Biology subjects

Siqueira, T.

Publications and source records attributed to Siqueira, T..

7 recordsLinked to original sources

bioRxiv2025

Accounting for the influence of dissimilarity gradientson community uniqueness

Compositional uniqueness has become increasingly relevant for understanding how local communities contribute to regional biodiversity. The most widely used metric is the Local Contribution to Beta Diversity (LCBD), which is typically regressed against environmental predictors. However, LCBD can vary either because of environmental processes that affect the overall variance in community composition, or because communities change directionally along environmental gradients. The latter implies that LCBD-environment relationships can strongly depend on how the environment is sampled. To address this issue, we introduce Generalised Dissimilarity Uniqueness Models (GDUM), a framework that embeds effects on community uniqueness within pairwise dissimilarity modelling. GDUMs are consistent with conventional uniqueness models, while explicitly accounting for directional changes in composition. This distinction disentangles directional and non-directional drivers of beta diversity, such as environmental filtering versus stochastic processes. By improving interpretability and generalizability, GDUM is a useful tool for understanding beta diversity patterns and projecting biodiversity responses.

ecology↗

bioRxiv2024

The ecological memory of landscape complexity shapes diversity of freshwater communities

Land use change affects the biodiversity of terrestrial landscapes as well as of the freshwater systems they surround, and thereby numerous ecosystem services that are essential for human well-being. Previous research suggests that freshwater systems show delayed responses to abrupt disturbances such as deforestation, however less is known about whether there is a legacy effect of landscape history on freshwater communities under a long history of land use change. We addressed this research gap here by first quantifying the historical complexity of landscapes, including natural and agricultural formations, in terms of their composition and configuration in 26 tropical catchment areas surrounding 101 streams over a 30-year period. We identified clear evidence for a memory effect of past events, whereby historical landscape complexity, measured as the information entropy of landscape composition, positively affected freshwater biodiversity. Finally, using a causal discovery approach, we showed that species richness was causally related to landscape complexity only when historical values were incorporated. Our results corroborate previous work on the positive effect of landscape complexity on biodiversity, and also confirm the role of historical contingencies in predicting future ecological outcomes.

ecology↗

bioRxiv2023

Species interactions drive continuous assembly of freshwater communities in stochastic environments

Understanding the factors driving the maintenance of long-term biodiversity in changing environments is essential for improving restoration and sustainability strategies in the face of global environmental change. Biodiversity is shaped by both niche and stochastic processes, however the strength of deterministic processes in unpredictable environmental regimes is highly debated. Since communities continuously change over time and space -- species persist, disappear or (re)appear -- understanding the drivers of species gains and losses from communities should inform us about whether niche or stochastic processes dominate community dynamics. Applying a nonparametric causal discovery approach to a 30-year time series containing annual abundances of benthic invertebrates across 66 locations in New Zealand rivers, we found a strong asynchronous causal relationship between species gains and losses directly driven by predation indicating that niche processes dominate community dynamics. Despite the unpredictable nature of these system, environmental noise was only indirectly related to species gains and losses through altering life history trait distribution. Using a stochastic birth-death framework, we demonstrate that the negative relationship between species gains and losses can not emerge without strong niche processes. Our results showed that even in systems that are dominated by unpredictable environmental variability, species interactions drive continuous community assembly.

ecology↗

bioRxiv2022

A multi-continental analysis of the responses of freshwater food webs to climate and land use change

O_LIFood web responses to environmental change are not straightforward to understand as they occur through an intricate arrangement of direct and indirect effects. Although previous investigations have advanced knowledge on freshwater food web structure, we must better understand the intricate relationships between the main drivers of environmental change and trophic networks in lentic and lotic ecosystems. C_LIO_LIWe compiled multicontinental data to investigate how climate and land use change are related to the structure of freshwater food webs, considering the inherent differences in lentic and lotic ecosystems. We analyzed the direct and indirect relationships between land use intensity, and temperature and precipitation temporal trends, and food webs using multi-group structural equation modeling. C_LIO_LIThe strength and direction of the relationships between climate, land use, and food webs varied considerably among lentic and lotic ecosystems, but most indicated indirect effects through the number of links in the network. While network connectance both increased and decreased with land use and climate change, the number of trophic levels decreased with land use intensity and maximum temperature and increased with increasing precipitation. Omnivory increased with land use intensity in both ecosystems but was negatively related to changes on maximum temperature in lake food webs. C_LIO_LIEven though food webs are expected to become more connected in face of disturbances, and our work supported this regarding local warming, the negative relationships between network connectance and land use intensification suggests that food webs become more specialized at disturbed sites. On the other hand, reduction in the number of trophic levels indicates the loss of top consumers in face of warming and increasing land use intensity. C_LIO_LIThe response of food webs in both lentic and lotic ecosystems to climate and land use change occurred mostly through changes in species interactions. Our results indicate that the intensification of land use makes food webs more specialized, with less trophic levels. Also, inherent aspects of freshwater ecosystems seemed to play a major role in the way food webs respond to disturbance and must be considered to fully understand and predict the effects of global changes on freshwater biodiversity. C_LI

ecology↗

bioRxiv2019

Heterogenization of remaining biodiversity in fragmented tropical forests across agricultural landscapes

