Steady Plio-Pleistocene diversification and a 2-million-year sympatry threshold in a New Zealand cicada radiation

Genetic differentiation and phylogeography of Erythroneurini (Hemiptera, Cicadellidae, Typhlocybinae) in the southwestern karst area of China

Erythroneurini is the largest tribe of the microleafhopper subfamily Typhlocybinae. Most prior research on this tribe has focused on traditional classification, phylogeny, and control of agricultural pests, and the phylogeography of the group remains poorly understood. In this study, the mitochondrial genomes of 10 erythroneurine species were sequenced, and sequences of four genes were obtained for 12 geographical populations of Seriana bacilla. The new sequence data were combined with previously available mitochondrial DNA sequence data and analyzed using Bayesian and Maximum-Likelihood-based phylogenetic methods to elucidate relationships among genera and species and estimate divergence times. Seriana was shown to be derived from within Empoascanara. Phylogeographic and population genetic analysis of the endemic Chinese species Seriana bacilla suggest that the species diverged about 54.85 Mya (95% HPD: 20.76-66.23 million years) in the Paleogene period and that population divergence occurred within the last 14 million years. Ancestral area reconstruction indicates that Seriana bacilla may have originated in the central region of Guizhou, and geographical barriers are the main factors affecting gene flow among populations. Ecological niche modeling using the MaxEnt model suggests that the distribution of the species was more restricted in the past but is likely to expand in the future years 2050 and 2070.

Geological events and climate change drive diversification and speciation of mute cicadas in eastern continental Asia

The poor mobility of nymphs living underground, usually for many years and the weak flying ability of adults make cicadas unique for evolutionary biology and bio-geographical study. Cicadas of the genus Karenia are unusual in Cicadidae in lacking the timbals that produce sound. Population differentiation, genetic structure, dispersal and evolutionary history of the eastern Asian mute cicada Karenia caelatata were investigated based on morphological, acoustic and molecular data. The results reveal a high level of genetic differentiation in this species. Six independent clades with nearly unique sets of haplotypes corresponding to geographically isolated populations are recognized. Genetic and geographic distances are significantly correlated among lineages. The phenotypic differentiation is generally consistent with the high levels of genetic divergence across populations. Results of ecological niche modeling suggest that the potential distribution range of this mountain-habitat specialist during the Last Glacial Maximum was broader than its current range, indicating this species had benefited from the climate change during the early Pleistocene in southern China. Geological events such as orogeny in Southwest China and Pleistocene climate oscillations have driven the differentiation and divergence of this species, and basins, plains and rivers function as natural "barriers" to block the gene flow. Besides significant genetic divergence being found among clades, the populations occurring in the Wuyi Mountains and the Hengduan Mountains are significantly different in the calling song structure from other populations. This may have resulted from significant population differentiation and subsequent adaptation of related populations. We conclude that ecological differences in habitats, coupled with geographical isolation, have driven population divergence and allopatric speciation. This study provides a plausible example of incipient speciation in Cicadidae and improves understanding of population differentiation, acoustic signal diversification and phylogeographic relationships of this unusual cicada species. It informs future studies on population differentiation, speciation and phylogeography of other mountain-habitat insects in the East Asian continent.

Testing drivers of acoustic divergence in cicadas (Cicadidae: Tettigettalna)

Divergence in acoustic signals may have a crucial role in the speciation process of animals that rely on sound for intra-specific recognition and mate attraction. The acoustic adaptation hypothesis (AAH) postulates that signals should diverge according to the physical properties of the signalling environment. To be efficient, signals should maximize transmission and decrease degradation. To test which drivers of divergence exert the most influence in a speciose group of insects, we used a phylogenetic approach to the evolution of acoustic signals in the cicada genus Tettigettalna, investigating the relationship between acoustic traits (and their mode of evolution) and body size, climate and micro-/macro-habitat usage. Different traits showed different evolutionary paths. While acoustic divergence was generally independent of phylogenetic history, some temporal variables' divergence was associated with genetic drift. We found support for ecological adaptation at the temporal but not the spectral level. Temporal patterns are correlated with micro- and macro-habitat usage and temperature stochasticity in ways that run against the AAH predictions, degrading signals more easily. These traits are likely to have evolved as an anti-predator strategy in conspicuous environments and low-density populations. Our results support a role of ecological selection, not excluding a likely role of sexual selection in the evolution of Tettigettalna calling songs, which should be further investigated in an integrative approach.

