A simple parametric method for reducing sample sizes in gut passage time trials

Rawsthorne, John; Roshier, David A.; Murphy, S. R.

doi:10.1890/08-1137.1

Cited by 10 publications

(9 citation statements)

References 10 publications

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“…Such a lognormal dispersal kernel has been found in many seed dispersal systems (Rawsthorne et al. , Viana et al. ).…”

Section: Methodsmentioning

confidence: 70%

“…k i determined the probability of survival, reproduction, and colonization in environment E. Dispersal was limited only by distance according to a lognormal kernel W (r) , where the location parameter (l dispersal ) was 0 (i.e., dispersal peaks at a distance of one grid cell) and the scale parameter (r dispersal ) controlled the dispersal capacity. Such a lognormal dispersal kernel has been found in many seed dispersal systems (Rawsthorne et al 2009, Viana et al 2013). In addition to dispersal within the grid, we incorporated immigration (m) from outside the grid (i.e., from the metacommunity) to avoid long-term monodominance in communities that were more neutral.…”

Section: Simulating Community Assemblymentioning

confidence: 79%

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Spatial scale modulates the inference of metacommunity assembly processes

Viana

Chase

2019

Ecology

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The abundance and distribution of species across the landscape depend on the interaction between local, spatial, and stochastic processes. However, empirical syntheses relating these processes to spatiotemporal patterns of structure in metacommunities remain elusive. One important reason for this lack of synthesis is that the relative importance of the core assembly processes (dispersal, selection, and drift) critically depends on the spatial grain and extent over which communities are studied. To illustrate this, we simulated different aspects of community assembly on heterogeneous landscapes, including the strength of response to environmental heterogeneity (inherent to niche theory) vs. dispersal and stochastic drift (inherent to neutral theory). We show that increasing spatial extent leads to increasing importance of niche selection, whereas increasing spatial grain leads to decreasing importance of niche selection. The strength of these scaling effects depended on environment configuration, dispersal capacity, and niche breadth. By mapping the variation observed from the scaling effects in simulations, we could recreate the entire range of variation observed within and among empirical studies. This means that variation in the relative importance of assembly processes among empirical studies is largely scale dependent and cannot be directly compared. The scaling coefficient of the relative contribution of assembly processes, however, can be interpreted as a scale‐integrative estimate to compare assembly processes across different regions and ecosystems. This emphasizes the necessity to consider spatial scaling as an explicit component of studies intended to infer the importance of community assembly processes.

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“…Such a lognormal dispersal kernel has been found in many seed dispersal systems (Rawsthorne et al. , Viana et al. ).…”

Section: Methodsmentioning

confidence: 70%

Section: Simulating Community Assemblymentioning

confidence: 79%

Spatial scale modulates the inference of metacommunity assembly processes

Viana

Chase

2019

Ecology

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“…Vellend et al 2003;Will & Tackenberg 2008), results of a lognormal fit to the data are included in Fig. 2 (Rawsthorne et al 2009).…”

Section: Resultsmentioning

confidence: 99%

A reassessment of the role of simple seed traits in mortality following herbivore ingestion

D’hondt

Hoffmann

2010

Plant Biology

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seed dispersal; endozoochory; zoochory; ungulates; foliage is the fruit; phylogenetically independent contrasts; hardseededness; physical dormancy ABSTRACTGrazing mammals are regarded as major vectors in seed dispersal of grassland plants through seed ingestion and subsequent excretion (endozoochory). The (evolutionary) ecology underlying this dispersal mode is understood relatively poorly as we have limited data, among others, on how seed attributes perform in this process (and could thus be selected for). Regarding mortality due to digestion, contrasting patterns found on the role of simple seed traits seem partly due to inadequate comparativeanalytical methods. We conducted a feeding experiment in which controlled seed quantities from a large number of grassland herbs and grasses were fed to cattle (48 species in total). Seed mass, length and shape measurements were related to mortality rates using phylogenetically independent contrasts, which account for taxonomical interdependence. The proportion of seeds surviving the digestive tract was generally low, but ranged up to 100 %, with increased germination for some species. Neither seed size nor shape correlated significantly with mortality. Structural traits are likely to overrule these simple seed traits, as illustrated by high survival rates of species that are characterized by water-impermeable seeds. As the latter trait holds some interesting properties with respect to intraspecific variation and genetics, it could open up perspectives for inference on any evolutionary consequences for this type of dispersal.

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“…1. Distribution of gut passage times in minutes for Amyema quandang mistletoe seeds consumed by spinycheeked honeyeater Acanthagenys rufogularis.Vertical bars are counts of 435 observed gut passage times from a previous study (Murphy et al 1993) grouped into 5-min intervals; the curve is a smoothed frequency distribution fitted using a log-normal distribution parameterized using the observed data (m = 3.658, s = 0.3065; c 2 = 13.4, P > 0.25) using the method described by Rawsthorne et al (2009). extent of mistletoe occurrence was established within the study area (Fig. 2).…”

Section: Resultsmentioning

confidence: 99%

“…This was achieved by determining a bird's displacement from a starting position within a movement path for each subsequent minute of that movement path, and then aggregating these data across many such 'initial' locations for each bird (after Murray 1988). A frequency distribution of gut passage times was determined by fitting a log-normal distribution to 435 observed gut passage times of A. quandang seeds in spiny-cheeked honeyeaters collected in a previous study (Murphy et al 1993;Rawsthorne et al 2009; Fig. 1).…”

Section: Estimation Of Seed Dispersal Curvesmentioning

confidence: 99%

Implications of movement patterns of a dietary generalist for mistletoe seed dispersal

Rawsthorne

Watson

Roshier³

2010

Austral Ecology

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Mistletoes are dispersed primarily by frugivorous birds and have highly aggregated distributions at multiple scales. Mistletoe specialist frugivores have been found to intensify infections within infected hosts and stands, and this is considered the most likely mechanism underlying clumped mistletoe distributions at these scales. How these patchy infections first develop and whether seed dispersers also contribute to aggregated mistletoe distributions at landscape and regional scales have not been evaluated. Here we predict the mistletoe seed shadow of a dietary generalist (spiny-cheeked honeyeater Acanthagenys rufogularis Aves: Meliphagidae), by combining our observations of movements via radio telemetry with previous data on gut passage times to estimate seed dispersal curves for individual birds. There was considerable variation in movements and inferred seed dispersal between individuals, with non-breeding birds predicted to regularly transport Amyema quandang (Santalales: Loranthaceae) seeds up to 700 m; well beyond the boundaries of an existing mistletoe infection. As the first work to consider explicitly the distance component of mistletoe seed dispersal by dietary generalists, this study poses further questions about the relative seed dispersal roles of dietary generalists and mistletoe specialists. Moreover, our findings highlight considerable intraspecific variation in movement and foraging behaviour, suggesting gender and reproductive status of birds should be considered explicitly when quantifying seed dispersal services.

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A simple parametric method for reducing sample sizes in gut passage time trials

Cited by 10 publications

References 10 publications

Spatial scale modulates the inference of metacommunity assembly processes

Spatial scale modulates the inference of metacommunity assembly processes

A reassessment of the role of simple seed traits in mortality following herbivore ingestion

Implications of movement patterns of a dietary generalist for mistletoe seed dispersal

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