A robust distance coefficient between distribution areas incorporating geographic distances.
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Demography↗
Biomedical subjects
Bernhard Hausdorf
Publications and source records attributed to Bernhard Hausdorf.
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↗
Relationships and origin of endemic Lake Baikal gastropods (Caenogastropoda: Rissooidea) based on mitochondrial DNA sequences.
The phylogenetic relationships and the origin of two groups of rissooid freshwater snails endemic to Lake Baikal were investigated using partial mitochondrial COI, 12S rDNA, and 16S rDNA sequences. The Baikalian Benedictiinae proved to be closely related to the Lithoglyphinae. According to a molecular clock estimate the two groups diverged in the Paleogene. The Benedictiinae might have evolved autochthonously in precursors of Lake Baikal. The Baikalian Baicaliidae are probably most closely related to the Amnicolidae and the Bithyniidae. These groups diverged at the latest during the Cretaceous. Thus the origin of the Baicaliidae predates the origin of the Baikal rift zone. The Baicaliidae evolved probably in other Central Asian freshwater reservoirs. However, the radiation of the extant Baicaliidae only started in the Neogene and might have occurred autochthonously in Lake Baikal. The conchological similarity of the Baicaliidae and the Pyrgulidae is due to convergence. The Pyrgulidae diverged from the common stem lineage of the other hydrobiid families at the latest in the Jurassic. The Bithyniidae is derived from hydrobiids and is related to the Amnicolidae.
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↗