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Coral Populations (coral + population)
Selected AbstractsLong-standing environmental conditions, geographic isolation and host,symbiont specificity influence the relative ecological dominance and genetic diversification of coral endosymbionts in the genus SymbiodiniumJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Todd C. LaJeunesse Abstract Aim, This study examines the importance of geographic proximity, host life history and regional and local differences in environment (temperature and water clarity) in driving the ecological and evolutionary processes underpinning the global patterns of diversity and distribution of symbiotic dinoflagellates. By comparing and contrasting coral,algal symbioses from isolated regions with differing environmental conditions, we may assess the potential of coral communities to respond to significant changes in climate. Location, Indian Ocean. Methods, Community assemblages of obligate symbiotic invertebrates were sampled at numerous sites from two regions, the north-eastern Indian Ocean (Andaman Sea, western Thailand) and the western Indian Ocean (Zanzibar, Tanzania). Molecular genetic methods, including denaturing gradient gel electrophoresis analysis of the ribosomal internal transcribed spacers, DNA sequencing and microsatellite genotyping, were used to characterize the ,species' diversity and evolutionary relationships of symbiotic dinoflagellates (genus Symbiodinium). Host,symbiont specificity, geographic isolation and local and regional environmental factors were evaluated in terms of their importance in governing the distribution and prevalence of certain symbiont taxa. Results, Host-generalist symbionts (C3u and D1-4, formerly D1a now designated Symbiodinium trenchi) frequently occurred alone and sometimes together in hosts with horizontal modes of symbiont acquisition. However, the majority of Symbiodinium diversity consisted of apparently host-specific ,species'. Clade C Symbiodinium were diverse and dominated host assemblages from sites sampled in the western Indian Ocean, a pattern analogous to symbiont communities on the Great Barrier Reef with similar environmental conditions. Clade D Symbiodinium were diverse and occurred frequently in hosts from the north-eastern Indian Ocean, especially at inshore locations, where temperatures are warmer, water turbidity is high and large tidal exchanges commonly expose coral populations to aerial desiccation. Main conclusions, Regional and local differences in cnidarian,algal combinations indicate that these symbioses are ecologically and evolutionarily responsive and can thrive under various environmental conditions. The high temperatures and turbid conditions of the north-eastern Indian Ocean partly explain the ecological success of Clade D Symbiodinium relative to Clade C. Phylogenetic, ecological and population genetic data further indicate that Clade D has undergone an adaptive radiation, especially in regions around Southeast Asia, during the Pleistocene. [source] Conflicting estimates of connectivity among deep-sea coral populationsMARINE ECOLOGY, Issue 2010Karen Miller Abstract Genetic data were used as an indirect means of assessing connectivity among deep-sea coral populations on seamounts and slopes in the Australian and New Zealand region. We sequenced three DNA regions (16S, ITS and Control Region) in nine deep-sea coral species from sites spanning thousands of kilometers. Based on haplotype distributions and AMOVA, we found evidence of genetic subdivision across ocean expanses for three species: the scleractinian Desmophyllum dianthus, and the antipatharians Antipathes robillardi and Stichopathes variabilis. Levels of genetic variation were low for the remaining species, including the reef-forming Solenosmila variablis and Madrepora oculata, and more sensitive molecular markers may be needed to resolve their spatial structure properly. For two species (the scleractinian Stephanocyathus spiniger and the antipatharian Stichopathes filiformis), we found no evidence of genetic subdivision among sites within regions, suggesting sufficient gene flow occurs to maintain genetic homogeneity at scales of tens to hundreds of kilometers. Recognising that some seamount regions and coral populations are, or are not, effectively isolated will be a key component of successful management planning based on marine protected area networks , both within and beyond national jurisdictions. [source] A restoration genetics guide for coral reef conservationMOLECULAR ECOLOGY, Issue 12 2008ILIANA B. BAUMS Abstract Worldwide degradation of coral reef communities has prompted a surge in restoration efforts. They proceed largely without considering genetic factors because traditionally, coral populations have been regarded as open over large areas with little potential for local adaptation. Since, biophysical and molecular studies indicated that most populations are closed over shorter time and smaller spatial scales. Thus, it is justified to re-examine the potential for site adaptation in corals. There is ample evidence for differentiated populations, inbreeding, asexual reproduction and the occurrence of ecotypes, factors