Genetic Consequences of Polygyny and Social Structure in an Indian Fruit Bat, Cynopterus Sphinx. Ii. Variance in Male Mating Success and Effective Population Size

Abstract

Abstract. Variance in reproductive success is a primary determinant of genetically effective population size (N e ), and thus has important implications for the role of genetic drift in the evolutionary dynamics of animal taxa characterized by polygynous mating systems. Here we report the results of a study designed to test the hypothesis that polygynous mating results in significantly reduced N e in an age-structured population. This hypothesis was tested in a natural population of a harem-forming fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae), in western India. The influence of the mating system on the ratio of variance N e to adult census number (N) was assessed using a mathematical model designed for age-structured populations that incorporated demographic and genetic data. Male mating success was assessed by means of direct and indirect paternity analysis using 10-locus microsatellite genotypes of adults and progeny from two consecutive breeding periods (n ϭ 431 individually marked bats). Combined results from both analyses were used to infer the effective number of male parents in each breeding period. The relative proportion of successfully reproducing males and the size distribution of paternal sibships comprising each offspring cohort revealed an extremely high within-season variance in male mating success (up to 9.2 times higher than Poisson expectation). The resultant estimate of N e /N for the C. sphinx study population was 0.42. As a result of polygynous mating, the predicted rate of drift (1/2N e per generation) was 17.6% higher than expected from a Poisson distribution of male mating success. However, the estimated N e /N was well within the 0.25-0.75 range expected for age-structured populations under normal demographic conditions. The life-history schedule of C. sphinx is characterized by a disproportionately short sexual maturation period scaled to adult life span. Consequently, the influence of polygynous mating on N e /N is mitigated by the extensive overlap of generations. In C. sphinx, turnover of breeding males between seasons ensures a broader sampling of the adult male gamete pool than expected from the variance in mating success within a single breeding period.

Species diversity of small mammals at Gunung Stong State Park, Kelantan, Malaysia

“…Lim et al (2008) suggested that the distribution pattern of C. sphinx should be investigated as little is known about the current distribution of this species in Malaysia. Clinal variation in terms of size of this species was discussed by Storz et al (2001) and our observations (unpublished data) indicate that C. sphinx is not highly adaptable in Peninsular Malaysia incongruent with observations of Bates et al (2008b). Although widespread the abundance of this species is determined by the type of vegetation sampled (Campbell et al 2006).…”

Mating system of a Neotropical roost-making bat: the white-throated, round-eared bat, Lophostoma silvicolum (Chiroptera: Phyllostomidae)

“…In this species, males sire 29% of the pups in their harem (Heckel et al 1999). In other species, this value averages around 60% but can range up to 100% in individual harems (Storz et al 2001b;Ortega et al 2003). In comparison, male birds, such as tree swallows, remain socially monogamous in spite of 70% or more extra-pair copulations by the females (Kempenaers et al 1999).…”

“…At the same time, sheltering another male's pup may not incur additional costs, if the nest-holder can sire the mother's next offspring. Reproductive success of male C. sphinx depends on colony structure during the previous post-partum estrus rather than current parturition (Storz et al 2001b), and the same may be true for male L. silvicolum. We show that relatedness of males with pups in their nest is high, indicating that they mate with the females that roost with them, thus justifying roost-making.…”

Comparative Genetics of Sarcoid Tumour-Affected and Non-Affected Mountain Zebra (Equus zebra) Populations

“…The results from AMOVA reflected extreme heterozygote deficiency among tumour-affected populations, possibly due to either a Wahlund effect caused by sampling functionally independent social reproductive harems that has confounded the interpretation of Wright's F IS (Storz et al 2001). The 'within population' inbreeding estimate (f = FIS) or value of deficit of heterozygotes.…”