Environmental Factors Drive Chalcid Body Size Increases with Altitudinal Gradients for Two Hyper-Diverse Taxa

Abstract

Body size is the most essential feature that significantly correlates with insects’ longevity, fecundity, metabolic rate, and sex ratio. Numerous biogeographical rules have been proposed to illustrate the correlation between the body sizes of different taxa and corresponding geographical or environmental factors. Whether the minute and multifarious chalcids exhibit a similar geographical pattern is still little known. In this research, we analyzed morphological data from 2953 specimens worldwide, including the two most abundant and diverse taxa (Pteromalidae and Eulophidae), which are both composed of field-collected and BOLD system specimens. We examined forewing length as a surrogate of body size and analyzed the average size separately for males and females using two methods (species and assemblage-based method). To verify Bergmann’s rule, we included temperature, precipitation, wind speed and solar radiation as explanatory variables in a generalized linear model to analyze the causes of the size variation. We found that there was an increasing trend in the body size of Pteromalidae and Eulophidae with altitude. The optimal Akaike information criterion (AIC) models showed that larger sizes are significantly negatively correlated with temperature and positively correlated with precipitation, and the possible reasons for this variation are discussed and analyzed.

Variation in Measurements of Some Body Parts of Laodelphax striatella (Fallén, 1826) (Hemiptera: Fulgoromorpha: Delphacidae) due to Altitude

“…For example, in the studies on Dichroplus pratensis (Acrididae) [28], Onthophagus spp. (Scarabaeidae) [29] and Paropsis atomaria (Chrysomelidae) [30], decrease in body size were reported [1]. It was thought that this may be caused by combined effect of the exposed ecological factors and insect species.…”

“…There are some key features which provide monitoring the ecological, biological, and physiological status of organisms and give information about their fitness. One of these key factors is the body size that give information about metabolic performance, fecundity, and longevity of organisms [1]. Body size is one of the most important characteristics of organisms.…”

“…There are several studies in the literature showing that the effect of elevation on insect body size [1,[9][10][11][12][13][14][15]. While some of the studies reported increase in body size based on elevation, the others determined decrease.…”