Editorial: Allee effects in ecology and evolution

Kramer, Andrew M.; Berec, Luděk; Drake, John M.

doi:10.1111/1365-2656.12777

Cited by 43 publications

(37 citation statements)

References 32 publications

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“…Attraction to conspecifics in phoretic nematodes might also arise to avoid the impact of Allee effects (i.e. decreased fitness due to low population density at the destination) as proposed in other species (Clotuche et al., 2013; Courchamp et al., 1999; Fronhofer et al., 2013; Kramer et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Hopping on: Conspecific traveller density within a vehicle regulates parasitic hitchhiking between ephemeral microcosms

Gupta

Borges

2021

Journal of Animal Ecology

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Hitchhikers (phoretic organisms) identify their vehicles using species‐specific visual, chemical and vibrational cues. However, what factors influence their choice between vehicles of the same species has rarely been investigated. Hitchhikers must not only avoid overcrowded vehicles but may also need to travel with conspecifics to ensure mates at their destination. Hence, a trade‐off between overcrowding and presence of conspecifics likely determines the choice of a vehicle especially when destination sites are distant, ephemeral and unique. Here, we investigate whether a trade‐off between the presence of conspecifics versus overcrowding by conspecifics or heterospecifics on a vehicle affects hitchhiker choice. We also investigate the sensory modality responsible for this choice. We experimentally examine these questions using a phoretic nematode community (containing plant‐ and animal‐parasitic taxa) obligately associated with a brood‐site pollination mutualism. In this model system, nematodes co‐travel with conspecifics and heterospecifics on pollinators as vehicles, between ephemeral plant brood sites to complete their developmental life cycle. In this system, hitchhiker overcrowding has proven negative impacts on vehicle and plant fitness. We expected nematodes to respond to conspecifics and heterospecific density on offered vehicles when making their choice. We found that animal‐parasitic nematodes preferred vehicles containing some conspecifics within a certain density range. However, plant‐parasitic nematodes preferentially boarded vehicles that were devoid of conspecifics or had few conspecifics. Plant parasites that preferred empty vehicles likely hitchhiked in pairs. Both nematode types employed volatile cues to discriminate between vehicles with different conspecific nematode densities. Our results suggest that vehicle overcrowding by conspecifics, most likely, guaranteed access to mates at the destination determined hitchhiker choice. Surprisingly, and contrary to our expectations, plant‐ and animal‐parasitic nematodes did not respond to heterospecific crowding on vehicles and did not discriminate between vehicles with different heterospecific nematode densities. The reason for this lack of response to heterospecific presence is unknown. This study not only shows that phoretic organisms use different strategies while choosing a vehicle but also confirms that density‐dependent effects can ensure the stability and persistence of phoretic interactions in a mutualism by balancing overcrowding against reproductive assurance.

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Section: Discussionmentioning

confidence: 99%

Hopping on: Conspecific traveller density within a vehicle regulates parasitic hitchhiking between ephemeral microcosms

Gupta

Borges

2021

Journal of Animal Ecology

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“…From a conservation standpoint, the absence of Allee effects is encouraging because Allee effects can increase extinction risk, making conservation intervention difficult relative to populations regulated by negative density dependence (Courchamp et al., 2008; Kramer et al., 2018). Allee effects near range boundaries could lead to stability as has been demonstrated theoretically, but they could also lead to rapid range contraction if environmental change and stochastic processes force small peripheral populations below the density threshold where positive density dependence occurs.…”

Section: Discussionmentioning

confidence: 99%

An experimental test of the Allee effect range limitation hypothesis

Merker

Chandler

2020

Journal of Animal Ecology

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1. Understanding how climate change impacts trailing-edge populations requires information about how abiotic and biotic factors limit their distributions. Theory indicates that socially mediated Allee effects can limit species distributions by suppressing growth rates of peripheral populations when social information is scarce. 2. The goal of our research was to determine if socially mediated Allee effects limit the distribution of Canada warbler Cardellina canadensis at the trailing-edge of the geographic range. 3. Using 4 years of observational data from 71 sites and experimental data at 10 sites, we tested two predictions of the socially mediated range limitation hypothesis: (a) local growth rates should be positively correlated with local density and (b) the addition of social cues immediately outside the trailing-edge range boundary would result in colonization of formerly unoccupied habitat and increased growth rates. During the third breeding season, social cues were experimentally added at 10 formerly unoccupied sites within and beyond the species' local range margin to determine if the addition of social information could increase density and effectively expand the species' range. 4. No experimental sites were colonized after adding social cues and no evidence of Allee effects was found. Rather, temperature, precipitation and negative density dependence strongly influenced population growth rates. 5. Although theoretical models indicate that the presence of socially mediated Allee effects at species range boundaries could increase the rate of climate-induced range shifts and local extinctions, empirical results from the first test of this hypothesis suggest that Allee effects play a minimal role in limiting species' distributions.

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“…, Kramer et al. ). However, spatial isolation may also reduce the chance of being found by a predator or herbivore or of being infected by a species‐specific disease (Comita et al.…”

Section: Wanted: Neglected Principles In Coexistence Theorymentioning

confidence: 99%

Give chance a chance: from coexistence to coviability in biodiversity theory

et al. 2019

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A large part of biodiversity theory is driven by the basic question of what allows species to coexist in spite of a confined number of niches. A substantial theoretical background to this question is provided by modern coexistence theory (MCT), which rests on mathematical approaches of invasion analysis to categorize underlying mechanisms into factors that reduce either niche overlap (stabilizing mechanisms) or the average fitness differences of species (equalizing mechanisms). While MCT has inspired biodiversity theory in the search for these underlying mechanisms, we feel that the strong focus on coexistence causes a bias toward the most abundant species and neglects the plethora of species that are less abundant and often show high local turnover. Given the more stochastic nature of their occurrence, we advocate a complementary cross‐level approach that links individuals, small populations, and communities and explicitly takes into account (1) a more complete inclusion of environmental and demographic stochasticity affecting small populations, (2) intraspecific trait variation and behavioral plasticity, and (3) local heterogeneities, interactions, and feedbacks. Focusing on mechanisms that drive the temporary coviability of species rather than infinite coexistence, we suggest a new approach that could be dubbed coviability analysis (CVA). From a modeling perspective, CVA builds on the merged approaches of individual‐based modeling and population viability analysis but extends them to the community level. From an empirical viewpoint, CVA calls for a stronger integration of spatiotemporal data on variability and noise, changing drivers, and interactions at the level of individuals. The resulting large volumes of data from multiple sources could be strongly supported by novel techniques tailored to the discovery of complex patterns in high‐dimensional data. By complementing MCT through a stronger focus on the coviability of less common species, this approach can help make modern biodiversity theory more comprehensive, predictive, and relevant for applications.

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Editorial: Allee effects in ecology and evolution

Cited by 43 publications

References 32 publications

Hopping on: Conspecific traveller density within a vehicle regulates parasitic hitchhiking between ephemeral microcosms

Hopping on: Conspecific traveller density within a vehicle regulates parasitic hitchhiking between ephemeral microcosms

An experimental test of the Allee effect range limitation hypothesis

Give chance a chance: from coexistence to coviability in biodiversity theory

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