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Past climatic refugia and landscape resistance explain spatial genetic structure in Oriental beech in the South Caucasus
AbstractPredicting species‐level effects of climatic changes requires unraveling the factors affecting the spatial genetic composition. However, disentangling the relative contribution of historical and contemporary drivers is challenging. By applying landscape genetics and species distribution modeling, we investigated processes that shaped the neutral genetic structure of Oriental beech (Fagus orientalis), aiming to assess the potential risks involved due to possible future distribution changes in the species. Using nuclear microsatellites, we analyze 32 natural populations from the Georgia and Azerbaijan (South Caucasus). We found that the species colonization history is the most important driver of the genetic pattern. The detected west–east gradient of genetic differentiation corresponds strictly to the Colchis and Hyrcanian glacial refugia. A significant signal of associations to environmental variables suggests that the distinct genetic composition of the Azerbaijan and Hyrcanian stands might also be structured by the local climate. Oriental beech retains an overall high diversity; however, in the context of projected habitat loss, its genetic resources might be greatly impoverished. The most affected are the Azerbaijan and Hyrcanian populations, for which the detected genetic impoverishment may enhance their vulnerability to environmental change. Given the adaptive potential of range‐edge populations, the loss of these populations may ultimately affect the specie's adaptation, and thus the stability and resilience of forest ecosystems in the Caucasus ecoregion. Our study is the first approximation of the potential risks involved, inducing far‐reaching conclusions about the need of maintaining the genetic resources of Oriental beech for a species' capacity to cope with environmental change.
Evolutionary history of Castanea sativa in the Caucasus driven by Middle and Late Pleistocene paleoenvironmental changes
Abstract Due to global climate cooling and aridification since the Paleogene, members of the Neogene flora were extirpated from the Northern Hemisphere or were confined to a few refugial areas. For some species, the final reduction/extinction came in the Pleistocene, but some others have survived climatic transformations up to the present. This has occurred in Castanea sativa, a species of high commercial value in Europe and a significant component of the Caucasian forests’ biodiversity. In contrast to the European range, neither the historical biogeography nor the population genetic structure of the species in its isolated Caucasian range has been clarified. Here, based on a survey of 21 natural populations from the Caucasus and a single one from Europe, we provide a likely biogeographic reconstruction and genetic diversity details. By applying Bayesian inference, species distribution modelling and fossil pollen data, we estimated (i) the time of the Caucasian—European divergence during the Middle Pleistocene, (ii) the time of divergence among Caucasian lineages and (iii) outlined the glacial refugia for species. The climate changes related to the Early–Middle Pleistocene Transition are proposed as the major drivers of the intraspecific divergence and European–Caucasian disjunction for the species, while the impact of the last glacial cycle was of marginal importance.
Forest genomics in the Caucasus through the lens of its dominant tree species – Fagus orientalis
AbstractThe last glacial period is known to have greatly influenced the demographic history of temperate forest trees, with important range contractions and post‐glacial expansions that led to the formation of multiple genetic lineages and secondary contact zones in the Northern Hemisphere. These dynamics have been extensively studied for European and North American species but are still poorly understood in other temperate regions of rich biodiversity such as the Caucasus. Our study helps filling that gap by deciphering the genomic landscapes of F. orientalis across the South Caucasus. The use of genome‐wide data confirmed a past demographic history strongly influenced by the Last Glacial Maximum, revealing two disjunct glacial refugia in the Colchis and Hyrcanian regions. The resulting patterns of genetic diversity, load and differentiation are not always concordant across the region, with genetic load pinpointing the location of the glacial refugia more efficiently than genetic diversity alone. The Hyrcanian forests show depleted genetic diversity and substantial isolation, even if long‐distance gene flow is still present with the main centre of diversity in the Greater Caucasus. Finally, we characterize a strong heterogeneity of genetic diversity and differentiation along the species chromosomes, with noticeably a first chromosome showing low diversity and weak differentiation.
