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- Climate Change in Deserts: Past, Present and Future
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Climate Change in Deserts: Past, Present and Future
The following information was supplied regarding data availability:. GenBank accession numbers and newly generated sequences are available in Table S1 , and the georeferences are included in the Supplementary Material. Among North American deserts, the Chihuahuan Desert has the highest levels of diversity and endemism. To understand the effect of future climate change on plants distributed in this arid land and propose effective conservation planning, we focused on five endemic shrubby species that characterize the Chihuahuan Desert and used an integrative approach.
Ecological niche-based modeling, spatial genetics and ecological resistance analyses were carried out to identify the effect of global warming on the studied five shrubby species. Key areas that need to be preserved were identified taking into account the existing protected areas within the Chihuahuan Desert. The extent of future distribution will vary among these species, and on average expansion will occur in the western part of the Chihuahuan Desert.
For most species low environmental resistance to gene flow was predicted, while higher future resistance was predicted for one species that would lead to increased population isolation. The highest haplotype diversity was identified in three hotspots. Based on future suitability of habitat and in the haplotype diversity we suggest preserving two hotspots of genetic diversity in the Sierra Madre Oriental, located in areas without protection.
Global climate change will have an effect in arid adapted plants, favoring expansion in the western of the Chihuahuan Desert however negatively affecting others with high ecological resistance disrupting gene flow. Two hotspots of genetic diversity in the Sierra Madre Oriental should be protected.
The effect of future climate change on organisms has been studied from multiple perspectives, in diverse biomes, ecosystems, farming landscapes and for many taxa and functional groups of organisms. The main effects of climate change are associated with demographic threats, opportunities for expansion, and positive or negative implications with respect to the size and position of species ranges, as well as the genetic variability of populations, disequilibrium in biotic interactions and a variable capacity of adaptation in natural and agricultural systems Harris et al.
Understanding how future climate variation influences ecological and evolutionary processes in organisms is crucial to conservation decision-making. It has been demonstrated that gene flow rates in plants vary enormously depending on the species and populations involved Ellstrand, ; moreover, the effect of gene flow might still be significant at distance of thousands of meters acting as a connecting force for local selection of populations Ellstrand, Ecological niche and gene flow are causally interrelated with the potential for one to impact the other, thus studying both simultaneously should provide stronger predictions of future species distributions.
Just like any habitat, deserts will be affected by climate change. The insularity of the Chihuahuan Desert has produced an area rich in endemic plant species; of the approximately 3, species about one third are endemic Villarreal-Quintanilla et al. Limits of the Chihuahuan Desert and distribution map and images of the five plant species studied. Main biogeographic areas are indicated in addition to occurrence localities. Areas follow Shreve and Morafka A Chihuahuan Desert subprovinces and distribution of studied species.
B Delimitation of the Chihuahuan Desert. C Berberis trifoliolata Berberidaceae. D Ephedra aspera Ephedraceae. E Setchellanthus caeruleus Setchellanthaceae. F Leucophyllum laevigatum Scrophulariaceae. G Lindleya mespiloides Rosaceae. Images taken by Diego F. There are few protected areas located within boundaries of the Chihuahuan Desert.
Here, we focus on the shrubby plants of the Chihuahuan Desert and using prospective ecological niche-based modeling ENM in five endemic species, aim to estimate whether species ranges will vary or remain the same and to identify the areas that are more likely to remain stable.
Additionally, by acquiring molecular data we estimate genetic diversity of populations of these species and determine how it is spatially distributed to determine the degree of vulnerability, taking into account the ecological connectivity of the populations. The goal is to provide guidelines for conservation decision-making based on these data and the existing protected areas.
Using these five indicator endemic shrubby plants we aim to: 1 determine how genetic diversity is spatially distributed in the Chihuahuan Desert; 2 establish the effect of global climate change on their distribution based on predictions of future climate scenarios for ; 3 understand how habitat ecological resistance among species might be affected by future climate change; 4 identify the most vulnerable or resilient populations and evaluate if they are located within protected areas; 5 make recommendations for conservation decision-making.
Field study permissions. Study species. We selected five endemic species to the Chihuahuan Desert Fig. The first is the Mormon tea gymnosperm Ephedra aspera Engelm. The four other species are angiosperms. Berberis trifolilata Moric. Leucophyllum laevigatum Standl.
The rose species Lindleya mespiloides Kunth is the only species of a monotypic genus endemic to the Chihuahuan Desert, with a shrubby or tree-like life form with thick leaves, conspicuous white flowers and dry, capsular fruits Henrickson, Setchellanthus caeruleus Brandegee is the sole species of Setchellanthaceae, a family endemic to the Chihuahuan Desert, and is receiving much interest because it produces glucosinolates and belongs to the group of mustard plants.
Sampling and DNA sequencing. We collected samples from populations of E. For the three remaining species we used previously published sequences B. GenBank accessions representing all haplotypes in the populations of each species are listed in Table S1. Populations studied, indicating population abbreviation, number of plants, geographic region, latitude and longitude where they were collected, as well as molecular diversity indices and their respective haplotypes.
