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Goedecke F.; Bergmeier, E. (2018): Ecology and potential distribution of the Cretan endemic tree species Zelkova abelicea. Journal of Mediterranean Ecology. accepted
Abstract
Mediterranean mountain forests feature woody species relics such as Zelkova abelicea, an endemic tree species confined to six spatially and genetically distinct populations in Crete (S Aegean, Greece). We used species distribution modelling to predict the potential distribution of Zelkova abelicea. Comparison of coordinate-based geodata extractions for climate and topography revealed pronounced environmental differences for the metapopulations. Main factors for species distribution models were altitude and temperature seasonality (proxy for west-east gradient) whereas topographic conditions had surprisingly little influence on our models. While the most extensive Zelkova metapopulations were found to occur under locally fairly mesic conditions and comprising a wider ecological spectrum, the smaller populations comprising narrower ecological range occurred at lower elevations and further east. For further extrapolation with similar models for known populations, only similar site conditions allowed for a prediction. Differentiated site conditions in the mountains, genetic distinctness and possible environmental adaptations of isolated populations are to be considered in conservation and management.
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Zelkova sicula (Ulmaceae) is currently known from only two localized natural subpopulations, each occupying a very small area (about 0.18 and 0.50 hectares, respectively) (Garfì et al. 2011). Both the extent of occurrence
(EOO) and the area of occupancy (AOO), estimated using a 2x2 km grid, are very much less than 8 km2,
and there is a continuing decline in the quality of habitat as a result of a range of threats, including
grazing, fire, and climate change. No successful pollination has been observed so far in the few
flowering plants (Garfì 1997, Garfì and Buord 2012), which fluctuate from year to year from about 20 to
70 in total for the two subpopulations. All the examined seeds proved to be sterile, and the species only
reproduces through root suckers, whilst re-sprouting allows prompt recovery from damage caused by
disturbance and drought stress (Garfì et al. 2002). Unable to perform sexual reproduction and due to its
extreme genetic impoverishment, the number of individuals are potentially subject to decline owing to
diseases and/or global warming (Gratzfeld et al. 2015), the latter also affecting the habitat. Though the
recent finding (2009) of a second subpopulation (Garfì et al. 2011) increased the number of known
plants, the probability of extinction remains very high. The species is assessed as Critically Endangered
B1ab(iii)+2ab(iii).
High-resolution information on climatic conditions is essential to many applications in environmental and ecological sciences. Here we present the CHELSA (Climatologies at high resolution for the earth's land surface areas) data of downscaled model output temperature and precipitation estimates of the ERA-Interim climatic reanalysis to a high resolution of 30 arc sec. The temperature algorithm is based on statistical downscaling of atmospheric temperatures. The precipitation algorithm incorporates orographic predictors including wind fields, valley exposition, and boundary layer height, with a subsequent bias correction. The resulting data consist of a monthly temperature and precipitation climatology for the years 1979–2013. We compare the data derived from the CHELSA algorithm with other standard gridded products and station data from the Global Historical Climate Network. We compare the performance of the new climatologies in species distribution modelling and show that we can increase the accuracy of species range predictions. We further show that CHELSA climatological data has a similar accuracy as other products for temperature, but that its predictions of precipitation patterns are better. Design Type(s) data integration objective • modeling and simulation objective Measurement Type(s) temperature of air • hydrological precipitation process Technology Type(s) data acquisition system Factor Type(s) Sample Characteristic(s) Earth • planetary atmosphere
Environmental niche modeling (ENM) is commonly used to develop probabilistic maps of species distribution. Among available ENM techniques, MaxEnt has become one of the most popular tools for modeling species distribution, with hundreds of peer-reviewed articles published each year. MaxEnt’s popularity is mainly due to the use of a graphical interface and automatic parameter configuration capabilities. However, recent studies have shown that using the default automatic configuration may not be always appropriate because it can produce non-optimal models; particularly when dealing with a small number of species presence points. Thus, the recommendation is to evaluate the best potential combination of parameters (feature classes and regularization multiplier) to select the most appropriate model. In this work we reviewed 244 articles published between 2013 and 2015 to assess whether researchers are following recommendations to avoid using the default parameter configuration when dealing with small sample sizes, or if they are using MaxEnt as a “black box tool.” Our results show that in only 16% of analyzed articles authors evaluated best feature classes, in 6.9% evaluated best regularization multipliers, and in a meager 3.7% evaluated simultaneously both parameters before producing the definitive distribution model. We analyzed 20 articles to quantify the potential differences in resulting outputs when using software default parameters instead of the alternative best model. Results from our analysis reveal important differences between the use of default parameters and the best model approach, especially in the total area identified as suitable for the assessed species and the specific areas that are identified as suitable by both modelling approaches. These results are worrying, because publications are potentially reporting over-complex or over-simplistic models that can undermine the applicability of their results. Of particular importance are studies used to inform policy making. Therefore, researchers, practitioners, reviewers and editors need to be very judicious when dealing with MaxEnt, particularly when the modelling process is based on small sample sizes.
Yellowwood (Cladrastis kentukea) grows in small, widely scattered populations in the wild, but is also a popular ornamental tree that thrives when planted in urban areas outside its natural range. Since the small native populations of yellowwood in several states are considered at risk of extirpation, the cultivated population could serve as an ex situ repository of yellowwood genetic diversity that could be used to restore lost local populations of the species. The potential value of cultivated yellowwood for conservation depends on the genetic diversity among cultivated trees compared to natural populations. Using nuclear microsatellite markers, we genotyped 180 yellowwoods from natural populations in Indiana, Missouri, Arkansas, and Kentucky, along with 61 trees from urban parks and landscapes in Indiana, Ohio, and Missouri. We found that, even when statistics were adjusted based on population size, the urban “population” had higher genetic diversity than any of the wild populations sampled, indicating that commercially-grown yellowwood is most likely a mixture of genotypes from isolated wild populations. We observed strong genetic differentiation among wild populations, and evidence for inbreeding in at least one of the wild populations.
