Genetic divergence does not predict change in ornament expression among populations of stalk-eyed flies

Stalk‐eyed flies (Diptera: Diopsidae) possess eyes at the ends of elongated peduncles, and exhibit dramatic variation in eye span, relative to body length, among species. In some sexually dimorphic species, evidence indicates that eye span is under both intra‐ and intersexual selection. Theory predi...

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Bibliographic Details
Published in:	Molecular ecology Vol. 14; no. 12; pp. 3787 - 3800
Main Authors:	Swallow, J.G, Wallace, L.E, Christianson, S.J, Johns, P.M, Wilkinson, G.S
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Science Ltd 01-10-2005 Blackwell Publishing Ltd
Subjects:	Animal populations Animals Asia, Southeastern Biometry compound eyes Cyrtodiopsis Cyrtodiopsis dalmanni Cyrtodiopsis whitei cytochrome-c oxidase Diopsidae Diptera Diptera - anatomy & histology Diptera - genetics DNA, Mitochondrial - genetics Eye - anatomy & histology Female Gene expression genes Genetic diversity genetic variation Haplotypes insect morphology Insects Male mitochondrial DNA molecular sequence data nucleotide sequences Phylogeny Polymorphism, Genetic reproductive traits ribosomal RNA secondary sexual traits Selection, Genetic Sex Characteristics sexual selection stalk-eyed flies Borneo Malaysia Indonesia Asia, Southeastern
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Summary:	Stalk‐eyed flies (Diptera: Diopsidae) possess eyes at the ends of elongated peduncles, and exhibit dramatic variation in eye span, relative to body length, among species. In some sexually dimorphic species, evidence indicates that eye span is under both intra‐ and intersexual selection. Theory predicts that isolated populations should evolve differences in sexually selected traits due to drift. To determine if eye span changes as a function of divergence time, 1370 flies from 10 populations of the sexually dimorphic species, Cyrtodiopsis dalmanni and Cyrtodiopsis whitei, and one population of the sexually monomorphic congener, Cyrtodiopsis quinqueguttata, were collected from Southeast Asia and measured. Genetic differentiation was used to assess divergence time by comparing mitochondrial (cytochrome oxidase II and 16S ribosomal RNA gene fragments) and nuclear (wingless gene fragment) DNA sequences for c. five individuals per population. Phylogenetic analyses indicate that most populations cluster as monophyletic units with up to 9% nucleotide substitutions between populations within a species. Analyses of molecular variance suggest a high degree of genetic structure within and among the populations; > 97% of the genetic variance occurs between populations and species while < 3% is distributed within populations, indicating that most populations have been isolated for thousands of years. Nevertheless, significant change in the allometric slope of male eye span on body length was detected for only one population of either dimorphic species. These results are not consistent with genetic drift. Rather, relative eye span appears to be under net stabilizing selection in most populations of stalk‐eyed flies. Given that one population exhibited dramatic evolutionary change, selection, rather than genetic variation, appears to constrain eye span evolution.
Bibliography:	ArticleID:MEC2691 ark:/67375/WNG-7H2CV45N-2 istex:61F820FF029D4A5D1E70614C64D505DF3F1E2867 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0962-1083 1365-294X
DOI:	10.1111/j.1365-294X.2005.02691.x