Questions tagged [ecology]

Ecology is the study of how organisms interact with their environment & each other. Ecology uses some specialized statistical techniques (eg ordination methods). Use this tag to indicate applications of statistics that are unique to ecology or that require a recognition of the ecological context.

94 questions with no upvoted or accepted answers
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122 views

Help with designing the analysis of a radio telemetry study

I was wondering if there are any spatial ecologists out there who can provide some insight on the trouble I'm having with my Masters research. I am looking at the association a bat species to high ...
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1answer
70 views

Modelling % cover that do not add up to 100% : GLM distribution families

I have an experimental set-up that consists in studying the impact of diversity of plant mixtures on the development of invasive species. On each plot, we recorded the % cover of each species which ...
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439 views

Comparing two non-linear biological models: differences in y vs. differences in slope

I'm an ecology PhD student, but unfortunately not a very mathematically sophisticated one. I am interested in ways to compare two non-linear models. I was really impressed with this answer, which ...
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1answer
94 views

GLM on non-integer data

I'm looking for a recommendation on what GLM I could do with non-integer data. Brief background of what I am doing: I'm wanting to combine calculated herbivory rates with abundance data, to compare ...
3
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1answer
41 views

GLM with random factors for observational design

I would love your help: I have 50 houses where I have counted the number of Mosquito's eggs once a week for 4 months. I have 5 fixed factors (temperature, NDVI, precipitations, etc) and I want to add ...
3
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1answer
48 views

Using GLMM to explain vegetation change as a function of change in soil parameters

I have a dataset that consists of vegetation datasets (species/abundancy tables) and soil parameters (tested for ten parameters per soil core). Three different rounds of these data are recorded in ...
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0answers
396 views

Confidence intervals on a predicted regression line cross

I have carried out a model on some long-term data I have looking at bird arrival dates in relation to different weather conditions and have run into some problems when plotting the results. I have ...
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28 views

Estimating proportion of region cropped by proportions in random samples

I have a series of quadrats placed randomly across aerial photography of a region. In each quadrat I have estimated the proportion of the quadrat under cropping and my goal is to estimate the ...
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0answers
828 views

Suitable method for modelling (underdispersed?) count data with lots of zeros and long tail

I have a small data set of counts of bees. I tried a simple Poisson model without random effects but it was very overdispersed (3.95). When I fit a GLMM with random effects (using glmer in lme4) it ...
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0answers
28 views

Hierarchical clustering: distance/linkage combination that allows starting in the middle of the dendrogram

I want to use hierarchical clustering to classify some ecological data (species abundances on different places), so I would like to use a Manhattan type distance that doesn't account for double ...
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46 views

Poisson Binomial Distribution - confidence intervals for sum of unequal probabilities estimated with uncertainty

I believe my question is related to, but distinct from this one: Poisson Binomial Distribution - confidence intervals I am working to estimate species richness by summing the results of 12 individual ...
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0answers
63 views

Exploratory data analysis before pefrorming Canonical Correspondence Analysis (CCA)

I want to perform CCA, but I read that, remember that observations (for example, species abundances) have to present unimodal distributions along gradients (for example, environmental variables). ...
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43 views

Is it valid to solve an equation for multiple coefficients, then average them to obtain overall effect?

I have a regression model, the setup for which is as follows: I am using manyglm, a multivariate general linear model approach to determine the difference in several invertebrate species between two ...
2
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2answers
36 views

Which tests can be used for variables that are non-normal, but have homogenous variances?

