Arthur Whistler

Abstract Trichomes are diverse and functionally important plant structures that vary in response to selection pressures across ecological gradients and evolutionary timescales. Classic hypotheses predict higher investment in trichomes in arid environments, at lower latitudes, and in long-lived species, as well as shifts in trichome production to reduce conflict between defense traits and mutualisms. However, tests of these hypotheses often rely on aggregate trichome metrics and neglect the rich diversity of trichome phenotypes. Here, we collected data on fine-scale patterns of trichome length, density, and type in 52 species of blazingstars (Mentzelia: Loasaceae) and tested whether individual trichome traits were consistent with existing adaptive hypotheses. Contrary to longstanding hypotheses, we found that Mentzelia species tend to display greater trichome investment in less arid environments and at higher latitudes. Barbed trichomes are significantly less common on the upper surface of the leaf, possibly reducing defense-pollination conflict. Species with larger petals (a proxy for reliance on insect pollinators) also shift investment away from insect-trapping hairs on the underside of the leaf. Examining trichome types separately revealed that different morphologies show distinct responses to abiotic and biotic factors, demonstrating the need to consider multiple axes of diversity when testing adaptive hypotheses for complex traits.

AbstractPremiseBiotic disjunctions have attracted scientific attention for the past 200 years. Despite being represented in many familiar plants (such as bald cypress, flowering dogwood, sweetgum, partridgeberry, etc.), the eastern North American (ENA)–Mexican (M) disjunction remains poorly understood. Major outstanding questions include the divergence times of taxa exhibiting the disjunction and environmental/geological processes that may underlie the disjunction. Symphyotrichum Nees (Asteraceae), one of the most diverse genera in the eastern USA, displays several examples of disjunct ENA–M taxa.MethodsWe generated target capture data using the Angiosperms353 baitset and generated the first well‐sampled phylogenomic hypothesis for Symphyotrichum and its close relatives. Focusing on S. subgenus Virgulus, we used MCMCTREE to perform divergence time estimation and the R package BioGeoBEARS to infer ancestral regions and biogeographic transitions between North America and Mexico. Finally, we used the ancestral niche reconstruction method Utremi to test for a role of historical aridification in generating the disjunction.ResultsOur molecular data suggest a recent radiation of Symphyotrichum at the Plio‐Pleistocene boundary (~2.5 mya), with early connections to Mexico in ancestral lineages that closed off shortly after and were followed by vicariance across this region. Except for some present‐day broadly distributed species, there is a complete lack of movement between ENA and M after ~0.5 mya.ConclusionsA reconstructed disjunct distribution of suitable habitat in Pleistocene climatic models corroborates results from biogeographic modeling and confirms glacial cycles are more likely to be associated with the breakup of ENA–M biogeographic connections.

Context Mapping the distribution of species from the genus Metrosideros is crucial for developing surveillance and management plans associated with species conservation in response to issues such as rapid ‘ōhi‘a death spread in the south-central Pacific region. Aims To support this endeavour, we recognised there was a need for open and reliable geographic information system data on island locations, extents, and occurrence data of Metrosideros species. Methods Using an open science framework, we reviewed six sources of island data and five sources of species occurrence data for availability, accuracy, and licencing criteria. Key results OpenStreetMap emerged as the optimal island location data, offering accuracy, precision, and open licencing, with this data improved and reprojected for mapping purposes. The Global Biodiversity Information Facility provided the majority of Metrosideros species occurrence data, but analysis of occurrence data from iNaturalist revealed common mis-identifications with regional biases that were corrected prior to compilation. The occurrence data of Metrosideros species was also supplemented by vegetation plot data, with HAVPlot and sPlotOpen providing key additional data for some species and islands. Conclusions Citizen science data via iNaturalist and OpenStreetMap formed the core of the compiled datasets. While such crowdsourced data can have quality issues, with additional crowdsourced curatorial effort these datasets will be significant and scalable sources of data into the future. Implications All compiled occurrence and GIS data are made openly available via permissive data licences to better support future biogeographical research in the south-central Pacific region.

