Biology subjects

Novak, M.

Publications and source records attributed to Novak, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Hazard characterization of Alternaria toxins - filling data gaps on in vitro genotoxicity.

Alternaria toxins are naturally occurring food contaminants with limited and often inconsistent genotoxicity and mutagenicity data. Within the European Partnership for the Assessment of Risks from Chemicals (PARC), an OECD-aligned in vitro testing strategy was applied to fill existing data gaps and to characterize the genotoxic potential of major Alternaria toxins using high-purity test materials. Mutagenicity was assessed using bacterial reverse mutation test (OECD TG 471) and SOS/umu assay, while chromosomal damage was assessed using the in vitro micronucleus (MN) assay (OECD TG 487) in TK6 and HepG2 cells, complemented by fluorescence in situ hybridization (FISH) and {gamma}H2AX assay in HepaRG cells. Alternariol (AOH), alternariol monomethyl ether (AME), and altertoxin-I (ATX-I) showed clear mutagenicity in bacteria, whereas altenuene (ALT), tenuazonic acid (TeA), and tentoxin (TEN) were negative under the tested conditions. In mammalian cells, AOH, AME, and ATX-I induced MN formation in TK6 cells at concentrations [≥]5.5 {micro}M, [≥]2.5 {micro}M, and [≥]0.21 {micro}M, respectively, with FISH analysis supporting a clastogenic mode of action. In HepG2 cells, all tested toxins induced chromosomal damage, with effect threshold ranging from [≥]6.25 {micro}M (AOH) to [≥]50 {micro}M (TeA). {gamma}H2AX induction confirmed DNA damage for AOH and ATX-I, and at higher concentrations for TeA (1000 {micro}M). Overall, the data indicate clear in vitro genotoxic potential for AOH, AME, and ATX-I and provide evidence of chromosomal damage for ALT, TEN, and TeA, thereby reducing critical data gaps for hazard assessment.

pharmacology and toxicology↗

bioRxiv2026

Symbolic regression for empirically realistic population dynamic time series

Applications of machine learning in ecology are rapidly expanding. Symbolic regression is gaining particular attention for its success in reverse-engineering human-readable explanatory population models, including the logistic growth and Lotka-Volterra equations, from simulated and laboratory-based population time series. However, field-based populations often lack the characteristics of the idealized time series used in prior assessments. We evaluated the utility of symbolic regression for such time series by quantifying its success for synthetic data varying in sampling density, population cycle asymmetry, process noise, and the erroneous consideration of spurious variables. We further compared two data preprocessing options for estimating population growth rates, and four evaluation workflows for selecting equations. Results indicate that a trade-off between sampling density and process noise primarily drives equation and variable recovery. Symbolic regression failed to recover the underlying equation at sampling densities below 10 points per cycle; however, at higher sampling densities, process noise did increase equation recovery rates. Importantly, although the true model was frequently recovered at sampling densities of 25 or more points per cycle, it was not consistently selected by the evaluation workflows. This discrepancy highlights a need for more robust post-algorithm selection criteria to identify the focal equation among competing candidates.

ecology↗

bioRxiv2025

Sea urchin consumption of kelp controlled by the density of drift algae

Rocky reef kelp forests can exhibit abrupt shifts between forested and barren states where unchecked sea urchin grazing inhibits kelp recovery. Forefront to urchin barren formation is a behavioral switch where sedentary urchins become active and graze upon attached kelp. This is hypothesized to occur when the availability of drift (i.e., detached kelp on the surface of the reef), which urchins are believed to prefer over intact and attached kelp, declines. Although observed repeatedly, the density-dependent nature of this apparent resource preference has not been characterized quantitatively. We used a series of subtidal functional response experiments in central California, USA, to quantify how consumption rates by Strongylocentrotus purpuratus (purple urchins) on Macrocystis pyrifera (giant kelp) and drift varied with their relative availability and over time as urchins became satiated. Our experiments indicate that the preference for drift over kelp is strong when drift and kelp are at equal abundance, that the abundance of drift has a strong effect on kelp consumption but not vice versa, and that the preferences for drift is indeed density dependent with the qualitative switch to a greater preference for kelp occurring when the availability of drift declines below approximately 1 g of drift for every 60 g of kelp. Our analyses suggest further that maintaining at least equal amounts of drift and kelp is sufficient to all but preclude urchins from grazing on live kelp. We recommend drift be used as an indicator of reef health, and that our thresholds be considered to guide drift subsidies to preserve and restore kelp forests.

