Infection, Genetics and Evolution 2 (2002) 121–128 Wing shape divergence between Rhodnius prolixus from Cojedes (Venezuela) and Rhodnius robustus from Mérida (Venezuela) J. Villegas a , M.D. Feliciangeli b , J.P. Dujardin c,∗ a Instituto de Altos Estudios “Dr. Arnoldo Gabaldon” (EMSA), Maracay, Venezuela b Universidad de Carabobo, BIOMED, Núcleo Aragua, Maracay, Venezuela c Institut de Recherches pour le Développement (IRD), Unité Mixte de Recherche (UMR) Centre National de Recherche Scientifique (CNRS), Institut de Recherches pour le Développement (IRD) CNRS-IRD 9926, CDC, 4770 Buford Hwy, 30341 Chamblee, GA, USA Received 13 October 2001; received in revised form 15 July 2002; accepted 29 August 2002 Abstract The existence of Rhodnius robustus as a species distinct from Rhodnius prolixus has long been the main epidemiological question about Chagas disease transmission in Venezuela and surrounding countries. These two taxa are morphologically and genetically very similar, but only R. prolixus is assumed to colonize houses and transmit Chagas disease to humans. R. robustus is assumed to be an exclusively sylvatic species, restricted to palm trees. If robustus and prolixus are actually the same species, the theoretical possibility exists of sylvatic specimens invading houses, even after insecticide application, and a control strategy similar to that of the successful Southern Cone Initiative against Triatoma infestans would be difficult to consider. Since no valid alternative control strategy exists, the answer to this biological question could be decisive about the future of vector control in this region. Although we believe genetic techniques are best suited to define species boundaries, we present here an example of the relevance of modern morphometrics in dealing with such an issue. Using both traditional and geometric morphometrics, we compared the wing size and shape in both sexes of these two taxa reared in the same laboratory for one generation. R. robustus specimens were collected from palm trees in the state of Mérida (Venezuela), and R. prolixus were collected from houses in the state of Cojedes (Venezuela). Our study provided no argument to question their specific status. Even after one generation of living in the same laboratory conditions, the two lines showed clear size differences, divergent allometric trends, and significant allometry-free differences in shape. These results suggest that R. robustus (Mérida, Venezuela) and R. prolixus (Cojedes, Venezuela) are distinct evolutionary units. Due to the epidemiological importance of this question, further studies in other geographic areas of Venezuela are required to accurately define the relationships of R. robustus and R. prolixus. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Rhodnius robustus; Rhodnius prolixus; Chagas disease transmission; Morphometrics 1. Introduction Rhodnius prolixus Stal (Hemiptera, Reduviidae, Triatom- inae) is one of the main Chagas disease vectors in Latin America. It is recognized as a domestic and peridomestic species, and most laboratory isolates derive from collec- tions from houses and/or chicken coops. However, sylvatic populations mainly in palm tree crowns–have been reported in parts of Venezuela since the work of Gamboa (1962). Palm tree crowns in these regions are also considered the main habitat of morphologically similar Rhodnius robustus Larousse, with the two species distinguished only by the lighter colored tibia of the older nymphs and minor differ- ∗ Corresponding author. Tel.: +1-7704-884-939; fax: +1-7704-488-4258. E-mail address: jdujardin@cdc.gov (J.P. Dujardin). ences in the basal plate struts of the male genitalia (Lent and Wygodzinsky, 1979). Isoenzyme studies found no consistent differences be- tween these two species, and no reproductive isolation was apparent in laboratory crosses (Harry et al., 1992a,b; Harry, 1993; Barrett, 1996; Solano et al., 1996), so that the specific status of robustus as a distinct taxon has been questioned (Harry, 1993; Barrett, 1996). However, recent mtDNA sequence data do indicate differences between in- dividuals from houses (defined as prolixus) and individuals from palm-trees (defined as robustus)(Lyman et al., 1999; Monteiro et al., 2000), and the domestic populations show different salivary protein profiles compared to morphologi- cally similar populations from palm trees in northern Brazil (Soares et al., 1998). The status of these two entities is of epidemiological im- portance because the domestic populations of R. prolixus are 1567-1348/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S1567-1348(02)00095-3