Evol Ecol Res 5: 977-997 (2003)     Full PDF if your library subscribes.

Geographic parthenogenesis in the Australian arid zone: II. Climatic analyses of orthopteroid insects of the genera Warramaba and Sipyloidea

Michael Kearney1* and Adnan Moussalli2

1 School of Biological Sciences, Heydon Laurence Building A08, The University of Sydney, Sydney, NSW 2006 and 2Department of Zoology and Entomology, University of Queensland, Brisbane, QLD 4072, Australia

Author to whom all correspondence should be addressed.
e-mail: mkearney@bio.usyd.edu.au

ABSTRACT

The Australian arid zone harbours a surprising number of parthenogenetic organisms, including the well known case of the grasshopper Warramaba virgo. Less well known is the case of the stick insects of the Sipyloidea complex, which, despite its presence in the literature for over 15 years, has gone entirely unnoticed by workers in the field. We draw attention to the remarkable similarities between the evolution of parthenogenesis in Warramaba and Sipyloidea and analyse the geographic distributions of parthenogenetic and sexual forms with respect to six climatic variables. We provide evidence that a combination of climatic and vegetative barriers are responsible for the current distribution patterns in these taxa. Comparisons are also made with patterns of geographic parthenogenesis in lizards of the Heteronotia binoei complex. In general, there has been a strong tendency for parthenogenesis to originate via hybridization in the western part of the arid zone with subsequent eastward spread throughout mulga woodlands and mallee shrublands where rainfall is both low and aseasonal. We propose that the hybridization events leading to parthenogenesis in these diverse taxa were driven by a common biogeographic process – that is, by range shifts associated with changes in aridity during the late Pleistocene.

Keywords: arid zone, Australia, climate, grasshopper, parthenogenesis, stick insect.

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