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Patterns of alpha and beta diversity of epigean arthropods at contrasting land-uses of an oceanic island (Terceira, Azores)
Publication . Cardoso, Pedro; Gaspar, Clara; Dinis, Francisco; Borges, Paulo A. V.
"[…]. To study the effect of land-use change in biological communities it is necessary to understand how are the different components of diversity distributed in space. Diversity has long been separated into different components according to the phenomena that interest ecologists (Whittaker, 1960, 1972): i) local species richness, i.e., alpha (community) diversity that measures the species richness of a local assemblage; ii) beta diversity, the degree of difference between communities (Whittaker et al., 2001), that measures turnover of species between communities and; iii) gamma (regional) diversity, which can be considered an equivalent to alpha diversity on a larger scale, but reflects the allopatric distribution of related taxa. Alpha diversity, of which species richness is just the most visible measure, is perhaps the most studied aspect of diversity. However, probably more important than knowing how many species live in a site at a given time, it is to know what species are these. In islands, where the introduction of non-indigenous species is one of the major threats to indigenous species (Borges et al., 2006; Martín et al., 2008), especially endemics, this question is even more significant. Even if man-made habitats are species rich, they may be empty of species considered as conservation priority and abundant in exotic species (Cardoso et al. 2009a). […]" (da Introdução)
Ilhas Oceânicas
Publication . Borges, Paulo A. V.; Azevedo, Eduardo B.; Borba, Alfredo Emílio Silveira de; Dinis, Francisco; Gabriel, Rosalina; Silva, Emiliana
Os arquipélagos dos Açores e Madeira constituem as duas zonas insulares portuguesas. Localizados no Oceano Atlântico, estes dois arquipélagos possuem uma importância estratégica em termos de zona económica exclusiva e em termos militares (e.g., Base Americana das Lajes na ilha Terceira). Na sua qualidade de ilhas oceânicas isoladas possuem igualmente ecossistemas singulares (e.g., a floresta de Laurissilva da Madeira foi recentemente nomeada como Património da UNESCO) e uma elevada diversidade de espécies únicas (ver as listas recentes da fauna e flora dos Açores e da Madeira e Selvagens; Borges et al., 2005a, 2008a). Apesar de cada um destes arquipélagos possuir características exclusivas, os Açores funcionam como um excelente modelo de ecossistema insular, neste caso com nove ilhas de origem vulcânica e isoladas no meio do oceano. Assim, optámos por focar este capítulo essencialmente no arquipélago dos Açores, fazendo no entanto uma análise da diversidade faunística e florística do arquipélago da Madeira. Muitos dos processos sócio-ecológicos poderão, no entanto, ser extrapoláveis para a Madeira já que estas ilhas se encontram sensivelmente à mesma latitude. Diga-se ainda que optámos por limitar a nossa análise essencialmente aos ecossistemas terrestres. (da Introdução)
A spatial scale assessment of habitat effects on arthropod communities of an oceanic island
Publication . Cardoso, Pedro; Aranda, Silvia C.; Lobo, Jorge M.; Dinis, Francisco; Gaspar, Clara; Borges, Paulo A. V.
Most habitats in the Azores have undergone substantial land-use changes and anthropogenic disturbance during the last six centuries. In this study we assessed how the richness, abundance and composition of arthropod communities change with: (1) habitat type and (2) the surrounding land-use at different spatial scales. The research was conducted in Terceira Island, Azores. In eighty-one sites of four different habitat types (natural and exotic forests, semi-natural and intensively managed pastures), epigaeic arthropods were captured with pitfall traps and classified as endemic, native or introduced. The land-use surrounding each site was characterized within a radius ranging from 100 to 5000 m. Non-parametric tests were used to identify differences in species richness, abundance and composition between habitat types at different spatial scales. Endemic and native species were more abundant in natural forests, while introduced species were more abundant in intensively managed pastures. Natural forests and intensively managed pastures influenced arthropod species richness and composition at all spatial scales. Exotic forests and semi-natural pastures, however, influenced the composition of arthropod communities at larger scales, promoting the connectivity of endemic and native species populations. Local species richness, abundance and composition of arthropod communities are mostly determined by the presence of nearby natural forests and/or intensively managed pastures. However, semi-natural pastures and exotic forests seem to play an important role as corridors between natural forests for both endemic and native species. Furthermore, exotic forests may serve as a refuge for some native species.
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Fundação para a Ciência e a Tecnologia
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SFRH
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BD