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Snakes: Ecology and Evolutionary Biology
... The total number of offspring may also be constrained due to physiological and mechanical reasons (Roff 1993). For example, carrying too many offspring could effect a fly's ability to fly (Berrigan 1991) and a snakes ability to move (Crews et al. 1988). In lizards it effects ability to climb (Andrews and Rand 1974), to hide in crevices (Vitt 1981), and to run (Garland Jr 1985;Van Damme et al. 1989). ...
How should a parent optimally distribute limited resources among its offspring? This question is as relevant to a mother bird deciding how to allocate food among her chicks as it is to a bacterium dividing high-quality organelles between its daughters. Optimal offspring size theory has long explored the tradeoff between the number and size of offspring in higher organisms. Meanwhile, the emerging field of bacterial aging examines when cells evolve unequal sharing of old cellular components. Our study unifies these two disciplines through a model of resource allocation. This model highlights that the convexity of how resources affect offspring survivorship determines whether even or uneven resource distribution evolves. Based on this, we derive the optimal resource distribution strategies, show that they evolve, and characterize when these strategies are robust to fluctuating environments. These results not only agree with and strengthen existing models, but also provide an organizing framework that enables new predictions. These include the conditions which select for strategies that contain a "runt of the litter."
... For example, a long list of species for sale can be found on the internet, many of which are endangered or CITESlisted (Duarte and Eterovic 2009). Problems resulting from the introduction of exotic species, include the reduction of native populations (Dodd 1987;Dodd 1993;Adams et al. 1994), structural changes in the arrival community (Savidge 1987;Rodda and Fritts 1992;Mertínez-Morales and Cuarón 1999), and the introduction new diseases and parasites in the native species (Reinert and Ruppert 1999;Cunningham et al. 2003;Jones et al. 2008;Ribeiro et al. 2019). Exotic species, especially in the threatened Atlantic Forest, deserve attention from local authorities to determine impacts on native species and to take action to mitigate the presence of exotic species in Brazilian territory. ...
We present a new record of the Asian Mourning Gecko, Lepidodactylus lugubris (Duméril & Bibron, 1836) in the Atlantic Forest of eastern South America. Lepidodactylus lugubris is a widely distributed lizard currently occurring throughout most of the northern Neotropical Region, including the Galapagos and the eastern Pacific islands. Unlike the Amazon Rainforest, which has wide forested cover and essentially diurnal geckos, the threatened Atlantic Forest has had most of its original vegetation removed. The arrival of L. lugubris in the region deserves attention and study, aiming understand the impact of this exotic gecko on the Atlantic Forest native gecko fauna.
... II Herpetologia no Brasil em áreas afastadas da linha do Equador, onde as temperaturas são mais baixas, como é constatado no& FORD, 1987). Informações sobre fecundidade podem ser obtidas a partir de estudos de campo (apalpação de fêmeas) ou de cativeiro (oviposiçõesOxyrhopus guibei, Erythrolamprus aesculapii (PIZZATTO & MARQUES, 2002;MARQUES, 1996a;obs. ...
O estudo da reprodução de serpentes neotropicais tem recebido maior atenção nas últimas décadas, especialmente pelo uso de material de coleções científicas. Esta revisão pretende reunir as principais informações a respeito de aspectos reprodutivos das serpentes brasileiras. Para isso, são definidos, discutidos e exemplificados com espécies de nossa fauna: (1) formas de dimorfismo sexual, (2) tipos de ciclos reprodutivos, estocagem de esperma, ciclos hormonais e de gordura, (3) modos reprodutivos (partenogênese, oviparidade, ovo-retenção e viviparidade), (4) fecundidade, (5) padrões comportamentais de combate, corte e cópula, (6) cópulas múltiplas e (7) relações entre atividade e reprodução.
Abstract Study on reproduction of neotropical snakes has received more attention in the last decades, mainly by using preserved specimens on scientific collections. This brief revision intends to assemble main information about reproduction in brazilian snakes. Thus, we described discussed and exemplified using brazilian snakes: (1) types of sexual dimorphism (2) patterns on reproductive cycles, sperm storage, hormonal and fat cycles; (3) reproductive modes (parthenogenesis, oviparity, egg-retention and viviparity), (4) fecundity, (5) patterns of male-male combat, courtship and mating, (6) multiple mating and (7) relationship between activity and reproduction.
