title: Decline of a Rare Moth at Its Last Known English Site: Causes and Lessons for Conservation.
abstract: The conditions required by rare species are often only approximately known. Monitoring such species over time can help refine management of their protected areas. We report population trends of a rare moth, the Dark Bordered Beauty Epione vespertaria (Linnaeus, 1767) (Lepidoptera: Geometridae) at its last known English site on a protected lowland heath, and those of its host-plant, Salix repens (L.) (Malpighiales: Salicaceae). Between 2007 and 2014, adult moth density reduced by an average of 30-35% annually over the monitored area, and its range over the monitored area contracted in concert. By comparing data from before this decline (2005) with data taken in 2013, we show that the density of host-plants over the monitored area reduced three-fold overall, and ten-fold in the areas of highest host-plant density. In addition, plants were significantly smaller in 2013. In 2005, moth larvae tended to be found on plants that were significantly larger than average at the time. By 2013, far fewer plants were of an equivalent size. This suggests that the rapid decline of the moth population coincides with, and is likely driven by, changes in the host-plant population. Why the host-plant population has changed remains less certain, but fire, frost damage and grazing damage have probably contributed. It is likely that a reduction in grazing pressure in parts of the site would aid host-plant recovery, although grazing remains an important site management activity. Our work confirms the value of constant monitoring of rare or priority insect species, of the risks posed to species with few populations even when their populations are large, of the potential conflict between bespoke management for species and generic management of habitats, and hence the value of refining our knowledge of rare species' requirements so that their needs can be incorporated into the management of protected areas.
authors.affiliation: Yorkshire Naturalists' Union Lepidoptera Group, Yorkshire Naturalists' Union, York, United Kingdom.|Butterfly Conservation, Yorkshire Branch, York, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.affiliation: Department of Biology, University of York, York, United Kingdom.
authors.forename: Sinead
authors.initials: S
authors.lastname: Barrett
authors.affiliation: Department of Biology, University of York, York, United Kingdom.
authors.forename: Colin M
authors.initials: CM
authors.lastname: Beale
authors.affiliation: Yorkshire Naturalists' Union Lepidoptera Group, Yorkshire Naturalists' Union, York, United Kingdom.|Department of Biology, University of York, York, United Kingdom.
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Crawford
authors.affiliation: Butterfly Conservation, East Lulworth, Wareham, Dorset, United Kingdom.
authors.forename: Sam
authors.initials: S
authors.lastname: Ellis
authors.affiliation: Department of Biology, University of York, York, United Kingdom.
authors.forename: Tallulah
authors.initials: T
authors.lastname: Gullett
authors.affiliation: Department of Biology, University of York, York, United Kingdom.
authors.forename: Peter J
authors.identifier: http://orcid.org/0000-0002-7346-6560
authors.initials: PJ
authors.lastname: Mayhew
authors.affiliation: Butterfly Conservation, East Lulworth, Wareham, Dorset, United Kingdom.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Parsons
authors.affiliation: Yorkshire Naturalists' Union Lepidoptera Group, Yorkshire Naturalists' Union, York, United Kingdom.|Butterfly Conservation, Yorkshire Branch, York, United Kingdom.
authors.forename: Penny
authors.initials: P
authors.lastname: Relf
authors.affiliation: Department of Biology, University of York, York, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Robertson
authors.affiliation: Natural England, York, United Kingdom.
authors.forename: Julian
authors.initials: J
authors.lastname: Small
authors.affiliation: Butterfly Conservation, East Lulworth, Wareham, Dorset, United Kingdom.
authors.forename: Dave
authors.initials: D
authors.lastname: Wainwright
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D005260:Female; D005843:Geography; D007814:Larva / Q000502:physiology; D008297:Male; D009036:Moths / Q000033:anatomy & histology*; D010944:Plants / Q000469:parasitology; D011157:Population Dynamics; D025341:Principal Component Analysis; D011795:Surveys and Questionnaires; D006113:United Kingdom