Abstract Detail

Hybrids and Hybridization

Buck, Ryan [1], Whipple, Amy [2], Gehring, Catherine [3], Flores-Renteria, Lluvia [4].

Hybridization and Reclassification of Pinyon Pines.

The two-needled pinyon pine (Pinus edulis) experiences some of the highest mortality rates among forest species after prolonged periods of drought, which are expected to increase in intensity with climate change. A close relative, Pinus monophylla, has one needle-per-fascicle, a trait thought to be adapted to more arid environments. Both species are dominant in the Southwest and play important ecological roles in supporting biodiversity. Despite occupying different ecological niches, they have overlapping distributions, facilitating potential hybridization. Two additional needle types have been observed near contact zones: fallax-type and californiarum-type. Both have one needle-per-fascicle but have varying numbers of resin canals and stomatal rows. Additionally, californiarum-type overlaps in distribution with Pinus quadrifolia, which has four needles-per-fascicle and is sister to P. monophylla. Individuals with intermediate morphology have been observed in their contact zones, leading some to believe they also hybridize. In this study, we used morphological and next-generation genomic data to test for hybridization, detect the direction of gene flow, and determine the extent of the hybrid zones. We examined the entire Southwestern range of these three pinyon pine species, to determine the evolutionary patterns of gene flow between and among species, ultimately discovering the extent of hybridization and its consequences. Using SNPs, we calculated the fixation index (F_ST) to determine population differentiation by genetic structure. Genetic population clustering was determined using the software STRUCTURE and a Discriminant Analysis of Principal Components (DAPC) in R. A network analysis using SplitsTree allowed for phylogenetic reconstruction while considering gene flow. The four-taxon D-statistic test, ABBA-BABA, will be implemented to distinguish between hybridization and incomplete lineage sorting. MIGRATE and Treemix will be used to examine the magnitude and direction of gene flow during ancient admixture events. Our F_ST, DAPC, network analyses, and STRUCTURE results support P. edulis and P. monophylla being independent species, californiarum-type possibly being a result of hybridization between the two, and fallax-type possibly being its own species. Our chloroplast PCA results suggest that californiarum-type, fallax-type, and P. edulis chloroplasts arise from the same evolutionary lineage, while P. monophylla and P. quadrifolia arise from independent chloroplast lineages, except for those in contact zones. These contrasting chloroplast-nuclear data show a potential chloroplast capture event, supporting the hypothesis that hybridization occurred. Preliminary morphological analyses suggest P. edulis and fallax-type do not significantly differ in resin canal number; yet californiarum-type has significantly more resin canals than all other needle types, contrasting the genetic results.

1 - 1720 Avondale Drive, Roseville, CA, 95747, United States
2 - Northern Arizona University, Biology, 1899 S San Francisco Street, Flagstaff, AZ, 86011, USA
3 - Northern Arizona University, Department Of Biological Sciences, 617 S Beaver Street, Flagstaff, AZ, 86011, United States
4 - 4319 Yale Ave, La Mesa, CA, 91942, United States

Keywords:
pinyon pines
hybridization
Next Generation Sequencing
gene flow
morphology.

Presentation Type: Oral Paper
Session: HYHY1, Hybrids and Hybridization
Location: Tucson H/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 10:15 AM
Number: HYHY1007
Abstract ID:989
Candidate for Awards:Margaret Menzel Award