Browsing by Author "Gaston, Kevin J."
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- ItemConservation during times of change : correlations between birds, climate and people in South Africa(Academy of Science of South Africa, 2004) Van Rensburg, Berndt J.; Erasmus, Barend F. N.; Van Jaarsveld, Albert S.; Gaston, Kevin J.; Chown, Steven L.Few studies have investigated the ability of national conservation networks to adapt to changes in underlying environmental drivers (such as precipitation) and their consequences for factors such as human density and species richness patterns. In this article, the South African avifauna is used as the basis for such analysis to ascertain the likely extent of current, and future, anthropogenic impacts on priority conservation areas. We show that human population pressure is high in or around most of these priority areas and is likely to increase, given the magnitude of post-climate change estimated from predicted changes in precipitation and relationships between species richness, human densities, and rainfall. Although additional conservation areas, such as the Important Bird Area (IBA) network, are likely to introduce valuable flexibility to conservation management, only limited options are available for such expansions, and the conservation value of these areas is likely to be compromised by changing climate. Ultimately, a more integrated conservation approach is needed for effective conservation policies. Such an approach should confer adequate protection on current reserves and emphasize sustainable utilization of non-reserve areas.
- ItemThe fynbos and succulent Karoo biomes do not have exceptional local ant richness(Public Library of Science (PLoS), 2012-03) Braschler, Brigitte; Chown, Steven L.; Gaston, Kevin J.Background: The Fynbos (FB) and Succulent Karoo biomes (SKB) have high regional plant diversity despite relatively low productivity. Local diversity in the region varies but is moderate. For insects, previous work suggests that strict phytophages, but not other taxa, may have high regional richness. However, what has yet to be investigated is whether the local insect species richness of FB and SKB is unusual for a region of this productivity level at this latitude, and whether regional richness is also high. Here we determine whether this is the case for ants. Methodology/Principal Findings: We use species richness data from pitfall traps in the FB and SKB in the Western Cape Province, South Africa and a global dataset of local ant richness extracted from the literature. We then relate the globally derived values of local richness to two energy-related predictors—productive energy (NDVI) and temperature, and to precipitation, and compare the data from the FB and SKB with these relationships. We further compare our local richness estimates with that of similar habitats worldwide, and regional ant richness with estimates derived from other regions. The local ant species richness of the FB and SKB falls within the general global pattern relating ant richness to energy, and is similar to that in comparable habitats elsewhere. At a regional scale, the richness of ants across all of our sites is not exceptional by comparison with other regional estimates from across the globe. Conclusions/Significance: Local richness of ants in the FB and SKB is not exceptional by global standards. Initial analyses suggest that regional diversity is also not exceptional for the group. It seems unlikely that the mechanisms which have contributed to the development of extraordinarily high regional plant diversity in these biomes have had a strong influence on the ants.
- ItemThe global distribution and drivers of alien bird species richness(Public Library of Science, 2017-01-12) Dyer, Ellie E.; Cassey, Phillip; Redding, David W.; Collen, Ben; Franks, Victoria; Gaston, Kevin J.; Jones, Kate E.; Kark, Salit; Orme, C. David; Blackburn, Tim M.Alien species are a major component of human-induced environmental change. Variation in the numbers of alien species found in different areas is likely to depend on a combination of anthropogenic and environmental factors, with anthropogenic factors affecting the number of species introduced to new locations, and when, and environmental factors influencing how many species are able to persist there. However, global spatial and temporal variation in the drivers of alien introduction and species richness remain poorly understood. Here, we analyse an extensive new database of alien birds to explore what determines the global distribution of alien species richness for an entire taxonomic class. We demonstrate that the locations of origin and introduction of alien birds, and their identities, were initially driven largely by European (mainly British) colonialism. However, recent introductions are a wider phenomenon, involving more species and countries, and driven in part by increasing economic activity. We find that, globally, alien bird species richness is currently highest at midlatitudes and is strongly determined by anthropogenic effects, most notably the number of species introduced (i.e., “colonisation pressure”). Nevertheless, environmental drivers are also important, with native and alien species richness being strongly and consistently positively associated. Our results demonstrate that colonisation pressure is key to understanding alien species richness, show that areas of high native species richness are not resistant to colonisation by alien species at the global scale, and emphasise the likely ongoing threats to global environments from introductions of species.
- ItemHemispheric asymmetries in biodiversity : a serious matter of ecology(PLoS One, 2004-11) Chown, Steven L.; Sinclair, Brent J.; Leinaas, Hans P.; Gaston, Kevin J.Penguins have been receiving a lot of bad press lately. They are considered somehow counter, spare, strange. Unlike most plant and animal groups, they do not show a peak of species richness towards the equator and a decline towards the poles. This more conventional spatial pattern is conveniently known as the latitudinal diversity gradient because of the strong covariance of richness and other measures of biodiversity that it describes. It is one of the most venerable, well-documented, and controversial large-scale patterns in macroecology (Willig et al. 2003).
