Herpetology Notes, volume 14: 99-102 (2021) (published online on 09 January 2021)

First record of Sibon dimidiatus (Günther, 1872) for the department of La Paz, south-western Honduras

Mario Roberto Espinal1, José Mario Solís2,3,4, and José Manuel Mora5,6,*

Dipsadide Gray, 1825 is the largest colubrid family of eastern and southwestern Guatemala, southern Belize, snakes in the New World, with over 800 species (Vidal northern Honduras, and eastern Nicaragua to Costa et al., 2010; Uetz et al. 2020). The genus Sibon Fitzinger, Rica, and south across the Petén (Chaves et al., 1826 currently comprises 18 recognised species in three 2013). It occupies evergreen forests in the lowlands groups. The species of Sibon range from lowland to and premontane slopes up to 1,950 m (Savage, 2002; premontane areas, from northern Veracruz, Mexico, Leenders, 2019). south through Central America to (east of the Andes) In Honduras Sibon dimidiatus only is known from northern Brazil, Colombia, Peru, Venezuela, Guyana, 13 specimens collected in the departments of Gracias a and Ecuador west of the Andes (McCranie, 2011; Vera- Dios (1), Olancho (5), Yoro (2), Cortés (2), Copán (2), Pérez, 2019). and Francisco Morazán (1), with all the records coming Günther (1872) described Leptognathus dimidiatus at elevations from 360 to 1,600 m, in forest formations from “México” as the type locality. Peters and Orejas- including Lowland Moist Forest, Premontane Wet Miranda (1970) listed this species as Sibon dimidiate. Forest, and Lower Montane Wet Forest (McCranie, Subsequently, Liner (1994) included the species, with 2011). Herein we report the fourteenth and fifteenth the current name of Sibon dimidiatus, within the Sibon record of Sibon dimidiatus for Honduras — including annulatus group (Vera-Pérez, 2019; Uetz, et al., 2020). the first record for the department of La Paz — both Sibon dimidiatus is a moderately small, banded or collected in the Municipality of Marcala. ringed snake, with a long tail that is associated with its The first individual, an adult female (Fig. 1), was arboreal habits. Notwithstanding its arboreal habits, this collected on 23 May 2019 at 10:01 h. The snake was snake species specialises on eating molluscs (McCranie, found in a coffee plantation adjacent to a forest fragment 2011; Harrington et al., 2018). Sibon dimidiatus is an at the Pueblo Viejo farm (14°08’52’’N, 88°03’01’’W; uncommon species found mainly in pristine forests 1,454 m elevation; Fig. 2). The second individual, (Leenders, 2019) of central Veracruz, Mexico, through another adult female, was collected on 12 August 2019

1 Centro Zamorano de Biodiversidad (CZB), Escuela Agrícola Panamericana Zamorano, Depto. de Francisco Morazán, Honduras. 2 Escuela de Biología, Facultad de Ciencias, Universidad Nacional Autónoma de Honduras, Depto. de Francisco Morazán, Tegucigalpa, Honduras. 3 Grupo de Investigación de Reptiles y Anfibios de Honduras (GIRAH). 4 Red Mesoamericana y del Caribe para la Conservación de Anfibios y Reptiles (MesoHERP). 5 Carrera de Gestión Ecoturística, Sede Central, Universidad Técnica Nacional, Alajuela, Costa Rica. 6 Department of Biology and Museum of Vertebrate Biology, Portland State University, Portland, Oregon 97207, USA Figure 1. An adult female individual of Sibon dimidiatus * Corresponding author. E-mail: [email protected] recorded in Marcala Municipality, La Paz Department, © 2020 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. Honduras. Photo by Jose Mario Solís. 100 Mario Roberto Espinal et al.

