Chromosomal evolution, environmental heterogeneity, and migration drive spatial patterns of species richness in Calochortus (Liliaceae).

We used nuclear genomic data and statistical models to evaluate the ecological and evolutionary processes shaping spatial variation in species richness in Calochortus (Liliaceae, 74 spp.). Calochortus occupies diverse habitats in the western United States and Mexico and has a center of diversity in the California Floristic Province, marked by multiple orogenies, winter rainfall, and highly divergent climates and substrates (including serpentine). We used sequences of 294 low-copy nuclear loci to produce a time-calibrated phylogeny, estimate historical biogeography, and test hypotheses regarding drivers of present-day spatial patterns in species number. Speciation and species coexistence require reproductive isolation and ecological divergence, so we examined the roles of chromosome number, environmental heterogeneity, and migration in shaping local species richness. Six major clades-inhabiting different geographic/climatic areas, and often marked by different base chromosome numbers (n = 6 to 10)-began diverging from each other ~10.3 Mya. As predicted, local species number increased significantly with local heterogeneity in chromosome number, elevation, soil characteristics, and serpentine presence. Species richness is greatest in the Transverse/Peninsular Ranges where clades with different chromosome numbers overlap, topographic complexity provides diverse conditions over short distances, and several physiographic provinces meet allowing immigration by several clades. Recently diverged sister-species pairs generally have peri-patric distributions, and maximum geographic overlap between species increases over the first million years since divergence, suggesting that chromosomal evolution, genetic divergence leading to gametic isolation or hybrid inviability/sterility, and/or ecological divergence over small spatial scales may permit species co-occurrence.

The effect of biofluorescence on predation upon Cope's gray treefrog: A clay model experiment.

Biofluorescence, the ability to absorb light and reemit it at a longer wavelength, is present in many taxa but has been examined only recently in amphibians. Over half of the studies documenting biofluorescence in the last century suggest this fluorescent signal may affect predation; however, to date, only one other experimental study has tested this hypothesis. To address this question, we experimentally tested the effect of biofluorescence on predation through the study of the Cope's Gray Treefrog, Hyla chrysoscelis. First, we quantified the spectral characteristics of a novel biofluorescence pattern in H. chrysoscelis. In both sexes of this species, the fluorescent signal is concentrated in an area that contains a proposed aposematic pattern to warn predators of the frog's toxic secretions. We hypothesized that the biofluorescent trait may increase the conspicuousness of this pattern and enable the frogs to deter predators more effectively. Second, we tested this prediction by conducting a clay model field experiment to assess differences in predation attempts on fluorescent versus non-fluorescent H. chrysoscelis models by various predator types. We found no effect of biofluorescence on the overall presence, type, or location of predation, suggesting that biofluorescence alone does not act as an antipredator signal of H. chrysoscelis. This study represents one of the first attempts to experimentally test the effect of biofluorescence on predation in any organism and the first to do so in amphibians. Further work is needed to explore the role of this trait in predation in other systems and to investigate alternative functions for the biofluorescent signal in H. chrysoscelis.

Populating a Continent: Phylogenomics Reveal the Timing of Australian Frog Diversification.

The Australian continent's size and isolation make it an ideal place for studying the accumulation and evolution of biodiversity. Long separated from the ancient supercontinent Gondwana, most of Australia's plants and animals are unique and endemic, including the continent's frogs. Australian frogs comprise a remarkable ecological and morphological diversity categorized into a small number of distantly related radiations. We present a phylogenomic hypothesis based on an exon-capture dataset that spans the main clades of Australian myobatrachoid, pelodryadid hyloid, and microhylid frogs. Our time-calibrated phylogenomic-scale phylogeny identifies great disparity in the relative ages of these groups which vary from Gondwanan relics to recent immigrants from Asia and include arguably the continent's oldest living vertebrate radiation. This age stratification provides insight into the colonization of⁠, and diversification on, the Australian continent through deep time, during periods of dramatic climatic and community changes. Contemporary Australian frog diversity highlights the adaptive capacity of anurans, particularly in response to heat and aridity, and explains why they are one of the continent's most visible faunas.