... More generally, males and females within snake populations often differ in the types or sizes of prey they consume, or the season of year during which they feed (e.g. Mushinsky 1987;. It is easy to see how temporal or spatial variation in the availability of a prey type that is used primarily by one sex (and not the other) could generate divergences in growth rate between the sexes. ...
Broad phylogenetic patterns in sexual size dimorphism ( SSD ) are shaped by sex differences in net selection pressures (e.g. sexual selection, fecundity selection, survival selection), but environmental and ecological factors can also affect the expression of SSD .
Discussions of proximate ecological influences on SSD have focused on niche divergence; for example, increase in a prey type used by only one sex can elevate growth rates of that sex but not the other. Food limitation also can generate spatial and temporal variation in SSD . Under restricted prey abundance, curtailed growth may mask SSD even if the optimal size is greater for one sex than the other. Because an increase in food availability elicits increased feeding and growth by the sex that benefits more from increased body size, variation in prey abundance can generate variation in SSD .
We used mark‐recapture methods to study growth rates relative to prey (frog) abundance in two species of sexually dimorphic colubrid snake species in tropical Australia.
In slatey‐grey snakes ( S tegonotus cucullatus ), a species in which larger body size enhances reproductive output in both sexes (because larger males win combat bouts, and larger females produce more/heavier eggs), increased abundance of frogs caused equivalent increases in growth rates in both sexes and hence did not affect SSD . In keelbacks ( T ropidonophis mairii ), a species in which larger size enhances reproductive output in females more than males (reflecting a lack of male–male combat), increased abundance of frogs elicited higher growth rates of females only. Thus, SSD in keelbacks was modified by prey abundance.
Our results show that the magnitude of sex differences in adult body size can be influenced by proximate environmental factors and support the hypothesis of sex‐specific targets for maximum feeding rates.
A lay summary is available for this article.
Snakes have increasingly been bred as pets around the world. Few studies have addressed the reproduction of boid snakes, and no study has addressed their reproductive cycles in captivity. Thus, this paper describes the reproductive aspects of Brazilian boids in captivity. We used ultrasonography to characterize the reproductive cycle of four boid species in captivity in the Southern Hemisphere: the anaconda (Eunectes murinus), the red-tailed boa (Boa constrictor constrictor), the Amazon tree boa (Corallus hortulanus), and the rainbow boa (Epicrates cenchria). Nonvitellogenic follicles occurred from January to December in anaconda and red-tailed boa and for a shorter period from September to February in Amazon tree boa and from January to May in rainbow boa. Vitellogenesis occurred from late June to late March in E. murinus in year-round (12 months), from March to March in Amazon tree boa, from late September to late March in red-tailed boa, and from late March to late September in rainbow boa. Mating occurred from late March to late September in red-tailed boa and rainbow boa and from late September to late March in Amazon tree boa. No mating was observed in anacondas, but a female probably underwent parthenogenesis. Births occurred in July in anaconda and in March to July in Amazon tree boa and from December to March in red-tailed boa and rainbow boa. In males, increases in testicular size were associated with the mating season. Ultrasonography proved to be a safe and noninvasive technique to study the reproductive cycle of giant snakes in captivity.
HIGHLIGHTS
• A method of diagnosing the reproductive phases that determined an ovulatory and gestational development reproductive standard.
• In males was possible to relate the size of the testicles with the reproductive season.
• Ultrasound examination showed an easy and inexpensive method of diagnosis.
A major cause of reproductive failure in birds is nest predation. Predation risk depends on predator type, as predators vary in their ecology and sensory modalities (e.g. visual vs. olfactory). Snakes (generally olfactory predators) are a major nest predator for small birds, with predation strongly associated with warmer temperatures. We investigated nest survival in a ground‐nesting alpine species, the Cape Rockjumper Chaetops frenatus, endemic to the Fynbos mountains in southwestern South Africa.
