Geographic divergence in upper thermal limits across insect life stages: does behavior matter?
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Insects with complex life cycles vary in size, mobility, and thermal ecology across life stages. We examine how differences in the capacity for thermoregulatory behavior influence geographic differences in physiological heat tolerance among egg and adult Colias butterflies. Colias adults exhibit differences in morphology (wing melanin and thoracic setal length) along spatial gradients, whereas eggs are morphologically indistinguishable. Here we compare Colias eriphyle eggs and adults from two elevations and Colias meadii from a high elevation. Hatching success and egg development time of C. eriphyle eggs did not differ significantly with the elevation of origin. Egg survival declined in response to heat-shock temperatures above 38–40 °C and egg development time was shortest at intermediate heat-shock temperatures of 33–38 °C. Laboratory experiments with adults showed survival in response to heat shock was significantly greater for Colias from higher than from lower elevation sites. Common-garden experiments at the low-elevation field site showed that C. meadii adults initiated heat-avoidance and over-heating behaviors significantly earlier in the day than C. eriphyle. Our study demonstrates the importance of examining thermal tolerances across life stages. Our findings are inconsistent with the hypothesis that thermoregulatory behavior inhibits the geographic divergence of physiological traits in mobile stages, and suggest that sessile stages may evolve similar heat tolerances in different environments due to microclimatic variability or evolutionary constraints.
KeywordsColias Wing melanin Overheating Heat shock Thermoregulation
We thank the City of Gunnison, the City of Montrose, and Robert and Roxanne Lane of Dayspring Farms for access to collection sites. We also thank the Rocky Mountain Biological Laboratory for access to lab space. We thank Kati Moore for her tireless work with the egg thermal gradient and Edward Shin for the countless hours scoring egg-hatching videos. We thank Kate Augustine, Samuel Shuford, and Autumn Arciero for help with field experiments. We also thank the reviewers and Rob Dunn for useful edits on the manuscript. The research was supported in part by NSF Grants DEB-1120062 to L. B. B. and J. G. K. and IOS-1120500 to J. G. K.
Author contribution statement
H. J. M., L. B. B., and J. G. K. conceived and designed the experiments. H. J. M. and J. K. H. performed the experiments. H. J. M. and J. G. K. analyzed the data. H. J. M. and J. G. K. wrote the manuscript; other authors provided editorial advice.
- García-Barros E (2000) Egg size in butterflies (Lepidoptera: papilionoidea and Hesperiidae): a summary of data. J Res Lepidoptera 35:90–136Google Scholar
- Grambsch TMTaPM (2014) Modeling survival data: extending the cox model. R package version 2.37-7 http://CRAN.R-project.org/package=survival
- Hayes JL (1980) Some Aspects of the Biology of the Developmental Stages of Colias alexandra (Pieridae). J Lepidopterists Soc 34(4): 345–352Google Scholar
- Higgins JK (2014) Rapid evolution and population divergence in response to environmental change in Colias butterflies. PhD, University of North Carolina at Chapel Hill, Chapel HillGoogle Scholar
- IPCC, Field CB, Barros VR, Dokken DJ, Mach KJ, Mastrandrea MD, Bilir TE, Chatterjee M, Ebi KL, Estrada YO, Genova RC, Girma B, Kissel ES, Levy AN, MacCracken S, Mastrandrea PR, White LL (2014) Ipcc climate change 2014: impacts, adaptation, and vulnerability. Part A: global and sectoral aspects. In: Field CB, Barros VR, Dokken DJ, Mach KJ, Mastrandrea MD, Bilir TE, Chatterjee M, Ebi KL, Estrada YO, Genova RC, Girma B, Kissel ES, Levy AN, MacCracken S, Mastrandrea PR, White LL (eds) Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, New YorkGoogle Scholar
- Kingsolver JG (1983) Ecological significance of flight activity in Colias butterflies: Implications for reproductive strategy and population structure. Ecol 64:545–551Google Scholar
- Pinheiro J, Bates D, DebRoy S, Sarkar D and R Core Team (2014) Nlme: linear and nonlinear mixed effects models. R package version 3.1-117 http://CRAN.R-project.org/package=nlme
- R Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. http://www.R-project.org/
- Springer P, Boggs CL (1986) Resource Allocation to oocytes: heritable variation with altitude in Colias philodice eriphyle (Lepidoptera). Am Nat 127:252–256. http://www.jstor.org/stable/2461354