Abstract Detail

Speciation Mechanisms in Plants

Broz, Amanda [1], Miller, Christopher [2], Randle, April [3], Tovar-Mendez, Alejandro [4], Sianta, Shelley [5], Simpson-Van Dam, Armeda [6], Hahn, Matthew [7], McClure, Bruce [8], Bedinger, Patricia [9].

Mating system transitions alter reproductive isolating barriers.

Mating system transitions from self-incompatibility (SI) to self-compatibility (SC) are common in angiosperms. However, the way in which these transitions impact population differentiation and ultimately shape speciation is not fully understood. We surveyed populations across the entire range of the Andean wild tomato species Solanum habrochaites to better understand genetic and geographic factors that lead to SC, and to examine how mating system transitions impact interspecific and interpopulation barriers. Our analyses suggest that S. habrochaites has undergone at least six independent transitions from SI to SC. At the southern species range margin in central Peru, we identified a single transition to SC which is associated with a specific S-haplotype that encodes a low activity version of the pistil SI factor S-RNase. However, at the northern species range margin in central Ecuador, we identified five distinct SC groups, each associated with unique loss-of-function mutations in S-RNase. This portion of the range encompasses a floristically diverse depression in the Andes known as the Amotape-Huancabamba Zone, and we hypothesize that recurrent selection for SC was driven by reproductive assurance in the fragmented microhabitats of this region. We identified a small area in central Ecuador where there appears to be recent intermixing between two of these SC groups, providing a mechanism by which genetic diversity can increase in SC populations as they come into secondary contact. Most SC populations retained pistil-side interspecific barriers; however, one northern SC group exhibited weakened or absent interspecific barriers which could allow for increased gene flow with sympatric species. We also identified mechanisms that act to strengthen reproductive isolation between populations and could promote divergence of emergent SC populations. In this case, we found that pollen tubes from two distinct SC groups are rejected by pistils of ancestral SI populations. In summary, our results suggest that changes in one or a few genes that impact pollen-pistil reproductive barriers not only facilitate mating system transitions from SI to SC, but they can also promote the divergence of new lineages from progenitor populations, particularly at species range margins.

1 - Colorado State University, Biology, 1878 Campus Delivery, Fort Collins, CO, 80523, United States
2 - Colorado State University, Biology, 1878 Campus Delivery, Fort Collins, CO, 80523-1878, United States
3 - University of San Francisco, Environmental Science, San Francisco, CA, 94143, USA
4 - University of Missouri, Biochemistry, 117 Schweitzer Hall, Columbia, MO, 65211, USA
5 - UC - Santa Cruz, Ecology And Evolutionary Biology, Kay Lab, 130 McAllister Way, Santa Cruz, CA, 95060, United States
6 - Colorado State University, 1878 Campus Delivery, Fort Collins, CO, 80523-1878, United States
7 - Indiana University, Biology and Computer Sciences, Bloomington, IN, 47405, USA
8 - University of Missouri, 117 Schweitzer Hall, Columbia, MO, 65211, United States
9 - Colorado State University, Biology, Biology Department, Colorado State University, Fort Collins, CO, 80523, United States

Keywords:
mating system
self-incompatibility
pollen-pistil interactions
Reproductive Isolation
interspecific interactions
Solanum.

Presentation Type: Colloquium Presentations
Session: C09, Speciation Mechanisms in Plants
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:30 PM(EDT)
Number: C09008
Abstract ID:113
Candidate for Awards:None