Multilocus analysis of introgression between two sand fly vectors of leishmaniasis

Camila J Mazzoni,Renata Vdm Azevedo,Guido Barbujani,Alexandre A Peixoto,Alejandra S Araki,Gabriel Em Ferreira

doi:10.1186/1471-2148-8-141

Abstract

BackgroundThe phlebotomine sand flies (Diptera:Psychodidae) Lutzomyia (Nyssomyia) intermedia Lutz & Neiva 1912 and Lutzomyia (Nyssomyia) whitmani Antunes & Coutinho 1932 are two very closely related species and important vectors of American cutaneous leishmaniasis. Two single-locus studies have revealed evidence for introgression between the two species in both mitochondrial and nuclear genomes. These findings have prompted the development of a multilocus approach to investigate in more detail the genetic exchanges between the two species.ResultsWe analyzed ten nuclear loci using the "isolation with migration" model implemented in the IM program, finding evidence for introgression from L. intermedia towards L. whitmani in three loci. These results confirm that introgression is occurring between the two species and suggest variation in the effects of gene flow among the different regions of the genome.ConclusionThe demonstration that these two vectors are not fully reproductively isolated might have important epidemiological consequences as these species could be exchanging genes controlling aspects of their vectorial capacity.

Highlights

The phlebotomine sand flies (Diptera:Psychodidae) Lutzomyia (Nyssomyia) intermedia Lutz & Neiva 1912 and Lutzomyia (Nyssomyia) whitmani Antunes & Coutinho 1932 are two very closely related species and important vectors of American cutaneous leishmaniasis
Polymorphism, Recombination and Divergence Analyses Initially all sequences were checked for recombination, a necessary step for the IM analysis
Our aim was to detect the occurrence of gene flow using the multilocus data, and determine whether the evidence for introgression is exclusive to some loci

Summary

Introduction

The phlebotomine sand flies (Diptera:Psychodidae) Lutzomyia (Nyssomyia) intermedia Lutz & Neiva 1912 and Lutzomyia (Nyssomyia) whitmani Antunes & Coutinho 1932 are two very closely related species and important vectors of American cutaneous leishmaniasis. A number of studies have provided evidence that introgression can occur more in certain regions of the genome This is determined mainly by natural selection, which is expected to restrain gene flow at regions associated with species-specific adaptations [3]. Fonseca et al [4] have shown that hybrids between two different forms in the Culex pipiens complex, probably introduced in the United States at two different moments, may act as a bridge vector between birds and humans of the West Nile virus, contributing to the current epidemics. In another (page number not for citation purposes)

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