Dispersal in a metapopulation of the critically endangered Danube Clouded Yellow butterfly Colias myrmidone: implications for conservation

Abstract

Colias myrmidone has suffered a dramatic decline in Europe, and now its occurrence is restricted to just a few countries. We investigated one of the last viable metapopulations (Knyszyn Forest, NE Poland), where the butterfly is almost completely dependent on forestry, inhabiting some clearings and young tree plantations rich in larval food plants (Chamaecytisus ruthenicus) and nectar resources. Intensive mark-recapture studies were performed in 2017 on eight occupied patches separated by 0.5-5 km. The overall population size of imagoes in the second brood was calculated at about 750 individuals. Sex ratio was shown to be well-balanced and average residency was estimated at 5.6 days. Dispersal occurred mostly between neighbouring patches, and isolation of patches contributed to the high mortality of emigrants. The average distance covered during dispersal was significantly higher for males. However, females left small patches much more readily than males. These patches were probably used only as 'stepping stone' sites in dispersal. Restricted dispersal could be related to barriers created by forest stands but it is also not excluded that individuals living in an isolated metapopulation become increasingly sedentary and our results are an early warning sign. The most distant local population was clearly isolated, with hardly any immigration from the other populations. To maintain a network of more stable habitat patches some clearings should be left deforested and appropriately managed. However this goal is difficult to achieve under the current forestry rules and therefore (re)creation of habitats on other available open areas should be considered.

Mosaic landscapes provide conservation pockets for an endangered species: Colias myrmidone in Romania

“…Overall, little knowledge is available on the mobility of the species (but see Sielezniew et al, 2019); however, experts evaluate Colias species to be strong flyers in general (Bink, 1992;Loos et al, 2014Loos et al, , 2015, which is assumed to relate to their large body size (Kuussaari et al, 2014;Newbold et al, 2010). In our case study areas in Transyl- agricultural practises (Loos et al, 2020).…”

“…While some of the habitat conditions of C. myrmidone , including the occurrence of its hostplant, might be satisfied in forests, we were unable to detect forests as significant land‐cover type for modelling the occurrences of C. myrmidone . The reason for this might be due to a methodological shortcoming in our study design: As previous studies approve closed forests as unsuitable habitat (Sielezniew et al, 2019; Szentirmai et al, 2014), our study design mostly excluded this land cover class for butterfly surveys. Nonetheless, we found evidence for the preferred proximity to forests, which is another information supporting C. myrmidone 's association to habitat mosaics.…”

“…Only few remaining populations across Europe are currently known to scientists and policy makers. We are currently aware of populations in two areas in Poland (Sielezniew et al, 2019), one area in Slovakia on the brink of extinction (Tuharska, K., personal communication) and in three areas as well as some scattered observations in Romania (Loos et al, 2020). Within the article 17 reporting of the Habitats' Directive in the EU, the overall assessment for C. myrmidone in Romania (alpine and continental biogeographical region) is U1 (unfavourable-inadequate) in the latest available period -2018(EEA, 2020.…”

Sexual differences in age-dependent survival and life span of adults in a natural butterfly population

“…Thus we assume that emigration probability, which may affect estimated adult residency time considerably [e.g. 84 ], was so low that the apparent survival estimated by our models was very close to true survival [see also 17 ]. We also note that the longest timespan between first and last captures of the same individual was 38 days in females and 30 days in males, both of which highly exceeded the average estimated life span.…”

Celebrating 50 years of Butterfly Conservation: a special issue on the ecology and conservation of butterflies and moths

“…Research on butterfly populations, particularly on metapopulation structure and habitat quality has led to the development and delivery of landscape scale conservation and urban butterfly ecology initiatives. This broad tradition is maintained in this volume with several papers in this field (Münsch et al 2019;Sielezniew et al 2019;Topp and Loos 2019;Viljur et al 2019;León-Cortés et al 2019).…”