Salvadora lineata

Salvadora lineata View in CoL

One of these species is a country endemic and the other is a non-endemic.

Only a single species is restricted to each of the following three physiographic regions in Chihuahua. These three regions and the species involved are as follows:

Llanuras y Médanos del Norte— Incilius alvarius

Sierras Plegadas del Norte— Eleutherodactylus marnockii

Sierras y Cañadas del Norte— Heloderma suspectum

Each of these three species is a non-endemic.

Finally, no species are limited to the GMCD region in Chihuahua.

To determine the herpetofaunal relationships among the nine physiographic regions we recognize, we constructed a Coefficient of Biogeographic Resemblance (CBR) matrix (Table 6). As noted above, the number of species per physiographic region ranges from 58 in the SLD to 128 in the GMCC. The number of shared species ranges from 14 between the SPN and GMCD regions to 72 between the SCN and GMCC regions. The range and mean of the shared species numbers for each of the nine regions, arranged according to the increasing mean number, are as follows (mean number in parentheses followed by range, then by total regional number in parentheses):

GMCD — (27.6) 14–59 (59)

SCN — (42.6) 29–72 (78)

SLD — (37.4) 22–42 (58)

BDM — (44.5) 20–62 (80)

SPN — (38.9) 14–58 (64)

LMN — (45.6) 23–62 (81)

SLT — (40.1) 27–53 (61)

GMCC — (46.1) 27–72 (128)

LSV — (41.6) 17–61 (75)

Notably, with one exception, as the total regional number increases, so does the mean number of shared species.

The CBR data in Table 6 demonstrate a range of values from 0.23 to 0.83. The lowest value is that between the SPN and the GMCD, while the highest value is that between the SPN and the LSV. The highest CBR value for each of the nine regions is as follows:

LMN (81) — 0.77 — BDM (80)

SLT (61) — 0.76 — SCN (78)

SPN (64) — 0.83 — LSV (75)

GMCC (128) — 0.70 —SCN (78)

BDM (80) — 0.81 — SPN (64)

SLD (58) — 0.66 — SLT (61)

LSV (75) — 0.83 — SPN (64)

GMCD (59) — 0.63 — GMCC (128)

SCN (78) — 0.76 — SLT (61)

For the nine regions, the strongest relationships involve only six of the other regions (SPN, BDM, LSV, SCN, SLT, and GMCC). The SPN, SCN, and SLT are involved in two of these relationships, whereas the other three (BDM, LSV, and GMCC) are involved only once.

Based on the data in Table 6, we constructed a UPGMA dendrogram to conveniently illustrate the overall herpetofaunal resemblances among the nine physiographic regions in Chihuahua in a hierarchial fashion (Fig. 13). The dendrogram indicates that the nine physiographic regions are divided into two principal groups separated at the 0.40 level, one containing the GMCC and GMCD regions and the other containing the remaining seven regions. The GMCC and GMCD regions are located adjacent to one another in southwestern Chihuahua ( Fig. 1), with the smaller GMCD region situated to the south of the GMCC region. The other seven regions are partitioned into two groups separated at the 0.53 level. One group comprises the SCN, SLT, and SLD regions, which are located in a swath lying to the east of the GMCC–GMCD pair that extends from the west-central portion of the state adjacent to the border of Sonora southeastward to the south-central portion adjacent to the border of Durango ( Fig. 1). The SCN and SLT regions are separated at the 0.76 level and lie

Fig. 13. UPGMA-generated dendrogram showing the similarity relationships of species richness among the herpetofaunal components of the nine physiographic provinces of Chihuahua (based on the data in Table 6; Sokal and Michener 1958). The similarity values were calculated using the Coefficient of Biogeographic Resemblance (CBR) of Duellman (1990).

adjacent to one another, with the SCN and SLT regions separated from the SLD region at the 0.63 level. Finally, the remaining four regions (LMN, SDM, LSV, and SPN) are joined to one another at the 0.76 level; these four regions are situated in a group occupying roughly the eastern half of the state ( Fig. 1) and are comprised of two swaths (LMN–BDM and SPN–LSV), the latter lying to the east of the former. The two most closely related regions (at the 0.83 level) are the SPN and LSV regions that lie adjacent to one another along the borders of Texas and Coahuila. These two regions are connected to the BDM region, which is adjacent to both these regions, at the 0.79 level. Finally, as noted above, these three regions are connected to the LMN region, located in the northwestern section of the state adjacent to the border of New Mexico, at the 0.76 level.

