Scorpion systematics and taxonomy have recently shown a need for revision, partially due to insights from molecular techniques. Scorpion taxonomy has been difficult with morphological characters as disagreement exists among researchers with character choice for adequate species delimitation in taxonomic studies. Within the family Buthidae, species identification and delimitation is particularly difficult due to the morphological similarity among species and extensive intraspecific morphological diversity. The genus Centruroides in the western hemisphere is a prime example of the difficulty in untangling the taxonomic complexity within buthid scorpions. In this paper, we present phylogeographic, Ecological Niche Modeling, and morphometric analyses to further understand how population diversification may have produced morphological diversity in Centruroides vittatus (Say, 1821). We show that C. vittatus populations in the Big Bend and Trans-Pecos region of Texas, USA are phylogeographically distinct and may predate the Last Glacial Maximum (LGM). In addition, we suggest the extended isolation of Big Bend region populations may have created the C. vittatus variant once known as C. pantheriensis.
We examined the population structure of sand scorpions (Paruroctonus mesaensis) by performing genetic and morphological analyses. Sand scorpions were expected to show large genetic distances among populations because they are limited to sandy habitats. However, allozyme analysis showed only moderate genetic differentiation among populations. The morphological analysis showed a geographical association among regional sites. A positive association was found among genetic, morphological and geographical distance matrices. However, the morphological distance matrix showed a higher correlation value with geographical distance than with genetic distance. This result suggests that local environmental conditions may affect scorpion morphology more than they affect genetic structure among populations. The sand scorpion population structure can be described as one with gene flow among populations in the middle of the range and increased isolation along the range boundaries. The major mechanism of genetic exchange is probably sand corridors that periodically connect different sand dune systems. As the age of the North American Sonoran Desert may be less than 10000 years, it is also possible that isolation has not existed long enough to differentiate the populations to a greater extent.
Body tissue and venom glands from an eastern population of the scorpion Centruroides vittatus (Say, 1821) were homogenized and molecular constituents removed to characterize putative sodium β toxin gene diversity, RT-qPCR, transcriptomic, and proteomic variation. We cloned sodium β toxins from genomic DNA, conducted RT-qPCR experiments with seven sodium β toxin variants, performed venom gland tissue RNA-seq, and isolated venom proteins for mass spectrophotometry. We identified >70 putative novel sodium β toxin genes, 111 toxin gene transcripts, 24 different toxin proteins, and quantified sodium β toxin gene expression variation among individuals and between sexes. Our analyses contribute to the growing evidence that venom toxicity among scorpion taxa and their populations may be associated with toxin gene diversity, specific toxin transcripts variation, and subsequent protein production. Here, slight transcript variation among toxin gene variants may contribute to the major toxin protein variation in individual scorpion venom composition.
The complete mitochondrial genome (mitogenome) of the Striped scorpion (Centruroides vittatus) was assembled from Illumina-based whole genome sequencing. The circular genome is 14,602 bp in length with 13 protein coding genes, 21 tRNA, two rRNAs, a translocation-inversion of tRNALeu compared to the horse shoe crab mitogenome, and the absence of tRNAAsp. The A + T content of the mitogenome is 68.1%. Our Bayesian and Maximum Likelihood phylogenetic analyses placed the C. vittatus mitogenome as a sister group of C. limpidus and nestled within the new world Buthids.
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