Biogeography and the evolution of acoustic communication in the polyploid North American grey treefrog complex.

After polyploid species are formed, interactions between diploid and polyploid lineages may generate additional diversity in novel cytotypes and phenotypes. In anurans, mate choice by acoustic communication is the primary method by which individuals identify their own species and assess suitable mates. As such, the evolution of acoustic signals is an important mechanism for contributing to reproductive isolation and diversification in this group. Here, we estimate the biogeographical history of the North American grey treefrog complex, consisting of the diploid Hyla chrysoscelis and the tetraploid Hyla versicolor, focusing specifically on the geographical origin of whole genome duplication and the expansion of lineages out of glacial refugia. We then test for lineage-specific differences in mating signals by applying comparative methods to a large acoustic data set collected over 52 years that includes >1500 individual frogs. Along with describing the overall biogeographical history and call diversity, we found evidence that the geographical origin of H. versicolor and the formation of the midwestern polyploid lineage are both associated with glacial limits, and that the southwestern polyploid lineage is associated with a shift in acoustic phenotype relative to the diploid lineage with which they share a mitochondrial lineage. In H. chrysoscelis, we see that acoustic signals are largely split by Eastern and Western lineages, but that northward expansion along either side of the Appalachian Mountains is associated with further acoustic diversification. Overall, results of this study provide substantial clarity on the evolution of grey treefrogs as it relates to their biogeography and acoustic communication.

Rapid radiation of ant parasitic butterflies during the Miocene aridification of Africa.

Africa has undergone a progressive aridification during the last 20 My that presumably impacted organisms and fostered the evolution of life history adaptations. We test the hypothesis that shift to living in ant nests and feeding on ant brood by larvae of phyto-predaceous Lepidochrysops butterflies was an adaptive response to the aridification of Africa that facilitated the subsequent radiation of butterflies in this genus. Using anchored hybrid enrichment we constructed a time-calibrated phylogeny for Lepidochrysops and its closest, non-parasitic relatives in the Euchrysops section (Poloyommatini). We estimated ancestral areas across the phylogeny with process-based biogeographical models and diversification rates relying on time-variable and clade-heterogeneous birth-death models. The Euchrysops section originated with the emerging Miombo woodlands about 22 million years ago (Mya) and spread to drier biomes as they became available in the late Miocene. The diversification of the non-parasitic lineages decreased as aridification intensified around 10 Mya, culminating in diversity decline. In contrast, the diversification of the phyto-predaceous Lepidochrysops lineage proceeded rapidly from about 6.5 Mya when this unusual life history likely first evolved. The Miombo woodlands were the cradle for diversification of the Euchrysops section, and our findings are consistent with the hypothesis that aridification during the Miocene selected for a phyto-predaceous life history in species of Lepidochrysops, with ant nests likely providing caterpillars a safe refuge from fire and a source of food when vegetation was scarce.

Goldenrod herbariomics: Hybrid-sequence capture reveals the phylogeny of Solidago.

PREMISE: The phylogenetic relationships among the ca. 138 species of goldenrods (Solidago; Asteraceae) have been difficult to infer due to species richness, and shallow interspecific genetic divergences. This study aims to overcome these obstacles by combining extensive sampling of goldenrod herbarium specimens with the use of a custom Solidago hybrid-sequence capture probe set. METHODS: A set of tissues from herbarium samples comprising ca. 90% of Solidago species was assembled and DNA was extracted. A custom hybrid-sequence capture probe set was designed, and data from 854 nuclear regions were obtained and analyzed from 209 specimens. Maximum likelihood and coalescent approaches were used to estimate the genus phylogeny for 157 diploid samples. RESULTS: Although DNAs from older specimens were both more fragmented and produced fewer sequencing reads, there was no relationship between specimen age and our ability to obtain sufficient data at the target loci. The Solidago phylogeny was generally well-supported, with 88/155 (57%) nodes receiving ≥95% bootstrap support. Solidago was supported as monophyletic, with Chrysoma pauciflosculosa identified as sister. A clade comprising Solidago ericameriodes, Solidago odora, and Solidago chapmanii was identified as the earliest diverging Solidago lineage. The previously segregated genera Brintonia and Oligoneuron were identified as placed well within Solidago. These and other phylogenetic results were used to establish four subgenera and fifteen sections within the genus. CONCLUSIONS: The combination of expansive herbarium sampling and hybrid-sequence capture data allowed us to quickly and rigorously establish the evolutionary relationships within this difficult, species-rich group.

