Differentiation of the Species of Melinaea and Mechanitis
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Systematic Entomology (1977) 2, 161-197 Geographical patterns of evolution in Neotropid Lepidoptera : differentiation of the species of MeZimea and Mechanitis (Nymphalidae ,Ithomiinae)” KEITH S. BROWN, Jr Departamento de Zoologia, Instituto de Biologia, Universidade Estadual de Campinas, Sao Paulo, Brazil ABSTRACT. Biosystematic analysis incorporating abundant new field data from many parts of the Neotropics has led to an ordered revision of the mimetic ithomiine genera Melinaea and Mechanitis. The various polytypic species of these genera probably served as prime movers for the differentiation of other mimetic butterflies in Quaternary forest refuges. The revisions are presented in the form of supplements to the works of fichard M. Fox on these genera, with analyses based on his divisions. Seven species (or monophyletic species-groups) and sixty- three well-differentiated geographic subspecies (six of these described here for the first time) are recognized in Melinaea. Specimens are illustrated which demonstrate intergradation between refuge-derived subspecies. Five species and fifty-two differentiated subspecies are recognized in Mechanitis, whose members are more abundant and gregarious, more plastic, and apparently more vagile than those of Melinaea, resulting in fewer clear-cut mimetic associations, more exten- sive blurring of differentiation patterns, and apparently fewer incipient biological species in this genus than in Melinaea. Introduction very difficult groups without ever having studied any of the species alive in nature. The mimetic tropical butterfly species in the Unfortunately, it is not always practical to genera Melinaea and Mechanitis (Nymphalidae, effect a reliable analysis of the relationships Ithomiinae) have a confused histoi y of syste- between named forms in these genera without matic arrangements, due primarily to their extensive field work in many different apparent plasticity of colour-pattern and regions. The plasticity of the patterns observed monotony of morphology (d’Almeida, 1951; in these species is probably in part due to Fox, 1949). The speciation patterns in these extensive recent recombination of genes two genera were analysed by Forbes (1924, arising from past differentiations in isolated 1927, 1948), d’Almeida (1951) and Fox forest refuges (Brown et al., 1974; Brown, (1960, 1965, 1967); all three studied a limited 1976a). Large samples must thus be obtained number of specimens. Fox’s genius is amply from a wide variety of localities before any demonstrated by the fact that he succeeded in consistent differentiation patterns become reaching a profound understanding of these apparent. Fortunately, most of the members * Contribution number 12 from the Prograrna de of the genera are common Mullerian models Ecologia, Instituto de Biologia, Universidade Estadual for mimicry rings. Thus, it is possible to de Campinas. obtain long series in many areas, showing the Correspondence: Dr Keith S. Brown, Jr, Departa- mento de Zoologia, Instituto de Biologia, Universi- limits of local polymorphic variation and dade Estadual de Campinas, C.P. 1170, Campinas, intergradation between named taxa; and at Sao Paulo 13,100, Brazil. least a few specimens may be captured almost 161 162 Keith S. Brown. Jr anywhere, helping to suggest the levels of gene in their systematics. Melinaea and Mecharzitis flow between imperfectly isolated geographical species are notable for highly localized occur- races. rence and dramatic fluctuations in population As these widespread and common species levels. Many populations of Melinaea seem to have recently been implicated as prime movers be absent during parts of the year, but reach in the differentiation of other mimetic Lepi- high levels under certain select conditions. In doptera (Brown & Benson, 1974; see also a 1 ha ‘ithomiine pocket’ recently studied in Kaye, 1907), it is especially important that southern Brazil (Brown & Vasconcellos Neto, there exist a complete and detailed under- 1976), mark-recapture experiments indicated standing of their geographical variation, in- that the population level of Mechanitis polym- corporating as much data as possible from the nia casabranca varied over several powers of field and from museum collections. The ten in a period of but 3 months. In the same present analysis attempts to bring up to date study it was shown that this species can move the systematic ordering of the groups presen- rapidly over reasonable distances (at least ted by Fox (1 960, 1965, 1967), in the light of 2 km). Many similar investigations support a recent field data from many areas, museum picture of general demographic instability specimens not examined by Fox, analyses (Brown & Benson, 1974), and