Common milkweed (Asclepias syriaca L.) is widely planted as part of monarch butterfly (Danaus plexippus) conservation efforts. Vegetative propagation is an alternative to planting A. syriaca from seed and offers advantages such as high emergence rates. The aim of this study was to determine the ideal planting depth and initial root segment length to vegetatively propagate A. syriaca. In a greenhouse trial with two runs, A. syriaca was grown from seed, and then 3-, 8-, and 15-cm segments were harvested. These segments were then planted at depths of 3, 8, or 15 cm. Planting depth did not impact A. syriaca growth, but an initial root segment length of 15 cm was associated with greater above- and belowground biomass and height in both runs of the experiment. Emergence rates were not impacted by either factor. Overall, A. syriaca was likely to establish regardless of the initial root segment length or planting depth, but plants grown from root segments of 15 cm were more vigorous than plants grown from shorter segments.

Hancornia speciosa Gomes is popularly known as mangabeira and occurs throughout Brazil. It belongs to the Apocynaceae family and is very important for its food and medicinal uses. The objective of this study was to perform the anatomical and histochemical characterization of the leaves of H. speciosa. Microscope slides were made containing cross sections of petiole and leaf blade, as well as paradermic sections of the leaf blade. The analyses were performed under light and polarized microscopy. For the histochemical analysis, different reagents were used, according to the targeted metabolite. Through microscopic analysis, it was possible to identify the anatomical structures that provide the detailed diagnosis of the studied species. Through histochemistry, the presence of phenolic compounds, tannins, alkaloids, triterpenes and steroids, lipophilic compounds, lignin, starch, and calcium oxalate crystals was evidenced in the leaf blade. Thus, the results presented contribute to the quality control of H. speciosa, as well as to bring unpublished data about the species and to increase knowledge about the Apocynaceae family.

Pale swallowwort and black swallowwort are European viny milkweeds that have become invasive in many habitats in the northeastern United States and southeastern Canada. A multiyear seedbank study was initiated in fall 2011 to assess annual emergence of seedlings and longevity of seeds of pale swallowwort and black swallowwort at four different burial depths (0, 1, 5, and 10 cm) over 4 yr. One hundred swallowwort seeds were sown in seed pans buried in individual pots, and emerged seedlings were counted and removed from May through September each year. A subset of seed pans was retrieved annually in October, and recovered seeds were counted and tested for viability. The majority of seedling emergence occurred during the first year (92% in 2012), and no new seedlings emerged in the third (2014) or fourth (2015) years. Pale swallowwort had relatively poor emergence at sowing depths of 0 cm (11%), 5 cm (6%), and 10 cm (0.05%—only one seedling), while 37% of pale swallowwort seeds emerged at 1 cm. The larger-seeded black swallowwort was more successful, with two-thirds of all sown seeds emerging at depths of 1 cm (71%) and 5 cm (66%), and 26% emerging at 10 cm. Only 16% of the surface-sown black swallowwort emerged. A large portion of the seeds that germinated at 10 cm, as well as at 5 cm for pale swallowwort, died before reaching the soil surface. Of filled seeds that were recovered in 2012 (black swallowwort at the 0-cm depth), 66% were viable. No viable seeds were recovered after the second growing season. Seeds recovered following the third year had become too deteriorated to accurately assess. Swallowwort seeds do not appear to survive more than 2 yr in the soil, at least in our experiment, suggesting that the elimination of seed production over 3 yr will exhaust the local seedbank. Seeds would need to be buried at least 10 cm for pale swallowwort but more than 10 cm for black swallowwort to prevent seedling emergence. Burial of swallowwort seeds as a management strategy may, however, only be practical in natural areas where high swallowwort densities occur.

Knowledge of photosynthetic capacity is crucial for fully understanding a species’ invasive potential and for the development of appropriate control strategies. Although growth and reproductive data are available for the invasive swallowwort vines Vincetoxicum nigrum and V. rossicum, photosynthetic data are wanting. These herbaceous, perennial congeners were introduced from separate European ranges during the late 19th century and became invasive during the following century in the northeastern United States and southeastern Canada. Vincetoxicum nigrum has been observed growing mainly in high light environments, whereas V. rossicum occurs across a wide range of light environments, suggesting niche divergence and that different management strategies might be needed for the two species. In this work, we investigated whether the differing habitat associations of these species is reflected in their photosynthetic capacities and leaf morphology. Photosynthetic parameters and specific leaf mass were determined across a range of light environments represented by four field habitats (common garden, forest edge, old field, and forest understory) and two greenhouse environments (high and low light). In the high-light common garden habitat, V. nigrum achieved 37% higher maximum photosynthetic rates than V. rossicum, but photosynthetic performance of the two species was the same in the forest edge habitat. Additionally, species’ performance was virtually identical in high light, low light, and transitions between high and low light regimes in the greenhouse. Specific leaf mass of V. nigrum was 17% higher in the common garden and 19% higher in the greenhouse compared with V. rossicum. Both invasive Vincetoxicum spp. appear capable of growing within a broad range of light environments and their management should be similar regardless of light environment. Other explanations are required to explain the scarcity of V. nigrum in low light natural areas.

