- Author: Kathy Keatley Garvey
The lecture, "Anthropogenic Forces Drive the Breakdown of Reproductive Isolation between Incipient Species of the African Malaria Mosquito," is from 12:10 to 1 p.m. in Room 122 of Briggs Hall. Plans are to record the lecture for later viewing on UCTV.
Lanzaro, who researches malaria vectors in Africa and Brazil says his area interest is in medical entomology with a focus on the genetics of vectors of human disease. He initiated his current work on the population genetics of malaria vectors in Africa in 1991 when he joined the Laboratory of Malaria Research at the National Institutes of Health and continues this work through today.
"A considerable part of our research program involves field work," he said. "Over the years we have worked in seven countries spanning sub-Saharan Africa." His Africa work is organized into three major research areas: (1) Genetics of complex behavioral phenotypes, host preference and adult resting behavior (2) Mutations in immune signaling pathway genes and mosquito susceptibility to malaria infection and (3) Speciation in anopheline mosquitoes.
"Just this year we have initiated a new research program focused on the genetics malaria vectors in Brazil," Lanzaro related. The Brazilian government supports the program, known as Brazil Science without Borders. The focus is on the population genetics and genomics of the mosquito Anoheles darlingi, the principal vector of malaria in Brazil.
The abstract of his talk on Nov. 13: "The M and S forms of Anopheles gambiae have been the subject of intense study by both malaria researchers and evolutionary biologists.The focus has centered on evaluating models of the evolution and maintenance of genetic divergence between the two forms in relation to speciation. The two forms occur in sympatry throughout west and central Africa. Hybrids are rarely found in nature and studies of reproductive isolation confirmed strong assortative mating with inter-form matings estimated at a frequency of ~1%. Progeny of laboratory crosses and backcrosses show no signs of reduced fitness, however, it is widely held that, in nature, some degree of ecologically dependent postzygotic isolation, in addition to assortative mating, contributes to divergence between the two forms. Comparative genomics studies have revealed divergence occurs at three discrete islands in genomes that are otherwise nearly identical. Two opposing models aimed at describing the evolution of M and S have been formulated. An 'islands of speciation' model proposes that diverged regions contain “speciation genes” that are maintained by selection in the face of gene flow. An alternative 'incidental island' model maintains that gene flow between M and S is effectively zero and that divergence islands are unrelated to speciation. A 'Divergence Island SNP' (DIS) assay was developed and used to explore the spatial and temporal distributions of hybrid genotypes. Results revealed that hybrid individuals occur at frequencies ranging between 5-97% in every population examined. A temporal analysis of DIS genotype frequencies spanning 20 years was conducted at a single site. This study revealed that assortative mating is unstable and periodically breaks down resulting in extensive hybridization. Results suggest that hybrids suffer a fitness disadvantage, but at least some hybrid genotypes are viable. Stable introgression of the 2L speciation island occurred at this site following a hybridization event. We present data suggesting that strong selection on a single gene within the 2L island is driving M/S introgression and that man-made changes to the environment is the source of this selection."
Lanzaro joined PMI in July 2006. He served as the director of the Center for Vectorborne Diseaes, UC Davis, from January 2006 through June 2007, and directed the UC Mosquito Research Program, headquartered in the UC Davis Department of Entomology, from June 2002 to 2008.
Prior his appointment at UC Davis, Lanzaro served on the faculty of Department of Pathology, University of Texas Medical Branch, Galveston, Texas, from August 1995 through May 2002, advancing from assistant and associate to full professor.
Lanzaro received his bachelor of science degree in biology/secondary education from Kansas State University, Manhattan, Kansas in 1972; his master's degree in entomology in 1978 from the Univeristy of Arizona, Tucson, and his doctorate in engomology in 1986 from the University of Florida.
The medical entomologist did post-doctoral work at three universities: from 1986 to 1988 in the Department of Entomology, Mississippi State University; from 1986 to 1988 in the Department of Entomology, Missisippi State University; and from 1988 to 1991 in the UC Davis Department of Entomology. He was a MacArthur Fellow in the Laboratory of Malaria Research, National Institutes of Health.