bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2024.01.17.575986

Estimation of Uncertainty and Location-specific Variation in Regional Food Web Interactions

Brothers, A. M.·Santillan, V.·Quitian, M.·Neuschultz, E. L.·Schleuning, M.·Böhning-Gaese, K.·Llamoza, O. A.·Thron, C.
View original source ↗Export metadata ↓

Abstract

Food-web interactions are commonly aggregated across sampling locations and represented by a single interaction strength for an entire region. This practice implicitly treats interaction strengths as fixed regional constants, even though ecological interactions may vary substantially among locations because of local environmental conditions, species abundances, and habitat structure. We argue that food-web interaction strengths should instead be viewed as spatially distributed latent variables whose regional distributions must be inferred from observations collected at a limited number of sites. To estimate this spatial variation, we develop a Bayesian framework based on transect observations from multiple locations within a region. Species-species interaction measurements at each location are modeled as Poisson random variables whose means are proportional to local interaction strengths. Preliminary analyses suggest that location-dependent interaction strengths may be simply approximated by a uniform distribution on an interval. Under this assumption, we estimate the endpoints of the interval and thereby characterize both the mean interaction strength and its spatial variability. For the case of three sampling locations, we derive graphical representations of the resulting estimates and their uncertainties. Among other results, we show that the average of three observed interaction frequencies systematically underestimates the true regional mean interaction strength under the uniform-distribution model. We apply the framework to avian frugivore-plant interaction data collected at three locations within each of six regions in Ecuador. The estimated distributions of interaction strength are used to test the hypothesis that species within the same genus spatially substitute for one another. The results do not support this hypothesis. Instead, species within the same genus tend to exhibit elevated interaction strengths in the same locations, indicating positive spatial association rather than substitution. We also find evidence that habitat fragmentation may reduce within-region variability in bird-plant interactions even when species diversity is maintained. These results suggest that explicitly modeling spatial variation can reveal ecological patterns that are obscured by conventional food-web representations.

Explore related subjects

ecologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Brothers, A. M., Santillan, V., Quitian, M., Neuschultz, E. L., Schleuning, M., Böhning-Gaese, K., Llamoza, O. A., Thron, C.. 2024-01-20. Estimation of Uncertainty and Location-specific Variation in Regional Food Web Interactions. https://doi.org/10.1101/2024.01.17.575986

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Ecological opportunity and evolutionary relatedness predict parasite sharing differently across mammalian taxonomic scales

As global change brings species into new contact, understanding the ecological and evolutionary drivers of parasite sharing is essential for anticipating and mitigating disease emergence. Yet, the relative importance of geographic proximity and evolutionary relatedness among host species in predicting parasite sharing remains unresolved. We tested whether their relative importance changes across host taxonomic scale using 30,310 recorded associations between 680 mammalian and 11,107 parasite species. Geography accounted for 86.6% importance within genera, declining to 44.7% across all mammals, shifting toward evolutionary relatedness predominating. Parasite sharing increased nonlinearly with geographic proximity and host relatedness, and the overall trend varied among parasite types. Notably, accounting for host taxonomic scale improved parasite-sharing prediction accuracy. To explore the consequences of biotic homogenization, we applied a counterfactual scenario of reducing geographic distance by 99%, which increased mean predicted parasite sharing to 13.71% within genera and 1.50% at the class level. Together, these findings suggest that ecological opportunity is especially consequential among close relatives whereas evolutionary similarity is increasingly important among geographically distant species. Accounting for evolutionary scale can therefore improve sharing predictions and help identify which new host encounters warrant surveillance for cross-species transmission and disease emergence.

ecology↗
bioRxiv2026

Host availability, climate and pupal-stage ecology shape the predicted environmental suitability of the New World screwworm across Central and South America

Background: The New World screwworm, Cochliomyia hominivorax, causes primary myiasis in warm-blooded vertebrates. Its recent resurgence in Central America has renewed the need for spatial tools that identify environmentally suitable areas and surveillance gaps. Most previous distribution models have emphasized climate and livestock, whereas ecological constraints acting during the free-living pupal stage have rarely been incorporated. Methods: We compiled 2,461 georeferenced occurrence reports from the literature across Central and South America and linked them to climate, livestock density, forest cover and superficial soil predictors. Four sequential (nested) logistic models quantified the incremental contribution of predictor blocks, compared using likelihood-ratio tests, AIC and discrimination metrics. Logistic regression and Random Forest were then compared using five-fold spatial block cross-validation, which we treat as the primary measure of generalisation, and an independent municipality-level 70:30 train-test split. Variable importance was assessed using Random Forest Mean Decrease Accuracy together with partial-dependence profiles. Because presence and pseudo-absence classes were balanced before fitting, model outputs are interpreted as relative environmental suitability rather than absolute probability of occurrence. Results: The literature database represented 2,589 infected hosts, dominated by cattle, pigs, dogs and humans. Across the sequential models, AUC increased from 0.780 for climate alone to 0.898 with livestock density, 0.908 with forest cover and 0.918 with superficial soil properties; the increment attributable to the soil block ({Delta}AUC = 0.010) was smaller than the between-fold variability observed under spatial cross-validation (SD 0.049) and is therefore reported as suggestive rather than established. Sheep and horse density and cold-quarter soil temperature showed the highest Mean Decrease Accuracy values, while silt texture ranked above cattle density and forest cover. Under spatial block cross-validation Random Forest was markedly more stable than the GLM (mean AUC 0.926 {+/-} 0.049 versus 0.814 {+/-} 0.157) and was retained as the final model. On the independent municipality-level test set it achieved AUC 0.981, TSS 0.824, sensitivity 0.850 and specificity 0.972, values we regard as optimistic relative to the spatially blocked estimates. Predicted suitability was highest across Central America and parts of northern and tropical South America. Conclusions: C. hominivorax occurrence was associated with interacting climatic, host and landscape conditions. Superficial soil variables added a small, biologically interpretable signal consistent with constraints acting during pupation, but one that lies within the uncertainty of our spatial validation and requires confirmation with independent data. The maps estimate relative environmental suitability rather than infection incidence, and are intended to identify areas where surveillance could be strengthened rather than to guide control operations directly.

ecology↗
bioRxiv2026

Phenotypic variation in divergent mitochondrial haplotypes in migratory three-spined stickleback

Mitochondria are essential components in life-sustaining organismal processes. The mitochondrial genome can be influenced by selection, and divergent mitochondrial haplotypes have substantial potential to affect interspecies variation in life-history and physiology, yet little is known about whole organism phenotypic changes that might accompany mitochondrial genomic divergence. Three-spined stickleback on the Scottish island of North Uist provide a model to study this as their populations exhibit a well-mixed nuclear genome, yet two highly diverged mitochondrial haplotypes ( trans-Atlantic and European). Three-spined stickleback were sampled from six lochs to investigate associations between mitochondrial haplotype and phenotypic traits including organ size, body size, and ovule volume/clutch size, as well as citrate synthase enzyme activity. Results showed that mitochondrial haplotype has an influence on male gonadosomatic index (GSI) and potentially citrate synthase (CS) enzyme activity. Differences in male GSI may be explained by the timing of male spermatogenesis or potentially a need for larger testes in European haplotype fish. While no other phenotypic trait showed differences between mitochondrial haplotypes, there were many differences between sexes and populations e.g. in body size and organ/muscle size.

ecology↗