Aposematic color polymorphism is a poor indicator of species boundaries in North American Paranthrene (Lepidoptera: Sesiidae) as evidenced by a multi-gene phylogeny.

Abstract

Color polymorphism among animal species can influence speciation. Factors such as natural and sexual selection, genetic drift and gene flow contribute to the maintenance of color polymorphism within the species or spur speciation. The evolutionary and ecological mechanisms for color polymorphism are taxon specific and only a few species have been studied. A phylogeny provides an evolutionary framework to understanding the association between color polymorphism and species. Paranthrene species are day flying aposematic moths that mimic wasps in both appearance and behavior. The genus has several polymorphic species and some color forms were originally described as species. Paranthrene presents the opportunity to test for an association between color polymorphism and species boundaries. We reconstructed a phylogeny using DNA sequence from COI, EF-1alpha, and Wingless genes from 67 specimens representing all North American Paranthrene species, nine color variants, and two outgroups. Parsimony and Bayesian analyses generally agreed in topology and support values. Paranthrene simulans (Grote, 1881) was polyphyletic, and monophyly of P. pellucida Greenfield and Karandinos, 1979 was not recovered. Paranthrene robiniae Hy. Edwards, 1880 was polyphyletic and genitalic and genetic differences among the three clades supported the recognition of two new pseudocryptic species, Paranthrene oasis Smith, Taft and, Cognato, new species and Paranthrene gilaensis Smith, Taft and, Cognato, new species. Paranthrene color variants did not overwhelming associate with species boundaries. Of the nine color forms we examined, only two were monophyletic, had DNA sequence divergence comparable to other species, and associated with species diagnostic morphology. It is likely that genetic drift and allopatric isolation explains the fixation of color variants with species. The mechanisms maintaining color polymorphisms within Paranthrene species will remain unknown until experimentation concerning the degree of aposematic protection in reference to wasp models is conducted.