The viperine snake Natrix maura is a common water snake, which forages on aquatic prey such as fish and frogs in Western Mediterranean water bodies. Female viperine snakes collected from three populations at the Iberian Peninsula during the vitellogenesis period were compared. Mean clutch size and range, as well as the slope of the regression between body size and clutch size, did not show differences between populations. In contrast, mean size of enlarged follicles of females collected in May from the Ebro Delta proved significantly smaller than those of females from the Matarranya River (50 km far) and the Granada Depression (500 km far). There were no differences in climatic conditions between areas. However, seasonal variation in food availability was significantly different in the Ebro Delta. In this area, the rice fields are dry in early spring as men control the water flow, and prey are not available. This energetic constraint induced female viperine snakes to adjust reproductive timing according to seasonal availability and to delay vitellogenesis for at least one month. By contrast, other Mediterranean populations exhibited a rather high prey availability from early spring (e.g. Matarranya River), females being in good condition in this season and consequently vitellogenesis starting earlier than in the Ebro Delta. This study illustrates a new case of reproductive plasticity in snakes.
The European Smooth snake, Coronella austriaca Laurenti, 1768, presents a continuous distribution range across central and northern Europe, with isolated fragmented populations in the southern European peninsulas. Up to 814 bp of mitochondrial DNA from 34 specimens were used to determine the phylogeny and biogeography of this species within the Iberian Peninsula. The results indicate that Coronella austriaca presents at least three mtDNA lineages in Iberia that may have originated during the Messinian Salinity Crisis, 5.3-5.9 Ma. Posterior range shifts within the independent clades were facilitated by climatic fluctuations that occurred during the Pleistocene Ice Ages and, in the Iberian Peninsula, created a complex scenario of refugia-within-refugia. The formation of old allopatric lineages during the Messinian followed by shifts in the distribution range during the Pleistocene coincide with what has been reported for other Iberian reptiles and amphibians and highlights the importance of the Southern European Peninsulas as "old" hotspots of biodiversity. Our results also support the more recent view that the accentuated environmental instability occurred during the Pleistocene did not lead to speciation in many animal groups. The subspecific status of C. a. acutirostris is confirmed by the mtDNA analyses.
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