Research Article |
Corresponding author: Alejandro Valdez-Mondragón ( lat_mactans@yahoo.com.mx ) Academic editor: Abel Pérez-González
© 2019 Alejandro Valdez-Mondragón, Claudia I. Navarro-Rodríguez, Karen P. Solís-Catalán, Mayra R. Cortez-Roldán, Alma R. Juárez-Sánchez.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Valdez-Mondragón A, Navarro-Rodríguez CI, Solís-Catalán KP, Cortez-Roldán MR, Juárez-Sánchez AR (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. https://doi.org/10.3897/zookeys.892.39558
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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.
DNA barcodes, ecological niche modeling, Loxosceles tenochtitlan sp. nov., species delimitation, taxonomy
The spider family Sicariidae Keyserling, 1880 comprises three genera: Hexophthalma Karsch, 1879 with eight species from Africa, Sicarius Walckenaer, 1847 with 21 species distributed in Central and South America, and Loxosceles Heineken & Lowe, 1832, with 139 described species worldwide (
Mexico has the highest diversity of Loxosceles worldwide, with 39 species, 37 native (not including the new species described here), and two introduced species: Loxosceles reclusa Gertsch & Mulaik, 1940 and Loxosceles rufescens (Dufour, 1820) (
Modern taxonomy uses multiple lines of evidence for species recognition, identification, diagnosis and delimitation. Several recently developed molecular delimitation methods have highlighted the extensive inconsistency in classical morphological taxonomy (
Currently, there are two separate tasks to which DNA barcodes are being applied in modern systematics. The first is distinguishing between species (equivalent to species identification or species diagnosis), and the second is the use of DNA data to discover new species (equivalent to species delimitation and species description) (
The primary aim of this study is to use an integrative taxonomic approach for the delimitation and description of a new species of Loxosceles from Mexico City. We analyzed DNA barcodes and used traditional morphology, ultra-morphology, geometric and linear morphometrics, biogeography, and ecological niche modeling for species delimitation. This is the first-time multiple lines of evidence have been used in the taxonomy of the genus.
The specimens of the new species were collected and deposited in 80% ethanol and labeled with their complete field data. The type specimens and additional examined material are deposited with their collection codes in the Laboratory of Arachnology (LATLAX), Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales (LBCTV), Institute of Biology, Universidad Nacional Autónoma de México (
AME anterior median eyes;
PLE posterior lateral eyes;
PLS posterior lateral spinnerets;
PME posterior median eyes.
The molecular analyses presented here are based on a total of 52 individuals from 11 species of Loxosceles, including the new species described here and two outgroups: Loxosceles rufescens (Dufour, 1820) and Scytodes thoracica (Latreille, 1802) (Table
Specimens sequenced for each species, DNA voucher numbers, localities, and GenBank accession numbers.
Species | DNA voucher LATLAX | Locality | GenBank accession number | |
---|---|---|---|---|
CO1 | ITS2 | |||
L. misteca | Ara0082 | Mexico: Guerrero | MK936272 | MK957212 |
Ara0089 | Mexico: Guerrero | MK936273 | MK957215 | |
Ara0090 | Mexico: Guerrero | MK936274 | MK957214 | |
Ara0084 | Mexico: Guerrero | MK936275 | MK957213 | |
Ara0236 | Mexico: Guerrero | MK936276 | – | |
Ara0237 | Mexico: Guerrero | MK936277 | – | |
L. tenochtitlan sp. nov. | Ara0146 | Mexico: Mexico City | MK936278 | MK957209 |
Ara0161 | Mexico: Mexico City | MK936279 | – | |
