, nutrient-poor upper mixed layer by mid-summer. This provided a competitive advantage for coccolithophorid phytoplankton in 1997 and to a lesser extent in 1998. Unusually high concentrations of coccolithophores persisted for the following two years although physical environmental conditions did not remain favorable. While slow variations in the overall aspects of the physical environment may be important for setting the stage, we propose that the significant multi-year adjustments in the marine ecosystem of the Bering Sea shelf are more directly caused by major air,sea interaction events on intraseasonal time scales. [source] Seascape genetics along a steep cline: using genetic patterns to test predictions of marine larval dispersalMOLECULAR ECOLOGY, Issue 17 2010HEATHER M. GALINDO Abstract Coupled biological and physical oceanographic models are powerful tools for studying connectivity among marine populations because they simulate the movement of larvae based on ocean currents and larval characteristics. However, while the models themselves have been parameterized and verified with physical empirical data, the simulated patterns of connectivity have rarely been compared to field observations. We demonstrate a framework for testing biological-physical oceanographic models by using them to generate simulated spatial genetic patterns through a simple population genetic model, and then testing these predictions with empirical genetic data. Both agreement and mismatches between predicted and observed genetic patterns can provide insights into mechanisms influencing larval connectivity in the coastal ocean. We use a high-resolution ROMS-CoSINE biological-physical model for Monterey Bay, California specifically modified to simulate dispersal of the acorn barnacle, Balanus glandula. Predicted spatial genetic patterns generated from both seasonal and annual connectivity matrices did not match an observed genetic cline in this species at either a mitochondrial or nuclear gene. However, information from this mismatch generated hypotheses testable with our modelling framework that including natural selection, larval input from a southern direction and/or increased nearshore larval retention might provide a better fit between predicted and observed patterns. Indeed, moderate selection and a range of combined larval retention and southern input values dramatically improve the fit between simulated and observed spatial genetic patterns. Our results suggest that integrating population genetic models with coupled biological-physical oceanographic models can provide new insights and a new means of verifying model predictions. [source] Long-distance dispersal and local retention of larvae as mechanisms of recruitment in an island population of a coral reef fishAUSTRAL ECOLOGY, Issue 2 2007HEATHER M. PATTERSON Abstract Although recruitment of pelagic larvae is a fundamental and well-documented process in the dynamics of benthic marine populations, identifying the sources of recruitment, or the degree to which populations are connected via dispersal of larvae, has remained elusive for most marine taxa. In this study we used natural environmental markers (trace elements) recorded in fish otoliths (ear stones) as tags of natal origin. Specifically, we used the otolith core and edge chemistries of a locally endemic wrasse (Coris bulbifrons) from Lord Howe Island (LHI), Australia, and a widely distributed species (Coris picta) from three potential mainland source regions, to determine the likely sources of recruitment to C. picta populations on LHI. The use of a local endemic species, which is by definition self-recruiting, is a novel approach for ground-truthing the dispersal history of non-endemic coral reef fish. Discriminant function analyses were able to separate LHI from mainland fish, using both edge and core signatures, with a high degree of accuracy, suggesting at least some of the C. picta collected on LHI were of local origin. This result was corroborated when half of the C. bulbifrons and LHI C. picta were introduced as unknowns into a discriminant function analysis using the remaining C. bulbifrons, LHI C. picta, and the mainland C. picta as a training data set. Overall, our findings suggest that both long distance dispersal and local retention are important sources of recruitment to populations of C. picta on LHI and that otolith chemistry of endemic species could be a useful benchmark for determining the prevalence of self-recruitment in insular populations of other widespread species. [source] | |||||||||||||