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18 Mar 2019
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Evaluating functional dispersal and its eco-epidemiological implications in a nest ectoparasite

Limited dispersal in a vector on territorial hosts

Recommended by based on reviews by Shelly Lachish and 1 anonymous reviewer

Parasitism requires parasites and hosts to meet and is therefore conditioned by their respective dispersal abilities. While dispersal has been studied in a number of wild vertebrates (including in relation to infection risk), we still have poor knowledge of the movements of their parasites. Yet we know that many parasites, and in particular vectors transmitting pathogens from host to host, possess the ability to move actively during at least part of their lives.
So... how far does a vector go – and is this reflected in the population structure of the pathogens they transmit? This is the question addressed by Rataud et al. [1], who provide the first attempt at using capture-mark-recapture to estimate not only functional dispersal, but also detection probability and survival in a wild parasite that is also a vector for other pathogens.
The authors find that (i) functional dispersal of soft ticks within a gull colony is very limited. Moreover, they observe unexpected patterns: (ii) experimental displacement of ticks does not induce homing behaviour, and (iii) despite lower survival, tick dispersal was lower in nests not containing hosts than in successful nests.
These results contrast with expectations based on the distribution of infectious agents. Low tick dispersal within the colony, combined with host territoriality during breeding and high site fidelity between years should result in a spatially structured distribution of infectious agents carried by ticks. This is not the case here. One possible explanation could be that soft ticks live for much longer than a breeding season, and that they disperse at other times of year to a larger extent than usually assumed.
This study represents one chapter of a story that will likely keep unfolding. It raises fascinating questions, and illustrates the importance of basic knowledge of parasite ecology and behaviour to better understand pathogen dynamics in the wild.

[1] Rataud A., Dupraz M., Toty C., Blanchon T., Vittecoq M., Choquet R. & McCoy K.D. (2019). Evaluating functional dispersal and its eco-epidemiological implications in a nest ectoparasite. Zenodo, 2592114. Ver. 3 peer-reviewed and recommended by PCI Ecology. doi: 10.5281/zenodo.2592114

Evaluating functional dispersal and its eco-epidemiological implications in a nest ectoparasiteAmalia Rataud, Marlène Dupraz, Céline Toty, Thomas Blanchon, Marion Vittecoq, Rémi Choquet, Karen D. McCoy<p>Functional dispersal (between-site movement, with or without subsequent reproduction) is a key trait acting on the ecological and evolutionary trajectories of a species, with potential cascading effects on other members of the local community. ...Dispersal & Migration, Epidemiology, Parasitology, Population ecologyAdele Mennerat2018-11-05 11:44:58 View
01 Feb 2020
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Evidence of tool use in a seabird?

Touchy matter: the delicate balance between Morgan’s canon and open-minded description of advanced cognitive skills in the animal

Recommended by ORCID_LOGO based on reviews by Valérie Dufour and Alex Taylor

In a recent paper published in PNAS, Fayet et al. [1] reported scarce field observations of two Atlantic puffins (four years apart) apparently scratching their bodies using sticks, which was interpreted by the authors as evidence of tool use in this species. In a short response, Benjamin Farrar [2] raises serious concerns about this interpretation and proposes simpler, more parsimonious, mechanisms explaining the observed behaviour: a textbook case of Morgan's canon.
In virtually all introductory lectures on animal behaviour, students are advised to exercise caution when interpreting empirical data and weighting alternative explanations. We are sometimes prisoner of our assumptions: our desire of beliefs in advanced cognitive skills in non-human species make us more receptive to facts confirming our preconceptions than to simpler, less exciting, interpretations (a phenomenon known as "confirmation bias" in psychology). We must resist the temptation to accept appealing explanations without enough critical thinking. Our students are thus taught to apply the Lloyd Morgan's canon, a variant of one of the most important heuristics in Science, the principle of parsimony or Occam's razor, rephrased by Morgan [3, page 53] in the context of animal behaviour: "In no case may we interpret an action as the outcome of a higher psychical faculty, if it can be interpreted as the outcome of the exercise of one that stands lower in the psychological scale". In absence of evidence to the contrary, one should postulate the simplest cognitive skill consistent with the observed behaviour. While sometimes criticized from an epistemological point of view [4-6], it remains an essential and largely accepted framework of animal cognition. It has repeatedly proved to be a useful guide in the minefield of comparative psychology. Classical ethology questions related to the existence of, for instance, meta-cognition [7], intentionality or problem solving [8] have been convincingly investigated using this principle.
Yet, there is a downside to this conservative approach. Blind reference to Morgan's canon may narrow our theoretical thinking about animal cognition [7,9]. It could be counter-productive to systematically deny advanced cognitive skills in animals. On the contrary, keeping our mind open to unplanned observations, unexpected discoveries, or serendipity [10], and being prepared to accept new hypotheses, sometimes fairly remote from the dominant paradigm, may be a fruitful research strategy. To quote Darwin's famous letter to Alfred Wallace: "I am a firm believer, that without speculation there is no good and original observation" [11]. Brief notes in specialized scientific journals, or even in grey literature (by enthusiast amateur ornithologists, ichthyologists, or entomologists), constitutes a rich array of anecdotal observations. For instance, Sol et al. [12] convincingly compared the innovation propensity across bird species by screening ornithology literature using keywords like 'never reported', 'not seen before', 'first report', 'unusual' or 'novel'. Even if "the plural of anecdote is not data" as the saying goes, such descriptions of novel behaviours, even single-subject observations, are indisputably precious: taxonomic ubiquity of a behaviour is a powerful argument in favour of evolutionary convergence. Of course, a race to the bottom, amplified by the inevitable media hypes around scientific articles questioning human exceptionalism, is another possible scientific trap for behavioural biologists in search of skills characteristic of so-called advanced species, but never described so far in supposedly cognitively simpler organisms. As stated by Franz de Waal [9]: "I have nothing against anecdotes, especially if they have been caught on camera or come from reputable observers who know their animals; but I do view them as a starting point of research, never an end point".
In the case of the two video observations of puffins apparently using sticks as scratching tool, it must be considered as a mere anecdote unless scientists systematically investigate this behaviour. In his constructive criticism of Fayet et al.'s paper, Benjamin Farrar [2] proposes interesting directions of research and testable predictions. A correlation between the background rate of stick picking and the rate of stick preening would indicate that this behaviour was more likely explained by fluke than genuine innovation in this species.


