Analysis of inbreeding depression in mixed-mating plants provides evidence for selective interference and stable mixed mating

Citation

Winn AA, Elle E, Kalisz S, Cheptou P, Eckert CG, Goodwillie C, Johnston MO, Moeller DA, Ree RH, Sargent RD & Vallejo-Marín M (2011) Analysis of inbreeding depression in mixed-mating plants provides evidence for selective interference and stable mixed mating. Evolution, 65 (12), pp. 3339-3359. https://doi.org/10.1111/j.1558-5646.2011.01462.x

Abstract
Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of selfing, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r greater than 0.8), mixed-mating (0.2 ≤r≥ 0.8), and highly outcrossing (r less than 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (δ= 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them.

Keywords
Age-specific expression of inbreeding depression; gynodioecy; mating-system evolution; outcrossing; purging; selfing

Journal
Evolution: Volume 65, Issue 12