The population genetics of speciation by cascade reinforcement.

Species interactions drive diverse evolutionary outcomes. Speciation by cascade reinforcement represents one example of how species interactions can contribute to the proliferation of species. This process occurs when the divergence of mating traits in response to selection against interspecific hybridization incidentally leads to reproductive isolation among populations of the same species. Here, we investigated the population genetic outcomes of cascade reinforcement in North American chorus frogs (Hylidae: Pseudacris). Specifically, we estimated the frequency of hybridization among three taxa, assessed genetic structure within the focal species, P. feriarum, and ascertained the directionality of gene flow within P. feriarum across replicated contact zones via coalescent modeling. Through field observations and preliminary experimental crosses, we assessed whether hybridization is possible under natural and laboratory conditions. We found that hybridization occurs among P. feriarum and two conspecifics at a low rate in multiple contact zones, and that gene flow within the former species is unidirectional from allopatry into sympatry with these other species in three of four contact zones studied. We found evidence of substantial genetic structuring within P. feriarum including a divergent western allopatric cluster, a behaviorally-distinct sympatric South Carolina cluster, and several genetically-overlapping clusters from the remainder of the distribution. Furthermore, we found sub-structuring between reinforced and nonreinforced populations in the two most intensely-sampled contact zones. Our literature review indicated that P. feriarum hybridizes with at least five heterospecifics at the periphery of its range providing a mechanism for further intraspecific diversification. This work strengthens the evidence for cascade reinforcement in this clade, revealing the geographic and genetic landscape upon which this process can contribute to the proliferation of species.

The use of Anchored Hybrid Enrichment data to resolve higher-level phylogenetic relationships: A proof-of-concept applied to Asterales (Eudicotyledoneae; Angiosperms).

Anchored Hybrid Enrichment (AHE) is a tool for capturing orthologous regions of the nuclear genome shared in low or single copy across lineages. Despite the increasing number of studies using this method, its usefulness to estimate relationships at deeper taxonomic levels in plants has not been fully explored. Here we present a proof of concept about the performance of nuclear loci obtained with AHE to infer phylogenetic relationships and explore the use of gene sampling schemes to estimate divergence times in Asterales. We recovered low-copy nuclear loci using the AHE method from herbarium material and silica-preserved samples. Maximum likelihood, Bayesian inference, and coalescence approaches were used to reconstruct phylogenomic relationships. Dating analyses were conducted under a multispecies coalescent approach by jointly inferring species tree and divergence times with random gene sampling schemes and multiple calibrations. We recovered 403 low-copy nuclear loci for 63 species representing nine out of eleven families of Asterales. Phylogenetic hypotheses were congruent among the applied methods and previously published results. Analyses with concatenated datasets were strongly supported, but coalescence-based analyses showed low support for the phylogenetic position of families Argophyllaceae and Alseuosmiaceae. Estimated family ages were congruent among gene sampling schemes, with the mean age for Asterales around 130 Myr. Our study documents the usefulness of AHE for resolving phylogenetic relationships at deep phylogenetic levels in Asterales. Observed phylogenetic inconsistencies were possibly due to the non-inclusion of families Phellinceae and Pentaphragmataceae. Random gene sampling schemes produced consistent age estimates with coalescence and species tree relaxed clock approaches.

