Biology subjects

Arim, M.

Publications and source records attributed to Arim, M..

5 recordsLinked to original sources

bioRxiv2026

The interaction of dispersal, species sorting, and priority effects, explains a unimodal response of β-diversity to immigration rates

A dominant perspective in metacommunity theory is that dispersal consistently homogenizes species composition across local communities. However, recent studies have reported a direct relationship between dispersal rate and {beta}-diversity, which has been attributed to the influence of priority effects and species sorting. The underlying mechanisms by which dispersal can either increase or decrease {beta}-diversity remain unclear, hindering our understanding of metacommunity assembly and the processes driving biodiversity patterns across time and space. We theoretically evaluated how purely random priority effects, priority effects conditioned by species dispersal abilities, and species sorting shape the {beta}-diversity-dispersal relationship in metacommunities open to exogenous dispersal (i.e., immigration) from a regional species pool. Our results show that the three evaluated processes foster community differentiation at intermediate exogenous dispersal rates when dispersal between communities (i.e. endogenous dispersal) is taking place. Additionally, the interaction between endogenous and exogenous dispersal homogenizes communities at low and high exogenous dispersal rates, determining a unimodal response of {beta}-diversity to increasing exogenous dispersal rates. Our findings contribute to a deeper mechanistic understanding of metacommunity assembly and offer a coherent explanation for previously observed empirical discrepancies, thereby challenging the traditional view of dispersal as a purely homogenizing process.

ecology↗

bioRxiv2024

Similar Won't Make It: Coexistence, Habitat Availability and Suboptimal Restoration

In the context of the looming biodiversity crisis, adding patches of habitat has been proposed as a restoration strategy in several ecosystems. However, these interventions rarely mimic the conditions of the natural habitats precisely. Consequently, not all species equally benefit from the restored habitat, fostering a difference in species fitness that could generate an imbalance in the equalizing and stabilizing mechanisms that enable species coexistence, leading to competitive exclusion. Using a metapopulation model, we explore how the introduction of habitat patches with biased fitness advantages affects species coexistence. We show that while adding habitat patches generally increases species occupancy, suboptimal patches can favor one species, disrupting the stabilizing and equalizing mechanisms that enable coexistence, leading to competitive exclusion. This impact on the coexistence regime is particularly pronounced in species with high niche overlap and high colonization-extinction ratios. Our results highlight the double-edged sword effect of suboptimal restoration, revealing potential unintended consequences that could exacerbate biodiversity loss. On the other hand, restoration favoring endangered species is also identified as a conservation tool. The present study advances in the mechanistic comprehension of habitat restoration, a necessary endeavor in the face of the challenges posed by global change.

ecology↗

bioRxiv2024

Food web structure mediate positive and negative effects of diversity on ecosystem functioning in a large floodplain river

Research programs on Biodiversity-Ecosystem Functioning (BEF) and Food Web Structure (FWS) have contributed to understanding the impact of biodiversity on the functioning and architecture of ecosystems, but the interconnectedness between these components was seldom attended until recently. Several theoretical hypotheses predict an interconnection between BEF and FWS but were poorly and independently evaluated. We estimated 63 sink food webs of predatory fish in the Parana River, covering a large gradient of community richness. We evaluated available hypotheses and their interrelationship through path analyses. A well-supported causal structure was identified, supporting that species richness directly increased standing biomass, modularity, and intermodular connection, whereas decreased interaction strength, connectance, and nestedness. A direct positive effect of modularity and connectance on biomass indicates that FWS can determine the BEF. Richness promotes biomass directly and through the increase in modularity but can also decrease biomass due to the decay in connectance, with similar positive and negative effects of richness on biomass. In this sense, the relationship between diversity and ecosystem functioning cannot be blind to FWS. Environmental homogenization and reduction in functional diversity may undermine the conditions for modular food webs, switching positive BEF to negative ones with potential cascading effects in the whole ecosystem.

ecology↗

bioRxiv2024

Fall of giants: European diversity resistance to waterscape degradation and its potential continental drivers

