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Carbon-concentrating mechanisms (CCMs) are a widespread phenomenon in photosynthetic organisms. In vascular plants, the evolution of CCMs ([C44-carbon compound] and crassulacean acid metabolism [CAM]) is associated with significant shifts, most often to hot, dry and bright, or aquatic environments. If and how CCMs drive distributions of other terrestrial photosynthetic organisms, remains little studied. Lichens are ecologically important obligate symbioses between fungi and photosynthetic organisms. The primary photosynthetic partner in these symbioses can include CCM-presenting cyanobacteria (as carboxysomes), CCM-presenting green algae (as pyrenoids) or green algae lacking any CCM. We use an extensive dataset of lichen communities from eastern North America, spanning a wide climatic range, to test the importance of CCMs as predictors of lichen ecology and distribution. We show that the presence or absence of CCMs leads to opposite responses to temperature and precipitation in green algal lichens, and different responses in cyanobacterial lichens. These responses contrast with our understanding of lichen physiology, whereby CCMs mitigate carbon limitation by water saturation at the cost of efficient use of vapor hydration. This study demonstrates that CCM status is a key functional trait in obligate lichen symbioses, equivalent in importance to its role in vascular plants, and central for studying present and future climate responses.

Changes in flowering can cause misalignment with pollinators and seed dispersers, thus causing changes in fitness of both the plant species and their mutualists. Phenological shifts in tropical flowering plants are poorly documented despite the widely understood importance of measuring flowering phenology. It has been hypothesized that changes in tropical flowering have been less severe than those in non-tropical latitudes due to minimal change in temperature annually. Furthermore, many tropical species flower continuously throughout the year, as they are not restricted by a cold induced dormancy period. To test this hypothesis, we used museum specimens to examine shifts in phenology of flowering plant species from across the global tropics. We identified species that flower once a year, every year, for four consecutive months or less, as these species can best be compared to temperate studies. This selection criteria resulted in 33 species across the tropics. Between 1794 and 2024, we documented an average absolute shift in flowering of 2.04 days per decade across all species, with a range of 0.037 days per decade to 14.10 days per decade. This shift is comparable to changes seen elsewhere around the globe, including those in temperate, boreal and alpine desert plants. This change has been shown to be severe enough to cause interspecific misalignment. Our work shows that changes in tropical flowering phenology are not insulated from the impacts of climate change, as previously assumed.

Acanthaceae are among the most taxonomically diverse, geographically widespread, and morphologically and ecologically variable lineages of flowering plants. Most modern workers have estimated more than 4000 species and potentially more than 5000 species worldwide, thus placing Acanthaceae among the 12 or so most diverse families of angiosperms. This diversity is marked by exceptional morphological variation, particularly with respect to floral forms, growth forms, and pollen types. The present work represents a synthesis of knowledge generated over the past two decades on the taxonomy and systematics of this complex plant family. We place all 191 accepted genera within a revised classification of the family. Dichotomous keys (nine in total) to recognize the major lineages of Acanthaceae are presented together with geographically partitioned keys to all genera, covering (a) Africa, Madagascar, the Mediterranean region, and Arabia; (b) Asia and Australasia; and (c) the Americas. Finally, we validate several new tribes, subtribes, and genera, and provide new combinations for species where generic delimitation has changed. Our hope is that the present contribution serves to benefit future research on the systematics of Acanthaceae and provides a foundation upon which future classification efforts can be built.

Aim Understanding ecological distributions of global biodiversity is stymied by incomplete knowledge of drivers of species rarity. These include trade‐offs among life‐history traits that impact dispersability, competition, reproductive output and speciation and extinction. In this study, we aim to understand potential drivers of rarity in North American lichens. Location and methods With nearly 5500 species and a third of global species richness, North America is a hotspot for lichen biodiversity. Here, we employ a continental‐scale dataset on North American lichens to test potential drivers of species rarity. For all species, we determined coarse‐scale geographical distribution along with the mode of reproduction, substrate, growth form and photobiont type. Results Our analyses found that most lichens are rare and known only from one or two ecoregions. Rare species are not equally distributed across ecoregions: the Eastern temperate hardwood forests and wet tropical forests of southern Florida harbour the vast majority of rare species. Wet to seasonally wet ecoregions of western North America are home to most remaining narrowly distributed lichen species. In contrast, northern ecoregions along with drier ecoregions including the Great Plains and deserts harbour primarily widespread species. Lichen rarity is significantly associated with species that live on bark or leaves, those with a Trentepohlia photobiont, those that are small, crustose and live closely appressed to their substrates, and those that reproduce sexually, dispersing only the mycobiont. North American lichens are represented unevenly across trait categories, with 65% of them having a crustose growth form, 73% bearing a Trebouxia or other green algal photobiont, 78% living on bark or rock and 77% reproducing sexually. Main conclusions Our study, spanning an entire continental‐scale biota, helps to establish a generalized relationship among life‐history traits and rarity in lichens and highlights the significance of biotic interactions in structuring biogeographical distributions.

It has been shown that changes in plant flowering times are directly tied to climate change, often being the first and most visible indicators of a broader, ecosystem-wide change. Despite this, tropical latitudes have been markedly understudied. We analyzed 19 tropical species across seven locations from 1960 to 2021. Through a series of Bayesian regression analyses of flowering date on maximum temperature, minimum temperature, and precipitation, we found that flowering dates of tropical plants have changed substantially with changes in climate. Flowering dates have shifted an average of 6.9 days per °C of maximum temperature change, 4.5 days per °C of minimum temperature change, and 0.28 days per mm precipitation. We then computed combined effects of the aforementioned climate variables and found that flowering dates have shifted 15.0 days per unit of combined temperature and precipitation changes (computed as the sum of products of standardized changes in climate variables and their posterior effect estimates). We found no meaningful difference in magnitude of change in flowering of species in consistently hot and wet locations to those in locations with seasonal wet and dry periods (Wilcoxon rank sum, P>0.05). Our study demonstrates that tropical ecosystems are not insulated from the impacts of climate change.