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.

Phylogenomics of trophically diverse cichlids disentangles processes driving adaptive radiation and repeated trophic transitions.

Cichlid fishes of the tribe Tropheini are a striking case of adaptive radiation, exemplifying multiple trophic transitions between herbivory and carnivory occurring in sympatry with other established cichlid lineages. Tropheini evolved highly specialized eco-morphologies to exploit similar trophic niches in different ways repeatedly and rapidly. To better understand the evolutionary history and trophic adaptations of this lineage, we generated a dataset of 532 targeted loci from 21 out of the 22 described Tropheini species. We resolved the Tropheini into seven monophyletic genera and discovered one to be polyphyletic. The polyphyletic genus, Petrochromis, represents three convergent origins of the algae grazing trophic specialization. This repeated evolution of grazing may have been facilitated by adaptive introgression as we found evidence for gene flow among algae grazing genera. We also found evidence of gene flow among algae browsing genera, but gene flow was restricted between herbivorous and carnivorous genera. Furthermore, we observed no evidence supporting a hybrid origin of this radiation. Our molecular evolutionary analyses suggest that opsin genes likely evolved in response to selection pressures associated with trophic ecology in the Tropheini. We found surprisingly little evidence of positive selection in coding regions of jaw-shaping genes in this trophically diverse lineage. This suggests low degrees of freedom for further change in these genes, and possibly a larger role for regulatory variation in driving jaw adaptations. Our study emphasizes Tropheini cichlids as an important model for studying the evolution of trophic specialization and its role in speciation.

Detecting and Removing Sample Contamination in Phylogenomic Data: An Example and its Implications for Cicadidae Phylogeny (Insecta: Hemiptera).

Contamination of a genetic sample with DNA from one or more nontarget species is a continuing concern of molecular phylogenetic studies, both Sanger sequencing studies and next-generation sequencing studies. We developed an automated pipeline for identifying and excluding likely cross-contaminated loci based on the detection of bimodal distributions of patristic distances across gene trees. When contamination occurs between samples within a data set, a comparison between a contaminated sample and its contaminant taxon will yield bimodal distributions with one peak close to zero patristic distance. This new method does not rely on a priori knowledge of taxon relatedness nor does it determine the causes(s) of the contamination. Exclusion of putatively contaminated loci from a data set generated for the insect family Cicadidae showed that these sequences were affecting some topological patterns and branch supports, although the effects were sometimes subtle, with some contamination-influenced relationships exhibiting strong bootstrap support. Long tip branches and outlier values for one anchored phylogenomic pipeline statistic (AvgNHomologs) were correlated with the presence of contamination. While the anchored hybrid enrichment markers used here, which target hemipteroid taxa, proved effective in resolving deep and shallow level Cicadidae relationships in aggregate, individual markers contained inadequate phylogenetic signal, in part probably due to short length. The cleaned data set, consisting of 429 loci, from 90 genera representing 44 of 56 current Cicadidae tribes, supported three of the four sampled Cicadidae subfamilies in concatenated-matrix maximum likelihood (ML) and multispecies coalescent-based species tree analyses, with the fourth subfamily weakly supported in the ML trees. No well-supported patterns from previous family-level Sanger sequencing studies of Cicadidae phylogeny were contradicted. One taxon (Aragualna plenalinea) did not fall with its current subfamily in the genetic tree, and this genus and its tribe Aragualnini is reclassified to Tibicininae following morphological re-examination. Only subtle differences were observed in trees after the removal of loci for which divergent base frequencies were detected. Greater success may be achieved by increased taxon sampling and developing a probe set targeting a more recent common ancestor and longer loci. Searches for contamination are an essential step in phylogenomic analyses of all kinds and our pipeline is an effective solution. [Auchenorrhyncha; base-composition bias; Cicadidae; Cicadoidea; Hemiptera; phylogenetic conflict.].

