Variation in context‐dependent foraging behavior across pollinators

Abstract

Pollinator foraging behavior has direct consequences for plant reproduction and has been implicated in driving floral trait evolution. Exploring the degree to which pollinators exhibit flexibility in foraging behavior will add to a mechanistic understanding of how pollinators can impose selection on plant traits. Although plants have evolved suites of floral traits to attract pollinators, flower color is a particularly important aspect of the floral display. Some pollinators show strong innate color preference, but many pollinators display flexibility in preference due to learning associations between rewards and color, or due to variable perception of color in different environments or plant communities. This study examines the flexibility in flower color preference of two groups of native butterfly pollinators under natural field conditions. We find that pipevine swallowtails (Battus philenor) and skippers (family Hesperiidae), the predominate pollinators of the two native Texas Phlox species, Phlox cuspidata and Phlox drummondii, display distinct patterns of color preferences across different contexts. Pipevine swallowtails exhibit highly flexible color preferences and likely utilize other floral traits to make foraging decisions. In contrast, skippers have consistent color preferences and likely use flower color as a primary cue for foraging. As a result of this variation in color preference flexibility, the two pollinator groups impose concordant selection on flower color in some contexts but discordant selection in other contexts. This variability could have profound implications for how flower traits respond to pollinator‐mediated selection. Our findings suggest that studying dynamics of behavior in natural field conditions is important for understanding plant–pollinator interactions.

Evolution of honest reward signal in flowers

“…Under natural conditions, a pollinator community would be likely to include both types of pollinator. The usability of floral signs obviously varies among pollinator taxonomic groups, given the differences in visual and olfactory systems [29][30][31] and flexibilities in colour or odour preferences owing to associative learning with rewards [32][33][34]. Likewise, the usability of plant locations varies among pollinator groups.…”

Local adaptation mediates floral responses to water limitation in an annual wildflower

“…If, however, pollinators choose among plants based on the number of flowers per plant, the dishonesty of this signal under drought might deter pollinators from continuing to forage on P. drummondii . While there has been no work investigating the role that flower size versus flower number may play in plant choice by pollinators in our system, butterfly pollinators of P. drummondii do discriminate among P. drummondii plants based on other floral traits such as flower color (Hopkins and Rausher, ; Briggs et al., ). Consistency in signal–reward associations promotes pollinator fidelity in other systems (Benitez‐Vieyra et al., ), suggesting the need for future research investigating butterfly preference for flower size and flower number for P. drummondii .…”

“…We used the butterfly‐pollinated annual plant Phlox drummondii (Polemoniaceae) to explore how water availability affects plant floral traits and the role that local adaption plays in drought response. Butterflies use visual cues presented by P. drummondii to choose plants on which to forage (Hopkins and Rausher, , ; Briggs et al., ). Using controlled growing conditions, we experimentally simulated water limitation for Phlox drummondii plants that were grown from seeds collected along a strong moisture gradient in central Texas.…”

The context dependency of pollinator interference: How environmental conditions and co‐foraging species impact floral visitation

“…One of the empirical challenges in understanding the interactions between pollinators is that environmental conditions can drastically change how pollinators behave and interact with conspecifics and other species. For instance, plant–pollinator interactions tend to be contingent on the external conditions pollinators experience (Briggs et al, 2018; Cnaani et al, 2006; Heinrich, 1976). High resource availability—measured in flower density or nectar volume—has been shown to decrease the duration of foraging trips for bumblebees (Westphal et al, 2006) and increase the floral visits (Thomson, 1988; Thomson et al, 1987).…”