Analysing point patterns on networks — A review

Baddeley, Adrian; Nair, Gopalan; Rakshit, S.; McSwiggan, Greg; Davies, Tilman M.

doi:10.1016/j.spasta.2020.100435

Cited by 64 publications

(62 citation statements)

References 136 publications

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“…This result suggests that there may be additional predictors influencing the presence of forest ravens along roadsides that were not measured in this study and should be investigated further. While point-pattern methods have been used for multi-dimensional data (e.g., two-dimensional vegetation plots), they have been underutilised for one-dimensional analysis (Baddeley et al 2020). Our Bayesian approach to parameter estimation of Poisson point-process models facilitates the inclusion of hierarchical structures and subsequent model comparison.…”

Section: Discussionmentioning

confidence: 99%

“…2a). The distribution of points in a spatial point pattern is typically modelled as a Poisson process, which assumes that each observation is independent (Baddeley et al 2020). Roadkill locations and habitat type were used to define spatial co-variates, X F : distance in metres to nearest open farmland; and X R : distance in metres to nearest roadkill (Fig.…”

Section: Methodsmentioning

confidence: 99%

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Roadkill islands: carnivore extinction shifts seasonal use of roadside carrion by generalist avian scavenger

Fielding¹,

Buettel²,

Brook³

et al. 2021

Preprint

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Global road networks facilitate habitat modification and are integral to human expansion. Many animals, particularly scavengers, use roads as they provide a reliable source of food, such as carrion left after vehicle collisions. Tasmania is often cited as the 'roadkill capital of Australia', with the isolated offshore islands in the Bass Strait experiencing similar, if not higher, levels of roadkill. However, native mammalian predators on the islands are extirpated, meaning the remaining scavengers are likely to experience lower interference competition. In this study, we use a naturally occurring experiment to examine how the loss of mammalian carnivores within a community impacts roadside foraging behaviour by avian scavengers. We monitored the locations of roadkill and forest ravens (Corvus tasmanicus), an abundant scavenger species, on eight road transects across the Tasmanian mainland (high scavenging competition) and the Bass Strait islands (low scavenging competition). We represented raven observations as one-dimensional point patterns, using hierarchical Bayesian models to investigate the dependence of raven spatial intensity on habitat, season, distance to roadkill and route location. We found that roadkill carcasses were a strong predictor of raven presence along road networks. The effect of roadkill was amplified on roads on the Bass Strait islands, where roadside carrion was a predictor of raven presence across the entire year. In contrast, ravens were more often associated with roadkill on Tasmanian mainland roads in the autumn, when other resources were low. This suggests that in the absence of competing mammalian scavengers, ravens choose to feed on roadside carrion throughout the year, even in seasons when other resources are available. This low interference competition could be disproportionately benefiting forest ravens, leading to augmented raven populations and changes to the vertebrate community structure. Our study provides evidence that scavengers modify their behaviour in response to reduced scavenger species diversity, potentially triggering trophic shifts and highlighting the importance of conserving or reintroducing carnivores within ecosystems.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Roadkill islands: carnivore extinction shifts seasonal use of roadside carrion by generalist avian scavenger

Fielding¹,

Buettel²,

Brook³

et al. 2021

Preprint

View full text Add to dashboard Cite

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“…Intensity is the average density of points (expected number of points per unit area) [ 18 ]. In general, the intensity of point will vary from place to place, so the intensity may be inhomogeneous.…”

Section: Methodsmentioning

confidence: 99%

Spatial and temporal clusters of avian influenza a (H7N9) virus in humans across five epidemics in mainland China: an epidemiological study of laboratory-confirmed cases

et al. 2020

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Background: Avian influenza A (H7N9) virus was first reported in mainland China in 2013, and alarming in 2016-17 due to the surge across a wide geographic area. Our study aimed to identify and explore the spatial and temporal variation across five epidemics to reinforce the epidemic prevention and control. Methods: We collected spatial and temporal information about all laboratory-confirmed human cases of A (H7N9) virus infection reported in mainland China covering 2013-17 from the open source. The autocorrelation analysis and intensity of cases were used to analyse the spatial cluster while circular distribution method was used to analyse the temporal cluster. Results: Across the five epidemics, a total of 1553 laboratory-confirmed human cases with A (H7N9) virus were reported in mainland China. The global Moran's I index values of five epidemic were 0.610, 0.132, 0.308, 0.306, 0.336 respectively, among which the differences were statistically significant. The highest intensity was present in the Yangtze River Delta region and the Pearl River Delta region, and the range enlarged from the east of China to inner provinces and even the west of China across the five epidemics. The temporal clusters of the five epidemics were statistically significant, and the peak period was from the end of January to April with the first and the fifth epidemic later than the mean peak period.

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“…However, despite this, the dead elements (e.g., decaying logs, fallen trees) are rarely measured or analysed as linear features in an SPPA framework (Buettel et al, 2018). There has been some success in modifying spatial point-pattern statistics, like Ripley's K, to deal with points distributed along linear networks (Spooner et al, 2004;Baddeley et al, 2020). There are also examples of modelling lines and points separately and then testing these for interactions, for instance in geological studies of ore seams (e.g., Mardia (1972)), see also (Stoyan and Ohser, 1982).…”

Section: Introductionmentioning

confidence: 99%

Spatial pattern analysis of line-segment data in ecology

Yates

Brook

Buettel

2021

Preprint

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The spatial analysis of linear features (lines and curves) is a challenging and rarely attempted problem in ecology. Existing methods are typically expressed in abstract mathematical formalism, making it difficult to assess their relevance and transferability into an ecological setting. A set of concrete and accessible tools is needed.We develop a new method to analyse the spatial patterning of line-segment data. It is based on a generalisation of Ripley’s K-function and includes an analogue of the transformed L-function, together with estimators and theoretical expectation values. We introduce a class of line-segment processes, related to the Boolean model, which we use in conjunction with Monte-Carlo methods and information criteria to generate and compare candidate models. We demonstrate the utility of our method using fallen tree (dead log) data collected from two one-hectare Australian tall eucalypt forest plots.Comparing six line-segment models, we find for both plots that the distribution of fallen logs is best explained by plot-level spatial heterogeneity. The use of non-uniform distributions to model dead-log orientation on the forest floor improves model performance in one of the two sites. Our case study highlights the challenges of model comparison in spatial-pattern analysis, where Monte-Carlo approaches based on the discrepancy of simulated summary functions can generate a different ranking of models than that of information criteria.These methods are of a general nature and are applicable to any line-segment data. In the context of forest ecology, the integration of fallen logs as linear structural features in a landscape with the point locations of living trees, and a quantification of their interactions, will yield new insights into the functional and structural role of tree fall in forest communities and their enduring post-mortem ecological legacy as spatially distributed decomposing logs.

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Analysing point patterns on networks — A review

Cited by 64 publications

References 136 publications

Roadkill islands: carnivore extinction shifts seasonal use of roadside carrion by generalist avian scavenger

Roadkill islands: carnivore extinction shifts seasonal use of roadside carrion by generalist avian scavenger

Spatial and temporal clusters of avian influenza a (H7N9) virus in humans across five epidemics in mainland China: an epidemiological study of laboratory-confirmed cases

Spatial pattern analysis of line-segment data in ecology

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