Schedule
Poster 1: A unifying framework for microbial-mediated invasion
Presented by: Maria Martignoni
Microbial-mediated invasion is an emerging science that aims to account for the role of microbial agents in facilitating or preventing biological invasion. Progress has been made in identifying possible scenarios occurring when microbes can transmit either from native to invasive (‘symbiont spillback’) or from invasive to native (‘symbiont spillover’). For example, the presence of pre-existing mycorrhizal networks in the soil may facilitate plant invasion, and invaders are more likely to be successful if native species are infected with parasites co-introduced with their invasive hosts. However, a unifying theoretical framework to contextualize these individual scenarios and explore the consequences of microbial sharing between hosts along a continuum of beneficial to harmful host-microbial interactions is lacking. Here, we present and analyse such a framework. We discuss interesting scenarios emerging from our analysis, such as the possibility that co-invasion may be observed if the spillover of less beneficial symbionts (that exploit native host resources at low cost) increases the fitness of invasive microbes and their hosts, or that invasion can be prevented if symbiont spillback leads to an increase in the abundance of native hosts. Our framework helps us gain intuition about the possible dynamics of host invasion, microbial invasion, or co-invasion observed when a certain interactive structure is in place, and about the possible consequences of microbial sharing for native host-microbial communities.
Poster 2: The genetic consequences of fragmentation on population networks
Presented by: Ohad Peled
The last few decades have seen increased climate change and anthropogenic activity. These processes lead to the destruction and fragmentation of natural habitats, constituting a major risk for the persistence of wild populations. Habitat fragmentation, in general, increases genetic differentiation between populations and decreases the genetic diversity within populations, leading to reduction in fitness and evolutionary potential. Previous models of the effect of fragmentation on the genetic composition of populations have typically considered a simple and uniform between-population connectivity pattern. However, real-world connectivity patterns may be complex and are often better represented as networks. To address this, we have integrated network theory with mathematical formulations from population genetics theory to simulate population networks going through three types of fragmentation processes: (a) random fragmentation, (b) fragmentation in which edges are removed in a correlated sequence, and (c) fragmentation simulating a decrease in migration distance. For each fragmentation step, we determine the genetic diversity of each population and the genetic differentiation between all population pairs. To better understand the role of the network topology and relate it to real-world populations, we analyze three types of networks: Erdos-Renyi random networks as a null model, random geometric graphs to model distance-dependent migration, and small-world networks. Our framework, which allows for a cohesive assessment of the genetic consequences of fragmentation as well as monitoring of critical points during the fragmentation process, can facilitate and inform wildlife management.
Poster 3: Genetic Diversity and Eco-evolutionary Feedbacks: Bridging Theory from Genes to Ecosystems
Presented by: Miguel Roman
The mechanics of microevolution pervade across biological scales, impacting processes in ecosystems and coevolution. In this study, we bridge theory from genes to ecosystems through a pioneering framework for polygenic adaptation in traits with ecological functions. The preliminary results highlight the importance of preserving genetic diversity by describing how the genetic architecture of populations echoes the dynamics and stability of entire communities.
Poster 4: Structured bipartite networks generation and null models
Presented by: Javier Borge-Holthoefer
The use of null models has been a cornerstone to assess the emergence of many network properties at different levels of organization (micro-, meso- or macroscales). Notwithstanding, the debate around which is the most appropriate null model for a given problem is far from being over. Within the ecological community, for example, the discussion around whether nestedness is -or not- ubiquitous in natural systems, and under which assumptions, remains open. Yet, efforts have been devoted to exploring to what extent current models are vulnerable to statistical errors or to introduce new models that employ different randomization procedures. Here, we attempt to show that assessing several descriptors under a single model may produce ambiguous results, which difficult the comparison regarding the joint emergence of different arrangements within a single network. To this aim, we analyze the statistical significance for nestedness, modularity and in-block nestedness, with three different null models for a set of ~10k synthetic bipartite networks with varying levels of nestedness. We show that, in some scenarios, this approach can consistently over-or underestimate the presence of significant structural patterns. In light of these ambiguities, we introduce an alternative model that helps to reduce the observed under- and overestimation and highlight the need for the development of new frameworks that take into account those biases.
Poster 5: Grow now, pay later: when should a bacterium go into debt?
Presented by: Amir Erez
Microbes adapt their growth to fluctuating environments. We introduce the concept of “growth debt”, where microbes grow rapidly initially, paying later with slower growth or heightened mortality. Despite the prevalence of such trade-offs, their understanding remains limited in the context of serial-dilution cultures. In this study, we first examine a classical chemostat experiment, validating our proposed dynamics and revealing that Escherichia coli regulates its stress resistance dynamically. Extending the chemostat theory to include serial-dilution cultures, we derive phase diagrams for the persistence of “debtor” microbes. We find that debtors cannot coexist with non-debtors if “payment” is increased mortality but can coexist if it lowers enzyme affinity. Surprisingly, weak noise considerably extends the persistence of resistance elements, pertinent for antibiotic management. Our microbial debt theory, broadly applicable across systems, bridges the gap between prevalent chemostat and serial dilution cultures.
