Geographic Variation in the Emerald Treeboa, Corallus caninus (Squamata: Boidae)
The arboreal boa Corallus caninus is widely distributed across northern South America (the Guianas and Amazonia). We examined geographic variation based on examination of 192 specimens from throughout the range, and revised its taxonomy on the basis of quantitative and qualitative analyses of morphological characters (meristics, morphometrics, and color patterns). Based on the high number of lateral blotches on the body and the high number of scales across the snout, populations south of the Rio Amazonas and west of the Rio Negro are identified as a species (or, potentially, a species complex) separate from C. caninus, and the name Corallus batesii is resurrected for those populations. The distribution of Corallus caninus is restricted to the Guiana Shield (north of the Rio Amazonas and east of the Rio Negro). La boa arbórea Corallus caninus presenta una distribución amplia en el norte de América del Sur (las Guyanas y la Amazonia). Obtuvimos datos de la variación geográfica utilizando 192 especimenes procedentes de varias localidades a los largo de su distribución. Revisamos su taxonomía utilizando caracteres morfológicos cuantitativos y cualitativos (merísticos, morfometría y patrones de coloración). Las poblaciones distribuidas al sur del Río Amazonas y al occidente del Río Negro fueron identificadas como una especie aparte de C. caninus, esto basándonos en una alto número de manchas laterales del cuerpo y de escamas del hocico. Se resucitó el nombre Corallus batesii para estas poblaciones. La distribución de Corallus caninus queda restringida al escudo de las Guyanas (al norte de Río Amazonas y al oriente del Río Negro).Abstract
Resumen
Bivariate plot with 95% confidence regions (ellipses) for the first two axes derived from scores of discriminant size-free analysis for three a priori defined groups of Corallus caninus (A) and correlations of meristic characters with corresponding first discriminant functions (directional cosines) (B). Group 1 = populations north of the Rio Amazonas and east of the Rio Negro (i.e., C. caninus populations); Group 2 = populations south of the Rio Amazonas and east of the Rio Tapajós (C. batesii); Group 3 = populations south of the Rio Amazonas, west of the Rio Negro, and west of the Rio Tapajós (C. batesii). Variables represented in the directional cosines graph correspond respectively to: 1 = ADORS, 2 = MDORS, 3 = PDORS, 4 = VENT, 5 = SNOUT, 6 = LATBL, 7 = TRIMD, 8 = SVL.
Scales across the top of the snout at the level of the suture between the third and fourth supralabials. (A) Corallus batesii from Montalvo, Pastaza, Ecuador (USNM 204089); (B) C. caninus from Moengo, Marowijne, Suriname (USNM 64623).
Frequency plots of the polymorphic diagnostic characters for groups of Corallus caninus: (A) The number of scales across the snout at the level of the suture between the third and fourth supralabials; (B) the number of lateral blotches on the left side of the body. Group 1 = populations north of the Rio Amazonas and east of the Rio Negro (i.e., C. caninus populations); Group 2 = populations south of the Rio Amazonas and east of the Rio Tapajós (C. batesii); Group 3 = populations south of the Rio Amazonas, west of the Rio Negro, and west of the Rio Tapajós (C. batesii).
(A) Corallus batesii from Santa Cecilia, Sucumbios, Ecuador (KU 121833); (B) C. batesii from Ariquemes, Rondônia, Brazil; (C) C. cf. batesii from an unknown locality; (D) C. caninus from Santa Elena de Uairen, Bolivar, Venezuela.
Geographic distribution of Corallus caninus and Corallus batesii. Triangles = C. caninus, circles = C. batesii, square = recent record from the Río Magdalena valley.
Contributor Notes
Associate Editor: D. Kizirian.