Ara0173 | Mexico: Tlaxcala | MK936280 | MK957210 | |
Ara0164 | Mexico: Tlaxcala | MK936281 | MK957211 | |
L. malintzi | Ara0100 | Mexico: Guerrero | MK936282 | MK957220 |
Ara0001 | Mexico: Puebla | MK936283 | MK957218 | |
Ara0002 | Mexico: Puebla | MK936284 | – | |
Ara0025 | Mexico: Puebla | MK936285 | MK957219 | |
Ara0072 | Mexico: Puebla | MK936286 | MK957222 | |
Ara0074 | Mexico: Puebla | MK936287 | MK957223 | |
Ara0101 | Mexico: Guerrero | MK936288 | – | |
Ara0004 | Mexico: Puebla | MK936289 | MK957221 | |
L. tenango | Ara0191 | Mexico: Hidalgo | MK936290 | – |
Ara0192 | Mexico: Hidalgo | MK936291 | MK957201 | |
Ara0045 | Mexico: Hidalgo | – | MK957195 | |
Ara0189 | Mexico: Hidalgo | – | MK957196 | |
Ara0190 | Mexico: Hidalgo | – | MK957197 | |
Ara0193 | Mexico: Hidalgo | – | MK957198 | |
Ara0188 | Mexico: Hidalgo | – | MK957200 | |
L. jaca | Ara0186 | Mexico: Hidalgo | MK936292 | MK957194 |
Ara0048 | Mexico: Hidalgo | MK936293 | – | |
Ara0046 | Mexico: Hidalgo | – | MK957192 | |
Ara0047 | Mexico: Hidalgo | – | MK957193 | |
Ara0183 | Mexico: Hidalgo | – | MK957199 | |
Loxosceles sp. 1 | Ara0175 | Mexico: Hidalgo | MK936294 | MK957208 |
Ara0181 | Mexico: Hidalgo | MK936295 | MK957206 | |
Ara0182 | Mexico: Hidalgo | MK936296 | MK957207 | |
Ara0174 | Mexico: Hidalgo | – | MK957202 | |
Ara0176 | Mexico: Hidalgo | – | MK957203 | |
Ara0177 | Mexico: Hidalgo | – | MK957204 | |
Ara0178 | Mexico: Hidalgo | – | MK957205 | |
L. nahuana | Ara0076 | Mexico: Hidalgo | MK936297 | MK957216 |
Ara0077 | Mexico: Hidalgo | MK936298 | – | |
Ara0079 | Mexico: Hidalgo | MK936299 | MK957217 | |
L. zapoteca | Ara0094 | Mexico: Guerrero | MK936300 | MK957224 |
Ara0220 | Mexico: Guerrero | MK936301 | – | |
Ara0227 | Mexico: Guerrero | MK936302 | – | |
L. colima | Ara0115 | Mexico: Colima | MK936303 | MK957224 |
Loxosceles sp. 2 | Ara0194 | Mexico: Guerrero | MK936304 | – |
Ara0198 | Mexico: Guerrero | MK936305 | – | |
Ara0199 | Mexico: Guerrero | MK936306 | – | |
Ara0205 | Mexico: Guerrero | MK936307 | – | |
Ara0209 | Mexico: Guerrero | MK936308 | – | |
Ara0210 | Mexico: Guerrero | MK936309 | – | |
Ara0204 | Mexico: Guerrero | MK936310 | – | |
L. rufescens | GenBank | Greece: Peloponnese | - | KR864735 |
Scytodes thoracica | GenBank | Turkey: Antalya | KR864739 |
Specimens for DNA extraction were preserved in ethanol (96%) and kept at -20 °C. DNA was isolated from legs, prosoma or complete specimens in the case of immatures. DNA extractions were done using a Qiagen DNeasy Tissue Kit following the protocol of
Gene | Primer name | Primer sequence (5'–3') | Reference |
---|---|---|---|
CO1 | LCO | GGT CAA CAA ATC ATA AAG ATA TTG G |
|
HCO | TAA ACT TCA GGG TGA CCA AAA AAT CA | ||
LCO-JJ | CHA CWA AYC ATA AAG ATA TYG G |
|
|
HCO-JJ | AWA CTT CVG GRT GCV CAA ARA ATC A | ||
ITS2 | 5.8S | CAC GGG TCG ATG AAG AAC GC | Ji et al. (2003), |
CAS28sB1d | TTC TTT TCC TCC SCT TAY TRA TAT GCT TAA |
Sequences were edited with the programs BioEdit v. 7.0.5.3 (
For molecular species delimitation four methods were used for analyzing the concatenated CO1+ITS2 matrix (1091 characters): 1) p-distances under neighbor joining (NJ) using MEGA v. 7.0, 2) automatic barcode gap discovery (ABGD) online version (
For the morphometric studies, tibiae of adult males in retrolateral views of L. tenochtitlan sp. nov. (N = 12) and L. misteca (N = 9) were analyzed using Make Fan 8 v. 1.0 software (
For georeferencing and corroboration of localities, two programs were used: GeoLocate online version (http://www.museum.tulane.edu/geolocate/) and Google Earth v. 7.1.5.1557. The geographic coordinates were transformed from NAD83 to WGS84 online on INEGI: Transformation of coordinates TRANINV (
Loxosceles rufescens (Dufour, 1820).
