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Search Results: 1 - 10 of 402872 matches for " M Julian Caley "
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Greater Genetic Diversity in Spatially Restricted Coral?Reef Fishes Suggests Secondary Contact among Differentiated Lineages
Line K. Bay,M. Julian Caley
Diversity , 2011, DOI: 10.3390/d3030483
Abstract: The maintenance of genetic diversity is a central goal of conservation. It is the raw material for evolutionary change and if lost, can accelerate extinction of species. According to theory, total genetic diversity should be less in species with restricted ranges and in populations on the margins of distributional ranges, making such species or populations more vulnerable to environmental perturbations. Using mtDNA and nuclear Inter Simple Sequence Repeat (ISSR) data we investigated how the genetic diversity and structure of three con-generic species pairs of coral reef fishes (Pomacentridae) was related to species’ range size and position of populations within these ranges. Estimates of genetic structure did not differ significantly among species, but mtDNA and nucDNA genetic diversities were up to 10 times greater in spatially restricted species compared to their widespread congeners. In two of the three species pairs, the distribution of genetic variation indicated secondary contact among differentiated lineages in the spatially restricted species. In contrast, the widespread species displayed a typical signature of population expansion suggesting recent genetic bottlenecks, possibly associated with the (re) colonization of the Great Barrier Reef. These results indicate that historical processes, involving hybridization and founder effects, possibly associated with Pleistocene sea level fluctuations, have differentially influenced the widespread and spatially restricted coral reef damselfish species studied here.
The Diversity of Coral Reefs: What Are We Missing?
Laetitia Plaisance, M. Julian Caley, Russell E. Brainard, Nancy Knowlton
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025026
Abstract: Tropical reefs shelter one quarter to one third of all marine species but one third of the coral species that construct reefs are now at risk of extinction. Because traditional methods for assessing reef diversity are extremely time consuming, taxonomic expertise for many groups is lacking, and marine organisms are thought to be less vulnerable to extinction, most discussions of reef conservation focus on maintenance of ecosystem services rather than biodiversity loss. In this study involving the three major oceans with reef growth, we provide new biodiversity estimates based on quantitative sampling and DNA barcoding. We focus on crustaceans, which are the second most diverse group of marine metazoans. We show exceptionally high numbers of crustacean species associated with coral reefs relative to sampling effort (525 species from a combined, globally distributed sample area of 6.3 m2). The high prevalence of rare species (38% encountered only once), the low level of spatial overlap (81% found in only one locality) and the biogeographic patterns of diversity detected (Indo-West Pacific>Central Pacific>Caribbean) are consistent with results from traditional survey methods, making this approach a reliable and efficient method for assessing and monitoring biodiversity. The finding of such large numbers of species in a small total area suggests that coral reef diversity is seriously under-detected using traditional survey methods, and by implication, underestimated.
Plasticity of Noddy Parents and Offspring to Sea-Surface Temperature Anomalies
Carol A. Devney,M. Julian Caley,Bradley C. Congdon
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011891
Abstract: Behavioral and/or developmental plasticity is crucial for resisting the impacts of environmental stressors. We investigated the plasticity of adult foraging behavior and chick development in an offshore foraging seabird, the black noddy (Anous minutus), during two breeding seasons. The first season had anomalously high sea-surface temperatures and ‘low’ prey availability, while the second was a season of below average sea-surface temperatures and ‘normal’ food availability. During the second season, supplementary feeding of chicks was used to manipulate offspring nutritional status in order to mimic conditions of high prey availability. When sea-surface temperatures were hotter than average, provisioning rates were significantly and negatively impacted at the day-to-day scale. Adults fed chicks during this low-food season smaller meals but at the same rate as chicks in the unfed treatment the following season. Supplementary feeding of chicks during the second season also resulted in delivery of smaller meals by adults, but did not influence feeding rate. Chick begging and parental responses to cessation of food supplementation suggested smaller meals fed to artificially supplemented chicks resulted from a decrease in chick demands associated with satiation, rather than adult behavioral responses to chick condition. During periods of low prey abundance, chicks maintained structural growth while sacrificing body condition and were unable to take advantage of periods of high prey abundance by increasing growth rates. These results suggest that this species expresses limited plasticity in provisioning behavior and offspring development. Consequently, responses to future changes in sea-surface temperature and other environmental variation may be limited.
