Biology subjects

Laskowski, K.

Publications and source records attributed to Laskowski, K..

4 recordsLinked to original sources

bioRxiv2026

Ancestral gene flow shaped the singular origin of the Amazon molly

The evolutionary origins of asexuality remain poorly understood, despite extensive research on its ecological and evolutionary consequences. Asexuality often arises through hybridization between species with intermediate genomic divergence, implying that hybrid-induced asexuality may be partly repeatable. The Amazon molly (Poecilia formosa), the first asexual vertebrate known to science, challenges this view: repeated experimental crosses between its extant parental species have failed to recreate a stable Amazon molly-like lineage. This apparent paradox gave rise to the Rare Formation Hypothesis, which proposes that stable asexuality requires an exceptionally specific genomic combination. Here, we combine experimental crosses, molecular cytogenetics, and population genomics to test whether ancestral introgression before the hybrid speciation event set the stage for the singular origin of the Amazon molly. We show that most experimental hybrids are viable but sexual, but that a subset of F1 hybrids produce unreduced eggs through a mechanism distinct from that of the Amazon molly. Population genomic analyses reveal that introgression between parental species likely predated the formation of the Amazon molly, and shared homozygous tracts across Amazon molly genomes support inheritance from admixed progenitors. Together, our findings reconcile the repeatable and contingent views of the origin of asexuality, suggesting that ancestral introgression may be the missing mechanism assembling the rare genomic combinations required for seemingly unrepeatable evolutionary innovations, including the emergence of asexual species.

evolutionary biology↗

bioRxiv2026

Group-level phenotypes are idiosyncratic yet unpredictable over development in a clonal fish

Behavioral differences among groups can have profound impacts on individual fitness, yet how group-level phenotypes arise and change during development is poorly understood. Group-level differences may originate from genetic differences or subtle variation among individuals, but they can also emerge over time through social feedback mechanisms within and between groups, potentially producing dramatically different group-level behavior. Disentangling these drivers of group phenotypes is challenging because groups are typically studied after they are already well established. Using the naturally clonal Amazon molly, we establish replicate groups of genetically identical individuals and continuously track group-level behavior from birth throughout the first 55 days of life. This design allows us to control for genetic and environmental sources of variance, thereby establishing a null baseline for group-level differences. Furthermore, by recording over an extended period beginning from day 1 of life, we test whether group phenotypes follow predictable trajectories driven by individual differences or instead diverge due to social feedback during development. We find that average behavioral changes across groups follow predictable patterns during this early developmental phase. In contrast, differences among groups are highly unstable over longer timescales: although groups differ from very early in life, it appears that the rank-order of group-level phenotypes undergoes a shuffling mid-development, around 4-5 weeks of age. These results suggest that distinct processes generate group-level variation across ontogeny, with early differences largely reflecting consistent individual variation; then as individuals mature and become more socially responsive, social feedbacks push groups along divergent, less predictable behavioral trajectories.

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↗

bioRxiv2023

Bayesian updating for self-assessment explains social dominance and the winner effect

In animal contests, winners of previous contests often keep winning and losers keep losing. This coupling of previous experiences to future success, referred to as the winner-loser effect, plays a key role in stabilizing the resulting dominance hierarchies. Despite their importance, the cognitive mechanisms through which these effects occur are unknown. Identifying the mechanisms behind winner-loser effects requires identifying plausible models and generating predictions that can be used to test these alternative hypotheses. Winner-loser effects are often accompanied by a change in the aggressiveness of experienced individuals, which suggests individuals may be adjusting their self-assessment of their abilities after each contest. This updating of a prior estimate can be effectively described by Bayesian updating, and here we implement an agent-based model with continuous Bayesian updating to explore whether this is a plausible explanation of winner-loser effects. We first show that Bayesian updating reproduces known empirical results of typical dominance interactions. We then provide a series of testable predictions that can be used in future empirical work to distinguish Bayesian updating from simpler mechanisms. Our work demonstrates the utility of Bayesian updating as a mechanism to explain and ultimately predict changes in behaviour after salient social experiences.

animal behavior and cognition↗