Herbarium collections constitute permanent and often well-documented records of the distribution of taxa through space and time. Since their creation, their uses have dramatically expanded and with many new uses being proposed, including some for which herbaria were not initially intended for. In this paper we assess the potential of these collections on conservation biology, by providing exemplary studies that use herbarium specimens, grouped into four categories: (1) based on occurrence data, such as studies about plant extinction or introduction, or those focused on modelling their ecological niche; (2) based on the specimens themselves, such as morphological or phenological studies to evaluate the impact of climate change; (3) based in genetic data, such as phylogeographic or taxonomical studies; and (4), other applied studies.

INaturalist defines itself as an “online social network of people sharing biodiversity information to help each other learn about nature” and it is likely one of the largest citizen science web portals in the world, as every year millions of observations across thousands of species are gathered and collectively compiled by an engaged community of nearly 3 million users (November 2023). The strengths and potentialities that explain the success of the platform are reviewed and include, among others, its usability and low technical requirements, immediacy, open-access, the possibility of interacting with other users, artificial-intelligence-aided identification, versatility and automatic incorporation of the validated records to GBIF. iNaturalist has, however, features that scientists need to carefully consider when using it for their research, making sure that the quality of observations does not limit or hinder its usefulness in plant research. While these are identified (e.g., the lack of representative photographs for many observations or the relatively frequent identification errors), we provide some suggestions to overcome them and, by doing so, improve the use and add value to iNaturalist for plant research.

Ethnobotany takes into account past uses to be projected into the present and future. Most current ethnobotanical research is focused, especially in industrialised countries, on obtaining information of plant uses from elderly people. Historical ethnobotany is less cultivated, although papers have demonstrated its interest. Particularly poor, but potentially very relevant, is the attention paid to historical herbaria as a source of data on useful plants. Bearing this in mind, we studied the herbarium of the Catalan pharmacist and naturalist Francesc Bolòs (1773-1844), which contains information on medicinal uses and folk names, with the aim of establishing a catalogue of plants and uses and tracing them through old and contemporary literature. The ca. 6000 plant specimens of this herbarium were investigated to assess those including plant uses and names. These taxa have been thoroughly revised. The data have been tabulated, their biogeographic profile, possible endemic or threatened status, or invasive behaviour have been assessed, and the content regarding medicinal uses, as well as folk names, has been studied. The medicinal terms used have been interpreted as per current days' medicine. The popular names and uses have been compared with those appearing in a certain number of works published from 11th to 20th centuries in the territories covered by the herbarium and with all the data collected in 20th and 21st centuries in an extensive database on Catalan ethnobotany. A total of 385 plant specimens (381 taxa) have been detected bearing medicinal use and folk names information. We collected data on 1107 reports of plant medicinal properties (in Latin), 32 indications of toxicity, nine reports of food use, and 123, 302 and 318 popular plant names in Catalan, Spanish and French, respectively. The most quoted systems are digestive, skin and subcutaneous tissue (plus traumatic troubles) and genitourinary. Relatively high degrees of coincidence of plant names and uses in the herbarium and the literature comparison set have been found. Of the taxa contained in this medicinal herbarium, 294 were native to the Iberian Peninsula, and 86 were alien. Neither endemic nor threatened taxa have been detected, whereas a considerable portion of the alien taxa shows invasive behaviour at present. Our analyses indicate a certain degree of consistency between the medicinal uses of plants recorded in this 18th and 19th century herbarium and the records found in the literature and in recent ethnobotanical datasets, accounting for the robustness of pharmaceutical ethnobotanical knowledge in the area considered. Data appearing on the specimen labels are numerous, pointing out the herbarium as a relevant source of ethnopharmacological information. Special attention should be paid to some original uses contained in the herbarium's labels for further investigation on plant properties and drug design.

Invasive alien species are currently considered one of the main threats to global biodiversity. One of the most rapidly expanding invasive plants in recent times is Kalanchoe × houghtonii (Crassulaceae), an artificial hybrid created in the 1930s in the United States by experimental crossings between K. daigremontiana and K. tubiflora, two species endemic to Madagascar. Thanks to its large colonizing capacity (mainly derived from the production of asexual plantlets), K. × houghtonii soon escaped from cultivation and quickly spread in many parts of the world. However, its actual range is not well known due to the lack of a formal description until recent times (2006) and its strong morphological resemblance with one of its parentals (K. daigremontiana). The present study was aimed, in the first instance, to delimit the present distribution area of K. × houghtonii at the global scale by gathering and validating all its occurrences and to track its colonization history. Currently, K. × houghtonii can be found on all continents except Antarctica, although it did not reach a global distribution until the 2000s. Its potential distribution, estimated with MaxEnt modelling software, is mainly centered in subtropical regions, from 20° to 40° of both northern and southern latitudes, mostly in areas with a high anthropogenic activity. Unexpectedly, concomitant to a poleward migration, future niche models suggest a considerable reduction of its range by up to one-third compared to the present, which might be related with the Crassulaceaean Acid Metabolism (CAM) of K. × houghtonii. Further research may shed light as to whether a decrease in potential habitats constitutes a general pattern for Crassulaceae and CAM plants.

Cities are often hotspots for biological invasions, showing much higher percentages of alien species than non-urbanized settings. The reasons are multiple and are mostly related to two main factors: their heterogeneous, highly disturbed habitats and their many gateways that allow alien species introduction (e.g., airports, roads, train stations, or gardens). In addition to being a sink of biological invasions, cities can also be a source of the spread of alien species into surrounding landscapes, which adds further complexity to this issue. Herein, we are presenting the results of a five-year survey of the alien flora of Montjuïc, the largest urban hill in Barcelona (Spain). In just about 3.4 km², we recorded up to 247 alien plant taxa, a figure much higher than those of many other Mediterranean cities and which clearly points to the role of Montjuïc as a hotspot for alien plants. The comparison with the alien flora of its surrounding region (coastal Catalonia) suggests that the alien flora of Montjuïc would have become enriched through many immigration episodes from close geographic areas. The hill, however, would have also acted as a source of the spread of alien plants, and indeed, some species have not been detected yet beyond the confines of Montjuïc. This study aims to be a key tool to ensure early detection and also to develop appropriate management and/or eradication actions.