Browsing by Subject "extinction"
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Item Dicynodonts and the end Permian event(Bernard Price Institute for Palaeontological Research, 1990) King, Gilian MPatterns of diversity changes in several groups of Late Permian South African terrestrial tetrapods are examined. Using data contained in Kitching (1977), histograms are presented which illustrate changes in a) total number of tetrapod genera per biostratigraphic zone; b) total number of therapsid genera per zone; c) total number of herbivore genera per zone; and d) total number of carnivore genera per zone. Herbivorous and carnivorous genera are categorized as comprising small, medium or large individuals and histograms which document changes in number of genera in each of these six categories per zone are presented. Potential sources of error inherent in the data are outlined. Broad changes in generic diversity are noted and possible explanations for these changes are presented. It is concluded that the present data do not provide overwhelming evidence for a rapid and catastrophic drop in terrestrial tetrapod diversity at the very end of the Permian, but do illustrate a gradual and continuing decrease from the middle of the Late Permian into the middle of the Triassic.Item How accurate are coat traits for discriminating wild and hybrid forms of Felis silvestris?(Walter de Gruyter GmbH, 2015-02) Ballesteros-Duperón, E.; Virgós, E.; Moleón, M.; Barea-Azcón, J.M.; Gil-Sánchez, J.M.Hybridisation between domestic cats, Felis catus, and wildcats, Felis silvestris, could lead to the genetic extinction of the latter; therefore, checking hybridisation rates in wild populations is of vital conservation importance. However, detecting hybridisation in the field is particularly challenging. Here, we aim to test the success of morphological-based procedures for discriminating wildcats from their hybrids and domestic cats, against genetic methods. We checked 17 putative Spanish wildcats by using two different classification systems based on coat patterns. None of the putative wildcats analysed in this study seemed to have an admixed genotype. Concordance between genetic and pelage approaches was almost total: only one coat classification produced mixed results with detection of one potential hybrid. Assignment was worse when performed in the field after a rapid examination of coat characters. We conclude that classification systems using coat traits could serve as surrogates of genetic approaches, but only after careful examination of those characters with more discriminatory power. Thus, the control of hybrid populations in the field as a management tool to preserve the genetic identity of wild forms is problematic if based on crude approaches or incomplete classification systems.