Differences among Major Taxa in the Extent of Ecological Knowledge across Four Major Ecosystems
Rebecca Fisher, Nancy Knowlton, Russell E. Brainard, M. Julian Caley
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026556
Abstract: Existing knowledge shapes our understanding of ecosystems and is critical for ecosystem-based management of the world's natural resources. Typically this knowledge is biased among taxa, with some taxa far better studied than others, but the extent of this bias is poorly known. In conjunction with the publically available World Registry of Marine Species database (WoRMS) and one of the world's premier electronic scientific literature databases (Web of Science?), a text mining approach is used to examine the distribution of existing ecological knowledge among taxa in coral reef, mangrove, seagrass and kelp bed ecosystems. We found that for each of these ecosystems, most research has been limited to a few groups of organisms. While this bias clearly reflects the perceived importance of some taxa as commercially or ecologically valuable, the relative lack of research of other taxonomic groups highlights the problem that some key taxa and associated ecosystem processes they affect may be poorly understood or completely ignored. The approach outlined here could be applied to any type of ecosystem for analyzing previous research effort and identifying knowledge gaps in order to improve ecosystem-based conservation and management.
Using DNA Barcoding and Standardized Sampling to Compare Geographic and Habitat Differentiation of Crustaceans: A Hawaiian Islands Example
Laetitia Plaisance,Russell Brainard,M. Julian Caley,Nancy Knowlton
Diversity , 2011, DOI: 10.3390/d3040581
Abstract: Recently, the Census of Marine Life has explored methods to assess coral reef diversity by combining standardized sampling (to permit comparison across sites) with molecular techniques (to make rapid counts of species possible). To date, this approach has been applied across geographically broad scales (seven sites spanning the Indian, Pacific and Atlantic Oceans), focusing on similar habitats at all sites (10–12 m forereef). Here we examine crustacean spatial diversity patterns for a single atoll, comparing results for four sites (comprising forereef, backreef, and lagoon habitats) at French Frigate Shoals (FFS), Northwestern Hawaiian Islands, Hawaii, USA, within the Papahanaumokuakea Marine National Monument. The Bray-Curtis index of similarity across these habitats at FFS was the same or greater than the similarity between similar habitats on Heron Island and Lizard Island in the Great Barrier Reef and much greater than similarity between more widely separated localities in the Indo-Pacific Ocean (e.g., Ningaloo, Moorea, French Polynesia or the Line Islands). These results imply that, at least for shallow reefs, sampling multiple locations versus sampling multiple habitats within a site maximizes the rate at which we can converge on the best global estimate of coral reef biodiversity.
Meta-population structure in a coral reef fish demonstrated by genetic data on patterns of migration, extinction and re-colonisation
Line K Bay, M Julian Caley, Ross H Crozier
BMC Evolutionary Biology , 2008, DOI: 10.1186/1471-2148-8-248
Abstract: Acanthochromis polyacanthus displayed strong genetic structure among regions (ΦST = 0.81, P < 0.0001) that supported an equilibrium isolation-by-distance model (r = 0.77, P = 0.001). Significant structuring across the continental shelf was only evident in the northern region (ΦST = 0.31, P < 0.001) and no evidence of isolation-by-distance was found within any region. Pairwise ΦST values indicated overall strong but variable genetic structure (mean ΦST among reefs within regions = 0.28, 0.38, 0.41), and asymmetric migration rates among reefs with low genetic structure. Genetic differentiation among younger reefs was greater than among older reefs supporting a meta-population propagule-pool colonisation model. Variation in genetic diversities, demographic expansion and population growth estimates indicated more frequent genetic bottlenecks/founder effects and subsequent population expansion in the central and southern regions compared to the northern one.Our findings provide genetic evidence for meta-population dynamics in a direct developing coral reef fish and we reject the equilibrium island and isolation-by distance models at local spatial scales. Instead, strong non-equilibrium genetic structure appears to be generated by genetic bottlenecks/founder effects associated with population reductions/extinctions and asymmetric migration/(re)-colonisation of such populations. These meta-population dynamics varied across the geographical range examined with edge populations exhibiting lower genetic diversities and higher rates of population expansion than more central populations. Therefore, coral reef species may experience local population reductions/extinctions that promote overall meta-population genetic differentiation.Coral reefs are important ecosystems in ecological, evolutionary and socio-economic contexts but are under increasing threat from anthropogenic impacts [1,2]. The most effective conservation tool available to coral reef managers so far has been the us
From transcriptome to biological function: environmental stress in an ectothermic vertebrate, the coral reef fish Pomacentrus moluccensis
Karin S Kassahn, Ross H Crozier, Alister C Ward, Glenn Stone, M Julian Caley
BMC Genomics , 2007, DOI: 10.1186/1471-2164-8-358
