Biology subjects

Smallegange, I. M.

Publications and source records attributed to Smallegange, I. M..

9 recordsLinked to original sources

bioRxiv2025

From form to function: Morphology as a proxy for life history and population performance in fish

O_LILife history strategies emerge from trade-offs between growth, survival and reproduction and are key predictors of how populations respond to environmental disturbances. However, estimating these strategies typically requires detailed demographic data, which are unavailable for many species. Because morphological traits govern whole-organism performance, selection on ecological performance can link morphology with life history strategies. Morphological traits can thus be practical proxies for life history strategies, offering a scalable approach for data-deficient populations. C_LIO_LITo test the hypothesis that morphological traits predict major life-history axes via shared performance trade-offs, we parameterised dynamic energy budget integral projection models for 290 marine and freshwater fish species to quantify life history strategies and measured eight morphological traits from lateral-view photographs for each species. We used phylogenetically corrected principal component analysis to summarise life history strategies and morphological traits, and tested whether morphology predicts life history strategies. C_LIO_LILateral size morphology, comprising body elongation, relative eye size and oral gape position predicted generation turnover depending on water column position, and predicted reproductive output depending on clade. C_LIO_LIOur results support the hypothesis that morphologies linked to ecological performance scale up to shape demographic strategies, providing proof of concept that morphology can predict life-history strategies. They also highlight the potential to develop performance-based trait proxies for rapid, low-cost estimations of demographic vulnerability and recovery potential across data-poor fish populations--expanding the scope of life-history frameworks for fisheries management and conservation under increasing pressures from overfishing, habitat loss and climate change. C_LI

ecology↗

bioRxiv2024

To what extent can life history strategies inform species conservation planning?

Global policy aims to prevent species extinctions; to support these aims conservation planners must effectively target interventions to reduce the extinction risk of species. However, there is often a lack of knowledge on the magnitude and direction of species responses to interventions and in turn the extent to which a species extinction risk is reduced. If we can use a species life history strategies to predict their responses to interventions, this offers a promising approach to better understand species extinction risks and conservation potential. Here we apply Dynamic Energy Budget Integral Project Models to 23 reptile species to investigate whether their life history traits can be summarised into a life history strategy framework using principal component analysis, and whether species positions along these axes predict their population growth rate, demographic resilience, sensitivity to perturbations and extinction risk. We found that species positions on reproductive and pace of life axes predicted reptile population growth rate and demographic resilience but not sensitivity to perturbations or extinction risk. Our findings show that reptile life history strategies can inform our understanding of reptile species conservation potential and could be applied to influence management decisions such as establishing monitoring timelines.

ecology↗

bioRxiv2024

Changing feeding levels reveal plasticity in elasmobranch life history strategies

Life history strategies are shaped by phylogeny, environmental conditions and individual energy budgets, and have implications for conservation biology. We summarised life history traits of 151 elasmobranch species into life history strategies for two contrasting feeding levels in a principal components analysis. Two axes, reproductive output and generation turnover, structure elasmobranch life history strategies, contrasting with results from similar studies. Species positions in this life history space were not fixed, but shifted to higher reproductive output when feeding level increased. We also found that both axes predicted population performance, but that population growth rate does not necessarily inform on a species demographic resilience. Finally, neither axis predicted IUCN conservation status. Our analyses reveal plasticity in species life history strategies and warn against extrapolating the life history strategy framework from one environment to another when predicting a species response to (climate) change, perturbations, and (over)exploitation.

ecology↗

bioRxiv2023

Individual differences in developmental trajectory leave a male polyphenic signature in bulb mite populations

