-
Views
-
Cite
Cite
Mark O. Johnston, Daniel J. Schoen, CORRELATED EVOLUTION OF SELF‐FERTILIZATION AND INBREEDING DEPRESSION: AN EXPERIMENTAL STUDY OF NINE POPULATIONS OF AMSINCKIA (BORAGINACEAE), Evolution, Volume 50, Issue 4, 1 August 1996, Pages 1478–1491, https://doi.org/10.1111/j.1558-5646.1996.tb03921.x
Close - Share Icon Share
Abstract
The relation between inbreeding depression and rate of self‐fertilization was studied in nine natural populations of the annual genus Amsinckia. The study included two clades (phylogenetic lineages) in which small‐flowered, homostylous populations or species are believed to have evolved from large‐flowered, heterostylous, self‐compatible ones. In one lineage the small‐flowered species is tetraploid with disomic inheritance. Rates of self‐fertilization were 25% to 55% in the four large‐flowered, heterostylous populations; 72% in a large‐flowered but homostylous population; and greater than 99.5% in the four small‐flowered, homostylous populations, which produce seed autonomously. When present, inbreeding depression occurred in the fertility but not the survival components of fitness. Using a cumulative fitness measure incorporating both survival and fertility (flower number), we found inbreeding depression to be lower in the four very highly self‐fertilizing populations than in the five intermediate ones. The Spearman rank correlation between inbreeding depression and selfing rate for the nine populations was –0.50, but was not statistically significant (P = 0.12). Inbreeding depression was greater in the two tetraploid populations than in the very highly self‐fertilizing, diploid ones. Phenotypic stability of progeny from self‐fertilization tended to be higher in populations with lower inbreeding depression. We conclude that levels of self‐fertilization and inbreeding depression in Amsinckia are determined more by other factors than by each other. Estimates of mutation rates and dominance coefficients of deleterious alleles, obtained from a companion study of the four highly self‐fertilizing populations, suggest that a strong relationship may not be expected. We discuss the relationship of the present results to current theory of the coevolution of self‐fertilization and inbreeding depression.
