Resource‐related variables drive individual variation in flowering phenology and mediate population‐level flowering responses to climate in an asynchronously reproducing palm

Abstract The degree to which foraging individuals are able to appropriately modify their behaviors in response to dynamic environmental conditions and associated resource availability can have important fitness consequences. Despite an increasingly refined understanding of differences in foraging behavior between individuals, we still lack detailed characterizations of within-individual variation over space and time, and what factors may drive this variability. From 2014 to 2017, we used GPS transmitters and accelerometers to document foraging movements by breeding adult Brown Pelicans (Pelecanus occidentalis) in the northern Gulf of Mexico, where the prey landscape is patchy and dynamic at various scales. Assessments of traditional foraging metrics such as trip distance, linearity, or duration did not yield significant relationships between individuals. However, we did observe lower site fidelity and less variation in energy expenditure in birds of higher body condition, despite a population-level trend of increased fidelity as the breeding season progressed. These findings suggest that high-quality individuals are both more variable and more efficient in their foraging behaviors during a period of high energetic demand, consistent with a “rich get richer” scenario in which individuals in better condition are able to invest in more costly behaviors that provide higher returns. This work highlights the importance of considering behavioral variation at multiple scales, with particular reference to within-individual variation, to improve our understanding of foraging ecology in wild populations.

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Phenology and seed production in Chenopodium rubrum, Rumex maritimus, and Rumex palustris as related to photoperiod in river forelands

Canadian Journal of Botany ◽

10.1139/b92-053 ◽

1992 ◽

Vol 70 (2) ◽

pp. 392-400 ◽

Cited By ~ 15

Author(s):

A. J. M. Van der Sman ◽

C. W. P. M. Blom ◽

H. M. Van de Steeg

Keyword(s):

Life Cycle ◽

Seed Production ◽

Population Level ◽

Flowering Phenology ◽

Chenopodium Rubrum ◽

Axillary Shoots ◽

Critical Photoperiod ◽

Number Of Leaves ◽

Rumex Maritimus ◽

Flooded Areas

Reproductive development in three species from irregularly flooded areas of river forelands was studied in relation to time of emergence. In Chenopodium rubrum, flowering was induced earlier in plants germinated in April–May than in later cohorts. However, the period of vegetative growth diminished and the life cycle was completed in a shorter time in later germinated plants. Seed number was reduced, but seed size as well as reproductive effort per plant increased in later cohorts. Plants of both Rumex species flowered after a certain number of leaves had developed and before a critical photoperiod had passed. In earlier cohorts, the main shoot and several axillary shoots elongated and flowered. Fewer axillary shoots flowered closer to the critical photoperiod, and this resulted in a reduced seed output in later cohorts. The critical photoperiod as well as the time needed for completion of the life cycle was longer in Rumex palustris than in Rumex maritimus. It is argued that in the riparian habitat, plants of both Rumex species are only occasionally able to complete their life cycle in one growing season. Survival of these species on the population level will rely more upon adaptations towards flooding during the established phase than is the case for C. rubrum. Key words: flowering phenology, photoperiod, seed production, Chenopodium rubrum, Rumex maritimus, Rumex palustris.

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Walking behaviour in the ground beetle, Poecilus cupreus: dispersal potential, intermittency and individual variation

Bulletin of Entomological Research ◽

10.1017/s0007485320000565 ◽

2020 ◽

pp. 1-10

Author(s):

Joseph D. Bailey ◽

Carly M. Benefer ◽

Rod P. Blackshaw ◽

Edward A. Codling

Keyword(s):

