Plants which live in diverse communities with other species may often share pollinators, which means that their stigmas can receive the pollen from different types of plants as well from individuals of their own species. This “heterospecific” pollen deposition may have consequences for plant reproduction if it clogs up the stigmas and prevents “conspecific” pollen from gaining a foothold. However there’s still relatively little published on this phenomenon and its impact on reproduction, particularly in highly diverse tropical communities across different seasons. In a new study just published in the journal Oikos and led by Sabrina Aparecida Lopes, we have shown that in a Brazilian hummingbird-flower community heterospecific pollen deposition (HPD) shows seasonal patterns. Contrary to expectations, we also found a positive relationship between HPD and reproductive success, which by coincidence has also been shown this month for a high-Andean plant community in this paper just published by Sabrina Gavini and colleagues.
Here’s the full reference and the abstract for our Oikos paper:
Lopes, S.A, Bergamo, P.J, Queiroz, S.N.P., Ollerton, J., Santos, T. & Rech, A.R. (2021) Heterospecific pollen deposition is positively associated with reproductive success in a diverse hummingbird-pollinated plant community. Oikos (in press)
Heterospeciﬁc pollen deposition (HPD) is ubiquitous across plant communities, especially for generalized species which use a diversity of pollinators, and may have negative eﬀects on plant reproduction. However, it is unclear whether temporal changes in the co-ﬂowering community result in changes in HPD patterns. Moreover, community-level studies are required to understand which factors inﬂuence HPD and how the reproduction of diﬀerent species is aﬀected. We investigated the temporal variation of HPD, its relationship with level of specialization on pollinators and ﬂoral phenotypic specialization, and its association with reproductive success (pollen limitation and fruit set) in 31 hummingbird-pollinated plant species in a tropical Campo Rupestre. We found seasonality in HPD, with species ﬂowering in the dry season having greater diversity of heterospeciﬁc pollen on stigmas and a higher frequency of stigmas containing heterospeciﬁc pollen, compared to the rainy season. Stigmas of ecologically generalized species had more heterospeciﬁc pollen, while the relationship for ecologically specialized species depended on ﬂoral phenotype. Surprisingly, and in contrast to theory, we found a positive relationship between HPD and reproductive success. Our results indicate beneﬁts of generalization and facilitation, in which sharing pollinators brings greater reproductive success via increased conspeciﬁc pollen deposition, even if it incurs more HPD. We demonstrated how assessing HPD at a community-level can contribute to understanding the ecological causes and functional consequences of pollinator sharing.
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