Lineage and role in integrative taxonomy of a heterotrophic orchid complex

Refining taxonomic identification of microalgae through molecular and genetic evolution: a case study of Prorocentrum lima and Prorocentrum arenarium

Species delimitation based on lineage definition has become increasingly popular. However, these methods have been limited, especially for species that lack genomic data and are morphologically similar. The trickiest part for the species identification is that the interspecific and intraspecific boundaries are vague. Taking Prorocentrum (Dinophyta) as an example, analysis of cell morphology, growth, and toxin synthesis in both species of P. lima and P. arenarium does not provide a reliable basis for species delineation. However, through phylogenetic and genetic distance analyses of their ITS and LSU sequences, establishment of evolutionary tree based on orthologous gene sequences, and combining the results of automatic barcode gap discovery and Poisson tree processes models, it was sustained that P. arenarium does not belong to the P. lima complex and should be considered as an independent species. Interspecies genetic evolution analysis revealed that P. lima and P. arenarium may contribute to evolutionary direction that favors combating reverse environmental factors. In P. lima, viral invasion may be one of the reasons for its large genome size. In the study, P. lima complex has been selected as an example to enhance the taxonomic identification of microalgae through molecular and genetic evolution, offering valuable insights into refining taxonomic identification and promoting microbial biodiversity research in other species.IMPORTANCEMicroalgae, especially the species known as Prorocentrum, have received significant attention due to their ability to trigger harmful algal blooms and produce toxins. However, the boundaries between species and within species are ambiguous. Clear and comprehensive species delineation indicates that Prorocentrum arenarium should be considered as an independent species, separate from the Prorocentrum lima complex. Improving the classification and identification of microalgae through molecular and genetic evolution will provide reference points for other cryptic species. Prorocentrum occupy multiple ecological niches in marine environments, and studying their evolutionary direction contributes to understanding their ecological adaptations and community succession.

Spiranthes hachijoensis (Orchidaceae), a new species within the S. sinensis species complex in Japan, based on morphological, phylogenetic, and ecological evidence

The systematics of the Old World Spiranthes sinensis (Pers.) Ames species complex (Orchidaceae) has been complicated by its wide distribution and morphological variations. Within the species complex, S. australis Lindl. has been generally accepted as the only Spiranthes Rich. species distributed on the Japanese mainland. The present study provides morphological, phylogenetic, and ecological evidence for the recognition of S. hachijoensis Suetsugu as a new species of the S. sinensis species complex on the Japanese mainland. Spiranthes hachijoensis is morphologically similar to S. hongkongensis S.Y. Hu & Barretto and S. nivea T.P. Lin & W.M. Lin, sharing a degenerated rostellum, pollinia without a viscidium, and distinctly trilobed stigma. However, the taxon can be morphologically distinguished from S. hongkongensis by its glabrous rachis, ovaries, and sepals, and from S. nivea by its papillate labellum disc, larger papillate basal labellum callosities, and glabrous rachis, ovaries, and sepals. The autogamy and flowering phenology (i.e., earlier flowering) of S. hachijoensis are most likely responsible for premating isolation from the sympatric S. australis. A MIG-seq-based high-throughput molecular analysis indicated that the genetic difference between S. hachijoensis and its putative sister species S. sinensis is comparable to, or even greater than, the genetic difference between pairs of other species within the S. sinensis species complex. Our multifaceted approach strongly supports the recognition of S. hachijoensis as a morphologically, phenologically, phylogenetically, and ecologically distinct species.

Monotropastrum kirishimense (Ericaceae), a new mycoheterotrophic plant from Japan based on multifaceted evidence

Due to their reduced morphology, non-photosynthetic plants have been one of the most challenging groups to delimit to species level. The mycoheterotrophic genus Monotropastrum, with the monotypic species M. humile, has been a particularly taxonomically challenging group, owing to its highly reduced vegetative and root morphology. Using integrative species delimitation, we have focused on Japanese Monotropastrum, with a special focus on an unknown taxon with rosy pink petals and sepals. We investigated its flowering phenology, morphology, molecular identity, and associated fungi. Detailed morphological investigation has indicated that it can be distinguished from M. humile by its rosy pink tepals and sepals that are generally more numerous, elliptic, and constantly appressed to the petals throughout its flowering period, and by its obscure root balls that are unified with the surrounding soil, with root tips that hardly protrude. Based on genome-wide single-nucleotide polymorphisms, molecular data has provided clear genetic differentiation between this unknown taxon and M. humile. Monotropastrum humile and this taxon are associated with different Russula lineages, even when they are sympatric. Based on this multifaceted evidence, we describe this unknown taxon as the new species M. kirishimense. Assortative mating resulting from phenological differences has likely contributed to the persistent sympatry between these two species, with distinct mycorrhizal specificity.

Morphological, ecological, and molecular phylogenetic approaches reveal species boundaries and evolutionary history of Goodyeracrassifolia (Orchidaceae, Orchidoideae) and its closely related taxa

Species delimitation within the genus Goodyera is challenging among closely related species, because of phenotypic plasticity, ecological variation, and hybridization that confound identification methods based solely on morphology. In this study, we investigated the identity of Goodyeracrassifolia H.-J.Suh, S.-W.Seo, S.-H.Oh & T.Yukawa, morphologically similar to Goodyeraschlechtendaliana Rchb.f. This recently described taxon has long been known in Japan as "Oh-miyama-uzura" or "Gakunan" and considered a natural hybrid of G.schlechtendaliana and G.similis Blume (= G.velutina Maxim. ex Regel). Because the natural hybrid between G.schlechtendaliana and G.similis was described as G.×tamnaensis N.S.Lee, K.S.Lee, S.H.Yeau & C.S.Lee before the description of G.crassifolia, the latter might be a synonym of G.×tamnaensis. Consequently, we investigated species boundaries and evolutionary history of G.crassifolia and its closely related taxa based on multifaceted evidence. Consequently, morphological examination enabled us to distinguish G.crassifolia from other closely related species owing to the following characteristics: coriaceous leaf texture, laxly flowered inflorescence, long pedicellate ovary, large and weakly opened flowers, and column with lateral appendages. Ecological investigation indicates that G.crassifolia (2n = 60) is agamospermous, requiring neither pollinators nor autonomous self-pollination for fruit set, whereas G.schlechtendaliana (2n = 30) is neither autogamous nor agamospermous but is obligately pollinator-dependent. MIG-seq-based phylogenetic analysis provided no evidence of recent hybridization between G.crassifolia and its close congeners. Thus, molecular phylogeny reconstructed from MIG-seq data together with morphological, cytological, and ecological analyses support the separation of G.crassifolia as an independent species.