Distribution Status Categorizations

To categorize the distributional status of members of the Chihuahua herpetofauna, we used the system in Alvarado-Díaz et al. (2013) and the other MCS entries (see above). We indicate our assignment of the four distributional categories of non-endemic, country endemic, state endemic, and non-native species in Table 7 and summarize the data in Table 8.

The number and proportion of species in each of these four categories are as follows: non-endemic, 121 of 186 (65.1%); country endemics, 61 (32.8%); non-natives, three (1.6%); and state endemics, one (0.5%). Accordingly, the Chihuahua herpetofauna resembles the other faunas dealt with in the MCS that have more non-native species than in any other category, and in this case, all the other categories combined (121 vs. 65). The number of non-endemic species exceeds that of the country endemic species in Oaxaca ( Mata-Silva et al. 2015, 2021), Chiapas ( Johnson et al. 2015a), Nuevo León (Nevárez-de los Reyes et al. 2016), the Mexican Yucatan Peninsula ( González-Sánchez et al. 2017), Coahuila ( Lazcano et al. 2019), Veracruz (Torres-Hernández et al. 2021), Tabasco ( Barragán-Vázquez et al. 2022), and the Baja California Peninsula ( Peralta-García et al. 2023). In the other states dealt with thus far in the MCS, the number of country endemics is greater than that of the non-endemic species in Michoacán ( Alvarado-Díaz et al. 2013), Nayarit (Woolrich-Piña et al. 2016), Jalisco (Cruz Sáenz et al. 2017), Puebla (Woolrich-Piña et al. 2017), Hidalgo ( Ramírez-Bautista et al. 2020), Querétaro ( Cruz-Elizalde et al. 2022), and Guanajuato ( Leyte-Manrique et al. 2022).

As indicated above, in some entries of the MCS the number of country endemics is greater than the number of non-endemic species, whereas in others the reverse is the case. Thus, the ratios of country endemics to non-endemic species vary considerably, from 0.53 in Jalisco to 0.95 in Baja California. The ratios in which the number of non-endemics exceeds that of the country endemics range from 1.12 in Oaxaca to 127.0 in the Mexican Yucatan Peninsula. The figure for Chihuahua is 1.9 (121/65). As noted by Leyte-Manrique et al. (2022: 147), “the nature of this ratio depends on how close the state in question is to either the United States or Central America. This ratio also depends upon the size of these aspects of a given herpetofauna as to whether the ratio will be more or less than one.” In the case of Chihuahua, we would expect the ratio to be greater than one since this state shares a relatively long border with the USA. Leyte-Manrique et al. (2022) quoted Torres-Hernández et al. (2021), who stated: “In the case of the three MCS states that border the USA, the ratios are 3.22 (100/ 31 in Coahuila; Lazcano et al. 2019), 2.44 (95/ 39 in Nuevo León; Nevárez-de los Reyes et al. 2016), and 2.32 (130/ 56 in Tamaulipas; Terán-Juárez et al. 2016).” As noted above, the ratio for Chihuahua is 1.9 (121/65), which is most similar to the ratio for Tamaulipas (i.e., 119/49=2.4; Terán-Juárez et al. 2016).

Interestingly, only one state endemic species is known to occur in Chihuahua, i.e., Plestiodon multilineatus ( McCranie and Wilson 1987) . This skink inhabits pine forests at elevations from 2,246 to 2,615 m in the Sierra Madre Occidental (Tanner 1988).

The three non-native species recorded from Chihuahua (Table 7) are the anuran Lithobates catesbeianus , the gecko

No. 13. Scaphiopus couchii Baird, 1854 . The distribution of Couch’s Spadefoot “extends from southeastern California to southeastern Colorado and southwestern Oklahoma, in the United States, southward in Mexico to northern Nayarit, Zacatecas, San Luis Potosí, and northern Veracruz ” ( Lemos-Espinal and Dixon 2013: 75–76). This individual was photographed in scrub vegetation near the city of Chihuahua, Chihuahua. Wilson et al. (2013b) established its EVS as 3, placing it at the lower limit of the low vulnerability category. Its IUCN status has been calculated as Least Concern, and this species is not listed by SEMARNAT. Photo by Eric Centenero-Alcalá.

