Periodic Reporting for period 1 - MOVAC (Maintenance of variation in aposematic colouration)
Okres sprawozdawczy: 2020-12-01 do 2023-11-30
The research programme outlined in this proposal addresses a key question in evolutionary biology: how diversity in appearance is maintained under natural selection. In particular, the project investigated how colour pattern variation is maintained in species that exhibit warning coloration. This in an especially intriguing area of research because theory predicts that warning signals should look the same in colour and pattern so that they are more easily recognised and avoided by predators. This project investigated this topic using a charismatic polymorphic species of nudibranch mollusc that is common to the coasts of the United Kingdom. Nudibranchs are shell-less marine molluscs with an astounding array of colours and patterns, which they use to either hide from predators (camouflage) or to deter predators by warning them of nasty chemical defenses (warning signals). Nudibranchs are popular spectacles to divers and underwater photographers, yet the anti-predator coloration of this taxon is relatively under-explored. Therefore nudibranchs offer an especially exciting avenue for future research.
The results of this project support the hypothesis that morphs of P. quadrilineata use different modes of protective coloration. While both morphs are camouflaged against natural backgrounds in terms of coloration, they each use different forms of aposematic patterns depending on context. In particular, the dark morph relies distance-dependant aposematism, while the light morph is more traditionally aposematic, with luminance contrast that is visible from a greater distance. Both morphs were equally well defended in terms of their chemical defences against fish predators. There were no differences between morphs in terms of in microhabitat association in the wild or behavioural choice between bryozoan / algae combinations. Diet did not seem to play a role in the development of dark pigmentation in juveniles, suggesting the polymorphism is genetically determined. The results of this research project can be used to inform and shape future theoretical models, which are be applicable to a range of ecological and evolutionary processes. The programme has draw attention to a fascinating and unique species, generating international interest and bringing new insight into Europe's coastal ecosystems.
The results of this project support the hypothesis that morphs of P. quadrilineata use different modes of protective coloration. While both morphs are camouflaged against natural backgrounds in terms of coloration, they each use different forms of aposematic patterns depending on context. In particular, the dark morph relies distance-dependant aposematism, while the light morph is more traditionally aposematic, with luminance contrast that is visible from a greater distance. Both morphs were equally well defended in terms of their chemical defences against fish predators. There were no differences between morphs in terms of in microhabitat association in the wild or behavioural choice between bryozoan / algae combinations. Diet did not seem to play a role in the development of dark pigmentation in juveniles, suggesting the polymorphism is genetically determined. The results of this research project can be used to inform and shape future theoretical models, which are be applicable to a range of ecological and evolutionary processes. The programme has draw attention to a fascinating and unique species, generating international interest and bringing new insight into Europe's coastal ecosystems.
This project explored the niche separation, protective coloration, and chemical defences of the polymorphic nudibranch Polycera quadrilineata through a series of work packages (WPs). Field observations (WP1) revealed no evidence of niche separation between colour morphs, as both morphs were equally distributed across microhabitats. Image analysis demonstrated that both morphs provide camouflage against their natural backgrounds in terms of coloration, with the dark morph showing more effective camouflage in terms of luminance. The dark morph may use distance dependant aposematism, with the black stripes blurring from a distance, but contrasting with yellow and white stripes when viewed in close proximity. Behavioural experiments indicated that fish predators more readily attack the light morph, but both morphs were equally rejected and avoided after initial attacks. Overall, results support different modes of protective coloration, with the light morph more conspicuous against natural backgrounds from a distance, and the dark morph with more contrasting internal patterns when viewed up close.
In WP2, the study examined predation risk and habitat preference, finding no significant differences in microhabitat associations or predator-driven selection between morphs. The light morph was more frequently attacked but survived similarly to the dark morph. Nudibranchs did not display preferences for specific bryozoan-algae combinations, although the light morph showed less inclination to visit seaweed without bryozoans.
WP2 focused on chemical profiling and the “go slow” hypothesis. Conspicuousness and chemical defences were assessed, with the light morph being more visually conspicuous from a distance against natural backgrounds and the dark morph being more conspicuous up close due to high contrast of the internal colour pattern. Both morphs were equally chemically defended to the fish predator Lipophyrs pholis. Ongoing work, delayed due to the COVID-19 pandemic, involves chemical analysis of nudibranch tissue in collaboration with Italian researchers. Due to the COVID-19 delay, additional studies on nudibranch chemical defences and predation strategies were conducted, supporting the “go slow” hypothesis.
In WP2, the study examined predation risk and habitat preference, finding no significant differences in microhabitat associations or predator-driven selection between morphs. The light morph was more frequently attacked but survived similarly to the dark morph. Nudibranchs did not display preferences for specific bryozoan-algae combinations, although the light morph showed less inclination to visit seaweed without bryozoans.
WP2 focused on chemical profiling and the “go slow” hypothesis. Conspicuousness and chemical defences were assessed, with the light morph being more visually conspicuous from a distance against natural backgrounds and the dark morph being more conspicuous up close due to high contrast of the internal colour pattern. Both morphs were equally chemically defended to the fish predator Lipophyrs pholis. Ongoing work, delayed due to the COVID-19 pandemic, involves chemical analysis of nudibranch tissue in collaboration with Italian researchers. Due to the COVID-19 delay, additional studies on nudibranch chemical defences and predation strategies were conducted, supporting the “go slow” hypothesis.
The project significantly impacted the researcher’s career, enhancing her skills, international collaborations, and research profile, leading to new job opportunities and further research prospects. Dissemination of the results was affected by the pandemic, but the researcher successfully shared findings through virtual and in-person conferences and on social media including an invited seminar at a workshop series and a plenary lecture at an international conference. In total, the project has thus far led to three first-author publications, one review paper, and two additional publications in preparation.