The effects of Pleistocene environmental fluctuations on the distribution and diversity of organisms in Southeast Asia are much less well known than in Europe and North America. In these regions, the combination of palaeoenvironmental reconstruction and inferences about population history from genetic data has been very powerful. In Southeast Asia, mosquitoes are good candidates for the genetic approach, with the added benefit that understanding the relative contributions of historical and current processes to population structure can inform management of vector species. Genetic variation among populations of Anopheles minimus was examined using 144 mtDNA COII sequences from 23 sites in China, Thailand and Vietnam. Haplotype diversity was high, with two distinct lineages that have a sequence divergence of over 2% and exhibit different geographical distributions. We compare alternative hypotheses concerning the origin of this pattern. The observed data deviate from the expectations based on a singlepanmictic population with or without growth, or a stable but spatially structured population. However, they can be readily accommodated by a model of past fragmentation into eastern and western refugia, followed by growth and range expansion. This is consistent with the palaeoenvironmental reconstructions currently available for the region.

Species of the Anopheles fluviatilis James and Anopheles minimus complexes (Diptera: Culicidae) are difficult to distinguish morphologically. Members of the two complexes have been confused and, consequently, their distributions and roles in malaria transmission are uncertain. We identified numerous mosquitoes from China, Thailand, Vietnam, India, Nepal, Pakistan and Iran by single-strand conformation polymorphism (SSCP) and/or sequencing, and analysed the variation in the 28S D3 region of ribosomal DNA for members of the Minimus Subgroup and also the internal transcribed spacer region 2 (ITS2) for members of the An. fluviatilis complex. The D3 region is highly conserved between taxa and therefore could serve as a standard for molecular diagnosis of the subgroup members. D3 sequence, bionomics and malaria transmission data provide further evidence that An. fluviatilis S in India is conspecific with An. minimus C in South-east Asia. An. fluviatilis T has three ITS2 haplotypes (designated T1, T2 and Y) and its distribution in India, Nepal, Pakistan and Iran is confirmed. An. fluviatilis U is well defined on cytogenetic grounds in Uttar Pradesh, India, but is very close to An. fluviatilis T and the two species may hybridize in some regions. Variant ITS2 sequences suggest the possible existence of two additional taxa within the An. fluviatilis complex, one in Iran and another in India, provisionally designated An. fluviatilis forms V and X, respectively. The distributions of members of the An. fluviatilis and An. minimus complexes in south-central Asia are summarized.

The origin of tropical forest diversity has been hotly debated for decades. Although specific mechanisms vary, many such explanations propose some vicariance in the distribution of species during glacial cycles and several have been supported by genetic evidence in Neotropical taxa. However, no consensus exists with regard to the extent or time frame of the vicariance events. Here, we analyse the cytochrome oxidase II mitochondrial gene of 250 Sabethes albiprivus B mosquitoes sampled from western Sao Paulo in Brazil. There was very low population structuring among collection sites (F ST ¼ 0.03, P ¼ 0.04). Historic demographic analyses and the contemporary geographic distribution of genetic diversity suggest that the populations sampled are not at demographic equilibrium. Three distinct mitochondrial clades were observed in the samples, one of which differed significantly in its geographic distribution relative to the other two within a small sampling area (B70 Â 35 km). This fact, supported by the inability of maximum likelihood analyses to achieve adequate fits to simple models for the population demography of the species, suggests a more complex history, possibly involving disjunct forest refugia. This hypothesis is supported by a genetic signal of recent population growth, which is expected if population sizes of this forest-obligate insect increased during the forest expansions that followed glacial periods. Although a time frame cannot be reliably inferred for the vicariance event leading to the three genetic clades, molecular clock estimates place this at B1 Myr before present.