- ItemIntraspecific body size frequency distributions of insects(Public Library of Science -- PLoS, 2011-03) Gouws, E. Jeanne; Gaston, Kevin J.; Chown, Steven L.Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n≥100). In addition, we review the published IaBSFDs for insects, though doing so is complicated by their under-emphasis in the literature. The form of IaBSFDs can differ substantially between mass-based and linear measures. Nonetheless, in non-social insects they tend to be normally distributed (18 of 27 species) or in fewer instances positively skewed. Negatively skewed distributions are infrequently reported and log transformation readily removes the positive skew. Sexual size dimorphism does not generally cause bimodality in IaBSFDs. The available information on IaBSFDs in the social insects suggests that these distributions are usually positively skewed or bimodal (24 of 30 species). However, only c. 15% of ant genera are polymorphic, suggesting that normal distributions are probably more common, but less frequently investigated. Although only 57 species, representing seven of the 29 orders of insects, have been considered here, it appears that whilst IaBSFDs are usually normal, other distribution shapes can be found in several species, though most notably among the social insects. By contrast, the interspecific body size frequency distribution is typically right-skewed in insects and in most other taxa. © 2011 Gouws et al.
- ItemLocal scale comparisons of biodiversity as a test for global protected area ecological performance : a meta-analysis(Public Library of Science, 2014-08-27) Coetzee, Bernard W. T.; Gaston, Kevin J.; Chown, Steven L.Terrestrial protected areas (PAs) are cornerstones of global biodiversity conservation. Their efficacy in terms of maintaining biodiversity is, however, much debated. Studies to date have been unable to provide a general answer as to PA conservation efficacy because of their typically restricted geographic and/or taxonomic focus, or qualitative approaches focusing on proxies for biodiversity, such as deforestation. Given the rarity of historical data to enable comparisons of biodiversity before/after PA establishment, many smaller scale studies over the past 30 years have directly compared biodiversity inside PAs to that of surrounding areas, which provides one measure of PA ecological performance. Here we use a meta-analysis of such studies (N = 86) to test if PAs contain higher biodiversity values than surrounding areas, and so assess their contribution to determining PA efficacy. We find that PAs generally have higher abundances of individual species, higher assemblage abundances, and higher species richness values compared with alternative land uses. Local scale studies in combination thus show that PAs retain more biodiversity than alternative land use areas. Nonetheless, much variation is present in the effect sizes, which underscores the context-specificity of PA efficacy.
- ItemMacrophysiology for a changing world(The Royal Society, 2008-07) Chown, Steven L.; Gaston, Kevin J.The Millennium Ecosystem Assessment (MA) has identified climate change, habitat destruction, invasive species, overexploitation and pollution as the major drivers of biodiversity loss and sources of concern for human well-being. Understanding how these drivers operate and interact and how they might be mitigated are among the most pressing questions facing humanity. Here, we show how macrophysiology-the investigation of variation in physiological traits over large geographical, temporal and phylogenetic scales-can contribute significantly to answering these questions. We do so by demonstrating, for each of the MA drivers, how a macrophysiological approach can or has helped elucidate the impacts of these drivers and their interactions. Moreover, we illustrate that a large-scale physiological perspective can provide insights into previously unrecognized threats to diversity, such as the erosion of physiological variation and stress tolerance, which are a consequence of the removal of large species and individuals from the biosphere. In so doing we demonstrate that environmental physiologists have much to offer the scientific quest to resolve major environmental problems. © 2008 The Royal Society.
- ItemPriorities for protected area research(International Union for Conservation of Nature, 2018-05) Dudley, Nigel; Hockings, Marc; Stolton, Sue; Amend, Thora; Badola, Ruchi; Bianco, Mariasole; Chettri, Nakul; Cook, Carly; Day, Jon C.; Dearden, Phil; Edwards, Mary; Ferraro, Paul; Foden, Wendy; Gambino, Roberto; Gaston, Kevin J.; Hayward, Natalie; Hickey, Valerie; Irving, Jason; Jeffries, Bruce; Karapetyan, Areg; Kettunen, Marianne; Laestadius, Lars; Laffoley, Dan; Lham, Dechen; Lichtenstein, Gabriela; Makombo, John; Marshall, Nina; McGeoch, Melodie; Nguyen, Dao; Nogue, Sandra; Paxton, Midori; Rao, Madhu; Reichelt, Russell; Rivas, Jorge; Roux, Dirk; Rutte, Claudia; Sadovy, Yvonne; Schreckenberg, Kate; Sovinc, Andrej; Sutyrina, Svetlana; Utomo, Agus; Vallauri, Daniel; Vedeld, Pal Olav; Verschuuren, Bas; Waithaka, John; Woodley, Stephen; Wyborn, Carina; Zhang, YanA hundred research priorities of critical importance to protected area management were identified by a targeted survey of conservation professionals; half researchers and half practitioners. Respondents were selected to represent a range of disciplines, every continent except Antarctica and roughly equal numbers of men and women. The results analysed thematically and grouped as potential research topics as by both practitioners and researchers. Priority research gaps reveal a high interest to demonstrate the role of protected areas within a broader discussion about sustainable futures and if and how protected areas can address a range of conservation and socio-economic challenges effectively. The paper lists the hundred priorities structured under broad headings of management, ecology, governance and social (including political and economic issues) and helps contribute to setting future research agendas.