[1] Fayet, A. L., Hansen, E. S., and Biro, D. (2020). Evidence of tool use in a seabird. Proceedings of the National Academy of Sciences, 117(3), 1277–1279. doi: 10.1073/pnas.1918060117
[2] Farrar, B. G. (2020). Evidence of tool use in a seabird? PsyArXiv, 463hk, ver. 5 recommended and peer-reviewed by Peer Community In Ecology. doi: 10.31234/
[3] Morgan, C. L. (1894). An introduction to comparative psychology. London, UK: Walter Scott, Ltd. Retrieved from
[4] Meketa, I. (2014). A critique of the principle of cognitive simplicity in comparative cognition. Biology and Philosophy, 29(5), 731–745. doi: 10.1007/s10539-014-9429-z
[5] Fitzpatrick, S. (2017). Against Morgan's Canon. In K. Andrews and J. Beck (Eds.), The Routledge handbook of philosophy of animal minds (pp. 437–447). London, UK: Routledge, Taylor and Francis Group. doi: 10.4324/9781315742250.ch42
[6] Starzak, T. (2017). Interpretations without justification: a general argument against Morgan's Canon. Synthese, 194(5), 1681–1701. doi: 10.1007/s11229-016-1013-4
[7] Arbilly, M., and Lotem, A. (2017). Constructive anthropomorphism: a functional evolutionary approach to the study of human-like cognitive mechanisms in animals. Proceedings of the Royal Society B: Biological Sciences, 284(1865), 20171616. doi: 10.1098/rspb.2017.1616
[8] Taylor, A. H., Knaebe, B., and Gray, R. D. (2012). An end to insight? New Caledonian crows can spontaneously solve problems without planning their actions. Proceedings of the Royal Society B: Biological Sciences, 279(1749), 4977–4981. doi: 10.1098/rspb.2012.1998
[9] de Waal, F. (2016). Are we smart enough to know how smart animals are? New-York, USA: W. W. Norton and Company.
[10] Scheffer, M. (2014). The forgotten half of scientific thinking. Proceedings of the National Academy of Sciences, 111(17), 6119–6119. doi: 10.1073/pnas.1404649111
[11] Darwin, C. R. (1857). Letter to A. R. Wallace, 22 December 1857. Retrieved 30 January 2020, from
[12] Sol, D., Lefebvre, L., and Rodríguez-Teijeiro, J. D. (2005). Brain size, innovative propensity and migratory behaviour in temperate Palaearctic birds. Proceedings of the Royal Society B: Biological Sciences, 272(1571), 1433–1441. doi: 10.1098/rspb.2005.3099

Evidence of tool use in a seabird?Benjamin G. FarrarFayet, Hansen and Biro (1) provide two observations of Atlantic puffins, *Fratercula arctica*, performing self-directed actions while holding a stick in their beaks. The authors interpret this as evidence of tool use as they suggest that the stick...Behaviour & EthologyFrancois-Xavier Dechaume-Moncharmont2020-01-22 11:55:27 View
24 May 2023
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Evolutionary determinants of reproductive seasonality: a theoretical approach

When does seasonal reproduction evolve?

Recommended by ORCID_LOGO based on reviews by Francois-Xavier Dechaume-Moncharmont, Nigel Yoccoz and 1 anonymous reviewer

Have you ever wondered why some species breed seasonally while others do not? You might think it is all down to lattitude and the harshness of winters but it turns out it is quite a bit more complicated than that. A consequence of this is that climate change may result in the evolution of the degree of seasonal reproduction, with some species perhaps becoming less seasonal and others more so even in the same habitat. 

Burtschell et al. (2023) investigated how various factors influence seasonal breeding by building an individual-based model of a baboon population from which they calculated the degree of seasonality for the fittest reproductive strategy. They then altered key aspects of their model to examine how these changes impacted the degree of seasonality in the reproductive strategy. What they found is fascinating. 

