Abstract
ObjectivesFloral structures may be warmer than their environment, and can show thermal patterning, where individual floral structures show different temperatures across their surface. Pollinators can differentiate between artificial flowers that mimic both naturally warmed and thermally patterned ones, but it has yet to be demonstrated that these patterns are biologically meaningful. To explore the relationship between pollinators and temperature patterning, we need to know whether there is diversity in patterning, and that these patterns are not simply a by-product of floral architecture constrained by ancestry. We analysed a dataset of 97 species to explore whether intrafloral temperature differences were correlated within clades (phylogenetic signal), or whether the variation seen was diverse enough to suggest that floral temperature patterns are influenced by the abiotic or pollinator-related niches to which plant species are adapted.ResultsSome phylogenetic signal was observed, with both the Asteraceae and species of Pelargonium being more similar than expected by chance, but with other species surveyed not showing signal. The Asteraceae tend to have large temperature differences across the floral surface, which may be due to floral architecture constraints within the family. Other families show no correlation, suggesting that patterning is influenced by pollinators and the environment.
Highlights
Many plant species rely on animal pollinators to transfer pollen between individuals to ensure successful reproduction [1–3]
The data demonstrate that there is relatively little phylogenetic signal in the temperature differences within floral temperature patterns in the 97 species surveyed, suggesting that this trait is unlikely to be constrained by evolutionary history [51, 58]
Since the species were sampled under similar environmental conditions, this suggests that the temperature differences within the patterns are determined by either the life history and selection, environment of the plant, or by the interaction with pollinators, or else the difference within the patterning is random and not subject to selection
Summary
Many plant species rely on animal pollinators to transfer pollen between individuals to ensure successful reproduction [1–3]. Plants produce floral displays that may be detectable by the pollinator across many sensory modalities, including colouration [4–9], scent [10, 11], tactile structure [12, 13], electrostatic charge [14, 15], orientation [16, 17], polarisation of light [18], and humidity [19, 20]. Floral temperature may be another signalling mode. The temperature differences seen are potentially biologically meaningful, as similar differences in the temperature of artificial flowers have been demonstrated to be detectable by bumblebees [27, 28], honeybees [29] and stingless bees [30]. Given that pollinators can detect the temperature differences produced, understanding the role of floral temperature as a potential cue to pollinators is important if we are to understand whether and why flowers produce such complicated multimodal displays [31–33]
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