Cline Centres Research Articles

Novosibirsk revisited 24 years on: chromosome polymorphism in the Novosibirsk population of the common shrew Sorex araneus L.

A Robertsonian fusion polymorphism in the common shrew (Sorex araneus L.), first described in Academgorodok near Novosibirsk (western Siberia) in 1970-72, was re-examined in 1994-95. The polymorphism in the 1970s involved chromosome arm combinations go, jl, mp and qr, i.e. each of these combinations was present in both a metacentric and a twin-acrocentric state in the population at that time. The twin-acrocentric morph for go occurred at low frequency in 1970-72 and was not observed in 1994-95. The polymorphism for arm combinations jl, mp and qr was still observed in 1994-95 and there was no significant difference in metacentric/twin-acrocentric frequencies compared with the previous sample. This is the third well-documented example in which the chromosome polymorphism in the common shrew has been found to be unchanged over a period of 20+ years. Although the polymorphism for qr may be associated with a chromosomal hybrid zone with a cline centre 200 km away, there is no definitive explanation for the other polymorphisms.

Variation in cuticular hydrocarbons across a hybrid zone in the grasshopperChorthippus parallelus

Two subspecies of the meadow grasshopper Chorthippus parallelus form a hybrid zone across the mountains of the Pyrenees. The subspecies differ, amongst several other traits, in the composition of their cuticular hydrocarbons. These compounds are thought to be involved in chemical communication during courtship. Here we report that cuticular hydrocarbon composition differs between the sexes and that a narrow cline for cuticular hydrocarbons separates the subspecies. The cline centre is displaced 15 km north of the majority of clines reported for other characters. This unusual lack of coincidence is discussed with reference to its possible causes and its consequences for the sexual communication system of Chorthippus parallelus .