ABSTRACT Background The role and relative importance of ecological processes (herbivory, fire) and human actions in shaping the pre-farming landscape of temperate north-west Europe is controversial, particularly in relation to processes that could have led to an open vegetation structure. Aims Reconstruct the changing role of herbivory, fire, and human activity in shaping a landscape in north-west Europe. Methods We present a multi-proxy study from a sedimentary record at an archaeological site on the Meuse floodplain (Netherlands). We reconstruct local vegetation cover (phytoliths, macrofossils), regional vegetation cover (pollen), depositional and aquatic environment (sediment physical properties, diatoms and aquatic macrofossils), herbivory (non-pollen palynomorphs) and fire (charcoal). Results High herbivory and low fire activity characterised the pre-farming landscape. Regional-scale vegetation dynamics were stable, the vegetation being dominated by trees, but local vegetation fluctuated periodically between open and closed canopy. Cultivation commenced around 6500 years ago (elevated Cerealia-type pollen), and subsequently, fire activity increased (c. 6500 years ago), and herbivores disappeared (c. 5200 years ago). Conclusions Herbivory in the pre-farming landscape maintained a dynamic mosaic of open vegetation within a forest matrix, which ceased when cultivation began. Our data show that humans have fundamentally changed the balance between herbivory and fire dynamics over thousands of years.

ABSTRACT Background Urban green and blue-green infrastructures (GI/BGI) support a wide range of ecosystem services, including e.g. flood mitigation, water and air quality improvements, biodiversity enhancement, and climate regulation. Vegetation is a central component of GI/BGI, yet effective implementation requires interdisciplinary knowledge exchange among scientists, planners, practitioners, policymakers, and the public. Methods This review explores the role of vegetation in the GI/BGI framework by synthesising foundational definitions, historical evolution of the concepts, and a range of ecosystem services provided by GI/BGI. It examines literature and case studies with a focus on biodiversity, plant dispersal, and the use of digital tools and mathematical models for ecosystem assessment. Results Hydrology, vegetation and interconnectedness among components constitute three principal pillars for the GI/BGI concepts. GI/BGI systems contribute to aesthetic improvements, enhanced biodiversity, microclimate regulation, and protection of downstream waterbodies. Barriers such as policy fragmentation and underestimation of benefits are discussed, along with potential trade-offs and disbenefits. Brownfield sites emerged as important for urban biodiversity. The role of digital tools in modelling species dispersal and evaluating GI/BGI benefits is demonstrated through international case studies. The paper also provides an outline of a model representing the spread of biological species through the GI/BGI network and its potential application for assessment of biodiversity of plants, animals, fungi and algae in urban environments. Conclusion Vegetation plays a critical role in GI/BGI and its successful implementation relies on interdisciplinary approaches, knowledge exchange and stakeholder collaboration. Further research should address knowledge gaps in biodiversity patterns and biogeochemical cycles, particularly through comparative ecosystem analysis and development of adaptive management strategies.

ABSTRACT Urban landscapes provide a range of man-made habitats wherein certain plants can flourish. These species benefit from (i) a warmer and drier microclimate (ii) substrates with a relatively high base status derived from calcium-rich building materials and (iii) plenty of open ground including gardens, parks and derelict sites (iv) ‘corridors’ within the landscape enabling efficient dispersal of seeds and other propagules. Urban species are regarded by many as ‘weeds to be eradicated’, but they contribute to environmental services including food for insect life, cooling, flood control and aesthetic appeal, creating also a biodiverse environment, enhancing human health and well-being. In this Special Issue we bring together the somewhat disparate strands of enquiry about plant life in cities, and raise questions about how Local Authorities should manage the flora of their towns and cities.

ABSTRACT Background There have been early reports that suggested that floras of towns and cities have more species than their rural counterparts. If so, this suggests that human settlements have a role to play in nature conservation. Aims To test two hypotheses: (i) that there are more species in urban areas than in adjacent rural areas and (ii) that alien species are more frequent in the built environment. Methods Species lists from these two data sets were examined: (i) the 1970–2023 database of the Botanical Society of Britain and Ireland and (ii) the 2015–2023 database of the species and habitats from the Urban Flora project of the Botanical Society of Scotland. Results The two largest cities, Glasgow and Edinburgh, contain at least 1,141 and 1,226 vascular plant species, respectively, and just over 50% of these are aliens. Smaller settlements and nearby rural areas are less species-rich with a higher proportion of native species. In all five cities, urban areas are more species-rich than surrounding rural areas. Conclusions The largest settlements are species-rich because of (i) the diversity of habitats (ii) human actions and (iii) favourable microclimates. The original hypotheses are broadly supported.

ABSTRACT Background Machair is a rare, semi-natural dune grassland, restricted to the north-west coast of Scotland and Ireland. It is of conservation importance due to its high diversity of wildflowers, and the presence of rare species of plants and wildlife. Maintained by low-intensity crofting agriculture, more detailed knowledge of current management practices and their impacts is required. Aims To investigate the effects of traditional crofting agriculture, specifically seasonal grazing and low-intensity rotational cultivation, on flowering plant species richness and composition of machair. Methods Vegetation survey data from the Outer Hebrides were collected and analysed to compare species richness and composition among four types of agricultural management, broadly defined as follows: uncultivated and year-round grazed; uncultivated and seasonally grazed; rotationally cultivated and ungrazed; both rotationally cultivated and seasonally grazed. Results Both seasonal grazing and rotational cultivation increased species richness, with a combination of the two resulting in the highest species richness. Cultivation had a stronger impact on species composition than grazing, with annual species in particular benefiting from rotational cultivation. Conclusions Consistent with previous studies, our results identify traditional management regimes as important in maintaining machair plant diversity. The study provides a preliminary but detailed view of current machair management in the Outer Hebrides.