Developmental plasticity alters phenotypes and can in that way change the response to selection. When alternative phenotypes show different life history trajectories, developmental plasticity can also affect, and be affected by, population size-structure in an eco-evolutionary interaction. Developmental plasticity often functions to anticipate future conditions but it can also mitigate current stress conditions. Both types of developmental plasticity have evolved under different selections and this raises the question if they underlie different eco-evolutionary population dynamics. Here, we tested, in a long-term population experiment using the male polyphenic bulb mite (Rhizoglyphus robini), if the selective harvesting of juveniles of different developmental stages concurrently alters population size (ecological response) and male adult phenotype expression (evolutionary response) in line with eco-evolutionary predictions that assume the male polyphenism is anticipatory or mitigating. We found that the frequency of adult males that expressed costly (fighter) morphology was lowest under the most severe juvenile harvesting conditions. This response cannot be explained if we assume that adult male phenotype expression is to anticipate adult (mating) conditions because, in that case, only the manipulation of adult performance would have an effect. Instead, we suggest that juveniles mitigate their increased mortality risk by expediating ontogeny to forego the development of costly morphology and mature quicker but as a defenceless scrambler. If, like in mammals and birds where early-life stress effects are extensively studied, we account for such pre-adult viability selection in coldblooded species, it would allow us to (i) better characterise natural selection on trait development like male polyphenisms, (ii) understand how it can affect the response to other selections in adulthood, and (iii) understand how such trait dynamics influence, and are influenced by, population dynamics.

evolutionary biology↗

bioRxiv2022

Exploring how the fast-slow pace of life continuum and cell size structure microorganism life history variation

Studying life history strategies in microorganisms can help predict their performance when complex microbial communities can be categorised into groups of organisms with similar strategies. Microorganisms are typically classified as copiotroph or oligotroph, but it has been proven difficult to generalise their life history strategies to broad lineages. Here we tested if the fast-slow continuum and reproductive strategy framework of macro-organismal life histories can be applied to microorganisms. We used demographic and energy budget data from 13 microorganisms (bacteria, fungi, a protist and a plant) to examine how generation time, survivorship, growth form, age at maturity, recruitment success, and net reproductive rate structure microbial life histories. We found that 79% of microorganism life-history variation fell along two uncorrelated axes. Like macro-organisms, we found a fast-slow pace of life continuum, including shorter-lived microorganisms at one end, and longer-lived microorganisms that mature later in life at the other. Also, like macro-organisms, we found a second, reproductive strategy axis, with microorganisms with greater lifetime reproductive success and decreased mortality at older age at one end, and microorganisms with the opposite characteristics at the other end. Microorganismal life history strategies did not covary proportionally to their shared evolutionary history. Thus, whereas this work suggests that the macro-organismal fast-slow continuum and reproductive strategy framework could be realistically applied to microorganisms, their life history processes cannot be inferred from patterns in taxonomic composition. Impact statementAnimals and plants show distinct differences in their pace of life: some have high reproduction and high mortality, others low. Here we show that microorganisms display similar such life history patterns, igniting future research on microbial life history strategies. Data summarySupplemental data, R code and MatLab code are deposited in Figshare at https://doi.org/10.6084/m9.figshare.16831543.v2 [27].

ecology↗

bioRxiv2021

Size-structured mating niche differentiation in the male-polyphenic mite Rhizoglyphus robini

Condition-dependent expression of alternative male morphs evolves when males of different sizes experience different mating niches, requiring different morphologies. Such mating niche differentiation can be due to competitive asymmetry between large and small males in contests over mating opportunities. Here, we tested the hypothesis that aggressive interactions among males cause size-structured mating niches in an acarid mite with condition-dependent male polyphenism: the bulb mite Rhizoglyphus robini. In this species, large males mature as armed fighters with enlarged legs, and small males as scramblers without modified legs. We staged experimental dyadic contests over a mating opportunity between either a pair of fighter males, or a fighter and a scrambler male. We predicted that the larger male would have a higher likelihood of mating first in contests among fighters, that the fighter male would have a higher likelihood of mating first in fighter-scrambler contests, that fighters would have a higher likelihood of interrupting ongoing copulations if they are larger than their mating rival, and that copulations in the presence of a fighter rival therefore last shorter than copulations with a scrambler rival present. We found that in contests among fighters, the larger male had a higher probability of mating first. In contests among a fighter and scrambler, the fighter male was more likely to mate first regardless of the body size difference between the contestants. Ongoing copulations were only rarely interrupted by the rival male (always by a fighter), and the probability of interruption did not depend on the body size difference between the mating male and its rival. Copulations lasted shorter in the presence of a rival fighter, but this effect was not attributable to interruption of copulations. We conclude that the fighting niche is particularly accessible for large males, as larger males have a higher probability of winning pre-copulatory contests. Such mating niche differentiation likely contributes to evolutionary maintenance of condition-dependent male polyphenism, where small males are forced to adopt an alternative mating tactic and hence develop a dedicated morphology.

