Local Movement and Edge Effects on Competition and Coexistence in Ephemeral-Patch Models

Remer,; Heard,

doi:10.2307/2463608

Cited by 10 publications

(14 citation statements)

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“…primarily among neighbouring plants). Such spatial structure is likely to have interesting consequences (Remer and Heard 1998), but is outside the scope of this manuscript.…”

Section: Ovipositionmentioning

confidence: 98%

“…Egg distributions may be heterogeneous because female movements during oviposition are influenced by the spatial arrangement of oviposition sites (Remer and Heard 1998), because females lay eggs in clutches (Sevenster and van Alphen 1996;Heard and Remer 1997;Heard 1998) or because females aggregate to particular oviposition sites (Hassell and May 1988). Some consequences of egg distribution behaviour have been examined for competitive (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Some consequences of egg distribution behaviour have been examined for competitive (e.g. Ives 1991;Heard and Remer 1997;Remer and Heard 1998) and host-parasitoid (e.g. Hassell and May 1988;Rohani et al 1994) interactions, but for plant-herbivore systems, only a few verbal models have been available (except see Myers 1976).…”

Section: Introductionmentioning

confidence: 99%

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Travel costs, oviposition behaviour and the dynamics of insect–plant systems

Heard

Remer

2008

Theor Ecol

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Insect attack can have major consequences for plant population dynamics. We used individually based simulation models to ask how insect oviposition behaviour influences persistence and potential stability of an herbivoreplant system. We emphasised effects on system dynamics of herbivore travel costs and of two kinds of behaviour that might evolve to mitigate travel costs: insect clutch size behaviour (whether eggs are laid singly or in groups) and female aggregation behaviour (whether females prefer or avoid plants already bearing eggs). Travel costs that increase as plant populations drop lead to inverse density dependence of plant reproduction under herbivore attack. Female clutch size and aggregation behaviours also strongly affect system dynamics. When females lay eggs in large clutches or aggregate their clutches, herbivore damage varies strongly among plants, providing probabilistic refuges that permit plant reproduction and persistence. However, the population dynamics depend strongly on whether insect behaviour is fixed or responds adaptively to plant population size: when (and only when) females increase clutch size or aggregation as plants become rare, refuges from herbivory weaken at high plant density, creating inverse density dependence in plant reproduction. Both herbivore travel costs themselves, and also insect behaviour that might evolve in response to travel costs, can thus create plant density dependence-a basic requirement for regulation of plant populations by their insect herbivores.

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“…primarily among neighbouring plants). Such spatial structure is likely to have interesting consequences (Remer and Heard 1998), but is outside the scope of this manuscript.…”

Section: Ovipositionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Travel costs, oviposition behaviour and the dynamics of insect–plant systems

Heard

Remer

2008

Theor Ecol

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“…Habitat edges can alter the nature of species interactions and thereby modify ecological processes and dynamics at a wide range of scales (Fagan, Cantrell & Cosner, 1999). Examples of altered herbivory (McKone et al, 2001), seed predation (Burkey, 1993), competition (Remer & Heard, 1998), predation (Ries & Fagan, 2003) and parasitism rates (Tscharntke et al, 2002 b ;Cronin, 2003b) are relatively common, and explicit recognition of these responses has applied significance in the field of biological control in agroecosystems (Thies & Tscharntke, 1999;. However, habitat edge effects can sometimes be dependent on landscape context, with diverse, structurally complex landscapes negating differences between fragment edges and interiors (Thies & Tscharntke, 1999;Tscharntke & Brandl, 2004).…”

Section: ) Edges Alter Species Interactionsmentioning

confidence: 99%

Confounding factors in the detection of species responses to habitat fragmentation