Poster 6: Eigenvalue spectra of Finely Structured Random Matrices: The Niche and Cascade Models
Presented by: Lyle Poley
The eigenvalue spectra of large random matrices provide insights into the stability of complex ecosystems using only a summary knowledge of the statistics of inter-species interactions. For example, results such as the well-known elliptic law have played a key role in connecting interspecies interaction with ecosystem stability. However, such universal results often assume that all species are statistically equivalent. Here, we remove this assumption by introducing the concept of a finely-structured random matrix, where the statistics of the elements depend on the location within the matrix, thereby allowing each species to be statistically distinct. Treating the fine-structure (the amount by which species are different) as a perturbation to the elliptic law, we find a universal `modified` elliptic law. As with the elliptic law, our modified elliptic law only depends on the macro statistics of interspecies interactions in the community. We demonstrate the direct applicability of our finely structured matrix results by applying them to two models in theoretical ecology, namely the Cascade and Niche models. For the Cascade model, we present formulae for the exact support of the bulk spectrum (known previously) and outlier eigenvalues (a new result). For the Niche model, we show how our modified elliptic law gives simple approximate formulae for the bulk and outliers. These examples demonstrate that our modified elliptic law allows us to draw broad conclusions about the effect of fine-structure on stability, transparently and analytically.
Poster 7: Unveiling the role of bats and birds in rice pest control: A case study in Guinea-Bissau`s rice paddies
Presented by: Patrícia Chaves
Rice serves as a staple food for billions of people worldwide, and Africa accounts for about 4% of the global rice production area. Integrated pest management is crucial in African rice production, which is predominantly subsistence-based. This study aimed to evaluate the pest suppression potential of bats and birds in rice paddies in West Africa. Using DNA metabarcoding, we examined the diet of these two taxa through the analysis of faecal pellets collected from animals captured in seven rice fields In Oio (Guinea-Bissau) between 2021 and 2022. Our findings revealed that 34 predator species, including 18 bat and 16 bird species, preyed upon 155 insect families. Using a network approach, we observed a low diversity of interactions, indicating a low connectance. The network exhibited a nested pattern and low modularity, with five modules identified, three of which comprised exclusively bats. Bats, particularly Sctotophilus sp. and Hipposideros sp., exhibited a higher degree and interaction strength compared to birds. Among birds, Euplectes franciscanus and Ispidina picta exhibited the highest degree and strength, respectively, albeit lower than that of bats. Furthermore, we identified insect families that include pests, such as Cydnidae, Acrididae, Gryllidae, Curculionidae, Delphacidae, and Pyralidae, in the diet of the predators. This study underscores the potential of bats and birds as natural pest suppressors in rice fields. By understanding their dietary preferences and ecological roles, we can implement targeted measures to conserve these predator species and enhance their contributions to sustainable rice production and pest management.
Poster 8: Universal scaling of robustness of ecosystem services to species loss
Presented by: Samuel Ross
Ensuring reliable supply of services from nature is key to the sustainable development and well-being of human societies. Varied and frequently complex relationships between biodiversity and ecosystem services have, however, frustrated our capacity to quantify and predict the vulnerability of those services to species extinctions. Here, we use a qualitative Boolean modelling framework to identify universal drivers of the robustness of ecosystem service supply to species loss. These drivers comprise simple features of the networks that link species to the functions they perform that, in turn, underpin a service. Together, they define what we call network fragility. Using data from 250 real ecological networks representing services such as pollination and seed-dispersal, we demonstrate that network fragility predicts remarkably well the robustness of empirical ecosystem services. We then show how to quantify contributions of individual species to ecosystem service robustness, enabling quantification of how vulnerability scales from species to services. Our findings provide general insights into the way species, functional traits, and the links between them together determine the vulnerability of ecosystem service supply to biodiversity loss.