Aquatic landscapes, or waterscapes, face severe threats from human activities propelling their deterioration. Waterscape degradation represents a main driver of the current diversity crisis, although its long-term consequences are difficult to quantify. In addition, the understanding of the potential effects of waterscape degradation on biodiversity at large spatial scales, such as biomes and continents, remains limited. In this work, we explore the potential trends in diversity decay in response to waterscape degradation across Europe to provide a first answer to these main threads. We reconstructed the European waterscape based on available satellite data and simulated diversity patterns using a coalescent metacommunity model run for several European ecoregions and considering nine dispersal abilities. Subsequently, we generated a gradient of waterscape degradation by systematically removing a percentage of available habitat and recalculating diversity metrics. For each ecoregion, dispersal ability, and degradation level we obtained a theoretical gamma diversity value. We synthesized the captured diversity decay trends in two parameters: the proportional decay rate and the collapsing rate, which respectively inform about the speed of diversity loss and its acceleration as waterscape degradation progresses. Finally, we mapped these parameters across Europe and related them with ecoregion structural descriptors (i.e. geographic location, water cover, connectivity, and size). Through this exercise, we could identify ecoregions sensitivities and their continental variation based on their diversity decay parameters. Connectivity and water cover emerged as primary descriptors of diversity decay, with more heterogeneous ecoregions generally exhibiting greater resistance to waterscape degradation. Our study provides a first order approximation to an urgently needed information: the continental-scale consequences of waterscape degradation for biodiversity. This data has the potential to improve conservation practices and facilitate the integration of innovative approaches in management, thereby enhancing our understanding of the consequences posed by one of the principal threats to freshwater diversity.

ecology↗

bioRxiv2017

The network structure of cancer ecosystems

Ever since Pagets seed-and-soil and Ewings connectivity hypotheses to explain tumor metastasis (1,2), it has become clear that cancer progression can be envisaged as an ecological phenomenon. This connection has flourished during the past two decades (3-7), giving rise to important insights into the ecology and evolution of cancer progression, with therapeutic implications (8-10). Here, we take a metapopulation view of metastasis (i.e. the migration to and colonization of, habitat patches) and represent it as a bipartite network, distinguishing source patches, or organs that host a primary tumor, and acceptor patches, or organs colonized ultimately from the source through metastasis. Using 20,326, biomedical records obtained from literature, we show that: (i) the network structure of cancer ecosystems is non-random, exhibiting a nested subset pattern as has been found both in the distribution of species across islands and island-like habitats (11-13), and in the distribution of among species interactions across different ecological networks (14-16); (ii) similar to ecological networks, there is a heterogeneous distribution of degree (i.e., number of connections associated with a source or acceptor organ); (iii) there is a significant correlation between metastatic incidence (or the frequency with which tumor cells from a source organ colonize an acceptor one) and arterial blood supply, suggesting that more irrigated organs have a higher probability of developing metastasis or being invaded; (iv) there is a positive correlation between metastatic incidence and acceptor organ degree (or number of different tumor-bearing source organs that generate metastasis in a given acceptor organ), and a negative one between acceptor organ degree and number of stem cell divisions, implying that there are preferred sink organs for metastasis and that this could be related to average acceptor organ cell longevity; (v) there is a negative association between organ cell turnover and source organ degree, implying that organs with rapid cell turnovers tend to generate more metastasis, a process akin to the phenomenon of propagule pressure in ecology (17); and (vi) the cancer ecosystem network exhibits a modular structure in both source and acceptor patches, suggesting that some of them share more connections among themselves than with the rest of the network. We show that both niche-related processes occurring at the organ level as well as spatial connectivity and propagule pressure contribute to metastaticspread and result in a non-random cancer network, which exhibits a truncated power law degree distribution, clustering and a nested subset structure. The similarity between the cancer network and ecological networks highlights the importance of ecological approaches in increasing our understanding of patterns in cancer incidence and dynamics, which may lead to new strategies to control tumor spread within the human ecosystem.

ecology↗