Molecular phylogenetics of the genus Neoconocephalus (orthoptera, tettigoniidae) and the evolution of temperate life histories

Abstract

Background: The katydid genus Neoconocephalus (25+ species) has a prominent acoustic communication system and occurs in large parts of the Neotropics and Nearctic. This group has been subject of numerous behavioral, physiological, and evolutionary studies of its acoustic communication system. Two distinct life histories occur in this group: The tropical life history incorporates multiple generations/year and direct egg development without environmental triggers. Temperate life history is characterized by overwintering in the egg stage, cold trigger of egg development, and one generation/year. This study reconstructs the phylogenetic relationships within the genus to (1) determine the evolutionary history of the temperate life history, and (2) to support comparative studies of evolutionary and physiological problems in this genus.

Methodology/principal findings: We used Amplified Fragment Length Polymorphisms (AFLP), and sequences of two nuclear loci and one mitochondrial locus to reconstruct phylogenetic relationships. The analysis included 17 ingroup and two outgroup species. AFLP and mitochondrial data provided resolution at the species level while the two nuclear loci revealed only deeper nodes. The data sets were combined in a super-matrix to estimate a total evidence tree. Seven of the temperate species form a monophyletic group; however, three more temperate species were placed as siblings of tropical species.

Conclusions/significance: Our analyses support the reliability of the current taxonomic treatment of the Neoconocephalus fauna of Caribbean, Central, and North America. Ancestral state reconstruction of life history traits was not conclusive, however at least four transitions between life histories occurred among our sample of species. The proposed phylogeny will strengthen conclusions from comparative work in this group.

Figure 1. Phylogeny of Neoconocephalus based on AFLP analysis.

Majority rule Bayesian AFLP phylogeny of 17 species of katydids. The species, as identified after , are indicated by color coding. Five species are represented by multiple geographic populations; CR = Costa Rica, FL = Florida, USA, NJ = New Jersey, USA, MO = Missouri, USA, PR = Puerto Rico, TN = Tennessee, USA, TT = Trinidad, and TX = Texas, USA. Nodal Support values, reported above nodes, are posterior probabilities in percent. Asterisks at the species names indicates temperate life history. The individuals included in this analysis are listed in the Table S1 in the sequence as they appear in this tree.

Figure 2. Phylogeny of Neoconocephalus based on nuclear genes.

Bayesian phylogeny of Neoconocephalus using partial nDNA sequences H3 (a) and ITS (b). Nodal support values given as posterior probabilities in percent; asterisk indicate 100%. The temperate clade and the N. maxillosus clade are indicated by labels ‘T’ and ‘M’, respectively. Branch lengths drawn to scale. The taxa included in these phylogenies are listed in Table S1. Asterisks at the species names indicates temperate life history. Species are indicated by colored lines.

Figure 3. Phylogeny of Neoconocephalus based on a mitochondrial gene.

Bayesian phylogeny of Neoconocephalus using partial COI mtDNA sequences. Nodal support values are posterior probabilities in percent; asterisk indicate 100%. The temperate clade and the N. maxillosus clade are indicated by labels ‘T’ and ‘M’, respectively. Branch lengths drawn to scale. The taxa included in this tree are listed in Table S1. Asterisks at the species names indicates temperate life history. Species are indicated by colored lines.

Figure 4. Phylogeny of Neoconocephalus based on the combined analysis of the nuclear and mitochondrial genes.

Bayesian phylogeny of Neoconocephalus using the combined H3, ITS and COI data sets. Nodal support values are given as posterior probabilities in percent; asterisk indicate 100%. The temperate clade and the N. maxillosus clade are indicated by labels ‘T’ and ‘M’, respectively. Branch lengths drawn to scale. The taxa included in this tree are listed in Table S1. Asterisks at the species names indicates temperate life history. Species are indicated by colored lines.

Figure 5.Total. evidence tree of Neoconocephalus.

Bayesian phylogeny of 17 Neoconocephalus species based on the combined analysis of the AFLP and gene trees given in Figures 1, 2, and 3. The phylogeny was pruned for visual simplification. Each tip of the pruned phylogeny represents a monophyletic group. Nodal support values are given as posterior probabilities in percent; asterisk indicate 100%. The temperate clade and the N. maxillosus clade are indicated by labels ‘T’ and ‘M’, respectively. Branch lengths are not drawn to scale. Asterisks at the species names indicates temperate life history.