Forest butterflies in West Africa have resisted extinction… so far (Lepidoptera: Papilionoidea and Hesperioidea)

Abstract

An extended study of the 972 forest butterflies (Lepidoptera: Papilionoidea and Hesperioidea) in Africa west of the Dahomey Gap, covering the period 1990–2006, showed that 97% of all species ever recorded from the area were still present in one or more of the remaining forests within the region. This is despite the fact that during the past 150 or so years the forests have shrunk to 13% or less of their original extent, very little of which in pristine condition. The 34 species not recorded during the study period mainly belong to genera and species-groups that are rare, local, or difficult of access—species that any collector would be lucky to find once in a lifetime. A few may actually be “phantom species” or mislabelled butterflies from other parts of Africa. Effectively it seems that no butterfly has yet gone regionally extinct in West Africa. Two-thirds of the 34 species not recorded between 1990 and 2006 were found elsewhere in Africa. This should be a source of pride and encouragement for all concerned with nature conservation in the region. The long-term survival of fauna and flora is wholly dependent on the continued existence of sufficient broadleaf forest in reasonable condition. It is possible that accumulated “extinction debt” will still lead to loss of species, a process that should be closely monitored. The remaining area of forest of high quality is small, fragile and now contained almost exclusively within the formal protected areas systems: its continued conservation is vital. Many challenges still exist and much hard work remains to consolidate the conservation of West African biodiversity.

Appendix 1: butterflies not collected in West Africa between 1990 and 2006

Michel Libert, whose knowledge of African butterflies is monumental, suggested that an appendix of the “missing species” should be included and that a description of the process at arriving at these should be discussed. The listing of the species began in 1993 on a computer operating with just two disk drives, each having a capacity of 700 KB—the automatic back-ups done by my present portable computer would have exhausted the capacity my first machine during the time used to write this paragraph! Of the 970 species included in the survey, almost 800 were recorded during personal field-work between 1993 and 2006, mainly in Ghana and Côte d’Ivoire. For most of this period it was possible to monitor material arriving at the African Butterfly Research Institute, Nairobi (ABRI). Very competent field collectors, especially Peter Walwanda, Malang Malé, Richard Vorgas, and Simon Yevu collected extensively in Guinea-Bissau, Guinea, and Ghana. Haydon Warren-Gash collected extensively in Côte d’Ivoire and also deployed local collectors, especially to the Nimba area (sensu lato) in western Côte d’Ivoire and eastern Guinea. Claudio Belcastro contributed important data from Guinea, Sierra Leone, Côte d’Ivoire, and Ghana. A few additional species were recorded from Ghana by Kühne (1999). By 2006 these activities had brought the total species to 938; it was assumed that these had always been present in West Africa. For the “missing” 34 special attention was paid to establish when they were last recorded from West Africa. Nearly all of these were collected during the 1960 s and 1970 s and are still available in collections, especially those of Father Theodor Maessen from Ghana and T. H. E. Jackson in several museums; many of the Lycaenidae were published by H. Stempffer in numerous publications and personally inspected by the author.

During literature and museum research for the book, a relatively small number of species that were on the first draft lists of West African butterflies were deleted. Thus, Papilio charopus Hewitson, 1843 had been included since its type locality was the Gold Coast [Ghana]. As late as 1990 it was shown from Ghana in a major distributional review of African Papilionidae (Mathot 1990). The species is found only above 1,300–1,500 m in the Cameroun/Nigeria Mountains and its presence in Ghana, where the highest point is just over 800 m, is á priory impossible. This is one of the largest and most characteristic butterflies that cannot have been overlooked for 150 years. Berger (1981) listed Acraea alicia Sharpe, 1890 from Ghana. The butterfly has never again been found in Africa west of the Dahomey Gap and is not even found in the Cameroun/Nigeria Mountains and was taken off the list. Euriphene larseni Hecq, 1994 from Ghana was included in the original list with reservations: in this paper it has been removed as being a junior synonym of E. saphirina, an East/Central African species that must have been mis-labelled. More such changes are discussed by Larsen (2005) as have the many species names dropped in favour of others because of extensive taxonomic revisions. However, deletions from the list are much outnumbered by additional species that were found during the 1990–2006 project period. Some were range extensions of known species: nearly all of these were already known from Nigeria and all of them from Cameroun. As part of extensive revisions of major genera many species new to science were added to the list. All such species are annotated in Larsen (2005). Thus the 34 “missing species” listed in the table below were finally arrived at [six of which refound after submission of the manuscript].

Table 1 The 34 species known from West Africa but not recorded during the 1990–2006 period covered by the extinction study (see Table 2)