The habitat vegetational structure and the success of the blue alcon, Maculinea alcon (Denis & Schiffermüller)

Abstract

In the present work, we report the first reference for blue alcon, Maculinea alcon (Denis & Schiffermüller) (Lepidoptera, Lycaenidae), in Portugal. This butterfly species maintains a complex relationship with its host plant marsh gentian (Gentiana pneumonanthe L., Gentianaceae) and with Myrmica ants in its habitat in Northern Portugal. This study involved a multivariate analysis of the relationship between M. alcon and selected habitat variables aimed at proposing a suitable methodology for the conservation of this species. Three habitats were distinguished in terms of their floristic combinations: density of ferns (more humid and deep soils, Habitat A), size of grasses (left wetlands, Habitat B) and shrubs (productive wetland, Habitat C). In these habitats, several G. pneumonanthe and M. alcon parameters were recorded as well as the number of host ant nests. Taller plants and higher number of Maculinea eggs were observed in the habitats with higher values ofshrubs and grasses cover (Habitats B and C), whereas the higher number of plants was stimulated by higher values of shrub cover (Habitat C). In contrast, more humid soils and low cattle pressures reduce the density of plants and ant nests and, consequently, the presence of Maculinea. However, the existence of ant nests is decreased under herbaceous layers. These results suggest that the right balance between the number of gentians and Myrmica nests will ensure the survival of theM.alcon butterfly. Thus, the management of the ecosystems where these species occur, i.e. the Erica tetralix hygroscopic communities, requires the maintenance of the balance between the grass and the shrub layers in order to ensure the existence of Myrmica nests and, consequently, the survival of M. alcon.

Keywords:

• Ecosystems conservation
• Gentiana pneumonanthe
• Maculinea alcon
• management
• Myrmica ants
• vegetal communities