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Premise Herbivores directly influence plant reproduction by damaging reproductive tissue which reduces seed production in consumed plants. Consumption of reproductive tissue may also indirectly depress reproduction in unconsumed plants by isolating unconsumed individuals from prospective mates and reducing pollination. However, empirical support for such hypothesized indirect effects remains limited. Methods To investigate potential indirect effects of herbivory on mating opportunities and pollination, we quantified spatial patterns of white-tailed deer (Odocoileus virginianus) herbivory and reproductive outcomes in Lilium philadelphicum (Liliaceae). We mapped 708 flowering plants, monitored deer herbivory, and examined how distance to prospective mates influenced rates of ovule fertilization, a proxy for pollen receipt. Results Most floweringL. philadelphicum plants (83%) failed to produce seed. Deer consumption of flowers prevented seed production in 35% of individuals. The probability of deer herbivory declined with distance to flowering conspecifics. Sixty-five percent of the remaining, unconsumed plants failed to produce seed due to apparent pollen limitation. While ovule fertilization rates declined with multiple predictors quantifying distances to flowering conspecifics, isolation metrics that excluded plants consumed by deer significantly improved predictions of ovule fertilization. Conclusions Our results offer empirical support for the hypothesis that herbivory reduces pollination and seed production in unconsumed plants by altering spatial mating opportunities. This feedback between deer herbivory and distance-dependent pollination contributes to widespread reproductive failure in L. philadelphicum, though the extent to which deer reduce seed production varies with plant isolation. Herbivory may exacerbate pollen limitation in other species by isolating unconsumed plants from prospective mates.
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Trade-offs between deer herbivory and nitrogen competition alter grassland forb composition
Abstract Two of the major factors that control the composition of herbaceous plant communities are competition for limiting soil resources and herbivory. We present results from a 14-year full factorial experiment in a tallgrass prairie ecosystem that crossed nitrogen (N) addition with fencing to exclude white-tailed deer,Odocoileus virginianus, from half the plots. Deer presence was associated with only modest decreases in aboveground plant biomass (14% decrease; −45 ± 19 g m−2) with no interaction with N addition. N addition at 5.44 and 9.52 g N m−2 year−1led to increases in biomass. There were weak increases in species richness associated with deer presence, but only for no or low added N (1 and 2 g N m−2 year−1). However, the presence of deer greatly impacted the abundances of some of the dominant perennial forb species, but not the dominant grasses. Deer presence increased the abundance of the forbArtemisia ludovicianaby 34 ± 12 SE g m−2(94%) and decreased the forbSolidago rigidaby 32 ± 13 SE g m−2(79%). We suggest that these changes may have resulted from trade-offs in plant competitive ability for soil N versus resistance to deer herbivory. Field observations suggest deer acted as florivores, mainly consuming the flowers of susceptible forb species. The preferential consumption of flowers of forbs that seem to be superior N competitors appears to create an axis of interspecific niche differentiation. The overpopulation of white-tailed deer in many tallgrass reserves likely structures the abundance of forb species.
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- Award ID(s):
- 1831944
- PAR ID:
- 10479543
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Oecologia
- Volume:
- 204
- Issue:
- 1
- ISSN:
- 0029-8549
- Format(s):
- Medium: X Size: p. 47-58
- Size(s):
- p. 47-58
- Sponsoring Org:
- National Science Foundation
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