Date Published: January 27, 2009
Publisher: Public Library of Science
Author(s): Alejandra S. Araki, Felipe M. Vigoder, Luiz G. S. R. Bauzer, Gabriel E. M. Ferreira, Nataly A. Souza, Izeneide B. Araújo, James G. C. Hamilton, Reginaldo P. Brazil, Alexandre A. Peixoto, Adalgisa Caccone
Abstract: BackgroundLutzomyia longipalpis is the primary vector of American visceral leishmaniasis. There is strong evidence that L. longipalpis is a species complex, but until recently the existence of sibling species among Brazilian populations was considered a controversial issue. In addition, there is still no consensus regarding the number of species occurring in this complex.Methodology/Principal FindingsUsing period, a gene that controls circadian rhythms and affects interpulse interval periodicity of the male courtship songs in Drosophila melanogaster and close relatives, we analyzed the molecular polymorphism in a number of L. longipalpis samples from different regions in Brazil and compared the results with our previously published data using the same marker. We also studied the male copulation songs and pheromones from some of these populations. The results obtained so far suggest the existence of two main groups of populations in Brazil, one group representing a single species with males producing Burst-type copulation songs and cembrene-1 pheromones; and a second group that is more heterogeneous and probably represents a number of incipient species producing different combinations of Pulse-type songs and pheromones.Conclusions/SignificanceOur results reveal a high level of complexity in the divergence and gene-flow among Brazilian populations of the L. longipalpis species complex. This raises important questions concerning the epidemiological consequences of this incipient speciation process.
Partial Text: Cryptic speciation is an interesting and important issue to evolutionary biologists as organisms that are distinct in several ways can look the same even to specialist taxonomists, leading to false conclusions about their biology. Moreover, it also has practical implications for conservation management and in the identification of economically or medically important species . In addition, the study of cryptic speciation in blood-sucking insects can be epidemiologically relevant as sibling species might differ in their importance as disease vectors. One classical example is the Anopheles gambiae complex whose siblings differ in their host preference and other biological characteristics that together define very different vectorial capacities (reviewed in ).
There are a number of difficulties associated with the study of recently diverged species and populations in an incipient speciation process – such as the members of the L. longipalpis complex within Brazil . Although the role of sexual selection as a major cause of speciation still needs further support , it is likely that the rapid divergence of mating signals is particularly important in the evolution of reproductive isolation in cryptic species complexes . Therefore, in order to enhance our knowledge on the taxonomic status and geographic distribution of the different L. longipalpis siblings in Brazil, we combined a comparison of period gene sequences with an analysis of male copulation songs and sex pheromones, traits that probably have an important role in the reproductive isolation among these closely related species.