Aim
Higher‐elevation areas on islands and continental mountains tend to be separated by longer distances, predicting higher endemism at higher elevations; our study is the first to test the generality of the predicted pattern. We also compare it empirically with contrasting expectations from hypotheses invoking higher speciation with area, temperature and species richness.
Location
Thirty‐two insular and 18 continental elevational gradients from around the world.
Methods
We compiled entire floras with elevation‐specific occurrence information, and calculated the proportion of native species that are endemic (‘percent endemism’) in 100‐m bands, for each of the 50 elevational gradients. Using generalized linear models, we tested the relationships between percent endemism and elevation, isolation, temperature, area and species richness.
Results
Percent endemism consistently increased monotonically with elevation, globally. This was independent of richness–elevation relationships, which had varying shapes but decreased with elevation at high elevations. The endemism–elevation relationships were consistent with isolation‐related predictions, but inconsistent with hypotheses related to area, richness and temperature.
Main conclusions
Higher per‐species speciation rates caused by increasing isolation with elevation are the most plausible and parsimonious explanation for the globally consistent pattern of higher endemism at higher elevations that we identify. We suggest that topography‐driven isolation increases speciation rates in mountainous areas, across all elevations and increasingly towards the equator. If so, it represents a mechanism that may contribute to generating latitudinal diversity gradients in a way that is consistent with both present‐day and palaeontological evidence.
The area under the receiver operating characteristic (ROC) curve, known as the AUC, is currently considered to be the standard method to assess the accuracy of predictive distribution models. It avoids the supposed subjectivity in the threshold selection process, when continuous probability derived scores are converted to a binary presence–absence variable, by summarizing overall model performance over all possible thresholds. In this manuscript we review some of the features of this measure and bring into question its reliability as a comparative measure of accuracy between model results. We do not recommend using AUC for five reasons: (1) it ignores the predicted probability values and the goodness-of-fit of the model; (2) it summarises the test performance over regions of the ROC space in which one would rarely operate; (3) it weights omission and commission errors equally; (4) it does not give information about the spatial distribution of model errors; and, most importantly, (5) the total extent to which models are carried out highly influences the rate of well-predicted absences and the AUC scores.
Genetic diversity at nine isozyme loci was surveyed in an endangered tree species, the argan tree, endemic to south-western Morocco. The species is highly diverse (3.6 alleles/locus) with populations strongly differentiated from each other (F ST=0.25). This example is used to illustrate a method for standardizing measures of allelic richness in samples of unequal sample sizes, which was developed for the estimation of the number of species and relies on the technique of rarefaction. In addition, it is shown that the measure of subdivision, θ ST, obtained when allelic richness is used in place ofh (Nei's index of diversity), is much larger than the F ST [e.g. θ ST(40)=0.52, where (40) indicates the specified sample used to estimate the allelic richness]. This suggests that rare alleles (which strongly influence measures of allelic richness) have a more scattered distribution than more frequent ones, a result which raises special conservation issues for the argan tree.
Hydraulic failure can cause massive die-back of forest trees during drought. With extreme climatic events set to become more frequent and severe due to climatic change, it is essential to study resistance to water stress-induced cavitation. We investigated the genetic differentiation for cavitation resistance among Pinus hartwegii populations, the pine species growing at the treeline in México. Open-pollinated seeds were collected from seven natural populations along an altitudinal gradient (3,150–3,650 masl) from Pico de Tancítaro, Michoacán, western México. Seedlings were raised in a nursery and then established in a randomized complete block design in a common garden experiment. Resistance to cavitation (P
50, xylem pressure inducing 50 % loss of hydraulic conductance and S, slope of the vulnerability curve) and specific hydraulic conductivity (k
s), were evaluated on branches of 5-year-old seedlings using the Cavitron technique. Mean P
50 was −3.42 ± 0.05 MPa, indicating that Pinus hartwegii is one of the more vulnerable pine species to cavitation. No significant genetic differentiation was detected between populations for cavitation resistance traits (P
50 and S), but a significant altitudinal cline was found for S. In contrast, k
s exhibited a significant differentiation among populations and a significant decline with increasing altitude. The lack of genetic differentiation among P. hartwegii populations for cavitation resistance is likely to represent a limitation for adapting to the warmer and drier climates that are expected to occur in México under climatic change. Finally, a worldwide comparison within the Pinus genus showed that pines growing at the treeline were on average more vulnerable to cavitation than those from lowland. This might reflect an adaptation to dry environmental conditions at low elevation.
Conservation policies usually focus on in situ protection of native populations, a priority that requires accurate assessment of population status. Distinction between native and introduced status can be particularly difficult (and at the same time, is most important) for species whose natural habitat has become both rare and highly fragmented. Here, we address the status of the white elm (Ulmus laevis Pallas), a European riparian tree species whose populations have been fragmented by human activity and is protected wherever it is considered native. Small populations of this species are located in Iberia, where they are unprotected because they are considered introductions due to their rarity. However, Iberia and neighbouring regions in southwestern France have been shown to support discrete glacial refuge populations of many European trees, and the possibility remains that Iberian white elms are native relicts. We used chloroplast RFLPs and nuclear microsatellites to establish the relationship between populations in Iberia and the Central European core distribution. Bayesian approaches revealed significant spatial structure across populations. Those in Iberia and southwestern France shared alleles absent from Central Europe, and showed spatial population structure within Iberia common in recognized native taxa. Iberian populations show a demographic signature of ancient population bottlenecks, while those in Central European show a signature of recent population bottlenecks. These patterns are not consistent with historical introduction of white elm to Iberia, and instead strongly support native status, arguing for immediate implementation of conservation measures for white elm populations in Spain and contiguous areas of southern France.Heredity advance online publication, 11 September 2013; doi:10.1038/hdy.2013.81.
