Wednesday, December 11, 2019

[Arachnida • 2019] Loxosceles tenochtitlanUnder An Integrative Taxonomic Approach: the Description of A New Species of the Genus Loxosceles (Araneae, Sicariidae) from Mexico City

 Loxosceles tenochtitlan Valdez-Mondragón & Navarro-Rodríguez

in Valdez-Mondragón, Navarro-Rodríguez, Solís-Catalán, Cortez-Roldán & Juárez-Sánchez, 2019. 

A new species of the spider genus Loxosceles Heineken & Lowe, 1832, Loxosceles tenochtitlan Valdez-Mondragón & Navarro-Rodríguez, sp. nov., is described based on adult male and female specimens from the states of Mexico City, Estado de Mexico and Tlaxcala. Integrative taxonomy including traditional morphology, geometric and lineal morphology, and molecules (DNA barcodes of cytochrome c oxidase subunit 1 (CO1) and internal transcribed spacer 2 (ITS2)), were used as evidence to delimit the new species. Four methods were used for molecular analyses and species delimitation: 1) corrected p-distances under neighbor joining (NJ), 2) automatic barcode gap discovery (ABGD), 3) general mixed yule coalescent model (GMYC), and 4) poisson tree processes (bPTP). All molecular methods, traditional, geometric and lineal morphology were consistent in delimiting and recognizing the new species. Loxosceles tenochtitlan sp. nov. is closely related to L. misteca based on molecular data. Although both species are morphologically similar, the average p-distance from CO1 data was 13.8% and 4.2% for ITS2 data. The molecular species delimitation methods recovered well-supported monophyletic clusters for samples of L. tenochtitlan sp. nov. from Mexico City + Tlaxcala and for samples of L. misteca from Guerrero. Loxosceles tenochtitlan sp. nov. is considered a unique species for three reasons: (1) it can be distinguished by morphological characters (genitalic and somatic); (2) the four different molecular species delimitation methods were congruent to separate both species; and (3) there is variation in leg I length of males between both species, with the males of L. misteca having longer legs than males of L. tenochtitlan sp. nov., also morphometrically, the shape of tibiae of the palp between males of both species is different.

Keywords: DNA barcodes, ecological niche modeling, Loxosceles tenochtitlan sp. nov., species delimitation, taxonomy

Family Sicariidae Keyserling, 1880

Genus Loxosceles Heineken & Lowe, 1832
Type species: Loxosceles rufescens (Dufour, 1820).

Figures 1–6. Live specimens of  Loxosceles tenochtitlan sp. nov. from Street Juárez Norte #214, Huamantla, Municipality Huamantla, Tlaxcala, Mexico
1–3 females 4–6 males.
Photographs by Jared Lacayo-Ramírez (2019).

Loxosceles tenochtitlan Valdez-Mondragón & Navarro-Rodríguez, sp. nov.

Etymology: The species is a noun in apposition dedicated to Tenochtitlán (Nahuatl language) city, a large Mexica city-state in what is now Mexico City where the type locality is located. Tenochtitlán was built on an island in what was then Lake Texcoco in the Valley of Mexico, being the capital of the expanding Aztec Empire in the 15th century.

Diagnosis: The male of Loxosceles tenochtitlan sp. nov. morphologically resembles those of Loxosceles misteca Gertsch, 1958 (Figs 29–31, 38–47) from Guerrero; however, in the new species, the curvature of the basal-ventral part of the tibia of the male palp is less pronounced than in L. misteca¸ where it is prominent (Figs 23, 25, 42, 44, 48–55). Both species have a spatula-shaped embolus; in the new species, the embolus is slightly wider than that of L. misteca (Figs 23, 25, 26, 42, 44, 45, 48–55, 62–65). In dorsal view, the embolus basally is wider in L. tenochtitlan sp. nov. than in L. misteca (Figs 26, 45). Leg I length of males of L. tenochtitlan sp. nov. is shorter than legs I of L. misteca (Fig. 81). The seminal receptacles of females of L. tenochtitlan sp. nov. and L. misteca are similar, however in the new species the distance between the base of the receptacles is larger than in L. misteca (Figs 56–61, 66–69), also, the genitalia of L. tenochtitlan sp. nov. has small accessory lobes receptacles on each side (Figs 56–61), which are absent on L. misteca (Figs 66–69).

 Alejandro Valdez-Mondragón, Claudia I. Navarro-Rodríguez, Karen P. Solís-Catalán, Mayra R. Cortez-Roldán and Alma R. Juárez-Sánchez. 2019. Under An Integrative Taxonomic Approach: the Description of A New Species of the Genus Loxosceles (Araneae, Sicariidae) from Mexico City. ZooKeys. 892: 93-133. DOI: 10.3897/zookeys.892.39558