Localized Phylogenetic Discordance Among Nuclear Loci Due to Incomplete Lineage Sorting and Introgression in the Family of Cotton and Cacao (Malvaceae).

The economically important cotton and cacao family (Malvaceae sensu lato) have long been recognized as a monophyletic group. However, the relationships among some subfamilies are still unclear as discordant phylogenetic hypotheses keep arising when different sources of molecular data are analyzed. Phylogenetic discordance has previously been hypothesized to be the result of both introgression and incomplete lineage sorting (ILS), but the extent and source of discordance have not yet been evaluated in the context of loci derived from massive sequencing strategies and for a wide representation of the family. Furthermore, no formal methods have been applied to evaluate if the detected phylogenetic discordance among phylogenomic datasets influences phylogenetic dating estimates of the concordant relationships. The objective of this research was to generate a phylogenetic hypothesis of Malvaceae from nuclear genes, specifically we aimed to (1) investigate the presence of major discordance among hundreds of nuclear gene histories of Malvaceae; (2) evaluate the potential source of discordance; and (3) examine whether discordance and loci heterogeneity influence on time estimates of the origin and diversification of subfamilies. Our study is based on a comprehensive dataset representing 96 genera of the nine subfamilies and 268 nuclear loci. Both concatenated and coalescence-based approaches were followed for phylogenetic inference. Using branch lengths and topology, we located the placement of introgression events to directly evaluate whether discordance is due to introgression rather than ILS. To estimate divergence times, concordance and molecular rate were considered. We filtered loci based on congruence with the species tree and then obtained the molecular rate of each locus to distribute them into three different sets corresponding to shared molecular rate ranges. Bayesian dating was performed for each of the different sets of loci with the same parameters and calibrations. Phylogenomic discordance was detected between methods, as well as gene histories. At deep coalescent times, we found discordance in the position of five subclades probably due to ILS and a relatively small proportion of introgression. Divergence time estimation with each set of loci generated overlapping clade ages, indicating that, even with different molecular rate and gene histories, calibrations generally provide a strong prior.

Investigating the utility of Anchored Hybrid Enrichment data to investigate the relationships among the Killifishes (Actinopterygii: Cyprinodontiformes), a globally distributed group of fishes.

The Killifishes (Cyprinodontiformes) are a diverse and well-known group of fishes that contains sixteen families inclusive of Anablepidae, Aphaniidae Aplocheilidae, Cubanichthyidae, Cyprinodontidae, Fluviphylacidae, Fundulidae, Goodeidae, Nothobranchiidae, Orestiidae, Pantanodontidae, Poeciliidae, Procatopodidae, Profundulidae, Rivulidae, and Valenciidae and more than 1,200 species that are globally distributed in tropical and temperate, freshwater and estuarine habitats. The evolutionary relationships among the families within the group, based on different molecular and morphological data sets, have remained uncertain. Therefore, the objective of this study was to use a targeted approach, anchored hybrid enrichment, to investigate the phylogenetic relationships among the families within the Cyprindontiformes. This study included more than 100 individuals, representing all sixteen families within the Cyprinodontiformes, including many recently diagnosed families. We recovered an average of 244 loci per individual. These data were submitted to phylogenetic analyses (RaxML and ASTRAL) and although we recovered many of the same relationships as in previous studies of the group, several novel sets of relationships for other families also were recovered. In addition, two well-established clades (Suborders Cyprinodontoidei and Aplocheilodei) were recovered as monophyletic and are in agreement with most previous studies. We also assessed the degree of gene tree discordance in our dataset to evaluate support for alternative topological hypotheses for interfamilial relationships within the Cyprinodontiformes using a variety of different analyses. The results from this study will provide a robust, historical framework needed to investigate a plethora of biogeographic, taxonomic, ecological, and physiological questions for this group of fishes.

Candidate-species delimitation in Desmognathus salamanders reveals gene flow across lineage boundaries, confounding phylogenetic estimation and clarifying hybrid zones.

