Incilius nebulifer ( Girard, 1854 )

Mendelson Iii, Joseph R., Kinsey, Se. T. & Murphy, Es. B., 2015, A review of the biology and literature of the Gulf Coast Toad (Incilius nebulifer), native to Mexico and the United States, Zootaxa 3974 (4), pp. 517-537 : 517-525

Incilius nebulifer ( Girard, 1854)

Gulf Coast Toad

Bufo granulosus Baird & Girard, 1852:173 . [Not of Spix, 1824]. Type-locality “between Indianola and San Antonio, Texas” [restricted to “Indianola, Calhoun County, Texas” by Schmidt, 1953:66.]. Holotype (fide Kellogg, 1932), United States National Museum (USNM) 2595, age and sex unknown, collected by J. H. Clark in 1851, under the direction of survey leader J. D. Graham (not examined by authors) Fouquette & Dubois (2014) rejected the restriction of the type locality, claiming lack of published evidence.

Bufo nebulifer Girard,1854:86 , preoccupied by Bufo granulosus Spix, 1824

Bufo nebulifera Baird, 1859a:44 .

Chilophryne nebulifera Cope,1862:358 .

Incilius nebulifer Cope, 1863:50 .

Bufo valliceps Peters, 1863:81 .

Bufo nebulifer Mendelson & Mulcahy, 2000:182

Cranopsis nebulifer Frost, Grant, Faivovich, Bain, Haas, Haddad , de Sá, Channing, Wilkinson, Donnellan, Raxworthy, Campbell, Blotto, Moler, Drewes, Lynch, Green & Wheeler, 2006:364.

Ollotis nebulifer Frost, Grant & Mendelson, 2006:558 .

Incilius nebulifer Frost, Mendelson & Pramuk, 2009:418 –419.

Bufo (Incilius) nebulifer Fouquette & Dubois, 2014:315 .

Nomenclatural history. This species was originally described as Bufo granulosus by Baird & Girard (1852) Girard (1854) provided the replacement name Bufo nebulifer , as the original name was preoccupied by Bufo granulosus Spix, 1824 . Peters (1863) placed B. nebulifer in the synonymy of Mesoamerican species Bufo valliceps Wiegman, 1833 , where it remained until Mulcahy & Mendelson (2000) showed that the two species were distinct. Frost et al. (2006a) suggested multiple taxonomic changes among New World bufonids, and referred the taxon nebulifer into Cranopsis Cope, 1875 , which was shown by Frost et al. (2006b) to be preoccupied, so the taxon was referred to Ollotis Cope, 1875 . Ollotis was found also to be unavailable, so nebulifer was finally referred to Incilius Cope, 1863 , by Frost et al. (2009). Various English-language common names have been applied to this species, including Gulf Coast Toad, Coastal Plain Toad, Mexican Toad, Common Toad, and Nebulous Toad. Crother (2012) suggested the name Gulf Coast Toad, which is adopted here. Liner & Casas-Andreu (2008) suggested the standard Spanish name as Sapo nebuloso, but were consistent with Crother (2012) in suggesting the standard English name as Gulf Coast Toad.

Definition. Incilius nebulifer is a large toad, with adult females up to 125 mm and males to 98 mm SVL. The head is broad, with a complete complement of low, robust cranial crests. The snout is pointed in dorsal view, and rounded in profile. The tympanum is large (about 50% diameter of the eye). In males, the bilateral vocal slits are large and the m. interhyoideus forms a large, bilobed (anteroposteriorly), pigmented vocal sac that may be visible through the overlying gular skin. The skin is uniformly rough, with many evenly distributed sharply pointed tubercles. On the flanks a conspicuous lateral descending row of enlarged sharply pointed tubercles is evident. The ventral surfaces are granular, with unpointed tubercles. Ventral surfaces are usually uniform cream in color while dorsal surfaces are variable. In most individuals the dorsal pattern clearly shows a dark brown dorsal and dorsolateral background coloration, with a broad cream or yellow mid-dorsal stripe and paired dorsolateral stripes (usually ventral to the lateral row of tubercles) of a similar pale color. Variable pale brown or cream markings may be present, scattered across all dorsal surfaces. The tips of the digits are the same color as the remainder of the digit. The hands have short, robust fingers and lack webbing. The feet are long, with slender toes, being about halfwebbed.

