Biology subjects

Sanchez-Vialas, A.

Publications and source records attributed to Sanchez-Vialas, A..

3 recordsLinked to original sources

bioRxiv2025

Evolution and comparative genomics of tick-associated endosymbionts: insights into metabolic pathways and historical biogeographic patterns

AbstractTicks (Ixodida) are the second most important vectors of infectious diseases in vertebrates, after mosquitoes. They also maintain mutualistic relationships with bacteria, such as endosymbionts that provide essential B vitamins absent in their blood diet. The most studied endosymbionts belong to the genera Coxiella, Midichloria, and Francisella. Francisella includes endosymbionts (FE), pathogens (FP), putative intermediates (FI), and free-living (FL) strains, making them valuable for evolutionary and comparative genomics. In this study, total DNA from six adult female ticks of the genera Hyalomma and Amblyomma was sequenced to obtain new FE genomes. Additionally, two deep metagenomes from public data were assembled, resulting in a dataset of 22 Francisella strains. This dataset was used to reconstruct a phylogenomic framework and compare vitamin biosynthesis and virulence pathways. An MLST-based dense phylogeny was also built to explore biogeographic patterns. The resulting phylogenomic tree shows FE form a monophyletic group derived from FP, possibly due to historical biogeography or recent horizontal transfers. Comparative analyses reveal that FE retain key metabolic pathways while losing nonessential ones, reflecting a selective genome reduction. These results advance our understanding of symbiont evolution in a changing world, revealing molecular adaptations that underpin tick- symbiont relationships and offering genomic insights with potential applications for disease control.

evolutionary biology↗

bioRxiv2025

Croaking for haste: How long does it take to describe a frog species since its discovery?

Global biodiversity faces severe anthropogenic threats, with alarming extinction rates projected for the near future. Most of Earths diversity remains undescribed, meaning countless species are doomed to extinction before being documented. Since current conservation laws consider only described species, the time to achieve a representative inventory of global biodiversity is crucial for effective conservation. Amphibians, the most endangered vertebrate class, exemplify the challenge: while the number of threatened species rises, new species descriptions rapidly increase, and hundreds of candidate species are flagged annually worldwide. We analyzed all anuran species described from the year 2000 to 2023 across four biodiversity-rich tropical regions to investigate the time required to describe new frog species. We quantified the time needed to collect the type series, the number and timing of expeditions, the lag between collection and publication of the species description, and the total time. Additionally, we explored temporal trends and the effect of selected abiotic variables. On average, it takes 11.3 years to formally describe a frog species since the collection of the first specimen, with 4.5 years spent on specimen collection and 6.8 years on description and publication. These figures were consistent across three of the four regions analyzed. Alarmingly, the time required to describe new species is globally increasing, exacerbating the so-called taxonomic impediment. Only 36% of species were described within five years of collection, highlighting the importance of biological collections as reservoirs of undescribed diversity while also calling for specimen revision after expeditions. These results raise concerns about the effectiveness of current taxonomic and conservation practices in addressing the biodiversity crisis. We call for a global effort to prioritize taxonomic research and discuss innovative taxonomic and conservation approaches. Under current practices, and given the observed timelines, we will lose the race against extinction for many species.

zoology↗

bioRxiv2023

New insights into the systematics of the Afrotropical Amblyomma marmoreum complex (Acari, Ixodidae) and a novel Rickettsia africae strain using morphological and metagenomic approaches

The Amblyomma marmoreum complex includes some Afrotropical species, such as Amblyomma sparsum, a three-host tick that parasitizes reptiles, birds, and mammals, and is a recognized vector of Ehrlichia ruminatum. However, the lack of morphological, genetic and ecological data on A. sparsum has caused considerable confusion in its identification among A. marmoreum complex members. In this study, we used microscopy and metagenomic approaches to analyze A. sparsum ticks collected from a puff adder snake (Bitis arietans) in southwest Senegal (an endemic rickettsioses area) in order to supplement previous morphological descriptions, provide novel genomic data for the A. marmoreum complex, and search for some associated spotted fever agent. Based on stereoscope and scanning electron microscopy (SEM) morphological evaluations, we provided high-quality images and new insights about punctation and enameling in the male of A. sparsum to facilitate identification for future studies. Additionally, the metagenomic approach allowed us assembly the complete mitochondrial genome of A. sparsum, as well as the nearly entire chromosome and complete plasmid sequences of a novel Rickettsia africae strain. Phylogenomic analyses showed a close relationship between A. sparsum and A. nuttalli for the first time and confirmed the position of A. sparsum within the A. marmoreum complex. Our results provide new insights into the systematic of A. sparsum and A. marmoreum complex, as well as the genetic diversity of R. africae in Afrotropical region. Future studies should consider the possibility that A. sparsum may be a competent vector for R. africae.

zoology↗