Dusky Salamanders (genus Desmognathus) currently comprise only 22 described, extant species. However, recent mitochondrial and nuclear estimates indicate the presence of up to 49 candidate species based on ecogeographic sampling. Previous studies also suggest a complex history of hybridization between these lineages. Studies in other groups suggest that disregarding admixture may affect both phylogenetic inference and clustering-based species delimitation. With a dataset comprising 233 Anchored Hybrid Enrichment (AHE) loci sequenced for 896 Desmognathus specimens from all 49 candidate species, we test three hypotheses regarding (i) species-level diversity, (ii) hybridization and admixture, and (iii) misleading phylogenetic inference. Using phylogenetic and population-clustering analyses considering gene flow, we find support for at least 47 candidate species in the phylogenomic dataset, some of which are newly characterized here while others represent combinations of previously named lineages that are collapsed in the current dataset. Within these, we observe significant phylogeographic structure, with up to 64 total geographic genetic lineages, many of which hybridize either narrowly at contact zones or extensively across ecological gradients. We find strong support for both recent admixture between terminal lineages and ancient hybridization across internal branches. This signal appears to distort concatenated phylogenetic inference, wherein more heavily admixed terminal specimens occupy apparently artifactual early-diverging topological positions, occasionally to the extent of forming false clades of intermediate hybrids. Additional geographic and genetic sampling and more robust computational approaches will be needed to clarify taxonomy, and to reconstruct a network topology to display evolutionary relationships in a manner that is consistent with their complex history of reticulation.

The Complex History of Genome Duplication and Hybridization in North American Gray Treefrogs.

Polyploid speciation has played an important role in evolutionary history across the tree of life, yet there remain large gaps in our understanding of how polyploid species form and persist. Although systematic studies have been conducted in numerous polyploid complexes, recent advances in sequencing technology have demonstrated that conclusions from data-limited studies may be spurious and misleading. The North American gray treefrog complex, consisting of the diploid Hyla chrysoscelis and the tetraploid H. versicolor, has long been used as a model system in a variety of biological fields, yet all taxonomic studies to date were conducted with only a few loci from nuclear and mitochondrial genomes. Here, we utilized anchored hybrid enrichment and high-throughput sequencing to capture hundreds of loci along with whole mitochondrial genomes to investigate the evolutionary history of this complex. We used several phylogenetic and population genetic methods, including coalescent simulations and testing of polyploid speciation models with approximate Bayesian computation, to determine that H. versicolor was most likely formed via autopolyploidization from a now extinct lineage of H. chrysoscelis. We also uncovered evidence of significant hybridization between diploids and tetraploids where they co-occur, and show that historical hybridization between these groups led to the re-formation of distinct polyploid lineages following the initial whole-genome duplication event. Our study indicates that a wide variety of methods and explicit model testing of polyploid histories can greatly facilitate efforts to uncover the evolutionary history of polyploid complexes.

Neurogenomic divergence during speciation by reinforcement of mating behaviors in chorus frogs (Pseudacris).

