DNA-based phylogenetic analyses have revealed more species in the fungal genus Skeletocutis than has traditionally been acknowledged. Here we describe two resupinate species as new: S. delicata Niemelä & Miettinen and S. exilis Miettinen & Niemelä. They are very similar to S. brevispora, S. papyracea and S. kuehneri, but differ from them mostly by their spore size and pore characteristics. The relationships of these species are discussed, and the importance of exact spore measurements is emphasized. Skeletocutis friata Niemelä & Saaren. is reduced to synonymy under Tyromyces chioneus, and misidentifications of some published records are corrected.

Lasianthus kailarsenii Poopath, Vajrodaya & Napiroon, L. tennissarimensis Napiroon, Balslev & Chayamarit and L. krabiensis Napiroon, Balslev & Chamchumroon are described as new species and illustrated. Lasianthus kailarsenii is morphologically close to L. lancilobus, but differs from it by its glabrous (not hirsute) branches and leaves, campanulate and glabrous (not obconical and hirsute) calyx, exserted (not included within the corolla tube) stigma, and 8 (not 4) pyrenes. Lasianthus tennissarimensis resembles L. robinsonii but differs from it by having lanceolate leaves that are 7.5–10 cm long (not oblong or oblong-elliptic, 12–16 cm long), its 5–6 (not 8–9) pairs of secondary veins, the calyx limbs that are narrowly lanceolate and 7–8 mm long (not linear and 2.5–4 mm long). Lasianthus krabiensis also resembles L. lancilobus but differs from it by having the abaxial leaf surface sparsely hirsute (glabrous), peduncle 1.5 mm (not 2.5–3 mm) long, and bracts shorter than calyx tube, 5–6 mm long (not longer than calyx tube, 1.5 cm long). Lasianthus oblongus which was previously known only from Peninsular Malaysia, has now been recorded in Yala (southern Thailand). A key that compares them to the related Thai Lasianthus species is also provided.

Nectar robbing by the ant Camponotus distinguendus was observed in flowers of Embothrium coccineum (Proteaceae), a tree mainly pollinated by hummingbirds. We hypothesized that robbing would reduce the amount of nectar, affecting the foraging behaviour of floral visitors and reducing seed production. Nectar robbing affected one-third of mature tree blossoms and 93.3% of trees. This reduced the amount of nectar to about half. Foraging behaviour of floral visitors included pollinating visits to consume nectar and pollen, primary and secondary nectar robbing, and nectar theft. We found no effect of nectar robbing by C. distinguendus on seed production in E. coccineum, which was sparse and completely dependent on legitimate pollinator visits, mostly performed by the green-backed firecrown Sephanoides sephaniodes. Determining the effects of nectar robbing by ants on the reproduction of plants is important to understand the dynamics of plant-animal interactions in the temperate forests of Chile.

Castanopsis dongnaiensis T.S. Hoang & V.N. Nguyen sp. nova (Fagaceae) from Dong Nai Culture and Nature Reserve, Dong Nai Province of Vietnam is described and illustrated. It is morphologically similar to C. ferox, but can be distinguished from it by its leaf margins which are serrate on 1/3 to the apex, a symmetric leaf base, cupule with decurved spines, nuts broadly conical with dense brown pubescence, and a concave nut scar, half-width of nut base.

Ardisia nutantiflora S.Z. Mao & C.M. Hu (Primulaceae), a new species from the limestone mountainous area in Guangxi Autonomous Region, southern China, is described. It resembles especially A. replicata, but can be distinguished by the flowers with longer pedicels, crowded towards apex of the rachis thus forming a pendulous corymbose raceme, and especially by the linear lanceolate calyx-lobes, 2/3 of the corolla length.

Historical (mainly 1930s) and contemporary records of 482 vascular plant species or genera of non-littoral areas of 464 islands in the archipelago of SW Finland are compared, to visualise changes in distribution patterns, and to identify environmental variables that affect the distribution of the species. The environmental variables were measured in a GIS. Logistic regression analysis was used to find variables that affect the probability of species occurrences. Results, with distribution maps, are presented for each species. The families Rosaceae, Fabaceae, Onagraceae, Sapindaceae, Oxalidaceae, Geraniaceae, Polygalaceae, Cornaceae, Apiaceae, Rhamnaceae and Rubiaceae are presented in this fourth part of the series. A synthesis of the study will be presented in the last part of this article series.

