Biology subjects

van Schaik, C.

Publications and source records attributed to van Schaik, C..

8 recordsLinked to original sources

bioRxiv2026

Interspecific adaptations in root system architecture define host tolerance of Arabidopsis to biotic stresses by root feeding nematodes

Belowground, plants are exposed to a wide range of biotic stresses that vary in severity and nature, including tissue damage, disruption of vascular connectivity, and depletion of assimilates. How plants adapt their root systems to cope with different types of belowground biotic stresses is not well known. In this paper we compare above- and belowground plant adaptations to three nematode species with distinct tissue migration and feeding behaviours to study mechanisms underlying tolerance to different types of biotic stresses. We monitored both green canopy growth and changes in root system architecture of Arabidopsis inoculated with Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita. This revealed three distinct phases in aboveground plant responses: (i) initial growth inhibition associated with host invasion and tissue damage, (ii) persistent growth reduction associated with nematode sedentarism, and (iii) late growth stimulus in more advanced stages of infection. Specific adaptations in the root systems further revealed fundamentally different stress coping strategies. Tissue damage and intermittent feeding by P. penetrans in the root cortex did not induce significant changes in root system architecture. Tissue damage to the root cortex and prolonged feeding on host vascular cells by H. schachtii induced secondary root formation compensating for primary root growth inhibition. Prolonged feeding on host vascular cell by M. incognita alone did not induce secondary root formation, but was accompanied by typical local tissue swelling instead. Our data suggest that local secondary root formation and tissue swelling are two distinct compensatory mechanisms underlying tolerance to sedentarism by root-feeding nematodes. HighlightHow plants utilize root system plasticity to cope with different types of biotic stresses by root feeding nematodes remains largely unknown. Here, we report on specific adaptive growth responses in Arabidopsis roots to three nematode species, Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita, with fundamentally different strategies for host invasion, subsequent migration through host tissue, and feeding on host cells.

plant biology↗

bioRxiv2025

Leadership under risk: male vervet monkey's roles in group progression across high-risk terrain

The evolution of cooperative behaviour among unrelated individuals is still incompletely understood. One example is the reported service provisioning by males in primate societies, which is difficult to explain by traditional reciprocity-based models. In this study, we investigated group progressions and sex roles in wild vervet monkeys (Chlorocebus pygerythrus) to test two hypotheses for the observed male bias in cooperative and protective behaviours: paternal care versus reputation-based partner choice. Over more than two years, we recorded the order and timing of individual progressions in five neighbouring groups of vervet monkeys across two terrain types differing in risk (rivers and roads). Males, particularly dominant males, were more likely to lead than females or juveniles, and their probability of leading increased in high-risk terrain. When leading, males often crossed alone, thereby assuming higher predation risk, whereas when not leading, males usually crossed within subgroups. Dominant males who had no offspring yet were most likely to lead during risky progressions. Males who did not lead did not preferentially cross with infants based on their paternal status, refuting the paternal care hypothesis. Instead, male leadership in risky contexts appears to represent a cooperative service. While some of these findings are consistent with the reputation-based partner choice model, we found no clear evidence that such services translated into direct mating advantages. Overall, our results highlight the role of dominance and reproductive status in shaping male service provisioning and underscore its potential adaptable function in primate social organisation.

evolutionary biology↗

bioRxiv2025

Patchy distribution of potato cyst nematodes within single arable fields reveals local disease suppressiveness mediated by disparate microbialcommunities

Disease suppressiveness is a complex phenomenon that is assumed to be the resultant of actions of local microbial antagonists in soil environments. Exploitation of disease suppressiveness as a tool to manage pathogens is hindered by our poor understanding of this phenomenon. Here we investigated soil microbiome-based suppression of potato cyst nematodes (PCN), and, to this end, four apparently homogeneous potato fields with an unexplained non-homogeneous PCN distribution were selected. We hypothesized that this patchy PCN distribution resulted from local variation in disease suppressiveness. Under controlled greenhouse conditions, we confirmed the suppressiveness of these soils vis-a-vis PCN and soils were gamma-irradiated to corroborate the biotic origin of this suppression. Subsequent DNA-based analysis of the microbial community in the potato rhizosphere revealed suppressiveness-related contrasts in community composition between suppressive and conducive patches. Elevated abundances of fungal (e.g., Metacordyceps chlamydosporia) and bacterial (e.g., Pseudomonas fluorescens) nematode antagonists were positively correlated with PCN suppressive patches. Distinct sets of antagonists were found to be associated with PCN suppression despite of the geographical closeness of the locations under investigation. Our findings confirm the biotic origin of local PCN suppressiveness and reveal that it should be regarded as a superficially similar resultant of a biologically diverse phenomenon.

ecology↗

bioRxiv2025

Making friends in an asymmetric game: the establishment of male-female grooming exchanges in vervet monkeys

An important challenge for individuals of group-living species is to build cooperative relationships with new partners. One famous strategy for doing so is "raise-the-stakes", proposing low initial investments that increase if the partner matches these investments in a series of exchanges. Contrarily, the "all-in" strategy predicts high initial investment that may be maintained, but downregulated if not fully matched. We tested these predictions on grooming exchanges between wild male-female vervet monkeys, a species with regular male dispersal. Contrary to model predictions, we found uneven initial investment between novel partners that reached near reciprocity after approximately six months. To identify which sex altered investment, we examined grooming durations and frequencies of novel and established partners. Females showed consistently high initial investment and gradually reduced grooming over the first six months. Males did not alter grooming duration but had higher grooming frequency after a year of residency. Eventually, grooming exchanges nearly evened out. Female behaviour aligns more closely with the "all-in" strategy, which suggests competition among female groups over dispersing males. Male behaviour partly fits the "raise-the-stakes" hypothesis. The study highlights the complexity of real-life cooperation, emphasizing the need to explicitly incorporate life history parameters to understand cooperative strategies.

