Long-term changes in the geographic distribution and population structures of Osilinus lineatus (Gastropoda: Trochidae) in Britain and Ireland

Since the rate of global climate change began to accelerate in the 1980s, the coastal seas of Britain have warmed by tip to l degrees C. Locations close to the northern range edges of a southern trochid gastropod Osilinus lineatus in Britain previously surveyed in the 1950s and 1980s were resurveyed during 2002-2004 to determine whether changes in the success of near-limit populations had occurred during the period of climate warming. Between the 1980s and the 2000s, the range limits had extended by up to 55 krn. Populations sampled over a latitudinal extent of 4 degrees from northern limits towards the centre of the range showed synchronous increases in abundance throughout the years sampled, suggesting a large-scale factor such as climate was driving the observed changes. These increases in abundance and changes in range limits are likely to have occurred via increased recruitment success in recent years.