Alejandra S. Araki

Molecular and behavioral differentiation among Brazilian populations of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae).

Background Lutzomyia 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 Findings Using 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/Significance Our 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.

Analysis of the Copulatory Courtship Songs of Lutzomyia longipalpis in Six Populations from Brazil

Abstract The sand fly Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae: Phlebotominae), the main vector of Leishmania infantum in the Americas, is believed to be a species complex, although the status of different Brazilian populations is still somewhat unclear. Preliminary analysis of the acoustic signals that are produced during copulation by L. longipalpis males has suggested the existence of three sibling species in Brazil. In the current report, we analyze in more detail a number of parameters of the copulatory courtship songs of L. longipalpis males from four allopatric populations from different parts of the country (Marajó Island, Natal, Jacobina, and Lapinha Cave) and from two sympatric populations from the locality of Sobral, where two types of males can be differentiated by the number of pale spots (one or two pairs) found on the abdomen. We show that males from the localities of Natal, Marajó, and Sobral (two-spot morph) have very similar songs composed of successive bursts, which are modulated in frequency and amplitude. No significant differences were found in the song parameters of these three populations. In contrast, one-spot males from Sobral and males from Jacobina and Lapinha produce songs that are made of pulses but with distinct patterns for each population and significant differences in all song parameters studied. The results suggest that the L. longipalpis complex in Brazil is composed of four sibling species and that the differences in song patterns between the populations are consistent with the level of divergence found in the period gene.

Lovesongs and period gene polymorphisms indicate Lutzomyia cruzi (Mangabeira, 1938) as a sibling species of the Lutzomyia longipalpis (Lutz and Neiva, 1912) complex.

The sand fly Lutzomyia cruzi (Mangabeira, 1938) is implicated as a vector of American visceral leishmaniasis (AVL) in some areas of Brazil. Lutzomyia cruzi is closely related to Lutzomyia longipalpis s.l. (Lutz and Neiva, 1912) the main Latin American vector of AVL and a species complex. Although females of the two species are identical, the males can be distinguished by differences in the genitalia. Nevertheless, pheromone analysis shows that Lu. cruzi males produce 9-methyl-germacrene-B, which has also been found in a number of Latin American populations of Lu. longipalpis s.l. In addition, analysis of microsatellite loci shows that the level of divergence between Lu. cruzi and Lu. longipalpis s.l. is similar to that observed among the Lu. longipalpis s.l. sibling species. Here we present the lovesongs of Lu. cruzi males which are similar to the Burst-type songs produced by one of the Lu. longipalpis s.l. sibling species. We also present data on the molecular polymorphisms of the period gene of Lu. cruzi that indicate this species as another sibling within the Lu. longipalpis complex. The results highlight the importance of an integrative approach to understand the patterns of genetic and phenotypic divergence among very closely related vector species.

Multilocus analysis of divergence and introgression in sympatric and allopatric sibling species of the Lutzomyia longipalpis complex in Brazil.

Background Lutzomyia longipalpis, the main vector of visceral leishmaniasis in Latin America, is a complex of sibling species. In Brazil, a number of very closely related sibling species have been revealed by the analyses of copulation songs, sex pheromones and molecular markers. However, the level of divergence and gene flow between the sibling species remains unclear. Brazilian populations of this vector can be divided in two main groups: one producing Burst-type songs and the Cembrene-1 pheromone and a second more diverse group producing various Pulse song subtypes and different pheromones. Methodology/Principal Findings We analyzed 21 nuclear loci in two pairs of Brazilian populations: two sympatric populations from the Sobral locality (1S and 2S) in northeastern Brazil and two allopatric populations from the Lapinha and Pancas localities in southeastern Brazil. Pancas and Sobral 2S are populations of the Burst/Cembrene-1 species while Lapinha and Sobral 1S are two putative incipient species producing the same pheromone and similar Pulse song subtypes. The multilocus analysis strongly suggests the occurrence of gene flow during the divergence between the sibling species, with different levels of introgression between loci. Moreover, this differential introgression is asymmetrical, with estimated gene flow being higher in the direction of the Burst/Cembrene-1 species. Conclusions/Significance The results indicate that introgressive hybridization has been a crucial phenomenon in shaping the genome of the L. longipalpis complex. This has possible epidemiological implications and is particularly interesting considering the potential for increased introgression caused by man-made environmental changes and the current trend of leishmaniasis urbanization in Brazil.

