Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution

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  Image Credit: WikiCommons Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution Abstract The comparison of chromosome-level genomes allows biologists to investigate new axes of organismal evolution. Spiders comprise a significant proportion of known arachnid diversity, with many complex morphologies and unique natural histories, yet comparative genomics in spiders has been limited due to the number of available genomes. We present a de novo chromosomal reference genome of a mature male tarantula, Aphonopelma marxi, and comparatively examine spider genome evolution across the Order Araneae. Using PacBio HiFi and Hi-C sequencing, the final 6.5 Gb assembly consists of 17 autosomes, 1 X chromosome, and 127 unplaced scaffolds, with an N50 of 370 Mb and Arachnida (odb10; 2934 genes) BUSCO of 96.7%. By comparing 20 additional spider genomes from 15 families, we find mygalomo...

Between cloud forests and museums: testing tarantula (Araneae: Theraphosidae) generic boundaries reveals a new montane genus from Ecuador and Colombia

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Between cloud forests and museums: testing tarantula (Araneae: Theraphosidae) generic boundaries reveals a new montane genus from Ecuador and Colombia

Abstract

This study presents the first comprehensive morphology-based phylogenetic analysis encompassing all described species of Cymbiapophysa Gabriel and Sherwood, 2020. We provide an updated and refined phylogenetic hypothesis that resolves relationships among closely related taxa and supports the recognition of a new theraphosid clade. Preliminary analysis of this clade suggests that unconventional characters of the male palpal bulb may have untapped potential for generic-level differentiation within Theraphosidae. Further, the recovered topologies support the recognition of a new genus, Tandayarachne gen. nov. The new genus is composed of a new species from the Tandayapa Cloud Forest Station, Western Ecuador, and a previously misplaced species of Neischnocolus Petrunkevitch, 1925 from Colombia. Notably, the paratype female of the latter species is reassigned to Neischnocolus and proposed here as a new species based on distinct spermathecal morphology. Integrating our phylogenetic hypothesis with character optimization and ancestral character state reconstruction, we identify evolutionary trends in keel-nested characters, further providing support for genera delimitation on the studied clade. We discuss the current impediments facing the taxonomy of the subfamily Theraphosinae, with a specific focus on the underestimation of proper morphological analysis of the palpal bulbs in taxonomic assessments. Finally, we discuss the geographical distribution of the new genus and propose plausible scenarios to explain its disjunct distribution.


Pedro Peñaherrera-R., Juan M Guayasamin, Between cloud forests and museums: testing tarantula (Araneae: Theraphosidae) generic boundaries reveals a new montane genus from Ecuador and Colombia, Zoological Journal of the Linnean Society, Volume 205, Issue 3, November 2025, zlaf152, https://doi.org/10.1093/zoolinnean/zlaf152