The Ecology and Evolution of Melitaeine Butterflies Niklas Wahlberg Metapopulation Research Group Department of Ecology and Systematics Division of Population Biology University of Helsinki Finland Academic dissertation To be presented, with permission of the Faculty of Science of the University of Helsinki, for public criticism in the lecture room of the Department of Ecology and Systematics, P. Rautatiekatu 13, on October 27, 2000, at 12 o’clock noon. Helsinki 2000 © Niklas Wahlberg, pp. 7–26 Technical editing by Johan Ulfvens Author’s address: Metapopulation Research Group Department of Ecology and Systematics Division of Population Biology P.O. Box 17 (Arkadiankatu 7) 00014 University of Helsinki Finland e-mail: [email protected] ISBN 952-91-2615-8 (nid) ISBN 952-91-2688-3 (pdf) Oy Edita Ab Helsinki 2000 Helsinki 2000 The Ecology and Evolution of Melitaeine Butterflies Niklas Wahlberg Metapopulation Research Group Department of Ecology and Systematics Division of Population Biology P.O. Box 17 (Arkadiankatu 7) 00014 University of Helsinki Finland The thesis is based on the following articles: I Wahlberg, N. & Zimmermann, M. 2000. Pattern of phylogenetic relationships among members of the tribe Melitaeini (Lepidoptera: Nymphalidae) inferred from mtDNA sequences. – Cladistics 16, in press. II Wahlberg, N. 2000. The phylogenetics and biochemistry of host plant specialization in melitaeine butterflies (Lepidoptera: Nymphalidae). – Submitted manuscript. III Wahlberg, N., Klemetti, T., Selonen, V. & Hanski, I. 2000. Metapopulation structure and movements in five species of checkerspot butterflies. – Manuscript. IV Wahlberg, N., Moilanen, A. & Hanski, I. 1996. Predicting the occurrence of endangered species in fragmented landscapes. – Science 273: 1536-1538. V Wahlberg, N., Klemetti, T. & Hanski, I. 2000. Dynamic populations in a dynamic landscape: the metapopulation structure of the marsh fritillary butterfly. – Manuscript. These are referred to by their Roman numerals in the text. 4 Contributions Contributions The following table shows the major contributions of authors to the original articles. I II III IV V Original idea NW, MZ NW IH, NW IH TK, IH, NW Study design NW NW NW IH, NW TK, NW Methods and implementation NW NW NW IH, AM, NW NW, TK Empirical data gathering NW, MZ NW NW, J-PB, TK, VS NW, MP TK Manuscript preparation NW NW NW NW, IH NW J-PB = Jan-Peter Bäckman MP = Mikko Pitkänen Supervised by Prof. Ilkka Hanski University of Helsinki Finland Reviewed by Prof. Jari Kouki University of Joensuu Finland Dr. Risto Väinölä University of Helsinki Finland Examined by Prof. Michael Singer University of Texas USA Contents 5 Contents 0. Summary ........................................7 Introduction .......................................7 Systematics and biogeography ..............................8 The relationship between melitaeines and their host plants ...............11 Population structure and dynamics ...........................15 Population structure in melitaeines .........................15 Movements of individuals .............................18 Conclusions .......................................20 Challenges for the future ................................21 References .......................................22 The ecology and evolution of melitaeine butterflies 7 Introduction Phylogenetical hypotheses can be used by comparative biologists to study common evo- The study of evolution is often focused on lutionary patterns across species and to infer some particular characters in a set of related which characters may have evolved in partic- species. By comparing different but related ular species as adaptations to the surrounding species one can hope to partition the effects of environment (Harvey and Pagel 1991). adaptation and constraint on a character of in- Taking a historical perspective can also help terest. The shared ancestry of species may us understand the ecology of single species confound such comparisons, but by taking living in a changing world. By comparing a into account information on the genealogical group of related species, we can identify evo- relationships of the species, one can hope to lutionary constraints on ecological features make the data conform to the assumptions of we might be interested in, such as host plant statistical analyses (Wanntorp et al. 1990; choice in butterflies. My aim in this thesis is Harvey and Pagel 1991; Harvey 1996). to make a contribution towards a better under- The comparative approach has been used standing of the evolutionary and ecological over a long period of time since Darwin patterns observable in a group of butterflies (1859) first proposed the theory of evolution belonging to the tribe Melitaeini. by natural selection. There have been two