The larvae are small (attaining 20–25 mm total length) and appear, without magnification, to be nearly uniformly dark gray dorsally, with a series of conspicuous pale spots extending down the dorsal ridge of the tail. The caudal fins are tall and transparent, with some scattered melanophores and iridiophores. The ventrolateral surfaces and the ventral half of the caudal musculature are dark gray with densely distributed silvery iridiophores. The oral disc and the marginal papillae are small and the tooth row formula is 2(2)/3; the A-2 gap is broad, being about one third the length of the A-2 row. The beak is small and shallowly notched.

Advertisement call has a mean frequency of 1479–1785 and a mean pulse of 33.14–38.17 (corrected to 25o C; Porter 1964a).

Diagnosis. A large species of Incilius (males to 98 mm SVL, females to 125 mm SVL) with the full complement of cranial crests (canthal, supraorbital, supratympanic, postorbital, parietal, preorbital, pretympanic, and suborbital), none of which are hypertrophied to any considerable degree. The tympanum is large (about 50% diameter of the eye), and usually in contact with the pretympanic crest. The skin is rough, with many evenly distributed sharply pointed tubercles over all dorsal surfaces, and with a distinct lateral descending row of enlarged sharply pointed tubercles on the flanks. Tibial glands are absent. The vocal slits are large and bilateral. The parotoid glands are distinctly triangular or subtriangular in shape. The color pattern is remarkably invariable, with most individuals having dark brown dorsal and dorsolateral background coloration, with a broad cream or yellow mid-dorsal stripe and paired dorsolateral stripes (usually ventral to the lateral row of tubercles) of a similar pale color. No individuals show a distinctive “dead leaf” color pattern dorsally. The tips of the digits are of a similar color to the rest of the digit.

Incilus nebulifer is similar in appearance to I. valliceps from which it most easily is distinguished by having the dorsal coloration described above ( Fig. 2 ), which is virtually absent in the otherwise polymorphic I. valliceps . The two species are parapatric about a geographic line crossing the Gulf Versant of Veracruz, Mexico, near the town of Palma Sola ( Mulcahy et al. 2006). The tadpoles of I. nebulifer ( Fig. 3 ) and I. valliceps are essentially indistinguishable, fitting the characters presented in the keys presented by Altig (1970), Altig et al. (1998), and Mendelson et al. (1999)—all presented under the taxon Bufo valliceps . Hybridization between these two species has not been documented.

Descriptions. The original description, as Bufo granulosus by Baird & Girard (1852) provided perfunctory details focusing on the cranial crests and coloration. The subsequent taxonomic note ( Girard 1854), replacing the preoccupied name granulosus with Bufo nebulifer , provided no additional morphological descriptions. Baird (1859) also presented a brief description. Cope (1889, as B. valliceps ) provided a description that is consistent with that of I. nebulifer (rather than I. valliceps ) and indeed it appears to be based mostly on material that is geographically referable to I. nebulifer ; references to specimens therein that geographically are referable to I. valliceps are limited to the “Varieties” section of the account. Kellogg’s (1932, as B. valliceps ) description is a composite representing specimens referable to both I. nebulifer and I. valliceps . Descriptions referable to I. nebulifer may be found in the following publications: Wright & Wright (1938; 1949; both as B. valliceps ); Blair et al. (1957, as B. valliceps ), Conant (1958; 1975; both as B. valliceps ); Dickerson (1969, as B. valliceps ), Cochran & Goin (1979), Smith (1978, as B. valliceps ); Behler & King (1979, as B. valliceps ); Garrett & Barker (1987, as B. valliceps ); Branson (1995, as B. valliceps ), Dundee et al. (1989, as B. valliceps ); Conant & Collins (1998, as B. valliceps ); Trauth et al. (2004, as B. nebulifer ), Lemos-Espinal & Smith (2007, as B. nebulifer ), Dorcas & Gibbons (2008, as B. nebulifer ); Elliott, Gerhardt, & Davidson (2009, as B. nebulifer / Ollotis nebulifer ), Oliver-López et al. (2009, as Ollotis nebulifer ), Tipton et al. (2012), and Lemos-Epinal & Dixon (2013). Descriptions of metamorphic and juvenile individuals were provided by Greuter (2004). Descriptions of the tadpole (as B. valliceps ) were presented by Wright (1929) and, in the form of dichotomous keys, were presented by Altig (1970), Altig et al. (1998), and Dodd (2013); Limbaugh & Volpe (1957) and Gosner (1960) described the tadpole through early development. Chromosomal information was presented by Cole et al. (1968), Bachman (1970), and Beck & Mahan (1979).

