Pelage characteristicsnext section
Figure 1 shows pelage characteristics of the study animal and of other species of the genus Trachypithecus.
The general color of the study animal is grayish black with no silvering, and only slightly lighter ventrally (Fig. 1a). The tail is dark gray, slightly paler than the body. The root of the tail and the area around the ischial callosities are whitish. The long, upright crown hair forms a distinct crest. The face is gray with a violet tinge. The animal has the whitish eye-rings fully encircling the eyes and a depigmented area on the mouth typical of leaf monkeys of the T. obscurus group.
With the possible exception of some aspects of facial pigmentation, the study animal closely fits the original description of T. barbei (Blyth, 1847) and the coloration of the syntypes of T. barbei (as summarized in Groves, 2001). It differs from T. obscurus (Fig. 1b) in that the legs and the crown are not contrastingly paler than the body. It differs from T. phayrei in the absence of any brownish or buffy pelage. It further differs from T. p. phayrei in the absence of contrastingly light underparts, from T. p. crepusculus (Fig. 1c) in the presence of large white eyerings, and from both T. p. crepusculus and T. p. shanicus in its much darker overall coloration.
It differs from members of the T. cristatus group in exhibiting light face markings (although there can be a lighter gray area round the mouth and eyes in one species, T. germaini), and from T. germaini (Fig. 1d), the only species of the group occurring in Thailand, in the much darker overall coloration and the absence of long, light circumfacial hair.
In order to elucidate the phylogenetic position of the study animal, a 573 bp long fragment of the mitochondrial cytochrome b gene was sequenced from a number of langur species and phylogenetically analyzed.
Pairwise difference analyses within Trachypithecus revealed that T. barbei is different in 4.4 - 16.4% to other species of the genus (Table 2). The lowest differences of the study animal to other Trachypithecus species were detected to T. obscurus and T. p. phayrei (4.4 - 4.5%) and are even higher than those observed between the three members of the T. cristatus group (T. cristatus, T. germaini and T. a. auratus) (3.1 - 4.2%). The two analyzed subspecies of T. phayrei (T. p. phayrei and T. p. crepusculus) differ in 8.9% which is as unexpected as the extremely high difference detected between four species of Trachypithecus (T. geei, T. pileatus, T. johnii and T. vetulus) and all the other species of the group (14.8 - 18.8%). Interestingly, the latter four species differ only in 3.1 - 9.8% from the two members of the genus Semnopithecus (S. e. hector and S. e. priam). The two analyzed species of Presbytis (P. c. comata and P. m. mitrata) differ in 3.1%.
All three tree reconstruction methods revealed the same topology and differed only by bootstrap or puzzling support values (Figure 2). The analyzed langur species are divided in three significantly supported clades with one containing the two Presbytis species, one the two representatives of Semnopithecus as well as T. geei, T. pileatus, T. johnii and T. vetulus (in the following named Indian clade) and finally, a clade with all the remaining Trachypithecus species including the study animal. The relationships among the three clades however are not significantly supported (57 - 89%), although a Trachypithecus/Indian clade grouping is indicated. Within the Indian clade, the relationships among the species are not well resolved. There is strong support, however, for a S. e. priam/T. vetulus and a T. geei/T. pileatus clade. The Trachypithecus clade consists for three significantly supported major groups with unresolved relationships among them. One comprises all members of the T. cristatus group (T. cristatus, T. germaini and T. a. auratus), a second one T. p. crepusculus and T. f. francoisi, and a third one including T. obscurus, T. p. phayrei and T. barbei. The reconstructed trees allow no clear resolution of the relationships among the latter three species, however, although NJ and ML algorithms indicate a sister grouping of T. obscurus and T. p. phayrei.