ecology↗

bioRxiv2025

Glioblastoma-natural killer cell crosstalk: insights from dynamic spheroid models reveal the importance of secreted cytokines and the CD155 axis

Glioblastoma (GB) is an aggressive primary brain cancer with poor patient prognosis. Natural killer (NK) cells can recognise and eliminate a range of malignant cells, including GB stem cells, which drive GB recurrence. NK cell-based immunotherapy has emerged as a promising approach for GB treatment, but a better understanding of the complex crosstalk between GB and NK cells is needed, particularly within the immunosuppressive GB tumour microenvironment. In this study, we established a reproducible protocol for the production and dynamic culture of uniformly sized GB spheroids using the Celvivo Clinostar system. Our spheroids recapitulated the heterogeneous structure of GB and expressed ligands for NK cell receptors at levels distinct from those observed in corresponding GB cell lines in standard culture, implicating altered sensitivity of GB cells to NK cells in dynamic 3D cultures. GB-NK cell crosstalk was GB cell type dependent and the ability of NK cells to infiltrate GB did not necessarily correlate with their cytotoxicity against GB cells. Spheroids derived from differentiated GB cells secreted higher levels of immunomodulatory cytokines compared to spheroids from GB stem-like cells, and a prominent increase in the secretion of immune-attracting factors was observed in their co-cultures with NK cells. Finally, the CD155-DNAM1/TIGIT axis was indicated as an important regulator of NK cell cytotoxicity against GB stem-like cells. Collectively, our results highlight important factors in GB-NK cell communication and provide a groundwork for further targeted research as well as therapeutic evaluation of NK cell-based approaches in the established dynamic 3D cultures.

cancer biology↗

bioRxiv2025

Effects of ancestry, agriculture, and lactase persistence on the stature of prehistoric Europeans

Ancient DNA has revolutionized our understanding of human evolutionary history, but studies focusing solely on genetic variation tell an incomplete story by neglecting phenotypic outcomes. The relationships between genotype and phenotype can change over time, making it desirable to study them directly in ancient populations rather than present-day data. Here, we present a large-scale integration of ancient genomic and phenotypic data, analyzing femur length as a proxy for stature in 568 individuals with published whole-genome ancient DNA data across western Eurasia. Polygenic scores derived from modern European and East Asian genome-wide association studies retain predictive power in ancient populations, explaining up to 10% of phenotypic variance. Contrary to longstanding archaeological hypotheses, we find that Neolithic populations were only modestly shorter than preceding Mesolithic groups, with differences at least partly attributable to genetic rather than environmental factors, challenging narratives of systematic stature decline following the transition to agriculture. Finally, we find that the lactase persistence allele had a large positive effect on stature in ancient individuals (0.24 standard deviations), even though it shows no association with height in modern populations. This gene-environment interaction highlights the limitation of using present-day genetic data to infer past phenotypic relationships. Our results underscore the value of integrating genetic and morphological data from ancient populations to reconstruct the dynamics of human adaptation.

genetics↗

bioRxiv2025

A Universal Scaling Law for Mitotic Spindles Driven by Chromosome Crowding

Cells regulate the size of their internal structures to maintain function in diverse biological settings1. The mitotic spindle, a molecular micro-machine responsible for chromosome segregation2, must scale to accommodate genomes varying in size by over 10,000-fold across eukaryotes3. Yet, how spindle biomechanics adapts to vastly different genome sizes remains unknown. Here, we uncover a universal spindle scaling law, where metaphase plate width scales with genome size following a power law with an exponent of [~]1/3. We hypothesize that chromosome crowding within the metaphase plate generates compressive forces as chromosomes push against each other, thereby determining spindle size and shape. Our experiments with altered chromosome number and mechanical properties in healthy and cancerous human and mouse cells, together with a theoretical model based on inter-chromosome pushing forces and mechanical manipulations of cells, confirm this hypothesis. Extending these insights across eukaryotes, we demonstrate that chromosome crowding predicts the observed power-law scaling. The biophysical constraint of chromosome crowding offers a mechanistic explanation for the evolution of open mitosis and mitotic cell rounding, enabling the division of larger genomes. Spindle adaptability to larger genomes may promote the proliferation of polyploid cells, driving not only tumor progression but also speciation during evolution.

biophysics↗

bioRxiv2025

Heterogenous mitochondrial ultrastructure and metabolism of human glioblastoma cells: differences between stem-like and differentiated cancer cells in response to chemotherapy

