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The Gullele Botanic Garden (GBG), on the slope of the Entoto hills, adjoins the north-western limit of the city of Addis Ababa, the capital of Ethiopia. The forested area of GBG is home to a mixture of semi-natural forest and Eucalyptus plantations with Eucalyptus having been removed in the recent past. The floristic composition, species diversity and vegetative structure of the woody plant species in the forested area are here presented from 81 plots (20 × 20 m). A total of 104 woody plant species (90% native, the rest planted or naturalised) of 83 genera and 47 families are recorded; a species richness higher than what researchers have found in nearby natural forests, though the definitions of woody species have varied between studies. The number of individuals of the dominant species, Juniperus procera, decreases with increasing DBH and height class, which indicates a healthy regeneration inside the GBG; the appearance of seedlings and young plants of Juniperus after the removal of Eucalyptus is comparable to the regeneration of Juniperus forests described from East Africa after forest fires or clear-felling. Clustering analyses on the floristic data result in four partly overlapping clusters, but the distribution of the plots on clusters changes notably if data on Eucalyptus is in- or excluded. Many woody species in nearby natural or semi-natural forests, where Juniperus procera is dominant, occur also in GBG but plant communities defined for those forests are not identified in the plot data from GBG. The findings in this paper can serve as a baseline dataset to follow the regeneration of the conservation area towards natural forest, useful for future anagement and sustainable utilization of Ethiopian forest species at local and national levels.

Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distribution ranges. Temperature is one of the most important drivers of plant phenology together with day length. The adaptation of their phenology may be important for the success of invasive plant species. The present study aims at understanding how the performance and the phenology of the invasive legume Lupinus polyphyllus vary with latitude. We sampled data across a >2000 km latitudinal gradient from Central to Northern Europe. We quantified variation in phenology of flowering and fruiting of L. polyphyllus using >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 sites. The day of the year at which different phenological phases were reached, increased 1.3–1.8 days per degree latitude, whereas the growing degree days (gdd) required for these phenological phases decreased 5–16 gdd per degree latitude. However, this difference disappeared, when the day length of each day included in the calculation of gdd was considered. The day of the year of the earliest and the latest climatic zone to reach any of the three studied phenological phases differed by 23–30 days and temperature requirements to reach these stages differed between 62 and 236 gdd. Probably, the invasion of this species will further increase in the northern part of Europe over the next decades due to climate warming. For invasive species control, our results suggest that in countries with a large latitudinal extent, the mowing date should shift by ca. one week per 500 km at sites with similar elevations.

The western woodlands of Ethiopia have been less studied than the highlands, with a first description published in 1940. Based on fieldwork and herbarium studies we intend to increase the knowledge of these woodlands. Some authors describe them as one continuous zone from south to north, spanning ca. 10° latitude and dominated by species of Combretum and Terminalia but sometimes with various names applied to the vegetation at its limits. The Atlas of the Potential Vegetation of Ethiopia (2010) followed the continuous model. In the Sudan and South Sudan, the same vegetation is described as distinct types defined on soil and rainfall. Reviewing species composition, environment, research-history and human influence, we present our own observations of the woody species and map their distribution in Ethiopia, review their ecological adaptations and model the total distribution in Africa of twelve characteristic species. We use our data for clustering and principal component analyses to study continuity and discontinuity of the vegetation and the drivers of variation. The appearance of the western woodlands is variable, and cluster analyses indicate that a high number of small and narrowly defined units might be identified. A significant number of trees are widespread from north to south, but some are restricted to the north, a few to the centre and south, and many just enter the woodlands with a main distribution elsewhere. At a high level, our analysis defines two or three weakly defined clusters, (1) the northern woodlands to just south of the Abay River and continuing far south as a brim along the western escarpment of Ethiopia, (2) woodlands south of the Abay at altitudes above cluster no. (1), and (3) dry woodlands of the upper Tacazze and Abay Rivers. Many environmental factors explain small but important parts of the variation. The clusters relate to variables such as latitude, altitude, climate and soil types, while slope, fire frequency and other parameters are

Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distribution ranges. Among the environmental factors, phenology is mostly driven by temperature and day length. Rapid adaptation of their phenology may also be important for the success of invasive plant species. Our main aim was to understand how the performance, timing, and temperature dependence of the phenology of the invasive legume Lupinus polyphyllus varies with latitude. L. polyphyllus is one of the most frequent invasive species in Europe, and the gained information may help to make management more effective by adjustments to latitude and phenology. Methods: We quantified variation in phenology across a >2000 km latitudinal gradient from Central to Northern Europe. We sampled data of flowering and fruiting of L. polyphyllus using >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 locations. We calculated the accumulated growing degree days for each observation date at each site from the temperature data of the meteorological stations, which are listed in the metadata of the dataset., License:This work is licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication license.

