Eleutherodactylus nitidus (Peters, 1870)

Grünwald, Christoph I., Reyes-Velasco, Jacobo, Franz-Chávez, Héctor, Morales-Flores, Karen I., Ahumada-Carrillo, Ivan T., Rodriguez, Christopher M. & Jones, Jason M., 2021, Two new species of Eleutherodactylus (Anura: Eleutherodactylidae) from Southern Mexico, with comments on the taxonomy of related species and their advertisement calls, Amphibian & Reptile Conservation (e 272) 15 (1), pp. 1-35 : 14-16

Summary Data for Eleutherodactylus nitidus Species Group Members

To help differentiate between the two new species described above, and the related species in the Eleutherodactylus nitidus species group, important morphological, mensural, and call differences of all of the species in this group are collated into a single table ( Table 3 ), and photographs of related species in the E. nitidus species group are provided ( Figs. 9–10 ). The distributions of the species in the E. nitidus group are mapped in Figs. 7 and 13.

Differentiating the Advertisement Calls of Closely Related Eleutherodactylus nitidus Species Group Members

Recordings were made from 120 calling males of all 24 species of Eleutherodactylus from western Mexico. The calls of the species analyzed were found to fall into five different categories of a rapid burst whistle (trill), a drawn-out whistle (whistle), a strong high-pitched chirp (peep), a soft high-pitched chirp (chirp), and a drawn-out chirp (pipe). Of the species analyzed herein, four ( E. dilatus , E. nebulosus , E. pipilans , E. sentinelus ) produce a strongly high-pitched chirp (peep), four ( E. albolabris , E. nitidus , E. orarius , E. petersi ) produce a drawn-out whistle (whistle), two ( E. maculabialis and E. syristes ) produce multi-note or pulsed calls (trill) of various rates and notes, and one ( E. maurus ) produces a slow and drawn-out chirp (pipe). While a detailed account is given of the calls of the species we describe here, as well as some of their relatives, we refrain from giving detailed descriptions of the calls of E. nitidus , E. albolabris , E. orarius , E. petersi , E. pipilans , E. nebulosus , and “ E. rubrimactulatus ” pending a more detailed taxonomic study of this species complex.

Eleutherodactylus dilatus . The advertisement call of E. dilatus is a single high-pitched “chirp” best described as a “peep” ( Fig. 11C ). Calls recorded at the type locality consist of a rapid chirp, with an average duration of 110 ms, and a dominant frequency ranging between starting at 2,550 kHz and 2,780 kHz.

Eleutherodactylus maculabialis . The advertisement call of E. maculabialis is a relatively slow multi-note “trill” ( Fig. 3 ). Calls recorded at the type locality consist of slow six-note trills with a duration of 180–210 ms, and a dominant frequency starting at 2,600 –2,900 kHz and rising to 3,050 –3,200 kHz. The call interval is about 40–55 ms ( Fig. 3A ). At a nearby locality at 1,320 m asl ( Fig. 3B ), calls were recorded of two males which varied from the type locality in consisting of five-note trills with an average duration of 230 ms and a dominant frequency starting at 3,630 kHz and reaching 4,000 kHz ( Table 4 ).

Eleutherodactylus maurus . The advertisement call of E. maurus is a single, drawn-out “chirp” best described as a “pipe.” Calls recorded near Ocuilan, in Estado de México, consisted of a single chirp with a duration of 205 ms, and a dominant frequency starting at 2,760 kHz and rising to 3,150 kHz. The amplitude was strongest at the middle of a call ( Fig. 11D ). At a locality near Taxco, Guerrero, a call of E. maurus was recorded which consisted of a single, drawn-out chirp. However, the call was longer, averaging 275 ms and the amplitude was distributed in three sub-pulses. This indicates a further need to investigate this population.

Eleutherodactylus sentinelus . The advertisement call of E. sentinelus is a single high-pitched “chirp” best described as a “peep” ( Fig. 3 ). Calls recorded at the type locality consist of a rapid chirp, with an average duration of 160 ms, and a dominant frequency starting at 2,560 kHz and rising to 3,100 kHz ( Fig. 3D ). Calls recorded above the type locality at 1,900 m asl ( Fig. 3C ) are slightly shorter and of higher frequency, with an average duration of 120 ms, and a dominant frequency starting at 2,700 kHz and finishing at 3,300 kHz ( Table 4 ).

Eleutherodactylus syristes . The advertisement call of E. syristes is a rapid but long multiple-pulse “trill” ( Fig. 11A–B ). Calls recorded at two different localities in Guerrero consisted of 49–60 pulses, about 10 ms apart, with a total duration of the call averaging 500– 560 ms. The dominant frequency at Agua de Obispo , Guerrero, was between 2,700 –3,170 kHz, starting lower, peaking, and then lowering again ( Fig. 11A ). At a second locality, slightly lower than Agua de Obispo , east of Highway 95, the calls tended to have a dominant frequency ranging between 3,000 –3,390 kHz ( Fig. 11B ).

Eleutherodactylus albolabris . The advertisement call of E. albolabris is a single, multi-pulsed whistle, with the call continuous amongst the pulses and with a duration of approximately 150–250 ms ( Fig. 11F ). Calls recorded at the type locality at Agua de Obispo had a duration of 160 ms, and started at a dominant frequency of 2,840 kHz rising to 3,015 kHz. Calls varied between 7–10 continuous pulses. At a second locality, near Vallecitos in the Municipality of José Azueta , Guerrero, the calls had a duration of 240 ms, and started at a dominant frequency of 2,740 kHz which rose to 2,915 kHz. Calls started with a multi-pulsed trill and then ended with several distinct pulses. This population’s call is best described as a combination of a “trill” with a “whistle” ( Fig. 11E ).

