Phylogeny of crickets (Orthoptera: Ensifera: Gryllidae) with comparative studies on the evolution of acoustic communication

The orthopteran suborder Ensifera represents one of the best-studied systems of acoustic communication. Chapter 1 estimates phylogenetic relationships of Ensifera using parsimony and Bayesian likelihood analyses of 18S, 28S, and 16S rRNA sequences. Results are compared with earlier phylogenies and a matrix of morphological characters. Ensifera diverged early into two superfamilies Grylloidea and Tettigonioidea, which both contain representatives lacking acoustic structures. This caused some authors to question the homology of acoustic structures in Ensifera. Character evolution simulations using phylogeny demonstrate why parsimonious ancestral state reconstructions should not be used as primary tests of homology.; Many parallel losses of acoustic structures have occurred in the ensiferan family Gryllidae. Chapter 2 uses parsimony and Bayesian likelihood analyses of 18S and 16S rRNA to estimate phylogenetic relationships in this group, which are compared with phylogenies implied by phenetic studies. Phylogenetic tests of character evolution demonstrate that losses of acoustic structures are coupled with flightlessness and wing loss, implying that they should be studied in these contexts. It is proposed that acoustic structures and wings are lost simultaneously because they are adult characters with similar developmental constraints.; In Chapter 3, Felsenstein's independent contrasts method tests for character state correlations in adults predicted by developmental constraints on morphology. Spearman's rank correlations showed that adultlike acoustic structures are correlated with adultlike wings, and juvenilized acoustic structures are correlated with juvenilized wings. It is suggested that this has resulted from heterochrony (paedomorphosis), the simplest mechanism that could lead to such widespread homoplasy and phenotype correlation in gryllids.; Chapter 4 examines the evolution of apterous, nonacoustic crickets endemic to Madagascar, the Malgasiinae. Parsimony and Bayesian likelihood analyses estimate a phylogeny of 12 species of Malgasia using sequences for 16S rRNA and CO-I. The results imply a secondary radiation into epigean habitats from cavernicolous ancestors, and speciation by local habitat shifts. Felsenstein's independent contrasts showed that cave species have longer legs and cerci than epigean species. Parsimonious character state optimizations using phylogeny suggest that elongate appendages in Malgasia evolved after the invasion of caves and the reduction of eyes, consistent with the definition of adaptation and the hypothesis of sensory compensation.