Pichi Sermolli’s work with his more than 2750 collections of plants from nearly 150 localities on the Lake Tana expedition in Ethiopia in 1937 was interrupted by World War II, but completed in 1947 at the Royal Botanic Gardens, Kew, and the British Museum (Natural History), UK. It resulted in preliminary accounts of the vegetation published 1938-40 and a taxonomically arranged account in 1951, all in Italian. Pichi Sermolli’s observations are difficult to locate due to the imperfect maps of the time, but in this book the authors have reconstructed the sequence of the collections, georeferenced the localities, and updated the identifications of the species. By reconstructing Pichi Sermolli’s observations, it is possible to draw conclusions about the vegetation and compare with a recent model of the vegetation of Ethiopia. According to this, the vegetation of the Lake Tana Basin was a complex mosaic of woodland, scrub, forest, farmland and lake shore vegetation now difficult to interpret in detail. Pichi Sermolli’s study of the vegetation in the Semien Mountains demonstrated for the first time the zonation of Ericaceous woodland and Afroalpine vegetation, within which he distinguished Carex monostachya bogs, Afroalpine grasslands with Lobelia rhynchopetalum, and stony and rocky Afroalpine vegetation. This book interprets Pichi Sermolli’s observations in English and compares them with modern knowledge of the region, partly obtained by the present authors’ own field work. It demonstrates how Pichi Sermolli’s studies form a valuable contribution to the understanding of the Ethiopian flora and vegetation.

Understanding biodiversity of plants depends on detailed knowledge of foristics and environmental parameters. According to the Flora of Ethiopia and Eritrea (FEE; 1989–2009), the latest academic fora of these two topographically complex countries, the number of taxa (including non-indigenous ones) is 6027 of which 647 are endemic. Since 2009, 56 indigenous taxa have been described from the FEE area. Based on FEE data and later information, the number of indigenous species is here counted at 5219. In the RAINBIO database Sosef et al. (BMC Biol 15:1–23, 2017) counted the number of indigenous species in Ethiopia at 4481 (Eritrea not counted). Studies of local diversity and endemism produce diferent results with varying methods and sources: FEE data show highest diversity in the southern part of Ethiopia near the borders with Kenya, while RAINBIO data show highest diversity in the south-west and around the town of Harar. Wang et al. (J Syst Evol 58(1):33–42, 2020) found the highest ‘weighted endemism’ in the central Ethiopian mountains, while our FEE data indicates highest single-region endemism near the borders with Kenya and Somalia; Hawthorne and Marshall (Gard Bull Singap 71(Suppl. 2):315–333, 2019), weighting species according to rarity, found the highest ‘bioquality score’ in the same areas as our highest single-region endemism. Studies of altitudinal diversity show a ‘mid-elevation diversity bulge’ at 1400–2100 m a.s.l. More data are needed before we understand the complex diversity of the two countries, including altitudinal diversity. We review needs for additional data gathering and modelling that may help answering outstanding questions.

On two independent field trips in 2015 and 2018, the authors collected a tall shrublike succulent species of Euphorbia (Euphorbiaceae) in Combretum-Terminalia woodland of the Omo Valley in south-western Ethiopia. These collections represent the easternmost records of E. venefica Trémaux ex Kotschy and are the first records from inside the borders of Ethiopia. Euphorbia venefica belongs to a group of large succulent species with single spines borne on a spine-shield and arranged on the cylindrical stem in a spiral. The species in this group are reviewed here, based on material in herbaria and the literature. The East African E. venefica and the West African E. unispina share potential distribution, have overlapping variation in stem- and leaf-morphology and cannot be separated by the characters mentioned in the literature. We consider these two taxa to be one species, to be called E. venefica and distributed from Burkina Faso to Ethiopia. E. poissonii presents characters that may justify it being a separate species restricted to Africa west of Cameroon. Euphorbia darbandensis N.E. Br. and E. sapinii De Wild. are too poorly known and could not be placed. Conservation assessments suggest that neither E. venefica, nor E. poissonii are threatened.

Anacampseros specksii Dreher (Anacampserotaceae, in Flora of Ethiopia and Eritrea in Portulacaceae), was described in 2016 from plants grown from seeds collected from Bale, SE Ethiopia. The species was not included in the paper on the Gerire Hills published by the present authors in Webbia in 2018. A. specksii is here considered to be another narrow endemic species in the Gerire Hills, belonging to the group of species that grows on the edges of Monte Ellot and Bur Caddas on sandstone rocks eroding into loose gravel. Anacampseros vespertina, the only other species of Anacampseros in NE tropical Africa, grows on limestone gravel in Somalia near the Indian Ocean, whilst the south tropical African species, A. rhodesica, grows on granite rocks in Zimbabwe, Botswana, Mozambique and South Africa. The conservation assessment in 2016 for A. specksii was Data Deficient (DD) because only one population had been observed and the number of individuals is not known; this assessment is here discussed and maintained.

