Is bee-avoidance by bird-pollinated flowers driven by nectar robbing in <em>Erica</em>?

Nectar robbing (consuming nectar from a perforated flower without pollinating) generally negatively affects plant fecundity, and plants exhibit multiple mechanisms in defence. The colour of bird-pollinated flowers that are prone to robbing by bees may consequently be explained by the bee-avoidance hypothesis, proposing that bird-pollinated flowers are less visible to bees than bee-pollinated flowers. This visual avoidance mechanism may co-occur with mechanical avoidance mechanisms; however, flower conspicuousness has not yet been related to nectar robbing rates across multiple species using a combination of comparative methods and field observations. To test the bee-avoidance hypothesis, we quantified conspicuousness and flower visitor rates in multiple congeneric ornithophilous and entomophilous Erica species from South Africa. Visual modelling and Phylogenetic Generalised Least Squares analyses of spectral reflectance of 33 ornithophilous and 31 entomophilous species revealed that bir..., Study species To obtain spectral reflectance and morphological measurements, we collected flowers from 33 ornithophilous (i.e., with bird-pollination traits) and 31 entomophilous (i.e., with insect-pollination traits) Erica species occurring in the Fynbos, South Africa, from both natural habitats and from Kirstenbosch National Botanical Garden (Cape Town) (Fig 1, Table S1). All species are shrubs with bisexual flowers that last several days. We sampled species randomly with respect to phylogeny and colour. For 18 species, we sampled multiple populations, including different colour morphotypes (from different sites, except for two sites that contained multiple morphs of the same species), for a total of 108 populations. This research was approved by South African National Parks (CRC/2016-2017/020—2016/V1) and CapeNature (AAA043-0008-0056). We classified species into pollination syndrome categories based on flower size and shape, but not colour (Rebelo &amp; Siegfried, 1985). We measured ..., # Data from: Is bee-avoidance by bird-pollinated flowers driven by nectar robbing in *Erica*? Dataset DOI: [10.5061/dryad.6djh9w1gz](https://doi.org/10.5061/dryad.6djh9w1gz) ## Description of the data and file structure To obtain spectral reflectance and morphological measurements, we collected flowers from 33 ornithophilous (i.e., with bird-pollination traits) and 31 entomophilous (i.e, with insect-pollination traits) *Erica* species occurring in the Fynbos, South Africa, from both natural habitats and from Kirstenbosch National Botanical Garden (Cape Town) (Fig 1, Table S1). We measured the spectral reflectance of the corollas of at least three fresh flowers and two leaves per population. To quantify the most obvious signal, we measured the colour covering the largest area of the perianth in bi-coloured flowers and the sepals when the sepals covered two-thirds of the corolla. We took measurements indoors using a calibrated spectrophotometer (Ocean Optics Jaz models), with a QR200-...,