Geographical, temporal and environmental determinants of bryophyte species richness in the Macaronesian islands

Current Status of Liverwort Herbaria Specimens and Geographical Distribution in China

Specimen data play a crucial role in geographical distribution research. In this study, the collection information of liverwort specimens in China was compiled and analyzed to investigate the history, current status, and limitations of liverwort research in China. By utilizing the latest systematic research findings and corresponding environmental data, a niche model was developed to offer theoretical support for exploring the potential geographical distribution and diversity of liverwort resources. A total of 55,427 liverwort specimens were collected in China, resulting in the recording of 1212 species belonging to 169 genera and 63 families. However, there are imbalances in the distributions of liverwort data among different groups, collection units, and geographical areas, with families such as Lejeuneaceae, Porellaceae, and Plagiochilaceae having the highest number of specimens. Similarly, genera such as Porella, Frullania, and Horikawaella were well represented. Remarkably, 125 species had specimen counts exceeding 100. Unfortunately, approximately 51.77% of the species had fewer than 10 recorded specimens. There were four obvious peaks in the collection years of the bryophyte specimens in China, among which the largest collection occurred from 2010 to 2023. Notably, the number of specimens collected at different stages closely aligned with the history of taxonomic research on liverworts in China. The results of the integrity of the liverwort collection indicate that there is insufficient representation of some families and genera, with a concentration of common and widely distributed large families and genera. Tropical and subtropical humid areas are key regions for liverwort diversity, with water and temperature being the primary environmental factors influencing their geographical distribution. The specific temporal and spatial data of species recorded from plant specimens will enhance the study of species diversity, comprehensive protection, and sustainable utilization. Additionally, these data will contribute to the investigation of large-scale biodiversity distribution patterns and the impact of global change on diversity.

Management of non-indigenous species in Macaronesia: Misconceptions and alerts to decision-makers

Human-induced pressures have led to substantial changes in marine ecosystems worldwide, with the introduction of non-indigenous species (NIS) emerging as a significant threat to ecological, economic, and social aspects. The Macaronesian islands, comprising the Azores, Madeira, Canary Islands, and Cabo Verde archipelagos, are regions where the regional economy is dependent on marine resources (e.g., marine traffic, ecotourism and fisheries). Despite their importance, concerted efforts to manage marine biological invasions in Macaronesia have been scarce. In this context, the current study aims to contribute to the much-needed debate on biosecurity measures in this unique insular ecosystem to prevent and mitigate the impact of NIS. By adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria, this work validated and analyzed 260 documents providing insights into the management of NIS in Macaronesia until 2022. These documents revealed the presence of 29 Invasive Alien Species (IAS), most of which are misconceptions regarding this terminology. Most studies focused on the stages of early detection, rapid response, and eradication across the archipelagos. Cabo Verde had comparatively fewer studies. The most common techniques include monitoring/sampling, literature reviews, and taxonomic reviews. NIS introduction pathways were mainly attributed to transport (stowaway) and unaided migration, with ship fouling, ballast water, rafting, ocean currents, and tropicalization being also identified as significant contributors. This systematic review highlights the current efforts to establish robust biosecurity protocols in Macaronesia and emphasizes the urgent need to safeguard the region's ecological, economic, and social well-being.

Ecological drivers of taxonomic, functional, and phylogenetic diversity of bryophytes in an oceanic island