MEXICO: Mexico City: male holotype (LATLAX-T001) from Street Cruz Verde No. 132 (lat 19.2921, lon -99.174203; 2281 m), Tlalpan, 10-XII-2017, M. Sánchez-Vílchis leg. (inside house). Paratypes: 1 female (LATLAX-T002), 2 males (LATLAX-T003), 4 females (LATLAX-0004), same data as holotype.
MEXICO: Mexico City: 5 females, 1 immature (LATLAX-Ara 0539), same data as holotype. 3 males, 8 immatures (LATLAX-Ara 0540), same data as holotype. 1 male (LATLAX-Ara 0542), 19-I-2019, A. Valdez leg., same locality as holotype. 1 female, 1 immature (LATLAX-Ara0156) from Street Tepocatl #61, Pedregal de Santo Domingo (19.330101, -99.147210; 2256 m), Coyoacán, 02-VII-2017, R. Cansino López leg. 1 male (LATLAX-Ara1087) from Pedregal de Santo Domingo, (19.328704, -99.164989, 2273 m) Coyoacán, 21-VII-2017 R. Cansiano Lopéz leg. 1 male, 1 female, 1 immature (LATLAX-Ara 0193) Los Reyes Copilco, Fracc. Areada Dpto. 102-A (19.336984, -99.182979, 2272 m), Coyoacán, IX-2017, D. Guerrero leg. 1 female, 1 immature (LATLAX-Ara196) Los Reyes Copilco, Fracc. Areada Dpto. 102-A (19.336984, -99.182979, 2272 m), Coyoacán, XII-2017, D. Guerrero leg. 1 immature (LATLAX-Ara 0482) from Street Toriello Guerra, Cuitlahuac S/N (19.297228, -99.174510, 2269 m) Tlalpan, II-2018, D. Barrales leg. 1 male 1 immature (LATLAX-Ara 0487) from Street Toriello Guerra, Cuitlahuac S/N (19.297228, -99.174510, 2269 m) Tlalpan, II-2018, D. Barrales leg. 1 female (LATLAX-Ara 0507) from Street Tepocatl #61, Pedregal de Santo Domingo (19.330101, -99.147210; 2256 m), Coyoacán 09-VIII-2018, R. Cansino Lopéz leg. Estado de Mexico: 1 female (LATLAX-Ara 0529) from Street Juaréz #23, San Mateo Ixtacalco (19.702460, -19.187150, 2355 m), Municipality Cuautitlán Izcalli 05-III-2019, M. Cortez. Tlaxcala: 1 male, 3 females, 15 immatures (LATLAX-Ara0132) from Street Reforma #5, Santiago Tlacochcalco (19.26939, -98.22303, 2245 m), Municipality of Tepeyanco, 06-VI-2017, M. Cortez, A. Juárez, J. Valerdi Cols. 1 female (LATLAX-Ara0188) from the Trinidad Tenexyecac (19.335588, -98.315688, 2241 m), Municipality of Ixtacuixtla of Mariano Matamoros, 02-III-2018, E. Briones leg. 2 males, 3 females, 10 immatures (LATLAX-Ara0500) from North Street Juárez #214, Huamantla downtown (19.3168, -97.92245, 2511 m), Municipality Huamantla, 15-V-2018, A. Valdez, I. Navarro, P. Solís, A. Cabrera, D. Montiel. Cols. 6 males, 5 females, 46 immatures (LATLAX-Ara0501) from Street North Juárez #214, Huamantla downtown (19.3168, -97.92245, 2511 m), Municipality Huamantla, 08-VI-2018, A. Valdez, I. Navarro, P. Solís, A. Cabrera, D. Montiel. Cols. 6 male, 2 females, 46 immatures (LATLAX-Ara0502) from Santiago Tlacochcalco (19.26939, -98.22303, 2245 m), Municipality of Tepeyanco, 25-IV-2018, P. Solís, I. Navarro A. Juárez, J. Valerdi Cols.
Live specimens and urban microhabitat of Loxosceles tenochtitlan sp. nov. from Tlaxcala 14–17 specimens from Street Juárez Norte #214, Huamantla downtown, Municipality, Huamantla, Tlaxcala, Mexico 18 microhabitat where some specimens were collected from Street Reforma #5, Santiago Tlacochcalco, Municipality Tepeyanco, Tlaxcala, Mexico. Red arrows indicate the specific places where specimens were collected. Photographs 14–17 by José A. Castilla-Vázquez (2018–2019). Photograph 18 by Alma R. Juárez-Sánchez (2018).