Figure 2. Two new locality records for Sibon dimidiatus in south-western Honduras (red triangle) at La Paz department. Red circles represent previously known localities of occurrence for the species in Honduras.

at 09:04 h at the Buenos Aires farm (14°08’30’’N; documented in Honduras: all but one are from wet 88°02’49’’W; 1,570 m elevation). Both specimens were forests (Subtropical and Lower Montane) or its edges preserved in 95% alcohol and deposited in the collection (three records are from the ecotone between Subtropical of the Museo de Historia Natural, Universidad Nacional Autónoma de Honduras en el Valle de Sula (MUVS- V). Catalogue numbers are MUVS-V-02141 (first Table 1. Measurements and pholidosis of two individuals individual), and MUVS-V-02142 (second individual). of Sibon dimidiatus from department of La Paz, Honduras. Measurements of both individuals were taken using Measurements follow McCranie (2011): SVL= snout–vent 1 Table 1. Measurements and pholidosis of two individuals of Sibon dimidiatus from an electronic digital calliper Tactix 24111 (resolution length; T= tail length; TL= total length; VS= ventral and 2 subcaudaldepartment scales; of DSR= La Paz, dorsal Honduras. scale rows; Measurements S= supralabial follow McCranie (2011): SVL= snout– 0.01 mm, precision 0.02 mm). To confirm species 3 scales;vent I= length;infralabial T= scales; tail P= length; postocular TL= scales. total length; VS= ventral and subcaudal scales; DSR= identification, we took scale counts following McCranie 4 dorsal scale rows; S= supralabial scales; I= infralabial scales; P= postocular scales. (2011; Table 1). 5 Previous records of Sibon dimidiatus in Honduras Specimen number have been restricted to the northern and south-central MUVS-V-02141 MUVS-V-02142 portion of the country (McCranie, 2011). This record SVL 490 mm 470 mm extends the distribution of the species by 106.4 km T 290 mm 210 mm NWW (airline distance) from the previously known TL 780 mm 680 mm nearest locality, in La Montañita village, department of VS 184 184 Francisco Morazán (Fig. 2). This break in distribution SS 99 (without the 99 (without the likely separates not only the new records from those tip of the tail) tip of the tail) of La Montañita, but probably also represents a break DSR 15, 15, 15 15, 15, 15 between two populations, because individuals of Sibon SL (right-left) 5-5 5-5 dimidiatus are isolated within patches of specific I (right-left) 7-7 7-7 ecosystem types. P 1 1 Thirteen previous records of this species are 6 7