reasonably made by d’Almeida, and a modern under- great dispersion ability between sharply standing of the bases for animal differentiation physically bounded populations, for the more in the Neotropics. It is not claimed that this strongly coloured, mimetic ithomiines. Thus, represents a final taxonomic revision, as much it is not surprising that many polymorphic field, insectary, genetic, cytological, physio- populations are known in these genera, with logical, and biochemical work must still be traits appearing in local colonies which undertaken before a complete and definitive apparently have immigrated from regions as comprehension of these groups can be much as thousands of kilometres away. The achieved. Rather, the interpretations are pre- narrow ecological tolerances of ithomiines sented in the light of the patterns discovered have undoubtedly contributed to rapid dif- in the previous analyses of probable Quaternary ferentiation during dryer periods, when the refuges in the Neotropics (Brown et al., 1974; colonies would be widely separated by large Brown, 1976a), which are then used to and essentially impassable areas of dryer vege- suggest solutions for some especially difficult tation, and also to the maintenance of these cases. differentiations in the present day. Moreover, A discussion of the philosophy used in sub- the dispersal abilities of many of the mimetic species designation in relatively sedentary species, especially evident at dawn and dusk polytypic continental species is presented in and on cloudy or very humid days, would the previous paper in this series (Brown, permit a mixing of complex colour-pattern 1976a). That paper also includes a map of elements of the evolved races with consequent the probable Neotropical refuges operative in production of confusingly variable local the last Quaternary dry cycle (and in some populations. These factors are probably the cases, probably still operative today), in the source of much of the difficulty in the syste- differentiation of heliconians and ithomiines; matics of these groups. This problem will be a somewhat revised map (incorporating exten- examined more carefully in some of the cases sive data collected in 1975-76) accompanies discussed in the following sections. this paper. Methodology for species analysis in difficult mimetic groups has been presented Differentiation of the species of Melirzaea with relation to the silvaniform Heliconius (Brown, 1976b). The following analysis of species and races is The demography and ethology of the based on the papers of Fox (1960, 1965), to Ithomiinae have been discussed by many which this constitutes a supplementary revi- authors (see especially Kaye, 1907; Collenette sion. Names within the section headings refer & Talbot, 1928; Fox, 1967; Gilbert, 1969; to the separate species recognized by Fox, in Brown & Benson, 1974;Brown& Vasconcellos the order established by him, except that the Neto, 1976), and are probably very important first name represents the oldest, to be applied Differentiation of Melinaea and Mechanitis 163 to the species as redefined in this analysis. The comma Forbes, romualdo Fox, lucifer Bates, papers of Fox should be read in parallel with lutzi Fox, and eryx d’Almeida is represented the present discussion, as here only important by so few specimens in toto (only comma and new information will be specifically men- Zucifer are moderately frequent in collections) tioned, and only relevant specimens illustrated that it is not strange that the assemblage was (many additional Melinaea have been figured regarded as three separate species by Fox. The by Brown & Benson, 1974). A complete list Andean subspecies (comma and romualdo) of the new ordering of the taxa, with refer- lack the characteristic series of submarginal ences to Fox’s revisions, is given in the Appen- spots present in all the others. The west dix. Amazonian (lucifer) and east Amazonian The species are presented here in proposed (mnasias) types were not known to intergrade; evolutionary order, though the present data Fox remarked that ‘on distributional grounds on this sequence are admittedly sparse. The there would be little objection to combining known entities are united into seven groups, the two as a single species, but the pattern in each of which appears, from present inforrna- lucifer is strongly modified’ (1 960 : 165). Re- tion, to represent a single polytypic species or cently discovered specimens, however, which monophyletic species-group (insectary test include three new subspecies and three impor- crosses have not yet been possible inMelinaea). tant transitional elements, permit a fuller There are four widespread, well-differentiated picture to be drawn of this very widespread Amazonian species; one of these (mnasias) is but rarely encountered, presumably relict