Tera: Papilionidae): Cladistic Reappraisals Using Mainly Immature Stage Characters, with Focus on the Birdwings Ornithoptera Boisduval
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Bull. Kitakyushu Mus. Nat. Hist., 15: 43-118. March 28, 1996 Gondwanan Evolution of the Troidine Swallowtails (Lepidop- tera: Papilionidae): Cladistic Reappraisals Using Mainly Immature Stage Characters, with Focus on the Birdwings Ornithoptera Boisduval Michael J. Parsons Entomology Section, Natural History Museum of Los Angeles County 900 Exposition Blvd., LosAngeles, California 90007, U.S.A.*' (Received December 13, 1995) Abstract In order to reappraise the interrelationships of genera in the tribe Troidini, and to test the resultant theory of troidine evolution against biogeographical data a cladistic analysis of troidine genera was performed. Data were obtained mainly from immature stages, providing characters that appeared to be more reliable than many "traditional" adult characters. A single cladogram hypothesising phylogenetic relation ships of the troidine genera was generated. This differs markedly from cladograms obtained in previous studies that used only adult characters. However, the cladogram appears to fit well biogeographical data for the Troidini in terms of vicariance biogcography, especially as this relates to the general hypotheses of Gondwanaland fragmentation and continental drift events advanced by recent geological studies. The genus Ornithoptera is shown to be distinct from Troides. Based on input data drawn equally from immature stages and adult characters, a single cladogram hypothesising the likely phylogeny of Ornithoptera species was generated. With minor weighting of a single important adult character (male forcwing uppersidc sex-brand), a further two clado grams were generated, one of which is similar to hypotheses proposed by previous workers. Based on these findings, and on ecological data, notably larval foodplant relations with Aristolochiaceac, as well as present-day biogeographical data, a new theory of the origin and evolution of Ornithoptera is presented which fits well Gondwanan vicariance events ascertained by geological studies: essentially that Ornithoptera evolved on northward drifting Australia, allopatrically from Troides on the Indian plate, and therefore that Ornithoptera did not reach the Australian subrcgion via TroiV/w-likc ancestors in Southeast Asia as has been previously postulated. Key Words androconia, Aristolochia, Aristolochiaccae, Atrophaneura, Australia, Battus, Bhutanitis, biogeography, Chilasa, classification, continental drift, Cressida, Euryades, foodplant, genitalia, Gondwanaland, Indonesia, Irian Jaya, larvae, Luehdorfia, mimicry, New Guinea, Ornithoptera, ova, Papilio, Papilioninac, Papilionini, Pararistolochia, Parides, Parnassiinae, Parnassiini, Pharmacophagus, phylogenetic, pupae, sphragis, swallowtail, Thottea, Trogonoptera, Troides, Zcrynthiini. *' Present address: Department of Entomology and Ncmatology, University of Florida, Bldg. 970, Hull Road, Gainesville FL 32611-0620, U. S. A. 44 Michael J. Parsons Contents Introduction 44 "Total Evidence" and Improving Analyses 46 The Tribe Troidini Ford, 1944 48 Method 49 Recognition ofTroidini Terminal Taxa 49 Methodology, Rationale and Selection ofOutgroups forTroidini Analysis 50 Selection of Characters for Troidini Analysis 53 Enumeration and Discussion ofTroidini Characters 54 The genus Ornithoptera Boisduval, 1832 68 Generic Distinctness of Ornithoptera and Troides 71 Outgroup Selection for Analysis of Ornithoptera 75 Enumeration of Ornithoptera Characters 77 Results 79 Enumeration ofTroidini Cladcs 79 Enumeration of Ornithoptera Cladcs 91 Discussion 94 Troidine Evolution and Gondwanan Palacobiogcography 94 Ornithoptera Origin and Biogcography: A New Hypothesis 97 Evidence from Foodplant Relations 101 Birdwing Evolution: Also Part of the Gondwanan Picture 103 Older, More Ancient Origins 105 Concluding Remarks 107 INTRODUCTION Like that of Munroe (1961), the early work of Igarashi (e.g. 1963), culminating in his more recent publications (e.g. Igarashi 1979 and 1984), can be regarded as pioneering in classifying the family Papilionidae. Igarashi's research was particu larly important because he emphasised the use of immature (or early) stages (eggs, larvae and pupae) to study the classification of the family. His work is, therefore, as much a foundation to the understanding of papilionid systematics as those of Munroe and Ehrlich (1960) and Munroe (1961) who concentrated on adult characters. Reliable phylogenetic reconstructions are of great importance in biogeographical studies (e.g. Hennig, 1966; De Jong, 1979). Only characters that are truly effective and/or useful in such systematic analyses will provide 'reasonable' (i.e. generally accepted) results. These must be selected and defined, which is