Evolutionary conservation and diversification of auditory neural circuits that process courtship songs in Drosophila

Acoustic communication signals diversify even on short evolutionary time scales. To understand how the auditory system underlying acoustic communication could evolve, we conducted a systematic comparison of the early stages of the auditory neural circuit involved in song information processing between closely-related fruit-fly species. Male Drosophila melanogaster and D. simulans produce different sound signals during mating rituals, known as courtship songs. Female flies from these species selectively increase their receptivity when they hear songs with conspecific temporal patterns. Here, we firstly confirmed interspecific differences in temporal pattern preferences; D. simulans preferred pulse songs with longer intervals than D. melanogaster. Primary and secondary song-relay neurons, JO neurons and AMMC-B1 neurons, shared similar morphology and neurotransmitters between species. The temporal pattern preferences of AMMC-B1 neurons were also relatively similar between species, with slight but significant differences in their band-pass properties. Although the shift direction of the response property matched that of the behavior, these differences are not large enough to explain behavioral differences in song preferences. This study enhances our understanding of the conservation and diversification of the architecture of the early-stage neural circuit which processes acoustic communication signals.

Lack of host phylogenetic structure in the gut bacterial communities of New Zealand cicadas and their interspecific hybrids

Host-microbe interactions are intimately linked to eukaryotic evolution, particularly in sap-sucking insects that often rely on obligate microbial symbionts for nutrient provisioning. Cicadas (Cicadidae: Auchenorrhyncha) specialize on xylem fluid and derive many essential amino acids and vitamins from intracellular bacteria or fungi (Hodgkinia, Sulcia, and Ophiocordyceps) that are propagated via transmission from mothers to offspring. Despite the beneficial role of these non-gut symbionts in nutrient provisioning, the role of beneficial microbiota within the gut remains unclear. Here, we investigate the relative abundance and impact of host phylogeny and ecology on gut microbial diversity in cicadas using 16S ribosomal RNA gene amplicon sequencing data from 197 wild-collected cicadas and new mitochondrial genomes across 38 New Zealand cicada species, including natural hybrids between one pair of two species. We find low abundance and a lack of phylogenetic structure and hybrid effects but a significant role of elevation in explaining variation in gut microbiota.

Phylogeography reveals the complex impact of the Last Glacial Maximum on New Zealand's terrestrial biota

We review the major phylogeographic patterns in Aotearoa New Zealand's terrestrial flora and fauna that have been associated with the Ōtira Glaciation of the Pleistocene, the end of which coincides with the global Last Glacial Maximum (LGM). We focus on (1) the complexity of biogeographic histories of New Zealand species, with LGM-driven phenomena overlaying the impacts of mountain-building and other drivers of phylogeographic structure; (2) the locations of glacial refugia and sets of taxa which may have shared refugia; and (3) the role of glaciation in driving diversification. We end with a brief focus on the next directions, including what can we learn about New Zealand's glacial history by expanding our phylogeographic toolbox to include genomic methods and hypothesis-driven inference methods. We provide follow-up questions which take advantage of the wealth of phylogeographic data for New Zealand.

Insights into Aotearoa New Zealand's biogeographic history provided by the study of natural hybrid zones

Hybridisation is commonly observed in geographical zones of contact between distinct lineages. These contact zones have long been of interest for biogeographers because they provide insight into the evolutionary and ecological processes that influence the distribution of species as well as the process of speciation. Here we review research on hybrid zones and zones of past introgression, both terrestrial and marine, in Aotearoa New Zealand. Many of New Zealand's hybrid zones occur between lineages or species that diverged prior to the Last Glacial Maximum (LGM), with numerous divergences dating to the early Pleistocene or Pliocene. Few secondary contact zones have been detected in terrestrial plants and in marine taxa. This may reflect a lack of the intensive sampling required to detect hybrid zones in these groups but for plants may also indicate widespread Pleistocene survival across the country. Lastly, we suggest avenues for research into New Zealand hybrid zones that are likely to be fruitful.

Advances in the Evolution and Ecology of 13- and 17-Year Periodical Cicadas

Apart from model organisms, 13- and 17-year periodical cicadas (Hemiptera: Cicadidae: Magicicada) are among the most studied insects in evolution and ecology. They are attractive subjects because they predictably emerge in large numbers; have a complex biogeography shaped by both spatial and temporal isolation; and include three largely sympatric, parallel species groups that are, in a sense, evolutionary replicates. Magicicada are also relatively easy to capture and manipulate, and their spectacular, synchronized mass emergences facilitate outreach and citizen science opportunities. Since the last major review, studies of Magicicada have revealed insights into reproductive character displacement and the nature of species boundaries, provided additional examples of allochronic speciation, found evidence for repeated and parallel (but noncontemporaneous) evolution of 13- and 17-year life cycles, quantified the amount and direction of gene flow through time, revealed phylogeographic patterning resulting from paleoclimate change, examined the timing of juvenile development, and created hypotheses for the evolution of life-cycle control and the future effects of climate changeon Magicicada life cycles. New ecological studies have supported and questioned the role of prime numbers in Magicicada ecology and evolution, found bidirectional shifts in population size over generations, quantified the contribution of Magicicada to nutrient flow in forest ecosystems, and examined behavioral and biochemical interactions between Magicicada and their fungal parasites and bacterial endosymbionts.

