Biology subjects

Strang, A.

Publications and source records attributed to Strang, A..

4 recordsLinked to original sources

bioRxiv2026

Conservation rescued the Mauritius kestrel from extinction but not from genomic erosion

Conservation can prevent species extinction via demographic recovery, yet it remains debated whether this translates into genomic recovery and restored fitness. The Mauritius kestrel (Falco punctatus) declined to four known wild birds in 1974 before intensive management recovered the population. Using 130 genomes spanning nearly 200 years, lifetime reproductive success data, and simulations, we reconstructed genomic change across the species collapse and recovery. Long-term small population size had already removed some harmful variation before the crash, a process expected to buffer populations from severe inbreeding depression. Yet the recent bottleneck sharply increased inbreeding, exposed additional harmful variants, and left a signature of genomic erosion associated with reduced reproductive success. The long conservation history of the Mauritius kestrel shows how population collapse and recovery can leave a compounding genetic threat, in which partial genetic purging, continuing genomic erosion, and conservation dependence unfold together in rescued species.

evolutionary biology↗

bioRxiv2026

Emergent feasibility in random ecological systems with higher-order interactions

A recurring lesson from random ecological models is that coexistence is hard to come by: in the Generalized Lotka-Volterra (GLV) model with pairwise interactions, the probability that randomly sampled parameters admit a positive (feasible) equilibrium - a necessary condition for coexistence - is exactly 1/2n in n species, vanishing rapidly with diversity. This rarity is often read as evidence that coexistence demands specific ecological mechanisms. Real interactions, however, are rarely strictly pairwise: any nonlinear dependence of one species growth rate on anothers abundance, Taylor-expanded, generates higher-order interactions (HOIs) of increasing degree. Treating the interaction order d as a knob that indexes this nonlinearity, we map the random GLV with HOIs onto the Kostlan-Shub-Smale class of random polynomial systems and approximate the probability of feasibility (Pf ) analytically. We find a phase transition at d = 4: below this threshold, Pf decays with diversity as in the pairwise case; above it, the exponential proliferation of equilibria outpaces the probability that any given equilibrium is feasible, and the probability of feasibility increases with n, approaching one. The transition appears to be universal across symmetric coefficient distributions, but vanishes when sign symmetry of the parameter distribution is broken. This work uncovers a route by which feasibility emerges from nonlinearity alone, with no fine-tuning of parameters and no appeal to specific ecological mechanisms.

ecology↗

bioRxiv2022

Noise source importance in linear stochastic models of biological systems that grow, shrink, wander, or persist

While noise is an important factor in biology, biological processes often involve multiple noise sources, whose relative importance can be unclear. Here we develop tools that quantify the importance of noise sources in a network based on their contributions to variability in a quantity of interest. We generalize the edge importance measures proposed by Schmidt and Thomas [1] for first-order reaction networks whose steady-state variance is a linear combination of variance produced by each directed edge. We show that the same additive property extends to a general family of stochastic processes subject to a set of linearity assumptions, whether in discrete or continuous state or time. Our analysis applies to both expanding and contracting populations, as well as populations obeying a martingale ("wandering") at long times. We show that the original Schmidt-Thomas edge importance measure is a special case of our more general measure, and is recovered when the model satisfies a conservation constraint ("persists"). In the growing and wandering cases we show that the choice of observables (measurements) used to monitor the process does not influence which noise sources are important at long times. In contrast, in the shrinking or persisting case, which noise sources are important depends on what is measured. We also generalize our measures to admit models with affine moment update equations, which admit additional limiting scenarios, and arise naturally after linearization. We illustrate our results using examples from cell biology and ecology: (i) a model for the dynamics of the inositol trisphospate receptor, (ii) a model for an endangered population of white-tailed eagles, and (iii) a model for wood frog dispersal. Author summaryBiological processes are frequently subject to an ensemble of independent noise sources. Noise sources produce fluctuations that propagate through the system, driving fluctuations in quantities of interest such as population size or ion channel configuration. We introduce a measure that quantifies how much variability each noise source contributes to any given quantity of interest. Using these methods, we identify which binding events contribute significantly to fluctuations in the state of a molecular signalling channel, which life history events contribute the most variability to an eagle population before and after a successful conservation effort rescued the population from the brink of extinction, and which dispersal events, at what times, matter most to variability in the recolonization of a series of ponds by wood frogs after a drought.

ecology↗

bioRxiv2018

Immune profiling of cord blood after prolonged rupture of membranes.

We hypothesised that foetal immune responses to an infectious challenge may be detected by genome-wide transcriptional profiling of cord blood. In order to test this hypothesis, we sought to identify transcriptomic changes in post-natal cord blood samples following prolonged pre-labour rupture of membranes (PROM) as a surrogate for increased risk of infection. By comparison to controls we found increased levels of blood transcripts in a subset of prolonged PROM cases, significantly enriched for innate immune system signalling pathways. These changes were idiosyncratic, suggesting qualitative and quantitative variation in foetal immune responses which may reflect differences in exposure and/or in host genetics. Our data support the view that PROM represents an infection risk to the foetus. In addition, we propose that cord blood transcriptional profiling offers exciting opportunities to identify immune correlates of clinical outcome following potential in utero exposures to infection. These may be used to elucidate the mechanisms of immunological protection and pathology in the foetus and identify biomarkers to stratify the risk of adverse outcomes.

immunology↗