Christophe Randin

University of Lausanne | UNIL · Department of Ecology and Evolution

http://www.archeologia-magazine.com/numero-547/l-ours-l-art-prehistorique.4556.php

Collection of R functions and data sets for the support of spatial ecology analyses with a focus on pre-, core and post- modelling analyses of species distribution, niche quantification and community assembly. Written by current and former members and collaborators of the ecospat group of Antoine Guisan, Department of Ecology and Evolution (DEE) &...

Although, in many organisms, genotypes are adapted to specific environmental conditions, the identification of the ecological factors explaining patterns of local adaptation is not a trivial task. In relation to the cosmopolitan barn owl (Tyto alba), its plumage varies from white to dark pheomelanic and shows a difference in the number and size of...

Attempts at explaining range limits of temperate tree species still rest on correlations with climatic data that lack a physiological justification. Here, we present a synthesis of a multidisciplinary project that offers mechanistic explanations. Employing climatology, biogeography, dendrology, population and reproduction biology, stress physiology...

Mountain regions worldwide are particularly sensitive to on-going climate change. Specifically in the Alps in Switzerland, the temperature has increased twice as fast than in the rest of the Northern hemisphere. Water temperature closely follows the annual air temperature cycle, severely impacting streams and freshwater ecosystems. In the last 20 y...

The tendency of trees to grow taller with increasing water availability is common knowledge. Yet a robust, universal relationship between the spatial distribution of water availability and forest canopy height (H) is lacking. Here, we created a global water availability map by calculating an annual budget as the difference between precipitation (P)...

Studying the geographic variation of phenotypic traits can provide key information about the potential adaptive function of alternative phenotypes. Gloger's rule posits that animals should be dark- vs. light-colored in warm and humid vs. cold and dry habitats, respectively. The rule is based on the assumption that melanin pigments and/or dark color...

Aim To incorporate changes in alpine land cover (tree line shift, glacier retreat and primary succession) into species distribution model ( SDM ) predictions for a selection of 31 high‐elevation plants. Location Chamonix Valley, French Alps. Methods We fit linear mixed effects ( LME ) models to historical changes in forest and glacier cover and p...

Bumblebees represent an active pollinator group in mountain regions and assure the pollination of many different plant species from low to high elevations. Plant-pollinator interactions are mediated by functional traits. Shift in bumblebee functional structure under climate change may impact plant-pollinator interactions in mountains. Here, we esti...

Snow cover is an important control in mountain environments and a shift of the snow‐free period triggered by climate warming can strongly impact ecosystem dynamics. Changing snow patterns can have severe effects on alpine plant distribution and diversity. It thus becomes urgent to provide spatially explicit assessments of snow cover changes that ca...

Tree species display different abundance patterns over the landscape due to a number of hierarchical factors, all of which have implications when modeling their distribution. While climate is often the primary driver for global to regional scale tree species distributions, modeling of presence and abundance patterns at finer scales, and in landscap...

Identifying the boundary of a species' niche from observational and environmental data is a common problem in ecology and conservation biology and a variety of techniques have been developed or applied to model niches and predict distributions. Here, we examine the performance of some pattern‐recognition methods as ecological niche models ( ENM s)....

Recent advances in remote sensing technologies have facilitated the generation of very high resolution (VHR) environmental data. Exploratory studies suggested that, if used in species distribution models (SDMs), these data should enable modelling species' micro-habitats and allow improving predictions for fine-scale biodiversity management. In the...

Most plant physiological processes act on micro-geographic scales within meters or less and on temporal scales of minutes or less. Yet, most studies relating species distribution to climate used typical resolutions of kilometers and months at best. Commonly available climate records from weather stations or freely available coarse-resolution geogra...

Ongoing rapid climate change is predicted to cause local extinction of plant species in mountain regions. However, some plant species could have persisted during Quaternary climate oscillations without shifting their range, despite the limited evidence from fossils. Here, we tested two candidate mechanisms of persistence by comparing the macrorefug...