Illustrations. Illustrations appear in all of the references cited in “Descriptions” above except that of Baird & Girard (1852). The illustration in Cope (1889) is referable to I. nebulifer . Others published illustrations include Cochran (1961, as B. valliceps ), Clark (1971, as B. valliceps ), Blair (1972, as B. valliceps ), Mattison (2007, as B. nebulifer and Waddle (2011, as I. nebulifer ). Illustrations of several osteological elements, based on un-vouchered specimens(s) from San Luis Potosi, Mexico, were presented by Holman (2003). The drawing presented by Powell et al. (1998:fig. 58; as B. valliceps ) is intended to refer to populations in USA (i.e., I. nebulifer ) but in fact represents the Neotropical species I. campbelli ; Lemos-Espinal & Dixon (2013:fig. 6) reprinted the same image to represent I. nebulifer .

Fossil Record. Holman (2003) reviewed published accounts of fossils referred to B. cf. valliceps and B. valliceps from Scurry County and Culberson County, Texas, USA, respectively. Both records are presumed to be referable to I. nebulifer , though both are extralimital with respect to the modern range of the species. The Scurry County record is from the Pliocene, and the Culberson County record is from the Pleistocene. Mulcahy & Mendelson (2000) posited a Miocene–Pliocene vicariant speciation event separating I. nebulifer and I. valliceps along the Caribbean Coast of modern-day Veracruz, Mexico, with subsequent Pleistocene dispersal of I. nebulifer northward into modern-day USA. This hypothesis is not entirely consistent with the fossil records from western Texas, USA. Holman (2003) in his review of North American anuran fossils states definitively the only fossil record of I. valliceps (= presumably I. nebulifer ) is from Fowlkes Cave, Culberson County, Texas; thus he casts doubt on the validity of the Pliocene record from Scurry County, Texas.

Remarks. The town of Indianola, referenced in the type locality, no longer is recognized after being decimated by a series of hurricanes in the 1800s. It was located near the mouth of Matagorda Bay on the Gulf Coast of Calhoun County, Texas, USA, at approximately N 28o 30’, W 96 o 29’. Despite the initial taxonomic misstep by Baird & Girard (1852) and the recent taxonomic changes of generic names for the clade of Mesoamerican bufonids ( Frost et al. 2006a; 2006b; 2009), the species was referred consistently to as B. valliceps in all literature and taxonomic checklists (e.g., Gorham 1974) from the time of Cope (1863) until Mulcahy & Mendelson (2000) Consequently, the literature on this species is relatively simple to search and interpret, so long as the reader can determine the provenance of the material being discussed (i.e., USA and northern Mexico vs. southern Mexico and Central America) With this distinction in mind, the majority of the literature relating to ecology, behavior, and physiology that was published under the name Incilius (= Bufo ) valliceps actually pertains to I. nebulifer . Note that Trauth et al. (2004) incorrectly listed Mulcahy & Mendelson as the authority for the taxon nebulifer when, in fact, it is Girard.

Etymology. The name nebulifer is derived from nebula, meaning “cloud” and “fer” meaning “bearing” and is in reference to the generally clouded color pattern of this species. The etymology provided by Dodd (2013), for the taxon nebulifer , is incorrect.

