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Weak genetic structure indicates strong dispersal limits: a tale of two coral reef fish.

ABSTRACT: The extent of dispersal by pelagic larvae in marine environments, including coral reefs, is central for understanding local population dynamics and designing sustainable marine reserves. We present here the first example of a clear stepping-stone genetic structure throughout the Caribbean basin for a common coral reef species, the French grunt (Haemulon flavolineatum). Analysis of microsatellite DNA markers indicated that French grunt population structure may be characterized by overlapping populations throughout the Caribbean, influenced by independent population dynamics but with no fixed geographical boundaries. In addition, different spatial genetic patterns were found in different oceanographic regions. A second species, the bluehead wrasse (Thalassoma bifasciatum), has a much longer pelagic larval duration than French grunts and showed no explicit spatial pattern of genetic variation. This finding is concordant with the hypothesis of a positive relationship between larval dispersal and duration in the plankton. While the magnitude of the genetic signal of population structure in French grunts was very low (F(ST) approximately 0.003), the pattern of isolation-by-distance throughout the Caribbean indicated considerable population structure with important ecological and conservation significance.

SUBMITTER: Purcell JF

PROVIDER: S-EPMC1560316 | biostudies-literature | 2006 Jun

REPOSITORIES: biostudies-literature

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Weak genetic structure indicates strong dispersal limits: a tale of two coral reef fish.

Purcell John F H JF Cowen Robert K RK Hughes Colin R CR Williams Dean A DA

Proceedings. Biological sciences 20060601 1593

The extent of dispersal by pelagic larvae in marine environments, including coral reefs, is central for understanding local population dynamics and designing sustainable marine reserves. We present here the first example of a clear stepping-stone genetic structure throughout the Caribbean basin for a common coral reef species, the French grunt (Haemulon flavolineatum). Analysis of microsatellite DNA markers indicated that French grunt population structure may be characterized by overlapping popu ...[more]

PMID: 16777742

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Project description:Coral reefs around the world are rapidly degrading due to a range of environmental stressors. Habitat degradation modifies the sensory landscape within which predator-prey interactions occur, with implications for olfactory-mediated behaviours. Predator naïve settlement-stage damselfish rely on conspecific damage-released odours (i.e., alarm odours) to inform risk assessments. Yet, species such as the Ambon damselfish, Pomacentrus amboinensis, become unable to respond appropriately to these cues when living in dead-degraded coral habitats, leading to increased mortality through loss of vigilance. Reef fish predators also rely on odours from damaged prey to locate, assess prey quality and engage in prey-stealing, but it is unknown whether their responses are also modified by the change to dead-degraded coral habitats. Implications for prey clearly depend on how their predatory counterparts are affected, therefore the present study tested whether olfactory-mediated foraging responses in the dusky dottyback, Pseudochromis fuscus, a common predator of P. amboinensis, were similarly affected by coral degradation. A y-maze was used to measure the ability of Ps. fuscus to detect and move towards odours, against different background water sources. Ps. fuscus were exposed to damage-released odours from juvenile P. amboinensis, or a control cue of seawater, against a background of seawater treated with either healthy or dead-degraded hard coral. Predators exhibited an increased time allocation to the chambers of y-mazes injected with damage-released odours, with comparable levels of response in both healthy and dead-degraded coral treated waters. In control treatments, where damage-released odours were replaced with a control seawater cue, fish showed no increased preference for either chamber of the y-maze. Our results suggest that olfactory-mediated foraging behaviours may persist in Ps. fuscus within dead-degraded coral habitats. Ps. fuscus may consequently gain a sensory advantage over P. amboinensis, potentially altering the outcome of predator-prey interactions.

Project description:Transcriptional profiling of gene responses in liver in the coral reef fish Pomacentrus moluccensis in response to different types of environmental stress: cold, heat, hypoxic and hyposmotic shock. Goal was to determine the common effects of different types of environmental stress on gene expression as well as responses unique to different stressors. Abstract from Kassahn et al. BMC Genomics (2007) 8:358 Background While our understanding of the importance of transcriptional regulation for biological function is continuously growing, we still know comparatively little about how environmentally-induced stress affects gene expression in vertebrates and how consistent transcriptional stress responses are across different types of environmental stress. Results In this study, we looked for a genetic measure of environmental stress and used a multi-stressor approach to identify components of a common stress response as well as components unique to different types of environmental stress. We exposed individuals of the coral reef fish Pomacentrus moluccensis to hypoxic, hyposmotic, cold and heat shock and measured the responses of approximately 16,000 genes in liver. We also compared winter and summer responses to heat shock to examine the capacity for such responses to vary with acclimation to different ambient temperatures. We identified a series of gene functions that were consistently involved in all stress responses examined here, suggesting common effects of stress on biological function. These common responses were achieved by the regulation of largely independent sets of genes and the responses of individual genes varied greatly across different stress types. However, we were able to identify groups of co-regulated genes, the genes within which shared similar functions. Given current estimates of climatic change, we were particularly interested in the response to prolonged heat exposure. In total, 324 gene loci were differentially expressed following exposure to heat over five days. The functions of these heat-responsive genes suggest that prolonged heat stress leads to oxidative stress and protein damage, challenge of the immune system, and a re-allocation of energy sources. Conclusion 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. This study 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. Keywords: Stress response

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Weak genetic structure indicates strong dispersal limits: a tale of two coral reef fish.

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Weak genetic structure indicates strong dispersal limits: a tale of two coral reef fish.

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