A single genealogical lineage from the Sonoran Desert and the Mexican Pacific Coast explains the haplotype distribution of Trichobaris compacta

The weevil Trichobaris compacta occurs in southwest USA where it uses Datura wrightii as host plant and to oviposit into its fruits. Previously, we showed that T. compacta can use 4 other Datura species as host plants also, but the mitochondrial lineages of T. compacta do not appear to be specifically associated to any Datura species. Thus, given that T. compacta is distributed from the southwest USA up to the Tehuantepec Isthmus in the Pacific coast ranges of Mexico, we aimed to determine how the genetic variation of T. compacta is distributed along the geographical space. To determine how geography has shaped the genetic population structure of T. compacta we used a 663-bp region of the COI gene in a sample of 232 individuals from 29 different localities. We detected 49 haplotypes, one of which is widely distributed. The un-rooted haplotype network and phylogeny showed that T. compacta integrates one single lineage. Also, the population genetic structure of T. compacta is made up of the admixture of 3 groups, 2 of them slightly associated geographically to the Colorado River basin. No other apparent geographic barrier to gene flow was identified despite weevils from southwest North America use D. wrightii and D. discolor as host plants, in the Pacific coasts of Mexico T. compacta uses D. reburra and D. discolor as host plants, whereas in southern Mexico it uses D. inoxia, D. pruinosa and D. discolor.

Automated summary

The weevil Trichobaris compacta is found in the southwest USA and up to the Tehuantepec Isthmus in Mexico, using various Datura species as host plants. Genetic analysis revealed that there is one main lineage for T. compacta, with its population structure consisting of the admixture of 3 groups, 2 of which are geographically associated with the Colorado River basin. Despite using different host plants in different regions, there is no clear geographic barrier to gene flow for T. compacta.