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 : 521

AGKISTRODON LATICINCTUS ( GLOYD & CONANT, 1934)

Broad-banded Copperhead

Holotype: UMMZ75599 , collected by William A, Bevan and R. F. Harvey.

Type locality: Twenty-six miles northwest of San Antonio, TX.

Etymology: Specific epithet refers to colour pattern, derived from Latin latus and cinctus, translated as ‘side’ or ‘broad’ and ‘banded’, respectively.

Synonymy: This species comprises the previously recognized subspecies Agkistrodon contortrix laticinctus ( Gloyd & Conant, 1934) , Agkistrodon contortrix pictigaster ( Gloyd & Conant, 1943) and A. c. phaeogaster (in part; Gloyd, 1969).

Diagnosis: Combining characteristics for the subspecies A. c. laticinctus and A. c. pictigaster, we provide a diagnosis for A. laticinctus . The broad-banded copperhead ( A. laticinctus ) is a medium-sized pit viper with an average adult size of 56–76 cm and a maximum size of 95 cm ( Gloyd & Conant, 1990; Conant & Collins, 1991), with a ratio of tail to total length of 0.11–0.18 in males and 0.11–0.16 in females. There is a single anal plate, keeled dorsal scales, and typically 23 midbody scale rows (range 21–25; Gloyd & Conant, 1990). Subcaudals range from 38 to 62 in males and from 39 to 57 in females, whereas ventral scales number 138–155 with no variation between sexes ( Gloyd & Conant, 1990). Supralabials and infralabials range from 7 to 10 (mode 8) and 8 to 12 (mode 10), respectively, and total postoculars + suboculars range from 2 to 6 (mode 4; Gloyd & Conant, 1990). A combination of geography and colour pattern distinguishes the broadbanded copperhead from related species. There are 10– 18 brown to red cross-bands in males (10–21 in A. contortrix ) and 10–18 in females (11–20 in A. contortrix ) on a light to medium- to light-brown background. Cross-bands do not narrow at midbody ( Gloyd & Conant, 1990), whereas they generally narrow at the midbody in A. contortrix . Head coloration typically matches that of the cross-bands with a lighter cheek stripe ( Gloyd & Conant, 1990). The approximate distribution of the A. laticinctus includes western and central Texas, central Oklahoma, and eastern Kansas, whereas the range of A. contortrix extends from Connecticut to Florida along the Atlantic coast, west to include eastern Texas north through eastern Oklahoma into eastern Kansas ( Fig. 5A ). Hybridization between the broad-banded copperhead and the eastern copperhead occurs along an ecological transition zone from south eastern Texas north to eastern Kansas, defined by an increasing elevation, decreasing precipitation, and transition from mixed forest and cypress swamp to prairie grassland. Diagnosis may be difficult for some individuals in this area without additional morphological data ( Fig. 5A ).

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.