Browsing by Author "Hespanhol, Helena"
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- Bryophyte Diversity along an Elevational Gradient on Pico Island (Azores, Portugal)Publication . Coelho, Márcia Catarina Mendes; Gabriel, Rosalina; Hespanhol, Helena; Borges, Paulo A. V.; Ah-Peng, ClaudineThe study of elevational patterns is a valuable method for inferring the influence of the climate and other variables in the regional distributions of species. Bryophytes are ideal for revealing different environmental patterns in elevational studies, since they occur from sea level to above the tree line. Taking advantage of the long elevational transect of Pico Island and the use of standardized survey methods, our main aims were: (1) to identify and characterize the alpha and beta diversities of bryophytes across the full elevational gradient (12 sites of native vegetation, ranging from 10 to 2200 m above sea level [a.s.l.]); (2) to detect the ecological factors driving bryophyte composition; (3) to identify bryophytes’ substrate specificity; and (4) to check the presence of rare and endemic species. The identification of 878 microplots yielded 141 species (71 liverworts and 70 mosses), almost half of those known to occur on Pico Island. The bryophyte species richness followed a parabolic unimodal pattern with a mid-elevation peak, where the richest native forests occur. A canonical correspondence analysis (CCA) of the bryophyte composition and explanatory variables revealed the effect of the elevation, precipitation, disturbance, richness of vascular plants and bark pH in explaining bryophyte compositions at regional levels. Very few species of bryophytes showed substrate specificity. Pico Island’s elevational gradient could be an asset for studying long-term changes in bryophyte species composition and alpha diversity under global change.
- The iterative process of plant species inventorying for obtaining reliable biodiversity patternsPublication . Aranda, Silvia C.; Hespanhol, Helena; Homem, Nídia; Borges, Paulo A. V.; Lobo, Jorge M.; Gabriel, RosalinaWe require representative data of species occurrence to explain plant diversity patterns, but most of the available information is incomplete and biased. To improve our knowledge, we suggest that species inventorying should be an iterative process encompassing the following: (1) the detection of taxonomic and geographical gaps; (2) the planning of a survey design to reduce such gaps; and (3) the evaluation of field sampling results. Here, we focus on the latter phase for the bryophytes of Terceira Island (Azores) for which we have previously estimated < 1% of the area as well surveyed based on historical collections. To examine the performance of our stratified survey based on two factors (land use and environmental regions), we used rarefaction curves, ANOVA tests and bootstrap sampling. We recorded 40% of all the species known for the island and presented eight new citations. The species assemblages remained similar between historical and current inventories. Most localities had completeness values > 85%, but we always exceeded the optimal sampling effort. Land uses and environmental regions affected species diversity, but, unexpectedly, to a different degree. Our study illustrates the difficulties of planning field surveys to obtain reliable biodiversity patterns, even when prior information and standardized sampling protocols are explicitly considered.