The structure of plant- pollinator communities: how do breeding systems and dispersal ability relate to plant species role?

ASTEGIANO JULIA; GUIMARAES PAULO ROBERTO JR; CHEPTOU PIERRE-OLIVIER; MASSOL, FRANÇOIS

Londres

Congreso; INTECOL; 2013

When pollination is limited, plant breeding system and dispersal ability may be linked to species ecological specialization on pollinators, as suggested by previous theoretical studies. For instance, non-autonomous self-pollination plants⎯i.e., plants depending on pollinators? visits to produce seeds⎯should interact with a more diverse pollinator assemblage to avoid pollen limitation. Moreover, good-dispersers plants can avoid pollen limitation by dispersing seeds to sites where pollination service is good and thus, can interact with a less diverse pollinator assemblage. Therefore, both plants breeding system and dispersal ability may modulate species role in plant-pollinator community structure and dynamics. In this context, the network approach emerges as a fundamental tool to study plant-pollinator communities and species role within communities. We investigated how the ecological specialization on pollinators and the role on plant-pollinator network structure of plants vary with both species dependence on pollinators and conspecifics to produce seeds and dispersal ability. We compiled information on plant breeding systems and dispersal types or syndromes for 111 species from 8 published plant-pollinator networks. We measured the number of pollinator species interacting with a plant species (plant?s degree), plant contribution to network nestedness (ni), and to within- and among-module connectivity (ci and zi). We compiled these measures for plants that (1) depend on both pollinators and conspecifics to produce seeds (hereafter ?both-dependent?)⎯i.e., self-incompatible and dioecious species ⎯, (2) only depend on pollinators (hereafter ?pollinator-dependent?)⎯i.e., self-compatible and monoecious species⎯ and (3) ?independent plants?⎯i.e., autonomous-self pollinating and agamospermous species⎯. For these three classes, we also informed dispersal modes i.e. species having (a) short-distance ability⎯i.e., barochory, mirmecochory, ballistically-dispersed⎯or (b) long-distance dispersal ability⎯i.e., hidrochory, zoochory and wind-dispersed. ?Both-dependent? species showed higher ecological generalization on pollinators and a higher contribution to among module connection than independent species. Indeed, ?both-dependent? species presented higher contribution to within-module connectivity than both, pollinator-dependent and independent species. The lowest contribution to nestedness was observed in short-distance dispersal ?both-dependent? species that depend on pollinators and conspecifics to produce seeds. The relationship found between plant?s dependence on pollinators and conspecifics for pollen deposition, ecological generalization on pollinators and species role in network structure tends to suggest a high robustness of plant-pollinator networks to pollinator loss. However, the lower contribution to nestedness of short-distance dispersal ?both-dependent? species may suggest higher specificity in the interactions established by these plants. Thus, the loss of pollinator species interacting with short-distance dispersal both-dependent species might have a negative impact on species and interaction diversity in communities.