The mantodean egg case: Evolutionary hypotheses on their functional diversity and its significance for praying mantid and systematics and phylogenetics (Insecta: Mantodea)

A distinct physiological feature of praying mantids is the formation of the egg case, a protein-based structure that provides mechanical support and protection to the eggs. Praying mantid egg cases exhibit extensive structural diversity that is taxon–specific; however, the nature of such variation has been seldom documented nor studied in a phylogenetic framework. In this study we investigate variation among praying mantid egg cases to: 1) test the hypothesis that structural variation in mantodean egg cases reflects phylogenetic relationships; and 2) generate hypotheses about the adaptive significance of the various egg case morphs. We selected a monophyletic lineage of Neotropical mantids whose members exhibit a wide range of life history strategies. Approximately 350 egg cases were subjected to comparative analyses and contrasted against a molecular Bayesian phylogeny that was constructed using a concatenated dataset of nine genes (12S rRNA, 16S rRNA, 18S rRNA, 28S rRNA, COI, COII, ND4, Wingless and Histone 3). Each egg case morph identified was found to correspond to a particular clade in the molecular phylogeny. This suggests that egg cases possess a suite of characters that are not only useful for taxon recognition, but also provide a novel and structurally conservative source of data to test current classifications at the family and subfamily levels, as well as for phylogenetic inference. We hypothesized that the various structural features of egg cases resulted from an evolutionary arm race, having evolved into multiple cryptic strategies to escape the attack of a wide range of natural enemies.