evolutionary biology↗

bioRxiv2021

Toward an understanding of the chemical ecology of alternative reproductive tactics in the bulb mite (Rhizoglyphus robini)

BackgroundUnder strong sexual selection, certain species evolve distinct intrasexual, alternative reproductive tactics (ARTs). In many cases, ARTs can be viewed as environmentally-cued threshold traits, such that ARTs coexist if their relative fitness alternates over the environmental cue gradient. Surprisingly, the chemical ecology of ARTs has been underexplored in this context. To our knowledge, no prior study has directly quantified pheromone production for ARTs in a male-polymorphic species. Here, we used the bulb mite--in which males are either armed fighters that kill conspecifics, or unarmed scramblers--as a model system to gain insight into the role of pheromones in the evolutionary maintenance of ARTs. Given that scramblers forgo investment into weaponry, we tested whether scramblers produce higher pheromone quantities than fighters, which would improve the fitness of the scrambler phenotype, e.g. through female mimicry to avoid aggression from competitors. To this end, we sampled mites from a rich and a poor nutritional environment and quantified their production of the female sex pheromone -acaridial through gas chromatography analysis. ResultsWe found a positive relationship between pheromone production and body size, but males exhibited a steeper slope in pheromone production with increasing size than females. Females exhibited a higher average pheromone production than males. We found no significant difference in slope of pheromone production over body size between fighters and scramblers. However, scramblers reached larger body sizes and higher pheromone production than fighters, providing some evidence for a potential female mimic strategy adopted by large scramblers. Pheromone production was significantly higher in mites from the rich nutritional environment than the poor environment. ConclusionFurther elucidation of pheromone functionality in bulb mites, and additional inter-and intrasexual comparisons of pheromone profiles are needed to determine if the observed intersexual and intrasexual differences in pheromone production are adaptive, if they are a by-product of allometric scaling, or diet-mediated pheromone production under weak selection. We argue chemical ecology offers a novel perspective for research on ARTs and other complex life-history traits.

evolutionary biology↗

bioRxiv2021

Nutrient-dependent allometric plasticity in a male-diphenic mite

Male secondary sexual traits often scale allometrically with body size. These allometries can be variable within species, and may shift depending on environmental conditions such as food quality. Such allometric plasticity has been hypothesized to initiate local adaptation and evolutionary diversification of scaling relationships, but is under-recorded, and its eco- evolutionary effects are not well understood. Here, we test for allometric plasticity in the bulb mite (Rhizoglyphus robini) in which large males tend to develop as armed adult fighters with thickened third legs, while small males become adult scramblers without thickened legs. We first examined the ontogenetic timing for size- and growth-dependent male morph determination, using experimentally amplified fluctuations in growth rate throughout juvenile development. Having established that somatic growth and body size determine male morph expression immediately before metamorphosis, we examined whether the relationship between adult male morph and size at metamorphosis shifts with food quality. We found that the threshold body size for male morph expression shifts towards lower values with deteriorating food quality, confirming food-dependent allometric plasticity. Such allometric plasticity may allow populations to track prevailing nutritional conditions, potentially facilitating rapid evolution of allometric scaling relationships.

evolutionary biology↗

bioRxiv2021

Facultative release from developmental constraints through polyphenism promotes adaptively flexible maturation

The timing of maturation, a critical fitness determinant, is influenced by developmental and energetic constraints, particularly when growth is poor in adverse conditions. Such constraints can be altered through developmental plasticity. Thus, in theory, plasticity in energetically costly sexually selected morphologies can promote life history flexibility in variable environments. We experimentally tested this hypothesis in bulb mites (Rhizoglyphus robini) that polyphenically develop as armed fighters with enlarged legs or as scramblers without modified legs. We found that (i) mites enter metamorphosis earlier if they develop as scramblers, (ii) mites accelerate the onset of metamorphosis when they sense resource limitation, and (iii) scrambler expression increases under increased competition for food, enabling males to mature early and escape juvenile mortality. We propose that life history plasticity can evolve through polyphenic release from sexually selected constraints, making the evolutionary dynamics of secondary sexual traits and life history traits, typically studied separately, interdependent.

evolutionary biology↗