This study is based on the hypothesis that catenary soil development occurs in many landscapes in response to the way water moves through and over the landscape. Significant correlations between quantified terrain attributes and measured soil attributes were found on a 5.4-ha toposequence in Colorado. Slope and wetness index were the terrain attributes most highly correlated with surface soil attributes measured at 231 locations. The computed and measured ranges of terrain and soil attributes, respectively, can be used to enhance an existing soil map, even when the exact form of the relationship is unknown. As a first approximation, interpolated predictions of A horizon thickness and pH compared reasonably well with the observed. Such techniques may also be applied in unmapped areas to guide soil sampling and model development. -from Authors
The altitudinal pattern of genetic variation in Pinus hartwegii Lindl. populations was explored for seedling height growth, frost damage, grass-stage, and phenological stage of the terminal shoot. A provenance test was conducted with open-pollinated seed from 13 populations collected along an altitudinal transect (3000–3600m) at the National Park Pico de Tancítaro, Michoacán, center-west Mexico. Height growth of seedlings in a nursery was assessed at seven and 18 months of age. Frost damage at −15°C was evaluated in laboratory at 18 months of age; proportion of plants that had left grass-stage and stage of shoot development was assessed at the age of 22 months. Significant differences among provenances (P
Understanding diversity patterns along environmental gradients and their underlying mechanisms is a major topic in current biodiversity research. In this study, we investigate for the first time elevational patterns of vascular plant species richness and endemism on a long-isolated continental island (Crete) that has experienced extensive post-isolation mountain uplift. We used all available data on distribution and elevational ranges of the Cretan plants to interpolate their presence between minimum and maximum elevations in 100-m elevational intervals, along the entire elevational gradient of Crete (0-2400 m). We evaluate the influence of elevation, area, mid-domain effect, elevational Rapoport effect and the post-isolation mountain uplift on plant species richness and endemism elevational patterns. Furthermore, we test the influence of the island condition and the post-isolation mountain uplift to the elevational range sizes of the Cretan plants, using the Peloponnese as a continental control area. Total species richness monotonically decreases with increasing elevation, while endemic species richness has a unimodal response to elevation showing a peak at mid-elevation intervals. Area alone explains a significant amount of variation in species richness along the elevational gradient. Mid-domain effect is not the underlying mechanism of the elevational gradient of plant species richness in Crete, and Rapoport's rule only partly explains the observed patterns. Our results are largely congruent with the post-isolation uplift of the Cretan mountains and their colonization mainly by the available lowland vascular plant species, as high-elevation specialists are almost lacking from the Cretan flora. The increase in the proportion of Cretan endemics with increasing elevation can only be regarded as a result of diversification processes towards Cretan mountains (especially mid-elevation areas), supported by elevation-driven ecological isolation. Cretan plants have experienced elevational range expansion compared to the continental control area, as a result of ecological release triggered by increased species impoverishment with increasing elevation.
Oncophorus dendrophilus is described from two upland forest localities in the Paphos District of Cyprus, and from the White Mountains of Crete. It is characterized by its bistratose upper leaves with bistratose streaks extending 3/4 of the way to the leaf base, 2–3 stratose margins and large spores. The new species may represent a relictual Tertiary element in the eastern Mediterranean flora, or it may be a recent derivative from the widespread Holarctic species O. wahlenbergii.
Summary 1. It is difficult to establish conservation priorities for cryptic species when their ecological requirements are confounded by problems with species identification. In some cases, such as Chiroptera, cryptic taxa may actually consist of both widespread, abundant species and localized, rare species. Discrimination between these species may be facilitated by phenotypic, species-specific traits such as echolocation calls. Echolocation studies supported by genetic data have revealed that one of the most abundant bat species in Europe actually consists of two cryptic species: Pipistrellus pipistrellus and P. pygmaeus . 2. We recorded echolocation calls from both species along road transects in Switzerland to study their distribution and abundance. Using Ecological Niche Factor Analysis and discriminant analysis, we characterized species-specific habitat requirements, built habitat suitability maps and examined interspecific differences in niche parameters. 3. The presence of P. pygmaeus was associated with landscape matrices comprising large rivers and lakes, human settlements and open woodland. P. pipistrellus utilized similar habitat matrices but was far more tolerant to deviations from its optimal habitat. P. pygmaeus occupied a much narrower ecological niche, encompassed mainly within that of its sister taxon. 4. Synthesis and applications. P. pipistrellus is ranked as 'not threatened' in Switzerland. The results from this study indicate an abundance approximately 30 times higher than that of P. pygmaeus . In contrast, P. pygmaeus is distributed patchily and occurs at comparatively low densities. We recommend reclassification of P. pygmaeus as 'rare and potentially threatened'. Conservation of P. pygmaeus should focus on the management of riparian woodland in areas with a high probability of occurrence. This study emphasizes the need to recognize the potential existence of cryptic taxa so that effective conservation management of rare species can be put into place before they are seriously endangered.
Prediction of species’ distributions is central to diverse applications in ecology, evolution and conservation science. There is increasing electronic access to vast sets of occurrence records in museums and herbaria, yet little effective guidance on how best to use this information in the context of numerous approaches for modelling distributions. To meet this need, we compared 16 modelling methods over 226 species from 6 regions of the world, creating the most comprehensive set of model comparisons to date. We used presence-only data to fit models, and independent presence-absence data to evaluate the predictions. Along with well-established modelling methods such as generalised additive models and GARP and BIOCLIM, we explored methods that either have been developed recently or have rarely been applied to modelling species’ distributions. These include machine-learning methods and community models, both of which have features that may make them particularly well suited to noisy or sparse information, as is typical of species’ occurrence data. Presence-only data were effective for modelling species’ distributions for many species and regions. The novel methods consistently outperformed more established methods. The results of our analysis are promising for the use of data from museums and herbaria, especially as methods suited to the noise inherent in such data improve.