Individual Variation ◽

Community Dynamics ◽

Ground Beetle ◽

Management Strategies ◽

Population Level ◽

Poecilus Cupreus ◽

Individual Level ◽

Dispersal Potential ◽

Simple Movement ◽

Dispersal Distances

Abstract Dispersal is a key ecological process affecting community dynamics and the maintenance of populations. There is increasing awareness of the need to understand individual dispersal potential to better inform population-level dispersal, allowing more accurate models of the spread of invasive and beneficial insects, aiding crop and pest management strategies. Here, fine-scale movements of Poecilus cupreus, an important agricultural carabid predator, were recorded using a locomotion compensator and key movement characteristics were quantified. Net displacement increased more rapidly than predicted by a simple correlated random walk model with near ballistic behaviour observed. Individuals displayed a latent ability to head on a constant bearing for protracted time periods, despite no clear evidence of a population level global orientation bias. Intermittent bouts of movement and non-movement were observed, with both the frequency and duration of bouts of movement varying at the inter- and intra-individual level. Variation in movement behaviour was observed at both the inter- and intra- individual level. Analysis suggests that individuals have the potential to rapidly disperse over a wider area than predicted by simple movement models parametrised at the population level. This highlights the importance of considering the role of individual variation when analysing movement and attempting to predict dispersal distances.

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Employing individual measures of baseline glucocorticoids as population-level conservation biomarkers: considering within-individual variation in a breeding passerine

Conservation Physiology ◽

10.1093/conphys/cow048 ◽

2016 ◽

Vol 4 (1) ◽

pp. cow048 ◽

Cited By ~ 7

Author(s):

Christine L. Madliger ◽

Oliver P. Love

Keyword(s):

Individual Variation ◽

Population Level

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A Multivariate Approach to Determine the Dimensionality of Human Facial Asymmetry

Symmetry ◽

10.3390/sym12030348 ◽

2020 ◽

Vol 12 (3) ◽

pp. 348

Author(s):

Omid Ekrami ◽

Peter Claes ◽

Julie D. White ◽

Seth M. Weinberg ◽

Mary L. Marazita ◽

...

Keyword(s):

Individual Variation ◽

Facial Asymmetry ◽

Population Level ◽

Directional Asymmetry ◽

Main Step ◽

Valuable Insight ◽

Biological Processes ◽

Measure Of Asymmetry ◽

Different Dimensions ◽

Insight Into

Many studies have suggested that developmental instability (DI) could lead to asymmetric development, otherwise known as fluctuating asymmetry (FA). Several attempts to unravel the biological meaning of FA have been made, yet the main step in estimating FA is to remove the effects of directional asymmetry (DA), which is defined as the average bilateral asymmetry at the population level. Here, we demonstrate in a multivariate context that the conventional method of DA correction does not adequately compensate for the effects of DA in other dimensions of asymmetry. This appears to be due to the presence of between-individual variation along the DA dimension. Consequently, we propose to decompose asymmetry into its different orthogonal dimensions, where we introduce a new measure of asymmetry, namely fluctuating directional asymmetry (F-DA). This measure describes individual variation in the dimension of DA, and can be used to adequately correct the asymmetry measurements for the presence of DA. We provide evidence that this measure can be useful in disentangling the different dimensions of asymmetry, and further studies on this measure can provide valuable insight into the underlying biological processes leading to these different asymmetry dimensions.

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Age-related declines in immune response in a wild mammal are unrelated to immune cell telomere length

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.2949 ◽

2016 ◽

Vol 283 (1825) ◽

pp. 20152949 ◽

Cited By ~ 13

Author(s):

Christopher Beirne ◽

Laura Waring ◽

Robbie A. McDonald ◽

Richard Delahay ◽

Andrew Young

Keyword(s):

