Context-dependent crypsis: a prey’s perspective of a color polymorphic predator

Abstract

Many animals use body coloration as a strategy to communicate with conspecifics, prey, and predators. Color is a trade-off for some species, since they should be visible to conspecifics but cryptic to predators and prey. Some flower-dwelling predators, such as crab spiders, are capable of choosing the color of flowers where they ambush flower visitors and pollinators. In order to avoid being captured, visitors evaluate flowers visually before landing. The crab spider Mecaphesa dubia is a polymorphic species (white/purple color morphs), which inhabits the flower heads of a dune plant, Palafoxia lindenii. Using full-spectrum photography of spiders and flowers, we evaluated how honeybees perceived the spiders at different distances. Using visual modeling, we obtained the chromatic and achromatic contrasts of the spiders on flower heads as perceived by honeybees. Purple morphs were found mainly on the receptacle area and white morphs were equally likely to be found in the flowers and receptacle. According to theoretical modeling, white morphs were visible to honeybees from a distance of 10 cm in receptacle area but appeared to be cryptic in the flower area. Purple morphs were cryptic on the receptacle and less so when they were on the flowers. Spiders on flower heads are predicted to be more easily detected by honeybees using chromatic contrast. Our study shows that the conspicuousness of flower dwelling spiders to honeybees depends on the color morph, the distance of observation, and the position of spider on the flower head.

Evolutionary trade‐offs may interact with physiological constraints to maintain color variation

“…For instance, detection can be affected by the interaction between animal coloration and background complexity (e.g., Dimitrova and Merilaita 2010), or by surface disruption resultant of the contrast between dorsal and abdominal coloration, (e.g., Stevens et al 2009; see also Merilaita et al 2017). It is also possible that color discrimination depends on the visual acuity of the predator, such that over longer distances frogs may not be distinguishable by predators (e.g., Rodríguez-Morales et al 2018). Additionally, coloration could be under frequency dependent selection arising from a predator's search image based on most frequently found colorations (i.e., apostatic selection; Allen and Clarke 1968, Endler 1980, Bond 2007.…”

Avoiding attack: How dune wasps leverage colour and motion to detect their cryptic spider predators

“…Mecaphesa dubia (Araneae: Thomisidae) is a colour-polymorphic spider that is frequently found on these flowerheads, either on top or to the side (i.e., on the receptacle). The most frequent colour morphs were white and purple (Rodríguez-Morales et al, 2018). Microbembex nigrifrons (Hymenoptera: Crabronidae) nests in dunes near vegetation (Evans et al, 2009), and feed on the pollen and nectar of P. lindenii flowers.…”

“…CC-BY-NC 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made The copyright holder for this preprint this version posted March 22, 2021. ; https://doi.org/10.1101/2021.03.20.436281 doi: bioRxiv preprint How dune wasps avoid attack -DRM et al purple (Rodríguez-Morales et al, 2018). Microbembex nigrifrons (Hymenoptera: Crabronidae) nests in dunes near vegetation (Evans et al, 2009), and feed on the pollen and nectar of P. lindenii flowers.…”

“…The problem of detecting ambush predators is commonly faced by pollinating insects that approach flowers harbouring crab spiders (Araneae: Thomisidae) (Morse, 1986). Crab spiders are famously cryptic -- their body colouration blends into the background of the flowers (Thery and Casas, 2009); some species are capable of changing their colour to match the flower (Oxford and Gillespie, 1998) and others are mottled in various shades (Rodríguez-Morales et al, 2018). This crypsis may serve to avoid detection by potential prey (Gavini et al, 2019; Morse, 1986), perhaps by interfering with search image formation.…”

Investigating Defensive Colouration in Nudibranch Molluscs using a Novel Analytical Framework for the Study of Animal Colour Patterns​​​​​​​

“…Problems can arise from both a mix-up of terminology (referring to discrimination when actually meaning detection) or using discrimination thresholds to assess the detectability of objects (e.g. Rodriguez-Morales et al, 2018). In this study, we refer to the task of discriminating a stimulus from its background as a detection task, as this reflects a common use of the achromatic contrast modelling in visual ecology, most prominently when quantifying the efficiency of animal camouflage (e.g.…”