Phylogeny of the grassland leafhopper genus Flexamia (Homoptera: Cicadellidae) based on mitochondrial DNA sequences

A multi-gene phylogenetic analysis of the leafhopper subfamily Typhlocybinae (Hemiptera: Cicadellidae) challenges the traditional view of the evolution of wing venation

Genera of the diverse leafhopper subfamily Typhlocybinae have traditionally been classified into tribes primarily based on characters of the wing venation and an intuitive phylogeny of this group was previously proposed based on the hypothetical pattern of wing vein evolution. Some recent authors suggested that wing vein characters are not always reliable but few attempts have been made to examine the status and relationships of typhlocybine tribes using rigorous phylogenetic analyses. Phylogenetic analysis of a dataset comprising DNA sequences from five gene regions (H3, H2A, 28S rDNA D2, 16S rDNA, and COI with a total length of 2413 bps) and 61 species representing six previously recognized tribes of Typhlocybinae provides strong support for the monophyly of the subfamily and five of the previously recognized tribes. Most branches received moderate to strong maximum likelihood bootstrap support. The following intertribal relationships were recovered: (Alebrini + Empoascini) + ((Dikraneurini + Erythroneurini) + Typhlocybini). Maximum likelihood analysis recovered Zyginellini (treated as a separate tribe by some authors) as sister to Typhlocybini with low branch support, but the former tribe was derived from within the latter in Bayesian analysis of the same dataset and relationships within Typhlocybini (sensu lato) were generally poorly resolved in both analyses. The relationship of Typhlocybini to other tribes is also unstable, suggesting that more data are needed to resolve the position of this tribe with confidence. Parts of the phylogeny receiving strong support in both analyses contradict the traditional view that Alebrini, the only tribe retaining an appendix in the forewing, is the earliest diverging lineage and possibly gave rise to the other tribes. Ancestral state reconstructions indicate that characters of the wing venation traditionally used for diagnosing typhlocybine tribes are generally conservative but exhibit some homoplasy and may not, by themselves, be reliable for recognizing monophyletic groups within this subfamily.

Structural features and phylogenetic implications of Cicadellidae subfamily and two new mitogenomes leafhoppers

Complete mitochondrial genome sequences facilitate species identification and analyses of phylogenetic relationships. However, the available data are limited to the diverse and widespread insect family Cicadellidae. This study analyzes and summarizes the complete mitochondrial genome structure characteristics of 11 leafhopper subfamilies and two newly sequenced Typhlocybinae species, Empoascanara wengangensis and E. gracilis. Moreover, using 13PCGs and rRNA data to analyze the nucleotide diversity, evolution rate, and the phylogenetic relationship between the subfamilies of 56 species, verifying the taxonomic status analysis of E. wengangensis and E. gracilis. The analysis results show that the genome structures of the subfamilies and the newly sequenced two species are very similar, and the size of the CR region is significantly related to the repeat unit. However, in the entire AT-skews and CG-skews, the AT-skews of other subfamilies are all positive, and CG-skews are negative, while Empoascini of Typhlocybinae and Ledrinae are the opposite. Furthermore, among 13PCGs, the AT-skews of 13 species are all negative while CG-skews are positive, which from Empoascini in Typhlocybinae, Idiocerinae, Cicadellinae, Ledrinae, and Evacanthinae. Phylogenetic analysis shows that ML and PB analysis produce almost consistent topologies between different data sets and models, and some relationships are highly supported and remain unchanged. Mileewinae is a monophyletic group and is a sister group with Typhlocybinae, and the sister group of Evacanthinae is Ledrinae + Cicadellinae. Phylogenetic analysis grouped the two newly sequenced species with other species of Typhlocybinae, which was separated from other subfamilies, and all Erythroneurini insects gathered together. However, E. gracilis grouped into a single group, not grouped with species of the same genus (Empoascanara). This result does not match the traditional classification, and other nuclear genes or transcriptome genes may be needed to verify the result. Nucleotide diversity analysis shows that nad4 and nad5 may be evaluated as potential DNA markers defining the Cicadellidae insect species.