Genetic analyses. Haplotype genetic diversity h was interpolated for each species using a distance weighted interpolation in ArcView v. In order to visualize the genetic diversity on a map, we plotted this interpolation over a hill shade map obtained from the digital elevation model Hydro1K.
We then averaged the genetic diversity of all species to identify the areas that share the highest genetic diversity. Ecological niche-based modeling. They comprised the entire distribution of species the number of records used in each species is given in Table S2. Considering a pixel of one km 2 , ENM was estimated for each species. Environmental inputs were based on the 19 climate variables from the WorldClim data base version 1.
These variables represent global precipitation and temperature conditions for the years — Then we selected a set of uncorrelated variables Pearson correlation coefficients below 0. The latter resulted in a set of eight bioclimatic variables i. In addition, a principal component analysis PCA analysis was conducted to corroborate the most significant climate variables see results in Fig. S1 using the statistical software R with the package raster Thuiller et al.
Species distribution modeling SDM were estimated using the maximum entropy algorithm MaxEnt implemented in the R package biomod2 Thuiller et al. A total of 10 replicates per each species were used and from these, geographic predictions and performance was averaged per species. Model performance was estimated for the projections in the climatic scenario for the present using the statistical metrics relative operating characteristic ROC , TSS true skill statistic and Kappa.
Values for ROC range from zero to one, with values greater than 0. To integrate most of the variation observed in the bioclimatic variables, we alternatively performed a multivariate analysis. A PCA was performed using 19 bioclimatic variables of all the climatic scenarios used in this study and reduce the observed variation on a set of uncorrelated PC axes. Then, we used the PC scores of these axes to generate raster layers for each climate scenario as environmental inputs to estimate SDMs and perform geographic projections.
Loading contributions for each of the PC axes used are showed in Table S4. PCA analyses were conducted in the statistical software R using the package raster Thuiller et al. To predict whether suitability conditions of each species might potentially change in the future we projected the estimated ENMs to future climate scenarios i. The RCPs are coherent with an ample range of probable changes in future human greenhouse gas emissions with the objective or representing their atmospheric concentrations.
RCP 2. In addition, two different general circulation models GCMs for each of these scenarios were used to obtain the geographic predictions. All future environmental layers were based on the WorldClim database version 1. We averaged the suitability values of the two different climate simulations for each RCP scenario to perform geographic projections under future scenarios. Evaluation of protected areas and genetic diversity. To identify whether the areas with the highest genetic diversity lie within protected areas we also overlaid protected areas on the distribution maps of the sampled populations.
Table 2 includes the protected areas within the Chihuahuan Desert. Current and future environmental resistance to gene flow. We estimated ecological resistance among populations using the habitat suitability raster file derived from ecological niche modeling as a conductance matrix in Circuitscape 4.
Environmental resistance was averaged for each species considering current and future climate scenarios and plotted using boxplots.
Haplotype and nucleotide diversity for every population of each species is included in Table 1 and displayed in Figs. The B. Among the populations of all of the species, L. For E. Genetic landscape analysis revealed high haplotype diversity for all species in the northwestern areas of the Chihuahuan Desert with the exception of S.
Table 3 includes Fst estimations for tudied species with their corresponding P -values, indicating that S. Landscape distributions of chloroplast haplotype polymorphism in the five species studied.
Dark gray shaded areas represent suitable areas for the distribution of each species based on the projection of ecological niche models onto future climate scenarios. Black dots represent species populations. Light gray shaded areas in F indicate protected natural areas. Number of populations, and variance components among populations and within populations is indicated.
Model performance evaluated with the ROC is summarized in Table 4 , showing similar values for every studied species. Table 5 includes eigenvalues retrieved by the PCA that were utilized to generate SMDs individual eigenvalues for every species are presented in Table S4.
In general, current ENMs accurately predicted the known distribution of every species Fig. Suitable conditions predicted by current and future climate scenarios were identified in the Mexican Plateau, in the areas corresponding to the Mapimian and Saladan subprovinces as well as in the Sierra Madre Oriental.
Rows in bold represent the variables used to generate raster layers to estimate SDMs and perform projection on geographic space.
Climate Resources at the National Academies
The following information was supplied regarding data availability:. GenBank accession numbers and newly generated sequences are available in Table S1 , and the georeferences are included in the Supplementary Material. Among North American deserts, the Chihuahuan Desert has the highest levels of diversity and endemism. To understand the effect of future climate change on plants distributed in this arid land and propose effective conservation planning, we focused on five endemic shrubby species that characterize the Chihuahuan Desert and used an integrative approach. Ecological niche-based modeling, spatial genetics and ecological resistance analyses were carried out to identify the effect of global warming on the studied five shrubby species. Key areas that need to be preserved were identified taking into account the existing protected areas within the Chihuahuan Desert. The extent of future distribution will vary among these species, and on average expansion will occur in the western part of the Chihuahuan Desert.
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Climate Change in Deserts - Title page. pp iii-iii. Past Present And Future. By Martin Williams. Access. PDF · HTML; Export citation.
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