The population outcrossing rate (t) and adult inbreeding coefficient (F) are key parameters in mating system evolution. The magnitude of inbreeding depression as expressed in the field can be estimated given t and F via the method of Ritland (1990). For a given total sample size, the optimal design for the joint estimation of t and F requires sampling large numbers of families (100-400) with fewer offspring (1-4) per family. Unfortunately, the standard inference procedure (MLTR) yields significantly biased estimates for t and F when family sizes are small and maternal genotypes are unknown (a common occurrence when sampling natural populations). Here, we present a Bayesian method implemented in the program BORICE (Bayesian Outcrossing Rate and Inbreeding Coefficient Estimation) that effectively estimates t and F when family sizes are small and maternal genotype information is lacking. BORICE should enable wider use of the Ritland approach for field-based estimates of inbreeding depression. As proof of concept, we estimate t and F in a natural population of Mimulus guttatus. In addition, we describe how individual maternal inbreeding histories inferred by BORICE may prove useful in studies of inbreeding and its consequences.
Bibliographical noteFunding Information:
We thank Mark Holder for invaluable Python programming advice, Chris Eckert for sharing his database of mating system papers, Chris Hudson for help with GUI development, Cory Wallace for aid in population sampling, and three anonymous reviewers for comments on the manuscript. This project was supported in part by an Institutional Research and Academic Career Development Award (IRACDA) to the University of Kansas (Award number: K12-GM063651), as well as NIH grant R01-GM073990 to JKK.
- Outcrossing rate
- inbreeding coefficient
- inbreeding depression
- mating system