Abstract Detail

Hybrids and Hybridization

Engle-Wrye, Nicholas [1], Mlsna, Todd [2], Folk, Ryan [3].

Investigating conserved pollinator attractants as a driver of hybridization in Heuchera.

      Little is known about environmental drivers of hybridization, but its phylogenetic distribution across plants is heterogeneous, suggesting that plant traits may play a role in its frequency. Conservatism of biotic niche could explain why some plants are prone to hybridization, as conserved pollination strategies would lead to a lack of pollinator assemblage divergence and therefore opportunities for gene flow, although this hypothesis has yet to be tested. The taxonomic tribe Heuchereae (Saxifragaceae) is a well-characterized system for pollinator interactions and particularly for floral scent, the primary pollinator attractant in the group. Floral volatile organic compounds (VOCs) in this clade, characterized to date in Asimitellaria and Lithophragma, are hypervariable at the population level and are responsible for selectivity of specialized pollinator assemblages including parasitic Greya moths, bees, fungus gnats, syrphids, and other insects. High levels of interspecific divergence may be responsible for the relatively low levels of hybridization observed in these groups. Heuchera flowers, by contrast, attract a generalist pollinator assemblage, including pollinators shared with other genera. While floral volatiles have yet to be characterized for this genus, they will offer insight into whether the diversity of prezygotic isolation mechanisms across a recent radiation are predictive of hybridization rate.
     Given that pollinator-mediated gene flow primarily hinges on floral volatile compounds in the relatives of Heuchera, we here investigate whether the particularly high rates of hybridization observed in Heuchera may be associated with low interspecific divergence of these pollinator attractants, using as a system the hybrid zone between H. americana and H. richardsonii in the midwestern US.  We optimized a new closed-space collection and GC-MS (gas chromatography-mass spectrometry) protocol. Preliminary GC-MS data from ~90 Heuchera representing 21 populations suggests that shared classes of VOCs and to some extent individual compounds occur within the hybrid complex while other Heuchera that do not hybridize with these species have distinct species-specific compounds.

1 - Mississippi State University, Biological Sciences, 295 Lee Blvd, Mississippi State, MS, 39762, USA
2 - Mississippi State University, Chemistry, 310 President Cir, Mississippi State, MS, 39762, United States
3 - 295 E. Lee Blvd., P.O. Box GY, Mississippi State, MS, 39762, United States

Keywords:
volatile organic compounds
Hybrids
hybridization
pollinators
Chemical ecology.

Presentation Type: Oral Paper
Session: HH1, Hybrids and Hybridization I
Location: /
Date: Wednesday, July 21st, 2021
Time: 11:30 AM(EDT)
Number: HH1007
Abstract ID:772
Candidate for Awards:None