Comments on the butterfly fauna (Papilionoidea) of Porto Santo (Madeira Archipelago): species list, distribution patterns, and butterfly-plant network

Abstract

Porto Santo (Madeira Archipelago) is a relatively old (11.1 to 14.3 Ma) and small volcanic island in the Atlantic Ocean. The main part of the island is characterised by semiarid climate and xeric vegetation, while the higher altitudes show subhumid conditions. So far, 11 butterfly species (Papilionoidea) have been detected on Porto Santo. The occurrence of Macroglossum stellatarum (Sphingidae) is published for the first time. The butterfly species of Porto Santo are commented and some comparisons with Madeira Island are discussed. The distribution of butterfly species on Porto Santo was studied during March 2017 (Papilionoidea; n = 204). Some observations of previous years were added (n = 21) and Macroglossum stellatarum (Sphingidae; n = 3) was also included. The butterflyplant network was sampled during March 2017 (115 flower visits). Three species (Colias croceus, Pieris rapae and Vanessa cardui) show a wide occurrence on Porto Santo. As an exception, Vanessa vulcania prefers the subhumid regions. Leptotes pirithous, Macroglossum stellatarum, Pararge aegeria (which all newly colonised Porto Santo), and the migratory Danaus plexippus show a scattered distribution. On the whole, 115 butterfly-plant interactions could be recorded. The network shows more plant than butterfly species and is asymmetric: Seven butterfly species used 15 plant species. The butterfly and plant species were interconnected. The woody Echium species, E. nervosum (endemic to the Madeira Archipelago) and E. portosanctensis (endemic to Porto Santo), including hybrids, are key species as nectar resources for Vanessa atalanta, V. cardui, and V. vulcania. Vanessa vulcania could be found only within one grid in the north of the island at an altitude of 235 m a.s.l. Vanessa vulcania is probably a remnant of an earlier time period, where due to lack of human impact larger areas with microforests and in part Apollonias barbujana laurisilva existed.