Breeding system and habitat effects on fitness components in three neotropical Costus ( Zingiberaceae).

Abstract

All species are self-compatible, and require a treefall gap for germination and establishment. Self-pollination resulted in lower seed output in all species; this difference was significant for Costus allenii and C. laevis. Seedling growth of selfed, outcrossed and naturally-pollinated Costus allenii, C. laevis and C. guanaiensis in sun and shade habitats in the greenhouse was unaffected by breeding system, but significantly affected by habitat, with reduced growth in shade. Selfed progeny had the lowest biomass in all treatments, with inbreeding depression for growth ranging from 8-25% compared to out-crossed performance. Reduced growth and greater variation in growth for selfed, as compared to out-crossed, progeny are consistent with the hypothesis that inbreeding depression in these species results from homozygosity of rare, deleterious alleles which are not expressed in the heterozygous state. Relative biomass production varied more between sun and shade habitats for selfed, than outcrossed or naturally-pollinated progeny, suggesting that increased homozygosity following inbreeding reduces genotypic versatility.-from Author