Convergence and parallelism among cicadas of Argentina and the southwestern United States (Hemiptera: Cicadoidea)

Abstract

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 tolerances 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.