Primary faunal succession in volcanic terrain: lava and cave studies on the Canary Islands |
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Authors: | N. PHILIP ASHMOLE,PEDRO OROMÍ ,MYRTLE J. ASHMOLE,JOSE L. MARTÍ N |
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Affiliation: | Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT;*Departamento de Biologia Animal (Zoologia), Universidad de La Laguna, 38206 La Laguna, Canary Islands |
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Abstract: | Invertebrate communities in volcanic habitats of different ages on the islands of La Palma and El Hierro were studied using standardized trapping and searching techniques. A variety of graphical and numerical approaches were used to analyse relationships among the sites. Young, barren lava flows constitute aeolian ecosystems with a fauna of generalized detritivores and predators, especially collembolans, earwigs, thysamirans and crickets. Surface samples have many individuals and low diversity; those from caves have smaller numbers but similar taxonomic composition. Vegetated surface habitats have richer communities, with diverse herbivores and predators but largely without the pioneer 'lavicolous' species. Caves with high humidity and stable temperature contain mainly specialized troglobitic species, but if there are both dry and humid sections lavicoles may also be present. Divergence into distinct epigean and hypogean communities results from both abiotic and biotic processes, including erosion and plant succession. While these occur mainly on the surface they also affect caves, increasing humidity and providing insulation from variations in external environmental conditions; the process is considered as a form of 'maturation' of the caves. Various models of succession are considered, which might help to account for the disappearance of lavicoles from mature epigean and hypogean communities. |
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Keywords: | Faunal succession volcanic habitats lava flows caves aeolian ecosystems Canary Islands arthropods lavicole troglobite |
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