Phylogeny and revision of the Oriental leafhopper genus Amritodus (Hemiptera: Cicadellidae: Idiocerini)

The phylogeny of the Oriental leafhopper genus Amritodus is reconstructed, for the first time, based on 47 discrete morphological characters and DNA sequence data from one nuclear and two mitochondrial genes. The phylogenetic results show that Amritodus is not monophyletic, and its concept is narrowed here to include four species: Amritodus atkinsoni, Amritodus brevis, Amritodus brevistylus and Amritodus saeedi. The phylogenetic results support establishment of a new genus, Paramritodus gen. nov., with three new species,Paramritodus triangulus sp. nov. (type species), Paramritodus introflexus sp. nov., Paramritodus spatiosus sp. nov. and three species previously included in Amritodus: Paramritodus pistacious comb. nov., Paramritodus flavocapitatus comb. nov. and Paramritodus podocarpus comb. nov. In addition, Amritodus flavoscutatus is transferred from Amritodus to Hyalinocerus as Hyalinocerus flavoscutatus comb. nov. Keys to species of Amritodus and Paramritodus are provided.

Patterns of genetic differentiation among populations of Amrasca biguttula biguttula (Shiraki) (Cicadellidae: Hemiptera)

Cotton leafhopper, Amrasca biguttula biguttula (Shiraki), a serious sucking insect pest of cotton and vegetables is present throughout South and Southeast Asia. Genetic differentiation within A. biguttula biguttula populations collected from 16 cotton growing areas of Punjab, Pakistan, was examined by sequencing the barcode region of the mitochondrial cytochrome oxidase subunit 1 (COI) gene. The dendrogram obtained by neighbour joining analysis of COI sequences confirmed the presence of single species of cotton leafhopper. The overall average pairwise divergence was 0.01. Very little variation was found among populations from cotton growing areas of Punjab, Pakistan and these were most similar to populations from North India. South Indian populations were grouped together and were generally more divergent. Extensive migration of this pest species among cotton-growing areas in the Indian subcontinent may hinder genetic diversification of cotton leafhopper. Four Pakistani samples of cotton leafhopper tested positive for Wolbachia infection but were not clearly differentiated from non-Wolbachia infected samples, suggesting that Wolbachia did not cause reproductive incompatibilities.

Mitochondria COI-based genetic diversity of the cotton leafhopper Amrasca biguttula biguttula (Ishida) populations from India

Amrasca biguttula biguttula (Ishida), the cotton leafhopper, is a polyphagous insect pest of Asia and Southeast Asian countries. We sequenced a mitochondrial COI gene fragment from 67 individuals of cotton leafhopper collected from 7 major cotton growing states of North, Central, and South India. Genetic divergence analysis of leaf hopper population across India confirmed the presence of single species. Thirty haplotypes, in total, were determined across different regions of India. While population from North India was dominated by single haplotype, the south and central Indian populations show dispersion of different haplotypes across the region. The neutrality test rejection for the north Indian population also suggests population expansion. The genetic differentiation and gene flow analysis together confirmed the phylogeographic structure of the A. biguttula biguttula Ishida as isolated by distance.

In the shadow of a megalopolis, a new Flexamia from a threatened grass species in the New Jersey Pine Barrens (Hemiptera, Cicadellidae, Deltocephalinae, Paralimnini)

A previously unknown species of the North American leafhopper genus Flexamia, Flexamiawhitcombisp. n., is described from pinebarren smokegrass (Muhlenbergiatorreyana (Schult.) Hitchc.), a state-listed threatened grass in the New Jersey Pine Barrens. The serrata species group, to which it belongs, is redefined and a key to the species of the group is provided. This is the first reported insect association with Muhlenbergiatorreyana.

Mitochondrial COI and 16sRNA evidence for a single species hypothesis of E. vitis, J. formosana and E. onukii in East Asia

Tea green leafhopper is one of the most damaging tea pests in main tea production regions of East Asia. For lack of recognized morphological characters, the dominant species of tea green leafhoppers in Mainland China, Taiwan and Japan have always been named as Empoasca vitis Göthe, Jacobiasca formosana Paoli and Empoasca onukii MATSUDA, respectively. Furthermore, nothing is known about the genetic relationships among them. In this study, we collected six populations from Mainland China, four populations from Japan and one population from Taiwan, and examined the genetic distances in the COI and 16sRNA regions of mtDNA among them. The results showed that the genetic distances based on single gene or the combined sequences among eleven leafhopper populations were 0.3–1.2%, which were all less than the species boundary of 2%. Moreover, there were at least two haplotypes shared by two distinct populations from different regions. The phylogenetic analysis based on single gene or combined sets also supported that tea green leafhoppers from Mainland China, Taiwan and Japan were closely related to each other, and there were at least two specimens from different regions clustered ahead of those from the same region. Therefore, we propose that the view of recognizing the dominant species of tea green leafhoppers in three adjacent tea production regions of East Asia as different species is unreliable or questionable and suggest that they are a single species.

