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. 2023 Jan 10;14(1):67.
doi: 10.3390/insects14010067.

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

Ning Kang  1   2 , Hongying Hu  1   2 , Zengqian Huang  1   2 , Shungang Luo  1   2 , Shuhan Guo  1   2
Affiliations

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

Ning Kang et al. Insects. .

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.

Keywords: Bergmann’s rule; Eulophidae; Pteromalidae; altitudinal clines; environmental adaptation; forewing length.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Geographic distribution of Pteromalidae and Eulophidae specimens used in this analysis. (b) Morphometric measurement illustrations. Upper: microslide specimen of male forewing of Sphegigaster stepicola and the scheme of wing length and wing area measurement. Lower: body of female Pachyneuron korlense and the scheme of body length, mesothorax length, tibia length, wing length, and wing area measurement.
Figure 2
Figure 2
Forewing length (FL) and hind tibia length (HTL) of Pteromalidae (n = 51 males and females of the same species) and Eulophidae (n = 48 males and females of the same species) in relation to body length (BL). (a) Correlation between FL and BL of Pteromalidae. (b) Correlation between FL and BL of Eulophidae. (c) Correlation between HTL and BL of Pteromalidae. (d) Correlation between HTL and BL of Eulophidae. All p < 0.001. Green circles: male; red circles: female. For detailed comparison of morphological characteristics, see Supplementary Material, Figure S1.
Figure 3
Figure 3
Forewing length of Pteromalidae and Eulophidae in relation to altitude based on two methods: (a) species-based method, (b) assemblage-based method. Green circles: male; red circles: female. See Supplementary Material, Figures S2 and S3 for detailed frequency histograms of four different elevation ranges.
Figure 4
Figure 4
Altitudinal distribution of Pteromalidae (a) and Eulophidae (b), and frequency of occurrence records by altitude. Box and whisker plots show the median (cross symbol), the 25th and 75th percentile (bottom and top of the box), the minimum and maximum values (lower and upper whiskers), and outliers (circles). The red line shows the frequency distribution of altitudinal values in the assemblage-based data.
See this image and copyright information in PMC

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