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Adding landscape genetics and individual traits to the ecosystem function paradigm reveals the importance of species functional breadth

  1. Shalene Jhaa,1
  1. aDepartment of Integrative Biology, University of Texas at Austin, Austin, TX 78712;
  2. bMuseo de Invertebrados G. B. Fairchild, Departmento de Zoología, Escuela de Biología, Facultad de Ciencias Naturales Exactas y Tecnología, Universidad de Panamá, 0824-00021, Panama City, Panama
  1. Edited by Peter Kareiva, University of California, Los Angeles, CA, and approved October 16, 2017 (received for review November 22, 2016)

Significance

Pollinators mediate reproductive processes between plants; however, little is known about how plant and pollinator traits impact pollen dispersal and resulting genetic connectivity. Our study quantifies pollen-dispersal distances and pollination effectiveness for individual pollinator species. We demonstrate that seed set is positively driven by pollinator body size, but long-distance pollen dispersal is mediated by both large-bodied and small-bodied bees. We also reveal that individual plant and population attributes impact pollen-dispersal distances and seed production, respectively. Thus, we show that plant and pollinator traits mediate pollination function and that the entire pollinator community, large and small, plays an important role in the maintenance of genetic connectivity.

Abstract

Animal pollination mediates both reproduction and gene flow for the majority of plant species across the globe. However, past functional studies have focused largely on seed production; although useful, this focus on seed set does not provide information regarding species-specific contributions to pollen-mediated gene flow. Here we quantify pollen dispersal for individual pollinator species across more than 690 ha of tropical forest. Specifically, we examine visitation, seed production, and pollen-dispersal ability for the entire pollinator community of a common tropical tree using a series of individual-based pollinator-exclusion experiments followed by molecular-based fractional paternity analyses. We investigate the effects of pollinator body size, plant size (as a proxy of floral display), local plant density, and local plant kinship on seed production and pollen-dispersal distance. Our results show that while large-bodied pollinators set more seeds per visit, small-bodied bees visited flowers more frequently and were responsible for more than 49% of all long-distance (beyond 1 km) pollen-dispersal events. Thus, despite their size, small-bodied bees play a critical role in facilitating long-distance pollen-mediated gene flow. We also found that both plant size and local plant kinship negatively impact pollen dispersal and seed production. By incorporating genetic and trait-based data into the quantification of pollination services, we highlight the diversity in ecological function mediated by pollinators, the influential role that plant and population attributes play in driving service provision, and the unexpected importance of small-bodied pollinators in the recruitment of plant genetic diversity.

Footnotes

  • ?1To whom correspondence should be addressed. Email: sjha{at}austin.utexas.edu.

Published under the PNAS license.

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