Quantity and quality components of effectiveness in insular pollinator assemblages

Abstract

Ecologically isolated habitats (e.g., oceanic islands) favor the appearance of small assemblages of pollinators, generally characterized by highly contrasted life modes (e.g., birds, lizards), and opportunistic nectar-feeding behavior. Different life modes should promote a low functional equivalence among pollinators, while opportunistic nectar feeding would lead to reduced and unpredictable pollination effectiveness (PE) compared to more specialized nectarivores. Dissecting the quantity (QNC) and quality (QLC) components of PE, we studied the opportunistic bird-lizard pollinator assemblage of Isoplexis canariensis from the Canary Islands to experimentally evaluate these potential characteristics. Birds and lizards showed different positions in the PE landscape, highlighting their low functional equivalence. Birds were more efficient than lizards due to higher visitation frequency (QNC). Adult lizards differed from juveniles in effecting a higher production of viable seeds (QLC). The disparate life modes of birds and lizards resulted in ample intra- and inter-specific PE variance. The main sources of PE variance were visitation frequency (both lizards and birds), number of flowers probed (lizards) and proportion of viable seeds resulting from a single visit (birds). The non-coincident locations of birds and lizards on the PE landscape indicate potential constraints for effectiveness. Variations in pollinator abundance can result in major effectiveness shifts only if QLC is relatively high, while changes in QLC would increase PE substantially only at high QNC. The low functional equivalence of impoverished, highly contrasted pollinator assemblages may be an early diagnostic signal for pollinator extinction potentially driving the collapse of mutualistic services.

Functional consequences of plant‐animal interactions along the mutualism‐antagonism gradient

“…Opportunistic nectar‐feeding passerine birds and lacertid lizards act as effective pollinators that increase FRS despite the potential for spontaneous autogamy (Rodríguez‐Rodríguez and Valido , Rodríguez‐Rodríguez et al. ). However, the benefits provided by these vertebrate mutualists are counteracted by invertebrate antagonists (florivores, nectar larcenists and predispersal seed predators), which consume and damage reproductive structures (see Appendix : Table S1 for a species list).…”

Pollinator Diversity: Distribution, Ecological Function, and Conservation

“…However the relative effectiveness of different groups of pollinators varies in relation to three components: the abundance of the animal in a community; the propensity for that animal to touch anthers, carry pollen, and contact stigmas; and whether or not the animal will move to a flower of the same species, and the distance it travels in order to do so (Herrera 1987, Rodriguez-Rodriguez et al 2013. The first of these is generally considered a "quantity" measure of pollination; the second and third relate to the "quality" of the pollinator, though all measures are quantitative, and they can be combined to produce indices of pollinator importance for a given plant (e.g.…”

Hotspots of damage by antagonists shape the spatial structure of plant–pollinator interactions

“…Although plants can produce seeds through spontaneous autogamy, their legitimate pollinators (passerine birds and lacertid lizards) significantly increase fruit and viable seed production (Rodrı´guez-Rodrı´guez and Valido 2008, Ollerton et al 2009, Rodrı´guez-Rodrı´guez et al 2013. This species is generally associated with canopy openings, showing a patchy distribution in the laurel and pine forests on the island of Tenerife (ATLANTIS 3.1, available online) 2 .…”