The degree of seasonality in reproductive strategy is expected to increase with increased seasonality in the environment, decreased food availability, increased energy expenditure, and how predictable resource availability is. Interestingly, neither female cycle length nor extrinsic infant mortality influenced the degree of seasonality in reproduction.

What this means in reality for seasonal species is more challenging to understand. Some environments appear to be becoming more seasonal yet less predictable, and some species appear to be altering their daily energy budgets in response to changing climate in quite complex ways. As with pretty much everything in biology, Burtschell et al.'s work reveals much nuance and complexity, and that predicting how species might alter their reproductive timing is fraught with challenges.

The paper is very well written. With a simpler model it may have proven possible to achieve analytical solutions, but this is a very minor gripe. The reviewers were positive about the paper, and I have little doubt it will be well-cited. 


Burtschell L, Dezeure J, Huchard E, Godelle B (2023) Evolutionary determinants of reproductive seasonality: a theoretical approach. bioRxiv, 2022.08.22.504761, ver. 2 peer-reviewed and recommended by Peer Community in Ecology.

Evolutionary determinants of reproductive seasonality: a theoretical approachLugdiwine Burtschell, Jules Dezeure, Elise Huchard, Bernard Godelle<p style="text-align: justify;">Reproductive seasonality is a major adaptation to seasonal cycles and varies substantially among organisms. This variation, which was long thought to reflect a simple latitudinal gradient, remains poorly understood ...Evolutionary ecology, Life history, Theoretical ecologyTim Coulson Nigel Yoccoz2022-08-23 21:37:28 View
03 Jun 2022
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Evolutionary emergence of alternative stable states in shallow lakes

How to evolve an alternative stable state

Recommended by ORCID_LOGO based on reviews by Jean-François Arnoldi and 1 anonymous reviewer

Alternative stable states describe ecosystems that can persist in more than one configuration. An ecosystem can shift between stable states following some form of perturbation. There has been much work on predicting when ecosystems will shift between stable states, but less work on why some ecosystems are able to exist in alternative stable states in the first place. The paper by Ardichvili, Loeuille, and Dakos (2022) addresses this question using a simple model of a shallow lake. Their model is based on a trade-off between access to light and nutrient availability in the water column, two essential resources for the macrophytes they model. They then identify conditions when the ancestral macrophyte will diversify resulting in macrophyte species living at new depths within the lake. The authors find a range of conditions where alternative stable states can evolve, but the range is narrow. Nonetheless, their model suggests that for alternative stable states to exist, one requirement is for there to be asymmetric competition between competing species, with one species being a better competitor on one limiting resource, with the other being a better competitor on a second limiting resource. 

These results are interesting and add to growing literature on how asymmetric competition can aid species coexistence. Asymmetric competition may be widespread in nature, with closely related species often being superior competitors on different resources. Incorporating asymmetric competition, and its evolution, into models does complicate theoretical investigations, but Ardichvili, Loeuille, and Dakos’ paper elegantly shows how substantial progress can be made with a model that is still (relatively) simple.


Ardichvili A, Loeuille N, Dakos V (2022) Evolutionary emergence of alternative stable states in shallow lakes. bioRxiv, 2022.02.23.481597, ver. 3 peer-reviewed and recommended by Peer Community in Ecology.

Evolutionary emergence of alternative stable states in shallow lakesAlice Ardichvili, Nicolas Loeuille, Vasilis Dakos<p style="text-align: justify;">Ecosystems under stress may respond abruptly and irreversibly through tipping points. Although much is explored on the mechanisms that affect tipping points and alternative stable states, little is known on how ecos...Community ecology, Competition, Eco-evolutionary dynamics, Theoretical ecologyTim Coulson2022-03-01 10:54:05 View
15 Jul 2023
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Evolution of dispersal and the maintenance of fragmented metapopulations

The spatial dynamics of habitat fragmentation drives the evolution of dispersal and metapopulation persistence

Recommended by based on reviews by Eva Kisdi, David Murray-Stoker, Shripad Tuljapurkar and 1 anonymous reviewer

​​​​​The persistence of populations facing the destruction of their habitat is a multifaceted question that has mobilized theoreticians and empiricists alike for decades. As an ecological question, persistence has been studied as the spatial rescue of populations via dispersal into remaining suitable habitats. The spatial aggregation of habitat destruction has been a key component of these studies, and it has been applied to the problem of coexistence by integrating competition-colonization tradeoffs. There is a rich ecological literature on this topic, both from theoretical and field studies (Fahrig 2003). The relationship between life-history strategies of species and their resilience to spatially structured habitat fragmentation is also an important component of conservation strategies through the management of land use, networks of protected areas, and the creation of corridors. In the context of environmental change, the ability of species to adapt to changes in landscape configuration and availability can be treated as an eco-evolutionary process by considering the possibility of evolutionary rescue (Heino and Hanski 2001; Bell 2017). However, eco-evolutionary dynamics considering spatially structured changes in landscapes and life-history tradeoffs remains an outstanding question. Finand et al. (2023) formulate the problem of persistence in fragmented landscapes over evolutionary time scales by studying models for the evolution of dispersal in relation to habitat fragmentation and spatial aggregation. Their simulations were conducted on a spatial grid where individuals can colonize suitable patch as a function of their competitive rank that decreases as a function of their (ii) dispersal distance trait. Simulations were run under fixed habitat fragmentation (proportion of unsuitable habitat) and aggregation, and with an explicit rate of habitat destruction to study evolutionary rescue.

