Abstract
Understanding the evolution of specialization in host plant use by pollinators is often complicated by variability in the ecological context of specialization. Flowering communities offer their pollinators varying numbers and proportions of floral resources, and the uniformity observed in these floral resources is, to some degree, due to shared ancestry. Here, we find that pollinators visit related plant species more so than expected by chance throughout 29 plant–pollinator networks of varying sizes, with “clade specialization” increasing with community size. As predicted, less versatile pollinators showed more clade specialization overall. We then asked whether this clade specialization varied with the ratio of pollinator species to plant species such that pollinators were changing their behavior when there was increased competition (and presumably a forced narrowing of the realized niche) by examining pollinators that were present in at least three of the networks. Surprisingly, we found little evidence that variation in clade specialization is caused by pollinator species changing their behavior in different community contexts, suggesting that clade specialization is observed when pollinators are either restricted in their floral choices due to morphological constraints or innate preferences. The resulting pollinator sharing between closely related plant species could result in selection for greater pollinator specialization.
Highlights
Pollinator specialization in communities is often discussed in terms of classic examples of evolutionary adaptations through plant–pollinator coevolution (Faegri and van der Pijl 1979; Fenster et al 2004)
To determine whether phylogenetic signal in floral restric tiveness is a plausible basis for phylogenetic clustering of plants visited by pollinators, we evaluated whether phylo genetic signal for floral restrictiveness is retained in the “pruned” phylogenies that contain only those plants pres ent in a community and whether the strength of signal depended on plant species richness
Mean phylogeny node depth was strongly negatively cor related with community plant species richness (F1,28 = 38.5352; P < 0.0001; R2 = 0.59), indicating that species-poor communities consist of more distantly related species
Summary
Pollinator specialization in communities is often discussed in terms of classic examples of evolutionary adaptations through plant–pollinator coevolution (Faegri and van der Pijl 1979; Fenster et al 2004). Recent studies indicate that the evolution of pollinator spe cialization can be influenced by coexisting plant species (Sargent and Otto 2006), to some extent driven by the level of inefficiency in pollen transfer when pollinators are visit ing numerous plant species (Muchhala et al 2010). These models assume that pollinator sharing between plant spe cies occurs though little is known regarding the determi nants of pollinator sharing (Schiestl and Schlu€ter 2009). Pollinator guilds that can only access unrestrictive floral resources (e.g., open flowers) exploit a subset of the resources exploited compared with more “versatile” pollinators [e.g., pollinators with long tongues that allow access to nectar tubes but may visit “open” flowers (Bastolla et al 2009); see Fig. 1]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
