Climatic Niche Models Research Articles

Evaluation of climate conditions and ecological traits that limit the distribution expansion of alien Lolium rigidum in Japan

Invasive alien plants cause severe global problems; therefore, determining the factors that lead to the success or failure of invasion is a critical question in the field of invasion ecology. In this study, we aimed to determine the factors underlying differences in the distribution range of alien plants in Japan by investigating why Lolium multiflorum thrives in a wide range of habitats while L. rigidum is mainly distributed on sandy beaches. We initially evaluated environmental niche suitability through species distribution modelling and subsequently examined whether species traits influence the differences in range expansion between the two species. We used MaxEnt modelling to identify potential environmental niches for both species. The analysis revealed that L. rigidum was considerably less suited to the Japanese climate compared to L. multiflorum, with high summer precipitation in Japan identified as one of the climatic factors limiting the distribution of L. rigidum. Given that these winter annual plants remain dormant as seeds during summer, in subsequent experiments, we buried seeds in paddy field soil and sandy beach sand during summer and evaluated their survival rate in autumn. The survival rate of L. rigidum seeds was significantly lower than that of L. multiflorum, particularly in paddy soil. Factors contributing to seed mortality may include the decay or early germination of L. rigidum seeds under Japan’s high rainfall conditions. This study emphasises the importance of considering local environmental factors alongside climate niche modelling in the risk assessment of invasive species. Moreover, the integration of species distribution modelling for large-scale evaluations and manipulation experiments for fine-scale assessments proved effective in identifying climatic conditions and species traits influencing the success or failure of alien species invasion.

Ice age-driven range shifts of diploids and expanding autotetraploids of Biscutella laevigata within a conserved niche.

Early studies of the textbook mixed-ploidy system Biscutella laevigata highlighted diploids restricted to never-glaciated lowlands and tetraploids at high elevations across the European Alps, promoting the hypothesis that whole-genome duplication (WGD) is advantageous under environmental changes. Here we addressed long-held hypotheses on the role of hybridisation at the origin of the tetraploids, their single vs multiple origins, and whether a shift in climatic niche accompanied WGD. Climatic niche modelling together with spatial genetics and coalescent modelling based on ddRAD-seq genotyping of 17 diploid and 19 tetraploid populations was used to revisit the evolution of this species complex in space and time. Diploids differentiated into four genetic lineages corresponding to allopatric glacial refugia at the onset of the last ice age, whereas tetraploids displaying tetrasomic inheritance formed a uniform group that originated from southern diploids before the last glacial maximum. Derived from diploids occurring at high elevation, autotetraploids likely inherited their adaptation to high elevation rather than having evolved it through or after WGD. They further presented considerable postglacial expansion across the Alps and underwent admixture with diploids. Although the underpinnings of the successful expansion of autotetraploids remain elusive, differentiation in B. laevigata was chiefly driven by the glacial history of the Alps.

Whole Genomes Inform Genetic Rescue Strategy for Montane Red Foxes in North America.

A few iconic examples have proven the value of facilitated gene flow for counteracting inbreeding depression and staving off extinction; yet, the practice is often not implemented for fear of causing outbreeding depression. Using genomic sequencing, climatic niche modeling, and demographic reconstruction, we sought to assess the risks and benefits of using translocations as a tool for recovery of endangered montane red fox (Vulpes vulpes) populations in the western United States. We demonstrated elevated inbreeding and homozygosity of deleterious alleles across all populations, but especially those isolated in the Cascade and Sierra Nevada ranges. Consequently, translocations would be expected to increase population growth by masking deleterious recessive alleles. Demographic reconstructions further indicated shallow divergences of less than a few thousand years among montane populations, suggesting low risk of outbreeding depression. These genomic-guided findings set the stage for future management, the documentation of which will provide a roadmap for recovery of other data-deficient taxa.

Phylogenetic climatic niche evolution and diversification of the Neurergus species (Salamandridae) in the Irano-Anatolian biodiversity hotspot.

