Biology subjects

Schultz, T. R.

Publications and source records attributed to Schultz, T. R..

3 recordsLinked to original sources

bioRxiv2026

The Evolution of Biomineral Armor in Fungus-farming Ants

Biomineralization has enabled remarkable adaptations across the animal kingdom, including defensive structures and rock-grinding teeth. Although calcium carbonate is a common biogenically formed mineral found in all extant animal phyla, it is only recently known in insects and almost universally occurs with minimal magnesium content. A high-Mg calcite armor layer, covering most of the exoskeleton, was recently discovered in the fungus-farming ant Acromyrmex echinatior. Here, using a combination of scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction, paired with genome-scale phylogenetic analysis based on ultraconserved elements (UCEs), we characterize the evolution of biomineralization in fungus-farming ants. We show the presence of high-Mg calcite biomineral in 35 of 50 fungus-farming ant species studied, including taxa that span all major agricultural lineages. The biomineral is absent in all 16 myrmicine outgroup ant species, indicating an origin of the biomineral within ant agriculture, with ancestral state reconstruction analysis slightly supporting multiple origins within the fungus-farming ant clade. We then show that the occurrence of the biomineral is closely associated with the ancient mutualism with antimicrobial-producing Pseudonocardia, finding biomineral presence to be significantly correlated with the Pseudonocardia symbiont and the cuticular symbiotic structures that maintain these bacteria. Furthermore, we reveal significant inter-species variation in mineral composition and coverage, as well as intra-colony caste-specific differences, highlighting its adaptive complexity. Collectively, this work demonstrates that the innovation of a high-Mg calcite armor is strongly associated with the evolution of ant agriculture, revealing a rare biomineral to be widespread in the fungus-farming ants.

evolutionary biology↗

bioRxiv2026

Carbon dioxide sequestration into biomineral armor by ants

Over geologic time, Earths climate has been shaped by the capture and conversion of atmospheric carbon dioxide (CO2) into stable carbonate minerals, including dolomite [CaMg(CO3)2]. Accelerating natural carbon mineralization offers significant potential for mitigating anthropogenic climate change. Using stable carbon isotope tracking, nano-scale secondary ion mass spectroscopy, and 13C SSNMR, we show that, paralleling global biosphere-level processes, Sericomyrmex amabilis fungus-farming ants rapidly convert CO2 in their nest chambers into a biomineral layer covering their exoskeletons. We further reveal that biogenic carbon mineralization by these ants produces partially ordered dolomite. This rapid sequestration of CO2 into defensive armor in ants provides a fascinating natural example of mediation of potentially toxic accumulation of atmospheric CO2 that could inform human efforts to mitigate climate change.

ecology↗

bioRxiv2017

Compositional heterogeneity and outgroup choice influence the internal phylogeny of the ants

Knowledge of the internal phylogeny and evolutionary history of ants (Formicidae), the worlds most species-rich clade of eusocial organisms, has dramatically improved since the advent of molecular phylogenetics. A number of relationships at the subfamily level, however, remain uncertain. Key unresolved issues include placement of the root of the ant tree of life and the relationships among the so-called poneroid subfamilies. Here we assemble a new data set to attempt a resolution of these two problems and carry out divergence dating, focusing on the age of the root node of crown Formicidae. For the phylogenetic analyses we included data from 110 ant species, including the key species Martialis heureka. We focused taxon sampling on non-formicoid lineages of ants to gain insight about deep nodes in the ant phylogeny. For divergence dating we retained a subset of 62 extant taxa and 42 fossils in order to approximate diversified sampling in the context of the fossilized birth-death process. We sequenced 11 nuclear gene fragments for a total of ~7.5 kb and investigated the DNA sequence data for the presence of among-taxon compositional heterogeneity, a property known to mislead phylogenetic inference, and for its potential to affect the rooting of the ant phylogeny. We found sequences of the Leptanillinae and several outgroup taxa to be rich in adenine and thymine (51% average AT content) compared to the remaining ants (45% average). To investigate whether this heterogeneity could bias phylogenetic inference we performed outgroup removal experiments, analysis of compositionally homogeneous sites, and a simulation study. We found that compositional heterogeneity indeed appears to affect the placement of the root of the ant tree but has limited impact on more recent nodes. We put forward a novel hypothesis regarding the rooting of the ant phylogeny, in which Martialis and the Leptanillinae together constitute a clade that is sister to all other ants. After correcting for compositional heterogeneity this emerges as the best-supported hypothesis of relationships at deep nodes in the ant tree. The results of our divergence dating under the fossilized birth-death process and diversified sampling suggest that the crown Formicidae originated during the Albian or Aptian ages of the Lower Cretaceous (103-124 Ma). In addition, we found support for monophyletic poneroids comprising the subfamilies Agroecomyrmecinae, Amblyoponinae, Apomyrminae, Paraponerinae, Ponerinae, and Proceratiinae, and well-supported relationships among these subfamilies except for the placement of Proceratiinae and (Amblyoponinae + Apomyrminae). Our phylogeny also highlights the non-monophyly of several ant genera, including Protanilla and Leptanilla in the Leptanillinae, Proceratium in the Proceratiinae, and Cryptopone, Euponera, and Mesoponera within the Ponerinae.

evolutionary biology↗