Their results reveal a balance between the selection for high dispersal under increasing habitat fragmentation and selection for lower dispersal in response to habitat aggregation. This balance leads to the coexistence of polymorphic dispersal strategies in highly aggregated landscapes with low fragmentation where high dispersers inhabit aggregated habitats while low dispersers are found in isolated habitats. The authors then integrate the spatial rescue mechanism to the problem of evolutionary rescue in response to temporally increasing fragmentation. There they show how rapid evolution allows for evolutionary rescue through the evolution of high dispersal. They also show the limits to this evolutionary rescue to cases where both aggregation and fragmentation are not too high. Interestingly, habitat aggregation prevents evolutionary rescue by directly affecting the evolutionary potential of dispersal. The study is based on simple scenarios that ignore the complexity of relationships between dispersal, landscape properties, and species interactions. This simplicity is the strength of the study, revealing basic mechanisms that can now be tested against other life-history tradeoffs and species interactions. Finand et al. (2023) provide a novel foundation for the study of eco-evolutionary dynamics in metacommunities exposed to spatially structured habitat destruction. They point to important assumptions that must be made along the way, including the relationships between dispersal distance and fecundity (they assume a positive relationship), and the nature of life-history tradeoffs between dispersal rate and local competitive abilities. 


Bell, G. 2017. Evolutionary Rescue. Annual Review of Ecology, Evolution, and Systematics 48:605–627. 
Fahrig, L. 2003. Effects of Habitat Fragmentation on Biodiversity. Annual Review of Ecology, Evolution, and Systematics 34:487–515. 
Finand, B., T. Monnin, and N. Loeuille. 2023. Evolution of dispersal and the maintenance of fragmented metapopulations. bioRxiv, 2022.06.08.495260, ver. 3 peer-reviewed and recommended by Peer Community in Ecology. 
Heino, M., and I. Hanski. 2001. Evolution of Migration Rate in a Spatially Realistic Metapopulation Model. The American Naturalist 157:495–511.

Evolution of dispersal and the maintenance of fragmented metapopulationsBasile Finand, Thibaud Monnin, Nicolas Loeuille<p>Because it affects dispersal risk and modifies competition levels, habitat fragmentation directly constrains dispersal evolution. When dispersal is traded-off against competitive ability, increased fragmentation is often expected to select high...Colonization, Competition, Dispersal & Migration, Eco-evolutionary dynamics, Spatial ecology, Metacommunities & Metapopulations, Theoretical ecologyFrédéric Guichard2022-06-10 13:51:15 View
26 Apr 2021
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Experimental test for local adaptation of the rosy apple aphid (Dysaphis plantaginea) during its recent rapid colonization on its cultivated apple host (Malus domestica) in Europe

A planned experiment on local adaptation in a host-parasite system: is adaptation to the host linked to its recent domestication?

Recommended by based on reviews by Sharon Zytynska, Alex Stemmelen and 1 anonymous reviewer

Local adaptation shall occur whenever selective pressures vary across space and overwhelm the effects of gene flow and local extinctions (Kawecki and Ebert 2004). Because the intimate interaction that characterizes their relationship exerts a strong selective pressure on both partners, host-parasite systems represent a classical example in which local adaptation is expected from rapidly evolving parasites adapting to more evolutionary constrained hosts (Kaltz and Shykoff 1998). Such systems indeed represent a large proportion of the study-cases in local adaptation research (Runquist et al. 2020). Biotic interactions intervene in many environment-related societal challenges, so that understanding when and how local adaptation arises is important not only for understanding evolutionary dynamics but also for more applied questions such as the control of agricultural pests, biological invasions, or pathogens (Parker and Gilbert 2004).

The exact conditions under which local adaptation does occur and can be detected is however still the focus of many theoretical, methodological and empirical studies (Blanquart et al. 2013, Hargreaves et al. 2020, Hoeksema and Forde 2008, Nuismer and Gandon 2008, Richardson et al. 2014). A recent review that evaluates investigations that examined the combined influence of biotic and abiotic factors on local adaptation reaches partial conclusions about their relative importance in different contexts and underlines the many traps that one has to avoid in such studies (Runquist et al. 2020). The authors of this review emphasize that one should evaluate local adaptation using wild-collected strains or populations and over multiple generations, on environmental gradients that span natural ranges of variation for both biotic and abiotic factors, in a theory-based hypothetico-deductive framework that helps interpret the outcome of experiments. These multiple targets are not easy to reach in each local adaptation experiment given the diversity of systems in which local adaptation may occur. Improving research practices may also help better understand when and where local adaptation does occur by adding controls over p-hacking, HARKing or publication bias, which is best achieved when hypotheses, date collection and analytical procedures are known before the research begins (Chambers et al. 2014). In this regard, the route taken by Olvera-Vazquez et al. (2021) is interesting. They propose to investigate whether the rosy aphid (Dysaphis plantaginea) recently adapted to its cultivated host, the apple tree (Malus domestica), and chose to pre-register their hypotheses and planned experiments on PCI Ecology (Peer Community In 2020). Though not fulfilling all criteria mentioned by Runquist et al. (2020), they clearly state five hypotheses that all relate to the local adaptation of this agricultural pest to an economically important fruit tree, and describe in details a powerful, randomized experiment, including how data will be collected and analyzed. The experimental set-up includes comparisons between three sites located along a temperature transect that also differ in local edaphic and biotic factors, and contrasts wild and domesticated apple trees that originate from the three sites and were both planted in the local, sympatric site, and transplanted to allopatric sites. Beyond enhancing our knowledge on local adaptation, this experiment will also test the general hypothesis that the rosy aphid recently adapted to Malus sp. after its domestication, a question that population genetic analyses was not able to answer (Olvera-Vazquez et al. 2020).


