Patterned, plain, and in-between: An assessment of ecogeographic divergence between colour pattern morphs of the common egg-eater Dasypeltis scabra

Abstract

Intraspecific variation in colour patterns may reflect adaptive responses to local environmental regimes that favour selection of different trade-offs between visual communication, thermoregulation, and anti-predatory functions. Understanding the drivers of colour pattern variation within species can therefore provide valuable insights about adaptation. However, the ecogeographic correlates, and thus the ecological drivers, associated with the segregation of different colour morphs for most reptile species, including snakes, are not well known. Here, we examined differences in environmental niches associated with occurrence records of preserved museum specimens and georeferenced photographic images of common egg-eaters (Dasypeltis scabra) to characterise ecogeographic divergence between typically patterned, patternless, and faintly marked individuals. We gathered 1707 records that we assigned as either patterned, plain, or intermediate morphs. Most records were of patterned individuals, which were widely distributed in southern Africa. Climate niches differed between morphs as plain and intermediate snakes were restricted to high-elevation areas in the Highveld grasslands of South Africa, and woodland-dominated areas in the central and eastern parts of both Zambia and Zimbabwe, but there were no areas where only plain or intermediate snakes occurred in isolation from patterned snakes. Environmental niche modelling predicted minimal areas suitable for co-habitation of colour morphs. We speculate that plain or weakly-marked colour patterns likely developed as an adaptation to increase camouflage ability in open areas in grassland and certain woodland habitats.