Comparison of calling songs in three allopatric populations of Endecous itatibensis (Orthoptera, Phalangopsinae)

Three isolated populations of the cricket Endecous itatibensis Rehn, 1918 had been analyzed to test the hypothesis of divergence in the calling song estridulation and to discuss its implications in the speciation process. The song registers were obtained from specimens in Corumbataí, Piraciacaba and Itatiba cities, state of São Paulo, Brazil. In the three analyzed populations, calling songs are composed by pairs of notes. Specimens from Corumbataí emit composed phrases with 3 to 18 pairs of notes, while those of Piracicaba and Itatiba have 1 to 3 pairs of notes. Inter- and intrapopulational variability in the frequencies of acoustic signals were detected. While recording the calling songs, other stridulations were registered, possibly from species of Orthoptera or Hemiptera. When the tapes were analyzed in the laboratory, it was verified that there was no overlap among the species' calling songs, in such a way that each species had their particular band of frequencies, avoiding interespecific acoustic competition.

Reproductive isolation between sympatric and allopatric Brazilian populations of Lutzomyia longipalpis s.l. (Diptera: Psychodidae)

Lutzomyia longipalpis s.l., the main vector of Leishmania chagasi in Latin America, is a species complex although the exact number of siblings is yet unknown. In Brazil, the siblings differ in male copulatory courtship songs and pheromones that most certainly act as pre-zygotic reproductive barriers. Here we analysed the reproductive isolation between three allopatric and two sympatric populations of Lu. longipalpis s.l. from Brazil. The results indicate a strong copulatory and pre-mating isolation between the three allopatric populations. In addition, the results also indicate a stronger pre-mating isolation between the two sympatric siblings than between the three allopatric ones, suggesting a role for reinforcement in the speciation of the Lu. longipalpis s.l. complex.

Copulatory courtship song in Lutzomyia migonei (Diptera: Psychodidae)

Lutzomyia migonei is a vector of leishmaniasis with a wide distribution in South America, which could favour population differentiation and speciation. Cryptic species of the Lutzomyia longipalpis complex, the widely distributed sand fly vector of visceral leishmaniasis in Latin America, have previously been shown to display distinct copulation songs. We found that Lu. migonei males also produce a song during copulation. This "lovesong" presents short trains (6-8 pulses) with an inter-pulse interval around 26 ms and is potentially involved in cryptic female choice and insemination success.

Acoustic communication in insect disease vectors

Acoustic signalling has been extensively studied in insect species, which has led to a better understanding of sexual communication, sexual selection and modes of speciation. The significance of acoustic signals for a blood-sucking insect was first reported in the XIX century by Christopher Johnston, studying the hearing organs of mosquitoes, but has received relatively little attention in other disease vectors until recently. Acoustic signals are often associated with mating behaviour and sexual selection and changes in signalling can lead to rapid evolutionary divergence and may ultimately contribute to the process of speciation. Songs can also have implications for the success of novel methods of disease control such as determining the mating competitiveness of modified insects used for mass-release control programs. Species-specific sound “signatures” may help identify incipient species within species complexes that may be of epidemiological significance, e.g. of higher vectorial capacity, thereby enabling the application of more focussed control measures to optimise the reduction of pathogen transmission. Although the study of acoustic communication in insect vectors has been relatively limited, this review of research demonstrates their value as models for understanding both the functional and evolutionary significance of acoustic communication in insects.