Aim The aim of this study was to test, based on biological theory, which facet of temperature is most closely associated with the elevational and latitudinal low‐temperature limits of seven European broad‐leaved tree species. We compared three temperature‐related potential constraints across three study regions: (1) absolute minimum temperature wit...

Species distribution models (SDMs) studies suggest that, without control measures, the distribution of many alien invasive plant species (AIS) will increase under climate and land-use changes. Due to limited resources and large areas colonised by invaders, management and monitoring resources must be prioritised. Choices depend on the conservation v...

At high elevation, temperate trees generally exhibit adaptive genetic differentiation in their morphological and physiological traits. On account of this directional selection, we hypothesized that tree populations growing near their upper cold elevational limits exhibit lower phenotypic plasticity of growth and leaf morphological traits in respons...

Species distribution models (SDMs) have been frequently employed to forecast the response of alpine plants to global changes. Efforts to model alpine plant distribution have thus far been primarily based on a correlative approach, in which ecological processes are implicitly addressed through a statistical relationship between observed species occu...

Warming-induced expansion of trees and shrubs into tundra vegetation will strongly impact Arctic ecosystems. Today, a small subset of the boreal woody flora found during certain Plio-Pleistocene warm periods inhabits Greenland. Whether the twenty-first century warming will induce a re-colonization of a rich woody flora depends on the roles of clima...

ABSTRACT Aim We compared the upper limits of 18 deciduous tree species with respect to elevation in Switzerland and latitude in Europe. We hypothesized that species would exhibit the same relative positions along elevation and latitude, which can be expected if species have reached their thermal cold limit along both gradients. Location Europe and...

Understanding the stability of realized niches is crucial for predicting the responses of species to climate change. One approach is to evaluate the niche differences of populations of the same species that occupy regions that are geographically disconnected. Here, we assess niche conservatism along thermal gradients for 26 plant species with a dis...

Aim It is hypothesized that the ecological niches of polyploids should be both distinct and broader than those of diploids – characteristics that might have allowed the successful colonization of open habitats by polyploids during the Pleistocene glacial cycles. Here, we test these hypotheses by quantifying and comparing the ecological niches and n...

The mangrove distribution in South Africa is fragmented and restricted to small forest patches occupying only 16 % of the estuaries within the current range. In this study we used species distribution models to test (1) whether the absence of mangrove forest and its species (Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata) within t...

Rare species have restricted geographic ranges, habitat specialization, and/or small population sizes. Datasets on rare species distribution usually have few observations, limited spatial accuracy and lack of valid absences; conversely they provide comprehensive views of species distributions allowing to realistically capture most of their realized...

Invasive plants can have different effects on ecosystem functioning and on the provision of ecosystem services, with the direction and magnitude of such effects depending on the service and ecosystem being considered, but also on the life strategies of the invaders. Strategies can influence invasiveness, but also key processes of host ecosystems. T...

Phenological events, such as the initiation and the end of seasonal growth, are thought to be under strong evolutionary control because of their influence on tree fitness. Although numerous studies highlighted genetic differentiation in phenology among populations from contrasting climates, it remains unclear whether local adaptation could restrict...

We describe a novel dissimilarity framework to analyze spatial patterns of species diversity and illustrate it with alien plant invasions in Northern Portugal. We used this framework to test the hypothesis that patterns of alien invasive plant species richness and composition are differently affected by differences in climate, land use and landscap...

Webber et al. take a critical view of our findings that niche expansions are rare in plant invaders, arguing mainly that we did not include nonanalog climates in our analyses. Yet, their concerns include misunderstandings and go beyond the scope of our study, which was purposely restricted to analog climates. We further explain why our results rema...

Mangroves are mainly tropical tree species that occur on either side of the equator and because temperature decreases with increasing latitude, the latitudinal limits of mangroves are expected to be mainly controlled by temperature- related drivers. Here, we hypothesized that the mangrove genera (Avicennia and Rhizophora) have the same limiting tem...

