Biology subjects

Kotrschal, A.

Publications and source records attributed to Kotrschal, A..

9 recordsLinked to original sources

bioRxiv2024

Artificial selection for adult predation survival impacts life history and morphology in guppies (Poecilia reticulata)

Predation is accepted as a major evolutionary driver of life history and morphology. However, whether these traits evolve directly via predation or via indirect effects is largely unresolved. We used artificial selection over three generations to experimentally test the impact of adult predation on the evolution of life history and morphology in guppies (Poecilia reticulata). We found that, compared to control fish, predation-selected fish produced larger offspring and larger broods early in life. However, other life history parameters, such as interbrood interval and total number of offspring, showed no response. We also found that predation-selected for smaller and lighter females and for shorter tails and gonopodia in males, with no effect on body colouration. Our results show that while several traits evolve fast under selection on adult predation, several classic predation-dependent traits seem unaffected by predation selection. By comparing our experimental results to those from natural populations we can disentangle the contribution of direct and indirect effects on trait evolution under predation pressure.

evolutionary biology↗

bioRxiv2023

Functional convergence of genomic and transcriptomic genetic architecture underlying sociability in a live-bearing fish

The organization and coordination of fish schools provide a valuable model to investigate the genetic architecture of affiliative behaviors and dissect the mechanisms underlying social behaviors and personalities. We used quantitative genetic methods in replicate guppy selection lines that vary in schooling propensity to investigate the genetic basis of sociability phenotypes. Alignment and attraction, the two major traits forming the sociability personality axis in this species, showed heritability estimates at the upper end of the range previously described for social behaviors, with important variation across sexes. Consistent with findings in collective motion patterns, experimental evolution of schooling propensity increases the sociability of female, but not male, guppies when swimming with unfamiliar conspecifics, a highly relevant trait in a species with fission-fusion social systems in natural populations. Our results from PoolSeq and RNASeq convergently identify genes involved in neuron migration and synaptic function, highlighting a crucial role of glutamatergic synaptic function and calcium-dependent signaling processes in the evolution of schooling.

evolutionary biology↗

bioRxiv2022

Lionfish Pterois volitans can see UV light: UV Vision in an Invasive Aquatic Predator

UV vision is wide-spread across animals. Many coral reef fish species use the reflection of UV light to communicate with conspecifics, as most aquatic predators are UV-blind. This creates a "secret" communication system for prey fish to signal to others while minimizing their risk of predation. Exploitation of this system by a predator that can see UV light would likely help facilitate prey detection and increase predator efficiency. Recently, indirect evidence has emerged that the Indo-Pacific lionfish (Pterois volitans), a highly invasive predator in the Caribbean, might be able to see into the UV spectrum. We propose that UV vision might be an important, and so far overlooked, reason for lionfishs predatory success. Using an associative learning assay, we investigated lionfishs ability to discriminate UV from non-UV light and found the first behavioral evidence that lionfish can indeed see UV light. We also measured the UV body reflectance of lionfish and found that lionfish reflect UV light, suggesting that lionfish may communicate with conspecifics via UV vision. Further studies should investigate if the UV vision is more widespread in marine predators than originally thought, as well as continue to investigate the function of UV vision in lionfish and other predators.

animal behavior and cognition↗

bioRxiv2022

Evolution of schooling propensity in the guppy drives changes in anti-predator behavior that are linked to neuroanatomy

One of the most spectacular displays of social behavior is the synchronized movements that many animal groups perform to travel, forage and escape from predators. However, elucidating the neural mechanisms underlying the evolution of collective behaviors, as well as their fitness effects, remains challenging. Here, we study anti-predator behavior in guppies experimentally selected for divergence in polarization, an important behavioral aspect of coordinated movement. We find that groups from artificially selected lines remain more polarized than control groups in the presence of a threat. Neuroanatomical measurements of polarization-selected individuals indicated changes in brain regions previously suggested to be important regulators of perception, fear and attention, and motor response. Additional visual acuity and temporal resolution tests performed in polarization-selected and control individuals indicate that observed differences in anti-predator and schooling behavior should not be attributable to changes in visual perception, but rather are more likely the result of the more efficient relay of sensory input in the brain of polarization-selected fish. Our findings highlight that brain morphology may play a fundamental role in the evolution of coordinated movement and anti-predator behavior.

evolutionary biology↗

bioRxiv2022

Jumping out of trouble: Evidence for a cognitive map in guppies (Poecilia reticulata)

Spatial cognitive abilities allow individuals to remember the location of food patches, predator hide-outs, or shelters. Animals typically incorporate learnt spatial information or use external environmental cues to navigate their surroundings. A spectacular example of how some fishes move is through aerial jumping. For instance, fish that are trapped within isolated pools, cut off from the main body of water during dry periods, may jump over obstacles and direct their jumps to return to safe locations. However, what information such re-orientation behaviour during jumping is based on remains enigmatic. Here we combine a lab and field experiment to test if guppies (Poecilia reticulata) incorporate learnt spatial information and external environmental cues (visual and auditory) to determine where to jump. In a spatial memory assay we found that guppies were more likely to jump towards deeper areas, hence incorporating past spatial information to jump to safety. In a matched vs. mismatched spatial cue experiment in the field, we found that animals only showed directed jumping when visual and auditory cues matched. We show that in unfamiliar entrapments guppies direct their jumps by combining visual and auditory cues, while in familiar entrapments they use a cognitive map. We hence conclude that jumping behaviour is a goal-directed behaviour, guided by different sources of information and involving important spatial cognitive skills.

