Genetic Variability among Populations of Lutzomyia (Psathyromyia) shannoni (Dyar 1929) (Diptera: Psychodidae: Phlebotominae) in Colombia

Vol. 96(2): 189-196, February 2001

Estrella Cárdenas/⁺, Leonard E Munstermann*, Orlando Martínez**,
Darío Corredor**, Cristina Ferro

Laboratorio de Entomología, Instituto Nacional de Salud, Avenida Eldorado, Carrera 50, Zona Postal 6, Apartado Aéreo 80080, Bogotá DC, Colombia *Department of Epidemiology and Public Health, School of Medicine, Yale University, New Haven, CT, USA **Facultad de Agronomía,
Universidad Nacional de Colombia, Bogotá DC, Colombia

Polyacrylamide gel electrophoresis was used to elucidate genetic variation at 13 isozyme loci among forest populations of Lutzomyia shannoni from three widely separated locations in Colombia: Palambí (Nariño Department), Cimitarra (Santander Department) and Chinácota (Norte de Santander Department). These samples were compared with a laboratory colony originating from the Magdalena Valley in Central Colombia. The mean heterozygosity ranged from 16 to 22%, with 2.1 to 2.6 alleles detected per locus. Nei's genetic distances among populations were low, ranging from 0.011 to 0.049. The estimated number of migrants (Nm=3.8) based on Wright's F-Statistic, F_ST, indicated low levels of gene flow among Lu. shannoni forest populations. This low level of migration indicates that the spread of stomatitis virus occurs via infected host, not by infected insect. In the colony sample of 79 individuals, the Gpi locus was homozygotic (^0.62/_0.62) in all females and heterozygotic (^0.62/_0.72) in all males. Although this phenomenon is probably a consequence of colonization, it indicates that Gpi is linked to a sex determining locus.

Key words: sand flies - Lutzomyia shannoni - isozyme electrophoresis - genetic variability - dispersal gene flow - Colombia

Of the more than 350 species of New World phlebotomine sand flies, only the visceral leishmaniasis vector, Lutzomyia longipalpis, has been extensively examined in terms of its population genetic structure among local populations (Morrison et al. 1995, Munstermann et al. 1998, Mutebi et al. 1998), and over a broader geographic range (Mukhopadhyay et al. 1998, Lanzaro et al. 1998, Mutebi et al. 1998, 1999). The forest sand fly Lu. shannoni, is a zoophilic species that has an even greater geographical distribution in the Western Hemisphere, extending from the southeastern United States to northern Argentina. In Colombia, this species is widely distributed from sea level up to 1,300 m (Young 1979). It is a vector of vesicular stomatitis virus (VSV) (Comer et al. 1990, 1991) and can support the development of at least three species of Leishmania: Le. mexicana (Lawyer et al. 1987), Le. chagasi (Endris et al. 1982) and Le. panamensis (Ferro et al. unpublished). The biology of Lu. shannoni has been studied by Comer et al. (1994) and Memmott (1991, 1992) in field conditions and under laboratory conditions by Ferro et al. (1998) and Cárdenas et al. (1999). However, no information on population genetic structure for this phlebotomine is available. In the present study, baseline parameters of genetic variation and interpopulation migration rates were estimated and genetic diversity was compared at 13 isozyme loci among forest populations of Lu. shannoni from three widely separated locations in Colombia and compared with a laboratory colony originating from the Magdalena Valley in Central Colombia.

MATERIALS AND METHODS

RESULTS AND DISCUSSION

ACKNOWLEDGMENTS

To Marco Fidel Suarez, to personnel of the Secretaria de Salud of Norte de Santander Department, and to personnel of CIDEIN of Valle Department for their collaboration in field collections of Lutzomyia shannoni specimens.

REFERENCES

Fig. 1 | Fig. 2 | Fig. 3 | Table I | Table II | Table III | Table IV

This research was supported by the Colombian Instituto Nacional de Salud (Project No. 3100302 to CF of the Entomology Laboratory) and the United States National Institutes of Health (AI-34521 to LEM).

⁺Corresponding author. Fax: +57-1-315.7341. E-mail: ecardenas95@latinmail.com

Received 27 January 2000

Accepted 4 October 2000

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