Natal philopatry in four European species of dragonflies (Odonata: Sympetrinae) and possible implications for conservation management

In Europe, the species Sympetrum depressiusculum is classified as vulnerable with a high risk of extinction in the wild. It is a habitat specialist, the presumed main reason for its vulnerability is the destruction of its natural habitats. Other causes of its general extinction are unknown. Published information regarding dispersal rate and philopatry is not available, although these are evolutionary strategies that can play key roles in susceptibility to environmental change. We compared the rate of philopatry in S. depressiusculum and three other related, abundant but not endangered species of the same genus (S. sanguineum, S. striolatum, S. vulgatum). We collected data in a very isolated site in the Czech Republic, more than 100 km distant from another known population of the species. Using exuviae collection (total of 6,157 exuviae) and capture-mark-recapture (total of 2,188 adults marked) methods, we acquired data allowing us to compare the numbers of emerged individuals and adults returning to the maternal site. We found a difference of nearly an order of magnitude between the philopatry of S. depressiusculum and the three other species. While in S. depressiusculum philopatry was almost 100 %, in the other species it was < 10 %. We suggest the high rate of philopatry can influence the vulnerability of S. depressiusculum in landscape altered by humans. Strict protection of the natal sites is very important for preserving species having this evolutionary strategy, and reintroductions and translocations should also be undertaken to reduce the extinction risk of this endangered species.