Dispersal constraints for the conservation of the grassland herb Thymus pulegioides L. in a highly fragmented agricultural landscape

Why are some plant species missing from restorations? A diagnostic tool for temperate grassland ecosystems

The U.N. Decade on Ecosystem Restoration aims to accelerate actions to prevent, halt, and reverse the degradation of ecosystems, and re-establish ecosystem functioning and species diversity. The practice of ecological restoration has made great progress in recent decades, as has recognition of the importance of species diversity to maintaining the long-term stability and functioning of restored ecosystems. Restorations may also focus on specific species to fulfill needed functions, such as supporting dependent wildlife or mitigating extinction risk. Yet even in the most carefully planned and managed restoration, target species may fail to germinate, establish, or persist. To support the successful reintroduction of ecologically and culturally important plant species with an emphasis on temperate grasslands, we developed a tool to diagnose common causes of missing species, focusing on four major categories of filters, or factors: genetic, biotic, abiotic, and planning & land management. Through a review of the scientific literature, we propose a series of diagnostic tests to identify potential causes of failure to restore target species, and treatments that could improve future outcomes. This practical diagnostic tool is meant to strengthen collaboration between restoration practitioners and researchers on diagnosing and treating causes of missing species in order to effectively restore them.

Diagnostic traits of medicinal herbal raw material of species of Thymus genus

The paper presents the peculiarities of morphological-anatomical structure of the organs, which are diagnostic traits of herbal raw materials (HRM) of the commonest species of Thymus L. genus in the moderate climatic zone. We determined that the studied species develop a subshrub life form, which grows monopodially in Th. pulegioides and Th. marschallianus, and sympodially with mono-, di- and polycyclic types of monocarpic shoots in Th. serpyllum. Inflorescence is of thyrsoid type with opposite partial inflorescences, which are constituents of simple dichasia with monochasia. Macroscopic and microscopic diagnostic features of the HRM are structure and pubescence on the stem, leaves and flowers, the anatomical structure of which was studied on 20 µm thick transversal sections using a light microscope. In Th. pulegioides, stems are tetrahedral, pubescent on ribs with unicellular and two-cellular elbow-shaped hairs. Leaves are ovoid, covered by multiangular epidermis that bears diacytic stromas, sharpened capitate unicellular and two-cellular hairs and 10–12 cellular essential oil glandules. In Th. marschallianus, the stems are poorly tetrahedral, rounded, pubescent on the entire surface. Leaves are elliptic, the cells of the epidermis are elongated, significantly tortuous, with 10–12 cellular glandules, diacytic stromas, capitate and unicellular hairs. In Th. serpyllum, the stems are cylindric, pubescent all round. The leaves are elongated-elliptic, epidermis cells are oval, tortuous, stromas are diacytic, essential oil glandules are 8–10 cellular, number of papilla-like hairs is low. The petioles and lamina base of the studied species are pubescent on the sides with short, coned and elbow-shaped, 2–3 cellular hairs, among which there are long, 4–8 cellular hairs; the hairs in Th. serpyllum are multicellular, interrupted. In mesophyll, there are schizogenous essential oil reservoirs. In Th. marschallianus and Th. pulegioídes, the calyx is campanulate, bilabiate, and pubescent. The flower corolla is purple-violet, bilabiate, has tube and outward bend, pubescent inside with coned unicellular hairs, has essential oil glandules and glandular capitate hairs, and pubescence in the fauces comprises long unicellular hairs. In Th. pulegioídes, cells of the corolla epidermis are multiangular-shaped with insignificantly wavy walls, in Th. marschallianus ‒ rectangular with significantly wavy walls. Cells of the tube epidermis are rectangular, tortuous. Surface of the corolla of Th. serpyllum is pubescent on both sides with short, cone-like and three-cellular, interrupted hairs, and also capitate hairs, and has essential oil glandules. Epidermis cells are multi-angular, tubes – rectangular and narrow. The obtained results may be used for diagnostics of HRM of morphologically similar species during their preparation.

Patterns of genomic divergence in sympatric and allopatric speciation of three Mihoutao (Actinidia) species

Isolation by geographic distance is involved in the formation of potential genomic islands and the divergence of genomes, which often result in speciation. The mechanisms of sympatric and allopatric speciation associated with geographic distance remain a topic of interest to evolutionary biologists. Here, we examined genomic divergence in three Actinidia species from large-scale sympatric and allopatric regions. Genome sequence data revealed that hexaploid Actinidia deliciosa originated from Actinidia chinensis and supported the speciation-with-gene-flow model in sympatric regions. The common ancestor of Actinidia setosa and A. deliciosa migrated from the mainland to the Taiwan Island ~2.91 Mya and formed A. setosa ~0.92 Mya, and the speciation of A. setosa is consistent with the divergence-after-speciation model with selective sweeps. Geographic isolation resulted in population contraction and accelerated the process of lineage sorting and speciation due to natural selection. Genomic islands contained genes associated with organ development, local adaptation, and stress resistance, indicating selective sweeps on a specific set of traits. Our results highlight the patterns of genomic divergence in sympatric and allopatric speciation, with the mediation of geographic isolation in the formation of genomic islands during Actinidia speciation.

Scale-dependent effects of habitat fragmentation on the genetic diversity of Actinidia chinensis populations in China

Spatial scale partly explains the differentiated effects of habitat fragmentation on plant biodiversity, but the mechanisms remain unclear. To investigate the effects of habitat fragmentation on genetic diversity at different scales, we sampled Actinidia chinensis Planch. at broad and fine scales, China. The broad-scale sampling included five mountain populations and one oceanic island population (Zhoushan Archipelago), and the fine-scale sampling covered 11 lake islands and three neighboring land populations in Thousand-Island Lake (TIL). These populations were genotyped at 30 microsatellite loci, and genetic diversity, gene flow, and genetic differentiation were evaluated. Genetic differentiation was positively related to geographical distance at the broad scale, indicating an isolation-by-distance effect of habitat fragmentation on genetic diversity. The oceanic population differed from the mainland populations and experienced recent bottleneck events, but it showed high gene flow with low genetic differentiation from a mountain population connected by the Yangtze River. At the fine scale, no negative genetic effects of habitat fragmentation were found because seed dispersal with water facilitates gene flow between islands. The population size of A. chinensis was positively correlated with the area of TIL islands, supporting island biogeography theory, but no correlation was found between genetic diversity and island area. Our results highlight the scale-dependent effects of habitat fragmentation on genetic diversity and the importance of connectivity between island-like isolated habitats at both the broad and fine scales.