Poster 9: Genetic contribution of Asiatic wild ass males in response to changes in water-source distribution in the Negev highlands
Presented by: Noa Yaffa Kan
Genetic diversity is a leading concern in conservation biology due to both its short and long-term implications for species sustainability. Small populations of polygynous species are particularly susceptible to genetic diversity loss because of the limited number of breeding males that contribute to the gene pool. In territorial polygyny, in which males gain reproductive advantage by defending valuable resources, such as food and water. This effect may be stronger when resources are scarce. We estimated the change in breeding males’ genetic contribution in the Asiatic wild ass (Equus hemionus) population in the Negev highlands, following active water-source management. This management was implemented by the Israel Nature and Parks Authority to increase water availability in the range of the Asiatic wild ass that has a strong polygynous mating system. We hypothesized that as territorial males tend to establish their territories next to water sources to increase mating opportunities, increasing the number of permanent water sources in the Negev would result in increased numbers of territorial males contributing to the population`s gene pool. We established a methodological system to infer genotypes, using hundreds of single nucleotide polymorphisms (SNPs) with a non-invasive sampling approach, to detect relatedness among individuals at a high resolution. Parentage analyses revealed that the number of contributing males increased following the increase in the number of available water sources. Moreover, the geographic locations of breeding males supported a spatial shift in their home ranges toward the new water sources. These findings accord with our research hypothesis. This, in turn, may increase the variance effective size of the population, which is important for the population long term persistence.
Poster 10: Global change increases the rate of forbidden links due to phenological uncoupling: integrating empirical data and simulation models
Presented by: Irene Mendoza
A forbidden link in an interaction network is defined as a missing link that is not due to inefficient sampling but rather constrained by other factors such as a mismatch in size. One of the most common types of forbidden links is due to phenological uncoupling, i.e. when potentially interacting partners are not coincident on time, resulting in the inability to interact. Biotic seed dispersal necessarily implies an overlap in the timing of fruiting plants and animals feeding on them, i.e. their phenologies. Despite the obvious connection between phenology and seed dispersal, our understanding of how future global change scenarios will impact ecological interactions by disrupting activity overlap remains limited. This study aims to analyze the prevalence of phenological uncoupling over short and long temporal scales by combining empirical observations on seed dispersal by frugivorous birds with simulations under different global-change scenarios. Our empirical data come from a Mediterranean lowland scrubland in SW Spain (Hato Ratón, Doñana Natural Area). Bird censuses and phenological transects were performed to estimate the abundance of birds and fruits in 1981-1983 and repeated later in 2019-2023, and we also captured species interactions by collecting bird feces. We developed three different models simulating phenological changes, altering either the timing or duration of phenophases. The results highlight increased rates of forbidden links over extended temporal spans, with a doubling in the rate of phenological uncoupling observed in recent monitoring. Furthermore, the simulated scenarios demonstrated a greater impact of phenological uncoupling when changes affected the duration of phenophases rather than the timing. Our findings underscore the vulnerability of mutualistic interactions to phenological shifts induced by global change and emphasize the importance of considering empirical missing links in the theory of ecological networks.
Poster 11: Competitive interactions between culturable bacteria are highly non-additive
Presented by: Amichai Baichman-Kass
Microorganisms are found in diverse communities whose structure and function are determined by interspecific interactions. Just as single species seldom exist in isolation, communities as a whole are also constantly challenged and affected by external species. Though much work has been done on characterizing how individual species affect each other through pairwise interactions, the joint effects of multiple species on a single (focal) species remain underexplored. As such, it is still unclear how single-species effects combine to a community-level effect on a species of interest. To explore this relationship, we assayed thousands of communities of two, three, and four bacterial species, measuring the effect of single, pairs of, and trios of 61 affecting species on six different focal species. We found that when multiple species each have a negative effect on a focal species, their joint effect is typically not given by the sum of the effects of individual affecting species. Rather, they are dominated by the strongest individual-species effect. Therefore, while joint effects of multiple species are often non-additive, they can still be derived from the effects of individual species, making it plausible to map complex interaction networks based on pairwise measurements. This finding is important for understanding the fate of species introduced into an occupied environment and is relevant for applications in medicine and agriculture, such as probiotics and biocontrol agents, as well as for ecological questions surrounding migrating and invasive species.
Poster 12: Vocal networks in the Arabian babbler (Turdoides squamiceps)
Presented by: Marie Guggenberger
Vocal communication in social animals can be essential for various purposes, including cooperation, group cohesion, decision-making, parent-offspring interactions, predation, and the regulation of social interactions. Acoustic signals, which can be perceived by a larger number of individuals than the intended receiver, are of particular interest in studying communication networks. Acoustic signals can transmit information about the sender, such as group membership, sex, rank or age. The Arabian babbler (Argya squamiceps) is a cooperative breeder that can form family or complex groups arranged in a hierarchical system. This research focuses on vocal networks in Arabian babblers during snake mobbing interactions, employing an acoustic camera and on-board sound recorders. Snake mobbing involves the birds forming a circle around the predator and emitting mobbing calls while hopping around the snake. Furthermore, other vocal interaction networks are examined by tagging entire groups of babblers and employing on-board sound recorders. Preliminary results indicate that juveniles of Arabian Babblers gradually join the vocal network, leading to changes in the network structure of the observed groups over time. Historically, vocal networks in wild animals have received limited research attention due to technological constraints. This research aims to enhance our understanding of vocal networks in group living wild animals.