Populations of the same species inhabiting distinct localities experience different ecological and climatic pressures that might result in differentiation in traits, particularly those related to temperature. We compared metabolic rate (and its thermal sensitivity), growth rate, and body size among nine high- and low-elevation populations of the Wellington tree weta, Hemideina crassidens, distributed from 9 to 1171. m. a.s.l across New Zealand. Our results did not indicate elevational compensation in metabolic rates (metabolic cold adaptation). Cold acclimation decreased metabolic rate compared to warm-acclimated individuals from both high- and low-elevation populations. However, we did find countergradient variation in growth rates, with individuals from high-elevation populations growing faster and to a larger final size than individuals from low-elevation populations. Females grew faster to a larger size than males, although as adults their metabolic rates did not differ significantly. The combined physiological and morphological data suggest that high-elevation individuals grow quickly and achieve larger size while maintaining metabolic rates at levels not significantly different from low-elevation individuals. Thus, morphological differentiation among tree weta populations, in concert with genetic variation, might provide the material required for adaptation to changing conditions.
Bibliographical noteFunding Information:
Thanks to the weta hunters: Dylan Anderson, Robyn Dewhurst, Natasha McKean, Alejandra Oyanedel and Briar Smith. The helpful IAE technicians: Paul Barrett, Tracy Harris, Shaun Nielsen and Cleland Wallace. Karen Smillie from Naturalac Nutrition Ltd (Auckland, New Zealand) donated the protein we used to supplement the diet of our captive weta. Dr. Gabe Redding helped set up the respirometry experiments. Gareth Boyt and Pete Shaw allowed and helped us to collect weta at Pohokura, and Rhys Mills allowed us to sample in the Nga Manu Nature Reserve. Milan Plećaš helped obtain the climate data. The following offices and staff of the New Zealand Department of Conservation helped us: Gareth Boyt (Rangataiki), Jeanine Bishop (Wellington), Beverley Freer and Ian Millar (Nelson Malborough), and Robyn Ellis (Tongariro Wanganui Taranaki). We are grateful to several anonymous referees for critical comments on an earlier version of the manuscript. This work was supported by a Massey University Research Grant ( MURF–2010 : What limits a weta?) and the Royal Society of New Zealand (Marsden PVT–601).
© 2015 Elsevier Ltd.
- Growth rates
- Metabolic cold adaptation
- Morphological variation
- New Zealand
- Standard metabolic rates