Sex pheromone and period gene characterization of Lutzomyia longipalpis sensu lato (Lutz & Neiva) (Diptera: Psychodidae) from Posadas, Argentina.

Lutzomyia longipalpis s.l. is the primary vector of Leishmania (L.) infantum in the New World. In this study, male Lutzomyia longipalpis specimens from Posadas, Argentina were characterized for two polymorphic markers: the male sex pheromone and the period (per) gene. The male sex pheromone was identified as (S)-9-methylgermacrene-B, the same compound produced by Lu. longipalpis from Paraguay and many populations from Brazil. The analysis of per gene sequences revealed that the population from Argentina is significantly differentiated from previously studied Brazilian populations. Marker studies could contribute to the understanding of the distribution and spread of urban American visceral leishmaniasis, thus aiding in the design of regional surveillance and control strategies.

The current status of the Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) species complex

Lutzomyia longipalpis s.l. is a complex of sibling species and is the principal vector of American visceral leishmaniasis. The present review summarises the diversity of efforts that have been undertaken to elucidate the number of unnamed species in this species complex and the phylogenetic relationships among them. A wide variety of evidence, including chemical, behavioral and molecular traits, suggests very recent speciation events and complex population structure in this group. Although significant advances have been achieved to date, differential vector capacity and the correlation between structure of parasite and vector populations have yet to be elucidated. Furthermore, increased knowledge about recent epidemiological changes, such as urbanisation, is essential for pursuing effective strategies for sandfly control in the New World.

The Lutzomyia longipalpis complex: a brief natural history of aggregation-sex pheromone communication

In this paper we review the natural history of pheromone communication and the current diversity of aggregation-sex pheromones in the sand fly Lutzomyia longipalpis. This species complex is the main vector of Leishmania infantum, the agent of visceral leishmaniasis in the Americas. The identification of variation in pheromone chemotypes combined with molecular and sound analyses have all contributed to our understanding of the extent of divergence among cryptic members of this complex. The importance of chemical signals as pre-mating barriers and drivers of speciation is discussed. Moreover, the importance of aggregation-sex pheromones as sexually selected signals is highlighted with evidence from the literature suggesting their potential role in species and mate recognition as well as mate assessment. The distinct evolutionary forces possibly involved are briefly reviewed and discussed in the context of this intriguing insect.

Hybrid sterility in crosses between two Brazilian sibling species of the Anopheles albitarsis complex

BackgroundComplexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species.MethodsHybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.ResultsMale hybrids show very low insemination rates and nearly complete sterility, apparently due to abnormalities in their reproductive organs. Evidence of partial sterility among the hybrid females was also observed.ConclusionsOur data indicated that Anopheles albitarsis s.s. and Anopheles marajoara show a high level of postzygotic isolation with a strong hybrid male sterility. This result is consistent with the Haldane’s rule which states that in interspecific crosses the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

Variation in Mitochondrial Cytochrome c Oxidase I DNA Can Successfully Identify Culex (Melanoconion) pedroi (Diptera: Culicidae) and Culex (Melanoconion) ribeirensis (Diptera: Culicidae)

Abstract Culex (Melanoconion) pedroi Sirivanakarn & Belkin 1980 and Culex (Melanoconion) ribeirensis Forattini & Sallum 1985 are two morphologically very similar species of the Pedroi subgroup of mosquitoes in the Spissipes section of the subgenus Melanoconion of the genus Culex L. 1758. We carried out an analysis of the mitochondrial cytochrome c oxidase I (COI) DNA variation between these two species. The recent observation of sympatric coexistence in a forested area of Rio de Janeiro State (Brazil) triggered the need to validate these two species previously identified based on morphology. We concluded that the COI is a useful tool for identification of Cx. pedroi and Cx. ribeirensis.