scholarly journals Species boundaries in the messy middle -- testing the hypothesis of micro-endemism in a recently diverged lineage of coastal fog desert lichen fungi

2021 ◽  
Author(s):  
Jesse Jorna ◽  
Jackson Linde ◽  
Peter Searle ◽  
Abigail Jackson ◽  
Mary-Elise Nielsen ◽  
...  
Keyword(s):  
Species Delimitation ◽  
Bayes Factor ◽  
High Throughput Sequencing ◽  
Incomplete Lineage Sorting ◽  
Cost Effective ◽  
Species Boundaries ◽  
Lineage Sorting ◽  
Coastal Fog ◽  
Genome Scale ◽  
Scale Data

Species delimitation among closely related species is challenging because traditional phenotype-based approaches, e.g., morphology, ecological, or chemical characteristics, often produce conflicting results. With the advent of high-throughput sequencing, it has become increasingly cost-effective to acquire genome-scale data which can resolve previously ambiguous species boundaries. As the availability of genome-scale data has increased, numerous species delimitation analyses, such as BPP and SNAPP+Bayes factor delimitation (BFD*), have been developed to delimit species boundaries. However, even empirical molecular species delimitation approaches can be biased by confounding evolutionary factors, e.g., hybridization/introgression and incomplete lineage sorting, and computational limitations. Here we investigate species boundaries and the potential for micro-endemism in a lineage of lichen-forming fungi, Niebla Rundel & Bowler in the family Ramalinaceae. The species delimitation models tend to support more specious groupings, but were unable to infer robust, consistent species delimitations. The results of our study highlight the problem of delimiting species, particularly in groups such as Niebla, with complex, recent phylogeographic histories.

scholarly journals Genome-wide data for effective conservation of manta and devil ray species

2018 ◽  
Author(s):  
Jane Hosegood ◽  
Emily Humble ◽  
Rob Ogden ◽  
Mark de Bruyn ◽  
Si Creer ◽  
...  
Keyword(s):  
Species Delimitation ◽  
High Throughput Sequencing ◽  
Incomplete Lineage Sorting ◽  
Conservation Strategy ◽  
Morphological Observation ◽  
Lineage Sorting ◽  
Standing Variation ◽  
Genome Wide ◽  
Genome Wide Data ◽  
Effective Conservation

AbstractPractical biodiversity conservation relies on delineation of biologically meaningful units, particularly with respect to global conventions and regulatory frameworks. Traditional approaches have typically relied on morphological observation, resulting in artificially broad delineations and non-optimal species units for conservation. More recently, species delimitation methods have been revolutionised with High-Throughput Sequencing approaches, allowing study of diversity within species radiations using genome-wide data. The highly mobile elasmobranchs, manta and devil rays (Mobulaspp.), are threatened globally by targeted and bycatch fishing pressures resulting in recent protection under several global conventions. However, a lack of global data, morphological similarities, a succession of recent taxonomic changes and ineffectual traceability measures combine to impede development and implementation of a coherent and enforceable conservation strategy. Here, we generate genome-wide Single Nucleotide Polymorphism (SNP) data from among the most globally and taxonomically representative set of mobulid tissues. The resulting phylogeny and delimitation of species units represents the most comprehensive assessment of mobulid diversity with molecular data to date. We find a mismatch between current species classifications, and optimal species units for effective conservation. Specifically, we find robust evidence for an undescribed species of manta ray in the Gulf of Mexico and show that species recently synonymised are reproductively isolated. Further resolution is achieved at the population level, where cryptic diversity is detected in geographically distinct populations, and indicates potential for future traceability work determining regional location of catch. We estimate the optimal species tree and uncover substantial incomplete lineage sorting, where standing variation in extinct ancestral populations is identified as a driver of phylogenetic uncertainty, with further conservation implications. Our study provides a framework for molecular genetic species delimitation that is relevant to wide-ranging taxa of conservation concern, and highlights the potential for genomic data to support effective management, conservation and law enforcement strategies.

scholarly journals A next generation approach to species delimitation reveals the role of hybridization in a cryptic species complex of corals

2019 ◽  
Author(s):  
Andrea M. Quattrini ◽  
Tiana Wu ◽  
Keryea Soong ◽  
Ming-Shiou Jeng ◽  
Yehuda Benayahu ◽  
...  
Keyword(s):  
Cryptic Species ◽  
Species Delimitation ◽  
Incomplete Lineage Sorting ◽  
Dna Barcode ◽  
Species Boundaries ◽  
Future Research ◽  
Species Trees ◽  
Lineage Sorting ◽  
Evolutionary Diversification

