Phenotypic differentiation in love song traits among sibling species of the Lutzomyia longipalpis complex in Brazil

Abstract

Background: Brazilian populations of Lutzomyia longipalpis may constitute a complex of cryptic species, and this report investigates the distribution and number of potential sibling species. One of the main differences observed among Brazilian populations is the type of acoustic signal produced by males during copulation. These copulation song differences seem to be evolving faster than neutral molecular markers and have been suggested to contribute to insemination failure observed in crosses between these sibling species. In previous studies, two main types of copulation songs were found, burst-type and pulse-type. The latter type can, in turn, be further subdivided into five different patterns.

Methods: We recorded male song from 13 new populations of the L. longipalpis complex from Brazil and compared the songs with 12 already available.

Results: Out of these 25 populations, 16 produce burst-type and 9 produce pulse-type songs. We performed a principal component analysis in these two main groups separately and an additional discriminant analysis in the pulse-type group. The pulse-type populations showed a clear separation between the five known patterns with a high correspondence of individuals to their correct group, confirming the differentiation between them. The distinctiveness of the burst-type subgroups was much lower than that observed among the pulse-type groups and no clear population structure was observed. This suggests that the burst-type populations represent a single species.

Conclusion: Overall, our results are consistent with the existence in Brazil of at least six species of the L. longipalpis complex, one with a wide distribution comprising all the populations with burst-type songs, and five more closely related allopatric siblings with different pulse-type song patterns and more restricted distribution ranges.

Fig. 1

Examples of the song traces of all 6 patterns observed in Brazilian populations of L. longipalpis (see text for further details). The first five correspond to the different pulse-type patterns or subtypes and the last one to the burst-type

Fig. 2

Examples of song traces from pulse-type populations of L. longipalpis from the localities of Lassance, Pirenópolis and Palmas 1S. The figure shows ~1 s of song in each case. Two traces from the populations Lassance, Pirenópolis and Palmas 1S are shown to illustrate the variation in the P4 pattern

Fig. 3

Scatter-plots of the first 3 factors obtained in the Principal Component Analysis of the pulse-type populations. (a) shows the plot of the first 2 canonical functions, (b) shows the plot of the first and third canonical functions

Fig. 4

Scatter-plots of the first 3 canonical functions obtained in the discriminant analysis of the pulse-type populations. (a) shows the plot of the first 2 canonical functions, (b) shows the plot of the first and third canonical functions and (c) the plot of the second and third canonical functions. P5 was not included in c since it forms a clear cluster in (a) and (b) and it helps visualise the differences among the other 4 song types

Fig. 5

Examples of the song traces from the burst-type populations L. longipalpis from the localities of Afonso Cláudio, Aracajú, Palmas 2S, Ipanema, Barcarena, Cametá, Camará, Itamaracá, Passira and Nova Porteirinha. The figure shows ~1 s of song in each case

Fig. 6

Scatter-plots of the first 2 factors obtained in the Principal Component analysis of the burst-type populations

Fig. 7

Map of Brazil showing the approximate geographical localization of all L. longipalpis populations that had their male copulations songs analysed so far (see text for further details). The colours of the circles symbolize the song pattern found in each population. The lighter patch of similar colour in the background marks the hypothetical distribution area of each cryptic species