Prehistorical climate change increased diversification of a group of butterflies

Satyrinae butterflies (Lepidoptera: Nymphalidae) and grasses (Poaceae) are very diverse and distributed worldwide. Most Satyrinae use grasses as host plants, but the temporal scale of this tight association is not known. Here, we present a phylogenetic study of Satyrinae butterflies and related groups, based on 5.1 kilobases from six gene regions and 238 morphological characters for all major lineages in the 'satyrine clade'. Estimates of divergence times calibrated using a fossil from the Late Oligocene indicate that the species-rich tribe Satyrini diversified to its current 2200 species simultaneously with the expansion and radiation of grasses during the dramatic cooling and drying up of the Earth in the Oligocene. We suggest that the adaptive radiation of grass feeders in Satyrini has been facilitated by the ubiquitousness of grasses since 25Myr ago, which was triggered by a change in global climate.

Molecular phylogenetic analysis of the dragonfly genera Libellula, Ladona, and Plathemis (Odonata: Libellulidae) based on mitochondrial cytochrome oxidase I and 16S rRNA sequence data

Molecular phylogenetic relationships among members of the odonate genus Libellula (Odonata: Anisoptera: Libellulidae) were examined using 735 bp of mitochondrial COI and 416 bp of 16S ribosomal RNA gene sequences. Considerable debate exists over several relationships within Libellula, as well over the status of two putative genera often placed as subgenera within Libellula: Ladona and Plathemis. Parsimony and maximum-likelihood analyses of the separate and combined data sets indicate that Plathemis is basal and monophyletic and that Ladona is the sister clade to the remainder of Libellula sensu stricto (s.s.) (all species within the genus Libellula, excluding Plathemis and Ladona). Moreover, two European taxa, Libellula fulva and L. depressa, were found to occupy a sister group relationship within the Ladona clade. Relationships within Libellula s.s. are less well resolved. However, monophyletic lineages within the genus are largely consistent with morphologically based subgeneric classifications. Although tree topologies from each analysis differed in some details, the differences were in no case statistically significant. The analysis of the combined COI and 16S data yielded trees with overall stronger support than analyses of either gene alone. Several analyses failed to support the monophyly of Libellula sensu lato due to the inclusion of one or more outgroup species. However, statistical comparisons of topologies produced by unconstrained analyses and analyses in which the monophyly of Libellula was constrained indicate that any differences are nonsignificant. Based on morphological data, we therefore reject the paraphyly of Libellula and accept the outgroup status of Orthemis ferruginea and Pachydiplax longipennis.

A molecular biogeographic analysis of the relationship between North American melanoploid grasshoppers and their Eurasian and South American relatives

The Melanoplinae constitute one of the two largest subfamilies of Acrididae. Distributed mainly throughout the New World and parts of Eurasia, this group of grasshoppers includes over 100 genera and 800 species. Over the past five decades there has been considerable speculation on the origins of North and South American taxa. The most favored hypothesis proposes an ancient division of Laurasian taxa accompanying the separation of North America and Eurasia, with subsequent radiations within those continents, followed by a recent incursion of Nearctic melanoplines into the southern hemisphere with the establishment of the Isthmus of Panama. This research tests that scenario by phylogenetic analysis using as characters portions of five mitochondrial gene sequences, totaling 2285 bp. Three tree-building methods, maximum-parsimony, neighbor-joining, and maximum-likelihood, strongly support the different view that melanopline grasshoppers originated somewhere in the Americas and spread to the Old World. The feasibility of these findings is discussed within a geological context.

