arXiv subjects

Rafael Rubio de Casas

Publications and source records attributed to Rafael Rubio de Casas.

4 recordsLinked to original sources

arXiv2026

Fluctuating Environments Favor Extreme Reproductive Delays and Penalize Intermediate Ones

The timing of reproduction is crucial for biological fitness. Reproductive delays carry an inherent demographic cost: an individual that takes longer to reproduce contributes later to population growth, a priori, without any compensating benefit. However, natural selection favors delayed reproduction under certain environmental conditions, a phenomenon that remains poorly understood. Here, we investigate how the environment can determine the evolution of particular life histories using a parsimonious delayed-logistic model. Individuals become reproductive only after a fixed lag whereas birth rates fluctuate under temporally correlated stochasticity. Numerical integration, analytical calculations and evolutionary simulations reveal that the joint effect of demographic memory and colored multiplicative noise generate a strongly nonmonotonic dependence of fitness on life history, with three distinct regimes of population performance: rapid reproduction maximizes linear growth but amplifies fluctuations and extinction risk; delayed reproduction buffers environmental variability, substantially increasing mean extinction times despite slower growth; strikingly, and central to our results, there is a broad band of maladaptive intermediate life histories that simultaneously reduce both growth and persistence, an effect that arises generically from the mismatch between reproductive timing and environmental autocorrelation. Our results show that reproductive timing is not merely a life-history parameter but an adaptive mechanism tuned to environmental time scales, and that "dangerous middle" maturation times can be inherently disfavored, with implications for understanding reproductive strategies across the tree of life.

q-bio.PE↗

arXiv2025

A biological hydraulic accumulator: How the squirting cucumber, Ecballium elaterium, squirts its seeds

Seed dispersal is a fundamental process that allows offspring to reach suitable habitats and colonize new environments. While most plants rely on external vectors, some have evolved mechanisms that employ the buildup of liquid pressure in a closed compartment and its explosive release to disperse their seeds. This form of energy storage, reinvented by humans for engineering applications, is termed a hydraulic accumulator. Here we investigated the fluid mechanics involved in dispersal in the squirting cucumber, Ecballium elaterium integrating high-speed videography (up to 10 000 fps), microtomography, and internal pressure sensors. We recorded long-term pressure time series showing that E. elaterium exhibits circadian (24 hour) and ultradian (short-period) rhythms. Remarkably, the measurements revealed a lack of correlation between fruit and stem turgor; while the stem showed strong circadian cycles, the fruit often did not, suggesting isolated physiological processes in different tissues. The fruit's spongy wall tissue stores elastic potential energy as turgor pressure builds to nearly one atmosphere (92-99 kPa). Upon detachment, this energy is rapidly released to expel a turbulent, particle-laden liquid jet. Microtomography revealed that the seeds are packed around a central funiculus, a configuration that optimizes their exit through the basal orifice at velocities of up to 30 m/s. Seeds eventually move faster than the liquid droplets during the later stages of ejection as they shed their liquid coating. This sophisticated mechanism ensures a broad dispersal cone, effectively spreading offspring across space and environmental conditions.

physics.bio-ph↗

arXiv2018

Eco-evolutionary Model of Rapid Phenotypic Diversification in Species-Rich Communities

Evolutionary and ecosystem dynamics are often treated as different processes --operating at separate timescales-- even if evidence reveals that rapid evolutionary changes can feed back into ecological interactions. A recent long-term field experiment has explicitly shown that communities of competing plant species can experience very fast phenotypic diversification, and that this gives rise to enhanced complementarity in resource exploitation and to enlarged ecosystem-level productivity. Here, we build on progress made in recent years in the integration of eco-evolutionary dynamics, and present a computational approach aimed at describing these empirical findings in detail. In particular we model a community of organisms of different but similar species evolving in time through mechanisms of birth, competition, sexual reproduction, descent with modification, and death. Based on simple rules, this model provides a rationalization for the emergence of rapid phenotypic diversification in species-rich communities. Furthermore, it also leads to non-trivial predictions about long-term phenotypic change and ecological interactions. Our results illustrate that the presence of highly specialized, non-competing species leads to very stable communities and reveals that phenotypically equivalent species occupying the same niche may emerge and coexist for very long times. Thus, the framework presented here provides a simple approach --complementing existing theories, but specifically devised to account for the specificities of the recent empirical findings for plant communities-- to explain the collective emergence of diversification at a community level, and paves the way to further scrutinize the intimate entanglement of ecological and evolutionary processes, especially in species-rich communities.

q-bio.PE↗

arXiv2015

Environmental unpredictability and inbreeding depression select for mixed dispersal syndromes

Mixed dispersal syndromes have historically been regarded as bet-hedging mechanisms that enhance survival in unpredictable environments, ensuring that some propagules stay in the maternal environment while others can potentially colonize new sites. However, this entails paying the costs of both dispersal and non-dispersal. Propagules that disperse are likely to encounter unfavorable conditions for establishment, while non-dispersing propagules might form populations of close relatives burdened with inbreeding. Here, we investigate the conditions under which mixed dispersal syndromes emerge and are evolutionarily stable, taking into account the risks of both environmental unpredictability and inbreeding. Using mathematical and computational modeling we show that high dispersal propensity is favored whenever temporal environmental unpredictability is low and inbreeding depression high, whereas mixed dispersal syndromes are adaptive under conditions of high environmental unpredictability, but more particularly if also inbreeding depression is small. Although pure dispersers can be selected for under some circumstances, mixed dispersal provides the optimal strategy under most parameterizations of our models, indicating that this strategy is likely to be favored under a wide variety of conditions. Furthermore, populations exhibiting any single phenotype go inevitably extinct when environmental and genetic costs are high, whilst mixed strategies can maintain viable populations even under such conditions. Our models support the hypothesis that the interplay between inbreeding depression and environmental unpredictability shapes dispersal syndromes, often resulting in mixed strategies. Moreover, mixed dispersal seems to facilitate persistence whenever conditions are critical or nearly critical for survival.

q-bio.PE↗