Temperature effects on wing vein morphology revealed by landmark-free morphometrics.

Insect wings commonly have 2 types of veins: primary and secondary. Primary veins have fixed positions across members of a given species, while the number, position, and connections of secondary veins vary from wing to wing even within individuals. Relative to primary veins, very little is known about the patterning and development of secondary venation, in part because they cannot be analyzed with traditional morphometric approaches, which require the identification of homologous landmarks across wings. We present a landmark-free morphometric approach for analyzing secondary wing venation, and we use it to describe the effects of temperature on secondary vein patterns in the common cricket Acheta domesticus (Linnaeus 1758). Our principal components-based approach identified 3 major compartments to the wing within which we observed correlations among the shapes of domains formed by secondary veins. Most interestingly, the effects of temperature varied across these compartments: higher temperatures were associated with larger domains in one compartment, smaller domains in another, and had no marginal correlation with domain shape in a third. This suggests that secondary vein development may involve multiple independent patterning systems in different regions, or more likely, a system whose parameters vary across the wing field.