Aim The physical and physiological mechanisms that determine tree‐line position are reasonably well understood, but explanations for tree species‐specific upper elevational limits below the tree line are still lacking. In addition, once these uppermost positions have been identified, questions arise over whether they reflect past expansion events o...

Aim Concerns over how global change will influence species distributions, in conjunction with increased emphasis on understanding niche dynamics in evolutionary and community contexts, highlight the growing need for robust methods to quantify niche differences between or within taxa. We propose a statistical framework to describe and compare enviro...

Phenological events such as the initiation and the end of seasonal growth are expected to be under high evolutionary pressure due to their strong influence on tree fitness. A good synchronisation of these two phenological events with climate is crucial to prevent frost damages on leaves or flowers in spring and to be cold-hardened in autumn, while...

Invading a Place Like Home Biological invasions can cause enormous economic problems but they also represent a biological experiment and provide insight into species distributions and range expansion or restriction. Most predictions about when and where species will invade rest on the assumption that invasive species will retain the same climatic n...

Aim Climatic niche modelling of species and community distributions implicitly assumes strong and constant climatic determinism across geographical space. We tested this assumption by assessing how stacked‐species distribution models ( S ‐ SDMs ) perform for predicting plant species assemblages along elevation gradients. Location The western S wis...

The low-temperature range limit of tree species may be determined by their ability to produce and disperse viable seeds. Biological processes such as flowering, pollen transfer, pollen tube growth, fertilization, embryogenesis and seed maturation are expected to be affected by cold temperatures. The aim of this study was to assess the quality of se...

Background/Question/Methods Machine learning provides a promising approach to ecological niche modeling (ENM). Particularly, we submit that the ecological problems of “presence-only” and “presence-absence” modeling may be mapped to the machine learning tasks of one-class and multiple class classification, respectively. We take advantage of this e...

Protecting native biodiversity against alien invasive species requires powerful methods to anticipate these invasions and to protect native species assumed to be at risk. Here, we describe how species distribution models (SDMs) can be used to identify areas predicted as both suitable for rare native species and highly susceptible to invasion by ali...

Continental-scale assessments of 21st century global impacts of climate change on biodiversity have forecasted range contractions for many species. These coarse resolution studies are, however, of limited relevance for projecting risks to biodiversity in mountain systems, where pronounced microclimatic variation could allow species to persist local...

Understanding and predicting biological invasions can focus either on traits that favour species invasiveness or on features of the receiving communities, habitats or landscapes that promote their invasibility. Here, we address invasibility at the regional scale, testing whether some habitats and landscapes are more invasible than others by fitting...

Abiotic factors are considered strong drivers of species distribution and assemblages. Yet these spatial patterns are also influenced by biotic interactions. Accounting for competitors or facilitators may improve both the fit and the predictive power of species distribution models (SDMs). We investigated the influence of a dominant species, Empetru...

Background/Question/Methods and Results/Conclusions Mountain ecosystems were early identified as potentially sensitive to global change. In particular, mountain regions may experience unprecedented rates of warming during the next century, two or three times higher than records of the 20th century. Mountain regions are also experiencing changes i...

Question Does a land-use variable improve spatial predictions of plant species presence-absence and abundance models at the regional scale in a mountain landscape? Location Western Swiss Alps. Methods Presence-absence generalized linear models (GLM) and abundance ordinal logistic regression models (LRM) were fitted to data on 78 mountain plant spec...

Habitat suitability models, which relate species occurrences to environmental variables, are assumed to predict suitable conditions for a given species. If these models are reliable, they should relate to change in plant growth and function. In this paper, we ask the question whether habitat suitability models are able to predict variation in plant...

Aims In perennial species, the allocation of resources to reproduction results in a reduction of allocation to vegetative growth and, therefore, impacts future reproductive success. As a consequence, variation in this trade-off is among the most important driving forces in the life-history evolution of perennial plants and can lead to locally adapt...

