Size-related life-history traits in geometrid moths: a comparison of a temperate and a tropical community

1. Comparative studies on insect life histories are facilitated by the increasing availability of reliable phylogenies but are hampered by the scarcity of comparable data. Fortunately, morphological proxies of some life-history traits can be measured on preserved specimens. 2. This study compared values of size-related life-history traits among a tropical (Ugandan) and a temperate (Estonian) assemblage of geometrid moths. 3. A comparative analysis based on an originally derived phylogeny revealed that tropical moths were, on average, larger than temperate ones. Tropical moths also had somewhat lower relative abdomen masses than temperate ones. This indicates that the tropical rather than the temperate moths tend to use an income (rather than capital) breeding strategy. Nevertheless, no difference was found in a related index of pro-ovigeny. When body size was accounted for, tropical moths were found to lay smaller eggs than temperate ones. 4. The differences between the two compared areas are consistent with selection on higher mobility of the moths imposed by the more diverse tropical vegetation. Relatively larger eggs of temperate moths may constitute an adaptation to overcome the presumably stronger quantitative defences of their host plants. 5. Overall, however, we conclude that the differences in ecologically relevant size-related traits are relatively low among moth assemblages of a tropical and a temperate forest region, indicating that these environments may not impose radically different selective pressures on insect life histories.