Trimeresurus pitvipers are a conspicuous component of most Asian reptilian faunas and in recent years have become a subject of intense interest to systematists, ecologists and herpetoculturalists. The following study reviews cryptic speciation and biogeography in three Trimeresurus species groups from the Indomalayan region.
The systematics of two frequently misidentified closely related species,
Trimeresurus hageni and T. sumatranus, are first investigated using multivariate
morphometrics. Two morphological forms are found to correspond to T. hageni in West Malaysia, Thailand, Singapore and Sumatra, and T. sumatranus in Borneo and west Sumatra. Geographic variation and diagnostic characters are discussed.
Following the collection of new material for the T. sumatranus complex, the
molecular and phenotypic evolution of the five species in this group is analysed
using mitochondrial DNA sequencing and multivariate morphometrics. A wellresolved phylogeny shows each species to represent a distinct lineage. Phenotypic differentiation within the group is congruent between the sexes but does not reflect phylogenetic history. An adaptive explanation for the observed pattern of differentiation is supported by independent contrasts analysis, and hypotheses concerning the functional significance of traits are proposed. Ecological convergence in traits used for classification is found to have important implications for species identification where taxa are distributed over varying environments.
Molecular, morphological and ecological species criteria are used to delimit species boundaries in the widespread T. popeiorum complex. A mitochondrial DNA phylogeny for the complex indicates two well-differentiated northern and southern clades. Multivariate analysis of morphological characters reveals a generally conserved pattern of geographical variation, with strongest differentiation between island populations. The current subspecific taxonomy of T. popeiorum is found to be inconsistent with the molecular, morphological and ecological divisions uncovered, and a conservative reorganisation of the group into three species is recommended.
The limitations of several pattern-based species criteria are discussed, and the
combined utility of molecular, morphological and ecological data is evaluated in
relation to delimiting species boundaries in organisms that are difficult to sample in large numbers.
Finally, mitochondrial gene sequences are used in combination with 4-nucleotide
extension AFLPs to infer systematic relationships and biogeographic history in the T. albolabris complex. A mitochondrial gene tree reveals four distinct clades, whose present distribution is closely linked to original patterns of vegetation cover.
Parallels between ordination and phylogenetic analysis of AFLP markers and the
mtDNA phylogeny support previous taxonomic revisions and provide further
resolution of systematic relationships within the complex. Congruence between the divisions recovered by AFLP and mtDNA analysis demonstrates the utility of 4-nucleotide extension AFLPs for generating systematic information within a complex of closely related pitviper species.