Abstract Detail

Reproductive Processes

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

Sexual dimorphism, inter-island evolutionary divergence, and diel variation in floral volatiles of wind-pollinated Schiedea globosa (Caryophyllaceae).

Recent evolution of separate sexes and wind pollination from hermaphroditism and biotic pollination may affect how floral scent varies over the course of the day, between sexes, and across reproductively isolated populations. Wind-pollinated species may retain patterns of day-night changes in floral scent used to attract nighttime pollinators in the past, or the patterns may be lost without biotic selection. Sexual dimorphism in floral scent may exist if the sexes experience differential selection and sex expression is linked to scent production. In a geographic radiation, the level of scent divergence may be proportional to genetic and geographic distance. We characterized these axes of intraspecific chemical variation in subdioecious Schiedea globosa, which sequentially colonized older to younger Hawaiian Islands and exhibits low gene flow between islands. Floral volatiles from inflorescences of greenhouse-grown plants (females, males, and hermaphrodites) from twelve populations (four islands) were sampled day and night and analyzed by GC-MS. Differences among groups were identified by canonical analysis of principal coordinates. Relationships between scent dissimilarity and geographic or genetic distance among populations were examined by Mantel tests. Scent emissions changed from day to night across all sexes and populations. At night flowers increased total emission rates through enhanced emissions of several ketones, nitrogen-bearing oximes, and phenylacetaldehyde. Females emitted less total scent per flower but more of some aliphatic compounds than males, and males emitted more ketones and aldoximes than females. Scent composition differed quantitatively among populations during both day and night. Divergence increased with genetic distance for day and night measures of scent for males, but not females. Divergence in scent increased with geographic distance within islands. Overall, Schiedea globosa exhibits differences in floral scent with time of day and with sex expression  despite morphological adaptations consistent with wind pollination and presumed loss of biotic pollination. Surprisingly, few of the night volatiles are shared with two moth-pollinated relatives, suggesting that they are not likely to be vestigial. Further studies of scent production, pollinators, and the phylogenetic relationships within the genus Schiedea may clarify factors influencing the production of floral scents in this presumably wind-pollinated species.

1 - UC Irvine, 321 Steinhaus Hall, Irvine, California, 92697, United States

floral volatiles
Island radiation
sexual dimorphism
genetic distance
scent chemistry
wind pollination.

Presentation Type: Oral Paper
Session: REP1, Reproductive Processes 1
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 10:30 AM
Number: REP1003
Abstract ID:676
Candidate for Awards:None

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