Tiina Särkinen

Societal Impact Statement: The IUCN Red List is the main global authority for determining species extinction risk. For vascular plants, fewer than 22% of all species have been globally assessed. Here, we evaluate whether those species assessed are representative of all known vascular plant species. There are significant biases in the IUCN Red List in terms of the distribution of species assessed, with herbaceous species and geographical regions such as temperate Asia under‐represented. The Sampled Red List Index for plants provides less biased extinction risk estimates, although biases remain. We hope that our findings facilitate effective prioritisation for future Red Listing projects.

Questions: Seasonally dry tropical forests are widespread globally and can store large quantities of carbon, yet they remain underrepresented in spatial assessments compared with humid tropical forests. The Caatinga biome in northeastern Brazil has experienced centuries of wood extraction and land‐use expansion, reducing its current biomass below ecological potential. We asked: (i) how do climatic, atmospheric, and topographic gradients regulate the spatial distribution of aboveground biomass? and (ii) where does the biome maintain a high potential for carbon storage under current environmental conditions? Location: Caatinga biome, northeastern Brazil. Methods: We compiled data from 301 georeferenced forest inventory plots and integrated them with high‐resolution climatic, atmospheric, and topographic predictors. We used principal component analysis to identify major environmental gradients and fitted a spatially validated random forest model to estimate the potential aboveground biomass across the biome. Model performance was evaluated using both random and spatial cross‐validation. Results: Two nearly orthogonal environmental gradients emerged: a hydrothermal gradient associated with precipitation, temperature, and drought severity, and a topographic gradient associated with slope, terrain ruggedness, and landform position. The spatial model explained substantial variation in biomass potential ( R ² = 0.81; RMSE = 21 Mg ha ⁻¹ ). Biomass potential increased markedly when drought severity was lower (maximum cumulative water deficit less negative than −500 mm) and annual precipitation exceeded approximately 1100 mm, while higher vapor pressure deficit and potential evapotranspiration were associated with reduced biomass potential. Rugged and concave terrain supported more than twice the aboveground biomass found in flat or convex sites. Conclusions: The Caatinga is not a uniformly low‐biomass system but a heterogeneous landscape containing localized high‐biomass refugia shaped by the interaction of water availability, atmospheric demand, and terrain complexity. By estimating potential biomass, this work provides a baseline to guide ecological restoration, conservation planning, and climate mitigation strategies in tropical drylands.

Aim: We investigate the distribution of dispersal modes — endozoochory (via animal ingestion), synzoochory (via animal seed accumulation) and anemochory (via wind)—and seed mass of woody plants across Brazilian ecosystems, testing whether their relative abundance in local plant communities could be predicted by climate, edaphic factors and dispersal agents (e.g., the main vectors moving seeds). We expected climate to be the main predictor of dispersal strategy abundance. Location: Brazilian ecosystems (Amazon, Atlantic Forest, Cerrado and Caatinga). Time Period: 2004–2020. Major Taxa Studied: Woody angiosperms, trees and shrubs. Methods: We assigned seed mass to 1984 species and dispersal mode to 2203 species within 300 old‐growth and non‐flooded plots. We employed Random Forest regressions to assess the influence of water availability, temperature seasonality, soil fertility, wind and frugivorous primates on the community‐weighted means of seed mass and dispersal modes. We mapped predictions and estimated the area of applicability to identify regions where predictions were reliable. Results: Climate was the main factor predicting tree dispersal strategies, followed by dispersal agents or soil properties. Endozoochory was prevalent in wetter regions with high water availability and greater diurnal temperature range. Anemochory was more common in drier regions with low water availability, stronger winds and greater diurnal temperature range, whereas synzoochory was more abundant in areas with low temperature seasonality. Heavier seeds were more prevalent in regions with less seasonal temperatures, smaller diurnal temperature ranges and weaker winds. Main Conclusions: Climate is a key predictor of the distribution and prevalence of plants with contrasting dispersal modes and seed masses. We thus expect functional responses to environmental change associated with shifts in the relative abundance of dispersal strategies, with implications for ecosystem services. Our results also highlight the critical role of plot‐based datasets in improving our understanding of how environmental factors influence seed dispersal strategies across tropical ecosystems.

