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Open Access Research article

Genetic constraints for thermal coadaptation in Drosophila subobscura

Olga Dolgova1, Carla Rego2, Gemma Calabria34, Joan Balanyà34, Marta Pascual34, Enrico L Rezende1 and Mauro Santos1*

Author Affiliations

1 Departament de Genètica i de Microbiologia, Grup de Biologia Evolutiva (GBE), Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain

2 Departamento de Ciências Agrárias, Azorean Biodiversity Group-CITAA, Universidade dos Açores, Terra-Chã, 9701-851 Angra do Heroísmo, Portugal

3 Departament de Genètica, Grup de Biologia Evolutiva (GBE), Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08071 Barcelona, Spain

4 Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, 08071 Barcelona, Spain

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BMC Evolutionary Biology 2010, 10:363  doi:10.1186/1471-2148-10-363

Published: 25 November 2010

Abstract

Background

Behaviour has been traditionally viewed as a driver of subsequent evolution because behavioural adjustments expose organisms to novel environments, which may result in a correlated evolution on other traits. In Drosophila subobscura, thermal preference and heat tolerance are linked to chromosomal inversion polymorphisms that show parallel latitudinal clines worldwide, such that "cold-climate" ("warm-climate") chromosome arrangements collectively favour a coherent response to colder (warmer) settings as flies carrying them prefer colder (warmer) conditions and have lower (higher) knock out temperatures. Yet, it is not clear whether a genetic correlation between thermal preference and heat tolerance can partially underlie such response.

Results

We have analyzed the genetic basis of thermal preference and heat tolerance using isochromosomal lines in D. subobscura. Chromosome arrangements on the O chromosome were known to have a biometrical effect on thermal preference in a laboratory temperature gradient, and also harbour several genes involved in the heat shock response; in particular, the genes Hsp68 and Hsp70. Our results corroborate that arrangements on chromosome O affect adult thermal preference in a laboratory temperature gradient, with cold-climate Ost carriers displaying a lower thermal preference than their warm-climate O3+4 and O3+4+8 counterparts. However, these chromosome arrangements did not have any effect on adult heat tolerance and, hence, we putatively discard a genetic covariance between both traits arising from linkage disequilibrium between genes affecting thermal preference and candidate genes for heat shock resistance. Nonetheless, a possible association of juvenile thermal preference and heat resistance warrants further analysis.

Conclusions

Thermal preference and heat tolerance in the isochromosomal lines of D. subobscura appear to be genetically independent, which might potentially prevent a coherent response of behaviour and physiology (i.e., coadaptation) to thermal selection. If this pattern is general to all chromosomes, then any correlation between thermal preference and heat resistance across latitudinal gradients would likely reflect a pattern of correlated selection rather than genetic correlation.