Wing geometric morphometrics to assess the population structure and dynamic patterns of Aedes aegypti (Diptera: Culicidae) in a temperate urban landscape.

Abstract

We analysed the phenotypic variability of Aedes aegypti at two moments of the activity season (beginning and peak) across five geographic areas in Buenos Aires, a temperate-climate city in Argentina, using geometric morphometrics of the wing shape. In the global analysis, Canonical Variate Analysis (CVA) showed slight shape variation between individuals from the beginning to the peak activity. Pairwise cross-validated reclassification yielded an accuracy of 68% for the beginning and 72% for the peak of activity. At the beginning of the activity, morphometric distances among areas were significant, cross-validated classification showed an overall accuracy of 68.9%, and no association was found between geographic and shape distances. During the peak of activity, no significant differences in morphological distances among areas were detected for the Centre-North, East-Westand East-South comparison using both Mahalanobis and Procrustes distances or for West-South comparison using Procrustes distances. Classification accuracy was 49%, and a significant correlation between the geographic and shape distances was observed. The phenetic tree grouped all geographic areas from the peak activity. Both the overall and partial analyses indicated that the wing shape was more variable at the beginning compared with the peak activity, where greater shape homogeneity was observed. The thermal characteristics of a temperate climate may modulate the exchange of individuals among areas throughout the season, resulting in morphological variation. Differences in wing shapes among geographic areas and no correlation between the geographic and morphological distances at the beginning may suggest that the activity season of Ae. aegypti could originate from morphologically divergent local populations. During the peak activity, the similarity in wing shapes among the geographic areas may indicate an enhanced dispersal flow of individuals during the period of highest relative abundance, resulting in a phenotypic homogenization of the wing shape. Patterns of wing shape changes over a relatively short time period may reflect specific dynamics within the urban environment.