Evol Ecol Res 18: 443-457 (2017)     Full PDF if your library subscribes.

Ambient temperature and host specialization drive mitochondrial genome evolution in fruit flies of the genus Bactrocera (Diptera: Tephritidae)

Hichem Ben Slimen, A. Awadi and M. Makni

Unité de Recherche Génomique des Insectes Ravageurs des Cultures d’Intérêt Agronomique, Faculté des Sciences de Tunis, Université de Tunis El-Manar, El Manar, Tunis, Tunisia

Correspondence: Hichem Ben Slimen, Unité de Recherche Génomique des Insectes Ravageurs des Cultures d’Intérêt Agronomique, Faculté des Sciences de Tunis, Université de Tunis El-Manar, El Manar, 2092 Tunis, Tunisia. email: ben_slimen_hichem@yahoo.fr


Background: Recent studies of selection on mitochondrial coding genes suggest adaptation due mainly to environmental variation.

Question: What is the extent of positive selection on the mitochondrial genomes of fruit flies? Are amino acid substitutions on these genomes affected by climate variation and/or host type (i.e. polyphagous, oliphagous or monophagous)?

Data incorporated: Seventeen complete mitochondrial genomes of fruit flies of the genus Bactrocera (retrieved from Genbank).

Method of analysis: Site and branch-site methods were applied to detect amino acid positions and lineages under positive selection. Relationships between genotypes and bioclimatic data were assessed using correlation tests, while genetic variation between polyphagous, oliphagous, and monophagous insects was assessed using a Kruskal-Wallis H-test. In addition, we applied a multiple regression analysis, with the genetic parameters as the dependent (outcome) variables, and the bioclimatic factors and host type as the predictor (independent) variables. Finally, we compared rates of evolution of the 13 mitochondrial coding genes with the corresponding predicted ancestral sequences.

Conclusions: Site and branch-site applied tests showed evidence of positive selection in 37 codons in 11 of the 13 mitochondrial coding genes, mostly affecting the oligophagous lineages. We found strong relationships between the genetic parameters and mean diurnal range, suggesting an effect of ambient temperature in the evolution of the genus Bactrocera. Moreover, a significant increase of amino acid substitutions from the predicted ancestor suggests an effect of the observed mitochondrial variation in the specialization process from polyphagous to monophagous species. Finally, we showed that NADH dehydrogenase subunit 6, one of the 13 mitochondrial coding genes, evolves independently from all the other genes of the same linkage system.

Keywords: Bactrocera, environmental adaptation, host specialization, mtDNA, positive selection

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