Diversifying selection and color-biased dispersal in the asp viper.

BACKGROUND: The presence of intraspecific color polymorphism can have multiple impacts on the ecology of a species; as a consequence, particular color morphs may be strongly selected for in a given habitat type. For example, the asp viper (Vipera aspis) shows a high level of color polymorphism. A blotched morph (cryptic) is common throughout its range (central and western Europe), while a melanistic morph is frequently found in montane populations, presumably for thermoregulatory reasons. Besides, rare atypical uniformly colored individuals are known here and there. Nevertheless, we found in a restricted treeless area of the French Alps, a population containing a high proportion (>50%) of such specimens. The aim of the study is to bring insight into the presence and function of this color morph by (i) studying the genetic structure of these populations using nine microsatellite markers, and testing for (ii) a potential local diversifying selection and (iii) differences in dispersal capacity between blotched and non-blotched vipers. RESULTS: Our genetic analyses support the occurrence of local diversifying selection for the non-blotched phenotype. In addition, we found significant color-biased dispersal, blotched individuals dispersing more than atypical individuals. CONCLUSION: We hypothesize that, in this population, the non-blotched phenotype possess an advantage over the typical one, a phenomenon possibly due to a better background matching ability in a more open habitat. In addition, color-biased dispersal might be partly associated with the observed local diversifying selection, as it can affect the genetic structure of populations, and hence the distribution of color morphs

Morphological variation of Philodryas patagoniensis (Girard, 1858) (Serpentes, Dipsadidae) from Brazil, based on the study of pholidosis, coloration and morphometric features

Abstract The current study aimed to verify the relationship between the patterns of coloration, the morphometrical features and pholidosis of specimens of Philodryas patagoniensis from Brazil, with the sexual dimorphism of this species. We studied specimens of P. patagoniensis deposited in several herpetological collections from Brazil. A total of 355 specimens were analyzed, of these 145 were males (87 adults and 58 juveniles) and 210 were females (134 adults and 76 juveniles). Adult specimens exhibit sexual dimorphism in snout-vent length, tail length, head length, number of ventral shields, and number of subcaudal shields. The analysis of variance showed that the adult females are significantly longer than adult males, both at snout-vent length and tail length. Females have a greater number of ventral shields (138-210) than males (151-200). The specimens studied also exhibit two distinct patterns of coloration unrelated to geographical or sexual variations

Monitoring and Assessment of the Distribution of the Dice Snake in Ticino, Southern Switzerland

Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrubtion range and hence overestimating the species threat status: we therefore used a model based on a mark-recapturelike approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site. We observed local decline or extinction of some small populations located on secondary streams, apparently because of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno, Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. Therefore, the status of Natrix tessellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these species is adequate because of the small area occupied at national level (IUCN criteria B2a, B2b (iii, iv)) and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of dice snakes populations in Ticino, Switzerland, will now be based on the collected data

Monitoraggio della Biscia tassellata, Natrix tessellata (Laurenti, 1768) nel Cantone Ticino (Svizzera)

ITALIAN: Sulla base dei dati raccolti durante due anni di monitoraggio abbiamo valutato la distribuzione attuale delle popolazioni ticinesi di Biscia tassellata (Natrix tessellata). La valutazione è stata effettuata tenendo conto del fatto che il mancato rilevamento della specie sul campo non indica necessariamente una sua assenza: infatti, grazie ad un modello basato su un approccio di tipo mark-recapture, abbiamo calcolato la probabilità di rilevamento, che risulta pari al 61.2% (± 6.8%), e la proporzione di siti occupati, pari al 78.0% (± 7.9%) dei siti conosciuti. Localmente, alcune piccole popolazioni situate lungo corsi d’acqua secondari appaiono soggette a dinamiche di regressione o estinzione, probabilmente in seguito al deterioramento della qualità degli habitat. Al contrario, le popolazioni che si trovano sulle rive dei laghi (Verbano e Ceresio) e sui corsi d’acqua principali (Ticino, Brenno, Maggia, Vedeggio e Tresa) sono ben distribuite sul territorio e caratterizzate da effettivi localmente abbondanti. La situazione è dunque da considerare sostanzialmente stabile. Lo statuto di specie minacciata secondo la Lista Rossa è tuttavia pienamente giustificato per N. tessellata, soprattutto considerate l’esiguità dell’area occupata a livello svizzero e la fragilità degli ambienti acquatici ai quali essa è strettamente legata. I dati raccolti in questo studio saranno utilizzati per l’allestimento di un piano d’azione specifico per la conservazione delle popolazioni di N. tessellata in Ticino. ENGLISH: Based on two years of field work, we surveyed the distribution of Dice Snakes (Natrix tessellata) populations in the Canton of Ticino (Switzerland). Imperfect detection has been taken into account in order to avoid underestimation of the species range: we therefore used a model based on a mark-recapture-like approach to estimate detection probability, which is 61.2% (± 6.8%), and site occupancy, which is 78.0% (± 7.9%). We observed local declines or extinctions of some small opulations inhabiting secondary streams, apparently because of the habitat deterioration. However, populations located along lakes (Ceresio, Verbano) and main rivers (Ticino, Brenno, Maggia, Vedeggio and Tresa) are widely distributed and show rather high densities. Therefore, the status of N. tessellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these species is adequate because of the small area occupied at national level and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of Dice Snakes populations in Ticino, Switzerland, will now be based on the collected data