Phylogeography of the endemic red-tailed cicadas of New Zealand (Hemiptera: Cicadidae: Rhodopsalta), and molecular, morphological and bioacoustical confirmation of the existence of Hudson’s Rhodopsalta microdora

Why do some genera radiate, whereas others do not? The genetic structure of present-day populations can provide clues for developing hypotheses. In New Zealand, three Cicadidae genera are depauperate [Amphipsalta (three species), Notopsalta (one species) and Rhodopsalta (three species)], whereas two have speciated extensively [Kikihia (~30 species/subspecies) and Maoricicada (~20 species/subspecies). Here, we examine the evolution of Rhodopsalta, the last New Zealand genus to be studied phylogenetically and phylogeographically. We use Bayesian and maximum-likelihood analyses of mitochondrial cox1 and nuclear EF1α gene sequences. Concatenated and single-gene phylogenies for 70 specimens (58 localities) support its monophyly and three described species: Rhodopsalta cruentata, Rhodopsalta leptomera and Rhodopsalta microdora, the last taxon previously regarded as uncertain. We provide distribution maps, biological notes and the first descriptions of diagnostic songs. We show that both R. cruentata and R. microdora exhibit northern and southern genetic subclades. Subclades of the dry-adapted R. microdora clade show geographical structure, whereas those of the mesic R. cruentata and sand-dune specialist R. leptomera have few discernible patterns. Genetic, bioacoustical and detailed distributional evidence for R. microdora add to the known biodiversity of New Zealand. We designate a lectotype for Tettigonia cruentata  Fabricius, 1775, the type species of Rhodopsalta.

Speciation across the Tree of Life

Much of what we know about speciation comes from detailed studies of well-known model systems. Although there have been several important syntheses on speciation, few (if any) have explicitly compared speciation among major groups across the Tree of Life. Here, we synthesize and compare what is known about key aspects of speciation across taxa, including bacteria, protists, fungi, plants, and major animal groups. We focus on three main questions. Is allopatric speciation predominant across groups? How common is ecological divergence of sister species (a requirement for ecological speciation), and on what niche axes do species diverge in each group? What are the reproductive isolating barriers in each group? Our review suggests the following patterns. (i) Based on our survey and projected species numbers, the most frequent speciation process across the Tree of Life may be co-speciation between endosymbiotic bacteria and their insect hosts. (ii) Allopatric speciation appears to be present in all major groups, and may be the most common mode in both animals and plants, based on non-overlapping ranges of sister species. (iii) Full sympatry of sister species is also widespread, and may be more common in fungi than allopatry. (iv) Full sympatry of sister species is more common in some marine animals than in terrestrial and freshwater ones. (v) Ecological divergence of sister species is widespread in all groups, including ~70% of surveyed species pairs of plants and insects. (vi) Major axes of ecological divergence involve species interactions (e.g. host-switching) and habitat divergence. (vii) Prezygotic isolation appears to be generally more widespread and important than postzygotic isolation. (viii) Rates of diversification (and presumably speciation) are strikingly different across groups, with the fastest rates in plants, and successively slower rates in animals, fungi, and protists, with the slowest rates in prokaryotes. Overall, our study represents an initial step towards understanding general patterns in speciation across all organisms.

Linear and geometric morphometric analyses of variation of the plectrum in four species of bess beetles, tribe Proculini (Coleoptera: Passalidae)

Bess beetles are sapro-xillophagous insects that inhabit decaying logs. They display sub-social behavior and acoustic communication. Adults produce sounds with an abdomino-alary stridulatory system. The sixth abdominal tergum has lateral protuberances with spines (pars stridens), whereas the hind wings have spines in the radial cell (plectrum). The potential taxonomic utility of these spines has not been studied. We evaluated the variation of spines in the plectrum of adult females sampling four species of Proculini using traditional and geometric morphometric methods. We divided the plectrum into five zones to compare the density, size and shape of spines among zones and among species comparing each zone separately. Spine shape and size were quantified with 2D cartesian coordinates and four variables from SEM micrographs. Separate univariate and multivariate analyses of variance revealed that the size, density and shape of spines is different among zones in each of the four species. Also, spine shape and size in all zones is different among species, which would imply that plectrum spines might have taxonomic utility. Additionally, disparity analyses showed that the peripheral zones have a higher variability, and the disparity values in the middle and apex zones are higher in the two species with a wide distribution range.

