Biology subjects

Ehlman, S. M.

Publications and source records attributed to Ehlman, S. M..

4 recordsLinked to original sources

bioRxiv2026

Activity during the first days of life predicts lifespan in a naturally clonal vertebrate

Lifespan varies widely among individuals, yet the extent to which such variation persists when genetic and environmental differences are minimized remains unclear. Here we quantify such stochastic lifespan variation in a naturally clonal vertebrate and test whether and how this variation is linked to early-life behavioral individuality. We followed N = 33 genetically identical Amazon mollies (Poecilia formosa), separated on day 1 of their life into highly standardized environments, from birth to death. Despite genetic uniformity and environmental standardization, lifespan varies markedly, spanning 502 - 826 days. Continuous high-resolution behavioral tracking during the first four weeks of life reveals that seemingly stochastic early-life activity differences explain 32.5% of this variation. Higher activity predicts shorter lifespan during the first two weeks, but as activity levels and among-individual variation in activity decline over early development, a U-shaped relationship emerges, with both low- and high-activity individuals outliving those with intermediate activity. These findings show that signatures of lifespan emerge within days of birth, even among genetically identical individuals, highlighting developmental stochasticity and early-life contingencies as major contributors to variation in life-history outcomes.

animal behavior and cognition↗

bioRxiv2025

No paternal effects in a sperm-dependent, naturally clonal fish

Paternal effects, i.e., effects of males on the phenotypes of their offspring that are not caused by the integration of male genetic material, are increasingly recognized as a potentially significant source of phenotypic variation across taxa - even in the absence of paternal care. Gynogenetic systems, which rely on sperm to trigger embryogenesis without incorporating male genetic material, provide a powerful way to experimentally isolate potential paternal effects from effects caused by the integration of male genetic material; up to now, however, paternal effects remain largely unexplored in these systems. Here, we test for paternal effects in the gynogenetic Amazon molly (Poecilia formosa): a naturally clonal, all-female species with no parental care. Using a highly controlled breeding experiment involving 59 Atlantic molly males (P. mexicana) and 57 Amazon molly females, we generated 169 broods and 2,966 offspring. While males were drawn from a naturally variable stock population, females - next to being genetically identical - were highly standardized for age, size, descent, and developmental experience. We asked whether male identity or body size predicted offspring size - a key offspring phenotypic trait. We also asked whether male identity or body size predicted brood size. While we found substantial variation in both offspring size and brood size, we found no evidence for paternal effects on either trait. Next to providing an experimental test for paternal effects in a gynogenetic system, our results also strengthen the Amazon mollys status as a model species for studying - in a highly controlled fashion - the developmental emergence of phenotypic variation.

animal behavior and cognition↗

bioRxiv2023

Developmental arcs of plasticity in whole movement repertoires of a clonal fish

Developmental plasticity at the behavioral repertoire level allows animals to incrementally adjust their behavioral phenotypes to match their environments through ontogeny, serving as a lynchpin between ecological factors that cue phenotypic adjustments and evolutionary forces that select upon emergent phenotypic variation. Quantifying the continuous arcs of plasticity throughout animals development, however, has often been prohibitively challenging. Here, we leverage recent advancements in high-resolution behavioral tracking and analysis to (i) track the behavior of 45 genetically identical fish clones (Poecilia formosa) reared in near-identical environments during their first four weeks of life at 0.2 s resolution and (ii) quantify the continuous arcs of plasticity across entire behavioral repertoires through development. Doing so, we are able to test one of the most fundamental theoretical predictions from Bayesian models of development that in stable (but initially unknown) environments, behavioral plasticity should gradually decrease from a maximum at the beginning of life. Using two approaches to measure plasticity across ontogeny, we first quantify plasticity in individual behavioral metrics before also developing a novel whole-repertoire approach that calculates plasticity as the degree of behavioral entropy across a multi-dimensional behavioral phenotype space. We robustly find - despite experimentally matching as best as possible the assumptions of models that predict decreasing plasticity - a [~]two-week initial increase in plasticity in movement behaviors before plasticity subsequently decreased. Our results challenge a common intuition about the optimal developmental course of plasticity through early ontogeny, thereby also demonstrating the value of long-term behavioral tracking approaches for testing fundamental predictions on phenotypic development. Significance statementBehavioral plasticity across development may help animals adjust to uncertainty in moderately unpredictable environments. In stable environments, developing animals should gradually decrease this uncertainty through ontogeny, becoming less sensitive to incoming information (and thus less behaviorally plastic) as they age. This intuitive expectation of old dog inflexibility to new tricks, however, has not been adequately tested with the long-term, highresolution datasets that would be ideal. Here, we achieve such a test and emphasize the significance of this study in (1) providing a novel method for quantifying multi-dimensional behavioral plasticity continuously across long-term, high-resolution behavioral timeseries and in (2) testing fundamental theory that links the temporal patterning of environmental conditions to evolved patterns of behavioral plasticity across development.

animal behavior and cognition↗

bioRxiv2023

Perceived predation risk affects the development of among-individual behavioral variation in a naturally clonal freshwater fish

Predation risk is a key driver of natural selection, influencing various aspects of prey behavior. While many studies focus on how predation risk affects average behavior at population level, less attention has been given to its potential impact on behavioral variation within prey populations. Here, we investigate the effect of perceived predation risk on among-individual behavioral variation in naturally clonal Amazon mollies. Juveniles were raised in two groups: one exposed to a predator during feeding (visual cues only) and the other one serving as a control group. We observed activity and feeding behavior (time spent feeding, visits to feeding spot) over a four-week period. (I) Individuals in the predator-exposed group were on average less active but there was no difference in average feeding behavior between the two groups, suggesting individuals strategically respond to threats based on behavior-specific cost-benefit trade-offs. (II) Among-individual behavioral variation was affected by perceived predation risk: in the absence of the predator, individuals developed pronounced differences in the time spent feeding while no such development was observed in the predator-exposed group. This result has the potential of affecting a wide range of fitness-relevant intraspecific interactions if lower among-individual feeding variation translate into reduced sizes differences. The presence of the predator initially reduced among-individual variation in activity and visits to the feeding spot, but these differences did not persist over time. Our findings highlight the importance of considering both population-level and individual-level responses to predation risk for a more comprehensive understanding of its ecological and evolutionary consequences.

animal behavior and cognition↗