Background Anthocyanins are major pigments contributing to flower coloration and as such knowledge of molecular architecture underlying the anthocyanin biosynthetic pathway (ABP) is key to understanding flower color diversification. To identify ABP structural genes and associated regulatory networks, we sequenced 16 transcriptomes generated from 10 species of Ruellia and then conducted co-expression analyses among resulting data. Results Complete coding sequences for 12 candidate structural loci representing eight genes plus nine candidate regulatory loci were assembled. Analysis of non-synonymous/synonymous (dn/ds) mutation rates indicated all identified loci are under purifying selection, suggesting overall selection to prevent the accumulation of deleterious mutations. Additionally, upstream enzymes have lower rates of molecular evolution compared to downstream enzymes. However, site-specific tests of selection yielded evidence for positive selection at several sites, including four in F3'H2 and five in DFR3 , and these sites are located in protein binding regions. A species-level phylogenetic tree constructed using a newly implemented hybrid transcriptome–RADseq approach implicates several flower color transitions among the 10 species. We found evidence of both regulatory and structural mutations to F3′5'H in helping to explain the evolution of red flowers from purple-flowered ancestors. Conclusions Sequence comparisons and co-expression analyses of ABP loci revealed that mutations in regulatory loci are likely to play a greater role in flower color transitions in Ruellia compared to mutations in underlying structural genes.

Understanding the spatial distributions of rarity and diversity is crucial for both targeted conservation efforts and elucidating the mechanisms that underpin species richness patterns. Existing studies suggest local communities with greater species richness also hold higher numbers of low abundance species. Rarity hotspots at the global scale tend to be spatially divergent from species richness hotspots and differ among many taxonomic groups, but much less work has been done to understand rarity patterns at the regional scale. Here, we used a large-scale dataset of comprehensive lichen diversity from a global biodiversity hotspot in eastern North America to explore the relationships of rarity, species richness, and elevation, while also examining the key plot characteristics that support increased rarity within the system. We found a mid-elevation slump in lichen rarity, with increased rarity at low and high elevations, contrasting with the mid-elevation hump in species richness for lichens in the same system. Additionally, important plot-level predictors of rarity changed with elevation. Rocky, open habitats hosted increased levels of rarity at low elevations, and the highest, coldest plots at the high elevations also hosted increased levels of rarity. Our results illustrate a contrast between elevational patterns and important plot characteristics for lichen rarity and species richness, suggesting a need for separate, complementary conservation efforts to protect both areas with high species richness and areas with high numbers of rare species.

Trail development is more prevalent as tourism develops globally. The depth effect of trail development on plant diversity and native species’ stress response via tuning flavonoids in natural ecosystems remain relatively poorly understood. We investigated the depth effects by comparing plant species diversity and flavonoid contents (of six common native species) in sampling plots plots (Rabbit Mountain Open Space, Boulder County, CO, USA) with varying distances away from trail. We found plant diversity to be lowest in plots immediately proximal to trails and highest in intermediate plots. We also found the concentrations of total flavonoids to vary significantly between plots closer and away from trails. Specifically, we found the concentrations of isoorientin and myricetin higher in plots closer to trails. On the contrary, the concentrations of vitexin and kaempferol were higher in plots away from trails. Quercetin was higher in the intermediate plots. Overall, trail development negatively impacted herbaceous plant diversity, which was evident as depth effects. The plant species responded to environmental stresses imposed by trail development through fine-tuned flavonoid accumulation.

Biatoropsis hirtae and B. minuta are reported from Colorado, to our knowledge for the first time. These species were found growing on thalli of Usnea hirta and U. perplexans, respectively, during recent specimen collecting by the authors in the Front Range Mountains of north-central Colorado. The occurrences of these species throughout North America are likely more common and geographically broader than presently understood owing to frequent overlooking of populations. We provide discussion of their geographical ranges as presently understood and other notes of interest regarding species of Biatoropsis known from the United States. Hasta donde sabemos, este es el primer registro de la presencia de Biatoropsis hirtae y B. minuta en Colorado. Estas especies se encontraron creciendo en los talos de Usnea hirta y U. perplexans respectivamente durante una reciente recolección de especímenes en las montañas Front Range del centro-norte de Colorado. Es probable que su presencia en toda Norteamérica sea más común y geográficamente más amplia de lo que se cree en la actualidad debido a la frecuente superposición de poblaciones. Proporcionamos una discusión acerca de los rangos geográficos tal como se entienden actualmente y de otras notas de interés concerniente a las especies de Biatoropsis conocidas de los Estados Unidos.

Sarcogyne similis is found to produce psoromic acid, a substance previously known from only one other species in the family Acarosporaceae. Study of more than one hundred specimens from throughout the range of S. similis confirms the species is widely distributed from Nova Scotia, Canada, south throughout much of the eastern United States, and westward through the Sonoran Desert to southern California, where it occurs on non-calcareous rocks, especially sandstone. The recently proposed synonymy with S. reebiae is confirmed. Sarcogyne similis f. convexa is lectotypified with material that contains psoromic acid. The type of S. californica, currently treated as a synonym of S. similis, does not produce psoromic acid and may belong to a separate taxon. The distribution of S. dakotensis, which produces norstictic acid, appears to be nearly allopatric with S. similis.