title: Elevational variation in adult body size and growth rate but not in metabolic rate in the tree weta Hemideina crassidens.
abstract: 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.
authors.affiliation: Ecology Group, Institute of Agriculture and Environment, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand. Electronic address: mbulgare@umn.edu.
authors.forename: Mariana
authors.initials: M
authors.lastname: Bulgarella
authors.affiliation: Ecology Group, Institute of Agriculture and Environment, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand. Electronic address: S.Trewick@massey.ac.nz.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Trewick
authors.affiliation: Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand. Electronic address: A.J.Godfrey@massey.ac.nz.
authors.forename: A Jonathan R
authors.initials: AJ
authors.lastname: Godfrey
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada. Electronic address: bsincla7@uwo.ca.
authors.forename: Brent J
authors.initials: BJ
authors.lastname: Sinclair
authors.affiliation: Ecology Group, Institute of Agriculture and Environment, Massey University, Private Bag 11-222, Palmerston North 4442, New Zealand. Electronic address: M.Morgan-Richards@massey.ac.nz.
authors.forename: Mary
authors.initials: M
authors.lastname: Morgan-Richards
mesh_terms: D000222:Adaptation, Physiological; D000531:Altitude; D000818:Animals; D001481:Basal Metabolism; D049628:Body Size; D005260:Female; D006135:Gryllidae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D009520:New Zealand; D012737:Sex Factors
keywords: Growth rates; Hemideina; Insects; Metabolic cold adaptation; Morphological variation; New Zealand; Plasticity; Standard metabolic rates