Blanquart F, Kaltz O, Nuismer SL, Gandon S (2013) A practical guide to measuring local adaptation. Ecology Letters, 16, 1195–1205.

Briscoe Runquist RD, Gorton AJ, Yoder JB, Deacon NJ, Grossman JJ, Kothari S, Lyons MP, Sheth SN, Tiffin P, Moeller DA (2019) Context Dependence of Local Adaptation to Abiotic and Biotic Environments: A Quantitative and Qualitative Synthesis. The American Naturalist, 195, 412–431.

Chambers CD, Feredoes E, Muthukumaraswamy SD, Etchells PJ, Chambers CD, Feredoes E, Muthukumaraswamy SD, Etchells PJ (2014) Instead of “playing the game” it is time to change the rules: Registered Reports at <em>AIMS Neuroscience</em> and beyond. AIMS Neuroscience, 1, 4–17.

Hargreaves AL, Germain RM, Bontrager M, Persi J, Angert AL (2019) Local Adaptation to Biotic Interactions: A Meta-analysis across Latitudes. The American Naturalist, 195, 395–411.

Hoeksema JD, Forde SE (2008) A Meta‐Analysis of Factors Affecting Local Adaptation between Interacting Species. The American Naturalist, 171, 275–290.

Kaltz O, Shykoff JA (1998) Local adaptation in host–parasite systems. Heredity, 81, 361–370.

Kawecki TJ, Ebert D (2004) Conceptual issues in local adaptation. Ecology Letters, 7, 1225–1241.

Nuismer SL, Gandon S (2008) Moving beyond Common‐Garden and Transplant Designs: Insight into the Causes of Local Adaptation in Species Interactions. The American Naturalist, 171, 658–668.

Olvera-Vazquez SG, Remoué C, Venon A, Rousselet A, Grandcolas O, Azrine M, Momont L, Galan M, Benoit L, David G, Alhmedi A, Beliën T, Alins G, Franck P, Haddioui A, Jacobsen SK, Andreev R, Simon S, Sigsgaard L, Guibert E, Tournant L, Gazel F, Mody K, Khachtib Y, Roman A, Ursu TM, Zakharov IA, Belcram H, Harry M, Roth M, Simon JC, Oram S, Ricard JM, Agnello A, Beers EH, Engelman J, Balti I, Salhi-Hannachi A, Zhang H, Tu H, Mottet C, Barrès B, Degrave A, Razmjou J, Giraud T, Falque M, Dapena E, Miñarro M, Jardillier L, Deschamps P, Jousselin E, Cornille A (2020) Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North Africa. bioRxiv, 2020.12.11.421644.

Olvera-Vazquez S.G., Alhmedi A., Miñarro M., Shykoff J. A., Marchadier E., Rousselet A., Remoué C., Gardet R., Degrave A. , Robert P. , Chen X., Porcher J., Giraud T., Vander-Mijnsbrugge K., Raffoux X., Falque M., Alins, G., Didelot F., Beliën T., Dapena E., Lemarquand A. and Cornille A. (2021) Experimental test for local adaptation of the rosy apple aphid (Dysaphis plantaginea) to its host (Malus domestica) and to its climate in Europe. In principle recommendation by Peer Community In Ecology., ver. 4.

Parker IM, Gilbert GS (2004) The Evolutionary Ecology of Novel Plant-Pathogen Interactions. Annual Review of Ecology, Evolution, and Systematics, 35, 675–700.

Peer Community In. (2020, January 15). Submit your preregistration to Peer Community In for peer review.

Richardson JL, Urban MC, Bolnick DI, Skelly DK (2014) Microgeographic adaptation and the spatial scale of evolution. Trends in Ecology & Evolution, 29, 165–176.

