Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
Abstracts, 3d Conference on Marmots (Cheboksary, Russia, 25-30 August 1997),
Moscow ABF 1997, 216p., 28 (Russian), 146 (English).


B. Goossens, L. Graziani, D. Allaine, Lp. Waits, J.Coulon, P. Taberlet, J. Bouvet

Laboratoire de Biologie des Populations d'Altitude CNRS UMR 5553, Université Joseph Fourier BP53, Grenoble Cedex, France

Monogamous mating systems are restricted to less than 3% of mammalian species, most in Primates, Rodents and Canids (Kleiman, 1977). In contrast, more than 90% of all bird species are monogamous (Lack, 1968). Recently, a number of studies on monogamous bird species have demonstrated evidence for extra-pair copulations (EPC) and extra-pair fertilizations (EPF) (Westneat et al., 1987 ; Gelder, Tegelstre, 1992). Field studies (Reichard, 1995) and genetic studies (Arnold, 1990) have documented EPC in monogamous mammals. Reichard (1995) presents field evidence for EPC in white-handed gibbons (Hylobates lar) that live in monogamous groups. The proportion of within-pair copulations (WPC) versus EPC was 88% versus 12%. In an alpine marmot population of Berchtesgaden (Germany), Arnold (1990) observed that some young had genotypes incompatible with the territorial male of their family group using analysis of allozymes on 2 informative loci (WPC vs EPC was 95% vs 5%).

To analyze paternity in alpine marmot family groups, we chose a more polymorphic marker (microsatellite loci). Our study, conducted in the French Alps (Parc National de la Vanoise) on 13 family groups over 5 years, presents evidence for EPC in this social rodent that lives in monogamous groups (IPC vs EPC was 61% vs 29%).

We captured all the members of 13 family groups during 5 seasons using live traps. All of the family groups have been observed since 1992 and their history has been traced each year. Behavioural observations were collected during the activity period to be sure that we have sampled all the individuals of groups and to determinate the expected dominant pair and their subordinates for each group. We collected hairs from each animal in order to carry out genetic analyses for filiation. DNA was extracted from 10 hairs per individual according to Walsh (1991) and Goossens et al.(submitted).

Six microsatellite loci were investigated in this experiment by PCR amplification using fluorescent labeled primers. All positive PCR products were sized using an ABI PRISM 377 DNA sequencer (Perkin Elmer). For each litter, the genotype of every young and its mother was used to include or exclude the dominant male as the sire.

On 35 litters representing 138 young, we have determined 24 cases of in-pair copulations, 8 cases of EPC from stranger males (out-group EPC), 1 case of within-group EPC from one subordinate male, 1 case of promiscuity (2 females have young in the same group and they copulate with more than 2 males), and 1 case of adoption as an example of polygyny (Goossens et al., 1996). Therefore the proportion of WPC versus EPC was 61% versus 29%, and 26 young out of 138 are produced from EPC, or 19% of extra-pair paternity.

We discuss the costs and the benefits of EPC in a monogamous mammal in relation with the ecological and behavioural constraints, and we estimate the reproductive success for dominant males in our population.

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