Abstract
Genetic diversity is essential for persistence of animal populations over both the short- and long-term. Previous studies suggest that genetic diversity may decrease with population decline due to genetic drift or inbreeding of small populations. For oscillating populations, there are some studies on the relationship between population density and genetic diversity, but these studies were based on short-term observation or in low-density phases. Evidence from rapidly expanding populations is lacking. In this study, genetic diversity of a rapidly expanding population of the Greater long-tailed hamsters during 1984–1990, in the Raoyang County of the North China Plain was studied using DNA microsatellite markers. Results show that genetic diversity was positively correlated with population density (as measured by % trap success), and the increase in population density was correlated with a decrease of genetic differentiation between the sub-population A and B. The genetic diversity tended to be higher in spring than in autumn. Variation in population density and genetic diversity are consistent between sub-population A and B. Such results suggest that dispersal is density- and season-dependent in a rapidly expanding population of the Greater long-tailed hamster. For typically solitary species, increasing population density can increase intra-specific attack, which is a driving force for dispersal. This situation is counterbalanced by decreasing population density caused by genetic drift or inbreeding as the result of small population size. Season is a major factor influencing population density and genetic diversity. Meanwhile, roads, used to be considered as geographical isolation, have less effect on genetic differentiation in a rapidly expanding population. Evidences suggest that gene flow (Nm) is positively correlated with population density, and it is significant higher in spring than that in autumn.
Highlights
Population genetic diversity has been thought to be essential to ensure population viability [1,2]
I was significantly (P = 0.005, 0.002 and 0.001) and positively (r = 0.910, 0.962 and 0.964) correlated with trap success in spring, autumn, and yearly, respectively (Figure 2 and Table 1). These results indicate that genetic diversity is density-dependent in a rapidly expanding population of the Greater long-tailed hamster
We found that gene flow between sub-population A and B (Nm = 522.7) was higher than in low density years (Nm = 312.4), and genetic differentiation (Fst = 0.0005) was lower than in low density years (Fst = 0.0008)
Summary
Population genetic diversity has been thought to be essential to ensure population viability [1,2]. Genetic diversity of a population can be influenced by many factors such as dispersal, genetic drift, mutation and selection [3,4,5,6,7,8]. The genetic diversity of populations tends to be stable and reach equilibrium between gene flow and genetic drift [9]. Due to human disturbance such as hunting, habitat destruction or pollution, the population size of some species often declines dramatically. Reduced population size or isolation may cause genetic losses from inbreeding [10], or genetic drift [11], or even both. It takes a long time to re-establish genetic diversity through mutation alone, which is not considered as one of main factors influencing genetic diversity in short-term
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