Biology subjects

Yitbarek, S.

Publications and source records attributed to Yitbarek, S..

6 recordsLinked to original sources

bioRxiv2025

Temporal dimensions of a microbial invader in a plant-microbiome feedback model

Plant-soil feedback (PSF) theory leverages the increasingly recognized ecological significance of microbiomes to provide insight into plant coexistence. However, PSF theory generally assumes that microbiomes have static composition and properties. In reality, plant communities are thought to commonly experience microbial colonization. Here, we use a PSF model to study microbial invasions of a community of two plant species and their associated microbiomes. We manipulate initial plant and microbiome evenness, microbial colonization timing, and properties of all actors, then record resulting community membership. Invasion success is higher during transient dynamics than when approaching equilibrium. Furthermore, stability analysis of a set of communities shows that invasion success is determined by the effects of the plants and the invader on each others growth rates. When successful, microbial invaders commonly disrupt plant coexistence. Our study demonstrates a promising framework for understanding biodiversity dynamics via integration of host-microbiome dynamics, dispersal, and time-dependent interactions.

ecology↗

bioRxiv2021

Spatiotemporal patterns of urban mosquitoes are modulated by socioeconomic status and environmental traits in the United States

The distribution of mosquitoes and associated vector diseases (e.g., West Nile, dengue, and Zika viruses) is likely a function of environmental conditions in the landscape. Urban environments are highly heterogeneous in the amount of vegetation, standing water, and concrete structures covering the land at a given time, each having the capacity to influence mosquito abundance and disease transmission. Previous research suggests that socioeconomic status is correlated with the ecology of the landscape, with lower-income neighborhoods generally having more concrete structures and standing water via residential abandonment, garbage dumps, and inadequate sewage. Whether these socio-ecological factors affect mosquito distributions across urban environments in the United States (US) remains unclear. Here, we present a meta-analysis of 22 paired observations from 15 articles testing how socioeconomic status relates to overall mosquito burden in urban landscapes in the United States. We then analyzed a comprehensive dataset from a socioeconomic gradient in Baltimore, Maryland to model spatiotemporal patterns of Aedes albopictus using a spatial regression model with socio-ecological covariates. The meta-analysis revealed that lower-income neighborhoods (regions making less than $50,000 per year on average) are exposed to 151% greater mosquito densities and mosquito-borne illnesses compared to higher-income neighborhoods ([≥]$50,000 per year). Two species of mosquito (Ae. albopictus and Aedes aegypti) showed the strongest relationship with socioeconomic status, with Ae. albopictus and Ae. aegypti being 62% and 22% higher in low-income neighborhoods, respectively. In the spatial regression analysis in Baltimore, we found that Ae. albopictus spatial spread of 1.2 km per year was significantly associated with median household income, vegetation cover, tree density, and abandoned buildings. Specifically, Ae. albopictus abundance was negatively correlated with median household income, vegetation cover, and tree density. Ae. albopictus abundance and the cover of abandoned buildings were positively correlated. Together, these results indicate that socio-ecological interactions can lead to disproportionate impacts of mosquitoes on humans in urban landscapes. Thus, concerted efforts to manage mosquito populations in low-income urban neighborhoods are required to reduce mosquito burden for the communities most vulnerable to human disease.

ecology↗

bioRxiv2019

Deconstructing higher-order interactions in the microbiota: A theoretical examination

O_LIA major objective of microbial ecology is to identify how the composition of gut microbial taxa shapes host phenotypes. However, most studies focus solely on community-level patterns and pairwise interactions and ignore the potentially significant effects of higher-order interactions involving three or more component taxa. C_LIO_LIStudies on higher-order interactions among microbial taxa are scarce for many reasons, including experimental intractability, daunting diversity and complexity of many microbial systems, and the potential confounding role of the environment. Moreover, we still lack the empirical and statistical tools to isolate and understand the role of higher-order interactions on the host. C_LIO_LIHere, we apply a mathematical approach to quantifying the effects of higher-order interactions among taxa on host infection risk. To do so, we adapt the Hadamard-Walsh method recently used in evolutionary genetics to quantify the nonlinear effects of mutations on fitness. We apply our approach to an in silico dataset built to resemble a population of insect hosts with gut-associated microbial communities at risk of infection from an intestinal parasite. Critically, we examine these interactions across a breadth of environmental contexts, using nutrient content of the insect diet as a model for context. C_LIO_LIWe find that the effect of higher-order interactions is considerable and can change appreciably across environmental contexts. Strikingly, the relative eminence of different orders (pairwise vs. third order, fourth order, and fifth order) changes as a function of environmental context. Furthermore, we show-in our theoretical microcosm-that higher-order interactions can stabilize community structure thereby reducing host susceptibility to parasite invasion. C_LIO_LIOur approach illustrates how incorporating the effects of higher-order interactions among gut microbiota across environments can be essential for understanding their effects on host phenotypes. We conclude that higher-order interactions among taxa can profoundly shape important organismal phenotypes, and they deserve greater attention in host-associated microbiome studies. C_LI

ecology↗

bioRxiv2018

Tropical arboreal ants form dominance hierarchies over nesting resources in agroecosystems