Distribution. We present a map of locality records in Fig. 4. Consideration of the distribution of I. nebulifer suggests that it is limited at its southern extent by the seemingly minimal eastern tail of the Trans-Mexican Volcanic Axis (Mulcay et al. 2006), whereas it appears to be capitalizing upon human habitat disturbance and actively expanding its distribution eastward in the United States ( Vogel and Pechman 2010; Milko 2012). Presumably, the northern distributional limit is delimited by winter temperatures, although the species does occur in areas known to experience hard freezes. Similarly, it appears that the western distributional limits are contained by the cooler conditions on the uplift of the Sierra Madre Oriental in Mexico. In USA and extreme northern Mexico, the distributional pattern appears to follow permanent drainages in the Chihuahuan Desert, suggesting that aridity plays a factor in delimiting the range in this area. However, none of these hypotheses regarding physiological effects of low temperatures and dryness as factors limiting the distribution have been explicitly tested.

MAP. The distribution of Incilius nebulifer . Dots indicate locality records. The approximate location of the type locality is indicated with a star. Question mark indicates a valid specimen record that likely does not represent a natural, nor established, population (see text).

Distributional notes were presented by Hallowell (1856), Baird (1859), Garman (1887), Cope (1888), Strecker (1902), Stone (1903), Gadow (1905), Strecker (1908a, b; 1909; 1926a –d), Sanders (1909), Strecker (1926a – c), Strecker & Williams (1927), Strecker (1928), Burt & Burt (1929), Strecker (1930), Burt (1935), Strecker & Johnson (1935), Schmidt & Owens (1944), Smith & Buechner (1947), Smith (1948), Blair (1950), Brown (1950), Milstead et al. (1950), Peterson (1950), Reese & Firschein (1950), Anderson et al. (1952), Smith & Sanders (1952), Raun (1959), Milstead (1960), Webb & Packer (1961), Lewis (1974), Conant (1977), Carl (1980), Rackowitz et al. (1983), Thornton & Smith (1993), Blair et al. (1995), McAllister & Ward (1986), Fleet & Aubrey (1997), Ramírez-Bautista (1999), Dixon (2000), Dayton et al. (2001), Johnson (2002), Gifford & Fontenot (2003), Hibbitts et al. (2008), Price (2009), Lazcano et al. (2012), Dixon & Hibbitts (2013), Farr et al. (2013), and Maxwell (2013).

Although this species is listed in most literature and field guides (e.g., Conant & Collins 1998; Dorcas & Gibbons 2008) as occurring in the state of Arkansas, USA, Trauth et al. (2004) reported that the occurrence in that state is based on but a single record (first reported by Smith & Langebartel (1949) near Calion, Union County, Arkansas; no additional records have been found. While Trauth et al. (2004) continued to list the species as part of the fauna of Arkansas, it seems unlikely that a viable population ever existed within the boundaries of Arkansas; that record is indicated on the map herein, but is not considered as part of the natural range of the species. A geographically proximal record, from Morehouse Parish, Louisiana, USA, is based on a specimen in the University of Louisiana at Monroe (ULM 16976) and does appear to be properly identified (J. L. Carr, pers. comm.); we have no information to discredit the validity of its locality data. However, we agree with J. Boundy (pers. comm.) that the natural northern boundary of I. nebulifer in Louisiana appears to lie in the lower Red River Valley, in Rapides Parish. The locality mapped by Dundee et al. (1989) for Richland Parish is not based on an extant voucher specimen (J. Boundy, pers. comm.); so, we do not include that record here. Given the proximity of Caddo Parish, in northwestern Louisiana, to known records in adjacent counties in northeastern Texas gives us a somewhat objective reason to predict the presence of the species in northeastern Texas, despite the apparent lack of records. Specimens mapped from Jones County, Mississippi, USA (Mendelson, in Lannoo 2005) are based on specimens at the University of Southern Mississippi that have highly suspect locality data (R. L. Jones, pers. comm.); based on this information, we discount records from that county.

