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Threatened Habitat (threatened + habitat)
Selected AbstractsModelling the distribution of a threatened habitat: the California sage scrubJOURNAL OF BIOGEOGRAPHY, Issue 11 2009Erin C. Riordan Abstract Aim, Using predictive species distribution and ecological niche modelling our objectives are: (1) to identify important climatic drivers of distribution at regional scales of a locally complex and dynamic system , California sage scrub; (2) to map suitable sage scrub habitat in California; and (3) to distinguish between bioclimatic niches of floristic groups within sage scrub to assess the conservation significance of analysing such species groups. Location, Coastal mediterranean-type shrublands of southern and central California. Methods, Using point localities from georeferenced herbarium records, we modelled the potential distribution and bioclimatic envelopes of 14 characteristic sage scrub species and three floristic groups (south-coastal, coastal,interior disjunct and broadly distributed species) based upon current climate conditions. Maxent was used to map climatically suitable habitat, while principal components analysis followed by canonical discriminant analysis were used to distinguish between floristic groups and visualize species and group distributions in multivariate ecological space. Results, Geographical distribution patterns of individual species were mirrored in the habitat suitability maps of floristic groups, notably the disjunct distribution of the coastal,interior species. Overlap in the distributions of floristic groups was evident in both geographical and multivariate niche space; however, discriminant analysis confirmed the separability of floristic groups based on bioclimatic variables. Higher performance of floristic group models compared with sage scrub as a whole suggests that groups have differing climate requirements for habitat suitability at regional scales and that breaking sage scrub into floristic groups improves the discrimination between climatically suitable and unsuitable habitat. Main conclusions, The finding that presence-only data and climatic variables can produce useful information on habitat suitability of California sage scrub species and floristic groups at a regional scale has important implications for ongoing efforts of habitat restoration for sage scrub. In addition, modelling at a group level provides important information about the differences in climatic niches within California sage scrub. Finally, the high performance of our floristic group models highlights the potential a community-level modelling approach holds for investigating plant distribution patterns. [source] Endemicity of Afromontane grasshopper assemblages: implications for grassland conservationAFRICAN JOURNAL OF ECOLOGY, Issue 4 2002S. H. Foord Abstract The Drakensberg escarpment in southern Africa is extensively afforested with pine plantations. The Afromontane grasslands in this area have large numbers of endemic plant taxa, but very little is known of their invertebrate fauna. We report on the microgeographical and broad-scale geographical characteristics of grasshoppers and their allies (Orthoptera) at the Groenvaly grassland fragmentation experiment site, South Africa. Pre-fragmentation sampling indicates that control sites and experimental fragments were comparable at the start of the experiment. Of the surveyed species (total 31 species) 25% are endemic to this grassland with another 33% occurring more widely in montane grasslands of south-eastern South Africa. The level of orthopteran endemicity is therefore similar to that of plants, emphasizing the conservation importance of this threatened habitat. There was a significant inverse relation between the degree of stenotopy of a species within the study site and its geographical range in southern Africa, with implications for interpreting the conservation importance of taxonomically and geographically unknown taxa such as the beetles (Coleoptera) in the Afromontane grassland. This information on endemicity of the Afromontane Orthoptera indicates that these grasslands harbour a diverse endemic fauna representing a significant part of southern African biodiversity. Résumé L'escarpement du Drakensberg, en Afrique australe, est largement couvert de plantations de pins. Les prairies afro-montagnardes de cette région comptent un grand nombre de taxons végétaux endémiques, mais on sait très peu de choses de leur faune d'invertébrés. Notre rapport porte sur les caractéristiques micro-géographiques et celles d'une plus grande échelle géographique des sauterelles et de leurs cousins (Orthoptères), sur le site expérimental de fragmentation des prairies de Groenvaly, en Afrique du Sud. L'échantillonnage pré-fragmentation indique que les sites de contrôle et les fragments expérimentaux étaient comparables au début de l'expérience. Des espèces étudiées (31 au total), 25% sont endémiques à cette prairie, tandis que 33 autres pour cent se rencontrent plus largement dans les prairies de montagne, au sud-est de l'Afrique du Sud. Le taux d'endémisme des orthoptères est dès lors semblable à celui des plantes, soulignant davantage l'importance de la conservation de cet habitat menacé. Il y avait une relation inverse significative entre le degré de sténotypie d'une espèce au sein du site étudié et sa distribution géographique en Afrique australe, ce qui a une incidence sur l'interprétation de l'importance de la conservation de taxons géographiquement et taxonomiquement inconnus comme les coléoptères (Coleoptera) de la prairie afro-montagnarde. Ces informations sur l'endémisme des Orthoptères afro-montagnards indiquent que ces prairies abritent une faune endémique variée qui représente une partie significative de la biodiversité de l'Afrique australe. [source] Determinants of floristic diversity and vegetation composition on the islands of Lake Burollos, EgyptAPPLIED VEGETATION SCIENCE, Issue 2 2000Abdel-Hamid Khedr Täckholm 1974; Boulos 1995 Abstract. A floristic and environmental survey was carried out on 22 uninhabited islands (0.1-8.4 ha) in Lake Burollos, Egypt. A total of 58 vascular plant species was recorded. The number of habitats on each island was counted. There was a positive correlation between island area and number of habitat types. Island area was significantly positively correlated with various measures of floristic diversity, including the total number of species present, and the numbers of annual, herbaceous, and shrublet species. Perennial and shrub species numbers did not differ significantly with island area. In addition to island area, elevation and soil salinity, as well as distance to the Mediterranean Sea, all contributed significantly to variation in species composition in the terrestrial habitats. Water salinity and transparency accounted for 69% of the variation in aquatic species numbers. There was a weak effect of isolation on similarity of species composition on islands. Eight vegetation types, represented by 13 indicator species identified after TWINSPAN analysis, were distinguished by soil characteristics. Species richness was inversely correlated with clay, organic carbon and total nitrogen in the soil, but positively correlated with calcium carbonate content. From a management perspective, long-term monitoring of threatened habitats in the lake is urgently required as a starting point to preserve biodiversity. Finally, we conclude that the present study supports the hypothesis indicating that larger areas feature higher species richness due to increased numbers of habitats. [source] Life-cycle phenology of some aquatic insects: implications for pond conservationAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2005Jérôme Cayrou Abstract 1.Life-cycles and growth patterns were determined for 21 dominant aquatic insect species in small permanent ponds in an arid, karstic region (SW France, site fr7300909 of the Natura 2000 conservation network). The species studied are widely distributed throughout Europe, but some life-cycle patterns are reported here for the first time. 2.The life-history patterns of the 21 species can be divided into five main types: (i) a semivoltine cycle spreading over 2 years; (ii) slow univoltine cycles; (iii) fast univoltine cycles; (iv) multivoltine life-cycles with a long winter generation and two or three summer generations per year; and (v) bivoltine life-cycles with two fast generations per year. Growth was either exponential over the whole developmental period for a given cohort, or divided into two or three successive periods during each of which the growth rate was fairly constant. 3.Biodiversity estimates strongly depend on the temporal and spatial scale over which observations are made. Ponds thus provide useful models to show how life-history patterns enable many temporally segregated populations to utilize small ecosystems. Conservation frameworks should therefore carefully consider the time-frame needed to survey ponds, as many species with fast cycles could be overlooked. The spatial scale needed to manage threatened habitats and thus preserve pond networks must be broadened, rather than attempting to target individual water bodies for particular management actions. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||