Geographic Variation, Convergent Crypsis and Mimicry in Gopher Snakes (Pituophis melanoleucus) and Western Rattlesnakes (Crotalus viridis)
1985; The Society for the Study of Amphibians and Reptiles; Volume: 19; Issue: 1 Linguagem: Inglês
10.2307/1564420
ISSN1937-2418
Autores Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoWestern North American races of the gopher snake Pituophis melanoleucus share aspects of coloration, pattern and defense behavior with the sympatric rattlesnake Crotalus viridis, and have been suggested to be Batesian mimics. Strong geographic variation in appearance and behavior occurs in Pituophis; in southwestern California the adjacent races P. m. annectens and P. m. catenifer appear to be poor and good mimics of C v. helleri and C. v. oreganus, respectively. Resemblance corresponds to convergence in habitat utilization: analysis of background matching shows that coastal Pituophis and Crotalus are cryptic in different microhabitats, whereas inland populations are cryptic in a shared shortgrass environment. Phenotypic similarity may thus be due to convergence on a common cryptic pattern rather than or in addition to selection for mimicry. Geographic variation in intensity of defense behavior provides evidence for the latter view; Pitu- ophis populations that are dissimilar to C viridis or occur outside its range seldom display an active defense (except as juveniles), whereas those occurring in close association with C. viridis defend vigorously. The importance of mimicry thus varies geographically as a secondary result of selection for cryptic coloration.
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