Speciation and Population Structure in the Morphospecies Lutzomyia longipalpis (Lutz & Neiva) as Derived from the Mitochondrial ND4 Gene Sandra I. Uribe Soto,* Tovi Lehmann,† Edgar D. Rowton,‡ Iva ´n Darı´o Ve ´lez B.,* and CharlesH. Porter† ,1 * PECET, Universidad de Antioquia, Apartado 1226, Medellı´n, Colombia; †Division of Parasitic Diseases, National Center of Infectious Diseases, Centers for Disease Control and Prevention, Chamblee, Georgia 30341; and ‡Department of Entomology, Walter Reed Army Institute of Research, Washington, DC 20307 Received January 11, 2000; published online December 12, 2000 Recent studies have suggested that the phleboto- mine sand fly Lutzomyia longipalpis (Diptera: Psy- chodidae), the principal vector of visceral leishmani- asis in the Neotropics, may consist of several allopatric sibling species. Phylogenetic and popula- tion genetic analyses of nucleotide variation in a 618-bp fragment of the mitochondrial ND4 gene were carried out on specimens of Lu. longipalpis from sev- eral locations in Central and South America. The anal- yses were concordant with previous findings, indicat- ing that certain allopatric populations of Lu. longipalpis have become sufficiently differentiated as to represent sibling species. Phylogenetic analyses re- vealed deep genetic divisions between four clades rep- resented by specimens from northern South America, Brazil, Central America, and an isolated Colombian population. Strong differentiation also was observed between certain populations within the first two clades. Partitioning of genetic diversity within and between Central American populations did not show the presence of more than one species in the region. However, distance, even within the 70-km range of the Honduran collection sites, was found to have a re- markably strong effect on gene flow. The highly sub- divided population structure may be due to the patch- iness of their distribution. F ST values comparing a Guatemalan population with several Honduran popu- lations revealed a level of differentiation associated with a negligible rate of gene flow. © 2000 Academic Press INTRODUCTION The phlebotomine sand fly Lutzomyia longipalpis (Lutz & Neiva) 1912 has undoubtedly received more attention from researchers than any of the other New World species of Phlebotominae (Psychodidae) (a com- prehensive list of references is included in Young and Duncan, 1994). This is primarily due to its role as the principal vector of Leishmania chagasi Cunha & Cha- gas (L. donovani chagasi), a protozoan (order Kineto- plastida) that is the etiological agent of visceral leish- maniasis in Latin America. Children are most frequently affected by this potentially fatal disease; symptoms include fever, enlargement of the spleen and liver, anemia, and weight loss (Pearson and de Queiroz Sousa, 1995). Lu. longipalpis has a broad, but discon- tinuous, geographic distribution extending from cen- tral Mexico to northern Argentina and occurs primarily in dry tropical forest to semiarid habitats. However, it also occurs in the lower Amazon basin where it appears to be associated with well-drained soils, which are sub- ject to periodic flooding (Lainson et al., 1983; Quinnell and Dye, 1994). Throughout its range, Lu. longipalpis is often abundant in the peridomestic environment of rural communities where domestic animals often live in close proximity to humans. Several investigators beginning with Ward et al. (1983), who crossed sympatric Brazilian populations with apparent morphological differences, have ex- plored the possibility that Lu. longipalpis represents a complex of sibling species (Munstermann et al., 1998). Through an analysis of genetic variability of enzyme- coding loci and experimental crossing of laboratory colonies, Lanzaro et al. (1993) detected differences of significant magnitude among colonized specimens from Costa Rica, Colombia, and Brazil, indicating that they represented three distinct species. The extent to which colonization alters genetic composition, especially as related to enzyme loci, has been addressed by Mukho- padhyay et al. (1997). A recent comparison by Mukho- padhyay et al. (1998) of allele frequencies for enzyme loci in field populations from seven distinct regions of 1 To whom correspondence should be addressed at Division of Parasitic Diseases, Mailstop F-22, Centers for Disease Control and Prevention, 4770 Buford Highway NE, Chamblee, GA 30341-3724. Fax: (770) 488-4258. E-mail: chp1@cdc.gov. Molecular Phylogenetics and Evolution Vol. 18, No. 1, January, pp. 84 –93, 2001 doi:10.1006/mpev.2000.0863, available online at http://www.idealibrary.com on 1055-7903/00 $35.00 Copyright © 2000 by Academic Press All rights of reproduction in any form reserved. 84