Systematic Studies of the Costa Rican Moss Salamanders, Genus Nototriton, with Descriptions of Three New Species
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Herpetological iMonographs, I, 1993, 131-159 0 1993 In The Herpetologists' League, IIK SYSTEMATIC STUDIES OF THE COSTA RICAN MOSS SALAMANDERS, GENUS NOTOTRITON, WITH DESCRIPTIONS OF THREE NEW SPECIES DAVIDA. GOOD' AND DAVIDB. WAKE Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, Berkeley, CA 94720, USA ABSTRKT: Study of allozyme variation, external morphology, and osteology reveals that there are more species of moss salamanders (genus Nototriton) in Costa Rica than the two currently recognized. The three species for which names are available are valid, and new diagnoses are presented for them; three additional species are described. The phylogenetic relationships and biogeography of the six species are investigated. The radiation of Nototriton in present-day Costa Rica has involved miniaturization accompanied by both morphological and ecological specialization. Costa Hican species inhabit moss-mats and leaf-litter; most of the remaining species in the genus are bromeliad-dwellers. The revised genus Nototriton includes two Mexican, one Guatemalan (another, detected in the present study, remains undescribed), two Honduran, and six Costa Rican species. The six Costa Rican species appear to form a monophyletic group, but the phylogenetic relationships of the two northern species groups to each other and to the southern group remain nncertain. Key words: Salamanders; Plethodontidae; Nototriton; Czosta Kica; Allozymes; blorphometrics; Systematics; New species SALAMANDEKSof the genus Nototriton Rica), they can be found easily, but char- (commonly known as moss salamanders) acteristically they are uncommon. Even are inconspicuous components of cloud species that have been known taxonomi- forest faunas from Oaxaca, Mexico, to cen- cally for more than 40 years (e.g., N. ri- tral Costa Rica. Most of the species occur churdi) are represented by fewer than 25 in moss mats hanging in trees or bushes, specimens in the museums of the world. or in moss covering dirt banks, large boul- Typically, species of Nototriton are small; ders, or stumps. Others inhabit bromeliads. none exceeds 40 mm in snout-vent length In a few places (such as on the northeastern and several species are not known to ex- slopes of the Cordillera Central in Costa ceed 30 mm. These salamanders have slen- der bodies, narrow heads, and long, ta- ' PHESENTADDRESS: Museum of Natural Science, pering tails that exceed their snout-vent 119 Foster Hall, Louisiana State University, Baton length. Their eyes are small arid oriented Rouge, LA 70803. USA. anteriorly, and several of the species have 132 HERPETOI~O<~ICALMONOGRAPHS [No. 7 enlarged nostrils. Their limbs are slender may be confused are ‘Oedipus’ picadoi and short, and the feet in some species arc Stejneger and Parvimolge richardi, both greatly reduced and have become syndac- of which occur in Costa Kica. The first tylous. Although the species are colorful species may be differentiated easily by the when living specimens are viewed under enlarged nostril of the young arid adults; a dissecting microscope, they arc so small and Parvimolge by the structure of hands that their color patterns are obscure. Spe- and feet, especially the enlarged elongate cies of Nototriton are taxonomically dif- middle digit” (Taylor, 1948:179). I,ater, ficult because there is so little perceptible Taylor (1952) placed picadoi in the genus external variation in the genus. The genus Chiropterotriton, and erroneously stated itself is of uncertain status, mainly because that this taxonomic assignment had bcen diagnostic characters are subject to ho- made by Taylor (1949); he considered ab- moplasy, a phenomenon that has plagued scondens and picadoi to be close relatives, phylogenetic analyses of tropical salaman- distinguished chiefly by nostril size (large ders. Because of these problems, the genus in picadoi, small in abscondens). Taylor and its members have had a confused tax- (1952) published detailed dra\vings of the onomic history; this history is reviewed be- only known specimen of the enigmatic tax- low in order to provide appropriate hack- on richardi, a form that he compared only ground for the taxonomic changes we to Parviniolge townsendi of Mexico. The propose. holotype of richardi was collected under the bark of a stump in local sympatry with HISTORICALHACKGROLJNU abscondens, but Taylor (1954) reported Stejneger (1911) described Spelerpes pi- finding abscondens to be abundant in moss cadoi from the “valley of the Orosi” in the mats. This was the first report of a species northern part of the Cordillera de Tala- of neotropical salamander that appeared manca in eastern Costa Rica. His descrip- to specialize on moss. tion