The evolutionary relationships of the West Indian (W. I.) xenodontine snake assemblage has been considered as either monophyletic or paraphyletic. Allozyme data from protein electrophoresis were used to estimate the phylogeny of the W. I. xenodontine snakes. Forty-two species from 25 genera (mainland and W. I. taxa) were examined. The phylogenetic relationships were estimated using parsimony analyses with successive approximation weighting on the data coded two ways: (1) the allele as the character and (2) the locus as the character. The most parsimonious trees from both coding methods indicated a non-monophyletic W. I. xenodontine assemblage. Three W.I. groups were recovered in both coding methods: (1) Jamaican Arrhyton and Darlingtonia, (2) Uromacer and the Cuban Arrhyton, and (3) Alsophis, Ialtris, and the South American Alsophis elegans. The relationships of Hypsirhynchus, Antillophis and Arrhyton exiguum were unstable. Nomenclatural changes are recommended for Darlingtonia, Arrhyton, Ialtris and Alsophis.
Micrurus surinamensis is an aquatic member of the genus Micrurus. This species is known for its highly specialized venom and distinctive diet, mostly made of aquatic vertebrates. Here, we explore both external (head and body) and skull shape morphologies in M. surinamensis, comparing it with two terrestrial species of the genus (M. lemniscatus and M. spixii) and two aquatic and terrestrial species of distantly related groups. We use both traditional and geometric morphometrics to determine whether the presence of similar traits in head shape morphology is rather the result of adaptive convergences between M. surinamensis and other aquatic species, or whether it is the product of phylogenetic conservatism within the genus. Results from both traditional and geometric morphometrics show that M. surinamensis can be considered convergent with aquatic species, mainly in the skull shape. Micrurus surinamensis differs from the two terrestrial species of Micrurus by having a wider head, smaller distance between nostrils, and a long tail. Geometric morphometric analysis shows that despite having an extremely conserved skull and mandible shape, M. surinamensis shows a longer supratemporal and quadrate bones than in terrestrial Micrurus, indicating a larger gape for this species. A more kinetic skull combined with a larger gape would allow M. surinamensis to feed on fish, which represent larger and wider prey that contrast with the elongate prey, which compose the main diet of species in the genus Micrurus. Our results illustrate the importance of both phylogenetic conservatism and adaptation in shaping species morphology.
Selection on locomotor performance was determined for a series of marked and recaptured individuals from a population of garter snakes (Thamnophis sirtalis fitchi) in Northern California. We measured snake length and mass, burst speed, endurance on a treadmill, and the distance crawled around a stationary circular track. Size-corrected values (residuals) of mass and locomotor performance were generated from the scaling equations of S-V length (SVL). Randomization tests and regressions were used to determine the probability that a trait was a significant predictor of survivorship, and a nonparametric, cubic spline estimate of the fitness function was used to facilitate detection of the patterns of selection. From 275 ("cohort") snakes measured and tested within 8 days of birth in 1985, 79 were recaptured in the spring-summer of 1986 and subsequent years. Birth SVL was the only significant (randomization P = 0.022) predictor of neonatal survival from 1985 to 1986 with directional selection favoring larger individuals. In addition to the lab-born cohort, 382 field-born snakes from all ages in the population were captured, tested, and released during spring-summer 1986. Similar to the 1985 cohort, the survivorship of 37 of 86 neonates from 1986 to 1987 showed no significant relationship with any residual value using any statistical test. Survivorship from 1986 to 1987 for 127 of 250 yearlings (including 32 lab-born cohort snakes) analyzed with the randomization test showed that greater values of both speed (P = 0.007) and distance residual (P = 0.008) significantly favored survival, whereas intermediate values of mass residual (P = 0.006) were significantly more likely to survive. Univariate regressions predicting the survival of yearlings from 1986 to 1987 gave similar results to the randomization test, but in a multiple regression with yearling burst speed residual, distance capacity residual, and a quadratic term of mass residual, distance capacity residual was the least important predictor variable. For the survivorship of 37 of the 113 older snakes, greater burst speed residual significantly favored survival (randomization P = 0.001).
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