This study explores how climate variables influenced the evolution and diversification of Neurergus newts within the Irano-Anatolian biodiversity hotspot. We use a dated phylogenetic tree and climatic niche models to analyze their evolutionary history and ecological preferences. Using genetic data from nuclear (KIAA) and mitochondrial (16s and 12s) genes, we estimate divergence times and identify four major Neurergus clades. The initial speciation event occurred approximately 11.3 million years ago, coinciding with the uplift of the Zagros and Anatolian mountains. This geological transformation isolated newt populations, likely triggering the first speciation event. By integrating potential geographic distribution with climate variables, we reconstruct ancestral niche occupancy profiles. This highlights the critical roles of temperature and precipitation in shaping Neurergus habitat preferences and distribution. We observe both phylogenetic niche conservatism and divergence, with niche divergence playing a dominant role in diversification. This research emphasizes the complex interplay of geography, climate, and ecology in speciation and the vulnerability of isolated mountain newt populations to environmental changes.

Can species climate niche predict canopy growth, functional traits and phenotypic plasticity in urban trees?

There is much uncertainty in how climate change will impact the performance of urban trees. Climate niche modelling predicts that many urban tree species may become unsuitable in future climates, but this has rarely been tested in cities. Broad planting of diverse tree species in different cities provides the opportunity to test climate niche predictions. Here we investigated if the climate of origin of 14 urban tree species influenced tree growth, trait expression, and phenotypic plasticity. We determined climate niche limits for all species and measured canopy growth rates of individual trees from 2013 to 2021 in the two largest Australian cities: subtropical Sydney, and temperate Melbourne. Six functional traits including leaf water potential at turgor loss point (TLP), wood density (WD), leaf dry matter content (LDMC), specific leaf area (SLA), carbon isotope composition (δ13C) and Huber value (HV) were measured in both cities. Trees planted outside their climate niche limits had lower growth than trees planted inside their climate niche in the temperate but not subtropical city. Species with lower MAP of origin (i.e., drier) had faster canopy growth in both cities. Species with low MAP and high heat moisture index (HMI) at their origin had more negative TLP and greater WD, indicating species from drier environments maintain their high drought tolerance in cities. Trees planted in drier Melbourne had more negative TLP, higher WD and higher LDMC than in Sydney, demonstrating phenotypic plasticity in urban trees. Wetter origin species showed greater phenotypic plasticity in TLP, WD and δ13C. Canopy RGR was negatively related with δ13C reflecting a strong impact of stomatal behaviour on urban tree growth. Our study provides limited support that species climate niche limits reliably predict urban tree growth, so we caution against solely using climate niche matching and advocate for inclusion of functional traits when selecting urban tree species.

Climate change may reveal currently unavailable parts of species' ecological niches.

The ability of climatic niche models to predict species extinction risks can be hampered if niches are incompletely quantified. This can occur when niches are estimated considering only currently available climatic conditions, disregarding the fact that climate change can open up portions of the fundamental niche that are currently inaccessible to species. Using a new metric, we estimate the prevalence of potential situations of fundamental niche truncation by measuring whether current ecological niche limits are contiguous to the boundaries of currently available climatic conditions for 24,944 species at the global scale in both terrestrial and marine realms and including animals and plants. We show that 12,172 (~49%) species are showing niche contiguity, particularly those inhabiting tropical ecosystems and the marine realm. Using niche expansion scenarios, we find that 86% of species showing niche contiguity could have a fundamental niche potentially expanding beyond current climatic limits, resulting in lower-yet still alarming-rates of predicted biodiversity loss, particularly within the tropics. Caution is therefore advised when forecasting future distributions of species presenting niche contiguity, particularly towards climatic limits that are predicted to expand in the future.

Predicting the site productivity of forest tree species using climate niche models