Montane oceanic islands possess unique geographic and ecological attributes, rendering them valuable for assessing patterns and drivers of alpha and beta taxonomic, functional, and phylogenetic diversity along elevational gradients. Such comparisons of diversity facets can provide insights into the mechanisms governing community assembly on islands. Herein, we aimed to characterize taxonomic, functional, and phylogenetic bryophyte diversity on Madeira Island within and across areas at varying elevations. We also assessed how these diversity facets for the alpha and beta components relate to ecological and anthropogenic factors. We estimated and compared alpha and beta taxonomic, functional, and phylogenetic diversity using 80 plots of 0.5 m × 0.5 m across the whole elevational gradient of the island. We compiled trait databases and supplemented them with our own observations. Phylogenetic information was sourced from the Moss and Liverwort Tree of Life. To assess the impact of ecological and anthropogenic factors on the three facets, we applied linear mixed-effects models and generalized dissimilarity models to alpha- and beta-diversity matrices, respectively. All facets of diversity exhibited strong correlations within both mosses and liverworts, indicating a substantial congruence when alpha and beta are analyzed separately. The bryophyte groups categorized by the growth form demonstrated contrasting patterns, aligning with their distinctive ecological requirements. While a mid-elevation peak emerged as a common pattern across the three facets of alpha diversity, beta diversity often displayed the opposite trend. Although the relative influence of environmental factors varied depending on the diversity facet and bryophyte grouping considered, we found that alpha and beta diversity of bryophytes are more influenced by climatic factors and the predominant type of vegetation than by anthropogenic factors. In the current context of global change, these results should be interpreted with caution, but they point to the resilience of bryophytes to survive in relatively well-preserved natural microhabitats within anthropogenic landscapes. In this study on Madeira Island, we investigated patterns and drivers of alpha and beta taxonomic, functional, and phylogenetic diversity along elevational gradients. We found that alpha and beta diversity of bryophytes are more strongly influenced by climatic factors and the predominant type of vegetation than by anthropogenic factors.

Testing differences of marine non-indigenous species diversity across Macaronesia using a standardised approach

The introduction of non-indigenous species (NIS) induces severe impacts on marine biodiversity and ecosystems. Macaronesia is an ecologically relevant region where several NIS were detected recently. For the first time, a standard experimental approach was designed to examine biofouling assemblages and investigate NIS across the region. In this context, sessile biofouling assemblages were examined in four recreational marinas in all the Macaronesian archipelagos from 2018 to 2020: the Azores, Madeira, Canary Islands, and Cabo Verde. We hypothesised that NIS numbers, abundance, and recruitment differed in each location due to abiotic and biotic features. From the Azores (higher latitudes) to Cabo Verde (lower latitudes), NIS recruitment and percentage cover decreased following a partial latitude gradient. The present study unveiled 25 NIS, with new records for the Azores (two cryptogenic species), Canary Islands (one NIS and two cryptogenic species), and Cabo Verde (three NIS and three cryptogenic species). The present research represents a pioneer and relevant step in advancing our current understanding of marine biological invasions in Macaronesia, employing a standard and low-cost approach.

Nuclear DNA Amounts in Chinese Bryophytes Estimated by Flow Cytometry: Variation Patterns and Biological Significances

There exists an obvious gap in our knowledge of the nuclear DNA amount of bryophytes, not only in terms of the low number of species represented, but also in systematic and geographic representation. In order to increase our knowledge of nuclear DNA amounts and variation patterns in bryophytes, and their potential phylogenetic significances and influences on phenotypes, we used flow cytometry to determine the DNA 1C values of 209 bryophyte accessions, which belong to 145 mosses and 18 liverworts collected from China, by using Physcomitrella patens as a standard. We quantified the differences in DNA 1C values among different orders and families and constructed a phylogenetic tree of 112 mosses with four gene sequences (nad5, rbcL, trnL-F, and 18S-ITS1-5.8S-ITS2-26S). DNA 1C values were mapped onto the phylogenetic tree to test a potential phylogenetic signal. We also evaluated the correlations of the DNA 1C value with the sizes of individuals, leaves, cells, and spores by using a phylogenetically controlled analysis. New estimates of nuclear DNA amounts were reported for 145 species. The DNA 1C values of 209 bryophyte accessions ranged from 0.422 pg to 0.860 pg, with an average value of 0.561 pg, and a 2.04-fold variation covered the extremes of all the accessions. Although the values are not significantly different (p = 0.355) between mosses (0.528 pg) and liverworts (0.542 pg), there are variations to varying extents between some families and orders. The DNA 1C value size exerts a positive effect on the sizes of plants, leaves, and cells, but a negative effect on spore size. A weak phylogenetic signal is detected across most moss species. Phylogenetic signals are comparatively strong for some lineages. Our findings show that bryophytes have very small and highly constrained nuclear DNA amounts. There are nucleotype effects of nuclear DNA amounts for bryophytes at the individual, organ, and cell levels. We speculate that smaller nuclear DNA amounts are advantageous for bryophytes in dry environments. Significant differences in the DNA 1C values among some moss families and orders, as well as phylogenetic signals for some lineages, imply that nuclear DNA amount evolution in mosses seems to be unidirectional.

