Agkistrodon

Burbrink, Frank T. & Guiher, Timothy J., 2015, Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon, Zoological Journal of the Linnean Society 173 (2), pp. 505-526 : 522

AGKISTRODON CONANTI ( GLOYD, 1969)

Florida Cottonmouth

Holotype: USNM165962 , collected by R. P. Elliot, J. Wariner, and P. Pinnel.

Type locality: Seven miles south-east Gainseville, FL.

Etymology: Specific epithet is a patronym honoring Roger Conant, a prominent American herpetologist of the 20th Century.

Synonymy: This species comprises the previously recognized subspecies Agkistrodon piscivorus conanti .

Diagnosis: The Florida Cottonmouth ( A. conanti ) is diagnosed from the subspecies A. p. conanti . This species is a medium- to large-bodied semi-aquatic pit viper with an average adult size 76–122 cm and a maximum size of 189.2 cm ( Gloyd & Conant, 1990; Conant & Collins, 1991), with a ratio of tail to total length of 0.15–0.19 in males and 0.13–0.18 in females. There is a single anal plate, keeled dorsal scales and typically 25 midbody scale rows (range 23–27; Gloyd & Conant, 1990). Subcaudals range from 45 to 54 in males and from 41 to 49 in females, whereas ventral scales number 135–145 in males and 132–144 in females ( Gloyd & Conant, 1990). Supralabials and infralabials range from 6 to 10 (mode 8) and 9 to 12 (mode 10), respectively, and total postoculars + suboculars range from 2 to 4 (mode 3; Gloyd & Conant, 1990). A combination of geography and colour pattern distinguishes the Florida cottonmouth from related species. There are 11–16 dark cross-bands on an olive, brown or black background, which may become subdued in adults, whereas A. piscivorus generally has 10–17 cross-bands that often become indistinguishable from the ground colour in adults ( Gloyd & Conant, 1990). The head is typically brown with vertical stripes along the snout on the rostrals, prenasals, and first supralabials ( Gloyd & Conant, 1990). Dark stripes appear on the lower jaw extending from the mental to the first four or five infralabials ( Gloyd & Conant, 1990). A dark cheek stripe is present bordered above and below by pale stripes and often present in adults, although it is often indistinguishable from the ground colour in adult A. piscivorus ( Gloyd & Conant, 1990; Conant & Collins, 1991). The distribution of the Florida Cottonmouth extends from southern Florida to approximately Savannah, Georgia, and west to south-eastern Alabama ( Fig. 5B ), whereas the Northern Cottonmouth ranges in the USA from south-eastern Virginia to central Georgia, east of the Appalachian Mountains, north to southern Illinois and eastern Kansas. Hybridization between the Florida and Northern cottonmouth occurs in the mid-Atlantic coastal plains in southern North Carolina to the southern coastal plains in southeastern Louisiana and diagnosis may be difficult without additional morphological and molecular data for some individuals in this area.

Figures

Figure 5. The distribution of species within the Agkistrodon contortrix complex (A) and Agkistrodon piscivorus complex (B) inferred by Bayesian species delimitation. Putative hybrids zones are identified with cross-hatches. Distributions are adapted from Gloyd & Conant (1990) and the results from ecological niche modelling.