BackgroundGlioblastoma stem-like cells (GSCs) contribute to the resistance of glioblastoma (GBM) tumors to standard therapies. The cellular and molecular background of the resistance of GSCs to the chemotherapeutic agent temozolomide is not yet fully understood, in particular in the context of cellular metabolism and the role of mitochondria. The aim of this study was to perform a detailed ultrastructural characterization of the mitochondria of GSCs prior and post temozolomide exposure and to compare it to differentiated GBM cells. MethodsPatient-derived and established GSC and GBM differentiated cell lines were used for the study. The ultrastructure of the mitochondria of the examined cell lines was assessed by transmission electron microscopy. The microscopic analysis was complemented and compared by an analysis of cell metabolism using cell viability assay and extracellular flux analysis using Seahorse assay. ResultsWe found that the metabolic profile of GSCs is quiescent and aerobic. Their elongated mitochondria with highly organized cristae is indicating increased biogenesis and mitochondrial fusion and corresponds to a more OXPHOS-dependent metabolism. The metabolism of GSCs is dependent on OXPHOS and there are no changes in defective mitochondria fraction after the treatment with temozolomide. In contrast, differentiated GBM cells with fragmented mitochondria, which have less organized cristae, are more energetic and glycolytic. Temozolomide treatment induced significant ultrastructural mitochondrial damage in differentiated GBM cells and had less effect on mitochondria in GSCs, suggesting that mitochondria play an important role in the resistance of GSCs to temozolomide treatment. ConclusionsWe demonstrated differences in mitochondrial ultrastructure and cellular metabolism between GSCs and differentiated GBM cells in response to temozolomide. This study provides a basis for further studies addressing the chemotherapy resistance of GSCs and the effects of different treatment regimens on the mitochondrial structure and function of GSCs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/638633v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@14674e1org.highwire.dtl.DTLVardef@a38976org.highwire.dtl.DTLVardef@95d7a5org.highwire.dtl.DTLVardef@180b6dd_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

Reconstructing life history of the 18th century priest from Prozorje, Croatia: bioarchaeological and biochemical approaches

The study presents a case of the adult male individual dated to the Early Modern Period buried at the church of St. Martin at Prozorje in Croatia. Based on the burial characteristic, the individual is presumed to be a member of the clergy. Using stable carbon and nitrogen isotope analysis of the dentine increments from the second permanent mandibular molar (Man 2) of the individual, this study aims to identify dietary changes during the juvenile years of the individual in order to reconstruct the timing of his admission into the seminary. Mean{delta} 13C and{delta} 15N values indicate mixed C3 and C4 terrestrial based diet with the visible animal protein intake. Results of the incremental dentine analysis provide more detailed information. The possible end of the weaning period is identified, followed by the diet based on C4 resources with low animal protein intake with periods of physiological stress during his early childhood. By the end of the observed period, significant dietary change is recorded characterised by the high animal protein intake and consumption of less C4 resources. According to the historical resources, this corresponds with the timing clergy cadets usually entered the seminary with the dietary regiment consisting of daily intake of meat or fish dishes accompanied by variety of fruit and vegetables (C3 resources). This is the first such study conducted in this part of Europe and it significantly contributes to our knowledge of dietary practices and certain social customs in Early Modern Period Croatia.

biochemistry↗

bioRxiv2024

Different hydrological conditions after permafrost thaw result in distinct microbial community compositions

Permafrost degradation leads to the formation of contrasting hydrological conditions such as water-saturated anoxic and dry oxic soils, which significantly influence the bacterial community structure and abundance. To investigate the bacterial abundance and diversity under these hydrological conditions, we collected soil samples from different horizons of both dry and wet degraded permafrost soils and non-degraded intact permafrost soil for comparison. The bacterial alpha diversity, measured by the Observed and Chao1 indices, was significantly greater in wet degraded permafrost soil (wet site) and intact permafrost soil (intact site) than in dry degraded permafrost soils (dry site). Notably, the wet and intact sites exhibited similar levels of alpha diversity as well as shared greater number of zOTUs. The relative proportion of most bacterial taxa was significantly differed among the sites. At the class level, dry site was dominated mainly by K-strategic bacteria like aliphatic degraders (Thermoleophilia), acidophilic and cellulolytic (Acidobacteriae), while wet site was dominated by mainly r-strategic bacteria from class Gammaproteobacteria and anoxygenic aerobic phototrophs (Gemmatimonadetes). According to Spearman correlation analysis, the relative proportion of bacterial taxa in dry and wet sites showed significant correlation with soil physicochemical parameters, whereas fewer correlations were found in intact site. The relative proportion of Pseudomonadota classes and Acidobacteriota were positively correlated with SOC, N, and C:N ratio, but were negatively correlated with pH in both dry and wet sites. In contrast, anaerobic methylotrophs (Methylomirabilota), anoxygenic photoheterotrops (Chloroflexota), Gemmatimonadota and filamentous Actinobacteriota were negatively correlated with SOC, N, and C:N. Additionally, strong correlations were observed between bacterial taxa and extracellular enzyme activities, where Alphaproteobacteria, Gammaproteobacteria, and Acidobacteriota showed positive correlations with both hydrolytic and oxidative enzymes in dry and wet sites, except for PerOx in wet site where they showed negative correlation. Conversely, Gemmatimonadota and Actinobacteriota displayed negative correlations with enzymes in dry and wet site, except for the PerOx in wet site, where they showed positive correlation.