In the western extreme of its distribution, in the Chihuahuan Desert, I. nebulifer appears to be restricted to the primary watercourses draining into either basins or into the Rio Grande that forms the US –Mexican border. In Mexico, Lemos-Espinal et al. (2004) do not list this species, under any taxonomic name from the State of Chihuahua; based on records of species in drainages into the Rio Grande in Texas, USA, we suspect this species will be found in similar drainages in Chihuahua, Mexico. Espino de Castillo et al. (2009) mention a toad they refer to Incilius valliceps from Los Riscos cave, in the State of Querétaro, but with no mention of voucher specimens; we do not include this record on the map presented here.

Biology of The Gulf Coast Toad. The catalogue account for Bufo valliceps ( Porter, 1970) , as well as Porter’s (1962; 1964a–c) overall concept of the species, is a composite of I. nebulifer , I. valliceps , and additional species of Incilius ( Mendelson 1998) ; however, those records and literature cited that pertain to specimens from the currently known range of I. nebulifer are valid for this latter species.

Morphology. Morphological descriptions and analyses of morphological data were presented by Bauldauf (1958), McAlister (1961), W. Martin (1967; 1971), R. Martin (1972a, b), Martin & Gans (1972), Gans (1973), Emerson (1982), Hutchinson & Savitzky (2004) R. Martin (1972b). The analyses of sternal morphology and inguinal fat body organs by da Silva & Mendelson (1999) included specimens referable both to I. nebulifer and I. valliceps , however no differences in these structures are evident between the two species ( Mendelson et al. 2011). The osteological review provided by Martin (1973) is problematic because it was based on specimens referable to I. nebulifer , but also included a skeletal specimen identified as Bufo valliceps (the specimen in Martin 1973:fig. 2D is TNHC 41994; T. LaDuc, in lett.); this specimen bears the locality data “ Mexico: Sinaloa” which is greatly extralimital for the either I. nebulifer or I. valliceps . Blair (1962; 1970) discussed the importance of various types of data to inform understanding of this species, with respect to other bufonids. Cytological comparisons with other bufonid species were presented by Sanders & Cross (1964). A morphologically anomalous specimen was described by Freed (1992) and larval deformities by Drake et al. (2007). Effects of long-term preservation on specimens were reported by Deichmann et al. (2009).

Reproduction, development, and hybridization. Various aspects of the reproductive biology, including the advertisement calls, of I. nebulifer have been documented by A. P. Blair (1947), Wright & Wright (1949), Duran (1954), Martin (1958), W. F. Blair (1956a; 1960a), Thornton (1960), Awbrey (1963), Porter (1964a), Hubbs & Martin (1967), Grubb (1970, 1973a), W. Martin (1972), Wiest (1982), Sullivan & Wagner (1988), Dundee et al. (1989), Ryan & Sullivan (1989), Branson (1995), Wagner & Sullivan (1992; 1995), Foley (1994), Greuter (2004), Lannoo et al. (2005), Salinas (2009), Jones & Ratnam (2009), Pierce & Hall (2012), and Oyervides & Zaidan (2013). Development, metamorphosis, and ontogeny and factors affecting them have been documented by Taylor (1942), Wright & Wright (1949), Volpe (1957), Limbaugh (1956), Limbaugh & Volpe (1957), Conant (1958, 1975); Blair (1953; 1956b; 1960a; 1963), Turner (1960, 1962), Hubbs et al. (1963), Ballinger & McKinney (1966), Yew (1966; 1969), Licht (1967), Grubb (1973b), Dundee et al. (1989), Pierce & Montgomery (1989), Nelson (1993), Rosenberg (1990), Rosenberg & Pierce (1995), and Conant & Collins (1998). Various aspects of hybridization with other anurans have been discussed by Blair (1941), Orton (1951), Liner (1954), Thornton (1954, 1955), A. P. Blair (1941), W. G. Blair (1956b; 1958; 1959; 1960a; 1961b; 1963; 1964; 1966; 1972), Moore (1955), Volpe (1956; 1959; 1960), Gosner & Black (1958), Fox et al. (1961), Kennedy (1962), Brown (1971a, b), Guttman (1972), Brown & Brownell (1971), Brownell (1971), Sanders (1978; 1985; 1986), Hillis et al. (1984), Dundee et al. (1989), Greuter (2004), Brown & Mesrobian (2005), Mulcahy et al. (2006), and Mendelson et al. (2011). This older literature regarding hybridization must be interpreted in the context of the taxonomic separation of I. nebulifer and I. valliceps by Mulcahy & Mendelson (2000), and also in the context of the re-analyses of data from the laboratory of W. F. Blair presented by (2008) and subsequently re-analyzed by Brandvain et al. (2014). Additional, recent, studies of hybridization were presented by Vogel (2007) and Vogel & Johnson (2008).