Without appropriate and ongoing management interventions, weeds will continue to economically and environmentally disadvantage agricultural and natural ecosystems. For these management strategies to have long‐term sustained success, they need to carefully consider the biological aspects of the targeted weed. These strategies will also need to consider potential adaptations evolved by the targeted weed in response to a range of selection pressures imposed by anthropogenetic factors, climate change, changing environmental conditions, and inappropriate or unsuccessful management regimes. One group of weeds that has been observed to readily adapt to a wide range of conditions and has shown considerable challenges in their management is invasive grasses. Adding to these challenges is that several invasive grasses have also developed resistance to a range of herbicide modes of action, which, to date, has been one of the most commonly used methods of control. To address these challenges, this review explores the biology and ecology of the globally invasive annuals Echinochloa crus‐galli (Barnyard grass) and Panicum capillare (Witchgrass), and the perennial Sorghum halepense (Johnson grass) to identify (i) the most suitable management options for their control and (ii) potential research gaps that may assist in the future management direction of these species. Based on the findings of this review, it is clear that an integrated management approach that targets different aspects of the plant's biology, in combination with early detection and treatment and ongoing surveillance, is necessary for the long‐term control of these species. Although a combination of methods appears promising, further investigation still is required to evaluate their efficiency and long‐term success in a changing environment, all of which are further discussed within this review.

Cold tolerance strategies in plants vary from structural to biochemical permitting many plants to survive and grow on sites that experience freezing conditions intermittently. Although tree ferns occur predominantly across the tropics, they also occur in temperate zones and occasionally in areas that experience sub‐zero temperatures, and how these large ferns survive freezing conditions is unknown. Many temperate tree fern taxa are marcescent – retaining whorls of dead fronds encircling the upper trunk – or develop short or prostrate trunks, possibly to insulate against frost damage to their trunks and growing crowns. We asked the following questions: 1) do global growth patterns and traits of tree ferns respond to freezing conditions associated with latitude and elevation, 2) do growth patterns of tree ferns in New Zealand vary along a temperature‐related gradient, and 3) do marcescent tree fern skirts insulate the growing crown from sub‐zero temperatures? To establish what morphological adaptations permitted the Cyatheales to occur in biomes that experience intermittent sub‐zero temperatures and frost, we 1) reviewed the global distributions of these structural and morphological traits within the tree ferns (Cyatheales); 2) assessed the patterns of tree fern marcescence, and other traits potentially associated with cold tolerance (no trunk, prostrate, short‐trunked) of nine taxa of the Cyatheales along environmental gradients across New Zealand; and 3) conducted a field experiment to assess the thermal insulation properties of tree fern marcescent skirts. We identified significant trends among growth forms, marcescence, and environmental gradients consistent with our hypothesis that these are adaptations to tolerate cold. Our field experiments provide quantitative evidence that marcescent skirts have a strong insulating effect on tree fern trunks. The Cyatheales have evolved several strategies to protect the pith cores of their trunks from extreme cold temperatures in temperate forests allowing them to capture niche space in environments beyond the tropics.

Lonicera japonica, an importante rsource plant, possesses significant medicinal, economic, and ecological value. To understand its response to climate change and to optimize its conservation and utilization, this study employed the Biomod2 ensemble model to predict its potential distribution under future climate scenarios and identified key environmental factors influencing its distribution. The results showed that under current climatic conditions, the potential distribution of honeysuckle is primarily concentrated in low-altitude regions of central and eastern China and the Sichuan Basin. In future scenarios, the overall distribution pattern changes less, and the area of highly suitable habitats slightly decreases by 0.80%. Distribution analysis indicated a trend of northward migration towards higher latitudes. Temperature-related factors, including temperature seasonality, the minimum temperature of the coldest month, the mean temperature of the coldest quarter, and the annual mean temperature, were identified as dominant factors affecting its distribution. The Biomod2 ensemble model significantly improved the precision and accuracy of suitability predictions compared to single models, providing a scientific basis for predicting the future geographic distribution of honeysuckle and for establishing and utilizing its cultivation regions in China.