Incomplete information on distributions for a high proportion of the world’s plant species together with biases in global biodiversity data mean that current estimates of plant diversity patterns are skewed. A key issue is that current predictions rely on a subset of species that is not representative of all plant species. Here we tested the feasibility of a representative sampling approach for mapping global vascular plant diversity at the finest scale where comprehensive data is available. Using the World Checklist of Vascular Plants as a reference, we generate random samples of species with increasing sample sizes from the global species pool. We compare the diversity patterns retrieved from the samples against the patterns of the reference dataset using spatially weighted correlation coefficients and four different diversity metrics. We find that at the botanical country scale, representative global maps of species and phylogenetic diversity can be created with small numbers of species (∼1% [0.2% and 0.4%, respectively]) at the botanical country scale. For effective growth form and family diversity sample sizes encompassing ∼20% [19.2% and 19.5%, respectively] of all species are needed. Random samples require markedly fewer species to reach high correlations than when restricting the pool of species to single plant families or genera. We show that when representative samples are used robust inferences of plant diversity patterns can be made from only a small proportion of species.

Solanaceae are a globally distributed family of considerable economic importance. Recent phylogenetic work on various clades in the family has resulted in a plethora of names at various taxonomic levels. This results in a confusing set of names applied to clades at different ranks, and to the use of informal names that are often not accepted in online resources. To solve this problem, we present here a phylogenetic classification following the PhyloCode for the Solanaceae. Traditional taxon names previously recognized at the ranks of tribe, genus, and section were maintained when associated with clades. We base our clade definitions on a newly constructed phylogeny of the family using 10 plastid and nuclear markers with a broad sampling of 1474 species, roughly half of the diversity of the family. We complement this marker‐based analysis with a phylogenomic analysis of 110 taxa (including 97 of the 103 genera in the family and the outgroup Ipomoea purpurea ) using the Angiosperms353 probe set. This pair of analyses produced highly concordant phylogenies and provided strong support for the clades included in the classification. In total, we propose and define rank‐free names for 38 major clades, including 16 infrageneric taxa within the mega‐diverse Solanum . This rank‐free system intends to promote name stability as new data become available, avoiding name changes to well‐known groups.

The Morelloid clade (black nightshades) is one of the most strongly supported clades within the megadiverse Solanum genus. It comprises 76 globally distributed, non-spiny herbaceous and suffrutescent species. While often erroneously considered poisonous weeds, several species are economically important as orphan crops. The clade is closely related to tomato and potato but, due to a lack of focused breeding efforts, remains a reservoir of genetic diversity for crop improvement. Despite this potential, we lack fundamental knowledge on the evolution of the Morelloid clade. The group includes polyploid species with unknown parental origins—likely reflecting reticulate processes such as hybridization, introgression, and associated backcrossing events. Prior analyses have been unable to disentangle these processes, leaving the mechanisms underlying reticulate evolution in the Morelloid clade poorly understood. Here, we use genome skimming to produce a well-supported maximum likelihood plastid phylogeny from complete circularized plastomes and a coalescent-based species tree from combined Angiosperms353 and conserved ortholog set nuclear markers. Our dataset, composed of previously published data and deep genome skimming from herbarium samples, spans 26 Morelloid species. To investigate patterns of non-treelike evolution, we used a nuclear phylogenetic network, multispecies coalescent simulations, a fused rooted nuclear chloroplast tree, and quantification of nuclear gene tree concordance. We show that incongruence between nuclear and plastid trees is pervasive and cannot be explained by incomplete lineage sorting alone. Instead, our results demonstrate that events consistent with repeated chloroplast capture have shaped the reticulate evolutionary history of the clade, especially among African polyploid and Pan-American diploid lineages.

The fossil record for Solanaceae has a complex taxonomic history, with many species originally described in the family being subsequently shown to belong in other plant families. In this work, we present an in‐depth analysis of the nightshade seed fossil record, which corresponds to the largest amount of fossil material for the family. We re‐examined 110 fossil seeds previously assigned either to one of the six described taxa or unplaced within the family. All fossils were imaged and measured for 15 discrete and continuous characters, and a subset of 22 well‐preserved specimens was additionally subjected to micro‐CT scanning. In parallel, we scored the same set of characters for seeds from 354 extant taxa of Solanaceae. We carried out a multivariate analysis of the combined extinct and extant dataset to visualize the placement of fossil seeds within Solanaceae seed morphospace. This analysis revealed a wide spread of fossils across morphospace, including a variety of shapes, sizes and testal wall features. For one fossil‐taxon ( Hyoscyamosperma daturoides gen. & sp. nov . ), the micro‐CT images confirmed the presence of an elaiosome, otherwise only known in the family from the genus Datura . Based on these analyses, we recircumscribe two specie, describe six new species and six new genera, doubling the number of fossil seed species in the family. The broad geographic and stratigraphic distribution of these diverse taxa, from Eocene North America and Europe to Pleistocene Eurasia, support the notion that the Solanaceae is likely a family of a Late Cretaceous origin that attained nearly a cosmopolitan distribution by the Eocene.

