New locality records and future habitat suitability of Sassanidotus gracilis (Birula, 1900) (Scorpiones: Buthidae) in the Iran–Afghanistan–Pakistan arid belt

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  New locality records and future habitat suitability of Sassanidotus gracilis (Birula, 1900) (Scorpiones: Buthidae) in the Iran–Afghanistan–Pakistan arid belt Abstract This study reports new locality records from Iran and a climate-based habitat suitability assessment for Sassanidotus gracilis (Birula, 1900) (Scorpiones: Buthidae) in the Iran–Afghanistan–Pakistan arid belt. We document new specimens from Sistan and Baluchestan Province, Iran, with an updated distribution map and illustrations, and we model the species' potential distribution across south-eastern Iran and adjacent parts of Afghanistan and Pakistan. Habitat suitability was associated mainly with precipitation seasonality, precipitation of the wettest month, precipitation of the driest month, and slope. In an arid setting these rainfall variables are unlikely to indicate a need for moist habitat; they more plausibly track seasonal productivity and the terrain features that provide shelter. Present-day suitable areas...

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 mygalomorphs (trapdoor spiders and their kin) generally possess more repetitive genomes with similar composition compared to their much more diverse sister lineage, the araneomorphs. We report mygalomorphs recover a lower number of completed BUSCOs than araneomorph spiders, a finding not correlated with sequencing coverage, as mygalomorphs have a portion of missing or derived BUSCOs in the current arachnid dataset. Across the Araneoidea (orb-weaving spiders and their kin), there is a correlation between decreasing genome size and repeat content, suggesting repetitive elements are being lost or removed. Importantly, visualization of macrosynteny across available genomes highlights structural rearrangements and allows identification of previously unreported sex chromosomes. This new, high-quality mygalomorph genome will provide new avenues of exploration for arachnid evolutionary biology.

Image Credit: “Taxonomic revision of the tarantula genus Aphonopelma Pocock, 1901 (Araneae, Mygalomorphae, Theraphosidae) within the United States”, in ZooKeys, volume 560, 2016, DOI:10.3897/zookeys.560.6264, pages 1–340

Briggs, E. J., Noble-Stuen, A. J., & Hamilton, C. A. Big Spider, Big Genome: Chromosome-level genome of a North American tarantula (Aphonopelma marxi) and comparative genomics across 300 million years of spider evolution. Genome Biology and Evolution. https://doi.org/10.1093/gbe/evag081