Interspecific dominance hierarchies have been widely reported across animal systems. While some dominant individuals (winners) get to monopolize resources, during dyadic interactions, they can increase their relative fitness as compared to subdominant individuals (losers). In some ant species, dominance hierarchies have been used to explain species coexistence and community structure. However, it remains unclear whether or in what contexts dominance hierarchies occur in tropical ant communities. Furthermore, it can be challenging to infer and quantify reliable dominance hierarchies from observed interactions. This study seeks to examine whether arboreal twig-nesting ants competing for nesting resources in a Mexican coffee agricultural ecosystem are arranged in a dominance hierarchy. Using network analysis, we quantified interactions between ten species by measuring the uncertainty and steepness in the dominance hierarchy. We also assessed the orderliness of the hierarchy by considering species interactions at the network level. Based on the Elo-ranking method, we found that the twig-nesting ant species Myrmelachista mexicana ranked highest in the ranking, while Pseudomyrmex ejectus was ranked as the lowest in the hierarchy. We quantified the uncertainty in the dominance hierarchy and found that the hierarchy was intermediate in its steepness, suggesting that the probability of higher ranked individuals winning contests against lower ranked individuals was fairly high. Motif analysis and significant excess of triads further revealed that the species networks were largely transitive. This study highlights that some tropical arboreal ant communities self-organize into dominance hierarchies.

ecology↗

bioRxiv2017

Competitive release from native range does not predict invasive success of a globally dominant exotic ant species

A major goal of invasion biology is to understand under what conditions exotic species thrive in the introduced range. High competitive abilities are thought to be an important characteristic of exotic species. Most invasion studies focus on the competitive ability of exotic species in the introduced range and attribute their ecological success to competitive release, but fewer studies have compared the relative competitive differences within the native range. These comparative studies are important in order to determine if competitive abilities of exotic species are strong predictors of invasion success. The little fire ant Wasmmnia auropunctata is a highly invasive species that has spread from its original range (Central and South America) to becoming a globally distributed exotic species in recent decades. It is generally accepted that island ecosystems offer weak biotic resistance to exotic species as compared to their native range. Here, we examined this empirically by comparing the relative competitive difference of W. auropunctata and locally dominant ants, between its native range of Mexico and introduced range of Puerto Rico. Resource competition was assessed between W. auropunctata and native ants under field conditions and in the laboratory. Furthermore, we compared resource competition at different temporal intervals ranging from short-term (< 2 hours) to long-term (14-days) dynamics. Our results are in contrast to common invasion predictions on island communities because we show that native species were resistant to W. auropunctata in its introduced range of Puerto Rico. We observed that the ground-foraging ant Solenopsis invicta competitive displaced W. auropunctata in Puerto Rico during short-term experiments. Meanwhile, the native arboreal ant Linepithema iniquum withstood competitive pressure from W. auropunctata. In the native range of Mexico, W. auropunctata was superior against Solenopsis Picea and Pheidole protensa species, but was outcompeted by dominant ants Solenopsis geminata and Pheidole synanthropica. This study challenges the relative importance of competitive ability in predicting invasion success. This is one of the few detailed comparative studies that examines exotic species performance between native and introduced habitats.

ecology↗

bioRxiv2017

Parasite mediated competition facilitates invasion

Parasites play an important role in invasion success with important consequences for biodiversity and community structure. While much research has focused on direct effects of parasites on biological invasions, parasites can also indirectly influence interactions within the invaded community across trophic levels. For instance, parasites can mediate competitive interactions between native and exotic species through trait-mediated indirect effects. We consider the interactions between the parasitoid fly Pseudacteon sp. (Diptera: Phoridae), and its native host ant Linipethema iniquum, and the exotic ant Wasmannia auropunctata in the introduced range of Puerto Rico. We examined the effects of phorid flies on the competitive outcome between the arboreal ants W. auropunctata and native ant L. iniquum. Furthermore, we investigate the searching efficiency of phorid flies in detecting L. iniquum nests. To study the indirect effects on ant competition, we monitored ant recruitment to baits over a 60-min time interval in the presence and absence of phorid fly parasitoids. We then performed field experiments and measured phorid arrival time to arboreal nests of L. iniquum located in both a) W. auropunctata patches and in b) isolated patches dominated by L. iniquum nests. We found that the presence of phorid fly significantly reduced recruitment of L. iniquum workers to baits through induced behavioral changes thereby increasing the ability of W. auropunctata to acquire resources. In addition, we found that phorid arrival time in isolated patches of L. iniquum patches was faster as compared to L. iniquum nests located within W. auropunctata patches. Our results show that phorid fly parasitoids indirectly may influence competitive interactions by attacking the host-ant L. iniquum and consequently providing an advantage to local spread of W. auropuntata populations in Puerto Rico. However, the spatial dynamics of arboreal ants shows that L. iniquum seeks protection from phorid fly parasotoids by moving their nests to W. auropunctata dominated patches.

ecology↗