Abstract
Lutzomyia longipalpis s.l. (Diptera: Psychodidae) is the principal vector of Leishmania infantum chagasi in the Americas, and constitutes a complex of species. Various studies have suggested an incipient speciation process based on behavioral isolation driven by the chemotype of male sexual pheromones. It is well known that natural barriers, such as mountains and rivers can directly influence population divergence in several organisms, including insects. In this work we investigated the potential role played by the Sao Francisco River in eastern Brazil in defining the current distribution of Lu. longipalpis s.l. Our studies were based on analyses of polymorphisms of the cytochrome b gene (cyt b) sequences from Lu. longipalpis s.l. available in public databases, and from additional field-caught individuals. Altogether, 9 distinct populations and 89 haplotypes were represented in the analyses. Lu. longipalpis s.l. populations were grouped according to their distribution in regards to the 10°S parallel: north of 10°S (<10°S); and south of 10°S (>10°S). Our results suggest that although no polymorphisms were fixed, moderate genetic divergences were observed between the groups analyzed (i.e., FST = 0.184; and Nm = 2.22), and were mostly driven by genetic drift. The population divergence time estimated between the sand fly groups was about 0.45 million years (MY), coinciding with the time of the change in the course of the Sao Francisco River, during the Mindel glaciation. Overall, the polymorphisms on the cyt b haplotypes and the current speciation process detected in Lu. longipalpis s.l. with regards to the distribution of male sexual pheromones suggest a role of the Sao Francisco River as a significant geographical barrier in this process.
Highlights
Lutzomyia longipalpis s.l. (Diptera: Psychodidae) is the vector of Leishmania infantum chagasi, the causative agent of visceral leishmaniasis (VL) in the New World [1,2,3]
Different chemotypes can be associated with different male copulation sounds or love songs generated by wing flapping: 3MαH is associated with the copulation songs Pulse songtype1; 9MGB is associated with either the Pulse songtype2 or the Pulse songtype3; cembrene-1 production is associated with Burstsong [15]
Our results suggest that the natural barrier represented by the Sao Francisco River in Lu. longipalpis s.l. has played a significant role in the development of sibling species of this sand fly
Summary
Lutzomyia longipalpis s.l. (Diptera: Psychodidae) is the vector of Leishmania infantum chagasi, the causative agent of visceral leishmaniasis (VL) in the New World [1,2,3]. (Diptera: Psychodidae) is the vector of Leishmania infantum chagasi, the causative agent of visceral leishmaniasis (VL) in the New World [1,2,3] This sand fly species has a wide, though discontinuous distribution ranging from southern Mexico to northern Argentina [4]. Recent studies have suggested the presence of sibling species in eastern Brazil [12,13]. These studies relied on the characterization of different male sexual pheromones, the "love songs" resulted from male wing vibration during courtship, as well as microsatellite markers and speciation genes. As many as five different chemotypes of sexual pheromones were characterized from Lu. longipalpis s.l. in Brazil [14]. No copulation songs have been associated with the production of pheromones 9MGB+ and cembrene-2 [3,14,15]
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