Wing reduction and body size variation along a steep elevation gradient: a case study with Magellanic sub-Antarctic mayflies and stoneflies

Abstract

IntroductionEcogeographical patterns in body size have been described across a wide range of vertebrate species. However, insects have shown inconsistent patterns in studies to date. Aquatic insects, particularly those from remote regions, have barely been explored.MethodsThe Magellanic sub-Antarctic ecoregion offers an ideal natural laboratory with near pristine environments, limiting the potential influence of confounding variables. In this study, we evaluated the influence of elevation on body and wing size and aspect ratio patterns for 10 species of mayfly (Ephemeroptera) and stonefly (Plecoptera) along a steep coastal elevation gradient (~0–600 m a.s.l.).ResultsWe detected significant relationships between altitude and morphological features for the studied species. Additionally, we found that in females, morphological changes were slightly more pronounced than in males, probably due to their role as dispersers. While body size showed an increase along the elevation gradient, there was a notable decrease in some species' wing length over a relatively short geographic distance.DiscussionOur data suggest that morphological plasticity might be promoted in response to the harsh environmental conditions that typify the steep coastal Magellanic sub-Antarctic mountain ranges.

Elevational constraints on flight efficiency shape global gradients in avian wing morphology

“…Recent quan@ta@ve analyses have tested variants of this hypothesis in a range of taxa, with some showing evidence of increased wing size or elonga@on at higher eleva@ons for par@cular bird species 15,[39][40][41] , and other studies finding no such rela@onship [42][43][44] . Similarly, in some groups of insects, wing size appears to increase in rela@on to body size at high eleva@ons 18 whereas other studies show the opposite trend of wing reduc@on 45,46 . These opposing trends may reflect varia@on among species in the effects of ecological gradients linked to climate or food supply.…”

“…These opposing trends may reflect varia@on among species in the effects of ecological gradients linked to climate or food supply. For example, some insect species are thought to become less aerial and therefore shorter-winged at high eleva@ons because lower temperatures and stronger winds increase the cost and risk of flight 45,46 . In birds, too, the propor@on of aerial-foraging species may decline at higher eleva@ons, either because cooler temperatures reduce the availability of airborne insect prey 47 , or limit the produc@on of thermal updraughts used by soaring species 48 .…”

Breaking the Law: Is It Correct to Use the Converse Bergmann Rule in Ceroglossus chilensis? An Overview Using Geometric Morphometrics

“…In this way, the authors conclude that this rule can be a valid ecological generalization for these two groups of endotherms. However, when studying the application of Bergmann's rule in major ectotherm groups, contrasting responses can be observed [7,13,14]. While Anurans increase their body size with latitude, lizards and snakes (squamates) reverse (or converse) this rule by decreasing their size as latitude increases [15,16].…”

“…Shelomi [3] states the importance of well-designed and continuous intraspecific studies as patterns regarding this rule can vary substantially even between closely related species [22]. Even though most species of insect groups are more likely to follow the converse Bergmann's rule (such as Coleoptera), some groups exactly follow Bergmann's rule (Diptera) or show no significant trends, like Plecoptera [3], water beetles [23] or even Ephemeroptera [14]. Interestingly, when the phylogenetic inertia associated with an insect group was controlled through comparative phylogenetic analyses, an insect group followed the converse Bergmann's rule; see the case of the bumblebee in [24].…”