Allobates alessandroi (Grant and Rodriguez, 2001)

Melo-Sampaio, Paulo R., Prates, Ivan, Peloso, Pedro L. V., Recoder, Renato, Dal Vechio, Francisco, Marques-Souza, Sergio & Rodrigues, Miguel T., 2020, A new nurse frog from Southwestern Amazonian highlands, with notes on the phylogenetic affinities of Allobates alessandroi (Aromobatidae), Journal of Natural History 54 (1 - 4), pp. 43-62 : 55-56

Notes on Allobates alessandroi

After examination of the morphology of other Allobates species known to occur in montane areas, we concluded that Allobates alessandroi ( Grant and Rodríguez, 2001) is likely taxonomically misplaced.

Allobates alessandroi ( Figure 6) was described based on five specimens collected in the Peruvian Andes (Cusco and Puno provinces). The species has a large body size in males when compared to most Allobates taxa (> 20 mm SVL). It is also the only species of Allobates with welldeveloped fringes on both edges of all toes ( Figure 6 (a)), keel-like lateral fringes on the fingers (most prominent distally), and two subarticular tubercles on Finger IV ( Figure 6 (b)) ( Grant and Rodríguez 2001). The presence of webbed or fringed toes, unknown in other Allobates , is a diagnostic character of Hyloxalus ( Noble 1931; Dunn 1933; Grant et al. 2006). Furthermore, the following additional characters of A. alessandroi are also diagnostic for Hyloxalus Jiménez de la Espada, 1870 (as proposed by Grant et al. 2006; emendation by, Grant et al. 2017 in bold): (1) dorsal colouration generally cryptic, brown, grey, or black; (2) pale oblique lateral stripe present; (3) pale dorsolateral stripe absent in most (but not all) species; (4) pale ventrolateral stripe usually absent; (5) dorsal skin texture posteriorly granular; (6) toe webbing varying from absent in most species to basal or extensive in some species; (7) Finger III of adult males (often) not swollen; (8) Finger I (often) shorter than Finger II; (9) finger discs narrow to moderately expanded; (10) median lingual process absent; and (11) dark throat collar absent. Recently, Grant et al. (2017) found a swollen Finger III in species of Hyloxalus , a trait that is also present in A. alessandroi .

To our knowledge, A. alessandroi is known only from the type series and has no DNA sequence data available; the current phylogenetic placement of this species can thus be considered tentative. In the absence of molecular data and based on the morphological attributes presented above, we assign A. alessandroi to the genus Hyloxalus under Hyloxalus alessandroi new combination. If this species was indeed a member of Allobates , its unique morphology would represent a remarkable case of convergence with Hyloxalus , potentially as an adaptation to life in rocky streams. Such traits, however, are not observed in A. pacaas and other Allobates species known to inhabit similar habitats.

Other Allobates species have unclear taxonomic affinities and may need to be reassessed. Recently, Allobates picachos ( Ardila-Robayo, Acosta-Galvis, and Coloma, 2000) was allocated to Hyloxalus by Acosta-Galvis and Vargas-Ramírez (2018) based on molecular data. Other species that may deserve consideration are Allobates mandelorum ( Schmidt, 1932) (as noted by Barrio-Amorós et al. 2019), Allobates sanmartini ( Rivero, Langone, and Prigioni, 1986) , and Allobates wayuu ( Acosta-Galvis, Cuentas, and Coloma, 1999) , three species tentatively allocated to Allobates by Grant et al. (2006). Similar to A. alessandroi , the last two species have attributes typical of Hyloxalus , such as Finger I smaller than Finger II, two tubercles on Finger IV, well-developed interdigital membranes on toes, and presence of an oblique lateral line. To reassess the generic status of these and other poorly known species, future studies will benefit from the re-examination of morphological attributes and incorporation of additional data types.