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.
The male of Loxosceles tenochtitlan sp. nov. morphologically resembles those of Loxosceles misteca Gertsch, 1958 (Figs
Male (holotype; LATLAX-T001): Specimen collected manually, preserved and observed in 80% ethanol. Measurements: Total length (prosoma + opisthosoma) 6.70. Carapace 3.20 long, 2.90 wide. Clypeus length 0.45. Diameter of AME 0.13, PME 0.17, PLE 0.20; AME-PME 0.20 Labium: length 0.79, width 0.58. Sternum: length 1.80, width 1.62. Leg lengths: I (total 18.55): femur 5.00 / patella 1.10 / tibia 5.90 / metatarsus 5.35 / tarsus 1.20; II (20.98): 5.60 / 1.12 / 6.75 / 6.20 / 1.31; III (15.67): 4.40 / 1.10 / 4.45 / 4.60 / 1.12; IV (16.99): 4.75 / 1.02 / 4.92 / 5.10 / 1.20. Leg formula: 2-1-4-3.
Prosoma
: Carapace orange, longer than wide, piriform, with small and numerous setae laterally, with defined pale brown violin-shaped pattern dorsally, darker toward ocular region, carapace without spots (Fig.
Legs
: Coxae pale orange (Fig.
Chelicerae : Fused basally, chelated chelicerae laminae, reddish orange, stridulatory lines laterally. Fangs reddish orange, paler distally, with long and thin setae.
Opisthosoma
: Pale yellow, darker posteriorly, oval, longer than both width and height (Figs
Palps
: Trochanters orange, femora reddish brown, long and thin, patellae reddish brown; tibiae reddish orange, darker, oval, curved ventrally, almost straight dorsally, wider distally than ventrally (Figs
Female (paratype; LATLAX-T002): Specimen collected manually, preserved and observed in 80% ethanol. Measurements: Total length 10.40. Carapace 3.75 long, 3.25 wide. Clypeus length 0.55. Diameter of AME 0.16, PME 0.20, PLE 0.20; AME-PME 0.23 Labium: length 0.80, width 0.75. Sternum: length 2.05, width 1.75. Leg lengths: I (total 18.73): femur 5.10 / patella 1.20 / tibia 5.68 / metatarsus 5.50 / tarsus 1.25; II (19.79): 5.50 / 1.24 / 6.10 / 5.60 / 1.35; III (15.83): 4.50 / 1.25 / 4.50 / 4.50 / 1.08; IV (18.09): 5.10 / 1.20 / 5.18 / 5.37 / 1.24. Leg formula: 2-1-4-3.
Differs from the male as follows. Prosoma: Carapace paler orange, with darker brown violin-shaped pattern; ocular region dark brown (Fig.
Chelicerae : Wider than in the male. Slightly dark reddish brown, with stridulatory lines laterally. Fangs dark reddish orange.
Opisthosoma
: Opisthosoma pale yellow (Figs
Palps : Trochanters pale orange, femora pale brown, paler ventrally; patellae pale brown, tibiae and tarsi reddish surrounded with several long and sparse setae. Tibiae cylindrical, tarsi conical.
Genital area
: Seminal receptacles asymmetric, S-shaped, curved basally and apically with rounded lobes (Fig.
