Abstract
Background Lutzomyia umbratilis is an important Leishmania guyanensis vector in South America. Previous studies have suggested differences in the vector competence between L. umbratilis populations situated on opposite banks of the Amazonas and Negro Rivers in the central Amazonian Brazil region, likely indicating a species complex. However, few studies have been performed on these populations and the taxonomic status of L. umbratilis remains unclear.Methodology/Principal FindingsPhylogeographic structure was estimated for six L. umbratilis samples from the central Amazonian region in Brazil by analyzing mtDNA using 1181 bp of the COI gene to assess whether the populations on opposite banks of these rivers consist of incipient or distinct species. The genetic diversity was fairly high and the results revealed two distinct clades ( = lineages) with 1% sequence divergence. Clade I consisted of four samples from the left bank of the Amazonas and Negro Rivers, whereas clade II comprised two samples from the right bank of Negro River. No haplotypes were shared between samples of two clades. Samples within clades exhibited low to moderate genetic differentiation (F ST = −0.0390–0.1841), whereas samples between clades exhibited very high differentiation (F ST = 0.7100–0.8497) and fixed differences. These lineages have diverged approximately 0.22 Mya in the middle Pleistocene. Demographic expansion was detected for the lineages I and II approximately 30,448 and 15,859 years ago, respectively, in the late Pleistocene.Conclusions/SignificanceThe two genetic lineages may represent an advanced speciation stage suggestive of incipient or distinct species within L. umbratilis. These findings suggest that the Amazonas and Negro Rivers may be acting as effective barriers, thus preventing gene flow between populations on opposite sides. Such findings have important implications for epidemiological studies, especially those related to vector competence and anthropophily, and for vector control strategies. In addition, L. umbratilis represents an interesting example in speciation studies.
Highlights
In the last three decades, molecular genetic markers have been widely used for elucidating the population structure and evolutionary genetics in insect vectors, and these studies have contributed to differentiate members of cryptic species complexes, primarily in malaria [1,2,3], leishmaniasis [4,5], and Chagas [6,7,8] vectors
Conclusions/Significance: The two genetic lineages may represent an advanced speciation stage suggestive of incipient or distinct species within L. umbratilis. These findings suggest that the Amazonas and Negro Rivers may be acting as effective barriers, preventing gene flow between populations on opposite sides
One hundred and eleven L. umbratilis specimens were sequenced from six locations from the central Amazonian Brazil region using an 1181 bp fragment of the cytochrome oxidase subunit I (COI) gene (Table 1, Figure 1)
Summary
In the last three decades, molecular genetic markers have been widely used for elucidating the population structure and evolutionary genetics in insect vectors, and these studies have contributed to differentiate members of cryptic species complexes, primarily in malaria [1,2,3], leishmaniasis [4,5], and Chagas [6,7,8] vectors. In Brazil, L. umbratilis has been registered in the Amazonian region [11] and in the state of Pernambuco [13] from the northeastern region Populations of this species occupy extensive areas separated by geographic barriers, including the largest rivers, the Amazonas and Negro, in Amazonian Brazil. Sandflies have very limited dispersal capabilities, usually no more than 1 km [14,15], are abundant in peridomestic environments of rural communities and are distributed in discontinuous areas [16] Taken together, these characteristics suggest that L. umbratilis populations are more susceptible to evolving into differentiated populations, incipient species and, reproductively isolated species. Previous studies have suggested differences in the vector competence between L. umbratilis populations situated on opposite banks of the Amazonas and Negro Rivers in the central Amazonian Brazil region, likely indicating a species complex. Few studies have been performed on these populations and the taxonomic status of L. umbratilis remains unclear
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