Abies nebrodensis (Lojac.) Mattei (Sicilian fir) is an endangered species represented by only one population of 29 adult individuals occurring
in a limited area of the Madonie Range in northern Sicily (Italy). Taxonomic boundaries between this taxon and the neighboring
Abies species are not clear. In this study, we used six chloroplast simple-sequence repeats (cpSSRs) to investigate the population
genetic structure and the distribution of chloroplast haplotypic variation in A. nebrodensis and three of the neighboring Abies species: Abies alba (Mill.), Abies numidica (De Lann) and Abies cepha-lonica (Loud.). Our aims were to quantify the level of cpDNA differentiation within the Abies populations and to shed light on the history of A. nebrodensis. Diversity levels based on the haplotype frequency at six cpSSRs were high, especially in A. alba and A. cephalonica. In all, we found 122 haplotypes among the 169 individuals analyzed, and the four species were distinguished from each other
by their haplotype composition. The majority of the haplotypes (76%) were detected only once, but in A. nebrodensis seven individuals (41% of the sample population) shared the same haplotype. Moreover, the seven A. nebrodensis individuals with an identical haplotype showed a tendency to be geographically grouped within the population"s limited range.
The analysis of molecular variance (AMOVA) showed a significant difference in the level of apportionment of gene diversity
between the species A. alba and A. cephalonica (FST=0.191 and 0.012, respectively). AMOVA analysis conducted over all populations from the four species showed that 19% of the
total cpSSR variation was attributable to differences among species, 6% was due to differences among populations within species,
and 74% to differences within populations. The high percentage of unique haplotypes identified confirms the power of cpSSR
haplotype analysis for identifying individual trees in individual Abies populations. Our results indicate that A.nebrodensis differs from the other three Abies species investigated and support its classification as an independent taxon. The results also showed a decreased level of
variation in A. nebrodensis and suggested that the species has experienced a genetic bottleneck during the last two centuries.
Deciduous and evergreen species are segregated on northeast and southwest slopes of the southern Appalachian Mountains. The segregated distributions of three ericaceous shrubs (Rhododendron maximum valley positions; Rhododendron periclymenoides on northeast slopes; Kalmia latifolia on southwest slopes) were compared to the respective irradiance environments. Growth patterns of field plants, and photosynthetic acclimation of each species to three irradiance treatments in a phytotron were studied. Rhododendron maximum, an evergreen species, was found to be most sensitive to high radiation. In phytotron experiments, quantum yield, light saturated photosynthetic capacity, photosynthesis per chlorophyll, and water use efficiency decreased at high ambient irradiance for R. maximum. These characteristics limit the growth of R. maximum on high irradiance southwestern slopes. Both K. latifolia and R. periclymenoides were able to improve their photosynthetic performance at high ambient irradiance. Rhododendron periclymenoides, a deciduous species, was found to continue increasing leaf conductance at high irradiance without an increase in photosynthesis indicating a possible limitation by water in high light environments such as southwest slopes. Kalmia latifolia, an evergreen species, had reduced photosynthetic capacity and reduced water use efficiency when grown in low irradiance conditions which coincides with the higher K. latifolia abundance on high light, southwestern slopes.
This book provides an up-to-date, comprehensive treatment of the variables and processes of microclimate and local climate, including radiation balance and energy balance. It describes and explains the climate within the lower atmosphere and upper soil, the region critical to life on Earth. Topics that are covered include not only the physical processes that affect microclimate, but also biological processes that affect vegetation and animals, including people. A geographic tour of the microclimates of the major ecosystems around the world is included. All major biomes and surface types are examined, including urban areas, and the effects of climate change on microclimate are described. This book is invaluable for advanced students and researchers in climatology in departments of environmental science, geography, meteorology, agricultural science and forestry.
Accurately predicting biological impacts of climate change is necessary to guide policy. However, the resolution of climate data could be affecting the accuracy of climate change impact assessments. Here we review the spatial and temporal resolution of climate data used in impact assessments and demonstrate that these resolutions are often too coarse relative to biologically relevant scales. We then develop a framework that partitions climate into three important components: trend, variance, and autocorrelation. We apply this framework to map different global climate regimes and identify where coarse climate data is most and least likely to reduce the accuracy of impact assessments. We show that impact assessments for many large mammals and birds use climate data with a spatial resolution similar to the biologically relevant area encompassing population dynamics. Conversely, impact assessments for many small mammals, herpetofauna, and plants use climate data with a spatial resolution that is orders of magnitude larger than the area encompassing population dynamics. Most impact assessments also use climate data with a coarse temporal resolution. We suggest that climate data with a coarse spatial resolution likely reduces the accuracy of impact assessments the most in climates with high spatial trend and variance (e.g., much of western North and South America) and the least in climates with low spatial trend and variance (e.g., the Great Plains of the USA). Climate data with a coarse temporal resolution likely reduces the accuracy of impact assessments the most in the northern half of the northern hemisphere where temporal climatic variance is high. Our framework provides one way to identify where improving the resolution of climate data will have the largest impact on the accuracy of biological predictions under climate change. This article is protected by copyright. All rights reserved.
Estimation of potential annual direct incident radiation has traditionally required numerical integration with simulation models. As an alternative, we present convenient equations for use in spreadsheet, GIS, and database applications. Input variables are latitude, slope, and aspect. The equations apply to 0-60degrees north latitude, slopes from 0-90degrees, and all aspects. By transforming aspect, the equations can also be applied as an index of heat load, symmetrical about a northeast to southwest axis.