A new smut fungus from Argentina, Tilletia tripogonellae T. Denchev & Denchev (Tilletiaceae), on Tripogonella spicata (Poaceae : Cynodonteae), is described and illustrated. It differs from all other species of Tilletia by being specialized on Tripogonella. Morphologically it differs from other known species of Tilletia on host plants from the subtribe Tripogoninae (Tilletia eragrostiellae, T. poonensis, T. savilei, T. tripogonis) by having a reticulate (vs. tuberculate or echinate) spore wall. A key to the smut fungi, that infect Eragrostiella, Tripogonella, Oropetium, and Tripogon, is provided.

Salacia menglaensis J.Y. Shen, L.C. Yan & S. Landrein (Celastraceae), a new species from Huidu, Mengla, Yunnan, China, is described and illustrated. It is similar to S. korthalsiana, S. glaucifolia and S. polysperma, but differs from them by the fruit size (2–3 × 2–3 cm), with only 1–2 mature seeds and by the non-glaucous abaxial leaf surface. We also provide a conservation assessment for this rare vine species.

A new infraspecific taxon in Orchidaceae, Epipactis purpurata f. variegata Żołubak & Jakubska-Busse f. nova, with variegated leaves, is described and illustrated from Lower Silesia, Poland.

Leucas dhonimalayensis Sunojk. & K.P. Vimal (Lamiaceae) is described and illustrated as a new species from the Dhoni Hills of the Western Ghats in Peninsular India. It is placed in sect. Astrodon. The morphological characters that distinguish it from the most similar species L. beddomei and L. hirta are given. Information on the distribution and habitat ecology of L. dhonimalayensis is also provided.

We provide a new phylogeny of the tribe Rochelieae (Boraginaceae, Cynoglossoideae) using sequence data from the internal transcribed spacer region of the nuclear ribosomal DNA (nr-DNA ITS), plastid trnL(UAA) intron, trnL(UAA)-trnF(GAA) intergenic spacer (trnL-F), and rpl32-trnL(UAG) intergenic spacer (rpl32-trnL(UAG)). The analyses resolved a well-supported Rochelieae clade. Hackelia and Rochelia are monophyletic while Lappula, Eritrichium, and Lepechiniella are not. The species of Lappula form three distinct lineages across the tribe Rochelieae. Lappula sinaica is placed in a new monotypic genus Pseudolappula Khoshsokhan & Kaz. Osaloo. Lappula sessiliflora and L. drobovii are segregated from Lappula and transferred to Rochelia. The three species of Lepechiniella are transferred to Lappula. In concordance with previous studies, our analyses demonstrated that the North American species of Lappula were derived from the Asian relatives. A taxonomic treatment of Lappula, Rochelia and Pseudolappula as well as a key to the genera of the tribe are provided.

We studied seedling dynamics and population structure of the invasive, monocarpic perennial Heracleum sosnowskyi (Apiaceae) in different habitats. The lowest seedling density was found in the managed anthropogenic herb stand, whereas in the unmanaged anthropogenic herb stand, mean seedling density was the highest and significantly different from that at the other studied sites. In all populations, a small fraction of the individuals were generative. In the managed anthropogenic herb stands, mature vegetative and generative individuals dominated in the population, whereas the unmanaged anthropogenic herb stands were dominated by immature vegetative plants. Our study confirmed that long-term abandonment of mesic meadows promotes development of denser stands of H. sosnowskyi. A short-time extensive management can reduce the density of monocarpic invasive species populations, especially their seedlings and immature vegetative plants. Significant reduction in seedling numbers occurred between April and May, with high seedling mortality rates in the following months until September. The mean seedling survival rate was 4.15%.

A new generic name, Scandosorbus Sennikov, is validly published to replace Borkhausenia Sennikov & Kurtto 2017, which is an illegitimate later near-homonym of Borckhausenia Roth 1800. New combinations are provided for the only species of the genus (B. intermedia) and its hybrid with Sorbus aucuparia.

Villaria marinduquensis Arriola & Alejandro (Octotropideae, Rubiaceae) is herein described and illustrated as a new species from Marinduque, Luzon, Philippines. The uniflorous inflorescences and infundibuliform calyx tube of V. marinduquensis resemble those of V. acutifolia and V. uniflora; however, the features of bracts, calyces and corolla in the new species differ from those in the two afore-mentioned species. Villaria marinduquensis is distinguished from all of its congeners by having a tubular corolla tube. An identification key to the Villaria species is provided.