The increasing worldwide interest on the conservation of tropical forests reflects the conversion of over 50% of their area into agricultural lands and other uses. Understanding the distribution of remaining biodiversity across agricultural landscapes is an essential task to guide future conservation strategies. To understand the long-term effects of fragmentation on biodiversity, we investigated whether forest fragments in southeastern Brazil are under a taxonomic homogenization or heterogenization process. We estimated pre-deforestation species richness and composition based on a Species Distribution Modelling approach, and compared them to the observed patterns of - and {beta}-diversity. In particular, we asked (i) if changes in {beta}-diversity reveal convergence or divergence on species composition; (ii) if these changes are similar between forest fragments in Strictly Protected Areas (SPAs) (n=20) and within private lands (n=367) and in different regions of the state (West, Center, and Southeast). We detected steep reductions in observed local species richness in relation to our modeled predictions, and this was particularly true among forest fragments in non-protected private lands. The higher observed {beta} diversity indicated an overall biotic heterogenization process, consistent with the idea that the originally diverse vegetation is now reduced to small and isolated patches, with unique disturbance histories and impoverished communities derived from a large regional species pool. Since conservation of biodiversity extends beyond the boundaries of strictly Protected Areas, we advocate forest fragments are valuable for conservation in agricultural landscapes, with particular relevance for private lands, which represent the most exposed and neglected share of what is left.

ecology↗

bioRxiv2019

Community size affects the signals of selection and ecological drift on biodiversity

Ecological drift can override the effects of deterministic niche selection on small populations and drive the assembly of small communities. We tested the hypothesis that smaller local communities are more dissimilar among each other because of ecological drift than larger communities, which are mainly structured by niche selection. We used a unique, comprehensive dataset on insect communities sampled identically in a total of 200 streams in climatically different regions (Brazil and Finland) that differ in community size by fivefold. Null models allowed us to estimate the magnitude to which beta diversity deviates from the expectation under a random assembly process while taking differences in species richness and relative abundance into account, i.e., beta deviation. Beta diversity of small tropical communities was consistently higher but closer to null expectations than {beta}-diversity of large communities. However, although {beta}-deviation and community size were strongly related in both regions, the direction of the relationship varied according to dissimilarity metrics. While incidence-based {beta}-diversity was lower than expected (communities were less dissimilar than null expectations) and negatively related to community size in Brazil, abundance-based {beta}-diversity was higher than expected (communities were more dissimilar than null expectations) and positively related to community size in both regions. We suggest that ecological drift drives variation in small communities by increasing the chances of species with low abundance and narrow distribution to occur within the metacommunity. Also, while weak niche selection and high dispersal rates likely reduced variation in community structure among large tropical streams, niche selection was likely sufficient to cause non-random variations in the relative abundances of genera among large communities in both regions. Habitat destruction, overexploitation, pollution, and reductions in connectivity have been reducing the size of biological communities. These environmental pressures will make smaller communities more vulnerable to novel conditions and render community dynamics more unpredictable, as random demographic processes should prevail under these conditions. Incorporation of community size into ecological models should provide conceptual, empirical and applied insights into a better understanding of the processes driving changes in biodiversity.

ecology↗

bioRxiv2018

Towards an applied metaecology

The complexity of ecological systems is a major challenge for practitioners and decision-makers who work to avoid, mitigate and manage environmental change. Here, we illustrate how metaecology - the study of spatial interdependencies among ecological systems through fluxes of organisms, energy, and matter - can enhance understanding and improve managing environmental change at multiple spatial scales. We present several case studies illustrating how the framework has leveraged decision-making in conservation, restoration and risk management. Nevertheless, an explicit incorporation of metaecology is still uncommon in the applied ecology literature, and in action guidelines addressing environmental change. This is unfortunate because the many facets of environmental change can be framed as modifying spatial context, connectedness and dominant regulating processes - the defining features of metaecological systems. Narrowing the gap between theory and practice will require incorporating system-specific realism in otherwise predominantly conceptual studies, as well as deliberately studying scenarios of environmental change.

ecology↗