Biological Flora of Britain and Ireland: Cytisus scoparius. No. 307
Abstract This account presents information on all aspects of the biology of Cytisus scoparius (L.) Link (Broom or Scotch Broom) (Sarothamnus scoparius (L.) W.D.J. Koch) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to the environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation. Broom is shade‐intolerant and drought‐tolerant, aided by c. 40% of net carbon fixation coming from stem photosynthesis and an ability to shed leaves in inclement periods. It is at its best in lowland, open, disturbed habitats but also open woodland; widespread across Britain, Ireland and much of Europe. It has been widely introduced to all continents (except Antarctica) where due to its prolific seeding and rapid spread it is often an invasive shrub. Broom thrives in an oceanic climate on a range of moist soils but is capable of invading arid and poor soils, helped by its ability to acquire 50% of its nitrogen from bacteria in root nodules. Broom is an obligate seeder, pollinated by a limited range of insects, primarily bees large enough to trip the explosive pollination mechanism. Seeds are dispersed explosively from the fruit and secondarily moved by ants attracted to the elaiosome. The water impermeable seed coat results in high dormancy, and so broom forms a significant seed bank. In Britain and Ireland, populations are showing little decline and broom is not considered to be at threat of extinction. In introduced areas, broom can rapidly spread despite browsing by native species and livestock. Biological control using a range of insects introduced from native areas, particularly seed eaters, together with mechanical and possibly chemical treatment, is showing some promise in its control.
Niche modelling suggests low feasibility of assisted gene flow for a Neogene relict tree, Castanea sativa Mill.
Abstract: As many tree species populations are being degraded by climate change, adaptive conservation, and forest management, such as assisted gene flow (AGF), can provide the genetic variation needed to adapt to climate change. The core of this strategy is to assist the adaptation process in populations at risk of climate maladaptation by introducing individuals with beneficial alleles to cope with expected climate changes. Castanea sativa Mill. (sweet chestnut) is an essential component of natural forests in the Mediterranean and Caucasian regions, with a long history of cultivation. Current climate change may seriously threaten the long-term persistence of the species, particularly in the Caucasus region, where the largest range reductions are predicted. Here, we used Species Distribution Models (SDMs) to assess the feasibility of AGF in European and Caucasian populations of Castanea sativa. Bioclimatic variables for present (1981–2010) and future (2071–2100) conditions were obtained from the CHELSA climate database. The final models of future species ranges were averaged across three climate models (IPSL-CM6A-LR, MPIESM1-2-HR and UKESM1-0-L) and three climate change scenarios – SSP1-2.6, SSP3-7.0 and SSP5-8.5. There are marked differences in the climatic niches of the Iberian, Alpine-Apennine, Balkan, and Caucasian populations, with significant implications for AGF. The most suitable European areas for the Caucasian populations were found only in the Adriatic region. The Iberian populations were not compatible with the predicted future climate in the Caucasus in any of the scenarios tested. Suitable areas for Alpine-Apennine populations within the AGF strategy were predicted in the Colchic lowlands, the eastern Pontic mountains and the Hyrcanian forests in the SSP1-2.6 and SSP3-7.0 climate change scenarios. In contrast, the Balkan populations would be compatible at most with the western Pontic mountains and, to a lesser extent, with the Hyrcanian forests. According to the most damaging climate scenario SSP5-8.5, the potential of AGF in the Caucasus with Alpine-Apennine and Balkan populations could be very limited. Our study showed limited applicability of AGF for Castanea sativa between the European and Caucasian populations due to low climate match. Genomic modelling is needed to fully assess the feasibility of this strategy in the species.
High genetic connectivity of common juniper in Scandinavia: Implication for management of genetic resources
Biodiversity protection against anthropogenic climate change: Conservation prioritization of Castanea sativa in the SouthCaucasus based on genetic and ecological metrics
AbstractThe climate drives species distribution and genetic diversity; the latter defines the adaptability of populations and species. The ongoing climate crisis induces tree decline in many regions, compromising the mitigation potential of forests. Scientific‐based strategies for prioritizing forest tree populations are critical to managing the impact of climate change. Identifying future climate refugia, which are locations naturally buffering the negative impact of climate change, may facilitate local conservation. In this work, we conducted the populations' prioritization for Castanea sativa (sweet chestnut), a Neogene relict growing in the Caucasus global biodiversity hotspot. We generated genetic and ecological metrics for 21 sites in Georgia and Azerbaijan, which cover the natural range of sweet chestnut across the region. We demonstrated that climate primarily drives the pattern of genetic diversity in C. sativa, proved with a significant isolation‐by‐environment model. In future, climate change may significantly reorganize the species' genetic diversity, inducing even some genetic loss, especially in the very distinct eastern fringe of the species range in Azerbaijan. Based on our combined approach, we mapped populations suitable for ex situ and in situ conservation, accounting for genetic variability and the location of future climate refugia.
