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Refuge theory and distribution patterns of land snails in Ugandan rain forests

Wronski, T and Hausdorf, B (2007) Refuge theory and distribution patterns of land snails in Ugandan rain forests. UNSPECIFIED. (Unpublished)

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Abstract

Refuge theory assumes that the recent distribution of organisms is influenced by past, usually Pleistocene, environmental changes resulting in the contraction of ranges into refugia or the expansion of ranges from refugia. Refugia are areas that are less affected by environmental changes than the surrounding regions so that organisms that become extinct elsewhere can survive there. The existence and importance of Pleistocene refugia in the northern continents that were heavily affected by Pleistocene glaciations is universally accepted. However, the existence and role of refugia in the tropics is still controversial. Often the existence of refugia is inferred only from the recent distribution of species richness. However, several other patterns in the distribution of organisms are expected to originate, if retraction to refugia and expansion from refugia are processes that affect recent biogeography. Such patterns are nestedness of ranges (Hultén, 1937; Daubenmire, 1975; Hausdorf & Hennig, 2003a), clustering of ranges (***; Hausdorf & Hennig, 2004), and Rapoport effects (***; Pfenninger, 2004; Hausdorf, 2006). It is a long standing question whether the recent distribution of organisms can be explained by current ecological conditions alone or whether it shows the imprint of historical events (Endler, 1982a,b; ***). It has been assumed that the Pleistocene climatic cycles have resulted in cycles of retraction of ranges of organisms to refuges and expansions (***). Such hypotheses have been tested mainly for temperate regions. A retraction of biota into refugia and subsequent range expansions from such refugia will result is specific patterns in distribution data. Such processes should result in:
1. A decrease of species richness with increasing distance from the refuge;
2. Nestedness; that is the biota in regions more distant from the refuge will be subsets of the biota more closer to the refuge;
3. A Rapoport effect; that is the average range extension of the species belonging to a regional biota will increase with increasing distance from the refuge;
4. Clustering of ranges (biotic elements)

Item Type: Other
Additional Information: Presented at: World Congress of Malacology, Antwerp, Belgium
Subjects: Q Science > QH Natural history
Q Science > QL Zoology
Divisions: Natural Sciences and Psychology
Date Deposited: 14 Aug 2017 09:23
Last Modified: 14 Aug 2017 09:23
URI: http://researchonline.ljmu.ac.uk/id/eprint/6910

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