A synthesis of major environmental-body size clines of the sexes within arthropod species

Abstract

Body size at maturity often varies with environmental conditions, as well as between males and females within a species [termed Sexual Size Dimorphism (SSD)]. Variation in body size clines between the sexes can determine the degree to which SSD varies across environmental gradients. We use a meta-analytic approach to investigate whether major biogeographical and temporal (intra-annually across seasons) body size clines differ systematically between the sexes in arthropods. We consider 329 intra-specific environmental gradients in adult body size across latitude, altitude and with seasonal temperature variation, representing 126 arthropod species from 16 taxonomic orders. On average, we observe greater variability in male than female body size across latitude, consistent with the hypothesis that, over evolutionary time, directional selection has acted more strongly on male than female size. In contrast, neither sex exhibits consistently greater proportional changes in body size than the other sex across altitudinal or seasonal gradients, akin to earlier findings for plastic temperature-size responses measured in the laboratory. Variation in the degree to which body size gradients differ between the sexes cannot be explained by a range of potentially influential factors, including environment type (aquatic vs. terrestrial), voltinism, mean species’ body size, degree of SSD, or gradient direction. Ultimately, if we are to make better sense of the patterns (or lack thereof) in SSD across environmental gradients, we require a more detailed understanding of the underlying selective pressures driving clines in body size. Such understanding will provide a more comprehensive hypothesis-driven approach to explaining biogeographical and temporal variation in SSD. Electronic supplementary material The online version of this article (10.1007/s00442-019-04428-7) contains supplementary material, which is available to authorized users.

Sex-specific plasticity and the nutritional geometry of insulin-signaling gene expression in Drosophila melanogaster

“…Thus, in birds and mammals, where SSD is generally male-biased, male growth tends to be affected more by nutritional stress than female growth [ 12 ]. In contrast, in in arthropods, where SSD is typically female-biased [ 27 , 28 ], female growth is more affected by nutritional stress [ 7 , 29 ]. This suggests that the mechanisms that generate SSD at least partially overlap with those that generate sex-specific nutritional plasticity.…”

Longitudinal-size Trend in Eight Species of Centrobolus

“…The best, but by no means conclusive evidence to date in this regard has been presented by McCabe and Partridge (1997) and Reeve et al (2000). The evidence in support for this was found in showing longer-lighter male millipedes occurred at higher temperatures and lower latitudes, providing support for directional selection on male size in 126 arthropod species from 16 taxonomic orders Horne et al, 2019). The evidence for the rule is supported on a global scale and suggests fecundity selection on female width (Cooper M., 2016).…”

Sex-specific plasticity and the nutritional geometry of insulin-signaling gene expression inDrosophila melanogaster

“…In birds and mammals, male growth tends to be affected more by nutritional stress than female growth [8], while in arthropods, the reverse appears to be true [9]. This is accompanied by the general trend of male-biased SSD in birds and mammals versus female-biased SSD in arthropods [10, 11]. Generally, therefore, the larger sex tends to be more nutritionally plastic than the smaller sex, and SSD increases with body size within a population [11].…”

“…This is accompanied by the general trend of male-biased SSD in birds and mammals versus female-biased SSD in arthropods [10, 11]. Generally, therefore, the larger sex tends to be more nutritionally plastic than the smaller sex, and SSD increases with body size within a population [11]. This suggests that the mechanisms that generate SSD at least partially overlap with those that generate sex-specific nutritional plasticity.…”