Distance Dependent Contribution of Ants to Pollination but Not Defense in a Dioecious, Ambophilous Gymnosperm
protective mutualism
Pollinator
0106 biological sciences
Ephedra
Anemophily
ant pollination
POLLINATION DROP
Genomic Insights into Social Insects and Symbiosis
Plant Science
Pollen source
01 natural sciences
SB1-1110
DIOECY
Agricultural and Biological Sciences
https://purl.org/becyt/ford/1.6
Biochemistry, Genetics and Molecular Biology
gymnosperm pollination
pollination drop
Genetics
EPHEDRA
ANT POLLINATION
https://purl.org/becyt/ford/1
Pollination
Biology
Ecology, Evolution, Behavior and Systematics
Gymnosperm
Ecology
Ants
Dioecy
Botany
Plant culture
Life Sciences
Strigolactone Signaling in Plant Interactions
15. Life on land
PROTECTIVE MUTUALISM
dioecy
GYMNOSPERM POLLINATION
WIND POLLINATION
FOS: Biological sciences
Herbivore
Pollen
Impact of Pollinator Decline on Ecosystems and Agriculture
Insect
Zoophily
GNETALES
DOI:
10.3389/fpls.2021.722405
Publication Date:
2021-09-08T05:28:54Z
AUTHORS (5)
ABSTRACT
Dioecious plants are obligate outcrossers with separate male and female individuals, which can result in decreased seed set with increasing distance between the sexes. Wind pollination is a common correlate of dioecy, yet combined wind and insect pollination (ambophily) could be advantageous in compensating for decreased pollen flow to isolated females. Dioecious, ambophilous gymnosperms Ephedra (Gnetales) secrete pollination drops (PDs) in female cones that capture airborne pollen and attract ants that feed on them. Plant sugary secretions commonly reward ants in exchange for indirect plant defense against herbivores, and more rarely for pollination. We conducted field experiments to investigate whether ants are pollinators and/or plant defenders of South American Ephedra triandra, and whether their contribution to seed set and seed cone protection varies with distance between female and male plants. We quantified pollen flow in the wind and assessed the effectiveness of ants as pollinators by investigating their relative contribution to seed set, and their visitation rate in female plants at increasing distance from the nearest male. Ants accounted for most insect visits to female cones of E. triandra, where they consumed PDs, and pollen load was larger on bigger ants without reduction in pollen viability. While wind pollination was the main contributor to seed set overall, the relative contribution of ants was distance dependent. Ant contribution to seed set was not significant at shorter distances, yet at the farthest distance from the nearest male (23 m), where 20 times less pollen reached females, ants enhanced seed set by 30% compared to plants depending solely on wind pollination. We found no evidence that ants contribute to plant defense by preventing seed cone damage. Our results suggest that, despite their short-range movements, ants can offset pollen limitation in isolated females of wind-pollinated plants with separate sexes. We propose that ants enhance plant reproductive success via targeted delivery of airborne pollen, through frequent contact with ovule tips while consuming PDs. Our study constitutes the first experimental quantification of distance-dependent contribution of ants to pollination and provides a working hypothesis for ambophily in other dioecious plants lacking pollinator reward in male plants.
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