While average temperature is likely to increase in most locations on Earth, many places will simultaneously experience higher variability in temperature, precipitation, and other climate variables. Although ecologists and evolutionary biologists widely recognize the potential impacts of changes in average climatic conditions, relatively little attention has been paid to the potential impacts of changes in climatic variability and extremes. We review the evidence on the impacts of increased climatic variability and extremes on physiological, ecological and evolutionary processes at multiple levels of biological organization, from individuals to populations and communities. Our review indicates that climatic variability can have profound influences on biological processes at multiple scales of organization. Responses to increased climatic variability and extremes are likely to be complex and cannot always be generalized, although our conceptual and methodological toolboxes allow us to make informed predictions about the likely consequences of such climatic changes. We conclude that climatic variability represents an important component of climate that deserves further attention.
© 2015 Cambridge Philosophical Society.
The MaxEnt software package is one of the most popular tools for species distribution and environmental niche modeling, with over 1000 published applications since 2006. Its popularity is likely for two reasons: 1) MaxEnt typically outperforms other methods based on predictive accuracy and 2) the software is particularly easy to use. MaxEnt users must make a number of decisions about how they should select their input data and choose from a wide variety of settings in the software package to build models from these data. The underlying basis for making these decisions is unclear in many studies, and default settings are apparently chosen, even though alternative settings are often more appropriate. In this paper, we provide a detailed explanation of how MaxEnt works and a prospectus on modeling options to enable users to make informed decisions when preparing data, choosing settings and interpreting output. We explain how the choice of background samples reflects prior assumptions, how nonlinear functions of environmental variables (features) are created and selected, how to account for environmentally biased sampling, the interpretation of the various types of model output and the challenges for model evaluation. We demonstrate MaxEnt’s calculations using both simplified simulated data and occurrence data from South Africa on species of the flowering plant family Proteaceae. Throughout, we show how MaxEnt’s outputs vary in response to different settings to highlight the need for making biologically motivated modeling decisions.
This is the first comprehensive book on the weather and climate of mountains. The first chapter on the historical aspects is followed by chapters dealing with the geographical controls of mountain meteorological elements, circulation systems related to orography and the climatic characteristics of mountains. Chapter 5 looks at case studies and Chapter 6 bioclimatology. The final chapter examines the evidence for and the significance of changes in mountain climates.-D.G.Tout
Aim To elucidate the phylogeographical patterns in three Cenozoic relict species: Zelkova sicula, Z. abelicea and Z. carpinifolia (Ulmaceae). Location Sicily, Crete and Transcaucasia. Methods Two chloroplast loci (trnH–psbA and trnL) and the nuclear ribo-somal markers ITS1 and ITS2 were sequenced for 154 samples collected from 14 populations of Z. abelicea, 16 populations of Z. carpinifolia, and the two known populations of Z. sicula. We obtained georeferenced data, calculated median joining networks and carried out diversity analyses. A few ex situ samples collected from botanical gardens, of the East Asian species Zelkova serrata, Z. schneideriana and Z. sinica, were also analysed for comparative purposes. Results High levels of variability were found in the chloroplast markers within Z. carpinifolia (15 haplotypes) and Z. abelicea (33 haplotypes), in association with strong phylogeographical structure. Conversely, Z. sicula was characterized by low diversity, with each population exhibiting a single haplotype. Lower variability was found for ITS1 and ITS2 within Z. carpinifolia and Z. abelicea (13 and 7 ribotypes per species, respectively), with Z. carpinifolia showing a high proportion of populations with no intragenomic polymorphism. In the triploid and clonal Z. sicula, all individuals displayed intragenomic polymor-phism and seven ribotypes were identified. Main conclusions The chloroplast diversity of Z. abelicea and Z. carpinifolia suggests a very ancient history of diversification and structuring, with footprints of past expansions and more recent bottlenecks. Zelkova sicula has had a history of severe isolation and is likely to be of hybrid origin.
This new taxon was discovered in 2 neighbouring dolines of the Psiloritis mountain range in C Kriti, at an altitude of c1500 m. -from Authors
On spur ridges on Brush Mountain, SW Virginia, Rhododendron maximum was found only in valleys and lower NE slopes, Rhododendron periclymenoides was found on NE slopes while Kalmia latifolia was most abundant on SW slopes. These partially segregated distributions were related to irradiance and water availability. R. periclymenoides had the lowest diurnal leaf water potentials and the largest seasonal variation in midday leaf water potential. K. latifolia had the highest leaf conductance. R. maximum had the greatest seasonal osmotic adjustment followed by R. periclymenoides and K. latifolia. The photosynthetic capacity of R. maximum was the most sensitive to water stress followed by R. periclymenoides. K. latifolia was able to modify its conductance rates to reduce water loss and maintain constant leaf water potential minimizing photosynthetic inhibition. R. periclymenoides showed extreme luxury spending of water indicated by high conductance and low photosynthesis. The ecophysiological responses to water and irradiance provided an explanation for the distributions of the species, eg R. maximum leaves are sensitive to elevated irradiance, and carbon gain is strongly influenced by water stress. Thus, R. maximum will perform best in low irradiance environments with ample water. -from Authors
The segregated distributions of Rhododendron maximum (valley positions), Rhododendron periclymenoides (NE slopes), and Kalmia latifolia (SW slopes) were compared to the respective irradiance environments. R. maximum, an evergreen species, was most sensitive to high radiation; quantum yield, light saturated photosynthetic capacity, photosynthesis per chlorophyll, and water use efficiency decreased at high ambient irradiance. These characteristics limit growth on high irradiance SW slopes. Both K. latifolia and R. periclymenoides improve photosynthetic performance at high ambient irradiance. The deciduous R. periclymenoides continued increasing leaf conductance at high irradiance without an increase in photosynthesis indicating a possible limitation by water in high light environments such as SW slopes. The evergreen K. latifolia had reduced photosynthetic capacity and reduced water use efficiency when grown in low irradiance conditions which coincides with its higher abundance on high light, SW slopes. -from Authors
Multivariate analysis of an extensive palyno‐logical database for Europe has enabled reconstruction of broad‐scale vegetation history. Whereas many major features of present vegetation patterns were established early in the Holocene, floristic composition of the forests has changed continuously up to the present day. For example, although ‘mixed deciduous forests’ had reached approximately their present extent in northwest Europe by 8000 B.P., Tilia peaked in abundance in these forests during the middle post glacial, whereas Pinus was most abundant in these forests during the early post‐glacial and Fagus increased in abundance only in recent millennia. Pollen‐climate response surfaces for major pollen taxa show how their distribution and abundance patterns relate to contemporary climate.