Habitat use. Habitat use by the adults has been discussed by Pope (1919), Wright & Wright (1949), Thornton (1960), Awbrey (1963), Brattstrom (1963), Wilks (1963), Grubb (1968, 1970), Neill & Grubb (1971), Grubb (1976), Moore (1976), Whiting et al. (1987), Dundee et al. (1989), McAllister et al. (1989), Foley (1994), Reid & Whiting (1994), Irwin (1997), Mendelson (1998), Mulcahy & Mendelson (2000), Means (2005), Mulcahy et al. (2006), Lemos-Espinal & Smith (2007), Vogel & Johnson (2008), Salinas (2009), Oliver-López et al (2009), Gehlbach (2010), Walls et al. (2011), Hernández-Salinas et al. (2012), and Milko (2012). Associations with caves has been reported by Mohr (1948), McAlister (1954), Baker (1957), Redell & Knox (1962), Redell & Finch (1963), and Reddell (1970). Specific associations with saltwater were documented by Viosca (1926), Allen (1932), Burger et al. (1949), reviewed by Neill (1958), Mueller (1985), Alexander et al. (2012) and Hua & Pierce (2013). Responses to fire were reported by Brown et al. (2011; 2014). Potential effects of exposure to introduced plant species were reported by Cotton (2009) and Cotten et al. (2013).

Community ecology. Feeding ecology has been documented by Strecker (1927a), Campbell & Davis (1968), Clark (1969), and McGehee et al. (2001). Predators and possible antipredator mechanisms have been documented by Strecker (1927b), Wright & Wright (1949), Licht (1968), Neill (1968a, b), Grubb (1972), Clark (1974), Brown (1974), Platt & Fontenot (1993), Tucker (1994), Adams (2005), and Mendelson (2005). Palatability of the tadpoles was tested by Adams et al. (2011). Parasites have been reported by Walton (1929), Harwood (1930), Hoffpauir & Morrison (1966), McAllister et al. (1989), McAllister & Donn (1990), and Martin & Dresser (1991). Pathogens were reported by Gaertner et al (2010), and Saenz et al. (2010). Interspecific associations with other anurans have been discussed by Glass (1946), Wright & Wright (1949), Axtell (1958), Blair (1961a), James (1966), Moore (1976), Gambs & Littlejohn (1979), Foley (2005), Mitchell & Lannoo (2005a, b), Schwalbe & Goldberg (2005), Franklin & Killpack (2005), Sredl (2005), Sredl & Field (2005), Sullivan (2005), Wallace (2005), Vogel & Pechmann (2010), and Preston et al. (2014). Associations with other species caught in traps with this species were reported by Blair (1960b). Population trends were discussed by Boundy (2005). Camper & Dixon (1988) evaluated a microchip marking technology in the species. Road and industrial mortality was reported by Flickinger (1981) and Ray et al. (2006); road mortality and scavenging by Thamnophis proximus was reported by Watson (2007).