AbstractBackgroundOur ability to investigate processes shaping the evolutionary diversification of corals (Cnidaria: Anthozoa) is limited by a lack of understanding of species boundaries. Discerning species has been challenging due to a multitude of factors, including homoplasious and plastic morphological characters and the use of molecular markers that are either not informative or have not completely sorted. Hybridization can also blur species boundaries by leading to incongruence between morphology and genetics. We used traditional DNA barcoding and restriction-site associated DNA sequencing combined with coalescence-based and allele-frequency methods to elucidate species boundaries and simultaneously examine the potential role of hybridization in a speciose genus of octocoral, Sinularia.ResultsSpecies delimitations using two widely used DNA barcode markers, mtMutS and 28S rDNA, were incongruent with one another and with the morphospecies identifications, likely due to incomplete lineage sorting. In contrast, 12 of the 15 morphospecies examined formed well-supported monophyletic clades in both concatenated RAxML phylogenies and SNAPP species trees of >6,000 RADSeq loci. DAPC and Structure analyses also supported morphospecies assignments, but indicated the potential for two additional cryptic species. Three morphologically distinct species pairs could not, however, be distinguished genetically. ABBA-BABA tests demonstrated significant admixture between some of those species, suggesting that hybridization may confound species delimitation in Sinularia.ConclusionsA genomic approach can help to guide species delimitation while simultaneously elucidating the processes generating diversity in corals. Results support the hypothesis that hybridization is an important mechanism in the evolution of Anthozoa, including octocorals, and future research should examine the contribution of this mechanism in generating diversity across the coral tree of life.

scholarly journals Species delimitation in the presence of strong incomplete lineage sorting and hybridization: lessons from Ophioderma (Ophiuroidea: Echinodermata)

2017 ◽  
Author(s):  
Alexandra Anh-Thu Weber ◽  
Sabine Stöhr ◽  
Anne Chenuil
Keyword(s):  
Species Delimitation ◽  
Approximate Bayesian Computation ◽  
Incomplete Lineage Sorting ◽  
Divergence Time ◽  
Species Boundaries ◽  
Multilocus Genotype ◽  
Lineage Sorting ◽  
Multilocus Genotypes ◽  
Approximate Bayesian ◽  
Genotype Clustering

AbstractAccurate species delimitation is essential to properly assess biodiversity, but also for management and conservation purposes. Yet, it is not always trivial to accurately define species boundaries in closely related species due to incomplete lineage sorting. Additional difficulties may be caused by hybridization, now evidenced as a frequent phenomenon. The brittle star cryptic species complex Ophioderma longicauda encompasses six mitochondrial lineages, including broadcast spawners and internal brooders, yet the actual species boundaries are unknown. Here, we combined three methods to delimit species in the Ophioderma longicauda complex and to infer its divergence history: i) unsupervised species discovery based on multilocus genotypes; ii) divergence time estimation using the multi-species coalescent; iii) divergence scenario testing (including gene flow) using Approximate Bayesian Computation (ABC) methods. 30 sequence markers (transcriptome-based, mitochondrial or non-coding) for 89 O. longicauda and outgroup individuals were used. First, multivariate analyses revealed six genetic clusters, which globally corresponded to the mitochondrial lineages, yet with many exceptions, suggesting ancient hybridization events and challenging traditional mitochondrial barcoding approaches. Second, multi-species coalescent-based analyses confirmed the occurrence of six species and provided divergence time estimates, but the sole use of this method failed to accurately delimit species, highlighting the power of multilocus genotype clustering to delimit recently diverged species. Finally, Approximate Bayesian Computation showed that the most likely scenario involves hybridization between brooders and broadcasters. Our study shows that despite strong incomplete lineage sorting and past hybridization, accurate species delimitation in Ophioderma was possible using a combination of complementary methods. We propose that these methods, especially multilocus genotype clustering, may be useful to resolve other complex speciation histories.HighlightsMultivariate analysis was used for species delimitationSix Ophioderma species were delimited using nuclear and mitochondrial dataOphioderma speciation history is complex and included hybridizationMitochondrial and nuclear histories differed, challenging barcoding approachesWe propose that using multilocus genotypes can resolve complex speciation histories

scholarly journals The choices we make and the impacts they have: Machine learning and species delimitation in North American box turtles (Terrapene spp.)

