ABSTRACT

Intraspecific color pattern polymorphism (CPP) is widely documented in squamate reptiles and thought to contribute to fitness advantages. Dimorphic striped/spotted CPPs (color pattern dimorphisms [CPDs]) are well characterized among colubrid snakes but are apparently rare among macrostoman lineages. Turks and Caicos Boas (Chilabothrus chrysogaster chrysogaster) are the only booids (superfamily Booidea) known to exhibit a dimorphic striped/spotted CPD within a single population. Based on examination of 737 live wild specimens observed over 12 yr within a population of boas on Big Ambergris Cay, Turks and Caicos Islands, we characterized the striped/spotted CPD and examined potential morphological and spatial correlates of this pattern dimorphism. Contrary to predictions based on studies of similar CPD in colubrid snakes, we found no association between striped or spotted morphs and sex, age, size, or potential morphological correlates. We show that, on average, 15% of the individuals in this population are striped during any given year and that the relative frequency of striped individuals does not appear to change through time, suggesting that the relative frequencies of this polymorphism are stable in this population. Spatial correlation analyses suggested that the striped morph is under-dispersed relative to the spotted morph on Big Ambergris Cay, which might be a product of limited postnatal dispersal or differential habitat preferences. Finally, we described a continuum of color-by-pattern morphs within each pattern class (striped/spotted) in this subspecies which represents a much broader range of color and pattern variation in this species than has been previously recognized.

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