Molecular approach for identification of Catla catla using mitochondrial CO1 from Pakistan

DNA barcoding is a rapid, precise, and effective way of species identification. A short and standard target gene marker is used to create sequence profile of identified species. Specific tag or marker is used, which is derived from mitochondrial COI for identification. Effectiveness of this method axes the degree of divergence among species. Identification is necessary for their representation. In the present work, Catla catla was used to study by using Cytochrome C Oxidase 1.The genetic distances were computed, and Neighbor Joining tree was constructed based on the Kimura 2 Parameter method. GenBank and BOLD revealed definitive identity matches. Conspecific and congeneric K2P nucleotide divergence was estimated. Evolutionary tree was analyzed clearly by relating their species to phylogenetic tree, as same as species were bunched under same tree node, while species were differently clustered under distinct nodes. These findings conclude that the gene sequence may serve as a milestone for identification and phylogenetic history of related species at molecular level.

Off-target capture data, endosymbiont genes and morphology reveal a relict lineage that is sister to all other singing cicadas

Phylogenetic asymmetry is common throughout the tree of life and results from contrasting patterns of speciation and extinction in the paired descendant lineages of ancestral nodes. On the depauperate side of a node, we find extant ‘relict’ taxa that sit atop long, unbranched lineages. Here, we show that a tiny, pale green, inconspicuous and poorly known cicada in the genus Derotettix, endemic to degraded salt-plain habitats in arid regions of central Argentina, is a relict lineage that is sister to all other modern cicadas. Nuclear and mitochondrial phylogenies of cicadas inferred from probe-based genomic hybrid capture data of both target and non-target loci and a morphological cladogram support this hypothesis. We strengthen this conclusion with genomic data from one of the cicada nutritional bacterial endosymbionts, Sulcia, an ancient and obligate endosymbiont of the larger plant-sucking bugs (Auchenorrhyncha) and an important source of maternally inherited phylogenetic data. We establish Derotettiginae subfam. nov. as a new, monogeneric, fifth cicada subfamily, and compile existing and new data on the distribution, ecology and diet of Derotettix. Our consideration of the palaeoenvironmental literature and host-plant phylogenetics allows us to predict what might have led to the relict status of Derotettix over 100 Myr of habitat change in South America.

Rapid and recent diversification patterns in Anseriformes birds: Inferred from molecular phylogeny and diversification analyses

The Anseriformes is a well-known and widely distributed bird order, with more than 150 species in the world. This paper aims to revise the classification, determine the phylogenetic relationships and diversification patterns in Anseriformes by exploring the Cyt b, ND2, COI genes and the complete mitochondrial genomes (mito-genomes). Molecular phylogeny and genetic distance analyses suggest that the Dendrocygna species should be considered as an independent family, Dendrocygnidae, rather than a member of Anatidae. Molecular timescale analyses suggests that the ancestral diversification occurred during the Early Eocene Climatic Optimum (58 ~ 50 Ma). Furthermore, diversification analyses showed that, after a long period of constant diversification, the median initial speciation rate was accelerated three times, and finally increased to approximately 0.3 sp/My. In the present study, both molecular phylogeny and diversification analyses results support that Anseriformes birds underwent rapid and recent diversification in their evolutionary history, especially in modern ducks, which show extreme diversification during the Plio-Pleistocene (~ 5.3 Ma). Therefore, our study support that the Plio-Pleistocene climate fluctuations are likely to have played a significant role in promoting the recent diversification for Anseriformes.

Reinforcement and a cline in mating behaviour evolve in response to secondary contact and hybridization in shield-back katydids (Orthoptera: Tettigoniidae)

In a dispersal-limited species that has evolved reproductive character displacement at a contact zone, a cline in mating behaviour may result if gene flow diffuses alleles out of the contact zone into allopatric populations. Prior work has found such a clinal pattern in the shield-back katydid Aglaothorax morsei, in which the male calling songs in a sympatric population have a displaced, short interpulse interval that increases in length with increasing distance from the contact zone. In this study, molecular phylogenetic and female preference data show that (1) sympatric populations result from secondary contact, (2) hybridization in sympatry has resulted in unidirectional mitochondrial introgression and (3) female preferences are consistent with reproductive character displacement and could generate a cline in mating behaviour. These data together suggest a history of reinforcement, generally considered rare in acoustically communicating insects; thus, Aglaothorax represents an important example of a rarely documented evolutionary process.

Acoustic, genetic and morphological variations within the katydid Gampsocleis sedakovii (Orthoptera, Tettigonioidea)

In an attempt to explain the variation within this species and clarify the subspecies classification, an analysis of the genetic, calling songs, and morphological variations within the species Gampsocleissedakovii is presented from Inner Mongolia, China. Recordings were compared of the male calling songs and analysis performed of selected acoustic variables. This analysis is combined with sequencing of mtDNA - COI and examination of morphological traits to perform cluster analyses. The trees constructed from different datasets were structurally similar, bisecting the six geographical populations studied. Based on two large branches in the analysis, the species Gampsocleissedakovii was partitioned into two subspecies, Gampsocleissedakoviisedakovii (Fischer von Waldheim, 1846) and Gampsocleissedakoviiobscura (Walker, 1869). Comparing all the traits, the individual of Elunchun (ELC) was the intermediate type in this species according to the acoustic, genetic, and morphological characteristics. This study provides evidence for insect acoustic signal divergence and the process of subspeciation.