Ardisia bullata G.H. Huang & G. Hao (Primulaceae), a new species endemic to the island of Hainan (southern China), is described and illustrated. It is affiliated to subgenus Bladhia, with A. ramondiiformis, A. silvestris var. silvestris, and especially A. silvestris var. appressa as close allies, but can be distinguished by the character combination of sessile and bullate leaves with an appressed-hirsute abaxial surface, ovate or broadly ovate sepals, and axillary racemose-paniculate inflorescences.

Rungia khoii D.V. Hai, Y.F. Deng & Joongku Lee, a new species from Vietnam, is described and illustrated. It is morphologically similar to R. daklakensis and R. clauda, but differs in the shape of its leaves, stem, bracts, corolla and fruits, as well as by the different stamens and anther thecae.

In recent treatments of Fissidens subgenus Fissidens, the species delimitation of F. bryoides, the type species of the subgenus, has been rather variable. In Finland, F. bryoides has either been split into F. bryoides, F. gymnandrus and F. viridulus, or treated as a single species, F. bryoides s. lato, including two or more intraspecific taxa. The herbarium material of Finnish F. bryoides, F. gymnandrus and F. viridulus was studied to clarify the distribution and ecological requirements of the three taxa and to find out which morphological and ecological characters are best for their delimitation. The phylogeny lends support to recognizing F. bryoides s. lato including F. gymnandrus and F. viridulus as F. bryoides var. gymnandrus and F. bryoides var. viridulus. The phylogeny reconstruction based on 18 morphological characters that are commonly used to distinguish the taxa could not resolve F. bryoides, F. gymnandrus and F. viridulus as monophyletic species. However, F. bryoides s. lato including all herbarium material of the three species was resolved as a monophyletic group morphologically distinct from the closely related F. pusillus. The synapomorphic characters that distinguish F. bryoides s. lato are the percurrent costa, limbidia that reach the leaf acumen, the acuminate leaf acumen, and a preference for substrates other than rock. We found differences in habitat requirements between the varieties, while sexual systems sometimes vary even within a single specimen. Fissidens bryoides var. bryoides and F. bryoides var. gymnandrus appear to have wider distribution in Finland than expected. Unlike F. bryoides var. viridulus the number of localities of F. bryoides var. bryoides and F. bryoides var. gymnandrus is low. Information on their conservation status is also provided.

Prunus nutantiflora D.G. Zhang & Z.H. Xiang sp. nova (Rosaceae) from Hunan Province, China, is described, illustrated and compared with morphologically similar species. Prunus nutantiflora resembles especially P. xueluoensis in having three axillary winter buds and an ellipsoid drupe, but differs from it by having a densely pilose style base and a campanulate hypanthium (ca. 4 × 2.5 mm).

Historical (mainly 1930s) and contemporary records of 482 vascular plant species or genera of non-littoral areas of 464 islands in the archipelago of SW Finland are compared, to visualise changes in distribution patterns, and to identify environmental variables that affect the distribution of the species. The environmental variables were measured in a GIS. Logistic regression analysis was used to find variables that affect the probability of species occurrences. Results, with distribution maps, are presented for each species. The families Apocynaceae, Gentianaceae, Menyanthaceae, Oleaceae, Adoxaceae, Caprifoliaceae, Convolvulaceae, Boraginaceae, Lamiaceae, Plantaginaceae, Solanaceae, Scrophulariaceae, Campanulaceae and Asteraceae are presented in this fifth part of the series. A synthesis of the study will be presented in the last part of this article series.

Astragalus nuoergongensis L.Q. Zhao & Xu Ri (Fabaceae), a new species from Inner Mongolia and Ningxia, China, is described and illustrated. It is morphologically quite similar especially to A. scabrisetus, but its calyx is densely covered with appressed bifurcate hairs, its calyx teeth are 1/2–3/4 the length of the calyx tube, and its legumes are covered with appressed bifurcate hairs and have a beak of 2.5–4 mm long. The species is assigned to Astragalus subgenus Cercidothrix sect. Trachycercis due to its short-branched subsurface caudex, bifurcate hairs and uninflated calyx after anthesis.