ecology↗

bioRxiv2024

Simple, universal rules predict trophic interaction strengths

Many drivers of ecological systems exhibit regular scaling relationships, yet the mechanisms explaining these relationships are often unknown. Trophic interaction strengths are no exception, exhibiting scaling relationships with predator and prey traits that lack evolutionary explanations. We propose two rules to explain the scaling of trophic interaction strengths through the relationship between a predators feeding rate and its preys density -- the so-called predator functional response. First, functional responses allow predators to meet their energetic demands when prey are rare. Second, functional responses approach their maxima near the highest prey densities predators experience. We show that equations derived from these rules predict functional response parameters across over 2,100 functional response experiments and make additional predictions such as their allometric scaling. The two rules thereby offer a potential ultimate explanation for the determinants of trophic interaction strengths, revealing ecologically realized constraints to the complex, adaptive nature of functional response evolution.

ecology↗

bioRxiv2024

Dizocilpine derivatives with neuroprotective effect lacking the psychomimetic side effects

We aimed to prepare novel dibenzosuberane derivatives that act on N-methyl-D-aspartate (NMDA) receptors with potential neuroprotective effects. Our approach involved modifying the tropane moiety of MK-801, a potent open-channel blocker known for its psychomimetic side effects, by introducing a seven-membered ring with substituted base moieties specifically to alleviate these undesirable effects. Our in silico analyses showed that these derivatives should have high gastrointestinal absorption and cross the blood-brain barrier (BBB). Our pharmacokinetic studies in rats supported this conclusion and confirmed the ability of leading compounds 3l and 6f to penetrate the BBB. Electrophysiological experiments showed that all compounds exhibited different inhibitory activity towards the two major NMDA receptor subtypes, GluN1/GluN2A and GluN1/GluN2B. Of the selected compounds intentionally differing in the inhibitory efficacy, 6f showed high relative inhibition ([~]90% for GluN1/GluN2A), while 3l showed moderate inhibition ([~]50%). An in vivo toxicity study determined that compounds 3l and 6f were safe at 10 mg/kg doses with no adverse effects. Behavioral studies demonstrated that these compounds did not induce hyperlocomotion or impair prepulse inhibition of startle response in rats. Neuroprotective assays using a model of NMDA-induced hippocampal neurodegeneration showed that compound 3l at a concentration of 30 M significantly reduced hippocampal damage in rats. These results suggest that these novel dibenzosuberane derivatives are promising candidates for developing NMDA receptor-targeted therapies with minimal psychotomimetic side effects.

neuroscience↗

bioRxiv2024

In defense of the Type I functional response: The frequency and population-dynamic effects of feeding on multiple prey at a time

Ecologists differ in the degree to which they consider the linear Type I functional response to be an unrealistic versus sufficient representation of predator feeding rates. Empiricists tend to consider it unsuitably non-mechanistic and theoreticians tend to consider it necessarily simple. Hollings original rectilinear Type I response is dismissed by satisfying neither desire, with most compromising on the smoothly saturating Type II response for which searching and handling are assumed to be mutually exclusive activities. We derive a "multiple-prey-at-a-time" response and a generalization that includes the Type III to reflect predators that can continue to search when handling an arbitrary number of already-captured prey. The multi-prey model clarifies the empirical relevance of the linear and rectilinear models and the conditions under which linearity can be a mechanistically-reasoned description of predator feeding rates, even when handling times are long. We find support for linearity in 35% of 2,591 compiled empirical datasets and support for the hypothesis that larger predator-prey body-mass ratios permit predators to search while handling greater numbers of prey. Incorporating the multi-prey response into the Rosenzweig-MacArthur population-dynamics model reveals that a non-exclusivity of searching and handling can lead to coexistence states and dynamics that are not anticipated by theory built on the Type I, II, or III response models. In particular, it can lead to bistable fixed-point and limit-cycle dynamics with long-term crawl-by transients between them under conditions where abundance ratios reflect top-heavy food webs and the functional response is linear. We conclude that functional response linearity should not be considered empirically unrealistic but also that more cautious inferences should be drawn in theory presuming the linear Type I to be appropriate.