No. 15. Spea multiplicata (Cope, 1863) . The distribution of the Mexican Spadefoot “extends from southeastern Utah and southern Colorado through western Oklahoma, Arizona and New Mexico, in the United States, southward into Mexico to northern Sonora and throughout the Chihuahuan Desert to the Transvolcanic Belt; it also occurs in mountainous regions from the Sierra Madre Occidental of central Chihuahua southward to Oaxaca ” ( Lemos-Espinal and Dixon 2013: 76–77). This individual was photographed in a sand dune environment (médanos) near Rancho El Lobo, in the city of Juárez, Chihuahua.Wilson et al. (2013b) determined its EVS as 6, placing it in the middle of the low vulnerability category.The IUCN has established its conservation status as Least Concern, and this species is not listed by SEMARNAT. Photo by Eric Centenero-Alcalá .

No. 14. Spea bombifrons (Cope, 1863) . The Plains Spadefoot is distributed from “southern Alberta and southwestern Saskatchewan (Canda) southward through Montana, North Dakota, … Nebraska and eastern Colorado to southeastern Utah, northeastern and southeastern Arizona , central Missouri, Oklahoma and western and South Texas ( USA) to Chihuahua and Tamaulipas ( Mexico)” ( Frost 2023). This individual was photographed in sand dune vegetation containing an aromatic shrub ( Poliomintha incana ) and Sand Sagebrush ( Artemisa filifolia ) at Rancho Zorro Plateado in the city of Juárez, Chihuahua. Wilson et al. (2013b) calculated its EVS as 10, placing it at the lower limit of the medium vulnerability category. The IUCN rated this species as Least Concern, and this species is not listed by SEMARNAT. Photo by Jesús M. Martínez-Calderas.

No. 16. Ambystoma rosaceum Taylor, 1941 . The Tarahumara Salamander occurs at “high elevations in the Sierra Madre Occidental from the region of Aguascalientes and western Zacatecas north through montane Nayarit, Durango and montane Sinaloa to northern Chihuahua (vicinity of Casas Grandes) and northern Sonora (Sierra Pinitos, Sierra de los Ajos, Sierra El Tigre, and Sierra San Luis in the north), Mexico ” ( Frost 2023). This larval individual was photographed in pine forest vegetation at Monterde, in the municipality of Guazapares, Chihuahua. Wilson et al. (2013b) ascertained its EVS as 14, placing it at the lower limit of the high vulnerability category. The IUCN conservation status of this salamander has been assessed at Least Concern, and this species was placed in the Special Protection category by SEMARNAT. Photo by Eric Centenero-Alcalá.

Hemidactylus turcicus , and the blindsnake Indotyphlops braminus . The blindsnake I. braminus is one of the most widespread non-native species in Mexico, as it has been recorded in all 16 previous MCS entries. González-Sánchez et al. (2021) also indicated this snake is one of the most widespread of the introduced herpetofaunal taxa in Mesoamerica ( Mexico and Central America), as it has been recorded in six of the eight countries in this region, and this blindsnake also occurs in northwestern Costa Rica (Wallach 2020a; Solórzano 2022).

Wilson et al. (2017) developed a system for categorizing the distribution of the non-endemic species of the Mesoamerican herpetofauna, including those of Mexico. As expected, the categorization of the non-endemic species in Chihuahua (Table 9) demonstrates that most of them (108 of 121 or 89.3%) are placed in the MXUS category. This situation was expected given that Chihuahua is one of the six Mexican states along the Mexico –USA border, as well as the one with the longest border. The next most common categorization is USCA (six, or 5.0%), which also was expected since Chihuahua lies at the opposite end of the country of Mexico from any of the countries in Central America. The MXSA and MXCA species each amount to three (2.5%). Finally, a single USSA species is represented (0.8%). Thus, all but six of the non-endemic species have distributional ranges that extend northward into the USA, and in a few cases all the way to South America .

Herpetofaunal Comparisons in Adjacent Mexican States

As indicated above, the northern border of Chihuahua is part of the border between Mexico and the USA. The rest of Chihuahua’s border is contiguous with parts of the Mexican states of Sonora , Sinaloa, Durango, and Coahuila. The herpetofauna of Coahuila was examined in the Mexican Conservation Series ( Lazcano et al. 2019), and the herpetofauna of Durango, Sinaloa, and Sonora were dealt with by Lemos-Espinal et al. (2018a, 2019b, 2020).

In Table 10 we compare the herpetofauna of Chihuahua to those of the five bordering Mexican states, which indicates the total number of herpetofaunal species, the number of endemic species (both state and country, as applicable), the number of non-native species, and the percentage of endemism (calculated as the number of endemic species [state and country endemics] divided by the number of native species times 100).