Species occurrence-based climate niche models (CNMs) serve as valuable tools for predicting the future ranges of species’ suitable habitats, aiding the development of climate change adaptation strategies. However, these models do not address an essential aspect - productivity, which holds economic significance for timber production and ecological importance for carbon sequestration and ecosystem services. In this study, we investigated the potential to extend the CNMs to predict species productivity under various climate conditions. Lodgepole pine (Pinus contorta Dougl. ex Loud.) and Douglas-fir (Pseudotsuga menziesii Franco.) were selected as our model species due to their comprehensive range-wide occurrence data and measurement of site productivity. To achieve this, we compared and optimized the performance of four individual modeling algorithms (Random Forest (RF), Maxent, Generalized Boosted Models (GBM), and Generalized Additive Model (GAM)) in reflecting site productivity by evaluating the effect of spatial filtering, and the ratio of presence to absence (p/a ratio) observations. Additionally, we applied a binning process to capture the overarching trend of climatic effects while minimizing the impact of other factors. We observed consistency in optimal performance across both species when using the unfiltered data and a 1:1.5 p/a ratio, which could potentially be extended to other species. Among the modeling algorithms explored, we selected the ensemble model combining RF and Maxent as the final model to predict the range-wide site productivity for both species. The predicted range-wide site productivity was validated with an independent dataset for each species and yielded promising results (R2 above 0.7), affirming our model’s credibility. Our model introduced an innovative approach for predicting species productivity with high accuracy using only species occurrence data, and significantly advanced the application of CNMs. It provided crucial tools and insights for evaluating climate change's impact on productivity and holds a better potential for informed forest management and conservation decisions.

The drivers of dark diversity in the Scandinavian mountains are metric‐dependent

AbstractQuestionDark diversity refers to the set of species that are not observed in an area but could potentially occur based on suitable local environmental conditions. In this paper, we applied both niche‐based and co‐occurrence‐based methods to estimate the dark diversity of vascular plant species in the subarctic mountains. We then aimed to unravel the drivers explaining (a) why some locations were missing relatively more suitable species than others, and (b) why certain plant species were more often absent from suitable locations than others.LocationThe Scandinavian mountains around Abisko, northern Sweden.MethodsWe calculated the dark diversity in 107 plots spread out across four mountain trails using four different methods: two co‐occurrence‐based (Beals’ index and the hypergeometric method) and two niche‐based (the climatic niche model and climatic niche model followed by species‐specific threshold). We then applied multiple Generalized Linear Mixed‐Effects Models and General Linear Models to determine which habitat characteristics and species traits contributed the most to dark diversity.ResultsThe study showed a notable divergence in the predicted drivers of dark diversity depending on the method used. Nevertheless, we can conclude that plot‐level dark diversity was generally 17% higher in areas at low elevations and 31% higher in areas with a low species richness.ConclusionOur findings call for caution when interpreting statistical findings of dark‐diversity estimates. Even so, all analyses point toward an important role for natural processes such as competitive dominance as the main driver of the spatial patterns found in dark diversity in the northern Scandes.

Predicting the distribution of Ixodes ricinus and Dermacentor reticulatus in Europe: a comparison of climate niche modelling approaches

BackgroundThe ticks Ixodes ricinus and Dermacentor reticulatus are two of the most important vectors in Europe. Climate niche modelling has been used in many studies to attempt to explain their distribution and to predict changes under a range of climate change scenarios. The aim of this study was to assess the ability of different climate niche modelling approaches to explain the known distribution of I. ricinus and D. reticulatus in Europe.MethodsA series of climate niche models, using different combinations of input data, were constructed and assessed. Species occurrence records obtained from systematic literature searches and Global Biodiversity Information Facility data were thinned to different degrees to remove sampling spatial bias. Four sources of climate data were used: bioclimatic variables, WorldClim, TerraClimate and MODIS satellite-derived data. Eight different model training extents were examined and three modelling frameworks were used: maximum entropy, generalised additive models and random forest models. The results were validated through internal cross-validation, comparison with an external independent dataset and expert opinion.ResultsThe performance metrics and predictive ability of the different modelling approaches varied significantly within and between each species. Different combinations were better able to define the distribution of each of the two species. However, no single approach was considered fully able to capture the known distribution of the species. When considering the mean of the performance metrics of internal and external validation, 24 models for I. ricinus and 11 models for D. reticulatus of the 96 constructed were considered adequate according to the following criteria: area under the receiver-operating characteristic curve > 0.7; true skill statistic > 0.4; Miller’s calibration slope 0.25 above or below 1; Boyce index > 0.9; omission rate < 0.15.ConclusionsThis comprehensive analysis suggests that there is no single ‘best practice’ climate modelling approach to account for the distribution of these tick species. This has important implications for attempts to predict climate-mediated impacts on future tick distribution. It is suggested here that climate variables alone are not sufficient; habitat type, host availability and anthropogenic impacts, not included in current modelling approaches, could contribute to determining tick presence or absence at the local or regional scale.Graphical abstract

Cryptic invasion suggested by a cytogeographic analysis of the halophytic Puccinellia distans complex (Poaceae) in Central Europe.