Telomere Length ◽

Individual Variation ◽

Immune Cell ◽

Ex Vivo ◽

Natural Populations ◽

Population Level ◽

Meles Meles ◽

Wild Mammal ◽

Age Related ◽

Age Variation

Senescence has been hypothesized to arise in part from age-related declines in immune performance, but the patterns and drivers of within-individual age-related changes in immunity remain virtually unexplored in natural populations. Here, using a long-term epidemiological study of wild European badgers ( Meles meles ), we (i) present evidence of a within-individual age-related decline in the response of a key immune-signalling cytokine, interferon-gamma (IFN γ ), to ex vivo lymphocyte stimulation, and (ii) investigate three putative drivers of individual variation in the rate of this decline (sex, disease and immune cell telomere length; ICTL). That the within-individual rate of age-related decline markedly exceeded that at the population level suggests that individuals with weaker IFN γ responses are selectively lost from this population. IFN γ responses appeared to decrease with the progression of bovine tuberculosis infection (independent of age) and were weaker among males than females. However, neither sex nor disease influenced the rate of age-related decline in IFN γ response. Similarly, while ICTL also declines with age, variation in ICTL predicted neither among- nor within-individual variation in IFN γ response. Our findings provide evidence of within-individual age-related declines in immune performance in a wild mammal and highlight the likely complexity of the mechanisms that generate them.

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Hierarchical Bayesian inference for concurrent model fitting and comparison for group studies

10.1101/393561 ◽

2018 ◽

Cited By ~ 3

Author(s):

Payam Piray ◽

Amir Dezfouli ◽

Tom Heskes ◽

Michael J. Frank ◽

Nathaniel D. Daw

Keyword(s):

Parameter Estimation ◽

Bayesian Inference ◽

Individual Variation ◽

Model Comparison ◽

Statistical Tests ◽

Model Fitting ◽

Population Level ◽

Parameter Estimates ◽

Hierarchical Bayesian ◽

Hierarchical Bayesian Inference

AbstractComputational modeling plays an important role in modern neuroscience research. Much previous research has relied on statistical methods, separately, to address two problems that are actually interdependent. First, given a particular computational model, Bayesian hierarchical techniques have been used to estimate individual variation in parameters over a population of subjects, leveraging their population-level distributions. Second, candidate models are themselves compared, and individual variation in the expressed model estimated, according to the fits of the models to each subject. The interdependence between these two problems arises because the relevant population for estimating parameters of a model depends on which other subjects express the model. Here, we propose a hierarchical Bayesian inference (HBI) framework for concurrent model comparison, parameter estimation and inference at the population level, combining previous approaches. We show that this framework has important advantages for both parameter estimation and model comparison theoretically and experimentally. The parameters estimated by the HBI show smaller errors compared to other methods. Model comparison by HBI is robust against outliers and is not biased towards overly simplistic models. Furthermore, the fully Bayesian approach of HBI enables researchers to quantify uncertainty in group parameter estimates, for each candidate model separately, and to perform statistical tests on parameters of a population.

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Species delimitation and hybridisation history of a hazel species complex

Annals of Botany ◽

10.1093/aob/mcab015 ◽

2021 ◽

Author(s):

Zhiqiang Lu ◽

Yongshuai Sun ◽

Ying Li ◽

Yongzhi Yang ◽

Gaini Wang ◽

...

Keyword(s):

Species Delimitation ◽

Species Complex ◽

Population Level ◽

Flowering Phenology ◽

The Other ◽

Genetic Composition ◽

Ssr Loci ◽

History Of ◽

Taxonomic Groups ◽

Taxonomic Studies

Abstract Background and Aims Hybridisation increases species adaptation and biodiversity but also obscures species boundaries. In this study, species delimitation and hybridisation history were examined within one Chinese hazel species complex (Corylus chinensis–Corylus fargesii). Two species including four varieties have already been described for this complex, with overlapping distributions. Methods A total of 322 trees from 44 populations of these four varieties across their ranges were sampled for morphological and molecular analyses. Climatic datasets based on 108 geographical locations were used to evaluate their niche differentiations. Flowering phenology was also observed for two co-occurring species or varieties. Key Results Four statistically different phenotypic clusters were revealed, but these clusters were highly inconsistent with the traditional taxonomic groups. All the clusters showed statistically distinct niches, with complete or partial geographic isolation. Only two clusters displayed a distributional overlap, but they had distinct flowering phenologies at the site where they co-occurred. Population-level evidence based on the genotypes of 10 simple sequence repeat (SSR) loci supported four phenotypic clusters. In addition, one cluster was shown to have an admixed genetic composition derived from the other three clusters through repeated historical hybridisations. Conclusions Based on our new evidence, it is better to treat the four clusters identified here as four independent species. One of them was shown to have an admixed genetic composition derived from the other threes through repeated historical hybridisations. This study highlights the importance of applying integrative and statistical methods to infer species delimitations and hybridisation history. Such a protocol should be adopted widely for future taxonomic studies.