Inflation of Molecular Clock Rates and Dates: Molecular Phylogenetics, Biogeography, and Diversification of a Global Cicada Radiation from Australasia (Hemiptera: Cicadidae: Cicadettini)

Dated phylogenetic trees are important for studying mechanisms of diversification, and molecular clocks are important tools for studies of organisms lacking good fossil records. However, studies have begun to identify problems in molecular clock dates caused by uncertainty of the modeled molecular substitution process. Here we explore Bayesian relaxed-clock molecular dating while studying the biogeography of ca. 200 species from the global cicada tribe Cicadettini. Because the available fossils are few and uninformative, we calibrate our trees in part with a cytochrome oxidase I (COI) clock prior encompassing a range of literature estimates for arthropods. We show that tribe-level analyses calibrated solely with the COI clock recover extremely old dates that conflict with published estimates for two well-studied New Zealand subclades within Cicadettini. Additional subclade analyses suggest that COI relaxed-clock rates and maximum-likelihood branch lengths become inflated relative to EF-1[Formula: see text] intron and exon rates and branch lengths as clade age increases. We present corrected estimates derived from: (i) an extrapolated EF-1[Formula: see text] exon clock derived from COI-calibrated analysis within the largest New Zealand subclade; (ii) post hoc scaling of the tribe-level chronogram using results from subclade analyses; and (iii) exploitation of a geological calibration point associated with New Caledonia. We caution that considerable uncertainty is generated due to dependence of substitution estimates on both the taxon sample and the choice of model, including gamma category number and the choice of empirical versus estimated base frequencies. Our results suggest that diversification of the tribe Cicadettini commenced in the early- to mid-Cenozoic and continued with the development of open, arid habitats in Australia and worldwide. We find that Cicadettini is a rare example of a global terrestrial animal group with an Australasian origin, with all non-Australasian genera belonging to two distal clades. Within Australia, we show that Cicadettini is more widely distributed than any other cicada tribe, diverse in temperate, arid and monsoonal habitats, and nearly absent from rainforests. We comment on the taxonomic implications of our findings for thirteen cicada genera.

Isolation and characterization of microsatellite markers useful for exploring introgression among species in the diverse New Zealand cicada genus Kikihia

The New Zealand cicada genus Kikihia Dugdale 1971 exhibits more than 20 contact zones between species pairs that vary widely in their divergence times (between 20,000 and 2 million years) in which some level of hybridization is evident. Mitochondrial phylogenies suggest some movement of genes across species boundaries. Biparentally inherited and quickly evolving molecular markers like microsatellites are useful for assessing gene flow levels. Here, we present six polymorphic microsatellite loci that amplify DNA from seven species across the genus Kikihia; Kikihia "northwestlandica," Kikihia "southwestlandica," Kikihia muta, Kikihia angusta, Kikihia "tuta," Kikihia "nelsonensis," and Kikihia "murihikua." The markers were developed using whole-genome shotgun sequencing on the 454 pyrosequencing platform. Moderate to high levels of polymorphisms were observed with 14-47 alleles for 213 individuals from 15 populations. Observed and expected heterozygosity range from 0 to 1 and 0.129 to 0.945, respectively. These new markers will be instrumental for the assessment of gene flow across multiple contact zones in Kikihia.

Species radiation of carabid beetles (broscini: mecodema) in new zealand

New Zealand biodiversity has often been viewed as Gondwanan in origin and age, but it is increasingly apparent from molecular studies that diversification, and in many cases origination of lineages, postdate the break-up of Gondwanaland. Relatively few studies of New Zealand animal species radiations have as yet been reported, and here we consider the species-rich genus of carabid beetles, Mecodema. Constrained stratigraphic information (emergence of the Chatham Islands) and a substitution rate for Coleoptera were separately used to calibrate Bayesian relaxed molecular clock date estimates for diversification of Mecodema. The inferred timings indicate radiation of these beetles no earlier than the mid-Miocene with most divergences being younger, dating to the Plio-Pleistocene. A shallow age for the radiation along with a complex spatial distribution of these taxa involving many instances of sympatry implicates recent ecological speciation rather than a simplistic allopatric model. This emphasises the youthful and dynamic nature of New Zealand evolution that will be further elucidated with detailed ecological and population genetic analyses.

