Phenotypic diversity, mimicry and natural selection in the African butterfly Hypolimnas misippus L. (Lepidoptera: Nymphalidae)

Abstract

Hypolimnus misippus, a sexually dimorphic, nymphalid butterfly with a very variable female, was sampled for 41 consecutive months, along with its supposed model, Danaus chrysippus (Danaidae), at Dar es Salaam, Tanzania. Hypolimnas larvae collected in the field were reared to compare their range of variation with that of the wild adult population. Some breeding data are presented.Although I show that the colour variations in Danaus and Hypolimnas are remarkably similar, the frequency rankings of the analogous forms within each species differ markedly in the long term. Moreover, 24% of Hypolimnus are transitional forms which are poor mimics. As the range of variation at Dar es Salaam is similar to that reported from Ghana, where the "model" is of quite different appearance, I conclude that mimetic resemblance is not of over-riding importance to its maintenance and perpetuation.The continuous variation in both fore-and hindwing coloration in the field is reflected in reared broods which fail to segregate into discontinuous phenotypes so that H. misippus is not truly polymorphic at Dar es Salaam.Females with transitional forewings have white on their hindwings more often than do the two extreme phenotypes, misippus and inaria. Transitional or white winged females are abundant only at times of high population density, whereas inaria larvae seem t o have an advantage in crowded conditions. The extreme rarity of association between the inaria forewing and white hindwing suggests disruptive selection, the former being associated with the conditions of K selection and the latter with r selection. The calculation of selection coefficients,supports this interpretation, Phenotypic diversity is greatest at high population density when the proportion of poor mimics is also maximal. At these times, apostatic selection may be important. At low density, diversity is minimal.Recent evidence concerning the efficiency of D. chrysippus as a model is discussed. The origin of colour variation in H. misippus probably owed much to mimicry but other selective forces such as apostatic selection or perhaps sexual selection are now of greater importance in maintaining it.

Genetics of the mimetic African butterfly Hypolimnas misippus: hindwing polymorphism

“…Here as previously (Smith, 1976;Gordon, 1982Gordon, , 1987 we use Edmunds' (1969) scoring system for the hindwing which indicates the number of spaces (interveins) affected by the white patch: it ranges from zero (0) (orange) to 10 (almost completely white); scores > 8 are very rare. A complete phenotype classification combines the hindwing score (0-10) with the seven forewing codes (biw, oo and op-brw).…”

“…At first glance it looks like a paradigm case of female-limited polymorphic mimicry. The detailed similarities between the colour patterns of four of its female morphs and the four forms of the distasteful African Queen, Danaus chrysippus (L.), (see colour plate in Smith, 1976) inspired Trimen (1887) to declare it "one of the most exact and unmistakeable cases of mimicry known". Poulton (1912) was prepared to abandon the theory of mimicry altogether if the resemblances between the diadem and the queen could be shown to be "merely accidental".…”

“…sequence and spread in evolutionary time (Clarke, Clarke, Gill, Turner and Collins, 1985). Moreover, field evidence exists for strong, though intermittent, selection on female colour patterns at four different sites on five different occasions: Newton, Sierra Leone, 1966(Unamba, 1968; Legon, Ghana, 1965, 1966(Edmunds, 1969; Dar-es- Salaam, Tanzania, 1974(Smith, 1976Cape Coast, Ghana, 1977 (Gordon, 1982(Gordon, , 1987.…”

Influences of geographic differentiation in the forewing warning signal of the wood tiger moth in Alaska

“…At least one recent study of forewing pattern frequencies across the years showed that fluctuations appeared to be due to genetic drift (O'Hara 2005). Similarly the diversity of warning signals in African Hypolimnas misippus (mimic of Danaus chrysippus) was found to be dependent on temporal fluctuations in population density and other aspects not related to mimicry (Smith 1976). The degree to which temporal stability in coloration and gene flow within populations maintain localized signal diversity represents an area of questions that will be undoubtedly important to answer to fully understand local warning signal diversity.…”

Test of association of morphological variation with heterozygosity in the snail Cepaea nemoralis

“…This type of process presumably accounts for the fact that Batesian mimetic butterflies, in which the visible characteristics are clearly adaptive in the presence of models, may also remain polymorphic in the absence of models. Examples of the complexity of the relation between the mimic/model system and the other selective forces involved are seen in studies of the Hypolimnas misippus/Danaus chiysippus complex (Edmunds, 1969;Smith 1976;VaneWright et a!., 1977;Cook, 1978). Cepaea nemoralis and C. hortensis are species which have advanced northwards with the recession of the ice sheet during the Pleistocene.…”