Past forest‐compositional changes were responses to climatic changes, the nature of which can be inferred from pollen‐climate response surfaces. Post‐glacial climate changes have been different in magnitude and direction in different regions of Europe. For example, in recent millennia the vegetation changes indicate decreasing summer temperatures in northern Europe but increasing summer temperatures in the Mediterranean region. The way in which vegetation responded to past climatic changes gives insight into the likely response of vegetation to future climate changes induced by the ‘greenhouse effect’.
New detailed pollen analysis of the lower part of the Upper Pliocene Semaforo section (Crotone, Italy) documents cyclic behavior of vegetation at the beginning of the Northern Hemisphere glaciations. The competition between four vegetation units (subtropical humid forest, deciduous temperate forest, altitudinal coniferous forest, and open xeric assemblage) probably reflects modifications of vegetation belts at this montane site. Several increases in herbaceous open vegetation regularly alternate with subtropical humid forest, which expresses rapid climatic oscillations. The complete temporal succession—deciduous forest (rich in Quercus), followed by subtropical humid forest (Taxodiaceae and Cathaya), then altitudinal coniferous forest (Tsuga, Cedrus, Abies, and Picea), and finally herbaceous open vegetation (Graminae, Compositae, and Artemisia )—displays the climatic evolution from warm and humid interglaciation to cold and dry glaciation. It also suggests an independent variation of temperature and humidity, the two main climatic parameters. The vegetation history of southern Calabria recorded in the Semaforo section have been correlated with the ∂18O signal established in the Atlantic Ocean.
The genus Zelkova contains species which are nowadays distributed in an extremely fragmentary, mainly Asiatic, area. The Island of Crete retains geographically the species nearest to Italy. Fossil leaves and pollen discovered in some sites of Central Italy furnish evidence of the distribution of these trees before and during the Last (Eemian) Interglacial and of their persistence during part of the Last (Wurmian) Glaciation. The evidence is seen in two pollen diagrams from boreholes at Castiglione and Fucino which have stratigraphic continuity; at the base of the series Zelkova reaches conspicuous peaks in a phase which can be correlated with the Eemian Interglacial. During the climatic fluctuations of the last glacial Zelkova disappears in steppe periods and spreads again in favourable times up to the time of extinction, which seems to occur in both series somewhat before the latest glacial acme.
The knowledge of the age of individual trees and of population age structure is of great importance for conservation purposes. In Mediterranean areas, however, trees are rarely used for dendroecological studies as ring growth is strongly perturbed by browsing and other disturbances. This study focused on the Tertiary relict tree species Zelkova abelicea (Ulmaceae) endemic to the mountains of Crete (Greece) and searched for new approaches to estimate the age of threatened trees in severely browsed populations. Our results demonstrate that dwarfed Z. abelicea trees can attain ages >500 yr and that such individuals often surpass normally growing trees of the same population in number and age. These findings significantly change the perception of population age structure in forest remnants of Mediterranean landscapes. Additionally, we show that tree age is well correlated (64%) with trunk circumference, for severely browsed dwarfed trees, however not so much (11%) for normally developed, large trees. Thus, our results can be used directly for age estimations of severely dwarfed Z. abelicea individuals in the field and the new approach can be easily reproduced for other threatened tree species affected by strong browsing pressure. Future conservation efforts and management strategies should, therefore, take into account not only normally developed trees but also severely browsed individuals and their populations.
In early autumn 2009 a new population of Zelkova sicula, a very threatened tree species endemic to Sicily, has been found some 17km east from the first and unique population previously known. The abiotic
(slope, rock and stone outcrop cover, environmental stress, etc.) and biotic (plant species composition,
vegetation mean height, total cover, etc.) features of 30 plots selected within the two populations were
investigated in order to contribute at clarifying the actual and potential eco-geographic range of this
species. Data analysis showed that the floristic differences among the sampled plots mostly relate to
the rather high micro-habitat amplitude of the target species and the tree size. As in both populations
Z. sicula appears to currently prefer hollow trails (“thalwegs” in hydrogeological terminology), the
assumption may be confirmed that in the past it probably was more widespread in fresher and more
humid environments. This hypothesis appears to be sound if we consider the ecological requirements of all the existing Zelkova species.
Field work during twenty years in the mountains of Crete has disclosed that the endemic deciduous tree Zelkova abelicea is more abundant than hitherto reported. The number of mature and old trees is estimated to reach several hundreds, while Z. abelicea scrub browsed by sheep and goats comprises thousands of individuals. The species is extremely resistant to browsing and regenerates by suckers after forest fires. Z. abelicea suckers freely and suckering is an efficient way of propagation in the wild, while natural regeneration by seed was very rarely seen. Root cuttings from all four mountain ranges of Crete were taken to Denmark and 50 % successfully rooted. Best results were obtained with root cuttings taken in late autumn. Branch cuttings of newly matured shoots from young plants were rooted with good results when taken after midsummer. Z. abelicea has been grown outdoors in milder areas of Scandinavia during five years with only insignificant frost damage after cold winters. Currently it is not threatened with extinction but remains vulnerable.