MALES. Mexico City: Males from Coyoacán are light brown, legs slightly darker than the carapace, males from Tlalpan are light brown, legs slightly darker than the carapace. Tlaxcala: Males from Santiago Tlacochcalco Municipality of Tepeyanco are light brown, legs slightly darker than the carapace and light brown, legs slightly darker than the carapace. Males from Huamantla are dark brown, legs slightly darker than the carapace. Mexico City: Coyoacán (N = 3): Tibia I 5.9–6.5 (x̄ = 6.1); carapace length (CL) 2.6–3.1 (x̄ = 2.9); carapace width (CW) 2.4–2.7 (x̄ = 2.5). Tlalpan (N = 3): Tibia I 6.0–7.6 (x̄ = 5.8); carapace length (CL) 2.2–3.2 (x̄ = 2.8); carapace width (CW) 2.5–2.7 (x̄ = 2.6). Tlaxcala: Santiago Tlacochcalco Municipality of Tepeyanco (N = 7): Tibia I 3.8–6.6 (x̄ = 5.0); carapace length (CL) 2.5–4.2 (x̄ = 3.1); carapace width (CW) 2.2–3.2 (x̄ = 2.7). Huamantla (N = 3): Tibia I 5.0–6.5 (x̄ = 5.8); carapace length (CL) 3.2–3.3 (x̄ = 3.2); carapace width (CW) 2.7–2.9 (x̄ = 2.8). FEMALES. Mexico City: Females from Coyoacán are dark brown, legs the same color as the carapace. Females from Tlalpan are dark brown, legs the same color as the carapace. Estado de Mexico: Female from San Mateo Ixtacalco, Municipality Cuautitlán Izcalli is dark brown, legs slightly darker than the carapace. Tlaxcala: Females from Santiago Tlacochcalco, Municipality of Tepeyanco are light brown, legs slightly darker than the carapace. Females from Huamantla are dark brown, legs the same color as the carapace and light brown, legs the same color as the carapace and light brown. A female from the Trinidad Tenexyecac, Municipality of Ixtacuixtla is light brown, legs the same color as the carapace. Mexico City: Coyoacán (N = 3): Tibia I 5.8–7.1 (x̄ = 6.7); carapace length (CL) 3.9–4.2 (x̄ = 4.1); carapace width (CW) 3.2–4.0 (x̄ = 3.7). Tlalpan (N = 6): Tibia I 4.6–6.3 (x̄ = 5.2); carapace length (CL) 1.7–4.0 (x̄ = 3.2); carapace width (CW) 1.8–3.3 (x̄ = 2.6). Estado de Mexico: San Mateo Ixtacalco, Municipality Cuautitlán Izcalli (N = 1) Tibia I 3.6; carapace length (CL) 2.5; carapace width (CW) 2.5. Tlaxcala: Santiago Tlacochcalco Municipality of Tepeyanco (N = 2): Tibia I 4.5, 5.3; carapace length (CL) 3.2, 3.3; carapace width (CW) 2.5, 2.9. Huamantla (N = 11): Tibia I 4.1–6.7 (x̄ = 5.1); carapace length (CL) 1.7–4.0 (x̄ = 3.3); carapace width (CW) 1.8–3.5 (x̄ = 2.7). Trinidad Tenexyecac, Municipality of Ixtacuixtla (N = 1): Tibia I 5.4; carapace length (CL) 3.3; carapace width (CW) 2.5.
There is little variation in the shape of the male palps, even those of specimens from different populations (Figs
The specimens of L. tenochtitlan sp. nov. (Figs
MEXICO: Mexico City, Tlaxcala, Estado de Mexico (Figs
MEXICO: Guerrero: male holotype (examined) (AMNH_IZC00327631) from Taxco, Municipality Taxco de Alarcón, Guerrero, Mexico, Date? 1946, Collected in the fall, Leo Isaacs leg.
MEXICO: Guerrero: 1 male, 1 female (CNAN-AR008985) from Cueva del Diablo, Acuitlapan (18.60106, -99.54318, 1581 m) Municipality Taxco de Alarcón, 04-VI-2010, O. Francke, D. Barrales, J. Cruz, A. Valdez Cols. 2 males (LATLAX-Ara 0158) from Cueva del Jardín Botánico, Parque Nacional Grutas de Cacahuamilpa (18.67038, -99.51134, 1145 m) Municipality Pilcaya, 15-IX-2017, A. Valdez, P. Solís, I. Navarro, J. Valerdi Cols. 2 males (LATLAX-Ara 0161) from Grutas del General Pacheco (18.66562, -99.50943, 1086 m) Municipality Pilcaya, 19-IX-2017, A.Valdez, P. Solís, I. Navarro, J. Valerdi Cols. 6 females (LATLAX-Ara 0162) from Cueva Agustín Lorenzo, Mexcaltepec (18.431,-99.55013, 922 m) Municipality Taxco de Alarcón, 20-IX-2017, A. Valdez, P. Solís, I. Navarro, J. Valerdi Cols. 3 males, 5 females (LATLAX-Ara 0526) from Jardín Botánico, Parque Nacional Grutas de Cacahuamilpa (18.67038, -99.51134, 1145 m) Municipality Pilcaya, 15-X-2019, A. Valdez, P. Solís, I. Navarro, A. Juaréz, A. Cabrera Cols. Morelos. 1 male (CNAN-Ar009069) from Lomas de Cortés, Municipality Cuernavaca, 11-II-2013, P. Bernard leg. 1 male (CNAN-Ar009070) from Tlaltenango (18.946414, -99.24392, 1660 m) Municipality Cuernavaca, III-2013. R. Rosas leg. 1 male (CNAN-Ar009071) from Boulevard Cuahutémoc #33, Lomas de Cortés (18.951125, -99.22408, 1640) Municipality Cuernavaca, 24-II-2012.