Experimental test for local adaptation of the rosy apple aphid (Dysaphis plantaginea) during its recent rapid colonization on its cultivated apple host (Malus domestica) in EuropeOlvera-Vazquez S.G., Alhmedi A., Miñarro M., Shykoff J. A., Marchadier E., Rousselet A., Remoué C., Gardet R., Degrave A. , Robert P. , Chen X., Porcher J., Giraud T., Vander-Mijnsbrugge K., Raffoux X., Falque M., Alins, G., Didelot F., Beliën T.,...<p style="text-align: justify;">Understanding the extent of local adaptation in natural populations and the mechanisms enabling populations to adapt to their environment is a major avenue in ecology research. Host-parasite interaction is widely se...Evolutionary ecology, PreregistrationsEric Petit2020-07-26 18:31:42 View
12 Apr 2023
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Feeding and growth variations affect δ13C and δ15N budgets during ontogeny in a lepidopteran larva

Refining our understanding how nutritional conditions affect 13C and 15N isotopic fractionation during ontogeny in a herbivorous insect

Recommended by based on reviews by Anton Potapov and 1 anonymous reviewer

Using stable isotope fractionation to disentangle and understand the trophic positions of animals within the food webs they are embedded within has a long tradition in ecology (Post, 2002; Scheu, 2002). Recent years have seen increasing application of the method with several recent reviews summarizing past advancements in this field (e.g. Potapov et al., 2019; Quinby et al., 2020).

In their new manuscript, Charberet and colleagues (2023) set out to refine our understanding of the processes that lead to nitrogen and carbon stable isotope fractionation by investigating how herbivorous insect larvae (specifically, the noctuid moth Spodoptera littoralis) respond to varying nutritional conditions (from starving to ad libitum feeding) in terms of stable isotopes enrichment. Though the underlying mechanisms have been experimentally investigated before in terrestrial invertebrates (e.g. in wolf spiders; Oelbermann & Scheu, 2002), the elegantly designed and adequately replicated experiments by Charberet and colleagues add new insights into this topic. Particularly, the authors provide support for the hypotheses that (A) 15N is disproportionately accumulated under fast growth rates (i.e. when fed ad libitum) and that (B) 13C is accumulated under low growth rates and starvation due to depletion of 13C-poor fat tissues. Applying this knowledge to field samples where feeding conditions are usually not known in detail is not straightforward, but the new findings could still help better interpretation of field data under specific conditions that make starvation for herbivores much more likely (e.g. droughts).

Overall this study provides important methodological advancements for a better understanding of plant-herbivore interactions in a changing world.


Charberet, S., Maria, A., Siaussat, D., Gounand, I., & Mathieu, J. (2023). Feeding and growth variations affect δ13C and δ15N budgets during ontogeny in a lepidopteran larva. bioRxiv, ver. 3 peer-reviewed and recommended by Peer Community in Ecology.

Oelbermann, K., & Scheu, S. (2002). Stable Isotope Enrichment (δ 15N and δ 13C) in a Generalist Predator (Pardosa lugubris, Araneae: Lycosidae): Effects of Prey Quality. Oecologia, 130(3), 337–344.

Post, D. M. (2002). Using stable isotopes to estimate trophic position: Models, methods, and assumptions. Ecology, 83(3), 703–718.[0703:USITET]2.0.CO;2

Potapov, A. M., Tiunov, A. V., & Scheu, S. (2019). Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition. Biological Reviews, 94(1), 37–59.

Quinby, B. M., Creighton, J. C., & Flaherty, E. A. (2020). Stable isotope ecology in insects: A review. Ecological Entomology, 45(6), 1231–1246.

Scheu, S. (2002). The soil food web: Structure and perspectives. European Journal of Soil Biology, 38(1), 11–20.

Feeding and growth variations affect δ13C and δ15N budgets during ontogeny in a lepidopteran larvaSamuel M. Charberet, Annick Maria, David Siaussat, Isabelle Gounand, Jérôme Mathieu<p style="text-align: justify;">Isotopes are widely used in ecology to study food webs and physiology. The fractionation observed between trophic levels in nitrogen and carbon isotopes, explained by isotopic biochemical selectivity, is subject to ...Experimental ecology, Food webs, PhysiologyGregor Kalinkat2022-11-16 15:23:31 View
14 May 2019
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Field assessment of precocious maturation in salmon parr using ultrasound imaging

OB-GYN for salmon parrs

Recommended by ORCID_LOGO based on reviews by Hervé CAPRA and 1 anonymous reviewer

Population dynamics and stock assessment models are only as good as the data used to parameterise them. For Atlantic salmon (Salmo salar) populations, a critical parameter may be frequency of precocious maturation. Indeed, the young males (parrs) that mature early, before leaving the river to reach the ocean, can contribute to reproduction but have much lower survival rates afterwards. The authors cite evidence of the potentially major consequences of this alternate reproductive strategy. So, to be parameterised correctly, it needs to be assessed correctly. Cue the ultrasound machine.

Through a thorough analysis of data collected on 850 individuals [1], over three years, the authors clearly show that the non-invasive examination of the internal cavity of young fishes to look for gonads, using a portable ultrasound machine, provides reliable and replicable evidence of precocious maturation. They turned into OB-GYN for salmons (albeit for male salmons!) and it worked. While using ultrasounds to detect fish gonads is not a new idea (early attempts for salmonids date back to the 80s [2]), the value here is in the comparison with the classic visual inspection technique (which turns out to be less reliable) and the fact that ultrasounds can now easily be carried out in the field.

