Altitude and hillside orientation shapes the population structure of the Leishmania infantum vector Phlebotomus ariasi

Abstract

Despite their role in Leishmania transmission, little is known about the organization of sand fly populations in their environment. Here, we used 11 previously described microsatellite markers to investigate the population genetic structure of Phlebotomus ariasi, the main vector of Leishmania infantum in the region of Montpellier (South of France). From May to October 2011, we captured 1,253 Ph. ariasi specimens using sticky traps in 17 sites in the North of Montpellier along a 14-km transect, and recorded the relevant environmental data (e.g., altitude and hillside). Among the selected microsatellite markers, we removed five loci because of stutter artifacts, absence of polymorphism, or non-neutral evolution. Multiple regression analyses showed the influence of altitude and hillside (51% and 15%, respectively), and the absence of influence of geographic distance on the genetic data. The observed significant isolation by elevation suggested a population structure of Ph. ariasi organized in altitudinal ecotypes with substantial rates of migration and positive assortative mating. This organization has implications on sand fly ecology and pathogen transmission. Indeed, this structure might favor the global temporal and spatial stability of sand fly populations and the spread and increase of L. infantum cases in France. Our results highlight the necessity to consider sand fly populations at small scales to study their ecology and their impact on pathogens they transmit. Phlebotomus sand flies are vectors of medically important pathogens, such as Leishmania, the causative agent of leishmaniasis 1 , and arthropod-borne viruses (Toscana virus, Naples virus, and Sicilian virus) 2. Phlebotomus ariasi Tonnoir, 1921 is the predominant sand fly species in the French Cevennes region 3 , and one of the two proven vectors, with Phlebotomus perniciosus Newstead, 1911, of leishmaniasis, which is caused by Leishmania infantum in the South of France 4. Sand flies are abundant in suburban and rural environments and are often close to human and domestic animal populations 4,5. Phlebotomus ariasi is found resting in houses, animal sheds, caves and weep holes in walls, near roads, and in villages. This species has a wide geographic distribution, including many countries of the Western Mediterranean region, such as Algeria,

A simple procedure to detect, test for the presence of stuttering, and cure stuttered data with spreadsheet programs

“…Simulations were undertaken with EASYPOP (v. 2.0.1) (Balloux, 2001). We simulated random mating dioecious populations (pangamy), like what probably occurs in the wild for ticks (De Meeûs et al, 2021), Nematocera flies (Prudhomme, De Meeûs et al, 2020), Hemipteran bugs (Gomez-Palacio, Triana et al, 2013), or tsetse flies (Berté et al, 2019). We also simulated selfing monoecious populations, as flukes and water snails (Correa et al, 2017).…”

Asymptomatic Leishmania infantum infection in dogs and dog owners in an endemic area in southeast France

“…Recently, Prudhomme et al . demonstrated the presence of two distinct Phlebotomus ariasi sand flies (sylvatic and domestic), with distinct genetic structures affected by altitude and hillside [ 36 ]. A particular population of sand flies may have an influence on Leishmania spp.…”

New Microsatellite Markers for Genetic Studies on Sergentomyia schwetzi (Diptera: Psychodidae): A Suspected Vector of Leishmania infantum (Trypanosomatida: Trypanosomatidae) in the Canine Leishmaniasis Focus of Mont-Rolland, Senegal

“…Samples were prepared, dissected, mounted, and identified as previously described in Prudhomme et al (2020) .…”

“…Raw data were formatted for CREATE ( Coombs et al 2008 ) that allows their conversion for the different software programs used. Linkage disequilibrium (LD) between each locus pair was measured with the G -based test (10,000 permutations) ( Goudet et al 1996 , Prudhomme et al 2020 ).…”

“…Yet, a better knowledge of these vectors is needed to precisely understand Leishmania transmission. Although few full sand fly genome sequences are available, the microsatellite marker-based method still remains one of the best approaches to study their population structure ( Prudhomme et al 2020 ).…”