How Do Taxonomic and Functional Diversity Metrics Change Along an Aridity Gradient in a Tropical Dry Forest?

Abstract

Ecological indicators based on biodiversity metrics are valuable and cost-effective tools to quantify, track and understand the effects of climate change on ecosystems. Studying changes in these indicators along climatic gradients in space is a common approach to infer about potential impacts of climate change over time, overcoming the limitations of lack of sufficiently long time-series data. Here, we studied the response of complementary biodiversity metrics in plants: taxonomic diversity (species richness and Simpson index) and functional diversity (diversity and redundancy) in 113 sampling sites along a spatial aridity gradient (from 0.27 to 0.69 of aridity index-AI) of 700 km in a Tropical dry forest. We found different responses of taxonomic and functional diversity metrics to aridity. Species diversity showed a hump-shaped curve peaking at intermediate levels of aridity between 0.38 and 0.52 AI as an ecotone, probably because it is where most species, from both drier and more mesic environments, still find conditions to co-exist. Functional diversity showed a positive linear relation with increasing aridity, suggesting higher aridity favors drought-adapted species with diverse functional traits. In contrast, redundancy showed a negative linear relation with increasing aridity, indicating that drier sites have few species sharing the same functional traits and resource acquisition strategies. Thus, despite the increase in functional diversity toward drier sites, these communities are less resilient since they are composed of a small number of plant species with unique functions, increasing the chances that the loss of one of such “key species” could lead to the loss of key ecosystem functions. These findings show that the integration of complementary taxonomic and functional diversity metrics, beyond the individual response of each one, is essential for reliably tracking the impacts of climate change on ecosystems. This work also provides support to the use of these biodiversity metrics as ecological indicators of the potential impact of climate change on drylands over time.

A Functional Trait-Based Approach to Evaluate the Resilience of Key Ecosystem Functions of Tropical Savannas

“…As we used response diversity as an indicator of the resilience of the functional groups [45], we can state that the resilience of all groups has eroded since the great drought. Oliveira [87] showed that communities in drier sites along an aridity gradient in a South American dry forest presented a smaller functional redundancy and are therefore less resilient, which is supported by our results. Several research studies have shown the negative effects of the great drought on woody populations in terms of density and species' composition [15,21,29,88].…”

Season‐driven climatic variables influence the temporal patterns of functional diversity and taxonomic dissimilarity of dung beetles in introduced Brazilian pasture ecosystem

“…Our study also provides evidence that some facets of diversity, such as functional diversity, may respond differently to seasonal variations in environmental conditions. Studies with different biological groups in distinct ecosystems have shown that other facets of diversity can react differently to environmental stressors (Correa & da Silva, 2022; De Pauw et al, 2021; Oliveira et al, 2022; Rivera et al, 2022). This result reinforces the need to investigate more than one facet of diversity to obtain a more robust picture of species responses to environmental changes (Devictor et al, 2010).…”

Harnessing Computational Methods to Characterize Chemical Impacts on Biodiversity

“…Such loss can be translated into broader alteration of ecosystem function and effects on important ecosystem services such as nutrient recycling, carbon sequestration, and many others. In developing trait-based approaches to monitor chemical impacts on ecosystems, basic challenges include which traits are most relevant for ecosystem function and what metrics can be used to characterize alterations in those traits. , Indicators for functional diversity include measures of functional redundancy (i.e., analogous traits in different species of an ecosystem that contribute to the same ecosystem function), and direct field-based measurements of ecosystem functions are frequently used to characterize changes in ecosystem traits. For example, oxygen concentrations can be monitored to approximate respiration rates in rivers and streams, while leaf-litter breakdown rates and microbial activity can be monitored to assess functional integrity of streams based on how leaves are processed by stream communities .…”