The Mediterranean as a melting pot: Phylogeography of Loxosceles rufescens (Sicariidae) in the Mediterranean Basin

Abstract

The species Loxosceles rufescens is native to the Mediterranean but considered cosmopolitan because it has been dispersed worldwide. A previous study revealed 11 evolutionary lineages across the Mediterranean, grouped into two main clades, without any clear phylogeographic pattern. The high genetic diversity within this species (p-distances of up to 7.8% in some Mediterranean lineages), together with the results obtained with different species delimitation methods (GMYC, TCS) could indicate the existence of cryptic species. Here we compare the mitochondrial and microsatellite diversity to elucidate if the lineages of L. rufescens in the Mediterranean should be considered different species (cryptic species) or populations of the same species. To do so, we analyzed the cox1 diversity of 196 individuals, of which, we genotyped 148, sampled from 19 localities across the Mediterranean. STRUCTURE analyses of microsatellite data identified two genetic clusters of L. rufescens. One cluster included individuals from Western Mediterranean localities (Iberian Peninsula, Morocco, Balearic Islands) and Israel, while the second one grouped individuals from Italian and Greek localities, including Sardinia, Sicily and Tunisia. These patterns suggest that geographic proximity is the more significant factor in the clustering with microsatellite data and shows the existence of gene flow between the nearest geographic areas, even if the individuals belong to different mitochondrial lineages or clades. The lack of correspondence between both genetic markers suggests that the evolutionary lineages found within L. rufescens should not be considered different species. We conclude that these phylogenetic linages and their distribution may be the result of the maternal evolutionary history of the species and human-mediated dispersion.

A Primer on Spider Assemblages in Levantine Caves: The Neglected Subterranean Habitats of the Levant—A Biodiversity Mine

“…Placing those four species on a cave-affinity continuum provides a better understanding of their distribution in caves. Loxosceles rufescens is an opportunistic synanthropic species common in the Mediterranean basin in houses and other manmade habitats (and introduced to other areas around the world) [52]. Although it can be found in shaded natural habitats such as caves and under stones [33], and is very common in caves as reported above, it is not a cave specialist.…”

Integrative taxonomy reveals first record of Loxosceles rufescens (Dufour, 1820) (Araneae, Sicariidae) in the Philippines

“… Loxosceles rufescens originated from North Africa, probably Morocco and transported within the Mediterranean Basin through human agencies and its own means ( Duncan et al 2010 , Planas et al 2014 , Nentwig et al 2017 ). The unintentional, human-mediated introduction of this spider also brought them to the United States ( Gertsch and Ennik 1983 , Massa et al 2018 ). Currently, the species is now spread through the islands of the Atlantic, Madagascar, Hawaii and in the areas of Australia, Mexico, Iran, Afghanistan, Peru, Macaronesia and South Africa ( Chomphuphuang et al 2016 , Gertsch and Ennik 1983 , World Spider Catalog 2023 Chomphuphuang et al 2016,).…”

“…The spider can be easily spread through human means as they are able to resist long periods of starvation and they are highly synanthropic (i.e. live in close association with humans and benefits from their habitats, surroundings and activities; Massa et al (2018) ). They prefer to hide in wooden objects, cardboard boxes, containers and other structures that have small crevices, which make them easy to transport along with other goods ( Nentwig et al 2017 ).…”

“…Despite their invasiveness and potential harm, L. rufescens do not disperse on their own means easily. All Loxosceles species have low dispersal capacity and do not balloon like other spiders ( Vetter 2008 , Greene et al 2009 , Massa et al 2018 ). They are usually sedentary and prefer to stay in the same location for long periods of time ( Massa et al 2018 ).…”

“…All Loxosceles species have low dispersal capacity and do not balloon like other spiders ( Vetter 2008 , Greene et al 2009 , Massa et al 2018 ). They are usually sedentary and prefer to stay in the same location for long periods of time ( Massa et al 2018 ). In casual conversations with the locals from the residential houses near the cave, they said that there are no sightings of L. rufescens in their houses.…”