animal behavior and cognition↗

bioRxiv2021

Rapid mosaic brain evolution under artificial selection for relative telencephalon size in the guppy (Poecilia reticulata)

The vertebrate brain displays enormous morphological variation and the quest to understand the evolutionary causes and consequences of this variation has spurred much research. The mosaic brain evolution hypothesis, stating that brain regions can evolve relatively independently, is an important idea in this research field. Here we provide experimental support for this hypothesis through an artificial selection experiment in the guppy (Poecilia reticulata). After four generations of selection on relative telencephalon volume (relative to brain size) in replicated up-selected, down-selected and control-lines, we found substantial changes in telencephalon size, but no changes in other regions. Comparisons revealed that up-selected lines had larger telencephalon while down-selected lines had smaller telencephalon than wild Trinidadian populations. No cost of increasing telencephalon size was detected in offspring production. Our results support that independent evolutionary changes in specific brain regions through mosaic brain evolution can be important facilitators of cognitive evolution.

evolutionary biology↗

bioRxiv2020

Where are they now? Tracking the Mediterranean Lionfish Invasion via Local Dive Centers

Invasive species are globally on the rise due to human-induced environmental change and are often a source of harm to their new ecosystems. Tracking the spread of invaders is crucial to better management of invasive species, and citizen science is often used to collect sighting data. However, this can be unreliable due to the general publics limited expertise for accurate identification and a lack of clear absence data. Here, we introduce a refined method of citizen science by tracking the spread of the invasive lionfish (Pterois miles) in the Mediterranean Sea using dive centers expertise on local marine wildlife. We contacted 1131 dive centers on the Mediterranean coast via email and received 216 responses reporting whether or not lionfish were present in their area and, if present, the year they were first sighted. Currently, lionfish sightings are observed in the eastern half of the Mediterranean, though the front is continuing to move west with the furthest sighting as far as Corfu, Greece (19.939423{degrees}E, 39.428017{degrees}N). In 2020, lionfish also expanded their invasive range north on the Turkish Aegean coast to Karaburun (26.520657{degrees}E, 38.637033{degrees}N), showing that the invasion is ongoing. We found that the invasive range is now exceeding previous invasion models, highlighting the need for additional research on lionfish biology to inform management efforts. Continuous monitoring of invasive fronts based on dive center reports and a better understanding of what makes lionfish so invasive is crucial to mitigating their negative impact on native ecosystems.

ecology↗

bioRxiv2020

Rapid evolution of coordinated and collective movement in response to artificial selection

Collective motion occurs when individuals use social interaction rules to respond to the movements and positions of their neighbors. How readily these social decisions are shaped by selection remains unknown. Through artificial selection on fish (guppies, Poecilia reticulata) for increased social coordination (group polarization), we demonstrate that social interaction rules can evolve remarkably fast. Within just three generations, groups of polarization selected females showed a 15% increase in polarization, coupled with increased cohesiveness, compared to fish from control lines. They did not differ in physical swimming ability or exploratory behavior. However, polarization selected fish adopted faster speeds, particularly in social contexts, and showed stronger alignment and attraction responses to multiple neighbors. Our results demonstrate that animals social interactions can rapidly evolve under strong selection, and reveal which social interaction rules change when collective behavior evolves.

animal behavior and cognition↗

bioRxiv2018

Revisiting the social brain hypothesis: contest duration depends on loser’s brain size

BackgroundBrain size is expected to evolve by a balance between cognitive benefits and energetic costs. Several influential hypotheses have suggested that large brains may be especially beneficial in social contexts. Group living and competition may pose unique cognitive challenges to individuals and favor the evolution of increased cognitive ability. Evidence comes from comparative studies on the link between social complexity and brain morphology, but the strength of empirical support has recently been challenged. In addition, the behavioral mechanisms that would link cognitive ability to sociality are rarely studied. Here we take an alternative approach and investigate experimentally how brain size can relate to the social competence of individuals within species, a problem that so far has remained unresolved. We use the unique guppy brain size selection line model system to evaluate whether large brains are advantageous by allowing individuals to better assess their performance in a social contest situation. Based on theoretical literature, we predict that contest duration should depend on the brain size of the loser, as it is the capitulation of the losing individual that ends the fight.\n\nResultsFirst, we show that studying the movement of competitors during contests allows for precise estimation of the dominance timeline in guppies, even when overt aggression is typically one-sided and delayed. Second, we staged contests between pairs of male that had been artificially selected for large and small relative brain size, with demonstrated differences in cognitive ability. We show that dominance was established much earlier in contests with large-brained losers, whereas the brain size of the winner had no effect. Following our prediction, large-brained individuals gave up more quickly when they were going to lose.\n\nConclusionsThese results suggest that large-brained individuals assess their performance in contests better and that social competence indeed can depend on brain size. Conflict resolution may therefore be an important behavioral mechanism behind macro-evolutionary patterns between sociality and brain size. Since conflict is ubiquitous among group-living animals, the possible effects of the social environment on the evolution of cognition may be more broadly applicable than previously thought.

animal behavior and cognition↗