Diversity of sand flies (Diptera, Psychodidae) in southwest Iran with emphasis on synanthropy of Phlebotomus papatasi and Phlebotomus alexandri

•One of the factors for being high diversity of sand flies in plain area is due to more annual precipitation.•Synanthropic index was determined for the first time for P. papatasi and P. alexandri in different land-use categories in Iran.•Shannon–Weiner index, richness and evenness in semi-urban area of plain were more than other habitats.•Agricultural ecosystem of littoral area had the highest diversity of sand flies. Zoonotic Cutaneous Leishmaniasis (ZCL) is still a serious health problem in Iran. The objective of the study was to determine the differences in sand fly biodiversity in Shush (plain) and Khorramshahr (littoral) Counties, Khuzestan Province, southwest Iran. Sand flies were collected using sticky paper traps from urban, semi urban, agricultural and natural ecotypes. Alpha and beta diversity were calculated using Shannon–Weiner index and Jaccard's and Sorensen's coefficients, respectively. Synanthropic index was determined for the first time for Phlebotomus papatasi and Phlebotomus alexandri in different land use categories in Iran. Totally 11213 specimens, 68.47% in Shush and 31.53% in Khorramshahr, were collected. Eleven species of sand flies including, 2 of genus Phlebotomus and 9 of genus Sergentomyia were identified. Sergentomyia christophersi was found as a new record. Dominant species were P. papatasi and Sergentomyia sintoni. Shannon–Weiner index, richness and evenness in semi urban area of Shush County were more than other habitats. The analysis of α biodiversity showed that agricultural ecosystem of Khorramshahr County had the highest diversity due to maximal richness and diversity and also relatively high evenness. Comparison of similarity of the sand flies population composition between Shush and Khorramshahr indicated the maximum similarity between the urban area of Shush and the semi urban area of Khorramshahr (Sj=75% and Ss=86%). Synanthropic index of P. papatasi and P. alexandri were calculated to be −83.34 and −91.18, respectively in Shush County. Estimated synanthropic indices for P. papatasi and P. alexandri in three habitats (natural, semi urban and urban) of Khorramshahr County were −69.84 and −85.89, in the same order. The factors for having high diversity of sand flies in the plain area studied may be due to higher annual precipitation, the related land use and land cover. The changes on the composition of sand flies are perhaps due to human intervention in their natural habitats.