Simone Orsenigo

Hieracium is a megadiverse genus within the family Asteraceae (tribe Cichorieae), and its evolutionary history has been challenging to tackle due to processes such as hybridization, polyploidizatio...

Aim: The European alpine life zone is a recognized biodiversity hotspot, currently impacted by warming temperatures. Here, we investigated temporal plant diversity changes and thermophilization processes on multiple summits' flora. Location: Italy: six mountain regions across the Alps and the Apennines. Methods: We evaluated two decades (2001–2024) of plant species presence and abundance across 23 summits, covering an elevation gradient from the treeline ecotone to the nival belt, monitored through permanent sampling areas. We investigated temporal trends of species gain and disappearance, species richness, alpha and beta diversity indices, species‐specific abundance changes, and the thermic indicator of plant assemblages. Results: Three summits in the Central and Northern Apennines experienced net species loss, involving endemic taxa, although species richness significantly increased in all other summits. At summit level, 7% of species significantly declined in abundance (’losers’), and with the same rate across the upper alpine and subnival belts (7%). About 5% of the species significantly increased (’winners’), and colonization rates were highest in the uppermost vegetation belts. The thermic indicator significantly increased in all mountain regions but the Central Apennines, with increasingly higher rates from the lowermost to uppermost vegetation belts, and accelerated during 2015–2024 in the Texel Group. Main Conclusions: We provide evidence of recent increasing thermophilization trends across the Alps and the Northern Apennines. The local plant species loss, including endemic taxa, and the widespread trend of loser species (not yet disappeared) may signal future local extinctions across both the Alps and Apennines also at the high‐elevated belts. The colonization rate observed in the uppermost vegetation belts further suggests a shift towards warmer thermic conditions at high elevations.

Recent changes in alpine vegetation are often attributed to climate warming, particularly community composition shifts towards more warmth-associated species, or thermophilization. Here we assess the link between thermophilization and warming across 53 European mountain summits. We combine long-term macroclimatic and microclimatic temperature time series with vegetation surveys in 724 permanent plots, monitored over 21 years, to evaluate a possible thermophilization signal and relate it to rates of change in 10 temperature metrics. We find evidence of both thermophilization of alpine plant communities and an increase in temperatures. However, although these two trends are related when averaged across mountain regions, their relationship is weak at the individual plot scale, especially when considering microclimatic temperature metrics. Instead, substrate conditions and particularly the availability of thermophilic colonizers in the surrounding vegetation have a major influence on plot-level thermophilization rates. We conclude that the response of plant communities to climate change strongly depends on the abiotic and biotic context, and intensified monitoring efforts are needed to reduce the resulting uncertainties.

In this contribution, the conservation status assessment of five vascular plants according to IUCN categories and criteria are presented. It includes the assessment of Iris kuschakewiczii B.Fedtsch., Lepidium olgae (R.M.Vinogr.) Al-Shehbaz & Mummenhoff, Parrya saxifraga Botsch. & Vved., Phleum sardoum (Hack.) Hack. and Tanacetum ulutavicum Tzvelev at global level.

Afzelia corallina A.Bianchi, S.Orsenigo & Baldesi (Fabaceae: Detarioideae) is described from the coral rag forests of the Tondooni Peninsula in the Ngezi–Vumawimbi Forest Reserve on Pemba Island, Zanzibar, Tanzania. Morphologically distinct from all known members of the genus, this large, emergent tree shows the closest affinities to Afzelia quanzensis but differs in several vegetative and floral characters, including its falcate leaflets, highly branched terminal inflorescences, petal colour, the colour of stamens, and the number of extra staminodes. The species is currently known only from a restricted coastal limestone habitat, indicating a micro-endemic distribution. An updated diagnostic key to East African Afzelia species is provided. This discovery highlights the botanical uniqueness and conservation importance of Pemba’s remaining forest ecosystems.

Climate warming is shifting biological communities, with warmth-demanding species being favoured at the expense of cold-adapted species in a process referred to as thermophilization^1-4. Because biodiversity responses often lag behind climate warming, climatic debts are accumulating in many ecosystems across the world^5-7. Although we might expect that thermophilization and climatic debts will vary among habitats, standardized quantification across ecosystems is lacking. Here we analysed multidecadal data from 6,067 resurveyed vegetation plots over 12-78 years in forests, grasslands and on alpine summits across Europe. We demonstrate that forest understory and grassland plant communities experienced positive thermophilization, although not significantly different from zero. By contrast, alpine summit vegetation showed much stronger (up to five times) and significant thermophilization. Thermophilization was driven largely by increases in warmth-demanding species in grasslands, by declines in cold-adapted species on alpine summits and by both processes in forests. Significant climatic debts have accumulated in forests and alpine summits, but less so in grasslands, with debts positively correlated with macroclimate temperature changes. Our findings uncover divergent thermophilization trajectories and increasing climatic debts across ecosystems. Moreover, we highlight the mechanisms that enable some communities to track climate change more closely than others and provide a basis for projecting future shifts in plant communities under accelerating climate warming.

The Ngezi–Vumawimbi Forest Reserve is the largest remaining patch of natural vegetation on Pemba Island, Zanzibar, Tanzania. In 2024, in collaboration with the Department of Forestry, Ministry of Agriculture, Zanzibar, we conducted a baseline biodiversity survey of animal and plant communities. Preliminary results reveal previously unrecognized plant diversity, including species likely new to science that are currently under study. We confirmed the presence of endemic and threatened plant species, and recorded populations of species not previously reported on Pemba Island. We also confirmed the presence of a small population of blue duiker Philantomba monticola , currently under threat from poaching. One of the areas richest in plant diversity is designated for development of a new tourist resort. This would replace most of the Vumawimbi evergreen coastal forest, home to a unique forest type in continental Africa dominated by Intsia bijuga .