Browsing by Subject "Forests"

Now showing 1 - 5 of 5
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    Open Access
    Departures from the energy-biodiversity relationship in south african passerines: are the legacies of past climates mediated by behavioral constraints on dispersal?
    (Public Library of Science, 2015) Péron, Guillaume; Altwegg, Res
    Legacies of paleoclimates in contemporary biodiversity patterns have mostly been investigated with global datasets, or with weakly dispersive organisms, and as a consequence been interpreted in terms of geographical or physical constraints. If paleoclimatic legacies also occurred at the regional scale in the distributions of vagile organisms within biomes, they would rather suggest behavioral constraints on dispersal, i.e., philopatric syndromes. We examined 1) the residuals of the regression between contemporary energy and passerine species richness in South African biomes and 2) phylogenetic dispersion of passerine assemblages, using occupancy models and quarter-degree resolution citizen science data. We found a northeast to southwest gradient within mesic biomes congruent with the location of Quaternary mesic refugia, overall suggesting that as distance from refugia increased, more clades were lacking from local assemblages. A similar but weaker pattern was detected in the arid Karoo Biomes. In mobile organisms such as birds, behavioral constraints on dispersal appear strong enough to influence species distributions thousands of years after historical range contractions.
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    Open Access
    The ecological and geographic context of morphological and genetic divergence in an understorey-dwelling bird
    (Public Library of Science, 2014) Ribeiro, Angela M; Lloyd, Penn; Dean, W Richard J; Brown, Mark; Bowie, Rauri C K
    Advances in understanding the process of species formation require an integrated perspective that includes the evaluation of spatial, ecological and genetic components. One approach is to focus on multiple stages of divergence within the same species. Species that comprise phenotypically different populations segregated in apparently distinct habitats, in which range is presently continuous but was putatively geographically isolated provide an interesting system to study the mechanisms of population divergence. Here, we attempt to elucidate the role of ecology and geography in explaining observed morphological and genetic variation in an understorey-dwelling bird endemic to southeastern Africa, where two subspecies are recognized according to phenotype and habitat affinity. We carried out a range-wide analysis of climatic requirements, morphological and genetic variation across southeast Africa to test the hypothesis that the extent of gene flow among populations of the brown scrub-robin are influenced by their distinct climatic niches. We recovered two distinct trends depending on whether our analyses were hierarchically structured at the subspecies or at the within subspecies level. Between subspecies we found pronounced morphological differentiation associated with strong reproductive isolation (no gene flow) between populations occupying divergent climatic niches characterized by changes in the temperature of the warmest and wettest month. In contrast, within subspecies, we recovered continuous morphological variation with extensive gene flow among populations inhabiting the temperate and sub-tropical forests of southern Africa, despite divergence along the climate axis that is mainly determined by minimum temperature and precipitation of the coldest months. Our results highlight the role of niche divergence as a diversifying force that can promote reproductive isolation in vertebrates.
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    Host-plant species conservatism and ecology of a parasitoid fig wasp genus (Chalcidoidea; Sycoryctinae; Arachonia)
    (Public Library of Science, 2012) McLeish, Michael J; Beukman, Gary; van Noort, Simon; Wossler, Theresa C
    Parasitoid diversity in terrestrial ecosystems is enormous. However, ecological processes underpinning their evolutionary diversification in association with other trophic groups are still unclear. Specialisation and interdependencies among chalcid wasps that reproduce on Ficus presents an opportunity to investigate the ecology of a multi-trophic system that includes parasitoids. Here we estimate the host-plant species specificity of a parasitoid fig wasp genus that attacks the galls of non-pollinating pteromalid and pollinating agaonid fig wasps. We discuss the interactions between parasitoids and the Ficus species present in a forest patch of Uganda in context with populations in Southern Africa. Haplotype networks are inferred to examine intraspecific mitochondrial DNA divergences and phylogenetic approaches used to infer putative species relationships. Taxonomic appraisal and putative species delimitation by molecular and morphological techniques are compared. Results demonstrate that a parasitoid fig wasp population is able to reproduce on at least four Ficus species present in a patch. This suggests that parasitoid fig wasps have relatively broad host- Ficus species ranges compared to fig wasps that oviposit internally. Parasitoid fig wasps did not recruit on all available host plants present in the forest census area and suggests an important ecological consequence in mitigating fitness trade-offs between pollinator and Ficus reproduction. The extent to which parasitoid fig wasps exert influence on the pollination mutualism must consider the fitness consequences imposed by the ability to interact with phenotypes of multiple Ficus and fig wasps species, but not equally across space and time.
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    Mapping the elephants of the 19th century East African ivory trade with a multi-isotope approach
    (Public Library of Science, 2016) Coutu, Ashley N; Lee-Thorp, Julia; Collins, Matthew J; Lane, Paul J
    East African elephants have been hunted for their ivory for millennia but the nineteenth century witnessed strongly escalating demand from Europe and North America. It has been suggested that one consequence was that by the 1880s elephant herds along the coast had become scarce, and to meet demand, trade caravans trekked farther into interior regions of East Africa, extending the extraction frontier. The steady decimation of elephant populations coupled with the extension of trade networks have also been claimed to have triggered significant ecological and socio-economic changes that left lasting legacies across the region. To explore the feasibility of using an isotopic approach to uncover a 'moving frontier' of elephant extraction, we constructed a baseline isotope data set (δ 13 C, δ 15 N, δ 18 O and 87 Sr/ 86 Sr) for historic East African elephants known to have come from three distinct regions (coastal, Rift Valley, and inland Lakes). Using the isotope results with other climate data and geographical mapping tools, it was possible to characterise elephants from different habitats across the region. This baseline data set was then used to provenance elephant ivory of unknown geographical provenance that was exported from East Africa during the late nineteenth and early twentieth centuries to determine its likely origin. This produced a better understanding of historic elephant geography in the region, and the data have the potential to be used to provenance older archaeological ivories, and to inform contemporary elephant conservation strategies.
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    New insights into samango monkey speciation in South Africa
    (Public Library of Science, 2015) Dalton, Desiré L; Linden, Birthe; Wimberger, Kirsten; Nupen, Lisa Jane; Tordiffe, Adrian S W; Taylor, Peter John; Madisha, M Thabang; Kotze, Antoinette
    The samango monkey is South Africa's only exclusively forest dwelling primate and represents the southernmost extent of the range of arboreal guenons in Africa. The main threats to South Africa's forests and thus to the samango are linked to increasing land-use pressure and increasing demands for forest resources, resulting in deforestation, degradation and further fragmentation of irreplaceable habitats. The species belongs to the highly polytypic Cercopithecus nictitans group which is sometimes divided into two species C . mitis and C . albogularis . The number of subspecies of C . albogularis is also under debate and is based only on differences in pelage colouration and thus far no genetic research has been undertaken on South African samango monkey populations. In this study we aim to further clarify the number of samango monkey subspecies, as well as their respective distributions in South Africa by combining molecular, morphometric and pelage data. Overall, our study provides the most comprehensive view to date into the taxonomic description of samango monkeys in South Africa. Our data supports the identification of three distinct genetic entities namely; C . a . labiatus , C . a . erythrarchus and C . a . schwarzi and argues for separate conservation management of the distinct genetic entities defined by this study.