Viola lilliputana Iltis & H.E. Ballard, considerada la violeta más pequeña del mundo, ha sido conocida durante más de cinco décadas únicamente de su localidad tipo en Ayacucho. En este estudio reportamos tres nuevas localidades en Áncash, Huancavelica y Junín, lo que amplía de manera significativa su rango geográfico y altitudinal conocido. Los ejemplares de Huancavelica y Junín concuerdan con la descripción original, mientras que los de Áncash presentan órganos vegetativos y reproductivos de mayor tamaño y ligeras diferencias cualitativas, interpretadas como variación intraespecífica dentro del rango morfológico de la especie. La especie habita microambientes de puna altoandina, asociados a suelos crioturbados y cojines de Pycnophyllum. El modelamiento de distribución potencial mediante MaxEnt evidenció alta capacidad predictiva (AUC = 0.97) y una idoneidad ambiental fragmentada, determinada por variables térmicas propias de ecosistemas de alta montaña. Con base en parámetros espaciales (extensión de ocurrencia, área de ocupación y número de localidades), se propone su categorización como En Peligro (EN). Se discute su elevada vulnerabilidad, asociada a una fuerte especialización microambiental y la baja detectabilidad en campo, lo que subraya la necesidad de muestreos dirigidos en ecosistemas altoandinos para una evaluación y conservación adecuadas.

Background and Aims: Although almost 40 % of the plant species in the world are likely to be rare, little is known about the determinants of range size, a major axis of rarity, particularly in the tropics. Narrow geographical ranges make species more susceptible to extinction, hence understanding factors that are correlated with small range sizes is key to prioritizing conservation efforts. The niche breadth–range size hypothesis predicts range-restricted species to have narrow environmental tolerances. Here, we tested the niche breadth–range size hypothesis in two big tropical plant genera, Solanum and Begonia. Methods: We used taxonomically verified occurrence data to quantify the range size of 1065 species native to Southern America, calculated their climatic niche breadth based on six bioclimatic variables and used spatial null models to determine whether the observed niche breadth–range size relationship differed significantly from spatial autocorrelation. Key Results: The correlation between climatic niche breadth and range size did not differ significantly from null expectations in either genus. Range-restricted species across both genera occur at higher elevations and have narrower elevational ranges than widespread species, however. More than two-thirds of the species had their minimum niche breadth in temperature seasonality, with strong increases between range-restricted and widespread species, suggesting that niche breadth in terms of temperature seasonality plays a key role in shaping species distributions. Conclusions: Our findings support the view that niche breadth–range size correlations can arise artificially, from spatial autocorrelation. Macroclimatic conditions capture only a part of the ecological niche, and additional niche properties, such as adaptations to soil, fire, and biotic interactions, are likely to influence species ranges, particularly in species-diverse tropical groups. Our findings emphasize that tropical mountains, such as the Andes and the Atlantic forests of Brazil, are globally important centres of range-restricted plant species.

Seasonally Tropical Dry Forests (STDFs) are widespread throughout the world and store significant amounts of carbon; however, they are often overlooked in spatial assessments compared to humid tropical forests. The Caatinga, which is the largest seasonally dry tropical forest in South America, covers approximately 862,000 km ^² in northeastern Brazil and supports millions of people. Unfortunately, its carbon dynamics has not been thoroughly quantified, especially after centuries of land-use transformation and wood extraction that have significantly diminished its biomass stocks. In this study, we model the potential aboveground biomass (AGB) that Caatinga could sustain under current climatic, atmospheric, and topographic conditions. We integrated data from 301 geo-referenced plots along with high-resolution environmental predictors. The principal Component Analysis revealed two main gradients: a hydro-thermal axis dominated by precipitation, temperature, and severity of drought, and a topographic axis reflecting slope, ruggedness, and terrain position. Random Forest models, validated through both random and spatial cross-validation, explained a significant amount of variation in AGB (R ^² = 0.81, RMSE = 21 Mg ha). Our findings indicated that AGB is highly sensitive to water availability. In particular, biomass increased sharply when the maximum cumulative water deficit (MCWD) was less than –500 mm and annual rainfall exceeded approximately 1,100 mm. In contrast, elevated vapour pressure deficit (VPD) and potential evapotranspiration (PET) were associated with reduced carbon storage. Topographic heterogeneity further influenced AGB, with rugged and concave terrains supporting potential biomass levels more than twice as high as those found in flat, convex areas. Our predictive map reveals a mosaic of low-biomass cores and localized high-biomass refugia, highlighting the dual influence of hydroclimatic and topographic factors. These findings reposition Caatinga as a heterogeneous and dynamic potential carbon reservoir – historically degraded by changes in land-use but still capable of storing substantial carbon. This research offers critical insights for the restoration, conservation and mitigation efforts for climate change in tropical drylands worldwide.