evolutionary biology↗

bioRxiv2024

Short-term memory, attentional control and brain size in primates

Brain size variability in primates has been attributed to various domain-specific socio-ecological factors. A recently published large-scale study of short-term memory abilities in 41 primate species [1] did not find any correlations with 11 different proxies of external cognitive demands. Here we found that the interspecific variation in test performance shows correlated evolution with total brain size, with the relationship becoming tighter as species with small sample sizes were successively removed, whereas it was not predicted by the often-used encephalization quotient (EQ). In a subsample, we also found that the sizes of brain region thought to be involved in short-term memory did not predict performance better than did overall brain size. The dependence on brain size suggests that domain-general cognitive processes underlie short-term memory as tested in [1]. These results support the emerging notion that comparative studies of brain size do not generally identify domain-specific cognitive adaptations, but rather reveal varying selection on domain-general cognitive abilities. Finally, because attentional processes beyond short- term memory also affected test performance, we suggest that the delayed response test can be refined.

animal behavior and cognition↗

bioRxiv2023

Population interconnectivity shapes the distribution and complexity of chimpanzee cumulative culture

While cumulative culture is a hallmark of hominin evolution, its origins can be traced back to our common ancestor with chimpanzees. Here we investigate the evolutionary origins of chimpanzee cumulative culture, and why it remained incipient. To trace cultural transmission among the four chimpanzee subspecies, we compared between-population networks based on genetic markers of recent migration and shared cultural traits. We show that limited levels of interconnectivity favored the emergence of a few instances of cumulative culture in chimpanzees. As in humans, cultural complexification likely happened in steps, with between-community transmission promoting incremental changes and repurposing of technologies. We propose that divergence in social patterns led to increased between-group mobility in Homo, propelling our lineage towards a trajectory of irreversible dependence on cultural exchange and complexification. One-Sentence SummaryPopulation interconnectivity through migration explains the origins of chimpanzee cumulative culture and why it remained incipient

evolutionary biology↗

bioRxiv2021

Parental provisioning drives brain size in birds

Large brains support numerous cognitive adaptations and therefore may appear to be highly beneficial. Nonetheless, the high energetic costs of brain tissue may have prevented the evolution of large brains in many species. This problem may also have a developmental dimension: juveniles, with their immature and therefore poorly performing brains, would face a major energetic hurdle if they were to pay for the construction of their own brain, especially in larger-brained species. Here we explore the possible role of parental provisioning for the development and evolution of adult brain size in birds. A comparative analysis of 1,176 bird species shows that various measures of parental provisioning (precocial vs altricial state at hatching, relative egg mass, time spent provisioning the young) strongly predict relative brain size across species. The parental provisioning hypothesis also provides an explanation for the well-documented but so far unexplained pattern that altricial birds have larger brains than precocial ones. We therefore conclude that the evolution of parental provisioning allowed species to overcome the seemingly insurmountable energetic constraint on growing large brains, which in turn enabled bird species to increase survival and population stability. Because including adult eco-and socio-cognitive predictors only marginally improved the explanatory value of our models, these findings also suggest that the traditionally assessed cognitive abilities largely support successful parental provisioning. Our results therefore indicate that the cognitive adaptations underlying successful parental provisioning also provide the behavioral flexibility facilitating reproductive success and survival. Significance StatementThe young of large brained species, if left to grow their own brain, would face a seemingly insurmountable energetic constraint, because brain tissue is energetically costly but adequate cognitive benefits arise only after a delay. We therefore hypothesize that protracted parental provisioning was a precondition for the evolution of large brains. Comparative analyses of 1,176 bird species confirmed that parental provisioning strongly predicts variation in relative brain size, suggesting that these two traits coevolved. These results provide the first explanation for the well-known difference in relative brain size between altricial and precocial birds. They also cast doubt on the explanatory value of previously considered social or technological cognitive abilities, suggesting we rethink our approach to cognitive evolution.

evolutionary biology↗

bioRxiv2021

Two evolutionary distinct effectors from a nematode and virus target RanGAP1 and 2 via the WPP domain to promote disease

The Gpa2 and Rx1 intracellular immune receptors are canonical CC-NB-LRR proteins belonging to the same R gene cluster in potato. Despite sharing high sequence homology, they have evolved to provide defence against unrelated pathogens. Gpa2 detects Gp-RBP-1 effectors secreted by the potato cyst nematode Globodera pallida whereas Rx1 recognizes the viral coat protein (CP) of Potato Virus X (PVX). How Gpa2 and Rx1 perceive their matching effectors remains unknown. Using a combination of in planta Co-Immunoprecipitation and cellular imaging, we show that both Gp-RBP-1 and PVX-CP physically interact with RanGAP2 and RanGAP1 in the cytoplasm of plant cells. Interestingly, this was also demonstrated for the eliciting variants of Gp-RBP-1 and PVX-CP indicating a role for RanGAP1 and RanGAP2 in pathogenicity independent from Gpa2 and Rx1 recognition. Indeed, knocking down both RanGAP homologs reduce cyst nematode and PVX infection. These findings show that RanGAP1/2 act as common host targets of evolutionary distinct effectors from two plant pathogens with different lifestyles. The involvement of RanGAP1/2 to pathogen virulence is a novel role not yet reported for these key host cell components and as such, their possible role in cyst nematode parasitism and viral pathogenicity are discussed. Moreover, from these findings a model emerges for their possible role as co-factor in pathogen recognition by the potato immune receptors Gpa2/Rx1.

plant biology↗