I am trying to compare the effect of two treatments (planting distance) on the growth of plants (multiple species), using the variable growth rate in diameter for multiple years. I have 4 sets of ...
2
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1answer
22 views

What are some simple ways i can analyse changes in relative abundance

I am looking (to begin with) some simple ways to analyse changes in relative abundance of species numbers over time. All we have is a inventory list of the number of species for each four seasons, ...
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63 views

Spatial clustering analysis on binomial data collected on a grid

I am new to spatial statistics and need help figuring out how to assess if there is spatial clustering in my dataset using R. I am assessing if acorn consumption is different inside timber harvest ...
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0answers
53 views

Comparing biological diversity before and after

I've got counts of two species in two treatments at two timepoints. I've got six replicates of each treatment. I'd like to know how to compare treatment diversity. As it is, I've calculated the ...
2
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1answer
70 views

Repeated measures field experiment: statistical design

In a study on a bird, breeding territories were mapped in 1990 and controlled in 2017. Each territory is one sample with the dependent variable territory abandoned (possible values: "yes" and "no"). I ...
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0answers
163 views

How to find the correct spatial scale in landscape ecology?

I am currently studying the effect of organic farming on honeybee colonies. I have calculated the percentage of organic land in several buffer areas around the hives (from 100m to 3000m in 100m steps) ...
2
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1answer
241 views

Multivariate data with repeated measures - restricted permutations

I have a data frame of multivariate abundances (species) that have been measured from sites under two different treatments. These same sites have been repeatedly measured over multiple years. I am ...
2
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1answer
155 views

What's the most adequate test/tests for this study?

I'm a PhD student (Biodiversity and Animal Ecology). I am preparing a scientific article to submit and I need help in statistical analysis of my data. In this message I will try to provide as much as ...
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0answers
43 views

Describing Differences between Two Inferred Populations

I am interested in the size of an animal in two populations, and found reliable estimates of the population provided by NOAA. The data was in the form of estimated total population within discrete ...
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0answers
63 views

Quantifying tree height diversity or heterogeneity

I am analyzing data collected in the field for a habitat selection study of a large mammal. I have ~1300 plots that were sampled. I am trying to find a good way to quantify the diversity of tree ...
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71 views

Spatially explicit model to test effects of multiple variables

What is the appropriate model to test the effects of location, species, and size on tree growth? So I have both categorical and continuous variables I want in the model. The following graphic just ...
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25 views

Doubts about the use of Cross-Validation in GLMM

I've recently ask in statckoverflow about some doubts with logistic regression fitted with a GLMM and an user recommend me asking in this forum. So, here it goes. I work with a wild population of a ...
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17 views

How to analyze data for spatial aggregation and niche overlap with no specific GPS points over time?

I study soil insects, and sample monthly for insects. Each month, I sample at 8 different sites. Each site is divided roughly into 4 meter square quadrants (shown in figure). From each quadrant, I ...
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40 views

Ecological count data and offset terms

Problem: When using GAMs to model ecological count data (e.g. fish counts) using Poisson or negative-binomial distributions, the response variable is raw counts and the offset (e.g. log-transformed ...
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1answer
33 views

What is the general process of choosing, confirming, and supporting the distribution used in a generalized linear model?

I am trying to better understand the process of choosing and validating a distribution for a generalized linear model (glm). I understand that for the most part, you can narrow it down to a few ...
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2answers
25 views

How can I calculate correlations between fungi presence and forest health in two different forest sites?

I am working on an undergraduate thesis and I have extremely little knowledge on statistics so my analysis is going to have to be quite basic. In two different forest ecosystems (plantation and mature)...
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1answer
21 views

Presence/absence data

I'm working on a study where I am testing whether individual species that I observed or didn't observe (presence/absence of observing species A on each survey) during drought and non-drought (presence/...
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0answers
20 views

What is cross validation doing in my spatial ecology model, and how necessary is it to run?

I'm currently using the R latticeDensity package to estimate home ranges of animals. Within the documentation, The minimum uvc (Unbiased CrossValidation ...
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0answers
28 views

Modelling resource selection in savanna ungulates

I am amidst an analysis of an 8 year data set that was collected from wildlife surveys over an 8 year period for my MSc thesis. 2 surveys were conducted each season for the three discernible seasons ...
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1answer
27 views

Using a species distribution model as an environmental variable in another distribution model

I'm interested in examining which of a suite of environmental variables is most important to predicting the distribution of a given species A, given a set of presence/absence points. I would like to ...
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0answers
163 views

Input data for Canonical Correspondence Analysis (CCA)

I'm going to conduct Canonical Correspondence Analysis (CCA). In the tutorial I've found at: CCA environmental data are discrete ...
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0answers
44 views

Can you run an AIC twice in a row?

