Determinants of the microstructure of plant–pollinator networks

Abstract

Identifying the determinants of biological interactions in mutualistic networks is key to understanding the rules that govern the organization of biodiversity. We used structural equation modeling and dissimilarities in nine ecological variables to investigate community processes underlying the turnover of species and their interaction frequencies (interaction pattern) among highly resolved plant-pollinator networks. Floral and pollinator community composition, i.e., species identities and their abundances, were strong determinants of the microstructure of pairwise interactions among the networks, explaining almost 69% of their variation. Flower and pollinator traits were directly related to interaction patterns, but were partly masked in the model by shared variance with community composition. Time of year and geographic location, floral and pollinator abundances independent of species identity, and relative abundance of exotic flowers had indirect and relatively weak effects on interaction patterns. Our analyses lead to precise predictions about the processes behind the interaction patterns in mutualistic networks. Future understanding of these processes will be aided by studies that evaluate these predictions experimentally at the network level.

Predicting abundances of plants and pollinators using a simple compartmental mutualistic model

“…This limitation is due to the scarcity of datasets of plantpollinator webs that contain abundances as well as size data about their species. However, datasets containing such morphological traits and phenology are currently being compiled [35]. It would be interesting to apply our methodology to these datasets once they become available.…”

Experimental manipulation of floral scent bouquets restructures flower–visitor interactions in the field

“…Thus, flower traits that function as attractants to mutualists but simultaneously prevent non-pollinating animals from consumption of floral resources (floral filters) increase the reproductive success of plants (Irwin, Adler & Alison 2004;Kessler, Gase & Baldwin 2008;Junker et al 2013). Accordingly, floral filters have been shown to cause a non-random distribution of flower visitors to the plant species available in a community (Junker, H€ ocherl & Bl€ uthgen 2010;Kaiser-Bunbury et al 2014;Junker et al 2013). Floral density or abundance, morphological fit and appropriateness of rewards were often discussed to be responsible for the presence or absence of links in plantpollinator networks (Kaiser-Bunbury et al 2014).…”

“…Accordingly, floral filters have been shown to cause a non-random distribution of flower visitors to the plant species available in a community (Junker, H€ ocherl & Bl€ uthgen 2010;Kaiser-Bunbury et al 2014;Junker et al 2013). Floral density or abundance, morphological fit and appropriateness of rewards were often discussed to be responsible for the presence or absence of links in plantpollinator networks (Kaiser-Bunbury et al 2014). However, few studies have considered the potential for floral scent and other chemical traits to contribute to such network structure (Junker, H€ ocherl & Bl€ uthgen 2010), although their potential as floral filters is undisputed (Kessler, Gase & Baldwin 2008;Raguso 2008b;.…”

Research on mutualisms between native and non-native partners can contribute critical ecological insights

“…As incipient partnerships, novel mutualisms also offer a unique opportunity to assess the relative importance of interaction frequency as driven by abundance, a neutral process, with that of adaptive traits that provide specific mutualistic benefits defined by the niches of their potential partners (Kaiser-Bunbury et al 2014). This comparison is particularly valuable given the rapid increase in abundance of non-native species that become invasive, and the relative importance of these two mechanisms may be dictated by the particular stage of spread of a non-native species (Fig.…”