Biology subjects

Engel, M. S.

Publications and source records attributed to Engel, M. S..

5 recordsLinked to original sources

bioRxiv2024

A new story of four Hexapoda classes: Protura as the sister to all other hexapods

Insects represent the most diverse animal group, yet previous phylogenetic analyses based on the morphological and molecular data have failed to agree on the evolutionary relationships of early insects and their six-legged relatives (together constituting the clade Hexapoda). In particular, the phylogenetic positions of the three early-diverging hexapod groups, the coneheads (Protura), springtails (Collembola), and two-pronged bristletails (Diplura), have been debated for over a century, with alternative topologies implying drastically different scenarios of the evolution of the insect body plan and hexapod terrestrialisation. We addressed this issue by sampling of all hexapod orders, and experimented with a broad range of across-site compositional heterogeneous models designed to tackle ancient divergences. Our analyses support Protura as the earliest-diverging hexapod lineage (Protura-sister) and Collembola as a sister group to the Diplura, a clade we refer to as Antennomusculata characterised by the shared possession of internal muscles in the antennal flagellum. The universally recognized Ellipura hypothesis is recovered under the site-homogenous LG model. Our cross-validation analysis shows that the CAT-GTR model that recovers Protura-sister fits significantly better than homogenous model. Furthermore, as a very unusual group, Protura as the first diverging lineage of hexapods is also supported by other lines of evidence, such as mitogenomics, comparative embryology, and sperm morphology. The backbone phylogeny of hexapods recovered in this study will facilitate the exploration of the underpinnings of hexapod terrestrialisation and mega-diversity.

evolutionary biology↗

bioRxiv2023

Extinct and extant termites reveal the fidelity of behavior fossilization in amber

Fossils encompassing multiple individuals provide rare direct evidence of behavioral interactions among extinct organisms. However, the fossilization process can alter the spatial relationship between individuals and hinder behavioral reconstruction. Here, we report a Baltic amber inclusion preserving a female-male pair of the extinct termite species Electrotermes affinis. The head-to-abdomen contact in the fossilized pair resembles the tandem courtship behavior of extant termites, although their parallel body alignment differs from the linear alignment typical of tandem runs. To solve this inconsistency, we simulated the first stage of amber formation, the immobilization of captured organisms, by exposing living termite tandems to sticky surfaces. We found that the posture of the fossilized pair matches trapped tandems and differs from untrapped tandems. Thus, the fossilized pair likely is a tandem running pair, representing the first direct evidence of the mating behavior of extinct termites. Furthermore, by comparing the positions of partners on a sticky surface and in the amber inclusion, we estimated to 67% the probability that the leader role in the fossilized tandem was performed by a male. Our results demonstrate that past behavioral interactions can be reconstructed despite the spatial distortion of body poses during fossilization. Our taphonomic approach clarifies how certain behaviors can be inferred from fossil occurrences.

evolutionary biology↗

bioRxiv2021

Integrated phylogenomics and fossil data illuminate the evolution of beetles

With over 380,000 described species and possibly several million more yet unnamed, beetles represent the most biodiverse animal order. Recent phylogenomic studies have arrived at considerably incongruent topologies and widely varying estimates of divergence dates for major beetle clades. Here we use a dataset of 68 single-copy nuclear protein coding genes sampling 129 out of the 194 recognized extant families as well as the first comprehensive set of fully-justified fossil calibrations to recover a refined timescale of beetle evolution. Using phylogenetic methods that counter the effects of compositional and rate heterogeneity we recover a topology congruent with morphological studies, which we use, combined with other recent phylogenomic studies, to propose several formal changes in the classification of Coleoptera: Scirtiformia and Scirtoidea sensu nov., Clambiformia ser. nov. and Clamboidea sensu nov., Rhinorhipiformia ser. nov., Byrrhoidea sensu nov., Dryopoidea stat. res., Nosodendriformia ser. nov., and Staphyliniformia sensu nov., alongside changes below the superfamily level. The heterogeneous former superfamily Cucujoidea is divided into three monophyletic groups: Erotyloidea stat. nov., Nitiduloidea stat. nov., and Cucujoidea sensu nov. Our divergence time analysis recovered an evolutionary timescale congruent with the fossil record: a late Carboniferous origin of Coleoptera, a late Paleozoic origin of all modern beetle suborders, and a Triassic-Jurassic origin of most extant families. While fundamental divergences within beetle phylogeny did not coincide with the hypothesis of a Cretaceous Terrestrial Revolution, many polyphagan superfamilies exhibited increases in richness with Cretaceous flowering plants.

zoology↗

bioRxiv2021

Compositional phylogenomic modelling resolves the 'Zoraptera problem': Zoraptera are sister to all other polyneopteran insects

The evolution of wings propelled insects to their present mega-diversity. However, interordinal relationships of early-diverging winged insects and the timescale of their evolution are difficult to resolve, in part due to uncertainties in the placement of the enigmatic and species-poor order Zoraptera. The Zoraptera problem has remained a contentious issue in insect evolution since its discovery more than a century ago. This is a key issue because different placements of Zoraptera imply dramatically different scenarios of diversification and character evolution among polyneopteran. Here, we investigate the systematic placement of Zoraptera using the largest protein-coding gene dataset available to date, deploying methods to mitigate common sources of error in phylogenomic inference, and testing historically proposed hypotheses of zorapteran evolution. We recover Zoraptera as the earliest-diverging polyneopteran order, while earwigs (Dermaptera) and stoneflies (Plecoptera) form a monophyletic clade (Dermoplectopterida) sister to the remainder of Polyneoptera. The morphology and palaeobiology of stem-zorapterans are informed by Mesozoic fossils. The gut content and mouthparts of a male specimen of Zorotypus nascimbenei from Kachin amber (Cretaceous) reveal a fungivorous diet of Mesozoic zorapterans, akin to extant species. Based on a set of 42 justified fossil and stratigraphic calibrations, we recover a Devonian origin of winged insects and Polyneoptera, suggesting that these groups coincided with the rise of arborescence during the diversification of early terrestrial plants, fungi, and animals. Our results provide a robust framework for understanding the pattern and timescale of early winged insect diversification.

zoology↗

bioRxiv2019

Evolution of leaf-cutter behavior in bees (Hymenoptera: Megachilidae) as inferred from total-evidence tip-dating analyses

A unique feature among bees is the ability of some species of Megachile s.l. to cut and process fresh leaves for nest construction. The presence of razors between the female mandibular teeth (interdental laminae) to facilitate leaf-cutting (LC) is a morphological novelty that might have triggered a subsequent diversification in this group. However, we have a limited understanding of the evolutionary origins of this behavior and associated structures. Herein, we use total-evidence tip-dating analyses to infer the origin of LC bees and patterns of variation of interdental laminae. Our datasets included five nuclear genes, representatives of all fossil taxa, 80% of the extant generic-level diversity of Megachilidae, and the full range of generic and subgeneric diversity of Megachilini. Our analyses support the notion of a recent origin of LC bees (15-25 Ma), casting doubts on Eocene trace fossils attributed to these bees. We demonstrate that interdental laminae developed asynchronicaly from two different structures in the mandible (teeth or fimbrial ridge), and differ in their phenotypic plasticity. Based on the phylogenetic results, we propose robust classificatory solutions to long-standing challenges in the systematics of Megachilidae. We discuss the implications of our findings as a foundational framework to develop novel evolutionary, ecological, and functional hypotheses on this behavior.

evolutionary biology↗