Diagnosis. Loxosceles misteca Gertsch, 1958 resembles L. tenochtitlan sp. nov. (Figs
29–31 Loxosceles misteca Gertsch. Male 29 left palp, retrolateral view, detail of tarsus, bulb and embolus 30 detail of bulb and embolus, retrolateral view 31 detail of the embolus 32–34 Loxosceles tenochtitlan sp. nov. Male paratype 32 right palp, retrolateral view, detail of tarsus, bulb and embolus 33 detail of bulb and embolus, retrolateral view 34 detail of the embolus. Arrows indicate the canal along the embolus.
Male holotype (examined) of Loxosceles misteca Gertsch, 1958 (AMNH_IZC 00327631), from Taxco, Municipality Taxco de Alarcón, Guerrero, Mexico; Date? 1946, collected in the fall, Leo Isaacs leg. 38, 39 habitus of male holotype, dorsal and ventral views, respectively 40 carapace 41 label of the holotype. Scale bars: 1 mm (38–40).
Male holotype (examined) of Loxosceles misteca Gertsch, 1958 (AMNH_IZC 00327631), from Taxco, Municipality Taxco de Alarcón, Guerrero, Mexico; 1946, collected in the fall, Leo Isaacs leg. 42–44 left palp, prolateral, dorsal and retrolateral views respectively 45–47 detail of the bulb and embolus, dorsal, retrolateral and apical views, respectively. Scale bars: 0.5 mm (42–44), 0.2 mm (45–47).
Loxosceles tenochtitlan sp. nov. Variation of the male palps, left palps, prolateral views 48 turiello Guerra, Street Cuitlahuac S/N, Tlalpan, Mexico City 49 Cruz Verde #132, Tlalpan, Mexico City (type locality) 50 Street Tepocatl #61, Pedregal de Santo Domingo, Coyoacán, Mexico City 51 Los Reyes Copilco, Frac. Areada Dpto. 102-A, Coyoacán, Mexico City 52, 53 Street Reforma #5, Santiago Tlacochcalco, Municipality of Tepeyanco, Tlaxcala 54, 55 Street Juárez Norte #214, Huamantla, Municipality Huamantla, Tlaxcala, Mexico. Scale bars: 0.5 mm.
Loxosceles tenochtitlan sp. nov. Variation of the seminal receptacles of the females, dorsal views 56 Street Cruz Verde #132, Tlalpan, Mexico City (type locality) (female paratype) 57 Los Reyes Copilco, Fracc. Areada Dpto. 102-A, Coyoacán, Mexico City 58 Street Juárez #23, San Mateo Ixtacalco, Municipality Cuautitlán Izcalli, Estado de Mexico 59 Street Reforma #5, Santiago Tlacochcalco, Municipality of Tepeyanco, Tlaxcala 60, 61 Street Juárez Norte #214, Huamantla, Municipality of Huamantla, Tlaxcala, Mexico.
Loxosceles misteca Gertsch, 1958 62–65 variation of the male palps, left palps, prolateral views 62 Grutas General Carlos Pacheco, Municipality Pilcaya, Guerrero 63 Cueva del Diablo Acuitlalpan, Municipality Taxco, Guerrero 64 boulevard Cuauhtémoc #99, Colonia Lomas de Cortes, Municipality Cuernavaca, Morelos 65 Grutas de Cacahuamilpa National Park, Municipality Pilcaya, Guerrero 66–69 variation of the seminal receptacles of the females, dorsal views 66, 67 Agustin Lorenzo Cave, Mexcaltepec, Municipality Taxco de Alarcón, Guerrero 68, 69 Botanical Garden Cave, Grutas de Cacahuamilpa National Park, Municipality Pilcaya, Guerrero.
The analyzed matrices include 52 individuals of 11 species of Loxosceles, 39 individuals for the CO1 data set and 34 individuals for ITS2 (Table
Genetic p-distance matrix from the CO1 data between Loxosceles tenochtitlan sp. nov. and Loxosceles misteca. Average p-distance = 13.8%.
