Our research focuses on understanding the effects of global change on ecosystems, particularly at the population and community levels. We use mainly modeling, in a broad sense, to address these issues. At present, three intertwined topics constitute the core of our research:
Impact of climate changes on the distribution of species, communities and biomes
Climate change is one of the priorities in the conservation and global change sciences, given the threat it poses to biodiversity. At the same time it has boosted basic ecological research on the role of climate as major driver of the functioning of ecosystems at all levels. In my research I focus on how climate changes shift the distribution of species, communities and biomes, following three strategies:
1. Impact of past climate changes. Understanding how species have responded to past climate changes informs how current climate change will impact the distribution of the species. Using niche modeling and combined with genetic analyses as an independent validation, I am describing how multiple species have shifted their distribution since the Last Glacial Maxima (21ky) in a wide variety of taxa and locations and environments including reptiles in North Africa (Anadon et al. 2015), amphibians in East Africa (Freilich et al. 2016), and cactacea plants, trees and terrestrial tortoises in Mexico (in prep).
2. Impact of future climate changes. In the last years it has been produced a rich literature on the impact of future climate of the main challenges now is to introduce biotic interactions and other community patterns or processes (i.e. perturbations, non-equilibrium dynamics) in the equation and predict the impact on communities. My current research efforts in this arena are in these directions. Using a novel approach I recently described how main biomes in the tropical and subtropical Americas (forest, savanna and deserts) are expected to shift under future climate scenarios (Anadón et al 2014).
3. Impact of contemporary climate change. The impact of contemporary climate change (i.e. that occurred during the last decades) can be directly observed and constitutes one of the main direct evidences and sources of information on climate change impact on species and ecosystems. I am leading a multinational and multidisciplinar collaboration network to assess how >400 endemic tree species in Mexico have shifted their distribution in the last century with overall goals of a) testing the relationship between range shifts and species’ traits and b) to study the variations of range shifts across biomes and their drivers.
Range expansions not related to climate: biological invasions and colonization processes
Species can also expand their distribution to new areas because they are introduced by humans (biological invasions) or because, at biogeographical temporal scales, dispersal barriers disappear (e.g. to changes on the sea level). In this second line, I study range expansion of species that are not directly driven by climate.
1. Determinants of successful invasions of exotic species. We have built a georeferenced database of > 15,000 records of invasive species in Spain and Portugal, probably the most comprehensive database on invasive species of a given group at a regional scale. Our database shows that 10% of all bird species of the world have already been introduced in the Iberian Peninsula, pointing out that current databases of invasive species largely underestimate the magnitude of biological invasions (Abellán et al. 2015). Secondly, we have recently showed that determinants of success vary between establishment and spread stages and that niche contraints (climatic matching) is relevant for the spread but not for the establishment (Abellán et al. 2017). Our next step here is develop spatial-explicit expansion models for each one of the species for the Iberian Peninsula in order to understand the factors that affect the expansion of species on a one-by-one basis.
In a similar vein, in collaboration with JA Sánchez-Zapata (UMH), I have developed expansion models for two ungulates (one invasive and the other native) that are expanding their range in the Iberian Peninsula concurrently. Our models have allowed us to identify the determinants of expansion of both species and their negative competitive interaction. In a next step, we are now studying the competitive interaction of both species at a local scale, in order to deep into our understanding in the biotic interactions between native and expanding invasive and species.
2. The genetic signature of range expansions and their consequences. Some of the most determinant but overlooked processes occurring during species’ range expansions are those at the genetic level. In this collaborative research line with researchers at UMH (Spain) we are studying the genetic processes occurring during the expansion of species and their consequences for the fitness of the species, and in last instance, for the expansion process itself. In Graciá et al 2013 we described, for the first time for a vertebrate species, a genetic surfing pattern during the range expansion of the species in the Iberian Peninsula. During this process, alleles that are rare in the founding population become common during the expansion. Combining genetic data with demographic data that we have collected during the last ca. 20 yr of field work we are testing the hypothesis that this genetic surfing process might have led to a decrease in fitness of the species as it expands and might ultimately be main driver of the limits of the species’ range in the Iberian Peninsula.
Assemble of communities along natural -altitudinal- and human gradients
In this third line I study how groups of species functionally related -communities- respond to changing environmental conditions, using a community analytical approach and by sampling large natural or human-created environmental gradients. This is my most recent research line, and that is highly complementary to the previous two lines, in relation to the basic question possed and the approach used.
1. Changes in biological communities along altitudinal environmental gradients. On this first project, funded by USAID, where I am co-PI and I lead the working group on biodiversity, we are studying how biological communities changes along large altitudinal gradients in Nepal. Here we are studying two different systems: one system composed by different and related trophic levels: plants, crops, pollinators and pest species (described above in Section and another system composed by the macro-vertebrate scavenger community.
2. Changes in biological communities along anthropogenic gradients. Pristine ecosystems are increasingly rare in our planet and will become even rarer in this XXI century due to mainly urbanization and agricultural land use changes. It is thus of critical importance to understand how biodiversity and the ecosystems services provided by biodiversity are impacted by these changes. In this research line I am studying how biodiversity, as described by different functional biological communities, varies along large anthropogenic gradients. We are studying how two contrasting communities, soil microbiome and macro-vertebrate scavengers, changes along a >500 km urbanization gradient in the State of New York. This gradient ranges from very densely populated area (New York City) to large pristine areas (Adirondaks Mountains) and includes urban, suburban ex-urban, rural and natural environments. we are studying the functional and compositional changes in the soil microbiome and virome communities along this gradient. In the first case the ultimate goals are a) to describe how the dynamics between the two communities (the microbiome species are host for the virome community) are and how they change along the urbanization gradient, and b) how the ecosystem services provided by the microbiome (C and N cycles) vary. In the second project, PhD student Alexis Brewer is studying how the macro-vertebrate scavenger community and the ecosystem services provided by it (removal of carrion) varies along this same anthropogenic gradient. For this purpose we are using a two approaches, experiments with baited camera traps and isotope analyses to delve into teh trophic ecology of teh obligate scavengers (vultures).