On a new genus of dwarf tarantulas (Araneae: Mygalomorphae: Theraphosidae) endemic from Peru: evidence from morphology and molecular phylogeny, with description of three new species

Posted by
  On a new genus of dwarf tarantulas ( Araneae : Mygalomorphae : Theraphosidae ) endemic from Peru: evidence from morphology and molecular phylogeny, with description of three new species Abstract Recent field campaigns conducted in Peru along with the examination of museum specimens allowed us to identify small tarantulas that do not fit with any known Theraphosidae genera. Morphology and additional molecular evidence from the mitochondrial gene COI led us to propose Kiskalla gen. nov . from southern Peru, at Puno region. Three new species of Kiskalla gen. nov . ( K. ignacioi sp. nov ., K. yeisoni sp. nov . and K. zukuapasanka sp. nov .) are herein described, diagnosed and illustrated. Kiskalla gen. nov . differs from the known Theraphosinae genera in the presence of lateral stripes on the abdomen and a small dorsal arrowhead-shaped patch of type III urticating setae, presence of a large number of spines on all legs, short and stout setae on the dorsal metatarsi encirc...

Genome of the green-head ant, Rhytidoponera metallica, reveals mechanisms of toxin evolution in a genetically hyper-diverse eusocial species

Posted by

 


Genome of the green-head ant, Rhytidoponera metallica, reveals mechanisms of toxin evolution in a genetically hyper-diverse eusocial species

Abstract

Background

While ants are textbook examples of eusocial animals in which altruistic behavior is maintained through kin selection, several ants form genetically diverse colonies that challenge this concept. One example is the Australian green-head ant (Rhytidoponera metallica) whose colonies harbor such extreme genetic variation that they have been speculated to represent an unstable form of eusociality. Yet, R. metallica is among the most successful ants on the Australian subcontinent. This success has been hypothesized to be partly due to the diverse venoms harbored within each colony. However, the genomic basis and evolutionary scenarios that maintain this toxin diversity remain unknown.

Results

To examine toxin genomic architecture, quantify individual-level genetic variation, and identify both proximate and ultimate mechanisms that have facilitated the toxin diversity in R. metallica, we generate a high-quality draft genome from a single worker. Most ectatotoxin genes are in clusters that contain evidence of multiple, complex gene-family expansions, some of which are likely explained by the presence of transposable elements. We also show that toxin regions of the genome exhibit elevated genetic variation despite being under strong selection and that this variation can translate to phenotypic diversity through toxin alleles with different functional properties.

Conclusions

Taken together, our results point to classical gene duplication and diversification as the main evolutionary mechanism by which the main toxin family in ant venoms evolves, suggest toxin-gene functional diversification under frequency-dependent selection maintains colony-level venom hypervariability in R. metallica, and provide new insight into the role of multi-level selection in eusocial animals.



Isaksen, A., Nachtigall, P.G., Araya, R.A. et al. Genome of the green-head ant, Rhytidoponera metallica, reveals mechanisms of toxin evolution in a genetically hyper-diverse eusocial species. Genome Biol 26, 306 (2025). https://doi.org/10.1186/s13059-025-03777-2