Complex population history of twoAnopheles dirusmosquito species in Southeast Asia suggests the influence of Pleistocene climate change rather than human‐mediated effects

Abstract

Anopheles dirus and Anopheles baimaii are closely related species which feed on primates, particularly humans, and transmit malaria in the tropical forests of mainland Southeast Asia. Here, we report an in‐depth phylogeographic picture based on 269 individuals from 21 populations from mainland Southeast Asia. Analysis of 1537 bp of mtDNA sequence revealed that the population history of A. baimaii is far more complex than previously thought. An old expansion (pre‐300 kyr BP) was inferred in northern India/Bangladesh with a wave of south‐eastwards expansion arriving at the Thai border (ca 135–173 kyr BP) followed by leptokurtic dispersal very recently (ca 16 kyr BP) into peninsular Thailand. The long and complex population history of these anthropophilic species suggests their expansions are not in response to the relatively recent (ca 40 kyr BP) human expansions in mainland Southeast Asia but, rather, fit well with our understanding of Pleistocene climatic change there.

Mitochondrial DNA variation in the malaria vector Anopheles minimus across China, Thailand and Vietnam: evolutionary hypothesis, population structure and population history

“…Signals of expansion from multiple forest species are most likely to be a response to a common factor. As we have suggested previously, this factor seems most likely to be the spread of forests from refugial areas following the onset of an interglacial period (Chen et al, 2004;Pramual et al, 2005;O'Loughlin et al, 2008). The divergence of Lineages A and B, which dates to B1 mya using the conventional calibration rate for animal mtDNA of 2% divergence per million years (Powell et al, 1986), has likely accumulated over multiple glacial cycles.…”

“…As the confidence intervals of these estimates overlap, the expansions could have occurred at the same time. Other forest insect species from Indochina show similarly dated genetic signals of expansion for mtDNA: A. dirus (O'Loughlin et al, 2008), Simulium tani blackflies (Pramual et al, 2005) and Anopheles jeyporiensis (Chen et al, 2004). Stone oaks in mainland (but not insular) Southeast Asia also have a star-like chloroplast DNA genealogy characteristic of demographic expansion (Cannon and Manos, 2003).…”

“…Both species are heavily dependent on primary forest habitat (O'Loughlin et al, 2008 and references therein). This, and the timing and geographic complexity of their population expansions, led to the suggestion that these expansions were in response to the post-glacial recovery and spread of tropical forests (O'Loughlin et al, 2008).…”

Evidence for Pleistocene Population Divergence and Expansion of Anopheles albimanus in Southern Central America

“…22 The discrepancy in allele frequencies may be attributed either to the mountain range that crosses Costa Rica and western Panama, which may act as a barrier to gene flow, or to population contraction in Panama caused by intense insecticide use. 22 Nonetheless, the analysis of only four populations in Costa Rica and Panama in the latter studies may have produced inaccurate results for the IBD analysis, and demographic history (e.g., stability of the population size) and natural selection (e.g., neutrality), which are known to influence inferences of population structure in Anopheles mosquitoes, 8,10 were not explored in these studies. Intensive chemical and physical larval control (e.g., source reduction) was carried out in Panama during and after the construction of the Panama Canal (1904)(1905)(1906)(1907)(1908)(1909)(1910)(1911)(1912)(1913)(1914).…”

“…In addition, such studies may provide key information on lineage divergence, discrete populations, and timing of demographic phenomena, all of which can influence the involvement of vectors in malaria transmission. [8][9][10] Anopheles albimanus is a malaria vector in the subgenus Nyssorhynchus with considerable ecological adaptability and broad, mostly coastal, geographic distribution in the Neotropics. 11 Generally, An.…”