The aim of this study is to classify and describe plant communities of mountain woodlands in the western half of Crete and to relate their species composition to environmental factors with particular reference to grazing. From a total of 232 original phytosociological relevés we classifi ed eight plant communities (plus several subunits). The plant communities were assigned to associations of the class Quercetea ilicis, herein specifi cally to the alliances Erico-Quercion ilicis, Quercion calliprini and Aceri-Cupression sempervirentis. Correspondence analysis revealed a separation of the chiefl y calcifuge Quercus ilex and Q. pubescens associations with more favourable water supply from the woodlands dominated by Q. coccifera, Acer sempervirens, Cupressus sempervirens and Pinus brutia, growing on hard limestone under drier conditions. Species composition in the latter group of woodlands follows an altitudinal gradient, expressing favourable moisture and, on Plattenkalk, nutrient supply at higher elevations. An ecogram was drawn displaying the relative ecological range of each community along moisture and temperature gradients. Silvopastoral impact was different at species response level, and 'tolerators', 'indicators', and 'avoiders' of grazing may be distinguished. Floristic differentiation related to wood-pasture within given associations was not found, indicating high grazing pressure throughout the stands. In most wood-pastures, especially broadleaved (semi-)evergreen, stands are structurally unbalanced, lack tree rejuvenation and require periods of regeneration from browsing. To allow regeneration and monitoring, we advocate sets of sizable exclosures in different areas and elevations, representing all relevant associations.
The vegetation at elevations above 1,400 m in the south Aegean island of Crete (Greece) is studied and revised. By means of phytosociological classification (assisted by TWINSPAN) and ordination (Detrended correspondence analysis, DCA), the plant communities and abiotic (environmental, geographical) factors governing the variance in vegetation are described and discussed. The analyses are based on 492 sample plots from the three major mountain ranges of Crete. All published data available, as well as own unpublished relevés are included. Since the plots differ much with respect to species number and plot size, and to combine different subsets and different data properties, various data sets are used for DCA ordination. Data on environmental variables are used supplementarily. Ordination results suggest the following factors to be of major effect on the variance in vegetation: Rock type, soil type, altitude, geographical situation, degree of substrate fixation, and inclination. The representation of local and regional endemics in the vegetation increases with altitude and along the habitat type series: phrygana and woodland fixed slopes dolines screes. A synoptic table of 26 columns (vegetation types and subtypes) is presented. The vegetation consists of the tragacanth formation of fixed slopes (8 columns), swards and scrub of doline grounds (9), scree vegetation (4), and rupicolous chasmophytic vegetation (2). Phrygana (2) and woodland vegetation (1) are marginal. A hierarchical conspectus of the syntaxa is provided which includes the following nomenclaturally relevant new or validated names of various ranks (in alphabetic order): Alysso sphaciotici-Valantion apricae, Arenario fragillimae-Silenetum antri-jovis, Arenarion creticae, Astragalion cretici, Berberido creticae-Astragaletum cretici, Cicero incisi-Silenetum variegatae, Colchico cretensis-Cirsion morinifolii, Fumano paphlagonicae-Helianthemetum hymettii, Gypsophilo nanae-Arenarietum creticae, Hyperico kelleri-Anchusetum cespitosae, Lomelosio sphacioticae-Centranthetum sieberi, Paronychio macrosepalae-Juniperetum oxycedri, Saturejo spinosae-Scutellarietalia hirtae, Sideritido syriacae-Verbascetum spinosi, Verbascion spinosi.
Model transferability (extrapolative accuracy) is one important feature in species distribution models, required in several ecological and conservation biological applications. This study uses 10 modelling techniques and nationwide data on both (1) species distribution of birds, butterflies, and plants and (2) climate and land cover in Finland to investigate whether good interpolative prediction accuracy for models comes at the expense of transferability – i.e. markedly worse performance in new areas. Models’ interpolation and extrapolation performance was primarily assessed using AUC (the area under the curve of a receiver characteristic plot) and Kappa statistics, with supplementary comparisons examining model sensitivity and specificity values. Our AUC and Kappa results show that extrapolation to new areas is a greater challenge for all included modelling techniques than simple filling of gaps in a well-sampled area, but there are also differences among the techniques in the degree of transferability. Among the machine-learning modelling techniques, MAXENT, generalized boosting methods (GBM), and artificial neural networks (ANN) showed good transferability while the performance of GARP and random forest (RF) decreased notably in extrapolation. Among the regression-based methods, generalized additive models (GAM) and generalized linear models (GLM) showed good transferability. A desirable combination of good prediction accuracy and good transferability was evident for three modelling techniques: MAXENT, GBM, and GAM. However, examination of model sensitivity and specificity revealed that model types may differ in their tendencies to either increased over-prediction of presences or absences in extrapolation, and some of the methods show contrasting changes in sensitivity vs specificity (e.g. ANN and GARP). Among the three species groups, the best transferability was seen with birds, followed closely by butterflies, whereas reliable extrapolation for plant species distribution models appears to be a major challenge at least at this scale. Overall, detailed knowledge of the behaviour of different techniques in various study settings and with different species groups is of utmost importance in predictive modelling.