Conflicting patterns of DNA barcoding and taxonomy in the cicada genus Tettigettalna from Southern Europe (Hemiptera: Cicadidae)

DNA barcodes have great potential to assist in species identification, especially when high taxonomical expertise is required. We investigated the utility of the 5' mitochondrial cytochrome c oxidase I (COI) region to discriminate between 13 European cicada species. These included all nine species currently recognized under the genus Tettigettalna, from which seven are endemic to the southern Iberian Peninsula. These cicadas have species-specific male calling songs but are morphologically very similar. Mean COI divergence between congeners ranged from 0.4% to 10.6%, but this gene was proven insufficient to determine species limits within genus Tettigettalna because a barcoding gap was absent for several of its species, that is, the highest intraspecific distance exceeded the lowest interspecific distance. The genetic data conflicted with current taxonomic classification for T. argentata and T. mariae. Neighbour-joining and Bayesian analyses revealed that T. argentata is geographically structured (clades North and South) and might constitute a species complex together with T. aneabi and T. mariae. The latter diverges very little from the southern clade of T. argentata and shares with it its most common haplotype. T. mariae is often in sympatry with T. argentata but it remains unclear whether introgression or incomplete lineage sorting may be responsible for the sharing of haplotypes. T. helianthemi and T. defauti also show high intraspecific variation that might signal hidden cryptic diversity. These taxonomic conflicts must be re-evaluated with further studies using additional genes and extensive morphological and acoustic analyses.

Evolutionary divergence in acoustic signals: causes and consequences

Acoustic signals mediate mate choice, resource defense, and species recognition in a broad range of taxa. It has been proposed, therefore, that divergence in acoustic signals plays a key role in speciation. Nonetheless, the processes driving divergence of acoustic traits and their consequences in terms of speciation are poorly understood. A review of empirical and comparative studies reveals strong support for a role of sexual selection in acoustic divergence, but the possible concomitant influences of ecological context are rarely examined. We summarize a conceptual framework for testing the relative significance of both adaptive and neutral mechanisms leading to acoustic divergence, predictions for cases where these processes lead to speciation, and how their relative importance plays out over evolutionary time.

Limited, episodic diversification and contrasting phylogeography in a New Zealand cicada radiation

BACKGROUND

The New Zealand (NZ) cicada fauna contains two co-distributed lineages that independently colonized the isolated continental fragment in the Miocene. One extensively studied lineage includes 90% of the extant species (Kikihia + Maoricicada + Rhodopsalta; ca 51 spp.), while the other contains just four extant species (Amphipsalta - 3 spp. + Notopsalta - 1 sp.) and has been little studied. We examined mitochondrial and nuclear-gene phylogenies and phylogeography, Bayesian relaxed-clock divergence timing (incorporating literature-based uncertainty of molecular clock estimates) and ecological niche models of the species from the smaller radiation.

RESULTS

Mitochondrial and nuclear-gene trees supported the monophyly of Amphipsalta. Most interspecific diversification within Amphipsalta-Notopsalta occurred from the mid-Miocene to the Pliocene. However, interspecific divergence time estimates had large confidence intervals and were highly dependent on the assumed tree prior, and comparisons of uncorrected and patristic distances suggested difficulty in estimation of branch lengths. In contrast, intraspecific divergence times varied little across analyses, and all appear to have occurred during the Pleistocene. Two large-bodied forest taxa (A. cingulata, A. zelandica) showed minimal phylogeographic structure, with intraspecific diversification dating to ca. 0.16 and 0.37 Ma, respectively. Mid-Pleistocene-age phylogeographic structure was found within two smaller-bodied species (A. strepitans - 1.16 Ma, N. sericea - 1.36 Ma] inhabiting dry open habitats. Branches separating independently evolving species were long compared to intraspecific branches. Ecological niche models hindcast to the Last Glacial Maximum (LGM) matched expectations from the genetic datasets for A. zelandica and A. strepitans, suggesting that the range of A. zelandica was greatly reduced while A. strepitans refugia were more extensive. However, no LGM habitat could be reconstructed for A. cingulata and N. sericea, suggesting survival in microhabitats not detectable with our downscaled climate data.

CONCLUSIONS

Unlike the large and continuous diversification exhibited by the Kikihia-Maoricicada-Rhodopsalta clade, the contemporaneous Amphipsalta-Notopsalta lineage contains four comparatively old (early branching) species that show only recent diversification. This indicates either a long period of stasis with no speciation, or one or more bouts of extinction that have pruned the radiation. Within Amphipsalta-Notopsalta, greater population structure is found in dry-open-habitat species versus forest specialists. We attribute this difference to the fact that NZ lowland forests were repeatedly reduced in extent during glacial periods, while steep, open habitats likely became more available during late Pleistocene uplift.