ecology↗

bioRxiv2024

Bioarchaeological Perspectives on Late Antiquity in Dalmatia: Paleogenetic, Dietary, and Population Studies of the Hvar Radosevic burial site

Late Antiquity Dalmatia was a time and place of political unrest in the Roman Empire that influenced the lives of the people living in that region. The Late Antique burial site of Hvar - Rado[s]evi[c], spanning the 3rd to 5th centuries, is located on the Croatian Dalmatian island of Hvar. Given the time frame and its location on a busy marine trade route, study of this burial site offers us a glimpse into the lives of the Late Antique population living on this island. It comprises 33 individuals, with 17 buried within a confined grave tomb, and the remaining individuals buried in separate locations in the tombs proximity. Our objective was to provide new perspectives on the lives of people on the island during those times by studying ancestry, population structure, possible differences within the buried population, dietary habits, and general health. Analysis of the ancestral origins of the individuals buried at Hvar - Rado[s]evi[c] revealed a diverse population reflective of the eras genetic variability. The identification of genetic outliers suggests affiliations with distinct regions of the Roman Empire, possibly linked to trade routes associated with the Late Antique port in ancient Hvar. Stable isotope ratio analysis ({delta}{superscript 1}3C and {delta}{superscript 1}N) indicated a diet mainly consisting of C3 plants, with minimal consumption of marine foods. High childhood mortality rates, physiological stress markers, and dental diseases suggest a low quality of life in the population. Assessment of kinship and dietary patterns revealed no discernible distinctions between individuals buried within the tomb and those buried outside, indicative of an absence of differential burial practices based on social status and familial ties.

genomics↗

bioRxiv2024

Potent and reversible open-channel blocker of NMDA receptor derived from dizocilpine with enhanced membrane-to-channel inhibition

N-methyl-D-aspartate receptors (NMDARs) play a significant role in developing several central nervous system (CNS) disorders. Currently, memantine, used for treating Alzheimers disease, and ketamine, known for its anesthetic and antidepressant properties, are two clinically used NMDAR open-channel blockers. However, despite extensive research into NMDAR modulators, many have shown either harmful side effects or inadequate effectiveness. For instance, dizocilpine (MK-801) is recognized for its powerful psychomimetic effects due to its high-affinity and nearly irreversible inhibition of the GluN1/GluN2 NMDAR subtypes. Unlike ketamine, memantine and MK-801 also act through a unique, low-affinity "membrane-to-channel inhibition" (MCI). We aimed to develop an open-channel blocker based on MK-801 with distinct inhibitory characteristics from memantine and MK-801. Our novel compound, K2060, demonstrated effective voltage-dependent inhibition in the micromolar range at key NMDAR subtypes, GluN1/GluN2A and GluN1/GluN2B, even in the presence of Mg2+. K2060 showed reversible inhibitory dynamics and a partially trapping open-channel blocking mechanism with a significantly stronger MCI than memantine. Using hippocampal slices, 30 {micro}M K2060 inhibited excitatory postsynaptic currents in CA1 hippocampal neurons by [~]51%, outperforming 30 {micro}M memantine ([~]21% inhibition). K2060 exhibited No Observed Adverse Effect Level (NOAEL) of 15 mg/kg upon intraperitoneal administration in mice. Administering K2060 at a 10 mg/kg dosage resulted in brain concentrations of approximately 2 {micro}M, with peak concentrations (Tmax) achieved within 15 minutes. Finally, applying K2060 with trimedoxime and atropine in mice exposed to tabun improved treatment outcomes. These results underscore K2060s potential as a therapeutic agent for CNS disorders linked to NMDAR dysfunction.

