DEVELOPMENTS IN BIOGEOGRAPHY
Patterns of regional structure in the distribution of organisms
Current work is exploring other kinds of patterns in distribution of organisms, including the tendency for species to be associated at different spatial scales. One familiar procedure is to classify areas into regions with similar biotas. In this example, equal-area grid cells are grouped into faunal regions (numbered 1-10) by their bumble bee faunas using Mark Hill's TWINSPAN software (ref 9) (below):
in the strength and breadth of transition zones between biotic regions
The measure of species turnover with the simplest interpretation is the density of range edges. The pattern can be considered to have two components: simple gradients in the numbers of species; and replacements between pairs of species.
A paper in the Journal of Biogeography (1999, 26: 459-474) shows simple measures of these components and the patterns they find within data for birds in sub-Saharan Africa.
Current work is exploring this approach at finer spatial scales and using a broad range of pattern measures. This work relates not only to questions in academic biogeography, but also has potential applications in conservation biology and research into environmental change through changing ecotones.