My research aims to bring new insights into the ecological and evolutionary processes that explain species distributions and shape biodiversity patterns worldwide, with a special focus on conservation biology. I am primarily focused on three questions: (1) why species are distributed non-randomly on Earth? (2) What is the relative role of the ecological and evolutionary processes on the diversity patterns we observe today? and (3) How can we prevent biodiversity loss facing global change? These are complicated questions that require the integration of a wide range of disciplines, taxa, and scales – since explanations for diversity patterns and diversity loss are scale-dependent.
These are (or have been) my main research lines so far:
Fragmentation theory and species extinction thresholds
Two key issues concerning conservation are the amount of habitat needed to achieve conservation goals and the importance of habitat fragmentation. Habitat fragmentation is an element of the pattern of habitat that differs from how much habitat there is. However, historically, the term ‘fragmentation’ has been used to illustrate human practices that destroy habitat, even though habitat can be removed without increasing fragmentation. This misinterpretation has generated confusion, complicating the understanding of the impacts of habitat amount and fragmentation on biodiversity. Ecological theory further predicts that fragmentation aggravates impacts of habitat loss, increasing the extinction threshold of habitat specialists, that is, the minimum amount of habitat below which a population cannot persist and becomes locally extinct. Although this theory has received much attention due to its implications for biodiversity conservation, contradictory empirical results have fuelled claims that fragmentation has been overemphasized, and more attention should be given to habitat loss for preserving species. The debate is still ongoing. Are theoretical models missing important processes? or, might problems lie in the structure of the empirical studies or in the interpretation of their results? These are among the questions that I am trying to answer.
Biogeographic patterns at continental and global scales
Species distributions are not random. From the late 19th century, faunal delimitations have attracted great interest to understand the ecological and evolutionary forces shaping organism distributions. Recently, the development of quantitative methods together with improved data availability has stimulated analytically biogeographic regionalizations. Delineation of biogeographic regions is now frequently the initial step for conservation planning and management, and clustering procedures capable of capturing the spatial structure of species composition data are being used increasingly by conservation biologists as well as biogeographers. One of the main drawbacks, however, of current clustering analytical methods is that it is difficult to know the final number of clusters (regions), that is to say, when to stop the clustering analysis running? A potential solution, generally used, is to specify the number of clusters (or regions) beforehand based on, for instance, environmental or vegetation units. However, this may lead to arbitrary results. To avoid this pitfall, I have used clustering analytical techniques like k-means and v-fold cross validation and an innovative and powerful algorithm named affinity propagation to delimitate optimal number of bioregions for major animal taxa in Europe and the world.
Community phylogenetics, niche conservatism and trait evolution
Recently, I have expanded my research towards the fields of community phylogenetics, niche conservatism, and the so-called functional biogeography, with a particular interest in the influences of biogeographic processes on local-scale patterns. Community phylogenetics attempts to link the macro-evolutionary processes that act on clades to their present-day ecological structure. Moreover, understanding how individual traits evolve or multiple traits co-evolve can help us to understand how we might expect species to evolve in response to climate change and other stressors. My interest has focused on the role of evolutionary history on contemporary community composition and interactions between species’ traits and environment. Many of the ecological patterns observed in nature and the traits related to them have an evolutionary component. In other words, organism ecological interactions affect the evolution of species, so I see no reason not to examine ecological and evolutionary interactions at the same time. What are the relative roles of ecology and evolution as drivers of community assembly? How species’ niche conservatism and evolutionary history of traits influence species distributions? are among the central questions I aim to answer.
Identifying drivers of population extirpations within the species’ geographical ranges
Human modification of the environment (e.g. habitat loss and fragmentation) is the major driver of local population extirpations; however, there is ongoing debate about the role that intraspecific variation in vulnerability plays in determining vulnerability to extirpation. Theory predicts that this vulnerability depends on the spatial configuration of suitable environmental conditions, namely, on the ecological and evolutionary factors that have imprinted to local populations a natural or intrinsic ability to tolerate anthropogenic threats (i.e. vulnerability per se). I am involved in building a novel biogeographic framework to incorporate the species environmental or natural context into ecological models, to test whether the contraction of species ranges differs with the spatial context and then to control analytically for the distribution of human threats to disentangle vulnerability per se from vulnerability caused by exposure to threats. The ultimate goal is to include the species inherent vulnerability as a key intrinsic trait into models predicting species extinction risk.
Marta Rueda 