Biological Journal of the Linnean Society, 2004, 83, 281–288. With 3 figures © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 281–288 281 Blackwell Science, LtdOxford, UKBIJBiological Journal of the Linnean Society0024- 4066The Linnean Society of London, 2004? 2004 832 281288 Original Article CONVERGENCE AND PARALLELISM IN CICADAS A. F. SANBORN ET AL. *Corresponding author. E-mail: asanborn@mail.barry.edu †Current address: 104 Hummingbird Circle, Buchanan Dam, TX 78609, USA Convergence and parallelism among cicadas of Argentina and the southwestern United States (Hemiptera: Cicadoidea) ALLEN F. SANBORN 1 *, MAXINE S. HEATH 2† , JAMES E. HEATH 2† , FERNANDO G. NORIEGA 3 and POLLY K. PHILLIPS 3 1 Barry University, School of Natural & Health Sciences, 11300 NE Second Avenue, Miami Shores, FL 33161–6695, USA 2 Department of Physiology, University of Illinois, Urbana, IL 61801, USA 3 Department of Biological Sciences, Florida International University, Miami, FL 33199, USA Received 13 October 2003; accepted for publication 20 February 2004 Cicadas of the genera Derotettix in Argentina and Okanagodes in the south-western United States resemble each other in colour, live on salt-tolerant plants (Atriplex spp. etc.), nearly match the colour of their respective host plants and produce songs above the range of avian hearing. The Argentine cicadas are smaller, but have nearly identical thermal limits for activity measured by the minimum temperature for flight (20–24 ∞C) and a body temperature at heat torpor (48–49 ∞C). The species shift activity from basking sites to shade at temperatures above 37 ∞C, although O. gracilis rises to a significantly higher temperature (40.7 ∞C) than its congener (38.2 ∞C) or Derotettix (37.2 ∞C). The thermal tolerances are the highest reported for cicada species. A third group using halophytes in Argentina (Babras sonorivox) has similar temperature tolerances and is cryptically coloured. The genera are convergent with respect to morphology, coloration, body size, behaviour, habitat choice and host plant selection. The similarities of thermal tol- erances and their influence on behaviour can be viewed as parallelism because the underlying mechanisms are the same in all species studied. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 281–288. ADDITIONAL KEYWORDS: Babras – behaviour – Derotettix – Okanagodes – temperature – thermal responses. INTRODUCTION Animals that experience the same natural selective factors often arrive independently at similar biological solutions to environmental problems. This homoplasy can occur through several mechanisms. Convergence occurs when distantly related taxa evolve superficially similar characteristics through independent develop- mental pathways. Parallelism occurs when organisms evolve similar features through the independent alter- ation of shared developmental pathways, often in closely related organisms (Futuyma, 1998). The exact definitions of convergence and parallelism are still a matter of debate (e.g. see summary in Weins, Chippindale & Hillis, 2003). Much of the confusion appears to be the result of the application of the defi- nitions to specific problems. Convergence has been described as characteristics that arise from different antecedent states, have different mechanisms involved in the expression of the similar traits or occur in distantly related organisms (Weins et al., 2003). By contrast, parallelism occurs when a trait evolves from the same antecedent state, uses the same mechanisms to express the trait and occurs in more closely related organisms (Weins et al., 2003). We are interested here in how similar morphological, physiological and behavioural characteristics have evolved in cicadas that inhabit similar habitats. We consider convergence