Accurate modeling of geographic distributions of species is crucial to various applications in ecology and conservation. The best performing techniques often require some parameter tuning, which may be prohibitively time-consuming to do separately for each species, or unreliable for small or biased datasets. Additionally, even with the abundance of good quality data, users interested in the application of species models need not have the statistical knowledge required for detailed tuning. In such cases, it is desirable to use ‘‘default settings’’, tuned and validated on diverse datasets. Maxent is a recently introduced modeling technique, achieving high predictive accuracy and enjoying several additional attractive properties. The performance of Maxent is influenced by a moderate number of parameters. The first contribution of this paper is the empirical tuning of these parameters. Since many datasets lack information about species absence, we present a tuning method that uses presence-only data. We evaluate our method on independently collected high-quality presenceabsence data. In addition to tuning, we introduce several concepts that improve the predictive accuracy and running time of Maxent. We introduce ‘‘hinge features’ ’ that model more complex relationships in the training data; we describe a new logistic output format that gives an estimate of probability of presence; finally we explore ‘‘background sampling’’ strategies that cope with sample selection bias and decrease model-building time. Our evaluation, based on a diverse dataset of 226 species from 6 regions, shows: 1) default settings tuned on presence-only data achieve performance which is almost as good as if they had been tuned on the evaluation data itself; 2) hinge features substantially improve model
The Tertiary vegetation of Europe evolved from paratropical to warm-temperate and temperate forms in response to a progressive, non-linear, climatic cooling. Its vegetational forms are composed mainly of two separate ecological units: the evergreen, laurophyll paleotropical geoflora and the deciduous, broad-leaved Arctotertiary geoflora. The development of the Tertiary climate and its interaction with the vegetation are convincingly indicated by the geoflora''s migration; the changes in its composition; and the development of the Tertiary forest, swamp, and aquatic plant communities. The paleotropical geoflora is characterized in the upper Cretaceous to the upper Miocene by paratropical rain forest, subtropical rain and laurel forests, temperate laurel forests and edaphically-mediated formation of laurel-conifer forests. The Arctotertiary geoflora advanced into Europe in waves since the Paleocene and formed the basis for the Tertiary mixed mesophytic forests. These can be divided into warm-temperate rain forests, oak-hornbeamchestnut or mixed beech-oak-hornbeam forests, and edaphic formations such as bottomland and swamp forests. Beginning in the lower Cretaceous, the hydrophytic vegetation developed independently of the forest vegetation and formed very diverse herbaceous fresh water, swamp, salt water, and coastal formations. Considerable differences in composition allow to separate floral regions and provinces in Eurosiberia. Instead of three ill-defined floral regions in the Paleocene, there are four well-defined floral regions in the Pliocene. A Mediterranean region cannot be recognized, although Mediterranean (eumesogeic) floral elements appear in the Eocene/Oligocene and thereafter. The Mediterranean sclerophyll forests probably arose after the destruction of the laurophyll forests during the Pleistocene.
Patterns of mitochondrial DNA (mtDNA) variation revealed by RFLP were investigated for 63 individuals of the common fig, Ficus carica L., in 15 supposedly natural populations throughout the Mediterranean basin. Fifteen haplotypes were detected using one restriction enzyme (HindIII) and four probes (atp, coxIII, nad3rpsl2 and rps12). Mitochondrial diversity within populations varied from monomorphic to entirely polymorphic and population differentiation was high (FST = 0.323, P –5). Seven groups of populations were defined on the basis of genetic and geographic proximity and lead to significant pairwise FST estimates except for the Corsican group which was similar to the Moroccan one. Fig populations were structured into three clusters: Balearic, West and East Mediterranean gene pools. The low diversity and strong differentiation of the Balearic populations strongly supports an ancient origin and the presence of natural populations in this area before domestication. Significant genetic differentiation between the West and East Mediterranean probably also reflects a diversification of the common fig over the Mediterranean basin preceding domestication. In contrast, Italian island populations seem to result from introduced cultivated fig since they present continental haplotypes. Our study represents a first mtDNA polymorphism survey and these indications should be confirmed by analysing local cultivated forms from the Baleares and from Italian islands and further natural populations from the East Mediterranean.
In this study, 23 previously identified Mendelian RAPD markers and 16 polymorphic allozymic markers were used to assess divergence among two Greek populations and five Italian populations of Pinus leucodermis. Confidence intervals of observed genetic divergence were obtained using bootstrap analysis. Divergence among Italian populations was found to be about as large as that between Italian and Greek populations. Since it is likely that the split of two nuclei took place more than 10,000 years ago, a larger differentiation between, rather than within, the above nuclei was expected. If genetic drift was responsible for the larger divergence of Italian populations, large randomly generated disequilibrium between alleles at neutral, unlinked loci was expected. Indeed, the proportion of pairs of loci showing a non-random association of alleles within each of the Italian populations was larger than what was expected by pure chance (7.95–10.88%). Effective population size based on randomly generated disequilibrium was quite small for three out of the five populations considered (N
e
=17.31±1.88, 16.57± 1.73, and 31.41±7.26, respectively). The implications of the results with respect to the conservation of endangered species of trees are discussed.
Assessing the potential future of current forest stands is a key to design conservation strategies and understanding potential future impacts to ecosystem service supplies. This is particularly true in the Mediterranean basin, where important future climatic changes are expected. Here, we assess and compare two commonly used modeling approaches (niche- and process-based models) to project the future of current stands of three forest species with contrasting distributions, using regionalized climate for continental Spain. Results highlight variability in model ability to estimate current distributions, and the inherent large uncertainty involved in making projections into the future. CO2 fertilization through projected increased atmospheric CO2 concentrations is shown to increase forest productivity in the mechanistic process-based model (despite increased drought stress) by up to three times that of the non-CO2 fertilization scenario by the period 2050–2080, which is in stark contrast to projections of reduced habitat suitability from the niche-based models by the same period. This highlights the importance of introducing aspects of plant biogeochemistry into current niche-based models for a realistic projection of future species distributions. We conclude that the future of current Mediterranean forest stands is highly uncertain and suggest that a new synergy between niche- and process-based models is urgently needed in order to improve our predictive ability.