Despite the wealth of studies dealing with the invasions of alien plants, invasions of alien genotypes of native species (cryptic invasions) have been vastly neglected. The impact of cryptic invasions on the biodiversity of plant communities can, however, be significant. Inland saline habitats and halophytes (i.e., salt-tolerant plant species) are especially threatened by this phenomenon as they inhabit fragmented remnants of largely destroyed habitats, but at the same time some of these halophytic species are rapidly spreading along salt-treated roads. To study potential cryptic invasion of halophytes, the patterns of genome size and ploidy variation in the Puccinellia distans complex (Poaceae), the most rapidly spreading roadside halophyte in Central Europe, were investigated. DNA flow cytometry with confirmatory chromosome counts were employed to assess ploidy levels of 1414 individuals from 133 populations of the P. distans complex. In addition, climatic niche modelling was used to predict the distributions of selected cytotypes. Eight groups differing in ploidy level and/or genome size were discovered, one diploid (2x; 2n = 14), two tetraploid (4xA, 4xB; 2n = 28), one pentaploid (5x; 2n = 35), three hexaploid (6xA, 6xB, 6xC; 2n = 42), and one heptaploid (7x; 2n = 49). The hexaploids (mostly the 6xC cytotype) were widespread through the study area, spreading intensively in both anthropogenic and natural habitats and probably hybridizing with the natural habitat dwelling tetraploids. In contrast, the non-hexaploid cytotypes rarely spread and were predominantly confined to natural habitats. The extensive spread of the hexaploid cytotypes along roadsides has most likely facilitated their incursion into natural habitats. The colonization of new natural habitats by the hexaploids may pose a threat to the indigenous Puccinellia populations by compromising their genetic integrity and/or by outcompeting them.

Global distribution modelling of a conspicuous Gondwanian soil protist reveals latitudinal dispersal limitation and range contraction in response to climate warming

AbstractAimThe diversity and distribution of soil microorganisms and their potential for long‐distance dispersal (LDD) are poorly documented, making the threats posed by climate change difficult to assess. If microorganisms do not disperse globally, regional endemism may develop and extinction may occur due to environmental changes. Here, we addressed this question using the testate amoeba Apodera vas, a morphologically conspicuous model soil microorganism in microbial biogeography, commonly found in peatlands and forests mainly of former Gondwana. We first documented its distribution. We next assessed whether its distribution could be explained by dispersal (i.e. matching its climatic niche) or vicariance (i.e. palaeogeography), based on the magnitude of potential range expansions or contractions in response to past and on‐going climatic changes. Last, we wanted to assess the likelihood of cryptic diversity and its potential threat from climate and land‐use changes (e.g. due to limited LDD).LocationDocumented records: Southern Hemisphere and intertropical zone; modelling: Global.MethodsWe first built an updated global distribution map of A. vas using 401 validated georeferenced records. We next used these data to develop a climatic niche model to predict its past (LGM, i.e. 21 ± 3 ka BP; PMIP3 IPSL‐CM5A‐LR), present and future (IPSL‐CMP6A‐LR predictions for 2071–2100, SSP3 and 5) potential distributions in responses to climate, by relating the species occurrences to climatic and topographic predictors. We then used these predictions to test our hypotheses (dispersal/vicariance, cryptic diversity, future threat from LDD limitation).ResultsOur models show that favourable climatic conditions for A. vas currently exist in the British Isles, an especially well‐studied region for testate amoebae where this species has never been found. This demonstrates a lack of interhemispheric LDD, congruent with the palaeogeography (vicariance) hypothesis. Longitudinal LDD is, however, confirmed by the presence of A. vas in isolated and geologically young peri‐Antarctic islands. Potential distribution maps for past, current and future climates show favourable climatic conditions existing on parts of all southern continents, with shifts to higher land from LGM to current in the tropics and a strong range contraction from current to future (global warming IPSL‐CM6A‐LR scenario for 2071–2100, SSP3.70 and SSP5.85) with favourable conditions developing on the Antarctic Peninsula.Main ConclusionsThis study illustrates the value of climate niche models for research on microbial diversity and biogeography, along with exploring the role played by historical factors and dispersal limitation in shaping microbial biogeography. We assess the discrepancy between latitudinal and longitudinal LDD for A. vas, which is possibly due to contrast in wind patterns and/or likelihood of transport by birds. Our models also suggest that climate change may lead to regional extinction of terrestrial microscopic organisms, thus illustrating the pertinence of including microorganisms in biodiversity conservation research and actions.

