Abstract
The Brown Hairstreak (Thecla betulae L.) is one of the least observed butterflies of the Palaearctic region, even though its distribution spans from Portugal in the west, to Russia and Korea in the far east. Adults are arboreal and seldom descend to ground level. As a result, this species is mostly monitored via the detection of eggs on the food plant during wintertime. In the Iberian Peninsula, this species was largely unknown until very recently, but a recent burst of regional studies in Spain has begun bridging this gap. However, their focused nature and a still incomplete knowledge on T. betulae in Portugal promoted the need for an integrative study at the Iberian scale. Here, we carried out a full literature review on the distribution, ecology and behaviour of T. betulae in Portugal and Spain. Complemented with field work in Portugal, we revealed an almost continuous distribution in the northern third of Iberia, whilst populations further south are mostly mountain-bound. In order to help with future discovery of new populations, we built a species-distribution model relating its occurrence with bioclimatic variables. This model accurately explains the current known occupation of the territory and highlights other areas where the species may potentially be found. Finally, we found evidence of a broadening of the species’ niche through the local use of an hitherto unknown food plant. This study sets a new knowledge baseline for future works and conservation of T. betulae through southern Europe.
Highlights
The Brown Hairstreak, Thecla betulae (Linnaeus, 1758) is a widespread trans-Palaearctic species known from Portugal in the west (Maravalhas et al 2004), to the Pacific coasts of Russia and Korea in the far east (Weidenhoffer and Bozano 2007)
A detailed revision of the literature dealing with T. betulae in Iberia yielded nine papers focused exclusively on this species in the region: Viader (1994), Stefanescu (1997), Stefanescu (2000), Vicente Arranz et al (2013a), Vicente Arranz et al (2013b), Vicente Arranz and Arjona (2014), Antón and Beltzunegi (2015), Mortera (2015) and Salvadores Ramos and Salvadores Ramos (2018)
One study (Dinca et al 2015), delves into the genetics of the species: the authors found only two COI haplotypes in Iberia, among the six scored throughout Europe, in a shallow and non-geographically-structured differentiation pattern
Summary
The Brown Hairstreak, Thecla betulae (Linnaeus, 1758) is a widespread trans-Palaearctic species known from Portugal in the west (Maravalhas et al 2004), to the Pacific coasts of Russia and Korea in the far east (Weidenhoffer and Bozano 2007). This temperate woodland species has its southernmost areas of occurrence in the Iberian Peninsula and northern Turkey (Kudrna et al 2011). The sister species Thecla betulina Staudinger, 1887, which is restricted to the far East of Asia in the Amur, Korea and NE China, is dependent of allied plants but is apparently restricted to Malus manchurica and Pyrus species (Shirôzu 1962; Dantchenko et al 1995)
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