ABSTRACT Background A large increase in surface growth on building façades has stimulated ongoing research on identifying colonising organisms and their impact on colonised surfaces. Aims This paper focuses on the characterisation of initial ecological succession on building surfaces. Methods Diverse investigations were used in an interdisciplinary approach to study early colonisation on modern building surfaces. Results More than 200 different taxa have been identified as part of the early succession so far. Most of the diversity is contributed by algae and cyanoprokaryota, followed by fungi. Remarkably, bryophytes and lichens also make up an important part of the rich biodiversity on building surfaces. Along with the identification of the microorganisms their ecological thresholds become apparent. Façade algae may be active in a range of relative humidities from 68% to 100% and fungi from ca. 73.3% upwards. The upper temperature limits lie at 57°C for active and may surpass 100°C for the dormant stage. The lowest temperature for physiological activity of façade organisms is ca. −15°C. Surface growth on masonry develops in seasonal cycles. Conclusions This overview covers succession, management of growth on buildings and deliberate greening of vertical building surfaces. New approaches for surface greening technologies with algae and bryophytes are on the way. The current discussions relate to whether microbial surface colonisation on buildings should be controlled or enhanced as a functional part of man-made ecosystems.

ABSTRACT Background The flora of Northern Europe has a complex glacial history, with species recolonising via different migration routes. However, traditional genetic markers have often struggled to resolve subtle population structure arising from closely located or cryptic refugia. Aims This study investigated the phylogeography of the widespread plant species Euphrasia micrantha in Scotland, using genome skimming to detect complex patterns of recolonisation. Methods We recovered complete plastid genomes and partial nuclear ribosomal DNA arrays for 145 individuals of E. micrantha and sympatric species. Phylogeographic histories are inferred from comparative phylogenetics and haplotype diversity measures. Results We identified a plastid haplotype group unique to E. micrantha, and present only in northern Scotland, while two other genetic clusters were intermixed with co-occurring species. Within the unique plastid lineage, we detected subtle east–west genetic divergence. Conclusions E. micrantha recolonised Scotland from multiple distinct refugia, potentially including cryptic northern refugia. The genetic distinctiveness of northern Scottish E. micrantha suggests a cryptic lineage, and/or this species’ distinct ecology and mating system maintain population differences. Genome skimming is likely to be useful in many other phylogeographic studies requiring dense population sampling.

ABSTRACT Background Hybridisation plays a key role in plant evolution. The extent to which parental divergence can predict the outcome of hybridisation (e.g. the ability to form hybrids and hybrid fertility) has most often been studied using a small number of individuals and/or DNA barcodes which could result in erroneous measures of parental divergence. Aims This study investigated the relationship between genetic divergence and the formation and fertility of hybrids, using Epilobium sect. Epilobium (willowherbs) of the British Isles as a model. Methods We used reduced representation sequencing to generate a phylogeny of Epilobium, which vary in their propensity to hybridise. Genetic distance was compared to the occurrence and seed set of hybrids using the literature available on this genus. Results A phylogeny constructed from 3522 quality-filtered SNPs from 44 samples of 10 species and four putative hybrid individuals, resolved all but one species as monophyletic. Two hybrid individuals were confirmed, and one additional hybrid was identified. All were likely to be F1 hybrids. Conclusion We did not detect a significant relationship between parental divergence and hybridisation likelihood and/or hybrid fertility in Epilobium sect. Epilobium, contradicting the hypothesis that increasing genetic divergence decreases hybrid formation and hybrid fertility.

ABSTRACT Background The recent colonisation of Carex salina in Scotland presents an opportunity to compare population genetic structure with long-established Norwegian populations. The closely related long-established Scottish C. recta allowed removal of the potentially confounding effects of latitude. Aims To compare genetic diversity, balance between clonal and sexual reproduction, clonal architecture in new and long-established populations of C. salina and C. recta, respectively. Methods Simple sequence repeat markers were used to quantify genetic parameters within all extant populations of C. recta and C. salina in Scotland and in C. salina sampled across its latitudinal range in Norway. Results Scottish and Norwegian populations of C. salina, and Scottish C. recta showed similar levels of expected heterozygosity. Almost all populations showed heterozygote excess. Clonality was lowest in Scottish C. salina. The few Scottish C. salina clones were large with very little overlap. By comparison, Norwegian C. salina and Scottish C. recta had smaller, overlapping clones. Conclusion Scottish saltmarshes have been colonised by C. salina on multiple occasions with insufficient time for extensive clonal growth to occur. It will be instructive to undertake future examination of the genetic structure of these Scottish populations to assess how they change over time.

ABSTRACT Background Habitat creation and enhancement using commercial wildflower seeds to combat biodiversity loss are increasing. However, potential genetic and adaptive impacts of these practices on the remnant populations and on ecosystem processes are not well understood for most species and regions. Aims This study assesses the potential impacts of habitat creation and enhancement by wildflower reintroductions. We focus on red campion (Silene dioica) in Great Britain (GB) , and determine whether wild and commercial populations differ in their genetic diversity and trait variation. Methods Seeds from 10 wild GB populaitons and two commercial red campion sources were grown in a common garden experiment to compare growth and reproductive traits. Genetic variation was analysed to compare genetic diversity and genetic differentiation . Results Significant phenotypic differences were found among wild populations, indicating spatially structured variation. Commercial populations exhibited greater vegetative size than wild populations suggestive of cultivation-associated selection. Genetic analysis revealed that both wild and commercial populations were genetically diverse, but commercial populations were distinct from wild populations. Conclusions Commercial plantings of red campion could potentially influence local genetic diversity and adaptation. The study highlights urgent need for further studies across species to provide evidence-based guidelines for conservation management of plant introductions