In vertebrates, genetic diversity influences many elements of an individual's fitness, such as health, survival, and reproduction. 'Inbred' individuals with less genetic diversity have greater parasite loads, reduced survivorship, and produce fewer surviving offspring than do more genetically diverse, or 'outbred" individuals - a phenomenon called inbreeding depression. Beyond these individual costs, inbreeding depression also has negative consequences on populations and species; therefore, understanding how genetic diversity impacts fitness has significant implications for conserving endangered species. Primates are especially vulnerable to inbreeding depression because of their long lifespans and low reproduction rates, yet thus far, no study has investigated how the loss of genetic diversity affects the health, survival, and reproduction of a wild primate population.
The challenge remains to identify the specific genes that can serve as estimates of 'genetic quality' because they influence variation in individual health, survival, and reproduction. One protein-coding region likely to contribute to individual differences is the Major Histocompatibility Complex (MHC). This family of genes controls the immune system's ability to recognize bacteria, viruses, and parasites, and thus, plays an essential role in the survival of an individual and their offspring.
To examine how MHC impacts fitness in a threatened primate, the ring-tailed lemur (Lemur catta), doctoral student Kathleen Grogan (Duke University), under the supervision of Dr. Christine Drea, will compare MHC diversity against survival, reproductive success, and health across an environmental stressor in a wild population at Beza Mahafaly Special Reserve, Madagascar. Survival and reproductive success, measured using long-term census data, and health, measured as parasite prevalence, diversity, and burden in fecal samples collected (a) under 'typical' environmental conditions and (b) following a severe drought, will be compared against MHC diversity. By examining the relationship between genetic diversity and fitness in wild ring-tailed lemurs, this research tests how individual differences in MHC diversity influence that individual's health, survival, and reproduction. This award will support the training of a graduate student. Additionally, the genetic information will inform conservation efforts.
