Y‐chromosome analysis confirms highly sex‐biased dispersal and suggests a low male effective population size in bonobos ( Pan paniscus )

Abstract

Dispersal is a rare event that is difficult to observe in slowly maturing, long‐lived wild animal species such as the bonobo. In this study we used sex‐linked (mitochondrial DNA sequence and Y‐chromosome microsatellite) markers from the same set of individuals to estimate the magnitude of difference in effective dispersal between the sexes and to investigate the long‐term demographic history of bonobos. We sampled 34 males from four distinct geographical areas across the bonobo distribution range. As predicted for a female‐dispersing species, we found much higher levels of differentiation among local bonobo populations based upon Y‐chromosomal than mtDNA genetic variation. Specifically, almost all of the Y‐chromosomal variation distinguished populations, while nearly all of the mtDNA variation was shared between populations. Furthermore, genetic distance correlated with geographical distance for mtDNA but not for the Y chromosome. Female bonobos have a much higher migration rate and/or effective population size as compared to males, and the estimate for the mitochondrial TMRCA (time to most recent common ancestor) was approximately 10 times greater than the estimate for the Y chromosome (410 000 vs. 40 000–45 000). For humans the difference is merely a factor of two, suggesting a more stable demographic history in bonobos in comparison to humans.

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