Stylophora pistillata is a widely used coral “lab-rat” species with highly variable morphology and a broad biogeographic range (Red Sea to western central Pacific). Here we show, by analysing Cytochorme Oxidase I sequences, from 241 samples across this range, that this taxon in fact comprises four deeply divergent clades corresponding to the Pacific-Western Australia, Chagos-Madagascar-South Africa, Gulf of Aden-Zanzibar-Madagascar, and Red Sea-Persian/Arabian Gulf-Kenya. On the basis of the fossil record of Stylophora, these four clades diverged from one another 51.5-29.6 Mya, i.e., long before the closure of the Tethyan connection between the tropical Indo-West Pacific and Atlantic in the early Miocene (16–24 Mya) and should be recognised as four distinct species. These findings have implications for comparative ecological and/or physiological studies carried out using Stylophora pistillata as a model species, and highlight the fact that phenotypic plasticity, thought to be common in scleractinian corals, can mask significant genetic variation.
BackgroundSeawater temperature is the main factor restricting shallow-water zooxanthellate coral reefs to low latitudes. As temperatures increase, coral species and perhaps reefs may move into higher-latitude waters, increasing the chances of coral reef ecosystems surviving despite global warming. However, there is a growing need to understand the structure of these high-latitude coral communities in order to analyze their future dynamics and to detect any potential changes.Methodology/Principal FindingsThe high-latitude (32.75°N) community surveyed was located at Tatsukushi, Shikoku Island, Japan. Coral cover was 60±2% and was composed of 73 scleractinian species partitioned into 7 functional groups. Although only 6% of species belonged to the ‘plate-like’ functional group, it was the major contributor to species coverage. This was explained by the dominance of plate-like species such as Acropora hyacinthus and A. solitaryensis. Comparison with historical data suggests a relatively recent colonization/development of A. hyacinthus in this region and a potential increase in coral diversity over the last century. Low coverage of macroalgae (2% of the benthic cover) contrasted with the low abundance of herbivorous fishes, but may be reasonably explained by the high density of sea urchins (12.9±3.3 individuals m−2).Conclusions/SignificanceThe structure and composition of this benthic community are relatively remarkable for a site where winter temperature can durably fall below the accepted limit for coral reef development. Despite limited functionalities and functional redundancy, the current benthic structure might provide a base upon which a reef could eventually develop, as characterized by opportunistic and pioneer frame-building species. In addition to increasing seawater temperatures, on-going management actions and sea urchin density might also explain the observed state of this community. A focus on such ‘marginal’ communities should be a priority, as they can provide important insights into how tropical corals might cope with environmental changes.
The capacity of corals for repairing partial mortality is a fundamental determinant of reef resilience. This capacity was assessed in the major reef-building coral Porites lutea by monitoring the regeneration of artificially induced lesions of standard size (330 ± 50 mm 2 , 3 mm deep) in 4 shallow reef flat populations at Réunion Island, under different environmental conditions related to sites and seasons, during a period without positive temperature anomalies. An exponential decay model with an asymptote described the lesion regeneration through 14 experiments. In spite of fast initial lesion regeneration, limited capacity for repair in this massive coral was indicated, as only 18% of the inflicted lesions healed completely within 6 to 9 mo. Lesion regeneration was fastest and most complete in the cooling and cool seasons, and may be impaired during the warming and hot seasons. Both solar radiation and seawater temperature contributed to seasonal changes in regeneration capacity, although they had opposite effects. While high radiation during the warming season decreased lesion regeneration rate, potentially through reduction of the photosynthetic efficiency of zooxanthellae, high temperature boosted it but also increased the amount of lesion area that could not be regenerated. Study sites were characterised by different temperature and radiation regimes, but these parameters alone could not explain all site effects on lesion regeneration capacity. Additional factors, most probably chronic stress caused by inputs of organic matter and run-off from land, may further compromise the regeneration capacity of corals and the resilience of coral populations.
The distribution and the structure of benthic assemblages vary with latitude. However, few studies have described benthic communities along large latitudinal gradients, and patterns of variation are not fully understood. Taiwan, lying between 21.90°N and 25.30°N, is located at the center of the Philippine-Japan arc and lies at the northern margin of coral reef development. A wide range of habitats is distributed along this latitudinal gradient, from extensive fringing coral reefs at the southern coast to non-reefal communities at the north. In this study, we examined the structure of benthic communities around Taiwan, by comparing its assemblages in four regions, analyzing the effects of the latitudinal gradient, and highlighting regional characteristics. A total of 25 sites, 125 transects, and 2,625 photographs were used to analyze the benthic communities. Scleractinian corals present an obvious gradient of increasing diversity from north to south, whereas macro-algae diversity is higher on the north-eastern coast. At the country scale, Taiwanese coral communities were dominated by turf algae (49%). At the regional scale, we observed an important heterogeneity that may be caused by local disturbances and habitat degradation that smooths out regional differences. In this context, our observations highlight the importance of managing local stressors responsible for reef degradation. Overall, this study provides an important baseline upon which future changes in benthic assemblages around Taiwan can be assessed.
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