Species | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
---|---|---|---|---|---|---|---|---|---|
1. Ara0082-L. misteca Gro | |||||||||
2. Ara0089-L. misteca Gro | 0.007 | ||||||||
3. Ara0090-L. misteca Gro | 0.010 | 0.003 | |||||||
4. Ara0084-L. misteca Gro | 0.017 | 0.020 | 0.024 | ||||||
5. Ara0236-L. misteca Gro | 0.009 | 0.012 | 0.014 | 0.019 | |||||
6. Ara0237-L. misteca Gro | 0.009 | 0.012 | 0.014 | 0.021 | 0.000 | ||||
7. Ara0146-L. tenochtitlan CDMX | 0.150 | 0.153 | 0.153 | 0.166 | 0.155 | 0.157 | |||
8. Ara0161-L. tenochtitlan CDMX | 0.133 | 0.131 | 0.131 | 0.150 | 0.134 | 0.137 | 0.014 | ||
9. Ara0173-L. tenochtitlan Tlax | 0.122 | 0.126 | 0.126 | 0.136 | 0.124 | 0.126 | 0.019 | 0.006 | |
10. Ara0164-L. tenochtitlan Tlax | 0.131 | 0.135 | 0.136 | 0.145 | 0.129 | 0.131 | 0.023 | 0.012 | 0.008 |
Genetic p-distance matrix from the ITS2 data between Loxosceles tenochtitlan sp. nov. and Loxosceles misteca. Average p-distance = 4.2%.
Species | 1 | 2 | 3 | 4 | 5 | 6 |
1. Ara0146-L. tenochtitlan CDMX | ||||||
2. Ara0173-L. tenochtitlan Tlax | 0.000 | |||||
3. Ara0164-L. tenochtitlan Tlax | 0.021 | 0.019 | ||||
4. Ara0082-L. misteca Gro | 0.036 | 0.037 | 0.062 | |||
5. Ara0084-L. misteca Gro | 0.030 | 0.031 | 0.059 | 0.005 | ||
6. Ara0090-L. misteca Gro | 0.026 | 0.026 | 0.066 | 0.020 | 0.014 | |
7. Ara0089-L. misteca Gro | 0.036 | 0.036 | 0.055 | 0.007 | 0.003 | 0.003 |
Maximum likelihood tree inferred from the concatenated matrix (CO1 + ITS2) of Loxosceles species from Mexico. Colors of branches and bars indicate different species. Numbers above bars at right represent the delimitation methods: 1: morphology (M). 2: neighbor-joining (NJ). 3: ABGD with initial partitions (IP). 4: ABGD with recursive partitions (RP). 5: GMYC. 6: bPTP with ML. 7: bPTP with IB. Numbers below bars represent species recovered for each delimitation method. Red numbers correspond to Bayesian posterior probabilities, and black numbers are bootstrap support values from the ML analysis.
The analysis of canonical variables CVA shows a significant difference (χ2 = 10.2555, df = 2, p = 0.00593003, λ = 0.5988) between both species, which indicates the formation of two groups according to the tibiae shape of the palps of the males (Fig.
Average of linear measurements of Loxosceles tenochtitlan sp. nov. and Loxosceles misteca. N = number of individuals. LL1 = Length of leg 1. Cl = Carapace length. Cw = Carapace width. Sl = Sternum length. Sw = Sternum width. ♂ = males. ♀ = females. Numbers in parentheses represent minimum and maximum measurements.
Species | N | LL1 | Cl | Cw | Sl | Sw |
---|---|---|---|---|---|---|
Loxosceles tenochtitlan sp. nov. | ♂ 16 | 18.10 | 3.00 | 2.70 | 1.80 | 1.50 |
(13.8–21.3) | (2.2–4.2) | (2.2–3.2) | (1.6–2.1) | (1.2–2.0) | ||
♀ 24 | 22.36 | 2.94 | 2.71 | 1.55 | 1.38 | |
(17.7–26.5) | (1.8–3.9) | (2.2–3.1) | (1.3–2.1) | (1.2–1.9) | ||
Loxosceles misteca | ♂ 11 | 23.75 | 3.05 | 2.73 | 1.59 | 1.42 |
(18–31.9) | (2.5–3.4) | (2.5–3.0) | (1.2–1.9) | (1.1–1.5) | ||
♀ 11 | 18.47 | 3.08 | 2.67 | 1.59 | 1.31 | |
(14.1–18.9) | (2.5–3.3) | (2.3–3.0) | (1.4–1.9) | (1.1–1.7) |
Geometric morphometry of the tibia shape on retrolateral view of the palps of males of L. tenochtitlan sp. nov. (N = 12) and L. misteca (N = 9) 74 CVA plot showing a significant difference (χ2 = 10.2555, df = 2, p = 0.00593003, λ = 0.5988) between both species in the tibiae shape 75 deformation grid, the vectors indicate the direction of change in the tibia with respect to the average shape of the 21 individuals analyzed of both species 76, 77 palps of the males of L. misteca and L. tenochtitlan sp. nov. respectively, retrolateral views (red arrows indicate the change in the shape of the tibiae of the species analyzed).
