While it has been long known that plants can respond to abiotic factors like light and precipitation, and more recently it has been shown that they can respond to biotic factors like herbivory and pollinator visitation, it is unclear whether plants can respond to changes in their frugivore community. Given that fruits are costly to create, and that frugivores may be unreliable or inconsistent in most communities, we hypothesize that fleshy-fruited plants should respond to frugivore activity. Specifically, we hypothesized that they could shift their resource allocation towards traits a frugivore may find more attractive. To test whether fruit traits respond to frugivory, we set up a greenhouse experiment with a wild tomato species, Solanum pimpinellifolium, using replicate genotypes and simulating low, medium, and high frugivore visitation levels using three fruit removal treatments. We measured fruit size, seed size, seed number, flesh:seed ratio, and ripening time and tested for differences in these traits across time under different removal treatments.
Results/Conclusions
We found that mean seed number was consistent across treatments, but the variation in seed number increased in low removal treatments over time. The plants in the high frugivory treatment had an overall higher crop yield, suggesting vertebrate dispersers increase plant total fitness. Over time, ripening time was faster in the full removal treatment, compared to no removal. Fruit size was larger in no removal treatments across genotypes, even after adjusting for time spent on the plant in the different removal treatment. The changes we saw were consistent across genotypes, but varied across source accessions, indicating that even within species, there is region-specific responses. This could indicate high plasticity under different natural frugivore frequencies. These results imply that some fleshy fruited plants have the ability to rapidly respond to changes in their frugivore communities in ways that could increase their overall fitness.