Beyond the potentially important consequences of this new technique for the correct assessment of salmon population dynamics, the authors also make the case for the acquisition of more reliable individual-level data in ecological studies, which I applaud.


[1] Nevoux M, Marchand F, Forget G, Huteau D, Tremblay J, and Destouches J-P. (2019). Field assessment of precocious maturation in salmon parr using ultrasound imaging. bioRxiv 425561, ver. 3 peer-reviewed and recommended by PCI Ecology. doi: 10.1101/425561
[2] Reimers E, Landmark P, Sorsdal T, Bohmer E, Solum T. (1987). Determination of salmonids’ sex, maturation and size: an ultrasound and photocell approach. Aquaculture Magazine.13:41-44.

Field assessment of precocious maturation in salmon parr using ultrasound imagingMarie Nevoux, Frédéric Marchand, Guillaume Forget, Dominique Huteau, Julien Tremblay, Jean-Pierre Destouches<p>Salmonids are characterized by a large diversity of life histories, but their study is often limited by the imperfect observation of the true state of an individual in the wild. Challenged by the need to reduce uncertainty of empirical data, re...Conservation biology, Demography, Experimental ecology, Freshwater ecology, Life history, Phenotypic plasticity, Population ecologyJean-Olivier Irisson2018-09-25 17:24:59 View
14 Jul 2023
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Field margins as substitute habitat for the conservation of birds in agricultural wetlands

Searching for conservation opportunities at the margins

Recommended by ORCID_LOGO based on reviews by Scott Wilson and Elena D Concepción

In a progressively human-dominated planet (Venter et al., 2016), the fate of many species will depend on the extent to which they can persist in anthropogenic landscapes. In Western Europe, where only small areas of primary habitat remain (e.g. Sabatini et al., 2018), semi-natural areas are crucial habitats to many native species, yet they are threatened by the expansion of human activities, including agricultural expansion and intensification (Rigal et al., 2023). 

A new study by Mallet and colleagues (Mallet et al., 2023) investigates the extent to which bird species in the Camargue region are able to use the margins of agricultural fields as substitutes for their preferred semi-natural habitats. Located in the delta of the Rhône River in Southern France, the Camargue is internationally recognized for its biodiversity value, classified as a Biosphere Reserve by UNESCO and as a Wetland of International Importance under the Ramsar Convention (IUCN & UN-WCMC, 2023). Mallet and colleagues tested three specific hypotheses: that grass strips (grassy field boundaries, including grassy tracks or dirt roads used for moving agricultural machinery) can function as substitute habitats for grassland species; that reed strips along drainage ditches (common in the rice paddy landscapes of the Camargue) can function as substitute habitats to wetland species; and that hedgerows can function as substitute habitats to species that favour woodland edges. They did so by measuring how the local abundances of 14 bird species (nine typical of forest edges, 3 of grasslands, and two of reedbeds) respond to increasing coverage of either the three types of field margins or of the three types of semi-natural habitat. 

This is an elegant study design, yet – as is often the case with real field data – results are not as simple as expected. Indeed, for most species (11 out of 14) local abundances did not increase significantly with the area of their supposed primary habitat, undermining the assumption that they are strongly associated with (or dependent on) those habitats. Among the three species that did respond positively to the area of their primary habitat, one (a forest edge species) responded positively but not significantly to the area of field margins (hedgerows), providing weak evidence to the habitat compensation hypothesis. For the other two (grassland and a wetland species), abundance responded even more strongly to the area of field margins (grass and reed strips, respectively) than to the primary habitat, suggesting that the field margins are not so much a substitute but valuable habitats in their own right. 

It would have been good conservation news if field margins were found to be suitable habitat substitutes to semi-natural habitats, or at least reasonable approximations, to most species. Given that these margins have functional roles in agricultural landscapes (marking boundaries, access areas, water drainage), they could constitute good win-win solutions for reconciling biodiversity conservation with agricultural production. Alas, the results are more complicated than that, with wide variation in species responses that could not have been predicted from presumed habitat affinities. These results illustrate the challenges of conservation practice in complex landscapes formed by mosaics of variable land use types. With species not necessarily falling neatly into habitat guilds, it becomes even more challenging to plan strategically how to manage landscapes to optimize their conservation. The results presented here suggest that species’ abundances may be responding to landscape variables not taken into account in the analyses, such as connectivity between habitat patches, or maybe positive and negative edge effects between land use types. That such uncertainties remain even in a well-studied region as the Camargue, and for such a well-studied taxon such as birds, only demonstrates the continued importance of rigorous field studies testing explicit hypotheses such as this one by Mallet and colleagues. 


IUCN, & UN-WCMC (2023). Protected Planet. Protected Planet. 

Mallet, P., Béchet, A., Sirami, C., Mesléard, F., Blanchon, T., Calatayud, F., Dagonet, T., Gaget, E., Leray, C., & Galewski, T. (2023). Field margins as substitute habitat for the conservation of birds in agricultural wetlands. bioRxiv, 2022.05.05.490780, ver. 3 peer-reviewed and recommended by Peer Community in Ecology. 