Liverworts show a globally consistent mid‐elevation richness peak

The study of elevational gradients allows to draw conclusions on the factors and mechanisms determining patterns in species richness distribution. Several earlier studies investigated liverwort diversity on single or few elevational transects. However, a comprehensive survey of the elevational distribution patterns of liverwort richness and their underlying factors is lacking so far. This study's purpose was to fill this gap by compiling an extensive data set of liverwort elevational patterns encompassing a broad diversity of mountains and mountain ranges around the world. Using polynomial regression analyses, we found a prevalence of hump‐shaped richness patterns (19 of 25 gradients), where liverwort species richness peaked at mid‐elevation and decreased towards both ends of the gradient. Against our expectation and unlike in other plant groups, in liverworts, this pattern also applies to elevational gradients at mid‐latitudes in temperate climates. Indeed, relative elevation, calculated as the percentage of the elevational range potentially inhabited by liverworts, was the most powerful predictor for the distribution of liverwort species richness. We conclude from these results that the admixture of low‐ and high‐elevation liverwort floras, in combination with steep ecological gradients, leads to a mid‐elevation floristic turnover shaping elevational patterns of liverwort diversity. Our analyses further detected significant effects of climatic variables (temperature of the warmest month, potential evapotranspiration, and precipitation of the warmest month) in explaining elevational liverwort richness patterns. This indicates that montane liverwort diversity is restricted by high temperatures and subsequent low water availability especially towards lower elevations, which presumably will lead to serious effects by temperature shifts associated with global warming.

Taxon-dependent effects of dispersal limitation versus environmental filters on bryophyte assemblages-Multiple perspective studies in land-bridge islands

To explore the taxon-dependent contribution of dispersal limitation versus environmental filters to bryophyte assemblages. We investigated bryophytes and six environmental variables on 168 islands in the Thousand Island Lake,China. We compared the observed beta diversity with the expected values based on six null models (EE, EF, FE, FF, PE, and PF), detected the partial correlation of beta diversity with geographical distances. We quantified the contributions of spatial versus environmental variables and island isolation per se to species composition (SC) using variance partitioning. We modeled the species-area relationships (SARs) for bryophytes and the other eight biotas. To explore the taxon-dependent effects of spatial versus environmental filters on bryophytes, 16 taxa including five categories (total bryophytes, total mosses, liverworts, acrocarpous, and pleurocarpous mosses) and 11 species-richest families were included in the analyses. The observed beta diversity values were significantly different from the predicted values for all 16 taxa. For all five categories, the observed partial correlations between beta diversity and geographical distance after controlling environmental effects were not only positive, but also significantly different from the predicted values based on the null models. Spatial eigenvectors are more important in shaping SC than environmental variables for all 16 taxa except Brachytheciaceae and Anomodontaceae. Spatial eigenvectors contributed more to SC variation in liverworts than in mosses and in pleurocarpous mosses than in acrocarpous mosses. The effects of island isolation on SC were significant for all five categories, highly varied at the family level. The z values of the SARs for the five bryophyte categories were all larger than those of the other eight biotas. In subtropical fragmented forests, dispersal limitation exerted significant, taxon-dependent effects on bryophyte assemblages. It was dispersal limitation rather than environmental filtering that predominantly regulated the SC patterns of bryophytes.

Macaronesia as a Fruitful Arena for Ecology, Evolution, and Conservation Biology

Research in Macaronesia has led to substantial advances in ecology, evolution and conservation biology. We review the scientific developments achieved in this region, and outline promising research avenues enhancing conservation. Some of these discoveries indicate that the Macaronesian flora and fauna are composed of rather young lineages, not Tertiary relicts, predominantly of European origin. Macaronesia also seems to be an important source region for back-colonisation of continental fringe regions on both sides of the Atlantic. This group of archipelagos (Azores, Madeira, Selvagens, Canary Islands, and Cabo Verde) has been crucial to learn about the particularities of macroecological patterns and interaction networks on islands, providing evidence for the development of the General Dynamic Model of oceanic island biogeography and subsequent updates. However, in addition to exceptionally high richness of endemic species, Macaronesia is also home to a growing number of threatened species, along with invasive alien plants and animals. Several innovative conservation and management actions are in place to protect its biodiversity from these and other drivers of global change. The Macaronesian Islands are a well-suited field of study for island ecology and evolution research, mostly due to its special geological layout with 40 islands grouped within five archipelagos differing in geological age, climate and isolation. A large amount of data is now available for several groups of organisms on and around many of these islands. However, continued efforts should be made toward compiling new information on their biodiversity, to pursue various fruitful research avenues and develop appropriate conservation management tools.

