Natrix

Abstract: Radio transmitters embedded in silicone rubber in elongate, oval, smooth-surfaced packages 50 x 21 x 14 mm or a little larger, were forcefed to 67 snakes of eight species (a 68th snake had an abdominally implanted transmitter), which were then trailed on a day to day basis. Forty per cent of all snakes located had made no movement since the previous day. Average distances, in meters covered per day, were: 142, Pituophis melanoleucus; 51.3, Elaphe obsoleta; 44.7, Crotalus horridus; 28.5, Coluber constrictor; 10, Thamnophis sirtalis; 8, Agkistrodon contortrix; 7, Lampropeltis calligaster; 3.7, Natrix sipedon. Movements were irregular and erratic. For periods of 15-30 days the trailed snakes usually moved progressively farther from their starting points. Three displaced snakes exhibited no homing ability. One female N. sipedon made short, irregular movements typical of resident individuals. A displaced male A. contortrix made an unusually long movement the first night, then settled down to a pattern of short, irregular movements like those of residents. A displaced female C. horridus moved away from the release point but did not travel toward its place of origin approximately 10 km distant.

Abstract: Some aspects of the natural history of snakes of the colubrid genus Natrix have been well studied. With their extensive European distribution and relative abundance, their ecology, reproduction and behaviour are well known. Yet other facets of their biology remain poorly understood. These include knowledge of Natrix phylogeny, hypotheses explaining the current distribution of the three extant members of the genus, and their evolution and relationships. In this study we used molecular data, the nucleotide sequences of four protein-coding mitochondrial genes (3806 bp total), to provide a well-supported phylogeny for the genus Natrix. With these molecular data, evidence from the fossil record, and knowledge of palaeogeological events, we used two approaches in designing a time scale which we used to date the major events in Natrix speciation and intraspecific variation. Our data strongly support a phylogeny for the genus in which N. maura is basal with N. natrix and N. tessellata being sister species. The calibrated molecular clock suggests that N. maura diverged from the common ancestor of the three species 18–27 mya and that N. natrix and N. tessellata diverged 13–22 mya. Although the ranges of these estimates are large they support an early Miocene to late Oligocene origin for the three species. Intraspecific divergence is estimated to have commenced 5.3, 6.0 and 6.7 mya with evolutionary rates of 1 : 1.25 : 1.35% per million years for N. maura, N. natrix and N. tessellata, respectively. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 127–143.