Bioacoustics of Hyloxalus arliensis

Diagnosis. Hyloxalus arliensis sp. nov. is a small frog ( Figures 5–6 ) with an arm gland in the adult males ( Figure 2 ), a character which differentiates this species from other species of Hyloxalus , except for H. anthracinus , H. cevallosi , H . exasperatus , H. fascianigrus , H. lehmanni , H. ramosi , H. saltuarius , and H. nexipus (Grant & Castro- Herrera 1998; Grant & Ardila-Robayo 2002 ; Grant et al. 2006 ; 2017 ) ( Figure 7 ). Although the color of the arm gland in H. arliensis distinguishes the species from all Hyloxalus except for H. saltuarius , given the somewhat variable nature of gland color we provide comparisons against all Hyloxalus with arm gland, regardless of its color. Hyloxalus arliensis sp. nov. differs from H. fascianigrus by ventral coloration of the belly, cream with sparse stippling in adult males ( vs. large white spots on dark ground belly in H. fascianigrus ; Figure 7 ), pale arm gland ( vs. black arm gland in H. fascianigrus ; Figure 2 C-D), and 2–3 notes/ms (vs. 1 notes/ms in H. fascianigrus ). The new species differs from H. saltuarius by having the throat, chest, and anterior belly cream with diffuse dark stippling that darkens on males and is immaculate in females ( vs. completely black in both sexes in H. saltuarius ), and the complete lateral and solid oblique lateral stripe (OLS), (usually broken into a series of elongated spots in H. saltuarius ). The new species differs from Hyloxalus ramosi by having a dark longitudinal line on anterior surface of thigh (absent in H. ramosi ); the throat, chest, and anterior belly cream with diffuse dark stippling that darkening these regions in males vs. completely black in males of H. ramosi ; Figure 7 ), pale arm gland ( vs. black arm gland in H. ramosi ; Figure 2 A-B), and by the smaller size SVL in adult females (16.0–17.0 mm) and adult males (14.6–16.7) mm ( vs. SVL in adult females 20–20.2 mm and adult males 18.5–19.1 mm in H. ramosi ). Differs from H. exasperatus by having a complete oblique lateral stripe (incomplete, short, extending to 1/3 of the body in H. exasperatus sensu Coloma 1995 ), the absence of lateral keeled in toe IV (present in H. exasperatus sensu Coloma 1995 ), and lacking a dorsolateral stripe (present in H. exasperatus ). Differs from H. lehmanni by having smaller body size, SVL 14.6–16.7 mm in adult males and 16.0–17.0 mm in adult females ( vs. SVL 18.4–19.8 mm in adult males and 19.7–22.1 mm in adult females in H. lehmanni ), and the ventrolateral region of body without or with scarce white dots (notable white spots or wavy white ventrolateral stripe in H. lehmanni ). Differs from H. cevallosi by the absence of the ventrolateral stripe (present in H. cevallosi ), and having a smaller snout-vent length (SVL 14.6–16.7 mm ) in adult males and (16.0–17.0 mm) in adult females ( vs. SVL 18.2 mm in adult male and 20.6–21.0 mm in adult females in H. cevallosi ). Hyloxalus arliensis sp. nov. differs from H. anthracinus by having a smaller size (SVL 14.6–16.7 mm ) in adult males and (16.0–17.0 mm) in adult females ( vs. SVL 16.2–19.0 mm in adult males and 17.1–23.6 mm in adult females in H. anthracinus sensu Coloma 1995 ), and ventral coloration of the belly, cream with sparse stippling in adult males (solid black darkening on abdomen in males, venter white in females sensu Coloma 1995 ). Finally, H. arliensis sp. nov. differs from H. nexipus by lacking fringes on hands (a well-developed fringes in H. nexipus sensu Coloma 1995 ), dorsolateral stripe absent (present and incomplete in H. nexipus sensu Coloma 1995 ) and the call repertoire of Hyloxalus arliensis sp. nov. is composed of peep calls with a dominant frequency 4808–6387 Hz ( vs. trills calls with 2500–4700 Hz in H. nexipus sensu Coloma 1995 ).

Distribution . Hyloxalus arliensis sp. nov. occurs at elevations between 565 and 1200 m a.s.l. on Andean slopes from the Magdalena valley in Antioquia , Boyacá , Cundinamarca , Santander and Tolima departments. Currently known from six localities ( Figure 9 ), five of these localities lie on the western slope of the Cordillera Oriental of Colombia ( Figure 9 A–E). The other sixth locality lies on the eastern slope of the Cordillera Central ( Figure 9F ). Advertisement call. Hyloxalus arliensis sp. nov. was recorded vocalizing hidden under leaf litter or ferns at the base of bushes near slow-flowing streams ( Figures 10–11 ), up to 1 m distant from the riverside, active during the rainy season. We recorded two minutes of advertisement calls on November 15, 2007 in the municipality of Viotá, Cundinamarca Department , Colombia ( 4°26’ N , 74°25’ W , datum WGS 84, 1100 m a.s.l.). Two specimens (IAvH- Am-8861-2) were recorded (BSA-15993) between 16:25–16:40 hours at a temperature ranging from 28–28.9 oC and at an environmental relative humidity between 64–65%. Temporal structure: The advertisement call of Hyloxalus arliensis sp. nov. consists of long trains of single notes (“peep”) with rapid and successive repetitions (two to three notes per milisecond) ( Figure 10 ). The note rate varied between 89–132 notes/min. The note duration ( Figure 11 ) was between 0.022 – 0.041 s (mean 0.035 + 0.005, n = 23), with 198–223 (mean 209 + 7.31, n = 22) oscillations contained in each note. The internote interval varied between 0.322 – 0.638 s (mean 0.42 + 0.006, n = 22). Spectral structure: Five to six harmonics were developed, with the dominant frequency 4808–6387 Hz (mean 5635 + 717, n = 25) and fundamental frequency in 2266–4086 Hz (mean 3037 + 787, n = 21). Natural History. Hyloxalus arliensis sp. nov. is a diurnal species inhabiting heterogeneous agricultural areas ( Figure 12 ) in the lowland Andes of the middle Magdalena River valley, associated with vegetation that borders slow flowing streams. Some specimens were found up to four meters away from the creek, in deforested areas dominated by grasslands or shrubby vegetation. This species was active during the rainy season between February to May and September to November. Generally, adult males vocalize after rains, calling from the ground hidden at the base of plants, usually Araceas or ferns; juvenile and post-metamorphic individuals were found hidden in the leaf litter. The clutch size consists of eight pigmented eggs ( Figure 12 E ). Tadpoles are located in pools separate from the streamflow. Hyloxalus arliensis sp. nov. is syntopic with other species of the superfamily Dendrobatoidea ( sensu Grant et al. 2006 ) such as Rheobates palmatus and Dendrobates truncatus .