The status of the African Queen butterfly, Danaus chrysippus (Linnaeus, 1758) (Lepidoptera: Nymphalidae, Danainae), in the Canary Islands, including an irruption on Fuerteventura

Abstract

Examination of museum collections and field work have established that Danaus chrysippus once inhabited five of the seven Canary Islands but is probably now confined to La Palma, La Gomera and Fuerteventura. It may be extinct on Gran Canaria and Tenerife. Before colonisation by the Spanish in the 14th century the food-plants of the relict Canary Island populations were undoubtedly scarce endemic milkweeds (Apocynaceae: Asclepiadoideae). However, on Fuerteventura the recent establishment and subsequent explosive spread of the alien milkweeds Calotropis procera (especially) and Gomphocarpus fruticosus have enabled a massive irruption of the butterfly over the last 20 years. The butterfly population is presently, as it appears always to have been, polymorphic at two unlinked genetic loci which control its colour and are under strong selection. In the African Humid Period of the Holocene, 14,000–5,000 years ago, the Sahara Desert region was green and the island populations were in close proximity to those of North Africa. Thus, there is no evidence that the Canary Island populations of the butterfly have been subject to Founder Effects or prolonged bottlenecks – as is so often the case with isolated island populations. It is suggested that the relict island populations have been periodically introgressed from North Africa and the Cape Verde Islands. There is insufficient evidence to support subspecific status (as D. chrysippus kanariensis Fruhstorfer, 1898) for the present dark-bodied butterflies from the Canary Islands (and St. Helena).