2005

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Habitat loss has pervasive and disruptive impacts on biodiversity in habitat remnants. The magnitude of the ecological impacts of habitat loss can be exacerbated by the spatial arrangement -or fragmentation -of remaining habitat. Fragmentation per se is a landscape-level phenomenon in which species that survive in habitat remnants are confronted with a modified environment of reduced area, increased isolation and novel ecological boundaries. The implications of this for individual organisms are many and varied, because species with differing life history strategies are differentially affected by habitat fragmentation. Here, we review the extensive literature on species responses to habitat fragmentation, and detail the numerous ways in which confounding factors have either masked the detection, or prevented the manifestation, of predicted fragmentation effects.Large numbers of empirical studies continue to document changes in species richness with decreasing habitat area, with positive, negative and no relationships regularly reported. The debate surrounding such widely contrasting results is beginning to be resolved by findings that the expected positive species-area relationship can be masked by matrix-derived spatial subsidies of resources to fragment-dwelling species and by the invasion of matrix-dwelling species into habitat edges. Significant advances have been made recently in our understanding of how species interactions are altered at habitat edges as a result of these changes. Interestingly, changes in biotic and abiotic parameters at edges also make ecological processes more variable than in habitat interiors. Individuals are more likely to encounter habitat edges in fragments with convoluted shapes, leading to increased turnover and variability in population size than in fragments that are compact in shape. Habitat isolation in both space and time disrupts species distribution patterns, with consequent effects on metapopulation dynamics and the genetic structure of fragment-dwelling populations. Again, the matrix habitat is a strong determinant of fragmentation effects within remnants because of its role in regulating dispersal and dispersalrelated mortality, the provision of spatial subsidies and the potential mediation of edge-related microclimatic gradients.We show that confounding factors can mask many fragmentation effects. For instance, there are multiple ways in which species traits like trophic level, dispersal ability and degree of habitat specialisation influence specieslevel responses. The temporal scale of investigation may have a strong influence on the results of a study, with short-term crowding effects eventually giving way to long-term extinction debts. Moreover, many fragmentation effects like changes in genetic, morphological or behavioural traits of species require time to appear. By contrast, synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of population decline may magnify the impacts...

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“…Surprisingly little attention, however, has been directed at comparing the spatial patterns of available and exploited points. Numerical techniques exist for some related aspects of population dynamics on patchy resources, such as the aggregation model of coexistence (Hartley and Shorrocks 2002), but these models are rarely spatially-explicit (i.e., directly consider the arrangement of resource patches in space) and this may be important in some situations (Heard 1998, Remer andHeard 1998). There are many spatially-explicit studies of organism-landscape interactions that view landscapes as a mosaic of habitat types, and they use different numerical techniques, appropriate to that scenario (e.g.…”

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confidence: 99%

Spatial point pattern analysis of available and exploited resources

Lancaster¹,

Downes²

2004

Ecography

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A patchy spatial distribution of resources underpins many models of population regulation and species coexistence, so ecologists require methods to analyse spatiallyexplicit data of resource distribution and use. We describe a method for analysing maps of resources and testing hypotheses about species' distributions and selectivity. The method uses point pattern analysis based on the L-function, the linearised form of Ripley's K-function. Monte Carlo permutations are used for statistical tests. We estimate the difference between observed and expected values of L(t), an approach with several advantages: 1) The results are easy to interpret ecologically. 2) It obviates the need for edge correction, which has largely precluded the use of L-functions where plot boundaries are ''real''. Including edge corrections may lead to erroneous conclusions if the underlying assumptions are invalid.3) The null expectation can take many forms, we illustrate two models: complete spatial randomness (to describe the spatial pattern of resources in the landscape) and the underlying pattern of resource patches in the landscape (akin to a neutral landscape approach). The second null is particularly useful to test whether spatial patterns of exploited resource points simply reflect the spatial patterns of all resource points. We tested this method using over 100 simulated point patterns encompassing a range of patterns that might occur in ecological systems, and some very extreme patterns. The approach is generally robust, but Type II decision errors might arise where spatial patterns are weak and when trying to detect a clumped pattern of exploited points against a clumped pattern of all points. An empirical example of an intertidal lichen growing on barnacle shells illustrates how this technique might be used to test hypotheses about dispersal mechanisms. This approach can increase the value of survey data, by permitting quantification of natural resource patch distribution in the landscape as well as patterns of resource use by species.J. Lancaster (j.lancaster@ed.ac.uk),

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Local Movement and Edge Effects on Competition and Coexistence in Ephemeral-Patch Models

Cited by 10 publications

References 0 publications

Travel costs, oviposition behaviour and the dynamics of insect–plant systems

Travel costs, oviposition behaviour and the dynamics of insect–plant systems

Confounding factors in the detection of species responses to habitat fragmentation

Spatial point pattern analysis of available and exploited resources

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