The Invertebrate Life of New Zealand: A Phylogeographic Approach

Phylogeography contributes to our knowledge of regional biotas by integrating spatial and genetic information. In New Zealand, comprising two main islands and hundreds of smaller ones, phylogeography has transformed the way we view our biology and allowed comparison with other parts of the world. Here we review studies on New Zealand terrestrial and freshwater invertebrates. We find little evidence of congruence among studies of different taxa; instead there are signatures of partitioning in many different regions and expansion in different directions. A number of studies have revealed unusually high genetic distances within putative species, and in those where other data confirm this taxonomy, the revealed phylogeographic structure contrasts with northern hemisphere continental systems. Some taxa show a signature indicative of Pliocene tectonic events encompassing land extension and mountain building, whereas others are consistent with range expansion following the last glacial maximum (LGM) of the Pleistocene. There is some indication that montane taxa are more partitioned than lowland ones, but this observation is obscured by a broad range of patterns within the sample of lowland/forest taxa. We note that several geophysical processes make similar phylogeographic predictions for the same landscape, rendering confirmation of the drivers of partitioning difficult. Future multi-gene analyses where applied to testable alternative hypotheses may help resolve further the rich evolutionary history of New Zealand's invertebrates.

Deep mtDNA subdivision within Linnean species in an endemic radiation of tiger beetles from New Zealand (genus Neocicindela)

The invertebrate fauna of New Zealand is of great interest as a geologically tractable model for the study of species diversification, but direct comparisons with closely related lineages elsewhere are lacking. Integrating population-level analyses with studies of taxonomy and clade diversification, we performed mtDNA analysis on Neocicindela (Cicindelidae, tiger beetles) for a broad sample of populations from 11 of 12 known species and 161 specimens (three loci, 1883 nucleotides), revealing 123 distinct haplotypes. Phylogenetic reconstruction recovered two main lineages, each composed of 5-6 Linnean species whose origin was dated to 6.66 and 7.26 Mya, while the Neocicindela stem group was placed at 10.82 ± 0.48 Mya. Species delimitation implementing a character-based (diagnostic) species concept recognized 19 species-level groups that were in general agreement with Linnean species but split some of these into mostly allopatric subgroups. Tree-based methods of species delimitation using a mixed Yule-coalescence model were inconclusive, and recognized 32-51 entities (including singletons), splitting existing species into up to 8 partially sympatric groups. These findings were different from patterns in the Australian sister genus Rivacindela, where character-based and tree-based methods were previously shown to produce highly congruent groupings. In Neocicindela, the pattern of mtDNA variation was characterized by high intra-population and intra-species haplotype divergence, the coexistence of divergent haplotypes in sympatry, and a poor correlation of genetic and geographic distance. These observations combined suggest a scenario of phylogeographic divergence and secondary contact driven by orogenetic and climatic changes of the Pleistocene/Pliocene. The complex evolutionary history of most species of Neocicindela due to the relative instability of the New Zealand biota resulted in populations of mixed ancestry but not in a general loss of genetic variation.

Onset of glaciation drove simultaneous vicariant isolation of Alpine insects in New Zealand

The origin of the New Zealand "beech gap," a low-diversity zone in the central South Island corresponding with a disjunction in the distribution of many taxa, has been the focus of biogeographical debate for many decades. Here, we use comparative phylogeographic analysis (COI; H3) of six alpine stonefly genera (116 individuals, 102 localities) to test a vicariant evolutionary hypothesis for the origin of this "biotic gap." We find strikingly similar phylogeographic patterns in all six genera, with the deepest genetic divergences always found between samples north and south of the beech gap. The magnitude of north-south genetic differentiation for COI is similar across all six genera (ranging from 0.074 to 0.091), with a test for simultaneous vicariance confirming that divergence is consistent with a single evolutionary event. The concordant cladogenesis detected across multiple taxa is consistent with vicariant isolation caused by the onset of glaciation in the late Pliocene. This study thus indicates an important cladogenetic role for glaciation, an abiotic evolutionary process that is more typically associated with loss of biodiversity.

Homology of olfactory receptor neuron response characteristics inferred from hybrids between Asian and European corn borer moths (Lepidoptera: Crambidae)

First generation hybrid males from crosses between the Asian corn borer (ACB), Ostrinia furnacalis, and the "univoltine Z-strain" European corn borer (ECB), Ostrinia nubilalis, were examined with respect to behavioral and physiological responses to ACB and ECB pheromones. The hybrid males often flew to the pheromone of ECB Z-strain, but very rarely to the ACB pheromone. We mapped the tuning profiles of each ORN of the F(1) hybrids with respect to the relevant pheromone components and a common behavioral antagonist by employing differential cross-adaptation and varying doses of the ligands. In the trichoid sensilla of F(1) hybrid males, the three co-compartmentalized ORNs produced spikes that were very difficult to distinguish by size, unlike the parental populations. Comparing the responses to ACB and ECB components at different doses reveals overlapping profiles similar to males of both parental types, but more responsiveness to the ECB pheromone components. We were unable to detect any differences in the ORN tuning profiles when comparing males with different behavioral phenotypes. While the two ECB pheromone races have similar ORN tuning properties that are different from those in ACB, the spike-amplitude patterns of ECB E-strain and ACB have greater homology when compared to ECB Z-strain.

