285 research outputs found
Interactive effects of losing key grazers and ecosystem engineers vary with environmental context
No full textLoss of biodiversity may cause significant changes to ecosystem structure and functioning. Evidence from long-term in situ removal experiments is rare but important in determining the effects of biodiversity loss against a background of environmental variation. Limpets and mussels are thought to be important in controlling community structure on wave-exposed shores in the UK: limpets as key grazers, mussels as ecosystem engineers. A long-term factorial removal experiment revealed interactive effects that varied between 2 shores in SW England. At one site (Harlyn), removing limpets caused a significant shift in community structure, but where limpets were lost, the presence or absence of mussels made little difference. Where limpets were present, however, the removal of mussels changed the structure and variability of the community. At the other site (Polzeath), the loss of mussels caused significant changes in community structure, and limpets played a less important role. At Harlyn, fucoid algae were abundant throughout the year. There were fewer algae at Polzeath, and cover was dominated by the summer bloom of ephemerals. At Harlyn, the limpets played a major role in controlling algae, but their effects were mediated by the presence of mussels. Other grazers were not able to fulfil their role. At Polzeath, mussels were far more important, and ephemeral algae grew on them regardless of the presence or loss of limpets. These findings emphasise the need to assess spatial and temporal variation in the effects of biodiversity loss and the importance of interactive effects of loss of multiple species from different functional groups
Taxonomy, phylogenetic and biogeographical relationships of African grassland Francolins (Genus: Scleroptila)
No full textBibliography: leaves 23-28.The potential for using a combination of molecular and whole-organismal data has opened up new avenues for avian taxonomy, phylogenetics and biogeography. Such a multifaceted approach is used here to identify diagnosable taxa within the Orange River Francolin Scleroptila levaillanloides species complex and resolve evolutionary relationships between these taxa and other mono-and polytypic forms within the Red-winged Group of francolins (= genus Scleroplila sensli lalo). Mitochondrial cytochrome-b DNA sequence data (±250 b.p.) from 50 individuals and 19 morphological characters extracted from reports in published literature were employed to achieve these aims. These characters were analysed separately and also in combination using maximum parsimony (DNA sequences and organismal data), maximum likelihood (DNA sequences) and distance (DNA sequences) analyses. Monophyly of the Red-winged Group plus the Ring-necked Francolin Dendroperdix slreptophorus was supported by all the analyses (bootstrap support ranged from 50%-94%) except distance analysis. The Orange River Francolin complex was found to be non-monophyletic. Two distinct clades were identified, one comprising taxa from southwestern and the other from northeastern Africa. Morphological analysis yielded a distinct clade of the southwestern Orange River Francolin. The other polytypic species and assemblages thereof show poor resolution. The results of this study clearly demonstrate a need for further assessment of the taxonomic status of Scleroptila spp. and their phylogenetic relationships
Taxonomy, phylogeny and eco-biogeography of southern African white-eyes (Zosterops spp.) Aves: order Passeriformes, Family: Zosteropidae
No full textIncludes abstract.Includes bibliographical references (p. 193-216).The aim of this study was to incorporate all lines of evidence to establish the true taxonomy and phylogeny of southern African Zosterops. Character data sets used include plumage and morphometric measures, vocal characters and molecular (mitochondrial and nuclear) DNA sequences. A broad scale phylogeographic analysis was also performed to establish the evolutionary process driving the diversity observed among these birds
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