ECR feature: Pablo Castro Sánchez-Bermejo

Pablo is a PhD student at the Martin Luther University Halle-Wittenberg in Germany. He is an ecologist with a special interest in community and functional ecology. Here, Pablo shares his recent work on how the gradient of aridity drives the loss of taxonomic and functional diversity in dung beetle communities in three different deserts.

The PhD student Pablo Castro Sánchez-Bermejo

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Institute. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Puschstraße 4, Leipzig 04103, Germany

Martin Luther University Halle-Wittenberg, Institute of Biology/Geobotany and Botanical Garden, Halle (Saale), Germany

Academic life stage. PhD student

Major research themes. Trait-based functional ecology and community ecology

Current study system. Dung beetles of the Scarabaeidae family primarily use the dung of mammals for feeding and nesting. That is why these organisms are crucial for the decomposition and recycling of dung into the soil. Since this taxonomic group has an important function in ecosystems, these organisms are good proxies for changes in the environment where they live. Also, the responses of this taxonomic group to large-scale environmental gradients are generally well-known, though so far, we know very little about the effects of aridity. Especially, it is urgent to understand the functional diversity responses of this group, which is crucial to better explain ecosystem functioning.

Recent JBI paper. Castro Sánchez-Bermejo, P., deCastro-Arrazola, I., Cuesta, E., Davis, A. L. V., Moreno, C. E., Sánchez-Piñero, F., & Hortal, J. (2022). Aridity drives the loss of dung beetle taxonomic and functional diversity in three contrasting deserts. Journal of Biogeography, 49, 2243–2255.

Motivation behind this paper. Drylands cover more than a third of the Earth’s land mass and are home to more than 38% of the world’s population.  It is alarming that these complex and amazing ecosystems are especially vulnerable to climate change and land degradation. Increased aridity in drylands has been driven by global warming, and therefore studying how ecological communities respond to gradients of increasing aridity remains crucial to understanding the effects of climate change on biodiversity. Furthermore, while the responses of some taxonomic group, such as plants, have been widely studied, we still lack knowledge about the responses of many animal groups to aridity gradients.

Scarabeus sacer in Morocco. This species belongs to the guild of the rollers, which sculpt the dung into a ball using his hind legs and roll it away before burying the dung in the soil. Photo taken by Fernando Urbano.

Key methodologies. In this paper, we characterize dung beetle communities along aridity gradients in three different deserts: Sahara, Kalahari and Chihuahua. We used 20 quantitative and 2 qualitative functional traits that account for dung beetle responses to arid environments to study, not only taxonomic responses but also changes in trait-based functional indices along the aridity gradients. We also attempted to isolate the effect of the different assembly rules (i.e., aridity, biotic interactions and stochastic processes) by using three different null models. One of these null models generates simulated communities randomly from the total species pool in the desert. The other two null models create simulated communities based on the response of species to aridity and the co-occurrence of species, respectively. Finally, by comparing all simulated values with that observed in the desert we could addressed the relative importance of the different assembly rules.

Unexpected challenges. In this research, we were expecting to observe a shift from biotic-driven communities (where the role of biotic interactions in community assembly is highly relevant for the assembly of dung beetle communities) in the semi-arid extremes of the gradient to aridity-driven communities in the hyper-arid areas. However, we found little evidence for similarity-limiting processes in assembling dung beetle communities. Instead, it appears that abiotic factors are the primary assembly rule along the entire aridity gradient.

Scarabeus sacer and Esymus finitumus in Morocco. Photo taken by Fernando Urbano.

Major results. We observed a decrease of both taxonomic richness and functional dispersion along the gradients of increasing aridity. This pattern seems to be the result of aridity, while limiting similarity or stochastic processes do not seem to be of great importance for the assembly of these communities. Also, in addition to the general patterns, it appears that different regional species pools respond to aridity in different ways. As climate change drives increased aridity, future dryland expansion scenarios may result in a decrease in taxonomic and functional diversity, while this would enhance the effect of abiotic conditions as the main filter in the assembly of dryland dung beetle communities.

Next steps for this research. In our recent study, we focused on examining dung beetle communities in three deserts, but to better understand the responses of this group to aridity, future research should include a broader representation of drylands, and even including aridity gradients in cold drylands (e.g., Greenland, the Patagonian Steppe). In addition, other aspects of biodiversity besides taxonomic and functional diversity, such as phylogenetic diversity, is crucial to better represent changes in these communities and the community assembly in drylands.

If you could study any organism on Earth, what would it be? Even though I have experience in plant ecology, and specifically working with trees, I am not very interested in any specific organism or taxonomic group. Instead, I would rather choose groups that I can use as models to test hypotheses in the fields I am interested in (community assembly, biotic interactions, functional diversity). This is why I am not afraid to work with different taxonomic groups, including plants, dung beetles, and hopefully, other organisms in the future.

Infographic summarizing some of the results in the paper. Illustrations were prepared by the PhD student.

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