DOI: 10.5061/dryad.jq966
title: Data from: Relative density and dispersion pattern of two southern African Asteraceae affect fecundity through heterospecific interference and mate availability, not pollinator visitation rate

description: 1. Since co-flowering plants often share pollinators, their fecundity is
 likely affected by pollen transfer within and among plant species. Changes
 in pollinator visitation rates (e.g. through facilitation or competition
 for pollinators) are usually thought to exert the predominant influence on
 plant fecundity. However, the transfer of conspecific relative to
 heterospecific pollen between individuals may also play an important role.
 Indeed the relative importance of these determinants of fecundity is
 expected to depend on the density, relative abundance and spatial
 arrangement of con- and heterospecifics. 2. We investigated the effects of
 con- and heterospecific density and spatial distribution pattern on
 pollinator visitation and plant fecundity within and between two annual,
 self-incompatible co-flowering species (Dimorphotheca pinnata and Ursinia
 cakilefolia (Asteraceae)) by manipulating their relative abundance,
 overall patch density, and dispersion patterns in experimental arrays in
 Namaqualand, South Africa. We quantified pollinator visitation rates and
 fruit set in arrays of varying density and aggregation. This enabled us to
 determine which mechanism(s) were driving variation of fecundity,
 particularly through their influence on visitation rates, mate
 availability and heterospecific pollen interference. To test whether
 autogamy offers reproductive assurance when individuals are scattered
 amongst a dense population of heterospecifics, we included an autogamous
 species (U. anthemoides) in a separate experiment. 3. We found that
 increased fecundity with increasing conspecific density was not the result
 of higher visitation rates, but rather increased mate availability.
 Furthermore, increased spatial aggregation of conspecifics at low density
 significantly increased fecundity through reduced heterospecific
 interference. 4. In contrast to results for self-incompatible species,
 fruit set in U. anthemoides was consistently high and unaffected by
 scattered distribution patterns. This suggests that autogamy offers
 reproductive assurance when mates are limited and the potential for
 interspecific pollen transfer (IPT) is high. 5. Synthesis. In this study
 of annual daisies, variation in fruit set is primarily driven by factors
 that affect the transfer of conspecific relative to heterospecific pollen,
 independent of pollinator visitation rate. Our findings demonstrate that
 mate limitation and IPT negatively affect fruit set and that these effects
 can be mitigated by intraspecific aggregation and the ability to
 autonomously self-pollinate.
description: De Waal et al Annual
 Asteraceae fruit set and visitation rates experimental
 arraysThis file contains fruit
 set and pollinator visitation rates of three annual Asteraceae
 (Dimorphotheca pinnata, Ursinia cakilefolia, U. anthemoides) in
 experimental arrays with four treatments (LDD = low density, dispersed;
 LDC = low density, clumped; HD = high density; LD = low density), as well
 as hand pollination experiments to establish the breeding system of D.
 pinnata.