DOI: 10.5061/dryad.78250
title: Data from: Nectar robbing impacts pollinator behavior but not plant reproduction

description: Trait-mediated indirect effects (TMIEs) refer to interactions in which the
 effect of one species on another is mediated by the behavior of a third
 species. A mechanistic approach that identifies the direction and impact
 of TMIEs can shed light on why different net outcomes are observed in the
 same general phenomena across systems. Nectar robbing has variable net
 effects through TMIEs on animal-pollinated plants across systems, but the
 mechanistic steps underlying this range of outcomes are often unclear. To
 address this knowledge gap, we assessed linkages between nectar robbing,
 pollinator behavior and plant reproductive success in the Andean tree,
 Oreocallis grandiflora. We found that robbing in this system led to lower
 nectar volumes, higher nectar sucrose concentration, and higher nectar
 viscosity, which together negatively impact nectar quality. This drop in
 nectar quality was associated with decreased visitation rates by
 hummingbirds, which might be expected to impact plant reproduction
 negatively by pollen limitation. However, it was also associated with
 increased diversity (Shannon's) and evenness in the pollinator
 community due to reduced visitation by a territorial hummingbird, which
 might be expected to impact reproduction positively via enhanced genetic
 diversity of pollen as non-territorial pollinators forage over greater
 areas. We measured seed set and mass to distinguish the relative intensity
 of these two possible outcomes, but found no detectable effect. We
 tentatively conclude that these two consequences of TMIEs may have
 balanced each other out to yield a neutral net effect of nectar robbing on
 plant reproduction, though other explanations are also possible. This
 study highlights ways in which ecologically important TMIEs may act in
 opposing directions to mask important ecological forces, and underscores
 the continued need for detailed study of the mechanisms through which
 TMIEs operate.
description: brix_robbingplotsBrix readings for flowers sampled from robbing treatment plots, "zc"=closed from all visitors, unrobbed, "ao"=open to all visitors, unrobbed, "er"=robbed, open to all visitors.ov_glmm_nozeroNectar volume data from Oreocallis grandiflora flowers sampled in robbing treatment plots. "ind"= individual tree, "group"=plot, "treat"= robbing treatment ("zc"=closed to all visitors, unrobbed, "er"=open to visitors, robbed, "ao"=open to visitors, unrobbed), "ov" = nectar volume in microliters.visitation_robbedplotsRecords of visits by different hummingbird species to flowers in nectar robbing treatment plots. "ind"=individual tree, "group"=plot, "treat"= treatment ("ao"=open, unrobbed, "er"=open, robbed), "day"=day since flower opening, "visits"=total number of visits per day, "duration"= time in hours that flower was observed, "bin"= presence/absence of visits, "agcu"=Aglaeactis cupripennis, "boma"=boissonneaua matthewsii, "coco"=Colibri coruscans, "covi"= Coeligena violifer, "heam"=Heliangelus amethysticollis, "mety"= Metallura tyrianthina, "unk"= unidentified hummingbird species.maternal reproductionSeed set, mass, and seed length from Oreocallis grandiflora under different nectar robbing treatments. Treatments as follows: "c"=closed to visitors, unrobbed, "er"=open to visitors, robbed, "o"=open to visitors, unrobbed.