Good‐bye to tropical alpine plant giants under warmer climates? Loss of range and genetic diversity in<i>Lobelia rhynchopetalum</i>

Aim: Statistical species distribution models (SDMs) are the most common tool to predict the impact of climate change on biodiversity. They can be tuned to fit relationships at various levels of complexity (defined here as parameterization complexity, number of predictors, and multicollinearity) that may co-determine whether projections to novel climatic conditions are useful or misleading. Here, we assessed how model complexity affects the performance of model extrapolations and influences projections of species ranges under future climate change. Location: Europe.Taxon: 34 European tree species. Methods:We sampled three replicates of predictor sets for all combinations of 10 levels (n = 3-12) of environmental variables (climate, terrain, soil) and 10 levels of multicollinearity. We used these sets for each species to fit four SDM algorithms at three levels of parameterization complexity. The >100,000 resulting SDM fits were then evaluated under environmental block cross-validation and projected to environmental conditions for 2061-2080 considering four climate models and two emission scenarios. Finally, we investigated the relationships of model design with model performance and projected distributional changes. Results: Model complexity affected both model performance and projections of species distributional change. Fits of intermediate parameterization complexity performed best, and more complex parameterizations were associated with higher projected loss of current ranges. Model performance peaked at 10-11 variables but increasing number of variables had no consistent effect on distributional change projections. Multicollinearity had a low impact on model performance but distinctly increased projected loss of current ranges. Main conclusions: SDM-based climate change impact assessments should be based on ensembles of projections, varying SDM algorithms as well as parameterization complexity, besides emission scenarios and climate models. The number of predictor variables should be kept reasonably small and the classical threshold of maximum absolute Pearson correlation of 0.7 restricts collinearity-driven effects in projections of species ranges. | 131 BRUN et al.

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“…Chala et al, 2016;Gregr et al, 2018) and As expected, we found parameterizations of intermediate complexity to yield highest TSS and AUC.…”

Section: Discussionsupporting

confidence: 84%

“…transferability) of models fitted from comparably complex parameterizations (e.g. Chala et al, 2016;Gregr et al, 2018) and of comparably complex SDM algorithms (e.g. Randin et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Model complexity affects species distribution projections under climate change

Brun

Thuiller

Chauvier

et al. 2019

Journal of Biogeography

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148

125

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“…Spatially restricted cryophilic species (e.g. Espeletiopsis colombiana , Coespeletia timotensis and Pycnophyllum tetrastichum ) would be particularly prone to a loss of climate niche space (Mavárez, Bézy, Goeury, Fernández, & Aubert, ), in agreement to the expected range contraction and loss in genetic diversity of Afrotropical alpine species suggested by model projections (Chala et al, ). Additional pressures on thermal narrow‐range specialists could arise from increases in seasonal temperature variability (IPCC, ), coupled with decreases in diurnal temperature variability due to faster night‐time versus daytime warming (Easterling et al, ).…”

Section: Discussionsupporting

confidence: 76%

Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Cuesta

Tovar

Llambí

et al. 2019

Journal of Biogeography

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Aim The climate variability hypothesis (CVH) predicts that locations with reduced seasonal temperature variation select for species with narrower thermal ranges. Here we (a) test the CVH by assessing the effect of latitude and elevation on the thermal ranges of Andean vascular plant species and communities, and (b) assess tropical alpine plants vulnerability to warming based on their thermal traits. Location High tropical Andes. Taxon Vascular plants. Methods Temperature data for 505 vascular plant species from alpine communities on 49 summits, were extracted from 29,627 georeferenced occurrences. Species thermal niche traits (TNTs) were estimated using bootstrapping for: minimum temperature, optimum (mean) temperature and breadth (maximum‐minimum). Plant community‐weighted scores were estimated using the TNTs of their constituent species. CVH was tested for species, biogeographical species groups and communities. Vulnerability to global warming was assessed for species, biogeographical species groups and communities. Results Species restricted to the equator showed narrower thermal niche breadth than species whose ranges stretch far from the equator, however, no difference in niche breadth was found across summits’ elevation. Biogeographical species groups distributed close to the equator and restricted to alpine regions showed narrower niche breadth than those with broader ranges. Community‐weighted scores of thermal niche breadth were positively related to distance from equator but not to elevation. Based on their TNTs, species restricted to equatorial latitudes and plant communities dominated by these species were identified as the most vulnerable to the projected 1.5°C warming, due to a potentially higher risk of losing thermal niche space. Main conclusions Our study confirms that the CVH applies to high tropical Andean plant species and communities, where latitude has a strong effect on the thermal niche breadth. TNTs are identified as suitable indicators of species’ vulnerability to warming and are suggested to be included in long‐term biodiversity monitoring in the Andes.

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“…The few grid cells that were not deemed suitable for stem succulents by the models but did contain at least two observed genera were manually assigned as presence. For the assignment of species to the succulent biome (see below), the continuous stem succulents map was converted to binary with a threshold of 33% (partially following Chala et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

Biomes as evolutionary arenas: Convergence and conservatism in the trans‐continental succulent biome

Ringelberg

Zimmermann

Weeks

et al. 2020

Global Ecol Biogeogr

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Aim: Historically, biomes have been defined based on their structurally and functionally similar vegetation, but there is debate about whether these similarities are superficial, and about how biomes are defined and mapped. We propose that combined assessment of evolutionary convergence of plant functional traits and phylogenetic biome conservatism provides a useful approach for characterizing biomes. We focus on the little-known succulent biome, a trans-continentally distributed assemblage of succulent-rich, drought-deciduous, fire-free forest, thicket and scrub vegetation as a useful exemplar biome to gain insights into these questions. Location: Global lowland (sub)tropics. Time period: Present. Major taxa studied: Angiosperms. Methods: We use a model ensemble approach to model the distribution of 884 species of stem succulents, a plant functional group representing a striking example of evolutionary convergence. Using this model, phylogenies, and species occurrence data, we quantify phylogenetic succulent biome conservatism for 10 non-succulent trans-continental plant clades including prominent elements of the succulent biome, representing over 800 species. Results: The geographical and climatic distributions of stem succulents provide an objective and quantitative proxy for mapping the distribution of the succulent biome. High fractions of succulent biome occupancy across continents suggest all 10 nonsucculent study clades are phylogenetically conserved within the succulent biome. Main conclusions: The trans-continental succulent and savanna biomes both show evolutionary convergence in key biome-related plant functional traits. However, in contrast to the savanna biome, which was apparently assembled via repeated local recruitment of lineages via biome shifts from adjacent biomes within continents, the succulent biome forms a coherent trans-continental evolutionary arena for droughtadapted tropical biome conserved lineages. Recognizing the important functional differences between the succulent-rich, grass-poor, fire-free succulent biome and the grass-dominated, succulent-poor, fire-prone savanna biome, and defining them | 1101 RINGELBERG Et aL.

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Good‐bye to tropical alpine plant giants under warmer climates? Loss of range and genetic diversity inLobelia rhynchopetalum

Cited by 96 publications

References 44 publications

Model complexity affects species distribution projections under climate change

Model complexity affects species distribution projections under climate change

Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Biomes as evolutionary arenas: Convergence and conservatism in the trans‐continental succulent biome

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