2020 ◽  
Author(s):  
Bradley T. Martin ◽  
Tyler K. Chafin ◽  
Marlis R. Douglas ◽  
John S. Placyk ◽  
Roger D. Birkhead ◽  
...  
Keyword(s):  
Machine Learning ◽  
North American ◽  
Species Delimitation ◽  
Species Concept ◽  
Incomplete Lineage Sorting ◽  
Signal To Noise Ratio ◽  
Lineage Sorting ◽  
Biogeographic History ◽  
Box Turtles ◽  
A Minor

AbstractModel-based approaches that attempt to delimit species are hampered by computational limitations as well as the unfortunate tendency by users to disregard algorithmic assumptions. Alternatives are clearly needed, and machine-learning (M-L) is attractive in this regard as it functions without the need to explicitly define a species concept. Unfortunately, its performance will vary according to which (of several) bioinformatic parameters are invoked. Herein, we gauge the effectiveness of M-L-based species-delimitation algorithms by parsing 64 variably-filtered versions of a ddRAD-derived SNP dataset involving North American box turtles (Terrapene spp.). Our filtering strategies included: (A) minor allele frequencies (MAF) of 5%, 3%, 1%, and 0% (=none), and (B) maximum missing data per-individual/per-population at 25%, 50%, 75%, and 100% (=none). We found that species-delimitation via unsupervised M-L impacted the signal-to-noise ratio in our data, as well as the discordance among resolved clades. The latter may also reflect biogeographic history, gene flow, incomplete lineage sorting, or combinations thereof (as corroborated from previously observed patterns of differential introgression). Our results substantiate M-L as a viable species-delimitation method, but also demonstrate how commonly observed patterns of phylogenetic discord can seriously impact M-L-classification.

scholarly journals Excluding spatial sampling bias does not eliminate over-splitting in DNA-based species delimitation analyses

2021 ◽  
Author(s):  
Daniel Lukic ◽  
Jonas Eberle ◽  
Jana Thormann ◽  
Carolus Holzschuh ◽  
Dirk Ahrens
Keyword(s):  
Dna Barcoding ◽  
Species Delimitation ◽  
Incomplete Lineage Sorting ◽  
Sampling Bias ◽  
Lineage Sorting ◽  
Data Set ◽  
Dna Taxonomy ◽  
Operational Taxonomic Units ◽  
And Performance ◽  
Single Locality

DNA-barcoding and DNA-based species delimitation are major tools in DNA taxonomy. Sampling has been a central debate in this context, because the geographical composition of samples affect the accuracy and performance of DNA-barcoding. Performance of complex DNA-based species delimitation is to be tested under simpler conditions in absence of geographic sampling bias. Here, we present an empirical data set sampled from a single locality in a Southeast-Asian biodiversity hotspot (Laos: Phou Pan mountain). We investigate the performance of various species delimitation approaches on a megadiverse assemblage of herbivore chafer beetles (Coleoptera: Scarabaeidae) to infer whether species delimitation suffers in the same way from exaggerate infraspecific variation despite the lack of geographic genetic variation that led to inconsistencies between entities from DNA-based and morphology-based species inference in previous studies. For this purpose, a 658 bp fragment of the mitochondrial cytochrome c oxidase subunit 1 (cox1) was analysed for a total of 186 individuals of 56 morphospecies. Tree based and distance based species delimitation methods were used. All approaches showed a rather limited match ratio (max. 77%) with morphospecies. PTP and TCS prevailingly over-splitted morphospecies, while 3% clustering and ABGD also lumped several species into one entity. ABGD revealed the highest congruence between molecular operational taxonomic units (MOTUs) and morphospecies. Disagreements between morphospecies and MOTUs were discussed in the context of historically acquired geographic genetic differentiation, incomplete lineage sorting, and hybridization. The study once again highlights how important morphology still is in order to correctly interpret the results of molecular species delimitation.

scholarly journals Phylogeny and Species Delimitation of Chinese Medicago (Leguminosae) and Its Relatives Based on Molecular and Morphological Evidence

2021 ◽  
Vol 11 ◽  
Author(s):  
Jinyuan Chen ◽  
Guili Wu ◽  
Nawal Shrestha ◽  
Shuang Wu ◽  
Wei Guo ◽  
...  
Keyword(s):  
Phylogenetic Relationship ◽  
Species Delimitation ◽  
Large Scale ◽  
Incomplete Lineage Sorting ◽  
Phylogenetic Analyses ◽  
Population Based ◽  
Integrative Approach ◽  
Morphological Evidence ◽  
Sampling Errors ◽  
Lineage Sorting

