Population structure of Lucilia mexicana Macquart 1843 (Diptera: Calliphoridae) in Texas with a discussion of colonization and genetics

The heterogeneity of blow fly (Diptera: Calliphoridae) species and populations across heterogeneous environments is a vital concept of basic biology that has a dramatic impact in forensic entomology and the assumptions forensic entomologists infer. Accurate determination of the post mortem interval using the initial colonizing blow fly relies on what forensic entomologists know about species and population distributions, and the physiological differences those distributions may have. Texas is composed of multiple variable habitats and little is known about blow fly populations across and between these habitats. A collection of the initial colonizing blow fly species from each ecoregion in Texas was conducted to investigate whether species composition and population genetics were heterogeneous across environments with different biotic and abiotic factors. The survey revealed that within partially shaded, rural and riparian environments during the warmer months of the year Lucilia mexicana Macquart, 1843 was homogeneous across the different ecoregions of Texas. A population genetics survey on the initial colonizing species L. mexicana using microsatellites demonstrated a moderate to high amount of genetic differentiation (FST=.2019) between collected groups that could indicate the presence of local adaptations or population level behavior differences. Population clustering obtained from STRUCTURE and BAPS demonstrated genetic groupings that coincided with a north/south temperature gradient and xeric and mesic environments. The current study is the first comprehensive review of initial colonizing species to mammalian carcasses in Texas and the first study to demonstrate blow fly population heterogeneity across geographic ranges using microsatellites.