Juvenile ecology drives adult morphology in two insect orders

Abstract

Most animals undergo ecological niche shifts between distinct life phases, but such shifts can result in adaptive conflicts of phenotypic traits. Metamorphosis can reduce these conflicts by breaking up trait correlations, allowing each life phase to independently adapt to its ecological niche. This process is called adaptive decoupling. It is, however, yet unknown to what extent adaptive decoupling is realized on a macroevolutionary scale in hemimetabolous insects and if the degree of adaptive decoupling is correlated with the strength of ontogenetic niche shifts. It is also unclear whether the degree of adaptive decoupling is correlated with phenotypic disparity. Here, we quantify nymphal and adult trait correlations in 219 species across the whole phylogeny of earwigs and stoneflies to test whether juvenile and adult traits are decoupled from each other. We demonstrate that adult head morphology is largely driven by nymphal ecology, and that adult head shape disparity has increased with stronger ontogenetic niche shifts in some stonefly lineages. Our findings implicate that the hemimetabolan metamorphosis in earwigs and stoneflies does not allow for high degrees of adaptive decoupling, and that high phenotypic disparity can even be realized when the evolution of distinct life phases is coupled.

Bite force transmission and mandible shape in grasshoppers, crickets, and allies is largely dependent on phylogeny, not diet

“…A further 190 specimens were scanned at DESY (Deutsches Elektronen Synchrotron, Hamburg, Germany) of which 106 were processed at the IBL-P05 imaging beamline (Khokhriakov et al, 2017; Moosmann et al, 2014; Wilde et al, 2016) (operated by the Helmholtz-Zentrum Hereon at PETRA III) and 74 larger specimens at the Phoenix Nanotom, General Electric, Boston, MA) housed at DESY. Each scan was downsampled to ∼300 MB with Fiji (Schindelin et al, 2012) using a stack-cropping macro script of Rühr et al, 2021, which also generates ‘HDR5-Analyse’ files with a corresponding .hdr file for import into ITK-Snap (v. 3.8) (Yushkevich et al, 2006). 3D reconstruction was done in ITK-Snap with a pre-segmentation by hand and completed using a semi-automatic segmentation algorithm.…”

The ant abdomen: The skeletomuscular and soft tissue anatomy of Amblyopone australis workers (Hymenoptera: Formicidae)

“…An important factor is that micro-CT works with ethanolpreserved (Püffel et al, 2021) and dry-mounted specimens (Rühr et al, 2021) as well as with fossils preserved in a matrix (Boudinot et al, 2022a;Schwermann et al, 2016;Soriano et al, 2010;van de Kamp et al, 2018). We note that much of the value of CT-data is in their manipulability within visualization and analysis software, here was originally generated as part of preliminary data exploration for an unrelated project.…”

Ornamented species incur higher male mortality in the larval stage

“…The discovery of abundant genetic (co-)variation was thought to undergird Darwin's assertion because such genetic resources should be sufficient for each life-cycle stage to eventually adapt to its unique selective pressures when given enough time (reviewed in [2]). However, recent empirical and theoretical studies indicate that even highly polygenic traits have not evolved as independently between life-cycle stages as we have long assumed [3–8]. For instance, evolution towards smaller body sizes is associated with the evolution of smaller adult sizes in frogs, despite the potential for substantial post-metamorphic growth [4].…”