Cryptic failure of partitioned Bayesian phylogenetic analyses: lost in the land of long trees

Partitioned Bayesian phylogenetic analyses of routine genetic data sets, constructed using MrBayes (Ronquist and Huelsenbeck 2003), can become trapped in regions of parameter space characterized by unrealistically long trees and distorted partition rate multipliers. Such analyses commonly fail to reach stationarity during hundreds of millions of generations of sampling-many times longer than most published analyses. Some data sets are so prone to this problem that paired MrBayes runs begun from different starting trees repeatedly find the same incorrect long-tree solutions and consequently pass the most commonly employed tests of stationarity, including the average standard deviation of split frequencies (ASDSF) and the potential scale reduction factor (PSRF) statistics offered by MrBayes (Gelman and Rubin 1992). In these situations, failure to reach stationarity is recognizable only in light of prior knowledge of model parameters, such as the expectation that third-codon-position sites usually evolve fastest in protein-coding genes. The conditions that lead to the long-tree problem are frequently encountered in phylogenetic studies today, and I present 6 demonstration examples from the literature. Although the effects on tree length (TL) are often dramatic, effects on topology appear to be subtle. Susceptibility to the problem is sometimes predicted by the difference between the true TL and the starting TL. In some cases, the problems described here can be avoided or reduced by manipulation of the starting TL and/or by adjustments to the prior on branch lengths. In more difficult situations, accurate branch length estimation may not be possible with Bayesian methods because of dependence of the solution on the branch length prior.

Do geological or climatic processes drive speciation in dynamic archipelagos? The tempo and mode of diversification in Southeast Asian shrews

Geological and climatic processes potentially alter speciation rates by generating and modifying barriers to dispersal. In Southeast Asia, two processes have substantially altered the distribution of land. Volcanic uplift produced many new islands during the Miocene-Pliocene and repeated sea level fluctuations during the Pleistocene resulted in intermittent land connections among islands. Each process represents a potential driver of diversification. We use a phylogenetic analysis of a group of Southeast Asian shrews (Crocidura) to examine geographic and temporal processes of diversification. In general, diversification has taken place in allopatry following the colonization of new areas. Sulawesi provides an exception, where we cannot reject within-island speciation for a clade of eight sympatric and syntopic species. We find only weak support for temporally declining diversification rates, implying that neither volcanic uplift nor sea level fluctuations had a strong effect on diversification rates. We suggest that dynamic archipelagos continually offer new opportunities for allopatric diversification, thereby sustaining high speciation rates over long periods of time, or Southeast Asian shrews represent an immature radiation on a density-dependent trajectory that has yet to fill geographic and ecological space.

Versatile aggressive mimicry of cicadas by an Australian predatory katydid

Background

In aggressive mimicry, a predator or parasite imitates a signal of another species in order to exploit the recipient of the signal. Some of the most remarkable examples of aggressive mimicry involve exploitation of a complex signal-response system by an unrelated predator species.

Methodology/Principal Findings

We have found that predatory Chlorobalius leucoviridis katydids (Orthoptera: Tettigoniidae) can attract male cicadas (Hemiptera: Cicadidae) by imitating the species-specific wing-flick replies of sexually receptive female cicadas. This aggressive mimicry is accomplished both acoustically, with tegminal clicks, and visually, with synchronized body jerks. Remarkably, the katydids respond effectively to a variety of complex, species-specific Cicadettini songs, including songs of many cicada species that the predator has never encountered.

Conclusions/Significance

We propose that the versatility of aggressive mimicry in C. leucoviridis is accomplished by exploiting general design elements common to the songs of many acoustically signaling insects that use duets in pair-formation. Consideration of the mechanism of versatile mimicry in C. leucoviridis may illuminate processes driving the evolution of insect acoustic signals, which play a central role in reproductive isolation of populations and the formation of species.

Evolution of New Zealand's terrestrial fauna: a review of molecular evidence

New Zealand biogeography has been dominated by the knowledge that its geophysical history is continental in nature. The continental crust (Zealandia) from which New Zealand is formed broke from Gondwanaland ca 80 Ma, and there has existed a pervading view that the native biota is primarily a product of this long isolation. However, molecular studies of terrestrial animals and plants in New Zealand indicate that many taxa arrived since isolation of the land, and that diversification in most groups is relatively recent. This is consistent with evidence for species turnover from the fossil record, taxonomic affinity, tectonic evidence and observations of biological composition and interactions. Extinction, colonization and speciation have yielded a biota in New Zealand which is, in most respects, more like that of an oceanic archipelago than a continent.