that may facilitate local adaptation. Discovery of widespread local adaptation would influence coral restoration projects mainly with regard to the physical and evolutionary distance from the source wild and/or captive bred propagules may be moved without causing a loss of fitness in the restored population. Proposed causes for loss of fitness as a result of (plant) restoration efforts include founder effects, genetic swamping, inbreeding and/or outbreeding depression. Direct evidence for any of these processes is scarce in reef corals due to a lack of model species that allow for testing over multiple generations and the separation of the relative contributions of algal symbionts and their coral hosts to the overall performance of the coral colony. This gap in our knowledge may be closed by employing novel population genetic and genomics approaches. The use of molecular tools may aid managers in the selection of appropriate propagule sources, guide spatial arrangement of transplants, and help in assessing the success of coral restoration projects by tracking the performance of transplants, thereby generating important data for future coral reef conservation and restoration projects. [source] Coral community decline at a remote Caribbean island: marine no-take reserves are not enoughAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2007Vānia R. Coelho Abstract 1.Coral reefs around the world have been deteriorating over decades owing to anthropogenic pressure. In the Caribbean recent rates of decline are alarming, particularly for coral reefs under high local human impact, many of which are severely degraded, although regions with lower direct anthropogenic influence seem less affected. 2.Little Cayman is a relatively undeveloped island, with less than 150 permanent residents. About 20% of its reefs have been protected by no-take marine reserves since the mid-1980s. We analysed the dynamics of coral communities around the island from 1999 to 2004 in order to test the hypothesis that a lack of major local anthropogenic disturbances is enough to prevent decline of coral populations. 3.Live hard coral coverage, coral diversity, abundance, mortality, size, and prevalence of disease and bleaching were measured using the Atlantic and Gulf Rapid Reef Assessment methodology (line transects) at nine sites. Despite the apparent undisturbed condition of the island, a 40% relative reduction of mean live coral coverage (from 26% to 16%, absolute change was 10%) was recorded in five years. Mean mortality varied from year to year from 23% to 27%. Overall mean diameter and height have decreased between 6% and 15% on average (from 47 to 40 cm for diameter, and from 31 to 29 cm for height). 4.The relative abundance of large reef builders of the genus Montastraea decreased, while that of smaller corals of the genera Agaricia and Porites increased. Disease prevalence has increased over time, and at least one relatively large bleaching event (affecting 10% of the corals) took place in 2003. 5.Mean live coral cover decline was similar inside (from 29% to 19%) and outside (from 24% to 14%) marine no-take reserves. No significant difference in disease prevalence or clear pattern in bleaching frequency was observed between protected and non-protected areas. It is concluded that more comprehensive management strategies are needed in order to effectively protect coral communities from degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Applying forest restoration principles to coral reef rehabilitationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2003N. Epstein Abstract 1.Forest restoration through silviculture (gardening) programs revives productivity, biodiversity, and stability. As in silviculture approaches, the coral ,gardening' strategy is based on a two-step protocol. 2.The first step deals with the establishment of in situ and/or ex situ coral nurseries in which corals are farmed (originating from two types of source material: asexual [ramets, nubbins], and sexual [planula larvae, spat] recruits). 3.The second is the reef rehabilitation step, where maricultured colonies are transplanted into degraded sites. 4.We compare here the rationale of forest restoration to coral reef ecosystem restoration by evaluating major key criteria. As in silviculture programs, a sustainable mariculture operation that focuses on the prime structural component of the reef (,gardening' with corals) may promote the persistence of threatened coral populations, as well as that of other reef taxa, thus maintaining genetic diversity. In chronically degrading reef sites this may facilitate a halt in biodiversity depletion. 5.Within the current theoretical framework of ecosystem restoration, the recovery of biodiversity indices is considered a core element since a rich species diversity provides higher ecosystem resilience to disturbances. 6.The gardening measure may also be implemented worldwide, eliminating the need to extract existing colonies for transplantation operations. At degraded reef sites, the coral gardening strategy can assist in managing human and non-human stakeholders' requirements as is done in forest management. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||