Abstract Detail

Population Genetics

Weller, Stephen G. [1], Sakai, Ann K. [1], Campbell, Diane R. [1], Culley, Theresa M. [2].

Heritabilities and genetic correlations for allocation to female and male traits in gynodioecious Schiedea adamantis (Caryophyllaceae).

The quantitative genetic basis of allocation to reproductive traits was investigated in gynodioecious Schiedea adamantis (Caryophyllaceae) to determine the levels of heritable variation important for the evolution of dioecy from gynodioecy. Genetic correlations were also investigated because positive genetic correlations within or across sexes could impede the evolution of separate sexes. We used biomass as a measure of common currency for patterns of allocation to female and male function. Narrow-sense heritabilities were highly significant for female traits (near 0.4 for carpel biomass and close to 1.0 for capsule biomass) and stamen biomass (near 0.3). Genetic correlations among nearly all female allocation traits were positive and highly significant. Significant positive genetic correlations were also characteristic of many allocation traits in hermaphrodites. Sexual dimorphism in allocation was much stronger in S. adamantis relative to S. salicaria, consistent with the difference between the species in percentage of females (39% in S. adamantis compared with 12-13% in S. salicaria) and presumed evolution towards dioecy. Females had significantly larger carpels and greater capsule and seed biomass, but reduced sepal biomass. There were no significant positive or negative genetic correlations between female and male traits within hermaphrodites. Female biomass traits were correlated across sexes, however, which might impede evolution of sexual dimorphism. High heritabilities and patterns of allocation in S. adamantis would be consistent with continuing selection for increased sexual dimorphism, although the recent decline in the size of the sole population of this species from several hundred to only six plants makes extinction the more likely outcome.

Broader Impacts:
Schiedea adamantis is known historically from only a single population on the rim of Diamond Head Crater on Oahu. Despite this rarity, we found that the species has retained considerable quantitative genetic variation for traits important in reproduction. The recent decline in the size of this population is more likely to result from drought and invasive species rather than depleted genetic variability, and may have restricted S. adamantis to the margins of its former range. Our quantitative genetic results also suggest that reintroduction might be possible for this species, in view of the variation in traits potentially important for adaptation to continued environmental change.

1 - University of California Irvine, Department of Ecology & Evolutionary Biology, 321 Steinhaus Hall, Irvine, California, 92697-2525, USA
2 - University of Cincinnati, Department of Biological Sciences, 614 Rieveschl Hall, Cincinnati, Ohio, 45221, USA

Keywords:
sexual dimorphism
gynodioecy
heritabilities
genetic correlations
Schiedea
dioecy.

Presentation Type: Oral Paper:Papers for Topics
Session: 35
Location: 556A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 10:30 AM
Number: 35002
Abstract ID:775