Before European contact, natural grasslands covered relatively little of Hawai‘i, with a grass flora composed of ∼48 species including 40 endemics. Following the proliferation of cattle ranches after the Great Mahele (land division) in the 1840s, it was quickly realized that the native grasses were not suitable for high intensity grazing. This sparked the importation of “improved” pasture grasses and set the path toward the contemporary dominance of foreign grasses across Hawai‘i. The importation of foreign grasses for forage accelerated dramatically in the early 1900s with the establishment of the Hawai‘i Agriculture Experiment Station (HAES) on O‘ahu by the United States government. The HAES imported seed, trialed grasses in introduction gardens, and distributed seed to ranchers across the islands. I performed a systematic review of literature produced by the HAES and similar organizations, newspapers, herbarium specimens, and floristic treatments to compile a record for the timeline of grass introductions, provide detailed historical context surrounding the introduction of these grasses, and reassess the status of species of controversial nativity. In total, 577 grasses were introduced post-1778, 158 of which were likely accidental introductions whereas 419 were deliberately imported. There are 232 species of grasses naturalized in Hawai‘i, including 102 deliberately introduced and 130 likely accidental. Deliberate introductions comprise the majority of invasive species which invade natural areas, whereas most accidental introductions are weeds associated with human disturbances. While deliberate introductions largely plateaued after 1970, new accidental introductions and some deliberate introductions with long lag periods continue to naturalize, with 30 newly naturalized grass species recorded between 2000 and 2023.

Exotic species are those growing in areas outside their natural distribution and can cause negative impacts on local biodiversity, such as ecological imbalance, competition with native species and changes in ecosystems functioning. Ipomoea obscura (L.) Ker Gawl., native to tropical and subtropical Asia and Africa, and exotic in Australia, Caribbean region and North America, is reported here as the first verified record for South American territory, in the state of Maranhão, Northeast Brazil. This species, known as “Obscure Morning Glory”, has invasive potential and can negatively affect local biodiversity. Recording exotic species in the initial stages of invasion, as well as understanding their biology and taxonomy, is essential for planning strategies to prevent their spread. Here we present a description, comments on phenological period, distribution, taxonomic notes, ecology and uses, as well as photos and illustration.

Some plant lineages remain within the same biome over time (biome conservatism), whereas others seem to adapt more easily to new biomes. The c. 398 species (14 genera) of subfamily Cercidoideae (Leguminosae or Fabaceae) are found in many biomes around the world, particularly in the tropical regions of South America, Asia and Africa, and display a variety of growth forms (small trees, shrubs, lianas and herbaceous perennials). Species distribution maps derived from cleaned occurrence records were compiled and compared with existing biome maps and with the literature to assign species to biomes. Rainforest (144 species), succulent (44 species), savanna (36 species), and temperate (10 species) biomes were found to be important in describing the global distribution of Cercidoideae, with many species occurring in more than one biome. Two phylogenetically isolated species-poor temperate ( Cercis ) and succulent ( Adenolobus ) biome lineages are sister to two broadly distributed species-rich tropical clades. Ancestral state reconstructions on a time-calibrated phylogeny suggest biome shifts occurred throughout the evolutionary history of the subfamily, with shifts between the succulent and rainforest biomes, from the rainforest to savanna, from the succulent to savanna biome, and one early occurring shift into (or from) the temperate biome. Of the 26 inferred shifts in biome, three are closely associated with a shift from the ancestral tree/shrub growth form to a liana or herbaceous perennial habit. Only three of the 13 inferred transcontinental dispersal events are associated with biome shifts. Overall, we find that biome shifts tend to occur within the same continent and that dispersals to new continents tend to occur within the same biome, but that nonetheless the biome-conserved and biogeographically structured Cercidoideae have been able to adapt to different environments through time.

Herbarium specimens provide an important and central resource for biodiversity research. Making these records digitally available to end-users represents numerous challenges, in particular, transcribing metadata associated with specimen labels. In this study, we used the citizen science initiative ‘Les Herbonautes’ and the Récolnat network to transcribe specific data from all herbarium specimen labels stored at the Muséum national d’Histoire naturelle in Paris of the large tropical plant family Annonaceae. We compared this database with publicly available global biodiversity repository data and expert checklists. We investigated spatial and taxonomic advances in data availability at the global and country scales. A total of 20 738 specimens were transcribed over the course of more than two years contributing to and significantly extending the previously available specimen and species data for Annonaceae worldwide. We show that several regions, mainly in Africa and South East Asia not covered by online global datasets, are uniquely available in the P herbarium, probably linked to past history of the museum’s botanical exploration. While acknowledging the challenges faced during the transcription of historic specimens by citizen scientists, this study highlights the positive impact of adding records to global datasets both in space and time. This is illustrative for researchers, collection managers, policy makers as well as funders. These datasets will be valuable for numerous future studies in biodiversity research, including ecology, evolution, conservation and climate change science.