Rhazya stricta is an endangered medicinal plant that is under severe human pressure as a result of commercial harvesting. As a model of habitat fragmentation, we selected the Kohat Plateau in the Pakistani Himalaya, where populations are fragmented, with less than 100 individuals per population. We hypothesized that the populations may be threatened by rapid habitat fragmentation and by unsustainable utilization of the plant. We analysed P450-based analogue functional genomic markers and amplified fragment length polymorphism markers from six populations of R. stricta on the Kohat Plateau, and examined their variations both within and among the populations. Both the marker groups revealed lower genetic differentiation among the populations and higher genetic differentiation within the populations as a result of high gene flow. The results confirmed that habitat fragmentation is being caused by severe human pressure, and although signs of genetic erosion are not yet visible, they seem likely to become visible in the future. Therefore, the conservation of R. stricta populations is necessary.

Lectotypes are selected for the following names in the Apocynaceae from the Arabian Peninsula: Adenium arabicum Balf.f., Adenium obesum (Forssk.) Roem. & Schultes, Caralluma adenensis (Deflers) A.Berger, Cryptolepis intricata (Balf.f.) Venter, Cryptolepis volubilis (Balf.f.) O.Schwartz, Kanahia laniflora (Forssk.) R.Br., Leptadenia arborea (Forssk.) Schweinf., Marsdenia robusta Balf.f., Rhazya stricta Decne. and Tylophora yemensis Deflers. For Secamone socotrana Balf.f., it is noted that a previous citation of a holotype is rather an effective designation of a lectotype. Neotypes are selected for Caralluma hexagona var. septentrionalis Lavranos & L.E.Newton, Glossonema boveanum (Decne.) Decne., Leptadenia pyrotechnica (Forssk.) Decne. and Orbea chrysostephana (Deflers) Bruyns.

Dischidia micholitzii N.E.Br. (Apocynaceae, Asclepiadoideae), described from a cultivated plant and erroneously assumed to be from Burma, is native to the Tenimbar and Babar island groups of Maluku, Indonesia. It is closely related to Dischidia ovata Benth. from New Guinea and Australia.

Pinochia, a new neotropical genus of Apocynaceae, subfamily Apocynoideae, is segregated from Forsteronia, described and illustrated. Four new combinations and a key to the species are provided.

Three new species of Chilocarpus (Apocynaceae – Rauvolfioideae) from Malesia are described: Chilocarpus hirtus D.J.Middleton, Chilocarpus pubescens D.J.Middleton and Chilocarpus sarawakensis D.J.Middleton. Preliminary conservation assessments are proposed.

Pollination in the genus Ceropegia L. (Apocynaceae: Asclepiadoideae–Ceropegieae) in East Africa is discussed based on field observations and herbarium studies. All inferred or confirmed pollinators are small, mostly female dipteran flies, c. 2.5mm long, which carry pollinaria on their proboscis. Identified putative pollinator flies belong to families Milichiidae, Chloropidae and Ceratopogonidae. The most important factors for an insect to effect pollination appear to be the appropriate overall size, i.e. small size of c. 3×;3mm at most, and appropriate mouth parts, i.e. extendible probosces with suitable surfaces and adjacent pads on which a pollinarium can attach. The complex and diverse floral morphology of the tubular flowers and their disposition as well as other commonly occurring features namely, diverse interior and exterior coloration, diverse scents, secretions such as nectar and water droplets, vibratile corolla lobes and hairs, specialized hairs, interior sculpturing, sliding zones and differential lighting within the flower are important mechanisms for attracting and detaining insect pollinators.

The new species Echidnopsis inconspicua (Apocynaceae–Asclepiadoideae) and Secamone cuneifolia (Apocynaceae–Secamonoideae) are described from Socotra. An account of Echidnopsis is provided for the island, where five species are now known to occur. The first species of Ceropegia is recorded for Socotra.

More than 30 collections of Tylophora from all over its geographic range were analysed together with representatives of all other genera in subtribe Tylophorinae except Rhyncharrhena. Regions of the chloroplast genome (trnT-L spacer, trnL intron and trnL-F spacer) as well as the nuclear genome (internal transcribed spacer including 5.8S of nuclear ribosomal DNA) were sequenced. Both the cpDNA dataset and the rDNA dataset yield a number of stable clades, but a completely resolved and stable phylogeny is not obtained from either alone or by combining them. The small East African and Arabian genera Blyttia, Diplostigma, Goydera and Pleurostelma form a well-supported clade in both datasets. Pentatropis is always recognized as monophyletic. Vincetoxicum is not clearly separable from Tylophora, and probably covers the temperate species, while Tylophora covers those in the tropics and subtropics.