Melanism, body size, and sex ratio in snakes—new data on the grass snake (Natrix natrix) and synthesis

It is postulated that melanism in ectotherms is adaptive by enhancing thermoregulation, subsequent resource acquisition, and growth. Such effects may differ between the sexes as a result of the differential costs of self-maintenance and reproduction, but empirical support for the sex-specific conseq...

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Bibliographic Details
Published in:Die Naturwissenschaften 2020-06, Vol.107 (3), p.22-22, Article 22
Main Authors: Bury, Stanisław, Mazgajski, Tomasz D., Najbar, Bartłomiej, Zając, Bartłomiej, Kurek, Katarzyna
Format: Article
Language:English
Subjects:
Animals
Biomedical and Life Sciences
Body size
Body Size - physiology
Body Temperature Regulation
Colubridae - physiology
Environment
Female
Females
Life Sciences
Literature reviews
Male
Melanism
Natrix natrix
Original Paper
Phenotypes
Pigmentation - physiology
Poland
Predation
Reproduction (biology)
Reproduction - physiology
Sex
Sex Ratio
Sexes
Snakes
Species
Terrestrial environments
Thermoregulation
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Summary:It is postulated that melanism in ectotherms is adaptive by enhancing thermoregulation, subsequent resource acquisition, and growth. Such effects may differ between the sexes as a result of the differential costs of self-maintenance and reproduction, but empirical support for the sex-specific consequences of melanism remains inconsistent. We studied the effects of melanism on body size and sex ratio in a population of the European grass snake ( Natrix natrix ) in SE Poland and also carried out a systematic review of the literature on the consequences of melanism in terrestrial snakes. Melanistic grass snakes of both sexes appeared to be smaller than the typical phenotype, which indicates higher predation pressure and minimal thermal benefits for black individuals. A female-biased sex ratio was observed in the typical phenotype, but not in melanistic snakes, suggesting that the costs for females and/or benefits for males are higher in melanistic individuals. In conjunction with earlier studies, our data indicate that the consequences of melanism may be related to the reproductive mode of species. In viviparous species, melanism tends to improve growth and/or body size and is more frequent in females, whereas the opposite holds for oviparous snakes. Further studies on melanism should examine a wider array of species with different reproductive strategies and traits beyond the usual thermal benefits.
ISSN:0028-1042
1432-1904
DOI:10.1007/s00114-020-01678-x