Abstract Detail

Recent Topics Posters

Abrahams , Richard S [1], Payton, Adam C. [1], McDaniel, Stuart [1].

Adaptive variation at a putative chromosomal inversion in the moss Ceratodon purpureus.

A major goal of modern evolutionary biology is to understand the genetic basis of adaptive variation. Here we report that the Adenosine kinase gene (adk) in Ceratodon purpureus is linked to a putative chromosomal inversion, and that this polymorphism is shaped by multiple forms of selection. Several lines of evidence strongly suggests adk is linked to an inversion. First, recombination between adk and other markers was suppressed in a genetic map. Second, adk contains three allelic classes (two closely related - A1 and A2, and a third more distantly related - B), each with limiited variation. The three allelcic classes have deeper coalescene times than is typical for the species. To study evolutionary forces maintaining variation at the putative inversion, we collected several hundred sporophytes from populations in Durham, North Carolina, and Storrs, Connecticut. From each sporophyte we estimated the total spore production and the mean spore viability. We then genotyped six haploid gametophytes from each sporophyte and compared the observed frequencies to Hardy-Weinberg proportions. First, F_ST was higher at adk than other loci, with each allele class exhibiting different frequencies in the two populations. We found an excess of heterozygotes, suggesting that the putative inversion contributes to assortative mating or heterozyote advantage. However, heterozygotes did not produce more spores (nor decreased spore viability), although adk variation explained ~8% of the variation in spore production. The allelic effect on spore production differed between the two populations, suggesting that genetic background influences the expression of this polymorphism. To identify other selective forces that may act on the adk polymorphism, we used a common garden experiment to test whether gametophyte traits covaried with the three allelic classes. We counted the number of days before the first gametophore appeared, as well as the number of days before antheridial buds were evident in males. From previous Q_ST / F_ST experiments we know that these traits are adaptively differentiated among populations. Gametophytes with the A2 allele produced gametophores two days slower than individuals with the A1 or B alleles. The close genealogical relationship between the A1 and A2 allelic classes suggests that the mutation causing this phenological difference arose recently. Collectively these data show that the chromosomal region near adk contributes to potentially adaptive variation in development time variation and assortative mating in C. purpureus, although the variants that control these traits may be distant from the adk locus.

1 - University Of Florida, Biology Department, Gainesville, FL, 32611, USA

Keywords:
moss
Ecology
Evolution
phenology
Evolutionary genetics
population genetics
chromosomal inversion .

Presentation Type: Recent Topics Poster
Session: P
Location: /
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PRT035
Abstract ID:1273
Candidate for Awards:None