Indirect topographic variables have been used successfully its surrogates for disturbance processes in plant species distribution models (SDM) in Mountain environments. However, no SDM Studies have directly tested the performance of disturbance variables. In this study, we developed two disturbance variables: it geomorphic index (GEO) and all index...

Aim We examined whether species occurrences are primarily limited by physiological tolerance in the abiotically more stressful end of climatic gradients (the asymmetric abiotic stress limitation (AASL) hypothesis) and the geographical predictions of this hypothesis: abiotic stress mainly determines upper-latitudinal and upper-altitudinal species ra...

Many studies have investigated the potential impacts of climate change on the distribution of plant species, but few have attempted to constrain projections through plant dispersal limitations. Instead, most studies published so far have simplified dispersal as either unlimited or null. However, depending on the dispersal capacity of a species, lan...

While phenological shifts and migration of isolated species under climate change have already been observed on alpine summits, very few studies have focused on community composition changes in subalpine grasslands. Here we use permanent plots monitored since 1954 and precisely located phytosociological censuses from 1970 to study compositional chan...

Mountain ecosystems will likely be affected by global warming during the 21st century, with substantial biodiversity loss predicted by species distribution models (SDMs). Depending on the geographic extent, elevation range, and spatial resolution of data used in making these models, different rates of habitat loss have been predicted, with associat...

The usefulness of species distribution models (SDMs) in predicting impacts of climate change on biodiversity is difficult to assess because changes in species ranges may take decades or centuries to occur. One alternative way to evaluate the predictive ability of SDMs across time is to compare their predictions with data on past species distributio...

Poster, Geophysical Research Abstracts, Vol. 10

Niche conservatism, the tendency of a species niche to remain unchanged over time, is often assumed when discussing, explaining or predicting biogeographical patterns. Unfortunately, there has been no basis for predicting niche dynamics over relevant timescales, from tens to a few hundreds of years. The recent application of species distribution mo...

The usefulness of species distribution models (SDMs) in predicting impacts of climate change on biodiversity is difficult to assess because changes in species ranges may take decades or centuries to occur. One alternative way to evaluate the predictive ability of SDMs across time is to compare their predictions with data on past species distributio...

Poster, Geophysical Research Abstracts, Vol 9

Due to their conic shape and the reduction of area with increasing elevation, mountain ecosystems were early identified as potentially very sensitive to global warming. Moreover, mountain systems may experience unprecedented rates of warming during the next century, two or three times higher than that records of the 20th century. In this context, s...

Models predicting species spatial distribution are increasingly applied to wildlife management issues, emphasising the need for reliable methods to evaluate the accuracy of their predictions. As many available datasets (e.g. museums, herbariums, atlas) do not provide reliable information about species absences, several presence-only based analyses...

Aim To assess the geographical transferability of niche‐based species distribution models fitted with two modelling techniques. Location Two distinct geographical study areas in Switzerland and Austria, in the subalpine and alpine belts. Methods Generalized linear and generalized additive models (GLM and GAM) with a binomial probability distributio...

Numerous studies have successfully used topographic variables for the prediction of plant species distributions in mountainous areas. A current question is which scale optimizes the predictive power of these variables. Due to the development of airborne radar/laser scanning, very high resolution digital elevation models (VHR DEMs) with a typical re...

1. The ecological niche is a fundamental biological concept. Modelling species' niches is central to numerous ecological applications, including predicting species invasions, identifying reservoirs for disease, nature reserve design and forecasting the effects of anthropogenic and natural climate change on species' ranges. 2. A computational analog...

Climate change will affect species around the world and will cause shifts in species' distributions (1-3). These changes in the distribution of species can lead to changes in the composition and structure of communities and the formation of novel ecosystems which may function differently than the ecosystems of today (4-6). To understand these chang...

Mangroves are forests in the intertidal zone along (sub)tropical coastlines. This vulnerable ecosystem is under threat of increasing coastal human population and land-use changes. Global warming has a major impact on the mangrove distribution as sea level is rising and the position of the intertidal zones is moving landwards. Next to this, an incre...