Abstract
Climate and weather affect phenological events in a wide range of taxa, and future changes might disrupt ecological interactions. Amphibians are particularly sensitive to climate, but few studies have addressed climatically mediated change in the phenology of closely related species or sexes. Here, we test the hypothesis that changes in spring temperatures result in phenological change among Triturus , and we examine inter‐ and intraspecific differences in response. Coexisting populations of Triturus helveticus and Triturus vulgaris at Llysdinam pond in mid‐Wales (53°12′59″N 3°27′3″W) were monitored using pitfall traps along a drift fence during 1981–1987, and again in 1997–2005. Spring temperature over the same period explained up to 74% of between‐year variability in median arrival date, with a significant advance of 2–5 days with every degree centigrade increase. Changes were greater for males than females of both species, and greater for T. helveticus than T. vulgaris within sexes, resulting in an increasing temporal separation between arrivals of male T. helveticus and all other groups. These data illustrate for the first time how climatic change might have differential effects on sympatric species and on the two sexes.