Phylogeny of the major lineages of Membracoidea (Insecta: Hemiptera: Cicadomorpha) based on 28S rDNA sequences

Analysis of sequences from a 3.5-kb region of the nuclear ribosomal 28S DNA gene spanning divergent domains D2-D10 supports the hypothesis, based on fossil, biogeographic, and behavioral evidence, that treehoppers (Aetalionidae and Membracidae) are derived from leafhoppers (Cicadellidae). Maximum-parsimony analysis indicated that treehoppers are the sister group of a lineage comprising the currently recognized cicadellid subfamilies Agalliinae, Megophthalminae, Adelungiinae, and Ulopinae. Based on this phylogenetic estimate, the derivation of treehoppers approximately coincided with shifts in physiology and behavior, including loss of brochosome production and a reversal from active, jumping nymphs to sessile, nonjumping nymphs. Myerslopiidae, traditionally placed as a tribe of the cicadellid subfamily Ulopinae, represented a basal lineage distinct from other extant membracoids. The analysis recovered a large leafhopper lineage comprising a polyphyletic Deltocephalinae (sensu stricto) and its apparent derivatives Koebeliinae, Eupelicinae (polyphyletic), Selenocephalinae, and Penthimiinae. Clades comprising Macropsinae, Neocoelidiinae, Scarinae, Iassinae, Coelidiinae, Eurymelinae + Idiocerinae, Evacanthini + Pagaroniini, Aphrodinae + Ledrinae (in part), Stenocotini + Tartessinae, and Cicadellini + Proconiini were also recovered with moderate to high branch support. Cicadellinae (sensu lato), Ledrinae, Typhlocybinae, and Xestocephalinae were consistently polyphyletic on the most-parsimonious topologies, but constraining these groups to be monophyletic did not significantly increase the length of the cladograms. Relationships among the major lineages received low branch support, suggesting that more data are needed to provide a robust phylogenetic estimate.

Detecting the Geographical Pattern of Speciation from Species-Level Phylogenies

We introduce a general approach for investigating the role of geography in speciation, based on analyzing the geography of sister clades across all nodes in a species-level phylogeny. We examine the predictions of allopatric, sympatric, and peripatric models of speciation in several animal groups, using patterns of range overlap and range size symmetry between sister clades. A simple model of cladogenesis incorporating random movements of species' ranges is used to illustrate the effects of range changes on expected patterns. We find evidence for a predominantly allopatric mode of speciation in our study groups, with sympatry arising through postspeciational range changes. In addition, we find that relatively recent speciation events are characterized by greater asymmetry in range size between sister clades than expected under our null models, providing potential support for the peripatric model of speciation. We discuss the possible confounding effects of postspeciational range changes on our conclusions.

The current state of insect molecular systematics: a thriving Tower of Babel

Insect molecular systematics has undergone remarkable recent growth. Advances in methods of data generation and analysis have led to the accumulation of large amounts of DNA sequence data from most major insect groups. In addition to reviewing theoretical and methodological advances, we have compiled information on the taxa and regions sequenced from all available phylogenetic studies of insects. It is evident that investigators have not usually coordinated their efforts. The genes and regions that have been sequenced differ substantially among studies and the whole of our efforts is thus little greater than the sum of its parts. The cytochrome oxidase I, 16S, 18S, and elongation factor-1 alpha genes have been widely used and are informative across a broad range of divergences in insects. We advocate their use as standards for insect phylogenetics. Insect molecular systematics has complemented and enhanced the value of morphological and ecological data, making substantial contributions to evolutionary biology in the process. A more coordinated approach focused on gathering homologous sequence data will greatly facilitate such efforts.

Phylogenetic relationships of North American damselflies of the genus Ischnura (Odonata: Zygoptera: Coenagrionidae) based on sequences of three mitochondrial genes

Relationships of North American damselflies of the genus Ischnura (Odonata: Zygoptera: Coenagrionidae) were investigated using a total of 1205 bp from portions of three mitochondrial genes: cytochrome b, cytochrome oxidase II, and 12S ribosomal DNA. Parsimony and neighbor joining analyses reveal a monophyletic group consisting of I. damula, I. demorsa, I. perparva, I. posita posita, I. posita atezca, I. verticalis, and probably I. denticollis, likely reflecting a recent radiation in North America. Ischnura kellicotti, I. barberi, I. prognata, I. hastata, I. ramburii, and I. capreola appear to represent much earlier divergences in the group. Many previous hypotheses of relationships among North American species of Ischnura are not supported by the molecular-based analyses. However, there is agreement in many respects between the results of the molecular phylogenetic analyses and the morphologically based conclusions of Kennedy (1919, "The Phylogeny of the Zygoptera," Ph.D. Dissertation, Cornell University, Ithaca). Although results of single-gene phylogenetic analyses often differ, there are very few cases in which there is strong support for conflicting relationships using different partitions of the data. Combined analysis of all three genes yields trees with stronger support overall than the single-gene analyses, and the combined data trees that result from diverse data treatments are congruent with one another in most respects.