A robust distance coefficient between distribution areas incorporating geographic distances.
Explore the source record for details and available documents.
Demography↗
Biomedical subjects
Christian Hennig
Publications and source records attributed to Christian Hennig.
Nestedness of north-west European land snail ranges as a consequence of differential immigration from Pleistocene glacial refuges.
We investigated whether ranges in continental biota are nested. We propose a test for nested subset structure which can detect nestedness even if there are several sets of nested subsets as expected on a larger geographical scale. The test is based on a Monte Carlo simulation with a null model that considers spatial autocorrelation of the occurrences of a taxon. The number of cases in which the occurrences of a species form a subset of the occurrences of another species is used as test statistic. In a case study we show that the ranges of north-west European land snail species are significantly nested. The geographic centres of the sets of nested subsets correlate with glacial refuges. The differential immigration of taxa restricted to southern refuges during the glacials was probably an important mechanism resulting in the observed nestedness of the ranges of the north-west European land snail species. Some species which were more widespread during Pleistocene glacials contribute little to the nested subset pattern and are not nested among themselves. A comparison between groups of species differing in their dispersal abilities indicates that differences in the degree of nestedness are primarily due to differences in the variance of range sizes and not in dispersal abilities. We found a very weak correlation between dispersal ability and the rank of ranges in the sets of nested subsets indicating that nestedness might in part be caused by differential dispersal abilities. We assume that the graded variation of environmental parameters might be more important in generating the nestedness of ranges of north-west European land snail species than their differential dispersal abilities.
Animals↗
Biotic element analysis in biogeography.
Biotic element analysis is an alternative to the areas-of-endemism approach for recognizing the presence or absence of vicariance events in a given region. If an ancestral biota was fragmented by vicariance events, biotic elements or clusters of distribution areas should emerge. We propose a statistical test for clustering of distribution areas based on a Monte Carlo simulation with a null model that considers the spatial autocorrelation in the data. The hypothesis tested is that the observed degree of clustering of ranges can be explained by the range size distribution, the varying number of taxa per cell, and the spatial autocorrelation of the occurrences of a taxon alone. A method for the delimitation of biotic elements which uses model-based Gaussian clustering is introduced. We demonstrate our methods and show the importance of grid size by means of a case study, an analysis of the distribution patterns of southern African species of the weevil genus Scobius. The example highlights the difficulties in delimiting areas of endemism if dispersal has occurred and illustrates the advantages of the biotic element approach.
Animals↗