Character State Reconstruction of Call Diversity in the Neoconocephalus Katydids Reveals High Levels of Convergence

Abstract

The katydid genus Neoconocephalus is characterized by high diversity of the acoustic communication system. Both male signals and female preferences have been thoroughly studied in the past. This study used Bayesian character state reconstruction to elucidate the evolutionary history of diverse call traits, based on an existing, well supported phylogenetic hypothesis. The most common male call pattern consisted of continuous calls comprising one fast pulse rate; this pattern is the likely ancestral state in this genus. Three lines of call divergence existed among the species of the genus. First, four species had significantly slower pulse rates. Second, five species had alternating pulse periods, resulting in a double pulse rhythm. Third, several species had discontinuous calls, when pulses were grouped into rhythmically repeated verses. Bayesian character state reconstruction revealed that the double-pulse pattern likely evolved convergently five times; the slow pulse rate also evolved four times independently. Discontinuous calls have evolved twice and occur in two clades; each of which contains reversals to the ancestral continuous calls. Pairwise phylogenetically independent contrast analyses among the three call traits found no significant correlations among the character states of the different traits, supporting the independent evolution of the three call traits.

Evolutionary diversification of the auditory organ sensilla in Neoconocephalus katydids (Orthoptera: Tettigoniidae) correlates with acoustic signal diversification over phylogenetic relatedness and life history

“…This was found in the GLM as well as the PCA. The double‐pulse pattern is a derived call pattern (Schul et al ., ; Frederick & Schul, ). As temporal selectivity in signal analysis occurs at neural levels beyond the sensory periphery (Pollack, ; Stumpner & Nowotny, ; Hedwig & Stumpner, ), this finding is surprising.…”

“…(), and Frederick & Schul (). Following Frederick & Schul (), pulse rates < 100 Hz are classified as slow pulse rates, and pulse rates > 100 Hz as fast. N. triops and N. ensiger are here coded as species with discontinuous calls.…”

“…N. triops and N. ensiger are here coded as species with discontinuous calls. For N. ensiger , the homology of call elements to continuous and discontinuous callers is not established (Frederick & Schul, ), but N. ensiger is classified as discontinuous as the calls have gaps > 30 ms (Greenfield, ). Neoconocephalus triops shows plasticity in male call patterns with discontinuous calls in the summer generation males but continuous calls in the winter generation males in extreme environments (Whitesell & Walker, ); clearly, the derived discontinuous call pattern is present in this species.…”

“…Several lines of diversification of the temporal call parameters have accompanied speciation. The ancestral call pattern was continuous and consisted of single pulses in fast repetition (Schul et al ., ; Frederick & Schul, ). Signals have independently diverged to discontinuous calls (with pulses grouped into chirps or verses), repeatedly changed from a single‐pulsed pattern to double‐pulsed patterns (with alternating pulse periods), or to a very slow pulse rate (Greenfield, ; Bush & Schul, ; Schul et al ., ; Frederick & Schul, ) (Fig.…”

What determines the number of auditory sensilla in the tympanal hearing organs of Tettigoniidae? Perspectives from comparative neuroanatomy and evolutionary forces

“…During the evolutionary radiation of the group, the call patterns diversified repeatedly into discontinuous calls, slow repetition rates, and/or double pulses (Schul et al 2014). The evolutionary diversification is highlighted e.g., by the repeated evolution of double-pulsed calls (Schul et al 2014, Frederick andSchul 2016). Studying the CA anatomy of nine species representing different taxonomic groups, life histories, call patterns, and call center frequencies, similar averages from 32-35 sensilla between the species were documented (Strauß et al 2017).…”