Effects of within-patch heterogeneity on connectivity in pond-breeding amphibians studied by means of an individual-based model

Pontoppidan, Maj-Britt; Nachman, Gösta

doi:10.5194/we-13-21-2013

Cited by 2 publications

(1 citation statement)

References 47 publications

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“…Lag times have been frequently detected at the onset of a biological invasion across different taxa (Crooks, 2005;Aagaard and Lockwood, 2014;van Sittert and Measey, 2016) with multiple mechanisms hypothesized to play a role such as Allee effects (Courchamp et al, 1999;Stephens and Sutherland, 1999), spatial heterogeneity (Schreiber and Lloyd-Smith, 2009) and population growth trajectories (Pyšek and Hulme, 2005). For example, exponential growth trajectories are intrinsically expected to generate lags because at the onset of any invasion the number of individuals and/or invaded areas is necessarily low (Crooks, 2005).…”

Section: Discussionmentioning

confidence: 99%

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Vimercati

Hui

Davies

et al. 2017

Ecological Modelling

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Modelling population dynamics of invasive species may help to propose effective management countermeasures. Invasion dynamics generally show recursive patterns across species and regions, where initial lag is followed by spread and eventual dominance phases. However, timing and modes of these phases are highly variable, emerging from the interplay between traits of the invader and characteristics of the invaded landscape. Disentangling this interplay is particularly arduous in species with complex life-histories, where an individual passes through different life stages that alter physiology, behaviour and interactions with the environment. Here, we describe an age structured model that can be utilized to simulate population dynamics of invasive pond-breeding anurans. The model follows a spatially structured population approach, each pond representing a discrete habitat patch that exchanges individuals with other similar patches, and simulates change in survival and dispersal behaviour as a function of age. It also integrates dispersal with landscape complexity through landscape resistance modelling to depict functional connectivity across the pond network. Then we apply the model to a case study, the invasion of the guttural toad Sclerophrys gutturalis in Cape Town, first detected in 2000. Age-structured demographic and spatial dynamics of the focal population are reconstructed in a network of 415 ponds embedded in a heterogeneous landscape. Parameterization is conducted through field and laboratory surveys, a literature review and data collected during an ongoing extirpation from 2010. We use the model to explore: i) occurrence and duration of lag phase; ii) whether the spatial spread fits an accelerating or a linear trend; iii) how simulated dynamics match field observations. Additionally we test model sensitivity to demographic and behavioural traits. We found a lag phase in both demographic and spatial dynamics; however the lag duration of these dynamics does not coincide, where invaders start to spread across the pond network five years before the demographic explosion. Also, we found that the spatial spread fits an accelerating trend that causes complete invasion of the network in six years. Such dynamics noticeably match field observations and confirmed patterns previously detected in other invaders characterized by high dispersal abilities. Sensitivity analysis suggests that it would have been preferable to quantify initial propagule size and post-metamorphic survival in the field; both timing and modes of invasion are particularly sensitive to these parameters. We conclude that the model has potential to forecast amphibian invasion dynamics and test management countermeasures.

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Section: Discussionmentioning

confidence: 99%

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Vimercati

Hui

Davies

et al. 2017

Ecological Modelling

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Movement ecology of amphibians: from individual migratory behaviour to spatially structured populations in heterogeneous landscapes^,

SinschUlrich

2014

Can. J. Zool.

109

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Both genetic cohesion among local populations of animals and range expansion depend on the frequency of dispersers moving at an interpatch scale. Animal movement has an individual component that reflects behaviour and an ecological component that reflects the spatial organization of populations. The total movement capacity of an individual describes maximum movement distance theoretically achievable during a lifetime, whereas its variation among the members of a local population determines the magnitude of interpatch movements and thus of gene flow between neighbouring patches within metapopulation or patchy population systems. Here, I review information on dispersal and migration as components of the movement capacity of juvenile and adult pond-breeding amphibians and discuss how these components inform the spatial structure of populations. Amphibians disperse as juveniles and adults, but movement distances detected in tracking or capture–mark–recapture studies are usually far below the corresponding estimates based on molecular gene-flow data. This discrepancy reflects the constraints of available tracking methods for free-ranging individuals leading to inappropriate surrogates of annual movement capacity, but can be resolved using probabilistic approaches based on dispersal functions. There is remarkable capacity for and plasticity in movements in amphibians. Annual within-patch movements (migrations) of individuals can be large and likely represent an underestimated capacity for movement at the interpatch scale. Landscape resistance may influence the paths of dispersing amphibians, but rarely impedes interpatch movements. Juveniles emigrating unpredictably far from the natal pond and adults switching from within-patch migrations to dispersal to another patch demonstrate the plasticity of individual movement behaviour. Three basic conclusions can be drawn with respect to the linkage of individual movement behaviour and spatial or genetic structure of local amphibian populations embedded in a heterogeneous landscape: (1) individual movements or consecutive short-term series of movements are misleading surrogate measures of total movement capacity; (2) probabilistic modelling of movement capacity is the best available behavioural predictor of interpatch gene flow; (3) connectivity of local populations in heterogeneous landscapes is less affected by landscape resistance than previously expected.

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Effects of within-patch heterogeneity on connectivity in pond-breeding amphibians studied by means of an individual-based model

Cited by 2 publications

References 47 publications

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Movement ecology of amphibians: from individual migratory behaviour to spatially structured populations in heterogeneous landscapes^,

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Effects of within-patch heterogeneity on connectivity in pond-breeding amphibians studied by means of an individual-based model

Cited by 2 publications

References 47 publications

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Movement ecology of amphibians: from individual migratory behaviour to spatially structured populations in heterogeneous landscapes,

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Movement ecology of amphibians: from individual migratory behaviour to spatially structured populations in heterogeneous landscapes^,