Cryptic Species Diversity and Phylogenetic Relationship in the Rust Genus Chrysomyxa from China

Chrysomyxa rusts are fungal pathogens widely distributed in the Northern hemisphere, causing spruce needle and cone rust diseases, and they are responsible for significant economic losses in China. Taxonomic delimitation and precise species identification are difficult within this genus because some characters often overlap in several species. Adequate species delimitation, enhanced by the use of DNA-based methodologies, will help to establish well-supported species boundaries and enable the identification of cryptic species. Here, we explore the cryptic species diversity in the rust genus Chrysomyxa from China. Species delimitation analyses are conducted using a distance-based method (ABGD) and three tree-based methods (GMYC, bPTP, and mPTP) based on combined LSU and ITS sequences of over 60 specimens. Although there is some incongruence among species delimitation methods, two new species and three putative cryptic species are identified. The key to 20 Chrysomyxa species distributed in China is presented. These results suggest that a significant level of undiscovered cryptic diversity is likely to be found in Chrysomyxa from China. Future studies should consider multiple analytical methods when dealing with multi-locus datasets.

Novel Approaches for Species Concepts and Delimitation in Polyploids and Hybrids

Hybridization and polyploidization are important processes for plant evolution. However, classification of hybrid or polyploid species has been notoriously difficult because of the complexity of processes and different evolutionary scenarios that do not fit with classical species concepts. Polyploid complexes are formed via combinations of allopolyploidy, autopolyploidy and homoploid hybridization with persisting sexual reproduction, resulting in many discrete lineages that have been classified as species. Polyploid complexes with facultative apomixis result in complicated net-work like clusters, or rarely in agamospecies. Various case studies illustrate the problems that apply to traditional species concepts to hybrids and polyploids. Conceptual progress can be made if lineage formation is accepted as an inevitable consequence of meiotic sex, which is established already in the first eukaryotes as a DNA restoration tool. The turnaround of the viewpoint that sex forms species as lineages helps to overcome traditional thinking of species as “units”. Lineage formation and self-sustainability is the prerequisite for speciation and can also be applied to hybrids and polyploids. Species delimitation is aided by the improved recognition of lineages via various novel -omics methods, by understanding meiosis functions, and by recognizing functional phenotypes by considering morphological-physiological-ecological adaptations.

Species Delimitation

Species delimitation is the process of determining whether a group of sampled individuals belong to the same species or to different species. The criteria used to delimit species differ across taxonomic groups, and the methods for delimiting species have changed over time, with a dramatic rise in the popularity of genomic approaches recently. Because inferred species boundaries have ramifications that extend beyond systematics, affecting all fields that rely upon species as a foundational unit, controversy has unsurprisingly surrounded not only the practices used to delimit species boundaries, but also the idea of what species are, which varies across taxa (e.g., the use of subspecies varies across the tree of life). This lack of consensus has no doubt contributed to the appeal of genetic-based delimitation. Specifically, genomic data can be collected from any taxon. Moreover, it can be analyzed in a common statistical framework (as popularized by the multispecies coalescent as a model for species delimitation). With the ease of collecting genetic data, the power of genomics, and the purported standardization for diagnosing species limits, genetic-based species delimitation is displacing traditional time-honored (albeit time-consuming) taxonomic practices of species diagnosis. It has also become an invaluable tool for discovering species in understudied groups, and genetic-based approaches are the foundation of international endeavors to generate a catalogue of DNA barcodes to illuminate biodiversity for all of life on the planet. Yet, genomic applications, and especially the sole reliance upon genetic data for inferring species boundaries, are not without their own set of challenges.

Nomenclator, geographic and stratigraphic distribution of the family Triphoridae (Mollusca: Gastropoda)

The microgastropod family Triphoridae is one of the five most diverse marine molluscan families. It likely hosts a few thousand species worldwide, but its taxonomy has long been considered challenging due to the high diversity and subtle morphological characters needed for species delimitation. Consequently, only a small portion of the species appears to be formally described to date. However, further taxonomic work should be based on robust knowledge on the numerous names introduced so far. In this perspective, we have here compiled a list of all published names that can be attributed to the fossil and extant Triphoridae. We list 958 species and 75 genus names, of which 771 are known as extant species and 146 as fossil species, 41 are known from both fossil and extant records. We provide information on type locality and horizon, type material, synonymy and homonymy. Importantly, based on the review of hundreds of publications, we provide a preliminary overview of the geographic and stratigraphic distribution.

Biodiversity Patterns and Ecological Preferences of the Photobionts Associated With the Lichen-Forming Genus Parmelia

The worldwide, ecologically relevant lichen-forming genus Parmelia currently includes 41 accepted species, of which the Parmelia sulcata group (PSULgp) and the Parmelia saxatilis group (PSAXgp) have received considerable attention over recent decades; however, phycobiont diversity is poorly known in Parmelia s. lat. Here, we studied the diversity of Trebouxia microalgae associated with 159 thalli collected from 30 locations, including nine Parmelia spp.: P. barrenoae, P. encryptata, P. ernstiae, P. mayi, P. omphalodes, P. saxatilis, P. serrana, P. submontana, and P. sulcata. The mycobionts were studied by carrying out phylogenetic analyses of the nrITS. Microalgae genetic diversity was examined by using both nrITS and LSU rDNA markers. To evaluate putative species boundaries, three DNA species delimitation analyses were performed on Trebouxia and Parmelia. All analyses clustered the mycobionts into two main groups: PSULgp and PSAXgp. Species delimitation identified 13 fungal and 15 algal species-level lineages. To identify patterns in specificity and selectivity, the diversity and abundance of the phycobionts were identified for each Parmelia species. High specificity of each Parmelia group for a given Trebouxia clade was observed; PSULgp associated only with clade I and PSAXgp with clade S. However, the degree of specificity is different within each group, since the PSAXgp mycobionts were less specific and associated with 12 Trebouxia spp., meanwhile those of PSULgp interacted only with three Trebouxia spp. Variation-partitioning analyses were conducted to detect the relative contributions of climate, geography, and symbiotic partner to phycobiont and mycobiont distribution patterns. Both analyses explained unexpectedly high portions of variability (99 and 98%) and revealed strong correlations between the fungal and algal diversity. Network analysis discriminated seven ecological clusters. Even though climatic conditions explained the largest proportion of the variation among these clusters, they seemed to show indifference relative to climatic parameters. However, the cluster formed by P. saxatilis A/P. saxatilis B/Trebouxia sp. 2/Trebouxia sp. S02/Trebouxia sp. 3A was identified to prefer cold-temperate as well as humid summer environments.