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Abstract Detail

Hybrids and Hybridization

Powers, John [1], Sakai, Ann [1], Weller, Stephen [1], Campbell, Diane [1].

Flower scent as a potential reproductive barrier in a Hawaiian plant lineage.

In flowering plants, chemical communication often facilitates pollinator specificity, which may affect whether populations diverge or hybridize. Species possessing divergent floral scents may attract distinct pollinators, limiting interspecific pollen transfer. Conversely, shared volatiles that attract the same pollinator could reduce prezygotic isolation. Furthermore, ability of pollinators to recognize hybrid scent could mediate gene flow between hybrids and parental species. After recombination, hybrids may produce novel volatile compounds, novel blends, or reduced emissions. Alternatively, overlap between hybrid and parental scent could enhance uni- or bi-directional backcrossing and gene flow.
The genus Schiedea (Caryophyllaceae) has radiated rapidly across the Hawaiian Islands, producing interfertile species with diverse pollen vectors (moth, bird, wind, selfing). We investigated the floral scent of two sympatric species from different clades (S. kaalae and S. hookeri) and their artificial hybrids. These species are visited by the same microlepidopteran pollinator, and when artificially pollinated produce viable hybrid seeds and vigorous F1 hybrids in the greenhouse. However, we have no evidence of natural hybridization or past genetic introgression, suggesting other barriers. We hypothesized that the parental species will differ in scent due to their phylogenetic distance yet share volatile compounds to attract their common pollinator, and that hybrid plants will have intermediate floral volatile composition. Alternatively, F1 hybrids could lack attractants and/or produce novel compounds.
We grew S. kaalae, S. hookeri, and F1 hybrids in the greenhouse from seeds and cuttings (n = 25, 23, 34). Floral volatiles were characterized and quantified by dynamic headspace sampling and thermal desorption GC-MS, with overlap determined by qualitative comparison (compounds in ≥4 samples), PERMANOVA, and constrained analysis of principal coordinates (CAP).
Parental species shared 58 of the 113 volatile compounds produced by the two species. As a group, artificial hybrids produced 57 of these 58 shared compounds, 11/17 compounds unique to S. kaalae, 36/36 compounds unique to S. hookeri, and 2 novel compounds. Quantitative scent composition differed between parents, hybrids were intermediate in their scent composition, and hybrids differed from parental species in scent composition. Several compounds (1-octen-3-ol, linalool) are known insect attractants, although attractants may be a single compound or blend of compounds.
Despite sharing a pollinator, parental species differed in floral volatile composition. Implications for isolation are equivocal because the two parental species and hybrids produced both shared and distinct floral volatiles. Future work will identify compounds critical for moth attraction and their role in pre- and post-zygotic reproductive isolation.

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Research website

1 - University Of California Irvine, Department Of Ecology And Evolutionary Biology, 321 Steinhaus Hall, Irvine, CA, 92697, USA

Floral volatiles

Presentation Type: Oral Paper
Session: 22, Hybrids and Hybridization
Location: Sundance 1/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 8:30 AM
Number: 22001
Abstract ID:250
Candidate for Awards:Margaret Menzel Award

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