Consequences of multiple mating-system shifts for population and range-wide genetic structure in a coastal dune plant.

Evolutionary transitions from outcrossing to selfing can strongly affect the genetic diversity and structure of species at multiple spatial scales. We investigated the genetic consequences of mating-system shifts in the North American, Pacific coast dune endemic plant Camissoniopsis cheiranthifolia (Onagraceae) by assaying variation at 13 nuclear (n) and six chloroplast (cp) microsatellite (SSR) loci for 38 populations across the species range. As predicted from the expected reduction in effective population size (Ne ) caused by selfing, small-flowered, predominantly selfing (SF) populations had much lower nSSR diversity (but not cpSSR) than large-flowered, predominantly outcrossing (LF) populations. The reduction in nSSR diversity was greater than expected from the effects of selfing on Ne alone, but could not be accounted for by indirect effects of selfing on population density. Although selfing should reduce gene flow, SF populations were not more genetically differentiated than LF populations. We detected five clusters of nSSR genotypes and three groups of cpSSR haplotypes across the species range consisting of parapatric groups of populations that usually (but not always) differed in mating system, suggesting that selfing may often initiate ecogeographic isolation. However, lineage-wide genetic variation was not lower for selfing clusters, failing to support the hypothesis that selection for reproductive assurance spurred the evolution of selfing in this species. Within three populations where LF and SF plants coexist, we detected genetic differentiation among diverged floral phenotypes suggesting that reproductive isolation (probably postzygotic) may help maintain the striking mating-system differentiation observed across the range of this species.

Changes in fatty acid composition during development of tissues of coconut (Cocos nucifera L.) embryos in the intact nut and in vitro.

Intact coconuts were germinated in situ and compared with excised zygotic embryos germinated in vitro. The growth of the embryonic tissue and their fatty acid compositions were measured. Haustoria, plumules and radicles of coconuts germinated in situ grew continuously and proportionately throughout the 120 d experiment with haustauria increasing to 45 g x nut(-1) and weighing 4-5-fold more than the other two tissues. The plumules and radicles of the seedlings cultured in vitro also grew continuously but the haustoria grew sporadically between 15 d and 75 d in culture and, at 250 mg x nut(-1) after 75 d, were smaller than the other two tissues. All the tissues of the nuts grown in situ contained significant amounts of lauric acid, the acid characteristic of coconut oil, as well as longer chain saturated and unsaturated fatty acids. The content of medium and long chain fatty acids increased in all growing tissues as the experiment proceeded, especially the haustorium which contained 24-35% of its fatty acid as lauric acid; the fat content of solid endosperm reduced during this period. Seedlings grown in vitro, on the other hand, failed to accumulate lauric acid in any of their tissues (haustorium contained 6-11% of its fatty acid as lauric acid). The results may have implications for the design of growth media for growing zygotic and somatic cultures of coconut and may provide a marker for successful germination.