Clinal Variation and Its Taxonomic Consequences in the Common Tanzanian Forest Frog, Arthroleptis affinis
North-to-south clinal variation in morphology is described in Arthroleptis affinis of the Eastern Arc mountains of Tanzania. While northern populations are readily separable from other Arthroleptis species, southern populations are not. This complicates differential diagnosis. Despite this, it is concluded that in the present state of knowledge, it is more useful to include the clinal variation under the name A. affinis, rather than attempt to divide the species into groups that defy clear morphological definition.Abstract
Map of the Eastern Arc mountain chain of Tanzania, showing the range of Arthroleptis affinis divided into four blocks, and other Giant East African Arthroleptids. See text for explanation.
(A) The ratio head width/snout–urostyle length in Arthroleptis affinis, grouped into the four blocks of Fig. 1. (B) The ratio horizontal tympanum diameter/snout–urostyle length, grouped into the four blocks of Fig. 1. (C) The ratio horizontal tympanum diameter/head width, grouped into the four blocks of Fig. 1. (D) The ratio length inner metatarsal tubercle/snout–urostyle length, grouped into the four blocks of Fig. 1. (E) The ratio length inner metatarsal tubercle/head width, grouped into the four blocks of Fig. 1. (F) Sexual dimorphism in Block 1 populations; black denotes female specimens, gray denotes male specimens.
(A) The ratio head width/snout–urostyle length in females, grouped into the four blocks of Fig. 1. (B) The ratio horizontal tympanum diameter/snout–urostyle length in females, grouped into the four blocks of Fig. 1. (C) The ratio horizontal tympanum diameter/head width in females, grouped into the four blocks of Fig. 1. (D) The ratio length inner metatarsal tubercle/snout–urostyle length in females, grouped into the three blocks of Fig. 1. (E) The ratio length inner metatarsal tubercle/head width in females, grouped into the four blocks of Fig. 1. Type material of A. nikeae, A. tanneri, A. adolfifriederici, and available material of A. reichei is included for comparison. (F) Range of the ratio for digital discs against tubercle width; circles placed on ranges denote the value for type specimens.
Contributor Notes
Associate Editor: M. J. Lannoo.