Rigal, S., Dakos, V., Alonso, H., Auniņš, A., Benkő, Z., Brotons, L., Chodkiewicz, T., Chylarecki, P., de Carli, E., del Moral, J. C. et al. (2023). Farmland practices are driving bird population decline across Europe. Proceedings of the National Academy of Sciences, 120, e2216573120. 

Sabatini, F. M., Burrascano, S., Keeton, W. S., Levers, C., Lindner, M., Pötzschner, F., Verkerk, P. J., Bauhus, J., Buchwald, E., Chaskovsky, O., Debaive, N. et al. (2018). Where are Europe’s last primary forests? Diversity and Distributions, 24, 1426–1439. 

Venter, O., Sanderson, E. W., Magrach, A., Allan, J. R., Beher, J., Jones, K. R., Possingham, H. P., Laurance, W. F., Wood, P., Fekete, B. M., Levy, M. A., & Watson, J. E. M. (2016). Sixteen years of change in the global terrestrial human footprint and implications for biodiversity conservation. Nature Communications, 7, 12558. 

Field margins as substitute habitat for the conservation of birds in agricultural wetlandsMallet Pierre, Béchet Arnaud, Sirami Clélia, Mesléard François, Blanchon Thomas, Calatayud François, Dagonet Thomas, Gaget Elie, Leray Carole, Galewski Thomas<p style="text-align: justify;">Breeding birds in agricultural landscapes have declined considerably since the 1950s and the beginning of agricultural intensification in Europe. Given the increasing pressure on agricultural land, it is necessary t...Agroecology, Biodiversity, Conservation biology, Landscape ecologyAna S. L. Rodrigues2022-05-09 10:48:49 View
24 Jan 2023
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Four decades of phenology in an alpine amphibian: trends, stasis, and climatic drivers

Alpine ecology and their dynamics under climate change

Recommended by based on reviews by Nigel Yoccoz and 1 anonymous reviewer

​​Research about the effects of climate change on ecological communities has been abundant in the last decades. In particular, studies about the effects of climate change on mountain ecosystems have been key for understanding and communicating the consequences of this global phenomenon. Alpine regions show higher increases in warming in comparison to low-altitude ecosystems and this trend is likely to continue. This warming has caused reduced snowfall and/or changes in the duration of snow cover. For example, Notarnicola (2020) reported that 78% of the world’s mountain areas have experienced a snow cover decline since 2000. In the same vein, snow cover has decreased by 10% compared with snow coverage in the late 1960s (Walther et al., 2002) and snow cover duration has decreased at a rate of 5 days/decade (Choi et al., 2010). These changes have impacted the dynamics of high-altitude plant and animal populations. Some impacts are changes in the hibernation of animals, the length of the growing season for plants and the soil microbial composition (Chávez et al. 2021).

Lenzi et al. (2023), give us an excellent study using long-term data on alpine amphibian populations. Authors show how climate change has impacted the reproductive phenology of Bufo bufo, especially the breeding season starts 30 days earlier than ~40 years ago. This earlier breeding is associated with the increasing temperatures and reduced snow cover in these alpine ecosystems. However, these changes did not occur in a linear trend but a marked acceleration was observed until mid-1990s with a later stabilization. Authors associated these nonlinear changes with complex interactions between the global trend of seasonal temperatures and site-specific conditions. 

Beyond the earlier breeding season, changes in phenology can have important impacts on the long-term viability of alpine populations. Complex interactions could involve positive and negative effects like harder environmental conditions for propagules, faster development of juveniles, or changes in predation pressure. This study opens new research opportunities and questions like the urgent assessment of the global impact of climate change on animal fitness. This study provides key information for the conservation of these populations.


Chávez RO, Briceño VF, Lastra JA, Harris-Pascal D, Estay SA (2021) Snow Cover and Snow Persistence Changes in the Mocho-Choshuenco Volcano (Southern Chile) Derived From 35 Years of Landsat Satellite Images. Frontiers in Ecology and Evolution, 9.

Choi G, Robinson DA, Kang S (2010) Changing Northern Hemisphere Snow Seasons. Journal of Climate, 23, 5305–5310.

Lenzi O, Grossenbacher K, Zumbach S, Lüscher B, Althaus S, Schmocker D, Recher H, Thoma M, Ozgul A, Schmidt BR (2022) Four decades of phenology in an alpine amphibian: trends, stasis, and climatic drivers.bioRxiv, 2022.08.16.503739, ver. 3 peer-reviewed and recommended by Peer Community in Ecology.

Notarnicola C (2020) Hotspots of snow cover changes in global mountain regions over 2000–2018. Remote Sensing of Environment, 243, 111781.

Four decades of phenology in an alpine amphibian: trends, stasis, and climatic driversOmar Lenzi, Kurt Grossenbacher, Silvia Zumbach, Beatrice Luescher, Sarah Althaus, Daniela Schmocker, Helmut Recher, Marco Thoma, Arpat Ozgul, Benedikt R. Schmidt<p style="text-align: justify;">Strong phenological shifts in response to changes in climatic conditions have been reported for many species, including amphibians, which are expected to breed earlier. Phenological shifts in breeding are observed i...Climate change, Population ecology, ZoologySergio EstayAnonymous, Nigel Yoccoz2022-08-18 08:25:21 View