BACKGROUND: Species interactions can promote mating behavior divergence, particularly when these interactions are costly due to maladaptive hybridization. Selection against hybridization can indirectly cause evolution of reproductive isolation within species, a process termed cascade reinforcement. This process can drive incipient speciation by generating divergent selection pressures among populations that interact with different species assemblages. Theoretical and empirical studies indicate that divergent selection on gene expression networks has the potential to increase reproductive isolation among populations. After identifying candidate synaptic transmission genes derived from neurophysiological studies in anurans, we test for divergence of gene expression in a system undergoing cascade reinforcement, the Upland Chorus Frog (Pseudacris feriarum). RESULTS: Our analyses identified seven candidate synaptic transmission genes that have diverged between ancestral and reinforced populations of P. feriarum, including five that encode synaptic vesicle proteins. Our gene correlation network analyses revealed four genetic modules that have diverged between these populations, two possessing a significant concentration of neurotransmission enrichment terms: one for synaptic membrane components and the other for metabolism of the neurotransmitter nitric oxide. We also ascertained that a greater number of genes have diverged in expression by geography than by sex. Moreover, we found that more genes have diverged within females as compared to males between populations. Conversely, we observed no difference in the number of differentially-expressed genes within the ancestral compared to the reinforced population between the sexes. CONCLUSIONS: This work is consistent with the idea that divergent selection on mating behaviors via cascade reinforcement contributed to evolution of gene expression in P. feriarum. Although our study design does not allow us to fully rule out the influence of environment and demography, the fact that more genes diverged in females than males points to a role for cascade reinforcement. Our discoveries of divergent candidate genes and gene networks related to neurotransmission support the idea that neural mechanisms of acoustic mating behaviors have diverged between populations, and agree with previous neurophysiological studies in frogs. Increasing support for this hypothesis, however, will require additional experiments under common garden conditions. Our work points to the importance of future replicated and tissue-specific studies to elucidate the relative contribution of gene expression divergence to the evolution of reproductive isolation during incipient speciation.

Gene Flow and Diversification in Himalopsyche martynovi Species Complex (Trichoptera: Rhyacophilidae) in the Hengduan Mountains.

The Hengduan Mountains are one of the most species-rich mountainous areas in the world. The origin and evolution of such a remarkable biodiversity are likely to be associated with geological or climatic dynamics, as well as taxon-specific biotic processes (e.g., hybridization, polyploidization, etc.). Here, we investigate the mechanisms fostering the diversification of the endemic Himalopsyche martynovi complex, a poorly known group of aquatic insects. We used multiple allelic datasets generated from 691 AHE loci to reconstruct species and RaxML phylogenetic trees. We selected the most reliable phylogenetic tree to perform network and gene flow analyses. The phylogenetic reconstructions and network analysis identified three clades, including H. epikur, H. martynovi sensu stricto and H. cf. martynovi. Himalopsyche martynovi sensu stricto and H. cf. martynovi present an intermediate morphology between H. epikur and H. viteceki, the closest known relative to the H. martynovi-complex. The gene flow analysis revealed extensive gene flow among these lineages. Our results suggest that H. viteceki and H. epikur are likely to have contributed to the evolution of H. martynovi sensu stricto and H. cf. martynovi via gene flow, and thus, our study provides insights in the diversification process of a lesser-known ecological group, and hints at the potential role of gene flow in the emergence of biological novelty in the Hengduan Mountains.

Gene flow in phylogenomics: Sequence capture resolves species limits and biogeography of Afromontane forest endemic frogs from the Cameroon Highlands.

Puddle frogs of the Phrynobatrachus steindachneri species complex are a useful group for investigating speciation and phylogeography in Afromontane forests of the Cameroon Volcanic Line, western Central Africa. The species complex is represented by six morphologically relatively cryptic mitochondrial DNA lineages, only two of which are distinguished at the species level - southern P. jimzimkusi and Lake Oku endemic P. njiomock, leaving the remaining four lineages identified as 'P. steindachneri'. In this study, the six mtDNA lineages are subjected to genomic sequence capture analyses and morphological examination to delimit species and to study biogeography. The nuclear DNA data (387 loci; 571,936 aligned base pairs) distinguished all six mtDNA lineages, but the topological pattern and divergence depths supported only four main clades: P. jimzimkusi, P. njiomock, and only two divergent evolutionary lineages within the four 'P. steindachneri' mtDNA lineages. One of the two lineages is herein described as a new species, P. amieti sp. nov. Reticulate evolution (hybridization) was detected within the species complex with morphologically intermediate hybrid individuals placed between the parental species in phylogenomic analyses, forming a ladder-like phylogenetic pattern. The presence of hybrids is undesirable in standard phylogenetic analyses but is essential and beneficial in the network multispecies coalescent. This latter approach provided insight into the reticulate evolutionary history of these endemic frogs. Introgressions likely occurred during the Middle and Late Pleistocene climatic oscillations, due to the cyclic connections (likely dominating during cold glacials) and separations (during warm interglacials) of montane forests. The genomic phylogeographic pattern supports the separation of the southern (Mt. Manengouba to Mt. Oku) and northern mountains at the onset of the Pleistocene. Further subdivisions occurred in the Early Pleistocene, separating populations from the northernmost (Tchabal Mbabo, Gotel Mts.) and middle mountains (Mt. Mbam, Mt. Oku, Mambilla Plateau), as well as the microendemic lineage restricted to Lake Oku (Mt. Oku). This unique model system is highly threatened as all the species within the complex have exhibited severe population declines in the past decade, placing them on the brink of extinction. In addition, Mount Oku is identified to be of particular conservation importance because it harbors three species of this complex. We, therefore, urge for conservation actions in the Cameroon Highlands to preserve their diversity before it is too late.

