Spatial structure of natural boxwood and the invasive box tree moth can promote coexistence

Ledru, Léo; Garnier, Jimmy; Gallet, Christiane; Noûs, Camille; Ibanez, Sébastien

doi:10.1016/j.ecolmodel.2021.109844

Cited by 10 publications

(6 citation statements)

References 80 publications

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“…Spatially local interactions can in uence ecological processes including disease, predation, and resource competition (DeAngelis and Yurek, 2017), and other authors have also found that movement is a key determinate of how local interactions scale up to population-level effects (eg. Pacala and Silander 1990; Lin and Pennings, 2018; Ledru et al, 2022). Our results further illustrate how understanding the relative scales of habitat heterogeneity and animal movement is critical to determining how spatially local interactions impact ecological dynamics.…”

Section: Discussionmentioning

confidence: 57%

When does spatial clustering in caterpillars influence the relationship between population density and contact rates?

Carson

Orians

Crone

2023

Preprint

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While interactions in nature are inherently local, ecological models often assume homogeneity across space, allowing for generalization across systems and greater mathematical tractability. Density-dependent disease models are a prominent example that assumes homogeneous interactions, leading to the prediction that disease transmission will scale linearly with population density. In this study, we examined how larval butterfly contact rates relate to population density in the Baltimore checkerspot (Euphydryas phaeton). Our study was partly inspired by a viral disease that is transmitted horizontally among Baltimore checkerspot larvae. First, we used multi-year larvae location data across six Baltimore checkerspot populations in the eastern U.S. to test whether larval nests are spatially clustered. We then integrated these spatial data with larval movement data. We used a Correlated Random Walk (CRW) model to investigate whether heterogeneity in spatially local interactions alter the assumed linear relationship between population density and contact. We found that all populations exhibited significant spatial clustering in their habitat use. Larval movement rates were influenced by encounters with host plants, and under many movement scenarios, the scale of predicted larval movement was not sufficient to allow for the “homogeneous mixing” assumed in density dependent disease models. Therefore, relationships between population density and larval contact rates were typically non-linear. We also found that observed use of available habitat patches led to significantly greater contact rates than would occur if habitat use were spatially random. These findings strongly suggest that incorporating spatial variation in larval interactions is critical to modeling disease outcomes in this system.

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Section: Discussionmentioning

confidence: 57%

When does spatial clustering in caterpillars influence the relationship between population density and contact rates?

Carson

Orians

Crone

2023

Preprint

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“…Spatially local interactions can influence ecological processes including disease, predation, and resource competition [ 28 ], and other authors have also found that movement is a key determinate of how local interactions scale up to population-level effects (eg. [ 52 , 54 , 64 ]). Our results further illustrate how understanding the relative scales of habitat heterogeneity and animal movement is critical to determining how spatially local interactions impact ecological dynamics.…”

Section: Discussionmentioning

confidence: 99%

Caterpillar movement mediates spatially local interactions and determines the relationship between population density and contact

Carson,

Orians,

Crone

2024

Mov Ecol

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Background While interactions in nature are inherently local, ecological models often assume homogeneity across space, allowing for generalization across systems and greater mathematical tractability. Density-dependent disease models are a prominent example of models that assume homogeneous interactions, leading to the prediction that disease transmission will scale linearly with population density. In this study, we examined how the scale of larval butterfly movement interacts with the resource landscape to influence the relationship between larval contact and population density in the Baltimore checkerspot (Euphydryas phaeton). Our study was inspired by the recent discovery of a viral pathogen that is transmitted horizontally among Baltimore checkerspot larvae. Methods We used multi-year larvae location data across six Baltimore checkerspot populations in the eastern U.S. to test whether larval nests are spatially clustered. We then integrated these spatial data with larval movement data in different resource contexts to investigate whether heterogeneity in spatially local interactions alters the assumed linear relationship between larval nest density and contact. We used Correlated Random Walk (CRW) models and field observations of larval movement behavior to construct Probability Distribution Functions (PDFs) of larval dispersal, and calculated the overlap in these PDFs to estimate conspecific contact within each population. Results We found that all populations exhibited significant spatial clustering in their habitat use. Subsequent larval movement rates were influenced by encounters with host plants and larval age, and under many movement scenarios, the scale of predicted larval movement was not sufficient to allow for the “homogeneous mixing” assumed in density dependent disease models. Therefore, relationships between population density and larval contact were typically non-linear. We also found that observed use of available habitat patches led to significantly greater contact than would occur if habitat use were spatially random. Conclusions These findings strongly suggest that incorporating larval movement and spatial variation in larval interactions is critical to modeling disease outcomes in E. phaeton. Epidemiological models that assume a linear relationship between population density and larval contact have the potential to underestimate transmission rates, especially in small populations that are already vulnerable to extinction.

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“…Invasive species may reach spectacular densities. During population outbreaks, the box tree moth becomes so numerous that predators are unlikely to influence their morph frequencies ( Ledru et al, 2022 ; Poloni, unpublished data). However, once caterpillars have defoliated all available hosts, moth populations drop and persist at lower densities according to the recovery of food plants ( Suppo et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Exploring polymorphism in a palatable prey: predation risk and frequency dependence in relation to distinct levels of conspicuousness

Poloni,

Dhennin,

Mappes

et al. 2024

Evolution Letters

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Camouflage and warning signals are different antipredator strategies, which offer an excellent opportunity to study the evolutionary forces acting on prey appearance. Edible prey often escape detection via camouflage, which usually leads to apostatic selection favoring rare morphs. By contrast, defended prey often display conspicuous coloration acting as warning signals to predators, which usually leads to positive frequency dependence and signal uniformity. However, when two morphs of the same species vary greatly in conspicuousness, the maintenance of both cryptic and conspicuous forms in profitable prey populations remains enigmatic. Using the white and melanic morphs of the invasive box tree moth (Cydalima perspectalis) presented at three different frequencies, we investigate (a) the palatability of caterpillars and adult moths to birds, (b) predation rates on the less conspicuous melanic morph, and (c) the role of frequency dependence in balancing morph frequencies. Our results show that caterpillars are distasteful for birds but not adult moths that are fully palatable. We found that the less conspicuous, melanic morph, benefits from reduced predation due to its lower detectability. The more conspicuous, white morph, instead, is more predated and is best off when common, suggesting positive frequency dependence. These results offer new insights into the evolution of color polymorphism and prey defenses in a polymorphic moth species. Further investigation is required to understand the role of different predation regimes on the maintenance of the polymorphism in this species and test whether additional selection pressures operate in natural populations.

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Spatial structure of natural boxwood and the invasive box tree moth can promote coexistence

Cited by 10 publications

References 80 publications

When does spatial clustering in caterpillars influence the relationship between population density and contact rates?

When does spatial clustering in caterpillars influence the relationship between population density and contact rates?

Caterpillar movement mediates spatially local interactions and determines the relationship between population density and contact

Exploring polymorphism in a palatable prey: predation risk and frequency dependence in relation to distinct levels of conspicuousness

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