neuroscience↗

bioRxiv2023

Improved detection of methylation in ancient DNA

Reconstructing premortem DNA methylation levels in ancient DNA (aDNA) has led to breakthrough studies such as the prediction of anatomical features of the Denisovan, as well as the castration status of ancient horses. These studies relied on computationally inferring methylation levels from damage signals in naturally deaminated cytosines. Because of statistical constraints, this inference requires high-coverage sequencing, and is thus not only expensive but also restricted to samples with exceptional DNA preservation. Instead, a method to directly measure methylation levels in aDNA, as exists in modern DNA samples, would open the door to a more thorough and cost effective ability to study ancient DNA methylation. We have tested two methods for direct methylation measurement developed for modern DNA based on either bisulfite or enzymatic methylation treatments. We find that both methods preserve sufficient DNA yields to allow for methylation measurement. Bisulfite treatment, combined with a single stranded library preparation, shows the least reduction in DNA yields compared to no methylation treatment, as well as the least biases during methylation conversion. In addition, we show that applying bisulfite treatment to [~]0.4-fold coverage sample provides a methylation signal that is comparable to, or even better, than the computationally inferred one. We thus present a method to directly measure methylation in ancient DNA that is cost effective and can be used on a wide variety of ancient samples.

genomics↗

bioRxiv2023

Chemotactic agents combining spatial and temporal gradient-sensing boost spatial comparison if they are large, slow, and less persistent

Biological cells and small organisms navigate in concentration fields of signaling molecules using two fundamental gradient-sensing strategies: spatial comparison of concentrations measured at different positions on their surface, or temporal comparison of concentrations measured at different locations visited along their motion path. It is believed that size and speed dictate which gradient-sensing strategy cells choose, yet this has never been formally proven. Using information theory, we investigate the optimal gradient-sensing mechanism for an ideal chemotactic agent that combines spatial and temporal comparison. We account for physical limits of chemo-sensation: molecule counting noise at physiological concentrations, and motility noise inevitable at the micro-scale. Our simulation data collapses onto an empirical power-law that predicts an optimal weighting of information as function of motility and sensing noise, demonstrating how spatial comparison becomes more beneficial for agents that are large, slow and less persistent. This refines and quantifies the previous heuristic notion. Our idealized model assuming unlimited information processing capabilities serves as a benchmark for the chemotaxis of biological cells.

biophysics↗

bioRxiv2022

Predator feeding rates may often be unsaturated under typical prey densities

Predator feeding rates (described by their functional response) must saturate at high prey densities. Although thousands of manipulative functional response experiments show feeding rate saturation at high densities under controlled conditions, it is unclear how saturated feeding rates are at natural prey densities. The general degree of feeding rate saturation has important implications for the processes determining feeding rates and how they respond to changes in prey density. To address this, we linked two databases - one of functional response parameters and one on mass-abundance scaling - through prey mass to calculate a feeding rate saturation index. We find that: 1) feeding rates may commonly be unsaturated and 2) the degree of saturation varies with predator and prey taxonomic identities and body sizes, habitat, interaction dimension, and temperature. These results reshape our conceptualization of predator-prey interactions in nature and suggest new research on the ecological and evolutionary implications of unsaturated feeding rates.

ecology↗

bioRxiv2022

High variation in handling times confers 35-year stability to predatorfeeding rates despite altered prey abundances and apparent diet proportions

Historical resurveys of ecological communities are important for placing the structure of modern ecosystems in context. Rarely, however, are snapshot surveys alone sufficient for providing direct insight into the rates of ecological processes that underlie how communities function, either now or in the past. In this study, I used a statistically-reasoned observational approach to estimate the feeding rates of a New Zealand intertidal predator, Haustrum haustorium, using diet surveys performed at several sites by Robert Paine in 1968-9 and by me in 2004. Comparisons between time periods reveal a remarkable consistency in H. haustoriums prey-specific feeding rates, which contrasts with the changes I observed in prey abundances, H. haustoriums body size distribution, and the proportional contributions of H. haustoriums prey to its apparent diet. Although these results imply accompanying and perhaps adaptive changes in H. haustoriums prey preferences, they are nonetheless anticipated by H. haustoriums high range of variation in prey-specific handling times that dictate not only its maximum possible feeding rates but also the probabilities with which feeding events may be detected during diet surveys. Similarly high variation in detection times (i.e. handling and digestion times) is evident in predator species throughout the animal kingdom. The potential disconnect between a predators apparent diet and its actual feeding rates suggests that much of the temporal and biogeographic variation that is perceived in predator diets and food-web structures may be of less functional consequence than currently assumed.

ecology↗