Climate Niche Modeling Reveals the Fate of Pioneering Late Pleistocene Populations in Northern Europe

Climate Niche Modeling Reveals the Fate of Pioneering Late Pleistocene Populations in Northern Europe

Artificial paradises: Man-made sites for the conservation of amphibians in a changing climate

Mediterranean wetlands harbour a rich freshwater biodiversity but also rank among the most-climate and human-pressure sensitive habitats. Amphibians are a taxonomic group strongly dependent on wetlands and the most threatened class of vertebrates due to habitat loss and alteration. In the Mediterranean region, amphibians breed in a large variety of artificial water sites (AWS). We used a large dataset of amphibian breeding sites to model functional connectivity, graph theory and climate niche modelling. AWS are radically different in structure compared to natural ones (NWS). Thus, we have disclosed how AWS can serve as a key piece of the ecological connectivity for amphibian populations; AWS and NWS have comparable values at the landscape scale, but in some areas AWS are pivotal. Furthermore, many AWS contribute by buffering the effect of climate change in the near future. We emphasize that conservation management strategies would be strengthened by including a specific focus on human-made aquatic habitats.

Applying the concept of niche breadth to understand urban tree mortality in the UK

Accelerated climate change has raised concerns about heightened vulnerability of urban trees, spurring the need to reevaluate their suitability. The urgency has also driven the widespread application of climatic niche-based models. In particular, the concept of niche breadth (NB), the range of environmental conditions that species can tolerate, is commonly estimated based on species occurrence data over the selected geographic range to predict species response to changing conditions. However, in urban environments where many species are cultivated out of the NB of their natural distributions, additional empirical evidence beyond presence and absence is needed not only to test the true tolerance limits but also to evaluate species' adaptive capacity to future climate. In this research, mortality trends of Acer and Quercus species spanning a 21-year period (2000–2021) from tree inventories of three major UK botanic gardens - the Royal Botanic Gardens, Kew (KEW), Westonbirt, the National Arboretum (WESB), and the Royal Botanic Garden Edinburgh (RBGE) - were analyzed in relation to their NB under long-term drought stress. As a result, Acer species were more responsive to drought and heat stress. For Acer, positioning below the lower limits of the precipitation of warmest quarter led to an increase in the probability of annual mortality by 1.2 and 1.3 % at KEW and RBGE respectively. In addition, the mean cumulative mortality rate increased corresponding to an increase in the number of niche positions below the lower limits of the selected bioclimatic variables. On the other hand, Quercus species in general exhibited comparable resilience regardless of their niche positions. Moreover, Mediterranean oaks were most tolerant, with cumulative mortality rates that were lower than those of native oaks in the UK. These findings further highlight the importance of incorporating ecological performance and recognizing species-specific adaptive strategies in climatic niche modeling.

Projected distribution of the westernmost subpopulation of Assamese macaques (Macaca assamensis pelops) under climate change: conservation implications of a threatened population

Anthropogenic climate change can have a negative impact on the distribution of habitat specialist species with narrow distributional ranges. Among the many areas around the world affected by climate change, the Himalayan region in particular is experiencing marked effects of global warming on its climatic patterns and life forms. This study assessed the current distribution of Assamese macaques (Macaca assamensis) in western Nepal, and projected their likely distribution (via habitat suitability modeling) for the years 2050 and 2070 under the two most plausible greenhouse gas emission scenarios (RCP4.5 and RCP6.0). We recorded a total of 159 Assamese macaques belonging to 10 groups (nine of them residing outside of protected area networks) between 684m and 2550m asl in western Nepal. Climatic niche modeling predicted that 37.03% (25,114 km2) of the total area of western Nepal (67,813 km2) represented suitable habitat of the species, the majority of which ranged between 1000 m and 2000 m asl. Future projections of the current climatic niche of the Assamese macaques revealed a consistent decrease in the suitable habitat for 2050 and 2070 in both of the greenhouse emission scenarios tested. With the RCP6.0 scenario, almost 57% of the current highly suitable habitat would be lost by 2070 with remaining suitable habitat shifted towards higher elevations. The loss of habitat directly affects the species survival and the range shift towards higher elevation exposes them to new areas for conflict with humans. Therefore, the Assamese macaque population in western Nepal requires a high conservation priority with the establishment of new protected areas.