Biological flora of Britain and Ireland: Viscum album, No. 303
AbstractThis account presents information on all aspects of the biology ofViscum albumL. (Mistletoe) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of theBiological Flora of Britain and Ireland: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation.Viscum albumis a widespread obligate hemiparasite on a wide range of angiosperm and gymnosperm trees. Once thought to take just water and nutrients from its host via a haustorium, it is now suggested to also take carbon. Heavy infestations can reduce host vitality through prolific water use and carbon removal.Flowers are highly reduced but are primarily pollinated by flies, ants and bees. Seeds are dispersed by birds. Removal of the epicarp is necessary for successful seedling establishment, and seeds have a sticky viscin coat, adhering it to the host bark. Vegetative spread also happens under the bark of its host resulting in densities of >700 Mistletoe plants per host.Viscum albumis a lowland species, most frequent in open human‐made habitats extending into woodlands in Europe. It has been widely planted for folklore use centred around Christmas. Despite conservation concerns following removal of Mistletoe‐laden old orchards, the species is thriving and needs control in some areas. Viscotoxins and lectins in leaves and shoots have been widely used in herbal medicine and now potentially in complementary cancer therapy.
The evolutionary heritage and ecological uniqueness of Scots pine in the Caucasus ecoregion is at risk of climate changes
AbstractScots pine is one of the most widely occurring pines, but future projections suggest a large reduction in its range, mostly at the southern European limits. A significant part of its range is located in the Caucasus, a global hot-spot of diversity. Pine forests are an important reservoir of biodiversity and endemism in this region. We explored demographic and biogeographical processes that shaped the genetic diversity of Scots pine in the Caucasus ecoregion and its probable future distribution under different climate scenarios. We found that the high genetic variability of the Caucasian populations mirrors a complex glacial and postglacial history that had a unique evolutionary trajectory compared to the main range in Europe. Scots pine currently grows under a broad spectrum of climatic conditions in the Caucasus, which implies high adaptive potential in the past. However, the current genetic resources of Scots pine are under high pressure from climate change. From our predictions, over 90% of the current distribution of Scots pine may be lost in this century. By threatening the stability of the forest ecosystems, this would dramatically affect the biodiversity of the Caucasus hot-spot.
Adaptive Silviculture and Climate Change—A Forced Marriage of the 21st Century?
Climatic changes significantly impact forest ecosystems, inevitably affecting forestry and forest-related industry. Considering that most forests are actively managed, there is a need to define the future risks and set a strategy for forestry and silviculture in a changing world. This review provides insight into the new challenges and opportunities forest management and silviculture face in the coming decades. There is sound recognition of risk factors expected from climate change, yet great uncertainty exists in the predictions of the response of forests to new conditions. Additionally, the stakeholders’ interests in the goods and services offered by forests are changing, and this also needs to be taken into account in future forest management. Undoubtedly, the goal of future forestry and silviculture in the 21st century will be primarily to ensure the continuity and sustainability of the forest. Sustainable use of goods and ecosystem services from forests will be directly related to the continuity and sustainability of the forest in the future. Adaptive forest management aims to promote the adaptive capacity of forests to new conditions resulting from climate change. If adaptation efforts are effective, adaptive forest management should be a kind of risk management. There is no one-fits-all strategy for adaptation to uncertain future conditions. Silviculture in the 21st century is expected to be more conducive to adapting forests to changes. Operational silvicultural activities should focus on ensuring the resilience and adaptation of forests to future environmental conditions. Modern silviculture offers activities that fall within the scope of contemporary close-to-nature silviculture practices. However, some of the currently applied practices will require review and modification to be applicable under new conditions. This review also identifies the need to fill knowledge gaps in order to develop more effective and flexible adaptation strategies to foster sustainable forest development and, thus, sustainable forestry.
