Abstract Detail

Population Genetics

Moore, Richard C. [1], Brown, Jennifer [2], Leeds, Blake [3], Hickey, Ryan [3], Hoang, Bao Tram [3], Adu, Esther [3].

The signature of local adaptation for the Carica papaya Y chromosome.

The tropical fruit crop, papaya (Carica papaya) is dioecious in the wild and sex is determined by the presence of an active Y chromosome; males are XY while females are XX. In many XY chromosome systems, the Y chromosome has a paucity of genetic variation due to its reduced effective population size, as well as the increased effect of background selection (selection against deleterious mutations) and/or positive selection in this region of suppressed recombination. In natural populations of Costa Rican papaya, we have discovered the signature of increased polymorphism relative to expectations. We used population genetic analyses to address the hypothesis that local adaptation favors the disproportionate distribution of three Y haplotypes (MSY1, MSY2, and MSY3) among the five regional populations of Costa Rica. The distribution of three Y haplotypes among the five regions varies, such that the Northwest (NW) region and the Nicoya peninsula almost exclusively have males with the MSY3 haplotype. Pair-wise FST values for Y-linked loci comparing the NW Pacific or Nicoya populations with all other populations are significantly elevated relative to X-linked and autosomal loci. Elevated FST comparisons for the Nicoya and NW Pacific populations are consistent with locally adapted Y chromosomes in these regions, with selective deterrence of the migration of certain haplotypes into these populations. However, low levels of within population diversity may also result in elevated FST. We therefore used an absolute measure of diversity, Da, the net sequence divergence, to estimate the amount of genetic differentiation between populations. Consistent with the hypothesis of local adaptation, Y-linked Da values are significantly greater than those for X-linked and autosomal loci for almost all comparisons between either the NW Pacific or Nicoya populations and all other regional populations. Thus, we propose that the MSY3 haplotype confers some significant advantage to males within the NW and Nicoya populations of Costa Rica and that MSY1 and MSY2 migrants are selectively excluded from these regions.

1 - Miami University, Botany, 316 Pearson, Oxford, OH, 45056, USA
2 - South Carolina Governor's School, 401 Railroad Avenue, Hartsville, South Carolina , 29550
3 - Miami University, 212 Pearson Hall, Oxford, OH, 45056, United States

Keywords:
none specified

Presentation Type: Oral Paper
Session: 39, Population Genetics
Location: 201/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 11:00 AM
Number: 39012
Abstract ID:675
Candidate for Awards:None