Geographic Pattern of Bryophyte Species Richness in China: The Influence of Environment and Evolutionary History

How contemporary environment interacts with macroevolutionary processes to generate the geographic pattern of bryophyte species is still unresolved. China is very rich in bryophytes, with more than 3,000 bryophytes covering 70% of the families in the world. In this study, we assessed the effects of the contemporary environment (average temperature of the coldest season TCQ, precipitation of the warmest season PWQ, and elevational range) and the recent diversification rates (estimated as mean species number per genus, MSG) on the geographical pattern of species richness for bryophytes and two groups (i.e., liverworts and mosses) in China. We compiled the provincial level distribution of bryophyte species and estimated the geographic pattern of the recent diversification rate by MSG for species in China. Univariate, multivariate regressions and path model analyses were used to assess the relationships between species richness, MSG, and their potential environmental drivers. Species richness of all bryophytes and liverworts significantly increased with the increase of MSG, either in regressions or path analyses, indicating that provinces with high bryophyte richness were mainly inhabited by species (especially liverworts) from lineages with particularly high MSG. In contrast, the species richness of mosses was insignificantly decreased with MSG in univariate regression or insignificantly increased with MSG in path analysis. Both species richness and MSG of all bryophytes and liverworts increased with the increase in energy and water availability. In contrast, for mosses, the species richness significantly increased with the increase of energy and water availability, while MSG decreased with the increase of energy and water availability. The MSG of liverworts increase with the increase of elevational range but the MSG of mosses decrease with the increase of elevational range. Our study suggests that the humid tropical and subtropical mountains in China are not only diversity hotspots for bryophytes, but also cradles for high recent diversification of liverworts, and refuges for mosses to hold many monotypic and oligotypic genera.

Automated Discovery of Relationships, Models, and Principles in Ecology

Ecological systems are the quintessential complex systems, involving numerous high-order interactions and non-linear relationships. The most used statistical modeling techniques can hardly accommodate the complexity of ecological patterns and processes. Finding hidden relationships in complex data is now possible using massive computational power, particularly by means of artificial intelligence and machine learning methods. Here we explored the potential of symbolic regression (SR), commonly used in other areas, in the field of ecology. Symbolic regression searches for both the formal structure of equations and the fitting parameters simultaneously, hence providing the required flexibility to characterize complex ecological systems. Although the method here presented is automated, it is part of a collaborative human–machine effort and we demonstrate ways to do it. First, we test the robustness of SR to extreme levels of noise when searching for the species-area relationship. Second, we demonstrate how SR can model species richness and spatial distributions. Third, we illustrate how SR can be used to find general models in ecology, namely new formulas for species richness estimators and the general dynamic model of oceanic island biogeography. We propose that evolving free-form equations purely from data, often without prior human inference or hypotheses, may represent a very powerful tool for ecologists and biogeographers to become aware of hidden relationships and suggest general theoretical models and principles.

Different Predictors Shape the Diversity Patterns of Epiphytic and Non-epiphytic Liverworts in Montane Forests of Uganda

We studied the influence of regional and local variables on the liverwort diversity within natural forest vegetation of Uganda to contribute to our understanding of the mechanisms and processes determining species richness. To this end, we compared the species richness distribution patterns of epiphytic and non-epiphytic liverworts (Marchantiophytina) in 24 plots in the forests of four Ugandan national parks. We recorded a total of 119 species and subspecies from 18 families, including 16 new species records for the country. We used generalized linear models (GLMs) and the relative variable importance of regional and local climatic and environmental variables to assess their respective impact on the species diversity. We found that the richness patterns of total and epiphytic richness were largely driven by regional climatic factors related to temperature and water-availability. In contrast, species diversity of non-epiphytic and rare species was additionally strongly determined by local-scale microhabitat factors such as height of forest canopy and slope inclination, reflecting the availability of suitable microhabitats. We conclude that macroclimatic variables perform well in predicting epiphytic liverwort richness, whereas the adequate prediction of non-epiphytic richness requires site-specific variables. Also, we propose that richness of epiphytic liverworts will be impacted more directly by climate change than richness of non-epiphytic and rare species.