Climate warming, ecological dynamics and nature conservation drive tree diversity in Wigierski National Park, Poland
In response to ongoing climate warming, tree species adapted to colder climates are expected to shift their geographic ranges northward. Within the framework of long-term ecological monitoring in Wigry National Park (northeastern Poland), observed changes in forest biocenoses reflect the combined influence of climate change and natural ecological dynamics. This study compares dendroflora composition and diversity between two monitoring periods, 2011 and 2024, as part of an ongoing effort to track climate-related ecological shifts. Tree observations and measurements were carried out using concentric circular plots. In the largest plots, all trees with a diameter at breast height (d.b.h.) ≥ 12 cm were recorded by species, and their d.b.h. was measured. In the smaller plots, all trees with a d.b.h. ≥ 2 cm and < 2 cm but taller than 30 cm were similarly identified and measured. Data were recorded with Field-Map software integrated with an electronic calliper. The species-level taxonomic data, individual counts and basal area per species and plot were used to calculate biodiversity indices. Over the 13-year interval, a marked increase in overall dendroflora diversity was observed. Notably, the dominance of canopy-forming conifers – Pinus sylvestris and, to a lesser extent, Picea abies – measured as the proportion of individuals or stem density, has declined. This decline of coniferous species has been accompanied by an increase in the abundance and diversity of broadleaved deciduous species, including Tilia cordata, Quercus robur, Betula pendula, and Acer platanoides. Other thermophilous deciduous taxa also exhibited upward trends in both presence and abundance. Furthermore, the exponential of Shannon entropy, reached the highest value when evergreen conifers comprised 35% of the stand composition in 2011 and 18% in 2024. This finding suggests that maximum dendroflora diversity reaches its highest level at an intermediate proportion of conifers presence, rather than under conifers dominance or absence. Collectively, the processes occurring in Wigierski National Park illustrate the gradual shift in ecotonal forest ecosystems from cold-adapted coniferous species to broadleaved deciduous taxa due to ongoing climate change.
Stomatal density in Pinus sylvestris as an indicator of temperature rather than CO2: Evidence from a pan-European transect
AbstractThe commonly observed negative relationship between stomatal density (SD) and atmospheric CO2 has led to SD being proposed as an indicator of atmospheric CO2 concentration. The use of SD as a proxy for CO2, however, has been hampered by an insufficient understanding of the intraspecific variation of this trait. We hypothesized that SD in Pinus sylvestris, a widely distributed conifer, varies geographically and that this variation is determined by major climatic variables. By sampling needles from naturally growing trees along a latitudinal range of 32.25°, equivalent to 13.7°C gradient of mean annual temperature (MAT) across Europe, we found that SD decreased from the warmest southern sites to the coldest sites in the north at a rate of 4 stomata per mm2 for each 1°C, with MAT explaining 44% of the variation. Additionally, samples from a provenance trial exhibited a positive relationship between SD and the MAT of the original localities, suggesting that high SD is an adaptation to warm temperature. Our study revealed one of the strongest intraspecific relationships between SD and climate in any woody species, supporting the utility of SD as a temperature, rather than direct CO2, proxy. In addition, our results predict the response of SD to climate warming.
Genetic and biometric patterns of rangewide divergence of iconic, Neogene relic broadleaved shrub species Staphylea pinnata L.– post-glacial expansion and human impact
Abstract Integrative phylogeographic studies supported by morphometric analysis and genetic data provide significant insights into the postglacial recolonization history and other factors shaping current distributions of plant species, including major forest-forming trees in Europe. However, genomic resources and phylogeographic knowledge of shrub species remain limited. Staphylea pinnata L. (European bladdernut) is a shrub native to thermophilous broadleaf forests and is the only representative of the Staphyleaceae in Central Europe. Given its historical associations with human and religious beliefs dating back to pre-Christian cultures, the current distribution of this iconic, Neogene relic species has been hypothesized to be influenced by human-assisted migration. This study aims to address this hypothesis by uncovering the genetic and morphometric relationships among S. pinnata populations across its wide distribution range in Europe, Caucasus and the Anatolian Peninsula, linking these findings with existing archaeobotanical and ethnobotanical data. We sampled 87 populations (979 individuals), genotyped them with the applications of newly developed genetic markers, and conducted morphological leafs’ measurements to estimate the postglacial expansion and human impact on the current distribution of S. pinnata. Both genetic and morphometric results indicate primarily natural post-glacial recolonization from two Pleistocene glacial refugia in the Apennines and Balkans. Additionally, we identified “suture zones” of increased genetic diversity in middle latitudes, resulting from secondary contact due to postglacial recolonization from different sources. Significant human contributions were observed towards the northernmost edge of the species’ range, including regions such as Eastern France, Lower Silesia in Poland, and Northern Podolia in Ukraine.