Three in four undescribed plant species are threatened with extinction

Tropical Land-Use Change Disrupts Zeta-Diversity Across Taxa

Land-use change causes community turnover via local extinction and colonisation of species, driving biotic homogenization or heterogenization at larger spatial scales. Quantification of these processes has focused on beta-diversity metrics, which upweight rarity and overlook the role of widespread species. A key knowledge gap is understanding the impact of land-use change on both rare and widespread species-zeta-diversity-allowing the detection of statistical patterns and drivers based on community turnover across space. We sampled bird, dung beetle, and orchid communities in 341 plots across natural (Andean forests and paramo) and transformed habitats (pasturelands) spanning ~270 km north-to-south in the Colombian Andes. We detected major losses in species richness following land-use conversion, which disrupts zeta-diversity across elevation in two ways. First, biodiversity patterns are rewired such that bird and dung beetle communities become structured by dispersal ability, overriding the effects of natural biogeographical drivers (i.e., elevation) and landscape conditions (i.e., canopy cover). Second, land-use change causes biotic homogenization across bird communities, with pasture retaining twice as many widespread species than natural habitats, and a four-fold reduction in widespread dung beetle species pointing to subtractive heterogenization. Orchid communities show high community turnover in both natural and transformed habitat. Our results show that the effect of local deforestation has a doubly devastating impact simplifying communities and reducing widespread species. Transforming natural habitats into anthropogenic landscapes may substantially raise extinction risk for communities composed of both widespread and rare species, especially in orchids as the most sensitive taxon.

Tracking hidden dimensions of plant biogeography from herbaria

Plants are diverse, but investigating their ecology and evolution in nature across geographic and temporal scales to predict how species will respond to global change is challenging. With their geographic and temporal breadth, herbarium data provide physical evidence of the existence of a species in a place and time. The remarkable size of herbarium collections along with growing digitization efforts around the world and the possibility of extracting functional traits and geographic data from preserved plant specimens makes them invaluable resources for advancing our understanding of changing species distributions over time, functional biogeography, and conserving plant communities. Here, I synthesize core aspects of plant biogeography that can be gleaned from herbaria along changing distributions, attributes (functional biogeography), and conservation biogeography across the globe. I advocate for a collaborative, multisite, and multispecies research to harness the full potential of these collections while addressing the inherent challenges of using herbarium data for biogeography and macroecological investigations. Ultimately, these data present untapped resources and opportunities to enable predictions of plant species' responses to global change and inform effective conservation planning.

The ecology of plant extinctions

Extinctions occur when enough individual plants die without replacement to extirpate a population, and all populations are extirpated. While the ultimate drivers of plant extinctions are known, the proximate mechanisms at individual and population level are not. The fossil record supports climate change as the major driver until recently, with land-use change dominating in recent millennia. Climate change may regain its leading role later this century. Documented recent extinctions have been few and concentrated among narrow-range species, but population extirpations are frequent. Predictions for future extinctions often use flawed methods, but more than half of all plants could be threatened by the end of this century. We need targeted interventions tailored to the needs of each threatened species.

No end to endemism - contributions to the difficult Nasa Weigend Series Alatae (Loasaceae). A new species from Peru and the rehabilitation of " Loasa" calycina Benth

A new species of Nasaser.Alatae (Urban & Gilg) Weigend from Northern Peru is described and illustrated. Nasakatjae sp. nov. was at first encountered by an observation on iNaturalist and subsequently collected in the humid Andean forests near Colasay in the province of Jaén (Cajamarca, Peru). Whilst comparing the new species with closely related Nasaloxensis (Kunth) Weigend, a taxon widespread in Southern Ecuador (and tentatively adjacent Peru), a reevaluation of the status of earlier synonymized Loasacalycina Benth. became necessary. Consequently, Nasacalycina comb. nov. is rehabilitated at species level and Nasaloxensis is redefined.

