Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

PHYLOGEOGRAPHIC INVESTIGATION OF MOLECULAR VARIATION IN WILD (C. IBEX E C. AEGAGRUS) AND DOMESTIC GOATS (C. HIRCUS)

MILANESI E.*, NEGRINI R.*, CREPALDI P.**, ZAGDSUREN Y.***, ERTRUGRUL O.****, CICOGNA M.**, LUIKART G.*****, AJMONE MARSAN P.*

* Istituto di Zootecnica, Università Cattolica del S. Cuore, Piacenza (I)

** Istituto di Zootecnia Generale, Università degli Studi, Milano (I)

*** The Agriculture University of Mongolia, Ulambaatar city (MG)

**** Faculty of Veterinary Science, Ankara University, Ankara (TR)

***** Laboratoire de Biologie des Populations d’Altitude, CNRS, Grenoble (F)

genetic distance, biodiversity, AFLP

Three AFLP primer pairs have been used to characterise the genome and investigate genetic diversity in 222 animals from the genus Capra, belonging to two wild species (C. ibex e C. aegagrus) and to 9 breeds of domestic goat (C. hircus) from Asia (Anatolian Black, Angora, Mongolian Cashmer, Bayendelger Cashmer e Malaysian Native), Africa (West African Dwarf) and Europe (Capra della Val Passiria, Girgentana, Maltese). Data on 133 AFLP markers have been analysed to investigate the main genetic parameters within breeds, genetic distances between breeds and species and the partition of genetic variation within and between species and breeds. In C. ibex we observed values of marker polymorphism and heterozygosity lower that those found in C. aegagrus and much lower than those observed in C. hircus. In the latter species, the maintenance of a high level of genetic diversity at neutral loci parallels the remarkable phenotypic variation at adaptive traits, due to the domestication process, that can presently be observed in domestic goats. Almost 50% of the total variation at AFLP loci was found between species (Gst index, Nei, 1973), while within C. hircus the variability at marker loci is mainly maintained within the 9 populations analysed. Dice similarities, Nei's Da genetic distances and the first two principal axes of PCOOA based on these indexes clearly separate C. ibex, C. aegagrus and C. hircus into three separate groups. Interestingly the Malaysian native population results half way between C. aegagrus and the most geographically distant domestic goat populations analysed, suggesting that in Southern Asia genetic exchange between wild and domestic goats might have continued until recently or, confirming existing data on mitochondrial DNA variation (Luikart et al., 2000), that indicate Southern Asia as a possible second site of domestication, independent on the fertile crescent. In addition, these results confirm the probable origin of C. hircus from C. aegagrus. A high correlation (r=0.75, P<0.01) between genetic and geographic distance was observed within C. hircus. Consistently the third and fourth principal axes of PCOOA separate domestic goat breeds highly in accordance with their geographic origin. The strong geographic structure of nuclear DNA is in contrast with investigations on the maternal lineage, that indicate in this species the presence of only a minor component of genetic variation between continents (Luikart et al., 2001). The absence of geographic structure in mitochondrial DNA may reflect extensive transportation and trade of goat females carried along during human migrations, while the geographic structure of genomic DNA may suggest crossing of domesticated females with local wild males, during the process of breed formation. In this view, the investigation of Y chromosome variation will shed light on the dynamics leading to breed formation and to the patterns of genetic variation we observe nowadays in goats.