Geoffrey Lockwood

Bio: Geoffrey Lockwood is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 390 citations.

Introduced species: a significant component of human-caused global change

Abstract: Humans move species beyond their native ranges both deliberately and inadvertently, and many of these species become established and spread in their new habitat. The list of established introduced species grows annually, as does the number of them that cause significant economic and ecological effects. One recent and notorious example in North America is the Eurasian zebra mussel which like many other aquatic organisms entered in the ballast water of ships, and like many others spread rapidly once it arrived. The invasion of zebra mussels is unusual in the magnitude of its economic consequences; the mussels grow and reproduce rapidly, covering river and lake bottoms and municipal and industrial water inlets. The cost of clearing blocked intake pipes has been calculated to be approximately US$2 billion (Office of Technology Assessment, 1993). Zebra mussels also alter populations of algae and the concentrations of nutrients in whole ecosystems (Caraco et al., 1997), and they are continuing to spread in rivers, lakes, and canals throughout North America. We suggest that biological invasions by notorious species like the zebra mussel, and its many less-famous counterparts, have become so widespread as to represent a significant component of global environmental change. This point has been made before (eg Elton, 1958), but is not widely appreciated, even by the global change research community or by those who study and/or work to control biological invasions. In part, this lack of appreciation reflects the fact that our perception is limited spatially it is possible to document the presence and importance of biological invasions almost anywhere, but more difficult to perceive that invasions are almost everywhere. In part, it may also reflect a narrow view of global environmental change, one that emphasizes climate change (global warming) at the expense of other, equally significant components of human-caused global change. In this paper, we place biological invasions in context with other human-caused global environmental changes; briefly describe the global extent of biological invasion; illustrate the consequences of particular invasions as they affect human health and wealth, and/or the functioning and biological diversity of natural ecosystems; discuss interactions between biological invasions and other components of global change; and describe ways that society can prevent, manage, and/or cope with invasions.

An Update of Wallace’s Zoogeographic Regions of the World

Abstract: Modern attempts to produce biogeographic maps focus on the distribution of species, and the maps are typically drawn without phylogenetic considerations. Here, we generate a global map of zoogeographic regions by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals. We identify 20 distinct zoogeographic regions, which are grouped into 11 larger realms. We document the lack of support for several regions previously defined based on distributional data and show that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere. We further show that the integration of phylogenetic information provides valuable insight on historical relationships among regions, permitting the identification of evolutionarily unique regions of the world.

The atlas of southern African birds

Abstract: This is a major work covering the breeding and non-breeding birds of the Southern African sub-region. Published in two volumes, Volume One includes introductory chapters describing methodology and the 'avi'-geography of the region, with habitat photos, and coverage of the non-passerines, whilst Volume Two covers the passerines. Some 900 species are covered in total, including 200 vagrants, with detailed species accounts, maps and statistics for at least 500 species. Conservation issues are discussed for most species. '...sets new standards in its scope and in its methods...it will come to be valued ever more as years go by, for setting a measured baseline against which to judge environmental trends across the great range of southern Africa.' - Colin Bibby, "BirdLife International".

Global biogeography and ecology of body size in birds

Abstract: In 1847, Karl Bergmann proposed that temperature gradients are the key to understanding geographic variation in the body sizes of warm-blooded animals. Yet both the geographic patterns of body-size variation and their underlying mechanisms remain controversial. Here, we conduct the first assemblage-level global examination of 'Bergmann's rule' within an entire animal class. We generate global maps of avian body size and demonstrate a general pattern of larger body sizes at high latitudes, conforming to Bergmann's rule. We also show, however, that median body size within assemblages is systematically large on islands and small in species-rich areas. Similarly, while spatial models show that temperature is the single strongest environmental correlate of body size, there are secondary correlations with resource availability and a strong pattern of decreasing body size with increasing species richness. Finally, our results suggest that geographic patterns of body size are caused both by adaptation within lineages, as invoked by Bergmann, and by taxonomic turnover among lineages. Taken together, these results indicate that while Bergmann's prediction based on physiological scaling is remarkably accurate, it is far from the full picture. Global patterns of body size in avian assemblages are driven by interactions between the physiological demands of the environment, resource availability, species richness and taxonomic turnover among lineages.