Is genetic drift to blame for testicular dysgenesis syndrome in Semliki chimpanzees (Pan troglodytes schweinfurthii)?

Abstract

We present 3 likely cases of testicular dysgenesis syndrome (TDS) within a community of chimpanzees (Pan troglodytes schweinfurthii). We tested whether genetic drift may be the culprit, as a genetic cause has been suspected to account for TDS among other wildlife. We successfully sequenced a 367-bp segment spanning the first hypervariable region within the D-loop of the mitochondrial genome for 78 DNA samples. We found 24 polymorphic sequence sites consisting of 7 singletons and 17 parsimony informative sites. This sample contained 9 haplotypes with a diversity index of 0.78 (SD=0.03). All tests against the null hypothesis of neutral polymorphisms were non-significant (P>.10). The mismatch distribution of pairwise differences does not fit a Poisson's curve (raggedness index=0.166; SSD=0.12; P=1). Thus, we found no significant signs of genetic isolation, population expansion, or genetic bottleneck. Alternative causes of TDS and how they might pertain to this population are discussed.