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Smith, Gerard [1], Swartz, Mark [2], Spigler, Rachel [3].

Causes and consequences of variation in heterospecific pollen receipt in Oenothera fruticosa.

Heterospecific pollen transfer, the exchange of pollen between co-flowering species, is common in most plant communities, yet the amount of pollen transferred is extremely variable among species. Intraspecific variation in heterospecific pollen (‘HP’) receipt can be even greater, but we have a poor understanding of its causes and fitness consequences in wild populations. We considered how pollinator identity, local floral neighborhood composition, and flowering phenology may contribute to intraspecific variation in HP receipt in Oenothera fruticosa L. (Onagraceae). Specifically, we evaluated the relationship between HP receipt (absolute grain number and proportion of pollen grains) and: visitation by different pollinator functional groups, the proportion of conspecific neighbors, and date of flowering. We further tested whether HP receipt translated into lower seed production. HP is ubiquitous on O. fruticosa stigmas, but the amount received is highly variable and unrelated to conspecific pollen receipt. Visitation by large bees (mostly Bombus) and small flies are associated with lower proportions of HP received, while visitation by smaller bee species increases the amount and proportion of HP a flower received. Visitation by the large fly, Milesia virginiensis, increases the proportion HP receipt. HP receipt is inversely related to the proportion of conspecific flowers in local floral neighborhoods on average, but the strength and direction of this relationship depends on pollinator group. Additionally, later blooming flowers receive greater proportions of HP because of a substantial decrease in the amount of conspecific pollen received later in the season. Naturally occurring levels of HP are sufficient to negatively impact seed set, but high conspecific pollen loads can counteract this detrimental effect. Together, these results indicate that flowering time and local context contribute equally to HP receipt in O. fruticosa, with fitness consequences. We discuss the implications of the relative roles of intrinsic and extrinsic drivers of HP in determining whether a tolerance or avoidance strategy with respect to HP receipt is likely to be adaptive. We predict a tolerance strategy is more advantageous in O. fruticosa, especially given increased conspecific pollen receipt can offset the cost of HP receipt.

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1 - Temple University, Biology, Department of Biology, BioLife Building (015-00), 1900 North 12th Street, Philadelphia, PA, 19122, United States
2 - Pennsylvania Department of Military and Veterans Affairs, Fort Indiantown Gap National Guard Training Center, Annville, PA, 17003, USA
3 - Temple University, Biology, 1900 N 12th Street, Philadelphia, PA, 19122, United States

Heterospecific pollen transfer
Seed set
pollinator visitation
Neighborhood composition.

Presentation Type: Oral Paper
Session: ECO7, Ecology: Reproductive Biology
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:15 PM(EDT)
Number: ECO7002
Abstract ID:614
Candidate for Awards:Ecological Section Best Graduate Student Paper

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