1

First record of Sibon dimidiatus for the department of La Paz, Honduras 101

Wet Forest and Subtropical Moist Forest). The record in the observation that the range of Sibon dimitiatus from Francisco Morazán and the two new records varies from near sea level to 1,950 m (Leenders, 2019). from La Paz are from the Lower Montane Moist Forest However, as noted by Brown et al. (1996) “features (LMMF). This life zone occurs in isolated patches of ranges are all related to the environmental factors across suitable habitats of southern Honduras (Fig. 2). and ecological processes that limit distribution and The LMMF is a broad leaf forest spanning from 700 abundance”. In particular, Brown and Maurer (1989) – 1,500 m elevation, with 1,850-4,000 mm of rain per made the observation that small ranges of vertebrates year, and a dry season of 1-2 months (Holdridge, 1967). tend to be oriented north-south, whereas large ones This is the typical cloud forest, with fog present for long instead are oriented east-west, along thermally stable periods of the day, and a high amount of humidity and latitudinal bands; Brown (1995) specifically applied moisture (Holdridge, 1967). These characteristics favour this to North American snakes. Sibon dimititatus the presence of Sibon dimidiatus due to its preference presents an interesting conundrum in that the major for humid environments associated with cloud forest axis of its geographic range is neither E–W nor N–S but habitats (Leenders, 2019). Specimens of this species instead is constrained by geography to an intermediate collected in Honduras and Costa Rica have come from orientation caused by the narrowing and orientation gallery forests or were captured on very rainy nights of the Mesoamerican land mass (Chaves et al., 2013). (Savage, 2002; Solorzano, 2004; McCranie, 2011). Based on the data of Chaves et al. (2013), the principal Sibon dimidiatus has a patchy distribution in Central area of distribution of S. dimitiatus is ca. 1,200 km America, and populations inhabiting mountainous areas E to W, and 725 N–S. This would make the species sometimes are separated from one another by hundreds one of the most extreme cases among snakes insofar of km, without opportunity for exchange of genetic as the shape of the geographic range, as per the data material (Leenders, 2019). Populations genetically of Brown (1995:109). However, the long axis of the isolated in isolated cloud forests could in fact represent principal distribution of S. dimitiatus is over 1400 km otherwise morphologically cryptic species concealed and presents notable narrowing toward the north, where within a species complex (Leenders, 2019). There the species’ distribution coincides with the coastal plain only are three small patches of cloud forests (LMMF of Veracruz, Mexico. In contrast, as the range of S. life zone) in La Paz within southwestern Honduras. dimitiatus extends southward, it also appears to expand Cloud forest amphibians and reptiles are one of most in breadth, an apparent intraspecific contradiction of important herpetofaunal groups in Honduras (Wilson Rapoport’s Rule (Stevens, 1989), which states that and McCraine, 2003). However, these species are ranges of biota generally are smaller at lower rather seriously endangered as a result of human activities than higher latitudes. Furthermore, the species migrates that exponentially increase habitat destruction (Wilson up vertically as latitude decreases. We hypothesise that and McCraine, 2003). Over half of these species have there may be a complex interaction between temperature populations that are in decline or have disappeared from and humidity that dictates range parameters in S. Honduran cloud forests (Wilson and McCraine, 2003). dimitiatus, a phenomenon recently documented at the All known cloud forest populations of Sibon dimidiatus interspecific level in ferns of Nuclear Central America are declining and the species is present only in one out by Hernández–Rojas et al. (2019). This phenomenon of eight ecophysiographic areas in Honduras (Wilson also was documented in a mammal species in lower and McCraine, 2003). Populations of Sibon dimidiatus Mesoamerica with range parameters similar to those of from cloud forests in southern Honduras are threatened S. dimitiatus (Mora et al., 2020), which resulted in an and should be protected as potentially unique genetic altitudinal range retraction as latitude decreased. Given units. the high elevation of the new southernmost records Throughout southwestern Honduras, Sibon dimidiatus reported herein, we hypothesise that the maximum is found in areas of LMMF, although the species’ elevation range of the species increases with decreasing range occupies a much-diminished area. Based on the latitude, as temperature–determined ecosystem bands foregoing, we conclude that Sibon dimidiatus displays rise in elevation. This suggests, taking into account a tendency to inhabit lower montane, moist, or wet the present climate change scenario, the development forests. Notwithstanding the foregoing, previous records of research on this species to evaluate the relationship of the species have varied in elevation. Inspection of the between elevation and latitude in Lower Montane Moist elevations absent geographic data would merely result Forest ecosystems. 102 Mario Roberto Espinal et al.

