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Accueil du site → Doctorat → États-Unis → 1975 → THE SYSTEMATICS, ECOLOGY, AND ZOOGEOGRAPHY OF THE AFRICAN GERBILS, TATERILLUS (RODENTIA : CRICETIDAE)

University of Arizona (1975)

THE SYSTEMATICS, ECOLOGY, AND ZOOGEOGRAPHY OF THE AFRICAN GERBILS, TATERILLUS (RODENTIA : CRICETIDAE)

Robbins, Charles Brian

Titre : THE SYSTEMATICS, ECOLOGY, AND ZOOGEOGRAPHY OF THE AFRICAN GERBILS, TATERILLUS (RODENTIA : CRICETIDAE)

Auteur : Robbins, Charles Brian

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1975

Résumé
The Rodent genus Taterillus (Family Cricetidae ; Subfamily Gerbillinae) occurs in the Sahel Savanna and the Sudan and Guinea Woodlands of Africa, between the Sahara Desert and the high forest. It is found west to Senegal and Mauritania, east to Somalia, and south to northern Tanzania. A single species can occupy all of the above vegetation zones. The systematic arrangement of Taterillus presented is a result of examination of the taxonomic relationships of the species in this genus. The taxonomy is a result of : (1) a study of the history and use of the many named taxa ; (2) analysis of geographic variation using univariate and multivariate statistical techniques ; and (3) examination of evolutionary and zoogeographic relationships. The available data suggest only seven species rather than the 19 species indicated by original descrip tions. In the past, small population samples from widely separated areas were described as different taxa using characteristics which were neither clearcut nor consistent, Examination of over 3000 specimens from 21 countries, including many not available to previous workers, and all of the holotypes, shows that minor variation in size, shape, color, and other features used as diagnostic of taxa in Taterillus are not necessarily indicative of taxonomic relationships. The species I recognize are : Taterillus arenarius Robbins, 1974 ; T. congicus Thomas, 1915 ; T. emini (Thomas, 1892) ; T. gracilis (Thomas, 1892) ; T. harringtoni (Thomas, 1906) ; T. lacustris (Thomas and Wroughton, 1907) ; and T. pygargus (F. Cuvier, 1838) . The descriptions of these species are based on cranial morphology, karyotypic differences, distribution, and possible habitat selection. Typical data show that five species described from Ethiopia, Kenya, Somalia, and the Sudan, with only minor geographic variation in cranial morphology and the same karyotype (2N=44), are in fact a single species (T. harringtoni). A total of six chromosomal forms have been found. Only minor population variation occurs within a species in the number of their major chromosome arms (fundamental number), Several localities in both West and East Africa have two different chromosomal forms occurring together with no hybridization yet found. Based on diploid and funda mental number, plus chromosome and cranial morphology, the six karyotyped species can be divided into three groups. These are : (1) 2N=54, FN=64-66 (T. congicus) ; (.2) 2N=44, FN=62 (T, harringtoni) ; and (3) the West African taxa (2N=22/23, FN=3 6-4 0 - T. pygargus ; 2N=28, FN=44 - T. lacustris ; 2N=30, FN=36 - T. arenarius ; 2N=36/37, FN=42 44 - T. gracilis. Most differences in cranial morphology involve age variation. Arbitrary age classes were established based on molar tooth morphology and only a single adult age class was used to eliminate morphological variation due to age. Secondary sexual differences were not found. A major problem in Taterillus systematics concerns distinguishing between sympatric species which are morphologically similar, and allopatric species which are closely related. This report shows the importance of using all available data when studying the biology and systematics of an, mammalian group. It can also be seen that compu terized statistical procedures are necessary when working with many specimens from a large geographic area. This study has resulted in a systematic arrangement based on the biological relationships of members of the genus Taterillus so that future studies on ecological relationships can be carried out to give more meaningful results,

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