Morphology, Ontogeny, and Adaptation of Ambrysus mormon (Hemiptera: Naucoridae): Quantitative Comparisons among Populations in Different Thermal Environments

Abstract

Specimens of Ambrysus mormon Montandon were collected from each of 3 widely separated populations that differed in thermal environment. For each population, 15 characters were measured from each of 10 individuals–for each of the 5 instars, adult males, and adult females–to determine if interdemic differences exist in allometric development. All 3 populations can be distinguished at each instar based on multivariate analyses, and all instars and both sexes of adult are morphometrically distinct within each population. Nonetheless, the magnitude of difference among populations depended on instar. Most of the variation among individuals (>99.0%) was related to size and could be associated with differences among instars or between sexes of adult. In most cases (40 of 42 analyses), growth was allometric rather than isometric, and regardless of population, the direction of allometry was consistent for a particular character (body width and profemur length are exceptions). Although the magnitude of size variation from 1st to 5th instars and adults was similar in all populations, interpopulational differences in allometric development occurred as well. Specifically, the rate of increase in size of 6 characters (head width, pronotum length, profemur length, mesotibia length, metatibia length, and metatarsus length) with respect to the rate of increase in body length differed among populations developing at different temperatures. Thus, overall shape differences existed among populations, and these differences changed through ontogeny. Because allometric relations consistently accounted for a significant and large portion of interindividual variation, we suggest that autadaptation rather than exadaptation has played a predominant role in the morphological evolution of A. mormon .