Abstract
Sex-biased dispersal is widespread in the animal kingdom and is affected by numerous factors including mating system, social factors and environmental conditions. Unlike birds and mammals, there is no common trend in amphibians and explaining the direction and degree of sex-biased dispersal in species-specific cases is difficult. We conducted a study on dispersal of the Chinese piebald odorous frog (Odorrana schmackeri) in a fragmented landscape associated with dam construction. Ten microsatellite loci were used to analyze 382 samples sourced from 14 fragmented ‘islands’. Assignment tests indicated a significant pattern of female-biased dispersal on one island with inconsistencies in the strength and direction of this pattern between nearby islands. The effects of four island attributes and two potential impact factors on the pattern of sex-biased dispersal were examined. We found that the extent of isolation from the mainland and the number of breeding sites both showed a negative correlation with female biased dispersal, such that the closer an island is to the mainland the more likely it is to display female biased dispersal, and the more breeding sites on an island the more male immigrants. Based on these results, we conclude that geographic isolation and limited breeding resources are the most likely explanation for the patterns of dispersal observed in this fragmented population of amphibians.
Highlights
As a key function in life history, dispersal influences population dynamics, genetic structure and the persistence of populations [1]
In the analysed molecular variance (AMOVA) test, the results showed that most of the molecular variance occurred within populations, while among populations there was explained only 4.77% (Table 3)
The different patterns of sex-biased dispersal on each fragmented island imply that there may be different evolutionary pressures operating between the sexes at different locations and illustrates that sexbiased dispersal is likely to be influenced by multiple factors and may not be shaped by mating system alone [3,41]
Summary
As a key function in life history, dispersal influences population dynamics, genetic structure and the persistence of populations [1]. It is with reference to data from birds and mammals that three alternative hypotheses were generated to explain differences in dispersal patterns between the sexes [5]. These hypotheses are: (1) avoidance of inbreeding, which suggests that the sex will disperse if it bears a greater cost from breeding with relatives [5]; (2) local mating competition, which predicts that the individuals of one sex will disperse to prevent competition with related individuals for mates [6]; and (3) local resource competition, whereby one sex disperses to minimize competition among relatives for a limiting breeding resources [6]. All three hypotheses predict male-biased dispersal and female philopatry in polygynous species (primarily mammals) [7]. While in monogamous species (primarily birds), only local resource competition is thought to drive female dispersal and the other two hypotheses cannot predict sex-biased dispersal [7]
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