Alpine adaptation drives rapid colour evolution in a Batesian mimic.

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Elevational gradients drive significant biodiversity changes, but alpine adaptation drivers are often unclear.
• Batesian mimicry in New Zealand stoneflies offers a model to study color phenotype selection along elevational gradients.
• Previous research suggested melanism is favored in alpine environments, but this study investigates the opposite pattern.

Purpose of the Study:

• To investigate the role of elevational gradients in selecting for melanic versus non-melanic color phenotypes in Aotearoa New Zealand stoneflies.
• To determine the drivers of alpine adaptation in stonefly populations.
• To assess the relationship between mimic and model species abundance across elevational gradients.

Main Methods:

• Genotyping approximately 1500 stonefly specimens across 7 independent stream populations.
• Analyzing color phenotype frequencies (melanic vs. non-melanic) in relation to elevation.
• Quantifying the abundance of the noxious model species (Austroperla) above the alpine treeline.

Main Results:

• Consistently reduced frequencies of dark (melanic) phenotypes were observed in upland versus lowland stonefly habitats.
• Alpine reductions in melanic Zelandoperla frequencies correlated with decreased abundance of the model Austroperla above the alpine treeline.
• The study found an inverse relationship between elevation and melanic phenotype frequency, contradicting prior hypotheses.

Conclusions:

• Shifting ecological interactions, specifically the reduced abundance of the noxious model, can drive rapid evolutionary changes in mimic populations.
• Elevational gradients can influence the dynamics of Batesian mimicry and selection for specific phenotypes over fine spatial scales.
• The findings highlight the importance of considering species interactions when studying adaptation along environmental gradients.