Molecular Analysis of the Eleutherodactylus nitidus Species Group

The molecular phylogeny based on the mitochondrial rRNA 16S recovered a well-supported Eleutherodactylus nitidus species group (posterior probability (pp) 1; Figs. 12 and S 1 ), which is sister to the E. modestus group as defined by Grünwald et al. (2018). As with previous phylogenies of the group based on 16S, some of the intermediate nodes in the phylogeny are not well supported (pp <0.5), and we have collapsed all nodes below this value.

In the Eleutherodactylus nitidus species group, we recovered two main clades. The first one is composed of E. pipilans , E. erythrochomus , and E. nebulosus , while the second group includes all the other species. In the second group, many of the intermediate nodes have little to no support. However, individual species do show strong support (pp = 1) in most cases, including E. dilatus , E. sentinelus , E. maurus , and E. syristes , while E. maculabialis has a posterior support of 0.86.

All the remaining species in the group form a second, well-supported clade (pp =0.99). In this clade, we recovered an early split between Eleutherodactylus albolabris and the other species, which include E. orarius , E. petersi , E. nitidus , and a hitherto undescribed form from Jalisco and Nayarit ( Fig. 13 ). We refrain from describing the western-most form at this time, as material from the type locality of E. petersi is unavailable, so the relationship of the western form with E. petersi remains unclear.

We believe that a more detailed study of the taxa related to E. nitidus is needed, when more thorough sampling is available and employing more populationlevel specific tools, such as genome-wide SNP data, in order to better understand the patterns of gene-flow and introgression.

Figures

Fig. 9. Comparison photos of Eleutherodactylus species related to E. nitidus in life. (A–I) E. syristes from the vicinity of Agua de Obispo, Municipality of Chilpancingo, Guerrero, Mexico. (J–O) E. albolabris from Agua de Obispo, Municipality of Chilpancingo, Guerrero, Mexico. (P–R) E. nitidus from Yerba Santa, Municipality of General Heliodoro Castillo, Guerrero, Mexico.

Fig. 10. Comparison photos of Eleutherodactylus species related to E. nitidus in life. (A–I) E. dilatus from Omiltemi, Municipality of Chilpancingo, Guerrero, Mexico. (J–O) E. petersi from Puerto El Balsamo, Municipality of José Azueta, Guerrero, Mexico. (P–R) E. pipilans from Acahuizotla, Municipality of Chilpancingo, Guerrero, Mexico.

Fig. 7. (A) Map showing the type localities and distribution of Eleutherodactylus species related to E. nitidus in southern Mexico. The stars represent type localities and circles represent additional localities, with each color coded for the species: E. sentinelus sp. nov. (purple), E. maculabialis sp. nov. (green), E. dilatus (pink), E. maurus (yellow), and E. syristes (blue). (B) Map showing the type localities and distribution of Eleutherodactylus species related to E. pipilans in southern Mexico. The red star represents the type locality of E. pipilans and red circles represent additional localities. The black star represents the type locality of E. nebulosus and black circles represent additional localities.

Fig. 13. Map of type localities and distributions of members of the Eleutherodactylus nitidus species group. Purple circles represent localities of an undescribed species related to E. petersi. For the other four species, stars represent the type localities and circles represent additional localities, which are color coded for species: E. orarius (red), E. albolabris (blue), E. nitidus (green), and E. petersi (orange).

Fig. 11. Oscillograms and spectrograms of the advertisement calls of adult males of Eleutherodactylus species related to E. maculabialis sp. nov. and E. sentinelus sp. nov. (A) E. syristes fromAgua del Obispo, Guerrero, Mexico.(B) E. syristes from east of Hwy. 95, near Acahuizotla, Guerrero, Mexico. (C) E. dilatus from Municipality of Chilpancingo, Guerrero, Mexico. (D) E. maurus from Municipality of Ocuilán, Estado de México, Mexico. (E) E. albolabris from Municipality of Agua de Obispo, Guerrero, Mexico. (F) E. albolabris from Vallecitos, Guerrero, Mexico.

Fig. 3. Oscillograms and spectrograms of the advertisement calls of Eleutherodactylus maculabialis sp. nov. and Eleutherodactylus sentinelus sp. nov. (A) Adult male E. maculabialis sp. nov. from type locality. (B) Adult male E. maculabialis sp. nov. from 1.0 km S of bridge between Nueva Delhi and El Paraíso, Municipality of Atoyac de Álvarez, Guerrero, Mexico. (C) Adult male Eleutherodactylus sentinelus sp. nov. from Puerto El Balsamo, Municipality of José Azueta, Guerrero, Mexico. (D) Adult male Eleutherodactylus sentinelus sp. nov. from type locality.

Fig. 12. Bayesian phylogenetic inference of members of the Eleutherodactylus subgenus Syrrhophus, with a focus on the E. nitidus species group, based on the mitochondrial loci 16S rRNA. Black circles represent nodes with a posterior support of 1. All nodes with support of less than 0.5 are collapsed.

Fig. 1. Holotype of Eleutherodactylus maculabialis sp. nov., MZFC 33312 (CIG 00921) from 11.4 km S of Puerto de Gallo, Municipio de Atoyac de Álvarez, Guerrero, Mexico. (A) Dorsolateral perspective in life. (B) Lateral perspective in life. (C) Ventral perspective in life. (D) Dorsal perspective in preservative. (E) Ventral perspective in preservative.