Connectivity within isolation: dispersal, population genetics, and conservation of the rarest European damselfly

Abstract

1. Coenagrion hylas (Trybom, 1899) has a very limited distribution in Europe, lives in very small, isolated populations, has rather specialised habitat demands, and is regarded as the rarest damselfly of Europe.2. Using a combination of capture-mark-recapture and population genetics, we aimed to evaluate the state of the populations in the Tyrolean Lech valley and to test whether exuviae from this species are usable as a DNA source. DNA was extracted from midleg tibiae and exuviae and genotyped with species-specific microsatellite markers. The results from the capture-recapture and the genetic methods were congruent.3. Coenagrion hylas has an unexpectedly high tendency to disperse within the valley, covering distances of up to 30 km, and lives longer than other damselflies, with an average longevity of 12 days and a maximum lifespan of at least 40 days. Low inbreeding coefficients and low ranges of genetic differentiation across sites provide evidence of panmixia, with no clear signs of inbreeding. The current population size is estimated at 1150 males based on the recapture data.4. We further demonstrated that exuviae deliver a sufficient amount of DNA, which will be important for future monitoring. Although C. hylas currently shows appropriate viability at most Lech valley sites, our study indicates that management measurements, such as creating stepping stone habitats, are crucial to maintain the current population status. Given the high dispersal capability of the species, such management measurements seem promising.