Helmet Shape and Phylogeography of the Treehopper Membracis mexicana

SIMPLE SUMMARY: Membracis mexicana is a treehopper widely distributed in the neotropical region where it is a minor pest of some crops. In Mexico, it is found in at least four biogeographic provinces (abiotic subdivision of biogeographic realms where assemblages of biota share an evolutionary history), and few species of insects have such wide distributions. Field observations indicate that there are different forms of this species, but so far, how the different forms appear and how they are distributed have not been recorded. To test whether the distribution of morphological and genetic variation was consistent with the regionalization of the biogeographic provinces, we analyzed the morphological and genetic variation of this species sampling a total of 303 insects and conducted a geometric morphometric analysis from the body shape and phylogeographical analysis using five sequenced genes. We found three different morphotypes of these species and two genetic groups; this means that one of the genetic groups shows two forms. These findings show that M. mexicana is a very variable species geographically structured by the conformation of biogeographic provinces. ABSTRACT: Membracis mexicana (Hemiptera: Membracidae) is distributed in four biogeographic provinces of Mexico. Field observations indicate that there are different forms of this species, but the distribution of the phenotype and the genetic variation of this species have not been clarified. The aim of this study was to quantify the phenotypic and genetic variation of M. mexicana and determine whether the configuration of biogeographic provinces impacts the distribution of this variation. To achieve this, we analyzed 307 photographs using 19 landmarks and geometric morphometrics to quantify the phenotypic variation in helmets. We sequenced five molecular markers for 205 individuals to describe the phylogeographic pattern. As a result, we identified three morphological configurations of the helmet of M. mexicana and two genetic lineages. The morphotypes are (1) a large and wide helmet with small dorsal spots, (2) a small and narrow helmet with large dorsal spots, and (3) a small and narrow helmet with small spots. Genetic lineages are distributed in southeast and western Mexico. The western lineage corresponds to two helmet morphotypes (1 and 2) and the southeast lineage to morphotype 3. We found that the larger helmets correspond to the western lineage and are distributed in Trans-Mexican Volcanic Belt and Pacific lowlands provinces, whereas the smallest helmets correspond to the southeast lineage and are present in the Veracruzan and Yucatan Peninsula provinces.