Hope in the dark: discovery of a population related to the presumably extinct micro-endemic Blunt-headed Salamander (Ambystoma amblycephalum)

Figures & data

Figure 1. Area survey in this study (red), with approximate location of the discovered Nahuatzen population assigned to Ambystoma cf. amblycephalum in 2018 (marker 1), as well the two other scientifically documented records: the type locality of A. amblycephalum described by 22 (marker 2), and the origin of the genetic sample included in 17 (marker 3).

Figure 2. (a) The breeding site of A. cf. amblycephalum at Nahuatzen, and photographs of (b) a paedomorphic adult; (c) a terrestrial adult; (d) a tadpole.

Table 1. Measurements of adults related to Ambystoma amblycephalum (in mm). The first three compose the type series of the species [22]; the following seven are the new specimens caught at Nahuatzen. F = female; M = male; L = larvae; SVL = snout-vent length; TL = total length; TAL = tail length; HW = head width; HL: head length; LAL: leg length; SL = snout length; ND = nostril diameter; IN = inter-nostril distance

Types	EHT-HMS 16443 now FMNH 100104 (holotype)	EHT-HMS 16442 (paratype)	EHT-HMS 16444 (paratype)	Nahuatzen 2018 specimens
Sex	F	F	F	F	M	M	F	F	M	F	L	L	L
SVL	90.0	93.0	64.5	91.0	70.5	66.4	75.4	59.9	45.4	42.0	21	14	16
TL	161.0	153.0	106.5	160.5	128.8	120.9	139.5	108.5	84.9	78.5
TAL	71.0	60.0	42.0	69.5	58.3	54.5	64.1	48.6	39.5	36.5	25	16	18
HL	16.8	15.9	12.8	15.5	13.1	11.9	13.7	11.6	8.6	8.0
HW	17.5	16.5	13.5	16.8	13.6	12.7	14.2	12.2	9.1	8.8
LAL	30.0	33.2	27.1	31.9	26.6	25.2	28.1	24.2	16.6	15.5
SL				22.3	18.7	16.6	18.5	16.1	12.0	11.5
ND				8.1	7.2	6.9	7.8	5.8	3.7	3.5
IN				14.5	15.9	12.3	13.8	10.8	8.7	8.5
TBW				21.1	13.8	14.1	14.8	12.5	10.7	10.7

Figure 3. Climatic records of the Nahuatzen area over the 2014–2018 period. (a) Maximum (red), average (light blue) and minimum (dark blue) temperatures (c); (b) Precipitation (mm, blue areas) and rainy days (black histograms).

Table 2. Ranges of air temperature and water chemistry in the aquatic sites of A. cf. amblycephalum compared to other Ambystomatids observed during the survey [37]

Taxon	Air Temperature (°C)	Water Temperature (°C)	pH	mV
A. cf. amblycephalum (n = 2)	25.4–27.1	23.1–24.8	9.43–9.45	223–230
A. flavipiperatum (n = 1)	19.6–22.4	16.4–18.3	6.96–7.21	401–410
A. ordinarium (n = 1)	22.9–26.7	19.0–19.2	7.92–8.06	301–306

Figure 4. A. tigrinum stebbinsi of the Bayesian phylogenetic reconstruction of available Ambystoma mitochondrial sequences (concatenated 16S + control region = 1,296bp). Supported branches (posterior probability >0.95) are indicated by asterisks. The matriline of the Nahuatzen population groups with A. amblycephalum and A. mexicanum.

Figure 5. Bayesian phylogeny (maximum clade-credibility tree) of the mitochondrial control region [755bp) from Nahuatzen and other Ambystoma sequences from the study of 30. Supported branches (posterior probability >0.95] are indicated by asterisks.

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