Abstract
Polyommatus exuberans is an evolutionarily significant unit (ESU) of the lycaenid butterfly Polyommatus ripartii. This ESU is known to survive at only two sites in the Susa Valley (NW Italy). Lack of correct management, reforestation and frequent wildfires severely threaten this ESU (listed as endangered species in the most recent IUCN Italian Red List). Although the taxonomic rank of this taxon is still debated, current threats could cause extinction of its two remaining populations before its taxonomic rank and its ecology are clarified. We collected data for the first time on this population at the small site of Mompantero (ab. 10 ha). We used butterfly GPS-positioning and the mark-release-recapture (MRR)-method to estimate its population size (269 individuals), sex-ratio (1.36 M/F), lifespan (4.76 days), density (47/ha) and mobility (median 153 and 33 m for males and females, respectively). Both sexes are equally catchable. Catchability increases around midday and decreases during overcast weather. While the size and density of this small population are comparable to those of other endemic Polyommatus species (such as P. humedasae and P. gennargenti), scarce mobility makes its populations isolated and even more seriously threatened.Implications for insect conservationWe suggest that implementing an active management plan, including mowing before July and/or in autumn, and supporting ant diversity, is of immediate importance. Management should be extended to road verges, where the larval host plant (Onobrychis sp.) is abundant, and would thus also serve as corridors to favour dispersion between sites. Our research is the first study to investigate this taxon, thus shedding some light on the ecological and biological aspects that are crucial for long-term survival.
Highlights
Recent research has emphasized a global decline in insect populations during the last 30 years (Collen et al 2012; Dirzo et al 2014; Hallmann et al 2017; Vogel 2017; Lister and Garcia 2018; Sánchez-Bayo and Wyckhuys 2019; Crossley et al 2021)
Little is known about these butterfly species, even if the contribution of rare and endemic species to ecosystems is generally crucial due to their role in ecosystem functioning, which is usually different from common species (Kunin and Gaston 1993; Gaston 2012)
We evaluated the ant communities to see if the ant genara used by P. ripartii were present in the area
Summary
Recent research has emphasized a global decline in insect populations during the last 30 years (Collen et al 2012; Dirzo et al 2014; Hallmann et al 2017; Vogel 2017; Lister and Garcia 2018; Sánchez-Bayo and Wyckhuys 2019; Crossley et al 2021). There is, a high risk of losing these species without even noticing it (McGarrahan 1997; Bonelli et al 2011; Theng et al 2020). Conservation actions, such as habitat protection and restoration, are likely to be effective in opposing the decline of local insect populations (Samways 2007; Forister et al 2019; Haddaway et al 2020; Crossley et al 2021). Policy and management must be supported by reliable knowledge accumulated from diverse sources of evaluated evidence on different aspects of species ecology and phenology
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