Steep converse Bergmann's cline in a carrion beetle: between‐ and within‐population variation in body size along an elevational gradient

Abstract

Body size is an integrative trait with substantial fitness consequences in animals. Geographical clines in body size have fascinated biologists because of their potential to provide insight into the mechanisms governing local adaptation and phenotypic plasticity. In this complex study, we focused on variation in body size of Silpha carinata (Coleoptera: Silphidae) along elevation gradients in Central Europe. Altitudinal clines were investigated separately for males and females as sex-specific responses to environmental conditions are documented for a variety of insect species. To identify potential underlying mechanisms responsible for observed patterns, a common garden experiment and investigation of within-population variation in body size were performed. Body size of S. carinata recorded in nature sharply decreased with increasing altitude in both genders, whereas sexual size dimorphism did not change with altitude. The degree of within-population variation in body size recorded in nature did not change with altitude. Under standardized laboratory conditions, higher altitude females produced smaller eggs than those from lower altitude. This size difference persisted to the very end of the larval period. Unfortunately, only few offspring survived till adulthood in the laboratory and thus precise analysis of offspring adult sizes was unfeasible, but between-population differences in body size seems to persist to adulthood. The observed converse Bergmann's cline in S. carinata fits well with what has been predicted for large, carnivorous, univoltine insect species. Until now, investigation of within-population variation in body size is rare in insects, and future complementary studies focused on this issue are highly needed as within-population variation could explain body size patterns observed at between-population level.

Altitudinal variation of sexual size dimorphism in ground beetle Carabus odoratus Shill.

“…Usually, researchers study body size variation in insects for both genders. They note decreasing or increasing body size in high elevation [47,48,49]. Our results in SSD variation differ from those of other researchers.…”

Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas, India

“…Apart from those using T‐statistics, only a few studies have dealt with changes in trait distribution (of which variance is the simplest metric) with elevation (e.g., Baranovská & Knapp, 2018; Classen et al., 2017). In general, studies have reported increased variability in traits under “favorable conditions” at lower elevations where intra‐ and interspecific competition drives trait divergence (Ding et al., 2019; Mayfield & Levine, 2010), while habitat filtering due to extreme environmental conditions at higher elevations is associated with reduced trait variance (de Bello et al., 2009; Kraft & Ackerly, 2010).…”

Morphometric Variability among Populations of Euglossa cordata (Hymenoptera: Apidae: Euglossini) from Different Phytophysiognomies

“…The wing shape and size of E. cordata seems to be traits that vary between habitats, which may explain the presence of correlation found among these variables with phytophysiognomy type, latitude, longitude and altitude. These morphometric variations observed may be related to different populations responses to the local environmental characteristics of each phytophysiognomy, because insects may have plastic morphological adaptations in response to altitudinal and latitudinal geographical gradients (Baranovská & Knapp, 2018), or to local variations in landscape elements (Ribeiro et al, 2019). Grassi-Sella et al (2018) found a pattern of morphometric clustering in E. annectans and E. truncata related to the phytophysiognomy from which the populations were sampled, being such pattern attributed to phenotypic plasticity.…”