The size of the herpetofauna in each of these five states ranges from 143 in Coahuila to 200 in Sonora (Table 10). The number of non-endemic species ranges from 73 in Sinaloa to 125 in Sonora . The number of endemic species ranges from 40 in Coahuila to 82 in Sinaloa. In most of these five states the number of non-endemic species is higher than the number of endemic species, except for Sinaloa. The ratios of endemic species to non-endemic species for the five states are as follows: Sonora (68/125 = 0.54); Chihuahua (62/121 = 0.51); Coahuila (40/100 = 0.40); Durango (72/81 = 0.89); and Sinaloa (82/73 = 1.12). Evidently, the lower ratios are those for Coahuila, Chihuahua, and Sonora , all states that share a border with the USA; the higher ratios are those for Durango and Sinaloa, states that do not border the USA. The percentage of endemism in the five states ranges from 28.6 in Coahuila to 52.9 in Sinaloa, with a mean value of 39.4. Finally, the number of non-native species ranges from three to seven. Three of the five states harbor three non-native species (Chihuahua,

No. 17. Barisia ciliaris (Smith, 1942) . The distribution of the Sierra Alligator Lizard “extends along the Sierra Madre Oriental, from Nuevo León and southeastern Coahuila southward to at least Guanajuato, and northward along the Sierra Madre Occidental to extreme southern Chihuahua ” ( Lemos-Espinal and Dixon 2013: 96–97). This individual was photographed in pine-oak forest at 25 km E of Guachochi on highway 23, in the municipality of Balleza , Chihuahua. Wilson et al. (2013a) determined its EVS as 15, placing it in the lower portion of the high vulnerability category. The IUCN has not evaluated its conservation status, and this species is not listed by SEMARNAT. Photo by Antonio Esaú Valdenegro Brito .

No. 19. Elgaria kingii Gray, 1838 . The Madrean Alligator Lizard “lives in and adjacent to mountains of eastern Arizona , southwestern New Mexico, and in the Sierra Madre in eastern Sonora and western Chihuahua … to Jalisco ” ( Lemos-Espinal and Smith 2007). This individual was photographed in pine forest at Divisadero , in the municipality of Urique , Chihuahua. Wilson et al. (2013a) determined the EVS of this anguid as 10, placing it at the lower limit of the medium vulnerability category. The IUCN has judged its conservation status as Least Concern, and it was placed in the Special Protection category by SEMARNAT. Photo by Eric Centenero-Alcalá.

No. 18. Barisia levicollis Stejneger, 1890 . The Chihuahuan Alligator Lizard is distributed in Chihuahua ( Lemos-Espinal and Smith 2007), and it also might occur in eastern Sonora (Rorabaugh and Lemos-Espinal 2016) . This individual was photographed in a remnant patch of pine forest at La Mesa de Cristo Rey, in the municipality of Guerrero, Chihuahua. Wilson et al. (2013a) calculated its EVS as 15, placing it in the lower portion of the high vulnerability category. The IUCN has evaluated its conservation status as Data Deficient, and it was noted as a species of Special Protection by SEMARNAT. Photo by José Eduardo Gámez López.

No. 20. Gerrhonotus infernalis Baird, 1859 . The Texas Alligator Lizard occurs from “central Texas west to the Big Bend area, and west of the Sierra Madre Oriental to southern San Luis Potosí and perhaps extreme southeastern Durango. Its distribution in Mexico is limited to the Chihuahuan Desert and Sierra Madre Oriental biotic provinces…” ( Lemos-Espinal et al. 2018). This adult individual was photographed in pine-oak forest at Sierra Rica , in the municipality of Manuel Benavides, Chihuahua. Wilson et al. (2013a) assessed its EVS as 13, placing it at the upper limit of the medium vulnerability category. The IUCN evaluated its conservation status as Least Concern, and this species is not listed by SEMARNAT. Photo by José Candelario Hernández Álvarez.

Coahuila, and Durango), one supports four species (Sinaloa), and one contains seven species ( Sonora ). The total number of non-native species in these five states is nine, whichincludestwoanurans (Lithobatescatesbeianus in Chihuahua, Coahuila, Durango, Sinaloa, and Sonora , and L. berlandieri in Sonora ), four lizards ( Gehyra mutilata in Sinaloa, Hemidactylus frenatus in Sinaloa and Sonora , H. turcicus in Chihuahua, Coahuila, Durango, and Sonora , and Sauromalus hispidus in Sonora ), one snake ( Indotyphlops braminus in Chihuahua, Durango, Sinaloa, and Sonora ), and two turtles ( Trachemys scripta in Coahuila and Apalone spinifera in Sonora ). The most widespread of these nine non-native species are Lithobates catesbeianus (five states), and Hemidactylus turcicus and Indotyphlops braminus (four states each).