Plant diversity darkspots for global collection priorities

More than 15% of all vascular plant species may remain scientifically undescribed, and many of the > 350 000 described species have no or few geographic records documenting their distribution. Identifying and understanding taxonomic and geographic knowledge shortfalls is key to prioritising future collection and conservation efforts. Using extensive data for 343 523 vascular plant species and time-to-event analyses, we conducted multiple tests related to plant taxonomic and geographic data shortfalls, and identified 33 global diversity darkspots (those 'botanical countries' predicted to contain most undescribed and not yet recorded species). We defined priority regions for future collection according to several socio-economic and environmental scenarios. Most plant diversity darkspots are found within global biodiversity hotspots, with the exception of New Guinea. We identify Colombia, Myanmar, New Guinea, Peru, Philippines and Turkey as global collection priorities under all environmental and socio-economic conditions considered. Our study provides a flexible framework to help accelerate the documentation of global plant diversity for the implementation of conservation actions. As digitisation of the world's herbaria progresses, collection and conservation priorities may soon be identifiable at finer scales.

Spatial decoupling of taxon richness, phylogenetic diversity and threat status in the megagenus Erica (Ericaceae)

Estimates of the number of vascular plant species currently under threat of extinction are shockingly high, with the highest extinction rates reported for narrow-range, woody plants, especially in biodiversity hotspots with Mediterranean and tropical climates. The large genus Erica is a prime example, as a large proportion of its 851 species, all shrubs or small trees, are endemic to the Cape Floristic Region (CFR) of South Africa. Almost two hundred are known to be threatened and a further hundred are 'Data Deficient'. We need to target conservation efforts and research to fill the most problematic knowledge gaps. This can be especially challenging in large genera, such as Erica, with numerous threatened species that are closely related. One approach involves combining knowledge of phylogenetic diversity with that of IUCN threat status to identify the most Evolutionarily Distinct and Globally Endangered (EDGE) species. We present an expanded and improved phylogenetic hypothesis for Erica (representing 65% of described species diversity) and combine this with available threat and distribution data to identify species and geographic areas that could be targeted for conservation effort to maximise preservation of phylogenetic diversity (PD). The resulting 39 EDGE taxa include 35 from the CFR. A further 32 high PD, data deficient taxa are mostly from outside the CFR, reflecting the low proportion of assessed taxa outside South Africa. The most taxon-rich areas are found in the south-western CFR. They are not the most phylogenetically diverse, but do include the most threatened PD. These results can be cross-referenced to existing living and seed-banked ex situ collections and used to target new and updated threat assessments and conservation action.

Extinction risk predictions for the world's flowering plants to support their conservation

More than 70% of all vascular plants lack conservation status assessments. We aimed to address this shortfall in knowledge of species extinction risk by using the World Checklist of Vascular Plants to generate the first comprehensive set of predictions for a large clade: angiosperms (flowering plants, c. 330 000 species). We used Bayesian Additive Regression Trees (BART) to predict the extinction risk of all angiosperms using predictors relating to range size, human footprint, climate, and evolutionary history and applied a novel approach to estimate uncertainty of individual species-level predictions. From our model predictions, we estimate 45.1% of angiosperm species are potentially threatened with a lower bound of 44.5% and upper bound of 45.7%. Our species-level predictions, with associated uncertainty estimates, do not replace full global, or regional Red List assessments, but can be used to prioritise predicted threatened species for full Red List assessment and fast-track predicted non-threatened species for Least Concern assessments. Our predictions and uncertainty estimates can also guide fieldwork, inform systematic conservation planning and support global plant conservation efforts and targets.

Re-evaluating the importance of threatened species in maintaining global phytoregions

Anthropogenic introductions are known to be changing the structure of global phytogeographical regions (phytoregions), but previous studies have been limited by incomplete or biased data sets that are likely to underestimate the importance of threatened species. In this work, we analyse a comprehensive data set of all known species and their occurrences (at botanical country resolution) to quantify the impact of potential future extinction scenarios. We used Infomap, a network-based community detection algorithm, to generate phytoregional delineations for six species-distribution scenarios (native, introduced and extinctions of species that are either documented as threatened or likely to be threatened, as well as combinations thereof). We compared the numbers and sizes of phytoregions to characterise the amount and spatial distribution of changes in global phytoregions under each scenario. Extinctions of species that are predicted to be threatened had a greater homogenising effect on phytoregions than introductions, and there was some evidence that introductions may even mitigate the homogenisation caused by extinctions, though this interaction is complex. This research provides the first evidence that the loss of threatened species would have significant ramifications for global phytoregions and demonstrates the need to consider extinction processes in studies of anthropogenic effects on biodiversity patterns.

Why plant diversity and distribution matter

This article is the Editorial for the Special Collection ‘Global plant diversity and distribution’. See https://www.newphytologist.org/global-plant-diversity for more details.