dif- Checkerspot butterflies (melitaeines) ferent traditions in the field of comparative have played a major role in helping to under- analysis, called the descent and guild tradi- stand the population biology of insects ever tions (Harvey and Pagel 1991). Taxonomists since Paul Ehrlich began his work on group species according to common ancestry, Euphydryas editha in the late 1950’s (Ehrlich while ecologists group species according to a 1961; Ehrlich et al. 1975). Work on meli- common way of life (guilds). These two tradi- taeines has been extended into many areas of tions are now being united to ask questions population biology, from population ecology about the processes of evolution. For in- and genetics to the evolution of host plant use stance, are members of a guild of species sim- and host-parasitoid interactions. Most re- ilar in their ecology due to identity by descent, cently one melitaeine species, Melitaea or due to parallel or convergent evolution? cinxia, has become the focal species of exten- The comparative approach is basically a sive studies on metapopulation dynamics study in adaptation. Many ecologists have no- (Hanski 1999). ticed that different species have the same ad- The melitaeines are a distinct group of but- aptations in similar environments. Different terflies in the family Nymphalidae and com- species may have the same adaptations prise about 250 species (Higgins 1941, 1950, mainly for two reasons; they may share a 1955, 1960, 1981). The species are distrib- common ancestor (identity by descent) or nat- uted widely in Europe, Asia, North and South ural selection may have worked on the differ- America, but are absent from Africa south of ent species independently in a similar way the Sahara and Australia. According to the (parallel or convergent evolution) (Harvey most recent classification by Harvey (1991), and Pagel 1991). However, since the know- melitaeines form the tribe Melitaeini in the ledge of the evolutionary history of species subfamily Nymphalinae, which includes two and species groups is at best sketchy (usually other tribes, the Nymphalini and Kallimini. the fossil record is rather inadequate), what The Kallimini are postulated to be the sister one observes is the current state of unknown group of the Melitaeini based on larval mor- evolutionary development. In the past few de- phology (Harvey 1991) and DNA sequence cades systematic methods have enabled tax- data (Brower 2000b). onomists to build phylogenetic hypotheses The melitaeines have been taxonomically which show the best approximation of this revised extensively by L. G.Higgins over four evolutionary development for a species group decades (Higgins 1941, 1950, 1955, 1960, (Hennig 1965; Kitching et al. 1998). 1978, 1981). He divided the butterflies into 8 The ecology and evolution of melitaeine butterflies three main groups for which no morphologi- Systematics cal intermediate forms are known (Higgins and biogeography 1981). One group comprises the species be- longing to the genus Euphydryas, which dif- Despite the intensive taxonomic work on the fer from all other melitaeines by the structure melitaeines, nobody has attempted to build a of the genitalia and features of their life his- phylogeny for the entire group. In part this is tory. The second group is much less homoge- due to the difficulties of finding informative nous and includes melitaeine species belong- morphological characters. Many characters ing to the genera Melitaea, Chlosyne and 9 are invariant (which is why the group is so smaller genera. The third group consists of distinct), while the characters that vary tend to species belonging to the Phyciodes group, be hypervariable or form continuous clines which Higgins (1981) split into 12 genera. that make their coding very difficult (Higgins The relationships of species in this group 1941; Scott 1994, 1998). These problems of butterflies are just beginning to be discov- now have an apparently easy solution: DNA ered (I), opening up possibilities of detailed sequences (Simon et al. 1994; Caterino et al. comparative studies. The ecologies of many 2000). With the advent of the polymerase species are well known, which helps to for- chain reaction (PCR), DNA sequence data mulate relevant hypotheses that can be tested. has become accessible to just about anybody, In my thesis, I attempt to understand the eco- with the advantage that it does not require logy and evolution of melitaeine butterflies much experience to generate a large amount by investigating patterns found in a wide of data. This is in stark contrast to morpholog- range of hierarchical levels. I start from the ical data, which requires many years of expe- highest level, the level of the entire tribe, by rience for the researcher to be