Abstract Detail

Speciation Mechanisms in Plants

Kalisz, Susan [1], Grant, Alannie-Grace [2], Randle, April [3], Spigler, Rachel [4].

Selfing, niche diversification and species boundaries.

Mating system is the primary determinant of the distribution of genetic variation within and among contemporary populations of a species and plays a central role in species’ capacity for local adaptation, persistence, and evolutionary divergence. Selfing rates can vary among populations within single species, indicating that rapid responses to natural selection on the mating system are common and that the ecological forces that favor selfing or shifts in mating system likely vary among populations. Rapid shifts to high levels of selfing can evolve under strong selection for reproductive assurance, due to pollinator failure or low mate availability, or in extreme environments. Functionally severed from other populations due to drastic reductions in gene flow, highly selfing populations may adapt to novel environments, driving niche divergence and speciation. This same mechanism would also predispose selfers to more rapidly adapt to new conditions, provided sufficient genetic variation. In this case, selfers may be expected to have greater niche breadth. Further, the evolution of selfing may be associated with competition for pollinators between sister species in sympatry. The reduced visitation rates and/or heterospecific pollen transfer can reduce fitness via lower seed set, gamete loss and unfit hybrid offspring production. Under these conditions, selfing may be favored as mechanism to reinforce species’ boundaries. We take diverse approaches to explore hypotheses of how selection can directly or indirectly favor the evolution of selfing and its ties to niche diversification and species boundaries using the self-compatible genera, Collinsia, and its sister, Tonella (Plantaginaceae). These genera present an evolutionarily dynamic study system with repeated mating system transitions from outcrossing to selfing and associated shifts in floral traits that comprise the ‘selfing syndrome’. Using a comparative approach and predictive ecological niche modeling to estimate niche divergence, overlap and breadth for seven sister species, we explored the relationship between selfing or outcrossing and niche breadth. We found that selfers have significantly wider niche breadths and occupy more extreme habitats compared to their outcrossing sisters. These results support the hypothesis that selfing can contribute to a greater capacity to reproduce and adapt to new habitats. Further studies examining sister species in sympatry, we further showed that asymmetric costs of pollinator sharing in sympatry can lead to divergence in selfing rate compared to allopatric populations. Newly developed genomic resources for this model system now pave the way for addressing outstanding questions and gaining unique insights into selfing’s role in speciation.

1 - University of Tennessee, Knoxville, Ecology and Evolutionary Biology, 1416 Circle Drive, Knoxville
2 - University of Tennessee - Knoxville, Knoxville, TN, USA
3 - University of San Fransicso, Environmental Science, San Francisco, CA, 94117-1080 , USA
4 - Temple University, Biology, 1900 N 12th Street, Philadelphia, PA, 19122, United States

Keywords:
selfing
mating system
Collinsia
Niche Modeling
pollination.

Presentation Type: Colloquium Presentations
Session: C09, Speciation Mechanisms in Plants
Location: /
Date: Thursday, July 22nd, 2021
Time: 1:00 PM(EDT)
Number: C09003
Abstract ID:935
Candidate for Awards:None