The vegetation of the plateaux of the Gerire Hills, of unique geology, represents an outlier of the Transitional semi-evergreen bushland of the eastern escarpment of the Ethiopian highlands, about 160 km from continuously distributed vegetation of this type. In the lowland surrounding the hills is deciduous Acacia-Commiphora bushland, typical of the Somalia-Masai region. Unpublished data from a 1937 Italian expedition documents past existence of Juniperus procera on the plateaux. Three new narrowly endemic species are described here from recently collected material: Croton elkerensis Friis & M.G. Gilbert (Euphorbiaceae), Gnidia elkerensis Friis & Sebsebe (Thymelaeaceae), and Plectranthus spananthus A.J. Paton, Friis & Sebsebe (Lamiaceae). Three previously described species from the hills, Blepharispermum obovatum Chiov. (Asteraceae), Aloe elkerriana Dioli & T.A.McCoy (Aloaceae) and Euphorbia bertemariae Bisseret & Dioli (Euphorbiaceae), are narrow endemics. The species most similar to the bushland endemics occur in a range of vegetation types and phytochoria in East Africa south of Ethiopia or more widespread in Africa. The species most similar to the succulent endemics occur elsewhere in semi-evergreen bushland on limestone at the mountain range in northern Somalia. The Gerire Hills endemics are considered Vulnerable (VU) or Least Concern (LC) given the differing threats to their respective habitats.

Crotalaria trifoliolata Baker f. (Leguminosae: Papilionoidaeae) was, for 120 years, only known from an incomplete holotype from an uncertain Ethiopian locality. In 2013 it was rediscovered in the Bale Zone, eastern Ethiopia. Surveys in 2014 and 2015 suggest that the species is restricted to limestone habitats in the Kubayo National Forest, where it forms almost monospecific stands of up to one thousand individuals in glades and at forest margins. Predictive distribution models suggest uncertain suitability of the present habitats under future climatic conditions. Based on this and other potential threats, the species is evaluated as Endangered (EN). Crotalaria trifoliolata is a bigger shrub than previously thought (up to c. 2 m high, with stems up to c. 3 cm in diam.). Molecular studies confirm that C. trifoliolata is related to the widespread C. saltiana, as predicted from morphological observations. A later name, C. malacothcha Harms, is placed in synonymy of C. trifoliolata. Information from local informants suggests that Walenso, the name of the type locality for both C. trifoliolata and C. malacotricha, is a collective name for mountains within the Kubayo Forest.

Forfatterne gennemførte i 2013 en måneds feltarbejde i området omkring Ginir, Sheik Hussein, Imi og Dolo Mena in den østlige Oromia og tilgrænsende dele af Somalia Regional States. Ib Friis havde for 30 år siden i forbindelse med det etiopiske floraprojekt forsøgt at arrangere en felttur til området omkring Ginir, men forsøget blev standset af sikkerhedsgrunde, og siden var situationen stadig så ustabil, at feltarbejde ikke var muligt. Artiklen beskriver en række vigtige iagttagelser fra rejsen i 2013.

The incompletely known Crotalaria trifoliolata Baker f. (Leguminosae subfam. Papilionoideae) has been rediscovered in the field. For 120 years, it has been known only from a fragmentary holotype with uncertain collecting locality. The habit and height of the plant, the pods and the seeds are here described for the first time. The new information confirms that C. trifoliolata belongs to sect. Hedriocarpae Wight & Arn. subsect. Hedriocarpae. Within that subsection it is similar to a small number of other species of Crotalaria from the Somalia-Masai floristic region (C. leucoclada Baker, C. rhynchocarpa Polhill, C. saltiana Andrews, C. thomasii Harms) in having the inside of the pod densely packed with long, white hairs. C. trifoliolata was observed at the edge of and in glades inside dry Juniperus-Olea forest, in which the canopy is dominated by J. procera Endl. and the undergrowth by Barbeya oleoides Schweinf. and other species characteristic of dry Afromontane forest and bushland. The species is found only in a limited area near the eastern Ethiopian escarpment at Sheik Hussein. It is documented with images and maps, its potential distribution is modelled and a conservation assessment is provided, suggesting that C. trifoliolata is Endangered (E).

Subsequent to the treatment of the Aloaceae, with 38 species of Aloe, in the Flora of Ethiopia (Sebsebe Demissew & Gilbert 1997), four more species, Aloe bertemariae Sebsebe & Dioli (2000), A. friisii Sebsebe & M. G. Gilbert (2000), A. clarkei L. E. Newton (2002) and A. elkerriana Dioli & T. A. McCoy (2007) have been described from that country. Here four additional new species are described: Aloe benishangulana Sebsebe & Tesfaye from near Assosa, Benishangul-Gumuz in Welega floristic region; A. ghibensis Sebsebe & Friis from the Ghibe Gorge, Kefa floristic region; A. weloensis Sebsebe from near Dessie in Welo floristic region and A. welmelensis Sebsebe & Nordal along the Welmel River in Bale floristic region. The phytogeographical positions of the new species are assessed by comparison with the previously known species. Complications with the deposition of type material of A. clarkei and A. elkerriana is used to raise various issues regarding the ethics of describing new taxa from foreign countries.