Abstract: We identified a series of gene functions that were involved in all stress responses examined here, suggesting some common effects of stress on biological function. These common responses were achieved by the regulation of largely independent sets of genes; the responses of individual genes varied greatly across different stress types. In response to heat exposure over five days, a total of 324 gene loci were differentially expressed. Many heat-responsive genes had functions associated with protein turnover, metabolism, and the response to oxidative stress. We were also able to identify groups of co-regulated genes, the genes within which shared similar functions.This is the first environmental genomic study to measure gene regulation in response to different environmental stressors in a natural population of a warm-adapted ectothermic vertebrate. We have shown that different types of environmental stress induce expression changes in genes with similar gene functions, but that the responses of individual genes vary between stress types. The functions of heat-responsive genes suggest that prolonged heat exposure leads to oxidative stress and protein damage, a challenge of the immune system, and the re-allocation of energy sources. This study hence offers insight into the effects of environmental stress on biological function and sheds light on the expected sensitivity of coral reef fishes to elevated temperatures in the future.Microarray technology provides a powerful tool for investigating gene regulation and its significance for biological function. However, our understanding of such relationships during environmental stress remains fragmentary, especially in vertebrates. In particular, the commonality, or otherwise, of the responses of vertebrates to different environmental stresses remain poorly understood. Recently, some understanding of responses to individual stresses, in particular those related to thermal stress in teleost fishes, has been gained. In these sp
Development and Validation of Computational Fluid Dynamics Models for Prediction of Heat Transfer and Thermal Microenvironments of Corals
Robert H. Ong, Andrew J. C. King, Benjamin J. Mullins, Timothy F. Cooper, M. Julian Caley
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037842
Abstract: We present Computational Fluid Dynamics (CFD) models of the coupled dynamics of water flow, heat transfer and irradiance in and around corals to predict temperatures experienced by corals. These models were validated against controlled laboratory experiments, under constant and transient irradiance, for hemispherical and branching corals. Our CFD models agree very well with experimental studies. A linear relationship between irradiance and coral surface warming was evident in both the simulation and experimental result agreeing with heat transfer theory. However, CFD models for the steady state simulation produced a better fit to the linear relationship than the experimental data, likely due to experimental error in the empirical measurements. The consistency of our modelling results with experimental observations demonstrates the applicability of CFD simulations, such as the models developed here, to coral bleaching studies. A study of the influence of coral skeletal porosity and skeletal bulk density on surface warming was also undertaken, demonstrating boundary layer behaviour, and interstitial flow magnitude and temperature profiles in coral cross sections. Our models compliment recent studies showing systematic changes in these parameters in some coral colonies and have utility in the prediction of coral bleaching.
δ18O water isotope in the iLOVECLIM model (version 1.0) – Part 3: A paleoperspective based on present-day data-model comparison for oxygen stable isotopes in carbonates
T. Caley,D. M. Roche
Geoscientific Model Development Discussions , 2013, DOI: 10.5194/gmdd-6-1527-2013
Abstract: Oxygen stable isotopes (18O) are among the most usual tools in paleoclimatology/paleoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM allowing fully coupled atmosphere-ocean simulations. In this study, we present the validation of the model results for present day climate against global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite 18O signal of speleothems for a data-model comparison exercise. On the contrary, the reconstructed surface ocean calcite δ18O signal in iLOVECLIM does show a very good agreement with late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil δ18O signal recorded in foraminifer shells and that depth habitat and seasonality play a role but have secondary importance. We argue that a data-model comparison for surface ocean calcite δ18O in past climate, such as the last glacial maximum (≈21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.
δ18O water isotope in the iLOVECLIM model (version 1.0) – Part 2: Evaluation of model results against observed δ18O in water samples
D. M. Roche,T. Caley
Geoscientific Model Development Discussions , 2013, DOI: 10.5194/gmdd-6-1495-2013
Abstract: The H218O stable isotope was previously introduced in the three coupled components of the Earth System Model iLOVECLIM: atmosphere, ocean and vegetation. The results of a long (5000 yr) pre-industrial equilibrium simulation are presented and evaluated against measurement of H218O abundance in present-day water for the atmospheric and oceanic components. For the atmosphere, it is found that the model reproduces the observed spatial distribution and relationships to climate variables with some merit, though limitations following our approach are highlighted. Indeed, we obtain the main gradients with a robust representation of the Rayleigh distillation but caveats appear in Antarctica and around the Mediterranean region due to model limitation. For the oceanic component, the agreement between the modelled and observed distribution of water δ18O is found to be very good. Mean ocean surface latitudinal gradients are faithfully reproduced as well as the mark of the main intermediate and deep water masses. This opens large prospects for the applications in paleoclimatic context.
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