Inbreeding depression in self-incompatible and self-compatible populations of Leavenworthia alabamica

Abstract

Inbreeding depression is one of the leading factors preventing the evolution of self-fertilization in plants. In populations where self-fertilization evolves, theory suggests that natural selection against partially recessive deleterious alleles will reduce inbreeding depression. The purpose of this study was to evaluate this hypothesis by comparing the magnitude of inbreeding depression in self-incompatible and self-compatible populations of Leavenworthia alabamica. Within-population crosses were conducted to compare the quantity and quality of offspring produced by outcrossing and selffertilization. These progeny were grown in a common greenhouse and inbreeding depression was measured in germination, survival, biomass, transition rate to flowering, flower number, petal length, pollen grains/anther, pollen viability, and ovule number. In comparison to outcrossing, self-fertilization led to the production of fewer and smaller seeds within self-incompatible populations. Moreover, inbreeding depression was observed in eight of 11 offspring traits within self-incompatible populations of L. alabamica. In contrast, there was significant inbreeding depression only in flower number within self-compatible populations. The results of this study are consistent with the idea that selffertilization selectively removes partially recessive deleterious alleles causing inbreeding depression in natural plant populations. However, in plant species such as L. alabamica where self-compatibility may evolve in small populations following long-distance dispersal, declines in inbreeding depression may also be facilitated by genetic drift. Heredity (2005) 94, 159-165.

Heterosis in an Isolated, Effectively Small, and Self-Fertilizing Population of the Flowering Plant Leavenworthia Alabamica

“…The geographic locations of these populations are reported elsewhere (Busch 2005a). Seeds from 25-30 families within each population were germinated in petri dishes and maintained in an incubator with 14-hour days (18ЊC) and 10-hour nights (8ЊC).…”

“…1). In contrast, self-compatibility has evolved at the margins of the species range, in which populations are approximately an order of magnitude smaller, undergo extinction and recolonization, and have purged strongly deleterious alleles causing inbreeding depression (Busch 2005a). Individuals in these populations readily produce seed autonomously and have many floral adaptations for self-pollination such as introrse anthers, short petals, short styles, and low pollen to ovule ratios (Lloyd 1965).…”

Pollen quality for pollinators tracks pollen quality for plants in Mimulus guttatus

“…Reduced viability is often associated with processes such as hybridization and inbreeding (Carr and Dudash 1997, Golmirzaie et al 1998, Melser et al 1999, Busch 2005, Glaettli and Goudet 2006, Eppley and Pannell 2009, Bures et al 2010, or environmental stress such as exposure to high temperature or pollutants (Handique and Baruah 1995, Tretyakova et al 1996, Gottardini et al 2008, Pasqualini et al 2011.…”

Inbreeding depression in self-incompatible North-American Arabidopsis lyrata: disentangling genomic and S-locus-specific genetic load

“…In addition, S-linked load may have a role in shaping S-allele genealogies and have an effect on the frequency distribution of S-alleles in natural populations. Numerous studies have documented the existence of a mutational load in species with a genetic self-incompatibility system (for example, Stone, 2004;Busch, 2005;Glemin et al, 2006). However, only few studies have attempted to disentangle the S-linked genetic load from the background genomic load.…”