Ongoing shrinkage and fragmentation in the geographic range of the Natterjack Toad, Epidalea calamita, in Latvia and the East Baltic Region

Abstract

Historical data indicate the presence of two Epidalea calamita population groups in Latvia in the past, one in western Latvia and another connecting populations from Estonia and Lithuania – in central Latvia. Both groups have experienced local extinctions that started after the Second World War in the coastal habitats around developing cities, where there were possible bottlenecks limiting population connectivity. Presently E. calamita’s range in Latvia has become split into four small- to medium-sized population groups with only two of them having connections with populations in neighbouring states, and this has produced major range gaps in Latvia dividing the once variably connected East Baltic E. calamita populations. The process of E. calamita range shrinkage continues, and we suggest that the main risk for population sustainability in the region is a combination of adverse local factors or occasional climate events with poor population connectivity and dispersal barriers.