Medicago and its relatives, Trigonella and Melilotus comprise the most important forage resources globally. The alfalfa selected from the wild relatives has been cultivated worldwide as the forage queen. In the Flora of China, 15 Medicago, eight Trigonella, and four Melilotus species are recorded, of which six Medicago and two Trigonella species are introduced. Although several studies have been conducted to investigate the phylogenetic relationship within the three genera, many Chinese naturally distributed or endemic species are not included in those studies. Therefore, the taxonomic identity and phylogenetic relationship of these species remains unclear. In this study, we collected samples representing 18 out of 19 Chinese naturally distributed species of these three genera and three introduced Medicago species, and applied an integrative approach by combining evidences from population-based morphological clusters and molecular data to investigate species boundaries. A total of 186 individuals selected from 156 populations and 454 individuals from 124 populations were collected for genetic and morphological analyses, respectively. We sequenced three commonly used DNA barcodes (trnH-psbA, trnK-matK, and ITS) and one nuclear marker (GA3ox1) for phylogenetic analyses. We found that 16 out of 21 species could be well delimited based on phylogenetic analyses and morphological clusters. Two Trigonella species may be merged as one species or treated as two subspecies, and Medicago falcata should be treated as a subspecies of the M. sativa complex. We further found that major incongruences between the chloroplast and nuclear trees mainly occurred among the deep diverging lineages, which may be resulted from hybridization, incomplete lineage sorting and/or sampling errors. Further studies involving a finer sampling of species associated with large scale genomic data should be employed to better understand the species delimitation of these three genera.

scholarly journals High-Throughput Sequencing of 5S-IGS rDNA in Fagus L. (Fagaceae) reveals complex evolutionary patterns and hybrid origin of modern species

2021 ◽  
Author(s):  
Simone Cardoni ◽  
Roberta Piredda ◽  
Thomas Denk ◽  
Guido W. Grimm ◽  
Aristotelis C. Papageorgiou ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Sequencing ◽  
Incomplete Lineage Sorting ◽  
Intergenic Spacer ◽  
5S Rdna ◽  
Fagus Crenata ◽  
Hybrid Origin ◽  
Lineage Sorting ◽  
Temperate Trees ◽  
Extant Species

Standard models of speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality is more complex: plant species can evolve from other species via isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi–copy, potentially multi–locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Here, we provide the first high-throughput sequencing (HTS) 5S intergenic spacer (5S – IGS) data for a lineage of wind-pollinated subtropical to temperate trees, the Fagus crenata – F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4,963 unique 5S – IGS variants reflect a long history of repeated incomplete lineage sorting and lineage mixing since the early Cenozoic of two or more paralogous-homoeologous 5S rDNA lineages. Extant species of Fagus are genetic mosaics and, at least to some part, of hybrid origin.

scholarly journals Embracing heterogeneity: Building the Tree of Life and the future of phylogenomics

2018 ◽  
Author(s):  
Gustavo A Bravo ◽  
Alexandre Antonelli ◽  
Christine D Bacon ◽  
Krzysztof Bartoszek ◽  
Mozes Blom ◽  
...  
Keyword(s):  
Large Scale ◽  
High Throughput Sequencing ◽  
Incomplete Lineage Sorting ◽  
Tree Of Life ◽  
Lineage Sorting ◽  
Modern Biology ◽  
Multispecies Coalescent ◽  
The Many ◽  
Genomic Signals ◽  
Character Mapping

Building the Tree of Life (ToL) is a major challenge of modern biology, requiring major advances in cyberinfrastructure, data collection, theory, and more. Here, we argue that phylogenomics stands to benefit by embracing the many heterogeneous genomic signals emerging from the first decade of large-scale phylogenetic analysis spawned by High-throughput sequencing (HTS). Such signals include those most commonly encountered in phylogenomic datasets, such as incomplete lineage sorting, but also those reticulate processes emerging with greater frequency, such as recombination and introgression. We suggest that methods of data acquisition and the types of markers used in phylogenomics will remain restricted until a posteriori methods of marker choice are made possible with routine whole-genome sequencing of taxa of interest. We discuss limitations and potential extensions of a major model supporting innovation in phylogenomics today, the multispecies coalescent model. Macroevolutionary models that use phylogenies, such as character mapping, often ignore the heterogeneity on which building phylogenies increasingly rely, and suggest that assimilating such heterogeneity is an important goal moving forward. Finally, we argue that an integrative cyberinfrastructure linking all steps of the process of building the ToL, from specimen acquisition in the field to publication and tracking of phylogenomic data, as well as a culture that values contributors to each step, are essential for progress.

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