a highly subjective process, limited by constraints on a researcher's knowledge of the particular group under scrutiny. As it is impossible to know which characters provide the 'best' (most unequivocal or truly reliable) results, this selection process represents a fundamental problem in any method of systematic study or classification (cladistic or otherwise), and renders all resultant hypotheses open to legitimate speculation. Nevertheless, it follows that the broader a researcher's knowledge is (encompassing Reappraisal of Troidini 45 other related groups, i.e. outgroups, etc.), the more likely it is that they will be able to make effective choices in character selection and thereby, in theory, improve the likelihood of obtaining results that better ascertain the actual course of events in the evolution of any study group. Only those facies that most assuredly reflect unidirectional evolutionary changes (rather than reversals, or those that have evolved independently several times) will provide the strongest corroboration of the 'correct' structures of evolutionary trees. Preferably, therefore, such characters should be relatively stable, not subject to rapid change, and so will provide greater reliability in their use in ascertaining sequences of evolution. Problems of character selection are perhaps more evident than ever in modern phylogenetic studies. For example, recent analyses of the butterflies as an entire group (including two cladistic studies) have resulted in at least three markedly different scenarios for their evolution at the family level: Kristensen (1976); Scoble (1986); Shields (1989). Even for the most popular and well-studied butterfly family, Papilionidae, Hauser (1993), while critically re-reviewing their classification, found that, contrary to previous findings, the subfamily Parnassiinae does not comprise a monophyletic group because the characters used were insufficiently well- known and/or rather poorly analysed. In their cladistic study of American swallow tails, Tyler etal. (1994) concluded that "with a judicious choice of these [characters] and the right taxa, you can make the papilionid phytogeny look almost any way you please." Likewise, even in studies of bird and human evolution, recent new fossil finds (providing still further characters for analysis) have only served to continue to challenge conventional theories of the historical lineages of these groups. It need hardly be emphasised that the latter are animal groups with at least a good base of adequate fossil evidence, whereas in the Lepidoptera (notably butterflies) this is extremely scant at best. The Aristolochiaceae-feeding papilionids in New Guinea were found to be particularly good candidates for cladistic study because reasonable data on their immature stages and ecology is available, and outgroups for these groups can be selected with some confidence. In addition, in carrying out a study of the foodplant relations of New Guinea Troidini, it was found necessary to address some apparent taxonomic problems in the classification of the 'birdwing' genera, most notably the validity of Ornithoptera as a genus distinct from Troides (Parsons, 1991). For example, in recent cladistic analyses, Hancock (1983) and Miller (1986, 1987b) merely saw fit to lump the two taxa, thereby obscuring the great importance of their relationships with other troidine genera. As Hauser (1993) pointed out: where characters are insufficiently well known and/or are poorly analysed then the results can likewise be expected to be poor or incorrect. For example, he found that the forewing cubital crossvein does not represent an autapomorphy of the Papilioninae, and that the Parnassiinae are paraphylctic as the subfamily presently stands because of poor interpretation ofadult characters, especially confusion overvalid synapomor- 46 Michael J. Parsons phic characters to truly define Parnassiinae. "Total Evidence" and Improving Analyses Authors such as Kluge (1989) and Tyler etal. (1994) have convincingly argued that the only really effective way to reconstruct the phylogenies of organisms is to include all possible characters, using the so-called "principle of total evidence" (Kluge, 1989). Adult characters have been the prime (often only) focus of attention for Lepidopterists in most systematic and phylogenetic studies. Characters of male butterfly genitalia, venation and wing pattern have traditionally been selected (including most of the recent cladistic analyses of butterflies) primarily because they are the easiest to study. However, Homma (1954), for example, suggested that the alimentary canal in butterflies is of taxonomic use, and some analyses have also included adult butterfly sensory and ambulatory appendages. Nevertheless, as my own studies of many different New Guinea butterfly groups have repeatedly demon strated (e.g. Parsons,