Tempo and mode of evolution of oryzomyine rodents (Rodentia, Cricetidae, Sigmodontinae): A phylogenomic approach.

The tribe Oryzomyini is an impressive group of rodents, comprising 30 extant genera and an estimated 147 species. Recent remarkable advances in the understanding of the diversity, taxonomy and systematics of the tribe have mostly derived from analyses of single or few genetic markers. However, the evolutionary history and biogeography of Oryzomyini, its origin and diversification across the Neotropics, remain unrevealed. Here we use a multi-locus dataset (over 400 loci) obtained through anchored phylogenomics to provide a genome-wide phylogenetic hypothesis for Oryzomyini and to investigate the tempo and mode of its evolution. Species tree and supermatrix analyses produced topologies with strong support for most branches, with all genera confirmed as monophyletic, a result that previous studies failed to obtain. Our analyses also corroborated the monophyly and phylogenetic relationship of three main clades of Oryzomyini (B, C and D). The origin of the tribe is estimated to be in the Miocene (8.93-5.38 million years ago). The cladogenetic events leading to the four main clades occurred during the late Miocene and early Pliocene and most speciation events in the Pleistocene. Geographic range estimates suggested an east of Andes origin for the ancestor of oryzomyines, most likely in the Boreal Brazilian region, which includes the north bank of Rio Amazonas and the Guiana Shield. Oryzomyini rodents are an autochthonous South America radiation, that colonized areas and dominions of this continent mainly by dispersal events. The evolutionary history of the tribe is deeply associated with the Andean cordillera and the landscape history of Amazon basin.

Phylogenomics, biogeography and taxonomic revision of New Guinean pythons (Pythonidae, Leiopython) harvested for international trade.

The large and enigmatic New Guinean pythons in the genus Leiopython are harvested from the wild to supply the international trade in pets. Six species are currently recognized (albertisii, biakensis, fredparkeri, huonensis, meridionalis, montanus) but the taxonomy of this group has been controversial. We combined analysis of 421 nuclear loci and complete mitochondrial genomes with morphological data to construct a detailed phylogeny of this group, understand their biogeographic patterns and establish the systematic diversity of this genus. Our molecular genetic data support two major clades, corresponding to L. albertisii and L. fredparkeri, but offer no support for the other four species. Our morphological data also only support two species. We therefore recognize L. albertisii and L. fredparkeri as valid species and place L. biakensis, L. meridionalis, L. huonensis and L. montanus into synonymy. We found that L. albertisii and L. fredparkeri are sympatric in western New Guinea; an atypical pattern compared to other Papuan species complexes in which the distributions of sister taxa are partitioned to the north and south of the island's central mountain range. For the purpose of conservation management, overestimation of species diversity within Leiopython has resulted in the unnecessary allocation of resources that could have been expended elsewhere. We strongly caution against revising the taxonomy of geographically widespread species groups when little or no molecular genetic data and only small morphological samples are available.