I came across this paper that seems to make a bunch of models, run an AIC, select the best models from that, then run the AIC again. Am I interpreting this correctly? And is that okay to do? Couldn't ...
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1answer
81 views

Is Hellinger transformation suitable for repeated (in time) site-species abundance data?

I have fish survey data from four different years and several locations, where I would like to study the difference in abundance and biomass between sites and check whether time dependence influences ...
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1answer
237 views

Multiple testing (bonferroni?) with GLM

Hi everyone: I scored four mutually-exclusive behaviors (e.g. feeding, brooding, standing, preening) on a number of observations of birds in two different treatments, and two different nesting ...
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1answer
37 views

Which stats can test differences between two experiments?

I have an experiment to look at habitat preferences of beetles and the effect of competition. In the first test, a beetle is on his own in an arena and I measured the % of time he spends in each of ...
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268 views

Canonical Correspondence Analysis: how to interpret results

I am using Canonical Correspondence Analysis (CCA) to analyze phytolith abundances (similar to pollen) over environmental gradients. As I am new to CCA, I read some background info. The following ...
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1answer
62 views

How to handle non-detects in duplicate samples

I took two separate water samples (one sample per bottle) in twenty one river locations (n=42). For the purpose of this question I am calling the two bottles duplicates. I am trying to show how ...
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0answers
67 views

Which statistical test should I use to compare land use type and species abundance?

I have abundance data for a species of bird and data on land use type in the areas where the bird data was collected. I want to test whether land use type affects bird abundance but I don't know what ...
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2answers
53 views

How to choose the statistic metrics to describe the patterns of trees near the tree line?

I have tree inventory data: about 700 points of trees with known locations (X;Y;Z) and measured heights and diameters of stems at the breast height (DBH). The trees are located along the elevation ...
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0answers
148 views

Comparing Composition of Samples

I have data on the composition of two different types of animal droppings. There are 15 observations of Animal 1 and 40 observations of Animal 2. I have the makeup of each dropping broken up into ...
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0answers
253 views

Residuals of symmetric Procrustes analyses are not symmetric

I am trying to replicate the analysis I saw in a paper. One of the step is to describe the relationships between two data tables. I use the procrustes() function ...
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0answers
187 views

How to calculate growth rates up and down from a local maxima?

Problem: I am currently doing my Msc-thesis on rodent population dynamics. One of my aims is look at symmetry in oscillation topography. For this I want to calculate the growth rates up and down from ...
1
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1answer
65 views

What distribution to use for response variable which is a ratio of counts (that are not independent) where it can be >1?

I have two sets of counts, bat passes and feeding buzzes. A feeding buzz is not independent of a bat pass. In a single bat pass, there can be multiple feeding buzzes. My response variable is buzz ...
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0answers
69 views

spatial autocorrelation, some features with no nearby neighbors

I have a set of point features that span the African continent. Some are clustered and show positive autocorrelation in a various measured ecological characteristics at scales of less than ~150km. ...
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0answers
20 views

What statistical methods does one use to map movements?

I have the movement (given by longitude and latitude) of 5 birds over a period of about a year. I would like to analyze their movement, i.e. where do they like to spend most of their time. What ...
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0answers
302 views

Imputing missing values and quality control of hourly weather data

I have hourly weather data for a number of weather stations in radius of some 300 kilometers, for second half of the last century. Missing values range from few hours to a whole month. I am working ...
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0answers
89 views

Correlation coefficient from ACF/PRCF as dependent/response variable

I have multiple, 12-year time-series of species abundance data. I want to model different population properties across spatially and temporally varying predictors. One of the properties I want to ...