Presentation Detail

Hybridization

Kingston, Sarah [1], Parchman, Thomas [2], Gompert, Zachariah [3], Buerkle, C. Alex  [4], Cicero, Carla [5], Klicka, John [6], Braun, Michael [1].

Hybridization, introgression and differentiation on a continental scale: genome-wide sequence analysis.

Species boundaries and their maintenance are topics of great interest in both general and evolutionary biology. In the context of inter-species hybridization, the maintenance or breakdown of reproductive isolation is observable in a natural setting. When two genomes interact, genomic patterns of heterogeneity can offer insight into selective as well as stochastic evolutionary processes. Two species of towhee, Pipilo maculatus and P. ocai, interact across well-documentedhybrid gradients in central Mexico. Specimens of both species and their hybrids have been collected along two of these gradients: Teziutlán (~1200km, 11 locations, 167 total specimens) and Transvolcanic (~700km, 10 sites, 295 total specimens) gradients. A third closely-related species, P. erythrophthalmus, is distributed in the eastern United States and interacts with western P. maculatus populations across a mid-western hybrid zone. Specimens of P. erythrophthalmus in the eastern US (27 total specimens), P. maculatus in the western US (45 totalspecimens), and both P. maculatus and P. ocai outside of the hybrid transectsin Mexico and Central America (42 total specimens) were also included for greater phylogeographic context. We utilized a high-throughput genomic sequencingtechnique (genotype by sequencing, GBS) to collect nearly 29,000 singlenucleotide polymorphism sites for analysis. Bayesian modeling allowed us to estimate population geneticparameters such as F_ST and assess variation in introgression across both Mexican hybrid transects. Outlier loci from the genomic background signal reveal portions of the genome undergoing either differential introgression or divergence (possibly related to maintenance of reproductive isolation). The ribbon-like habitat corridors in the Teziutlán gradientand island-like distribution of the Transvolcanic habitat allow us to compare differential introgression and gene flow across a semi-porous species membrane in two different spatial contexts. We find a small but significant level of overlap in outlier loci between the two Mexican transects, as well as a heterogeneous signal of introgression and adaptation across the genome. Maintenance of historical divergence is acting in a cohesive manner on a core set of loci across transects, but local environmental and stochastic factors are also important driving forces. The larger phylogeographic context of the N. American distribution for all three species allows us to compare the three species simultaneously and in biogeographic context. The genetic pattern exhibited bears a strong geographic signal and isolation-by-distance component across both the hybrid transects as well as the continental distributions of all three species.

1 - Smithsonian Institution, Smithsonian Institution- MRC 534, 4210 Silver Hill Rd, Suitland, Maryland, 20746, United States
2 - University of Wyoming, Department of Botany, 3165, University of Wyoming, Laramie, Wyoming, 82071, United States
3 - Texas State University
4 - University Of Wyoming, Dept Of Botany, 3165, 1000 E University Ave, Laramie, WY, 82071, USA
5 - University of California, Berkeley,, Museum of Vertebrate Zoology, 3101 Valley Life Sciences Bldg, Berkeley, CA, 94720-3160, USA
6 - University of Washington, Burke Museum, Department of Biology

Keywords:
hybridization
gene flow
reproductive isolation
introgression
phylogeography.

Presentation Type: Regular Oral Presentation
Session: 45
Location: Peruvian A/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 4:15 PM
Number: 45004
Abstract ID:139
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation