Patterns of among- and within-species variation in heterospecific pollen receipt: The importance of ecological generalization.
OBJECTIVE
Coflowering plants are at risk for receiving pollen from heterospecifics as well as conspecifics, yet evidence shows wide variation in the degree that heterospecific pollen transfer occurs. Evaluation of patterns and correlates of among- and within-species variation in heterospecific pollen (HP) receipt is key to understanding its importance for floral evolution and species coexistence; however, the rarity of deeply sampled multispecies comparisons has precluded such an evaluation.


METHODS
We evaluated patterns of among- and within-species variation in HP load size and diversity in 19 species across three distinct plant communities. We assessed the importance of phenotypic specialization (floral phenotype), ecological specialization (contemporary visitor assemblage), and conspecific flower density as determinants of among-species variation. We present hypotheses for different accrual patterns of HP within species based on the evenness and quality of floral visitors and evaluated these by characterizing the relationship between conspecific pollen (CP) and HP receipt.


RESULTS
We found that within-species variation in HP receipt was greater than among-species and among-communities variation. Among species, ecological generalization emerged as the strongest driver of variation in HP receipt irrespective of phenotypic specialization. Within-species variation in HP load size and diversity was predicted most often from two CP-HP relationships (linear or exponentially decreasing), suggesting that two distinct types of plant-pollinator interactions prevail.


CONCLUSIONS
Our results give important insights into the potential drivers of among- and within-species variation in HP receipt. They also highlight the value of explorations of patterns at the intraspecific level, which can ultimately shed light on plant-pollinator-mediated selection in diverse plant communities.
4249 Fifth Ave, Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
Gerardo
G
Arceo-Gómez
Department of Tropical Ecology, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xtmakuil, Mérida, Yucatán, México 97000.
Luis
L
Abdala-Roberts
4249 Fifth Ave, Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
Anneka
A
Jankowiak
4249 Fifth Ave, Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
Clare
C
Kohler
4249 Fifth Ave, Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA.
George A
GA
Meindl
Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (EBD-CSIC). Avda. Américo Vespucio s/n, E-41092, Sevilla, Spain.
Carmen M
CM
Navarro-Fernández
Department of Tropical Ecology, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xtmakuil, Mérida, Yucatán, México 97000.
Víctor
V
Parra-Tabla
4249 Fifth Ave, Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 USA tia1@pitt.edu.
Tia-Lynn
TL
Ashman
Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (EBD-CSIC). Avda. Américo Vespucio s/n, E-41092, Sevilla, Spain.
Conchita
C
Alonso
D044822:Biodiversity; D035264:Flowers / Q000502:physiology*; D011058:Pollen / Q000502:physiology*; D054817:Pollination / Q000502:physiology; D012044:Regression Analysis; D013045:Species Specificity
co-flowering community; diversity; ecological generalization; floral specialization; floral visitor assemblage; heterospecific pollen; pollinator sharing