Physiology and behavior. Various aspects of the physiological parameters and responses in this species have been presented by Morgan & Stokes (1936), Svedberg & Hedenius (1934), Sanders (1962), Wittliff (1964), Campbell & Davis (1971), Guttman (1974), Withers (1978), Prasad et al. (1984), Wygoda (1989), Williams (1992), Williams & Wygoda (1993), Verma & Pierce (1994), Moore (1997), and Rowson et al. (2001). Veterinary protocols were presented by Brannelly et al. (2012) and Brannelly (2014) and notes on captive care were provided by Walsh et al. (1992). Phototactic responses were presented by Jaeger & Hailman (1973) and Hailman & Jaeger (1974); however, the source for the specimens used by Jaeger & Hailman (1973, presented as B. valliceps ) is not reported, so referral of data as relevant to I. nebulifer is speculative. Interspecific effects of injections of pituitary extracts were presented by Quinn & Mengden (1984). Hemoglobins and transferrins were described by Fox et al. (1961). Resistance to cardiotoxins was reported by Moore et al. (2009) The parotoid secretions were analyzed by Porter (1964c), but results are based on specimens referable both to I. nebulifer and I. valliceps . Serological comparisons were made by Durio (1960) and biochemical components in the skin were analyzed by Cei et al. (1968). Use of this species for human pregnancy testing was evaluated by Aguirre-Pequeno (1950). Effects of potentially toxic chemicals were evaluated by Chen & Chen (1933), and Shaw & Grushkin (1957). Effects of radiation were reported by Blair (1960c) and Clayton (1960). Clark (1971) reported on use of branding as a means of marking individuals. Greding (1971) reported on learning in this species.

Evolution. The phylogenetic literature, with respect to I. nebulifer , can be difficult to interpret if the authors did not state the provenance of the samples used in their analyses. For example, Baldauf (1959) implies that the individuals used in his morphological analyses were collected in the USA (and possibly may be the same individuals reported by Baldauf, 1958), but one cannot be certain. Maxson (1984) and Maxson et al. (1981) included “ Bufo valliceps ” in their studies from Texas, so they can be assigned with certainty to I. nebulifer .

All phylogenetic treatments of the taxon “ valliceps ” published prior to 2000 were based, variously, on specimens or samples representing either I. valliceps (sensu stricto) or I. nebulifer . The modern reader of those papers is encouraged to check the geographic source of the material included in any particular analysis and assign the appropriate taxonomic name. Because of the well-supported sister-taxon relationship between I. nebulifer and I. valliceps ( Mulcahy & Mendelson 2000; Mulcahy et al. 2006; Mendelson et al. 2011), the taxonomic differences typically have virtually no bearing on the overall evolutionary discussions presented by those authors. The exception, however, is the result presented by Van Bocxclaer et al. (2010), wherein they reported that the species pair valliceps + nebulifer ) was rendered paraphyletic by a sample identified as “ I. macrocristata ” (= I. macrocristatus ). Mendelson et al. (2011) reviewed all of the relevant material, presented a clarification of the issue and determined that Van Boxclaer et al. (2010) had included a misidentified specimen in their analyses (i.e., their sample of “ I. macrocristata ” actually represented I. valliceps ). In their broad analysis of amphibian relationships, Pyron & Wiens (2011) chose to compile various published genetic sequences (i.e., GenBank) to create chimera to represent the taxa “ Bufo valliceps ” and “ Bufo nebulifer ” for their analyses; their compilation of sequences from various sources into singular OTUs included the misidentified material from Van Bocxlaer et al. (2010), with the result that Pyron & Wiens presented “ valliceps ” and “ nebulifer ” not to be sister taxa. Because their analyses include clearly misidentified material, this section of their overall phylogenetic tree is inadmissible. Thus, the sister relationship between I. valliceps + I. nebulifer remains is supported by all modern phylogenetic analyses that are based on accurately identified material. Phylogenetic relationships, biogeographic history, and evolutionary natural history of I. nebulifer were presented and discussed by Mulcahy & Mendelson (2000), Mulcahy et al. (2006), and Mendelson et al. (2011). The relative phylogenetic diversity of I. nebulifer , with respect to other North American bufonids, in terms of conservation prioritization was presented and discussed by Goebel (2005).

Conservation and education. Summary of possible conservation threats to this species were presented by Hammerson & Canseco-Márquez (2004), Mendelson (2005), Frías-Alvarez et al. (2010). Use of habitat by this species following mining activities was reported by Walton (2012). Use of these common toads in conservationawareness education programs was described by Rommel (2012).

Figures

FIGURE 2. Incilius nebulifer, in life. An adult male photographed in the wild in Harris County, Texas, USA, by Matthijs Hollanders.

FIGURE 3. Incilius nebulifer, in life. A larval tadpole; image reproduced from Altig et al. (1998).