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Game of webs: species and web structure influence contest outcome in black widow spiders

Behavioral Ecology ◽

10.1093/beheco/arz153 ◽

2019 ◽

Vol 31 (1) ◽

pp. 32-42 ◽

Cited By ~ 1

Author(s):

Cameron Jones ◽

Lea Pollack ◽

Nicholas DiRienzo

Keyword(s):

Individual Variation ◽

Native Species ◽

Interspecific Interactions ◽

Population Level ◽

Black Widow ◽

Trait Variation ◽

Web Structure ◽

Contest Outcome ◽

Black Widow Spiders ◽

The Web

Abstract Population-level trait variation within species plays an often-overlooked role in interspecific interactions. In this study, we compared among-individual variation in web phenotype and foraging behavior between native black widows (Latrodectus hesperus) and invasive brown widows (Latrodectus geometricus). We staged repeated contests whereby native widows defended their webs against intruders of both species to 1) investigate how trait variation mediates web contest outcome among native widows and 2) see whether widow behavior differs in response to an invasive spider. In only one trait, the average number of foraging lines, did black widows differ from brown widows. Black widow residents that built more structural lines were more likely to successfully defend their webs from conspecific intruders (i.e., be the sole spider remaining on the web postinteraction). This association between web structure and contest outcome did not exist in trials between black widows and invasive brown widows; however, in interspecific interactions, these same residents were more likely to have intruders remain on the web rather than drive them away. Surprisingly, brown widows did not usurp black widows. Brown widows were never observed signaling, yet black widow residents signaled equally to intruders of both species. Our results suggest that among-individual variation among native species can influence the response toward invasive competitors and outcome of these interactions.

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A comparison of sex, morphology, physiology and behavior of black-capped chickadees trapped using two common capture methods

PeerJ ◽

10.7717/peerj.10037 ◽

2020 ◽

Vol 8 ◽

pp. e10037

Author(s):

Sara M. Burns ◽

Frances Bonier

Keyword(s):

Individual Variation ◽

Behavioral Response ◽

Population Level ◽

Sampling Bias ◽

Sample Mean ◽

Novel Object ◽

Biological Studies ◽

Audio Stimulus ◽

Capture Techniques ◽

Selection Of

Many biological studies require the capture of individuals for sampling, for example for measurement of morphological or physiological traits, or for marking individuals for later observations. Capture methods employed often vary both within and between studies, and these differing methods could be more or less effective in capture of different individuals based on their morphology or behavior. If individuals that are prone to capture by the selected method differ with respect to traits of interest, such sampling bias could generate misleading or simply inaccurate results. The selection of capture methods could introduce two different forms of sampling bias, with the individuals that are sampled differing from the population at large or with individuals sampled via one method differing from individuals that could be sampled using a different method. We investigated this latter form of sampling bias by comparing individual birds sampled using two common capture techniques. We caught free-ranging black-capped chickadees (Poecile atricapillus) using walk-in traps baited with seed and mist nets paired with playback of an audio stimulus (conspecific mobbing calls). We measured 18 traits that we expect might vary among birds that are trappable by these differing methods—one that targets birds that are food motivated and potentially less neophobic and another that targets birds that respond readily to a perceived predation risk. We found no differences in the sex, morphology, initial and stress-induced corticosterone concentrations, behavioral response to a novel object, or behavioral response to a predator between individuals captured by these two methods. Individual variation in the behavioral response to a novel object was greater among birds caught by mist nets, suggesting this method might provide a sample that better reflects population-level individual variation. We do not know if the birds caught by these two methods provide a representative sample of the population at large, but can conclude that selection of either of these two common capture methods can similarly sample mean trait values of a population of interest. To accurately assess individual variation, particularly in behavior, mist nets might be preferable.

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