EVIDENCE FOR ASSOCIATION OF CHROMOSOMAL FORM AND DEVELOPMENT TIME FROM COMPLEX CLINES AND GEOGRAPHIC RACES IN THE GRASSHOPPER CALEDIA-CAPTIVA (ORTHOPTERA, ACRIDADAE)

Evidence for an association between chromosomal Form and development t ime in the grasshopper Caledia captiva (F.) was obtained through compa rison of two geographic taxa and analysis of a complex latitudinal din e within one of the taxa. Northern populations of the Moreton taxon po ssess a metacentric genome and are slow-developing. In contrast, the T orresian taxon, distributed throughout northern, coastal Australia, a region of pronounced seasonality in rainfall, and southern populations of the Moreton taxon, which inhabit a region of pronounced seasonalit y in temperature, both have an acrocentric genome and are fast-develop ing. The convergence of chromosomal form and development time between Torresian and southern Moreton populations appears to be driven by con vergence in life history. Seasonality limits grasshoppers to one gener ation per year and favours fist development. The transition between re latively acrocentric southern Moreton populations and relatively metac entric northern Moreton populations is gradual but not monotonic. Inst ead, a shift to a bivoltine life history in the middle of the transect occurs and is associated with shifts in both development time and chr omosomal form. These results imply an adaptive role for chromosomal fo rm, although the causative link between chromosomal variation and vari ation in development time remains to be established. (C) 1996 The Linn ean Society of London