Predictions based on phylogeography and climatic niche modelling depict an uncertain future scenario for giant blister beetles (Berberomeloe, Meloidae) facing intensive greenhouse expansion and global warming

Abstract Large‐scale agricultural and tourism development are the main threats to biodiversity in south‐eastern Spain. Species with low dispersal abilities, such as some endemic insects from this region, are particularly vulnerable to fragmentation and loss of genetic and morphological diversity. Here, we studied the current and future threat of climate and land‐use change on the intraspecific diversity of one such group of endemics, the giant blister beetles of the Berberomeloe insignis species group. Using a phylogeographic approach and morphometrics, we identified intraspecific variation within the B. insignis species group. These data were coupled with ecological niche modelling (ENM) to determine the effect of agricultural and climate change on the connectivity across phylogroups. We identified a marked geographic structure within B. insignis, with the time to the most recent common ancestor (TMRCA) of the two main mtDNA clades dating back to 2.1 Ma. Cyto‐nuclear discordances found across parapatric populations suggest past events of genetic introgression. B. insignis presents a head pattern that is geographically structured and mostly congruent with the four mitochondrial lineages. In contrast, diversification within Berberomeloe tenebrosus is more recent, dating back to less than 1 Ma. Future ENMs highlight the role of mountains as potential refugia under a climate warming scenario but predict extinctions in the lowlands. Based on our analyses, two lineages of B. insignis are threatened and should be urgently considered as independent conservation units, and their current geographic distribution areas protected to conserve, at the very least, a portion of the species' evolutionary heritage.

Predicting potential range shifts using climatic time series and niche models: A Neotropical montane shrew's case

Ecological niche models (ENMs) can forecast species' potential range shifts by transferring a model to a future climatic scenario. However, this approximation does not identify whether range shifts have occurred in species' distributional limits in the last several decades. Given ongoing anthropogenic climate change, changes in distributional limits are expected to occur (poleward and upslope for several montane species). Here, I use a climatic time series to predict potential changes in distributional limits in response to climate change over the last four decades, using the Mexican small-eared shrew (Cryptotis mexicanus), a montane cloud-forest species, as an example. I transferred the ENM (tuned to optimize complexity) to a series of thirty-year bioclimatic periods between 1979 and 2019 created with monthly precipitation and temperature data. I detected trends in suitability and bioclimatic variables using a Mann-Kendall test and identified which variables could be driving the suitability changes in distributional limits. The detected extent and direction of suitability trends do not suggest the uniform pole-ward or upslope shifts expected under warming conditions. Comparisons between suitability and variable trends suggest that precipitation, not temperature, plays a stronger role in explaining changes in climatic suitability for C. mexicanus. Where precipitation decreased, there was suitability loss, while in areas where precipitation increased, suitability gain was observed. These analyses illustrate how incorporating time-series climatic data into ENMs can aid in understanding if species are already responding to changes in climate. Here, the potential response of C. mexicanus to climate change varies across its distribution and therefore the species' range shifts may not necessarily follow expected general patterns. These findings should be verified with field data. More generally, using the valuable climatic information of the last several decades should be incorporated into studies that determine potential range shifts under recent or future climatic conditions.