Sexual dimorphism of Loxosceles tenochtitlan sp. nov. (T test) 78 box plots showing the variation of leg length 1 between males and females (t = -1.3106, p = 0.1981, df = 37, α = 0.05) 79, 80 box plots showing variation of carapace length (79) and width (80) between males and females (length: t = 1.498, p = 0.142, df = 38, α = 0.05; width: t = 0.6955, p = 0.4912, df = 36, α = 0.05) 81 linear morphometric variation of leg I length between males and females of L. tenochtitlan and L. misteca (T test) (males: t = 3.6174, p = 0.00331, df = 13, α = 0.05; females: t = 0.274, p = 0.787, df = 17, α = 0.05).
To analyze the potential distribution of L. tenochtitlan sp. nov., ENM was performed for the new species, with a total of 34 records from Mexico City, Estado de Mexico and Tlaxcala (Figs
Percent contribution of the climatic variables for the distribution model for Loxosceles tenochtitlan sp. nov. using the Maxent algorithm.
Variables | Contribution (%) |
---|---|
Vegetation type (CON01) | 42 |
Mean Temperature of Wettest Quarter (BIO10) | 28.5 |
Max Temperature of Warmest Month (BIO05) | 7.2 |
Temperature Seasonality (BIO04) | 5.3 |
Following the biogeographic scheme for Mexico proposed by
Ecological niche modeling (ENM) under Maxent algorithm for Loxosceles tenochtitlan sp. nov. Colors represent different ranges of probabilities of presence (high probability: 0.75–1.0). Circles represent known records of the new species. Blue lines represent biogeographical provinces proposed by
The first record of Loxosceles from Mexico City was by
As was mentioned previously, recent taxonomic studies based on molecular analyses using mitochondrial markers have suggested that the known diversity within the genus Loxosceles could be greatly underestimated (
Although DNA barcodes are being applied in modern systematics as a useful tool to resolve species delimitation problems, modern taxonomy includes many different sources of evidence, such as traditional morphology, ecology, reproduction, and biogeography. Traditional morphology alone cannot determine species boundaries in some cases, and the genus Loxosceles is no exception. Identifying morphologically inseparable cryptic or sibling species requires a new set of taxonomic tools, including DNA and additional sources of evidence (integrative taxonomy) (
Although morphologically L. tenochtitlan sp. nov is quite similar to L. misteca in the seminal receptacles of the females and the male palps, there are some subtle morphological differences that allow diagnosis of the new species as was mentioned in the description section. Multiple lines of robust evidence are able to clearly separate it as a new species. These methods are genetic differences, geometric and linear morphometry and different biogeographical distribution patterns. Strictly, cryptic species are those that cannot be differentiated based on their morphology or external appearance and are reproductively isolated. The present genetic divergence indicates the two species are independent lineages (
The species separation based on corrected genetic distances indicates that CO1 performed better for species delimitation than ITS2 (Figs
Sexual characters in spiders are robust and important morphological characters that are still used to separate species and to provide a diagnosis. This means that genitalia evolve, on average, more rapidly than non-genital morphological traits (Huber, 2003;
ENM is a powerful approach to understand how abiotic factors (e.g., temperature, precipitation, and seasonality) impact the geographic limits of the species (
Despite the similarity between L. tenochtitlan sp. nov. and L. misteca, we consider them different species for three main reasons: (1) they can be distinguished by morphological characters (genitalic and somatic); and the new species can be diagnosed morphologically; (2) molecular data from multiple genes analyzed with multiple methods consistently separate them (congruence among methods); and (3) statistically significant geometric and linear morphometric variation in tibias shape of the palp of the male and leg I length of males respectively.
The first author thanks the program “Cátedras CONACyT”, Consejo Nacional de Ciencia y Tecnología (CONACyT), Mexico; for scientific support for the project No. 59: “Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales (LBCTV) del Institute of Biology, Universidad Nacional Autónoma de México (