Population structure of the last Tomares nogelii (Lepidoptera, Lycaenidae) population in the European Union—A capture‐mark‐recapture study

Effective conservation of highly specialized butterflies in fragmented landscapes requires quantitative estimates of population size, turnover and functional connectivity. Here, we present the first capture–mark–recapture (CMR) survey of the last known metapopulation of Tomares nogelii dobrogensis , a locally monophagous Lycaenid, in northern Dobrogea, Romania. From May to July 2025, six spatially separated colonies were surveyed, recording 832 capture events (638 first captures and 194 recaptures). Apparent survival (Φ) and recapture probability ( p ) were estimated using Cormack–Jolly–Seber models. Population sizes were assessed using the POPAN parameterization of the Jolly–Seber framework. Dispersal was quantified by fitting dispersal kernels to movement distances derived from georeferenced capture histories. Additionally, wing wear was recorded as a surrogate of butterfly age. POPAN models estimated a metapopulation size of 1801 imagines (sum of colonies 1–5) with a pronounced core–periphery structure: 840 imagines in Colony 1, 277–338 imagines in three intermediate colonies and two small satellite colonies with <50 imagines. The observed flight period was 24 May to 24 June (32 days), longer than previously reported. Dispersal between colonies was only observed in three females. Dispersal kernels were heavy‐tailed, with females showing higher probabilities of long‐distance flights than males. Residence times differed among colonies and between sexes, ranging between approximately 1.6 and 5.3 days. Variation in female residence time was consistent with colony‐specific differences driven by emigration and immigration, plausibly linked to external pressures or density‐dependent intraspecific competition. Conservation efforts should prioritize safeguarding the core colony and maintaining stepping‐stone habitat patches.