was based on a single small salaman- Wake and Lynch (1976) concluded that der collected in a bromeliad at La Estrella picadoi and abscondens were conspecific, by the famous Costa Rican biologist Clau- and assigned them to an informal “beta domiro Picado (Picado, 1913). Dunn (1926) group” of the genus Chiroptcrotriton. discussed the anatomy of some specimens They were uncertain of the generic status from Ida Palma, Costa Rica, which he as- of richardi, which they tentatively listed signed to Oedipus picadoi, and asserted as Parvimolge. In retrospect, the reasons that some of the type material of the spe- for combining abscondens and picadoi art’ cies now known as Bolitoglossa subpal- evident, for we now believe that until re- mata (type locality La Palma) also was cently only one specimen of picadoi, the assignable to 0. picadoi. In a generic rc- holotype, had ever made its way into any vision of the tropical salamanders, Taylor of the major herpetological collections (iri- (1944), at that time unfamiliar with Costa cluding that of the University of Costa Rican species, simply listed Stejneger’s tax- Rica). Taylor (1952) accepted Dunn’s on as “Pseudoeurycea? picadoi”. Taylor (1926) assignment of La Palma specimens (1949) continued to refer to the species in to picadoi, but specimens from this locality that manner, but by thcn he had begun in the Cordillera Central cannot be sepa- his field work in Costa Rica and had dis- rated morphologically from abscondens. It covered some diminutive salamanders in was this fact that led Wake and Lynch to the volcanic Cordillera Central which he recognize only one taxon. We interpret described as Chiropterotriton abscondens Taylor’s (1948) statement concerning the (Taylor, 1948) and Parvimolge richardi large nostril size in young picadoi to be (Taylor, 1949) (both of these genera had based on his examination of specimens been deseri1)etl by Taylor, 1044). Of C. from I,a Palma, for to our knowledge no a?xcondens, Taylor stated: “two other di- juveniles of “true” picadoi were collected minutive species with which this species until recently, when we discovered a pop- 19931 HERPETOLOGICAL MONOGRAPHS 133 ulation assignable to picadoi in the Tala- pina; that is, Nototriton might be para- mancan region near the type locality. This phyletic. Until recently, N. richardi has discovery enabled us to determine that pi- been too rare to examine this proposition cadoi is specifically distinct from the pop- seriously. The nasalis group is well sup- ulations in the Cordillera Central that pre- ported by osteological synapomorphies viously had been assigned to this taxon (see (Lynch and Wake, 1978; Papenfuss and below). Wake, 1987), but this has not been true of Revisionary studies of Guatemalan and the Costa Rican species. The recently de- Mexican species of the beta group of Chi- scribed species N. adelos from Oaxaca, ropterotriton revealed that three appar- Mexico, placed in its own species group ently monophyletic assemblages existed (Papenfuss and Wake, 1987), remains too (Lynch and Wake, 1975,1978; Wake and poorly known to be considered further. Elias, 1983). All species north of the Isth- This paper represents the results of field mus of Tehuantepec remained in Chirop- and laboratory research conducted over a terotriton, and two new genera were de- period of several years to clarify system- scribed (Dendrotriton and Nototriton); atic, biogeographic, and local ecological picadoi (sensu lato) and richardi were problems involving Costa Rican salaman- placed in Nototriton (the latter with res- ders (e.g., Wake, 1987). In this revision of ervation) (Wake and Elias, 1983). In ad- Costa Rican Nototriton, we first outline dition, the poorly known Talamancan spe- the criteria we have used in recognizing cies Bolitoglossa diminuta (Robinson, taxa. We then describe new species and 1976) was tentatively included in Noto- present redescriptions of previously rec- triton (Wakeand Elias, 1983);subsequent- ognized taxa. A discussion of evidence for ly the species was returned to Bolitoglossa our taxonomic decisions then follows. This (Bolaiios et al., 1987; Papenfuss and Wake, order of presentation is chosen so that 1987; Wake, 1987). names are available for clarity in the dis- The unsettled taxonomy of the Costa cussion of morphological and biochemical Rican Nototriton is related to the super- data. ficial morphological similarity of these tiny salamanders, as well as their relative rarity. CRITERIAFOR SPECIESRECOGNITION Information concerning habitat, distribu- Our general goal is to discern geneti- tion, behavior, and morphology has ac- cally cohesive units that are evolutionarily cumulated slowly (e.g., Wake, 1987). The independent entities, and to recognize same difficulties have been encountered in them taxonomically as species. Two ex- Mexico, where Hanken