Unraveling phallic complexities in scrub-lovin’ grasshoppers: Does shape matter? (Acrididae: Melanoplus: The Puer Group)

The scrub ecosystem of the southeastern U.S. is a wellspring of endemism in arthropods, like those in the grasshopper genus, Melanoplus (Orthoptera: Acrididae: Melanoplinae). The majority of the southeastern members of this genus belong  to the Puer Group (PG), comprised of 24 species with related morphology, which spans four neighboring states (Florida, Georgia, South Carolina, and North Carolina), contains many scrub endemics, and whose males are possessed of great variation in their genitalia (mainly between phallic complexes). These reasons, combined with the additional fact that they are all flightless, makes the PG an ideal candidate for examining the speciation process. One suspected speciation mechanism for these species is sexual selection by cryptic female choice in which the females of each species are driving the amazing evolution of the genitalia of their male counterparts in a manner still unknown to science. However, despite what is not known, it is possible to utilize a phylogenetic framework and landmark geometric morphometric analyses to examine the general evolution of PG male genitalia and elucidate the role that sexual selection is playing in the speciation of the PG. Avenues investigated were: 1) generally comparing the relative evolution of morphological traits across all utilized species, 2) specifically comparing the evolution of the same parts between sister species, and 3) examining the relative rate of the same parts compared to one another.