Acknowledgments. We thank L. D. Wilson for confirming the Liner, E.A. (1994): Scientific and common names for the identification of the snake, and for his pre-submission review of amphibians and reptiles of Mexico in English and Spanish. the note. We also thank Adolfo Josué Pérez and Ernesto Adolfo Nombres científicos y comunes en inglés y español de los Pérez for allowing us to work in their coffee farm at Marcala, La anfibios y los reptiles de México. Society for the Study of Paz, and for their hospitality and kindness. Jorge Funes kindly Amphibians and Reptiles Herpetological Circular 23: 1–113. prepared the map in Figure 2. We appreciate all corrections and McCranie, J.R. (2011): The Snakes of Honduras. Systematics, suggestions made by Javier Ernesto Cortés Suárez, Louis W. distribution, and conservation. Ithaca, N.Y., USA, The Society Porras, and specially L. A. Ruedas. JMM acknowledges Emilce for the Study of Amphibians and Reptiles. Rivera, department head, Carrera de Gestión Ecoturística, Mora, J.M., Silva, S.M. López, L.I., Burnham-Curtis, M.K., Universidad Técnica Nacional, for provide time to work on this Wostenberg, D.J., French, J.H., Ruedas, L.A. (2020): paper. Systematics, distribution, and conservation status of Dice’s cottontail, Sylvbilagus dicei Harris, 1932 (Mammalia, References Lagomorpha, Leporidae), in Central America. Systematics and Biodiversity, doi: 10.1080/14772000.2020.1827. Brown, J.H. (1995): Macroecology. Chicago, Illinois, University Peters, J.A., Orejas-Miranda, B. (1970): Catalogue of the of Chicago Press. Neotropical Squamata: Part 1 Snakes. Bulletin of the United Brown, J.H., Maurer, B.A. (1989): Macroecology: the division States National Museum 297: 1–134. of food and space among species on continents. Science 243: Savage, J.M. (2002): The Amphibians and Reptiles of Costa Rica. 1145–1150. A herpetofauna between two continents, between two seas. Brown, J.H., Stevens, G.C., Kaufman, D.W. (1996): The geographic Chicago, Illinois, USA, The University of Chicago Press. range: size, shape, boundaries, and internal structure. Annual Solórzano, A. (2004): Serpientes de Costa Rica. Heredia, Costa Review of Ecology and Systematics 27: 597–623. Rica, InBio. Chaves, G., Flores-Villela, O., Köhler, G., Porras, L.W. (2013): Stevens, G.C. (1989): The latitudinal gradients in geographical Sibon dimidiatus. The IUCN Red List of Threatened range: how so many species co-exist in the tropics. American Species 2013: e.T63917A3131032. Available at: https://dx.doi. Naturalist 133: 240–256. org/10.2305/IUCN.UK.2013-2.RLTS.T63917A3131032. Uetz, P., Freed, P., Hošek, J. (2020): Sibon dimidiatus (Günther, en. Accessed on 12 October 2020. 1872). The Reptile Database. Available at: http://www.reptile- Günther, A. (1872): Seventh account of new species of snakes in database.org. Accessed on 31 May 2020. the collection of the British Museum. The Annals and Magazine Vera-Pérez, L.E. (2019): A new species of Sibon Fitzinger, 1826 of Natural History 9: 13–37. (Squamata: Colubridae) from southwestern Colombia. Zootaxa Harrington, S.M., De Haan, J.M., Shapiro, L., Ruane, S. (2018): 4701: 443–453. Habits and characteristics of arboreal snakes worldwide: Vidal, N., Dewynter, M., Gower, D.J. (2010): Dissecting the arboreality constrains body size but does not affect lineage major American snake radiation: A molecular phylogeny of diversification. Biological Journal of the Linnean Society 20: the Dipsadidae Bonaparte (Serpentes, Caenophidia). C. R. 1–11. Biologies 333: 48–55. Hernández-Rojas, A.C., Kluge, J., Krömer, T., Carvajal-Hernández, Wilson, L.D., McCranie, J.R. (2002): The herpetofauna of the C., Silva-Mijangos, L., Miehe, G., et al. (2019): Latitudinal cloud forests of Honduras. Amphibian and Reptile Conservation patterns of species richness and range size of ferns along 3: 34–48. elevational gradients at the transition from tropics to subtropics. Journal of Biogeography 47: 1383–1397. Holdridge, L.R. (1967): Life Zone Ecology. San José, Costa Rica, Tropical Science Center. Leenders, T. (2019): Reptiles of Costa Rica: a field guide. Ithaca, New York, USA, Zona Tropical Publications.

Accepted by Javier Cortés Suárez