High-mountain phylogeography in the Balkan Peninsula: isolation pattern in a species of alpine siliceous grasslands and its possible background

Although the Balkan Peninsula belongs to the most mountainous regions of Europe, phylogeographic structure of its alpine flora remains insufficiently understood, especially for species distributed both in the western and eastern parts of the Peninsula. We analyzed Campanula orbelica, a Balkan endemic typical of high-mountain siliceous grasslands, based on the population genetic structure, climatic niche modeling at the species- and intraspecific level, and niche hindcasting back to the Last Glacial Maximum (LGM; 20 kya). Our data reveal a clear phylogeographic pattern with three geographically coherent genetic groups: (i) the most divergent and spatially restricted lineage of the Pirin mountains (east), (ii) neighboring Rila mountains and other eastern Balkan massifs (Rhodopes, Stara Planina, Vitoša), and (iii) the most geographically disjunct mountains of the Scardo-Pindhic range (Šar Planina and Korab) in the west. This pattern indicates multiple refugia and isolated evolutionary centers within the Balkan Peninsula mountains, with the eastern part of the range as likely ancestral area, and an early dispersion into the western region, which formed the main geographical disjunction. The genetic divergence was only partly correlated with geographical isolation, clear dispersal barriers, or climatic niche shifts, suggesting contrasting isolation/dispersal dynamics in various parts of the range. Climatic niche overlap was low among eastern vs. western groups, which correlates with the longest spatial distance and significant genetic divergence, while niche characteristic of the Pirin lineage was a subset of the adjacent Rila lineage niche. High genetic divergence of the Pirin populations was also not correlated with persistent gaps in potential distributions but hypothetically may have been triggered by diversified (limestone/silicate) bedrock conditions. Our results highlight the need for high-mountain phylogeographic surveys in the eastern part of the Balkan Peninsula, to assess the biogeographical relevance of isolation patterns and definition of evolutionarily important units in the high-mountain flora.

Niche conservatism and strong phylogenetic signals in climate, soil, and morphological variation of Neotropical firs (Abies, Pinaceae)

AbstractInterspecific trait divergence may reflect adaptation and reproductive isolation, particularly after the rapid differentiation that may follow the colonization of new environments. Although new lineages are generally expected to be morphologically and ecologically similar to their ancestors, environmental forces can also drive adaptive differentiation along specific phenotypic axes. We used climate niche models and comparative analyses based on a previously inferred phylogeny to examine the history of ecological and morphological divergence of Neotropical firs (Abies Mill., Pinaceae), a group of conifers that have recently colonized and diversified in the mountains of Mexico and northern Central America. We inferred past secondary contact zones by comparing current and past climate niche projections and looked for evidence of recent interspecific gene flow using genomic data. Neotropical firs have similar niches to each other and show a strong phylogenetic signal for most evaluated morphological traits. Analyses based on individual variables suggested a random walk model of differentiation. However, early adaptation to tropical conditions is inferred in the ancestor of the southernmost firs, as all modern southern taxa are differentiated climatically from Abies concolor, the northernmost species. In addition, observed autapomorphic traits for soil properties and the number of resin ducts in needles are consistent with possible species‐specific adaptations. Thus, a combination of nonadaptive and adaptive processes along different phenotypic axes, some related to the environment, likely operated after the southward migration of this plant lineage from North America and its subsequent radiation in the Neotropics.

Climatic niche convergence through space and time for a potential archaeophyte (Acacia caven) in South America

Based on the niche conservatism hypothesis, i.e. the idea that niches remain unchanged over space and time, climatic niche modelling (CNM) is a useful tool for predicting the spread of introduced taxa. Recent advances have extended such predictions deeper in time for plant species dispersed by humans before the modern era. The latest CNMs successfully evaluate niche differentiation and estimate potential source areas for intriguing taxa such as archaeophytes (i.e., species introduced before 1492 AD). Here, we performed CNMs for Acacia caven, a common Fabaceae tree in South America, considered an archaeophyte west of the Andes, in Central Chile. Accounting for the infraspecific delimitation of the species, our results showed that even when climates are different, climatic spaces used by the species overlap largely between the eastern and western ranges. Despite slight variation, results were consistent when considering one, two, or even three-environmental dimensions, and in accordance with the niche conservatism hypothesis. Specific distribution models calibrated for each region (east vs west) and projected to the past, indicate a common area of occupancy available in southern Bolivia—northwest Argentina since the late Pleistocene, which could have acted as a source-area, and this signal becomes stronger through the Holocene. Then, in accordance with a taxon introduced in the past, and comparing regional vs continental distribution models calibrated at the infraspecific or species level, the western populations showed their spread status to be mostly in equilibrium with the environment. Our study thus indicates how niche and species distribution models are useful to improve our knowledge related to taxa introduced before the modern era.