Adaptive variation in head size in Vipera berus L. populations

Forsman, Anders

doi:10.1111/j.1095-8312.1991.tb00600.x

Cited by 67 publications

(44 citation statements)

References 33 publications

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“…Mainland Tiger snakes typically produce litters composed of numerous small neonates that feed on a wide range of small prey items (Aubret, 2012). Insularity created a potentially huge mismatch between prey size and neonate swallowing ability (that is, due to drastically different prey assemblages), generating intense selective pressure for an increase in body and head size of neonate snakes (Forsman, 1991;King, 2002;Aubret et al, 2004a; Figure 3 Body mass rates of evolution and levels of adaptive plasticity. Rates of evolution in body mass in grams per generation were significantly correlated with the level of plasticity for head growth in response to prey size calculated for five island populations (linear regression; R 2 ¼ 0.88; F 1, 3 ¼ 21.14; Po0.019).…”

Section: Discussionmentioning

confidence: 99%

Island colonisation and the evolutionary rates of body size in insular neonate snakes

Aubret

2014

Heredity

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Island colonisation by animal populations is often associated with dramatic shifts in body size. However, little is known about the rates at which these evolutionary shifts occur, under what precise selective pressures and the putative role played by adaptive plasticity on driving such changes. Isolation time played a significant role in the evolution of body size in island Tiger snake populations, where adaptive phenotypic plasticity followed by genetic assimilation fine-tuned neonate body and head size (hence swallowing performance) to prey size. Here I show that in long isolated islands (46000 years old) and mainland populations, neonate body mass and snout-vent length are tightly correlated with the average prey body mass available at each site. Regression line equations were used to calculate body size values to match prey size in four recently isolated populations of Tiger snakes. Rates of evolution in body mass and snout-vent length, calculated for seven island snake populations, were significantly correlated with isolation time. Finally, rates of evolution in body mass per generation were significantly correlated with levels of plasticity in head growth rates. This study shows that body size evolution occurs at a faster pace in recently isolated populations and suggests that the level of adaptive plasticity for swallowing abilities may correlate with rates of body mass evolution. I hypothesise that, in the early stages of colonisation, adaptive plasticity and directional selection may combine and generate accelerated evolution towards an 'optimal' phenotype.

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Section: Discussionmentioning

confidence: 99%

Island colonisation and the evolutionary rates of body size in insular neonate snakes

Aubret

2014

Heredity

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“…and A. n. mexicana; for mass r 2 = 0.945, including Porthidium spp. ); these residuals are treated here as relative tail length (RTL) and relative stoutness (RST), respectively (see Forsman, 1991).…”

Section: Methodsmentioning

confidence: 99%

Diversity and evolution of macrohabitat use, body size and morphology in a monophyletic group of Neotropical pitvipers (Bothrops)

et al. 2001

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The Neotropical pitviper genus Bothrops comprises about 40 species, which occur in all main ecosystems of cis-Andean South America. We explored the relationships of body size and form (tail length and stoutness) with macrohabitat use in 20 forms of Bothrops. Semi-arboreal habits appeared only in forest forms. Semiarboreals are signi®cantly more slender and have longer tails than terrestrials; body size is not signi®cantly different between terrestrials and semi-arboreals. Within Bothrops, independent contrasts for macrohabitat use were signi®cantly correlated with contrasts of tail size (positively) and stoutness (negatively); thus, the more arboreal the species, the longer its tail and the more slender its body. Contrasts of adult body size seems to remain constant over the lower range of macrohabitat use, but to decrease in species of Bothrops which are more arboreal. Reconstructions of character states indicate that: (1) the ancestor of Bothrops was a small, stout, terrestrial species; (2) semi-arboreal habits appeared one to three times in the genus; (3) a decrease in stoutness and an increase in tail length occurred along with an increase in arboreality in some clades. Although macrohabitat use seems to be important in determining body form in Bothrops, our results also indicate that tail size, stoutness and body size may also be affected by selective agents other than macrohabitat use. The selective agents responsible for the shifts in macrohabitat use in Bothrops are still uncertain, although they may have included prey availability and/or predation pressure. The plasticity of macrohabitat use, morphology and body size described in this study may have been key features that facilitated the highly successful ecological diversi®cation of Bothrops in South America.

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“…Forsman (1991b) found phenotypic variation in head length among mainland and island populations of Vipera berus. Adders inhabiting islands with large voles Microtus agrestis had longer heads (relative to body size) than adders living on islands with smaller voles.…”

Section: Discussionmentioning

confidence: 85%

Body size plasticity and local variation of relative head and body size sexual dimorphism in garter snakes (Thamnophis sirtalis)

2003

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For snakes, prey size and sex are two possible determinants of head and body size. In garter snakes Thamnophis sirtalis, females are generally longer and have greater body weights than males, and also have larger relative head sizes, which may facilitate foraging success. The selective pressures that account for sexual size dimorphism in garter snakes have not been unequivocally demonstrated. In this study, the body (length and mass) and head (head length, head width, jaw length, inter-ocular distance) sizes of garter snakes inhabiting two nearby but ecologically dissimilar sites with different types of available prey were compared. Overall, the adult female snakes were larger and had greater relative head sizes than males. Males from the two sites did not differ significantly in body or head sizes. However, the mean body length and mass of females from a site where vertebrates are included in the diet were greater than that of females feeding almost exclusively on earthworms. There were also significant site differences in all four head measurements in females, although the direction of the difference varied by site. Diet-induced morphological plasticity is well documented and was evident in this study, although the relative roles of genotype, ontogeny, and competing selective forces in the expression of such plasticity can only be ascertained through future experimental studies.

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Adaptive variation in head size in Vipera berus L. populations

Cited by 67 publications

References 33 publications

Island colonisation and the evolutionary rates of body size in insular neonate snakes

Island colonisation and the evolutionary rates of body size in insular neonate snakes

Diversity and evolution of macrohabitat use, body size and morphology in a monophyletic group of Neotropical pitvipers (Bothrops)

Body size plasticity and local variation of relative head and body size sexual dimorphism in garter snakes (Thamnophis sirtalis)

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