Seasonal variation of secondary metabolites in nine different bryophytes

Bryophytes occur in almost all land ecosystems and contribute to global biogeochemical cycles, ecosystem functioning, and influence vegetation dynamics. As growth and biochemistry of bryophytes are strongly dependent on the season, we analyzed metabolic variation across seasons with regard to ecological characteristics and phylogeny. Using bioinformatics methods, we present an integrative and reproducible approach to connect ecology with biochemistry. Nine different bryophyte species were collected in three composite samples in four seasons. Untargeted liquid chromatography coupled with mass spectrometry (LC/MS) was performed to obtain metabolite profiles. Redundancy analysis, Pearson's correlation, Shannon diversity, and hierarchical clustering were used to determine relationships among species, seasons, ecological characteristics, and hierarchical clustering. Metabolite profiles of Marchantia polymorpha and Fissidens taxifolius which are species with ruderal life strategy (R-selected) showed low seasonal variability, while the profiles of the pleurocarpous mosses and Grimmia pulvinata which have characteristics of a competitive strategy (C-selected) were more variable. Polytrichum strictum and Plagiomnium undulatum had intermediary life strategies. Our study revealed strong species-specific differences in metabolite profiles between the seasons. Life strategies, growth forms, and indicator values for light and soil were among the most important ecological predictors. We demonstrate that untargeted Eco-Metabolomics provide useful biochemical insight that improves our understanding of fundamental ecological strategies.

Oceanic island biogeography through the lens of the general dynamic model: assessment and prospect

The general dynamic model of oceanic island biogeography (GDM) has added a new dimension to theoretical island biogeography in recognizing that geological processes are key drivers of the evolutionary processes of diversification and extinction within remote islands. It provides a dynamic and essentially non-equilibrium framework generating novel predictions for emergent diversity properties of oceanic islands and archipelagos. Its publication in 2008 coincided with, and spurred on, renewed attention to the dynamics of remote islands. We review progress, both in testing the GDM's predictions and in developing and enhancing ecological-evolutionary understanding of oceanic island systems through the lens of the GDM. In particular, we focus on four main themes: (i) macroecological tests using a space-for-time rationale; (ii) extensions of theory to islands following different patterns of ontogeny; (iii) the implications of GDM dynamics for lineage diversification and trait evolution; and (iv) the potential for downscaling GDM dynamics to local-scale ecological patterns and processes within islands. We also consider the implications of the GDM for understanding patterns of non-native species diversity. We demonstrate the vitality of the field of island biogeography by identifying a range of potentially productive lines for future research.

Long-distance dispersal to oceanic islands: success of plants with multiple diaspore specializations

A great number of scientific papers claim that angiosperm diversification is manifested by an ample differentiation of diaspore traits favouring long-distance seed dispersal. Oceanic islands offer an ideal framework to test whether the acquisition of multiple sets of diaspore traits (syndromes) by a single species results in a wider geographic distribution. To this end, we performed floristic and syndrome analyses and found that diplochorous species (two syndromes) are overrepresented in the recipient flora of the Azores in contrast to that of mainland Europe, but not to mainland Portugal. An additional analysis of inter-island colonization showed a general trend of a higher number of islands colonized by species with a single syndrome (monochorous) and two syndromes than species with no syndrome (unspecialized). Nevertheless, statistical significance for differences in colonization is meagre in some cases, partially due to the low proportion of diplochorous species in Europe (244 of ∼10 000 species), mainland Portugal (89 of 2294 species), and the Azores (9 of 148 species), Canaries (17 of 387 lowland species) and Galápagos (18 of 313 lowland species). Contrary to expectations, this first study shows only a very marginal advantage for long-distance dispersal of species bearing multiple syndromes.