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.

Filter by
Sorted by
Tagged with
2
votes
1answer
223 views

How do I Calculate the odds ratio for a circular predictor variable using the coefficient(s) of a logistic regression?

Using a logistic regression I have modelled the habitat characteristics of a dataset existing out of GPS positions. To visualize the results I want to calculate the odds ratio for each value in my ...
1
vote
2answers
998 views

Pearson and Spearman correlations [duplicate]

I'm having a problem with choosing between Pearson and Spearman correlation. I'd like to understand clearly why I should use one or the other. I have read the questions already asked here about this ...
0
votes
1answer
203 views

Variance in temperature across three sites - 2 way ANOVA?

Example data: ...
2
votes
1answer
325 views

Replicates in Canonical Correspondence Analysis or PERMANOVA

My problem is the statistical analysis of community data with gradients of environmental data. I have a table of species occurrences (from metabarcoding) per sample site and measurements of ...
0
votes
1answer
167 views

Statistical test for comparing species diversity based on frequency at two points

I am trying to quantify similarity between these two locations taking into account species frequency: Chicago   Blue Jay: 0.79   American Crow: 0.25   Blackpoll ...
2
votes
1answer
1k views

Fitting and interpreting random effects in repeated measures and unbalanced ecological data set

I have a vegetation data set that consists of 150 plots that were sampled 1-3 times over a three year period. Plots are my unit of observation and they are unbalanced (since plots were sampled either ...
3
votes
2answers
2k views

GLMM- relationship between AICc weight and random effects?

I am developing GLMM's in order to assess habitat selection (using GLMMs' coeficients to construct Resource selection functions). I have (telemetry) data from 5 study areas, and each area has a ...
0
votes
1answer
45 views

randomization test on differences

I have three treatments (A, B, and C) that I would like to compare. However, within each treatment, I have nested "high" and "low" (H and L) treatments. The values for A, B, and C must be calculated ...
1
vote
1answer
122 views

Habitat as fixed factor with a nested design

I have the following design: Two regions, in each region 6 sites, in each site three habitats and in each habitat 4 100m2 plots. Then, in each site 12 plots (3 habitats, 4 plots). For each site I ...
1
vote
2answers
577 views

GLMM: relationship between AIC, R squared and overdispersion?

First of all, I am a beginner in statistics, and I have been reading some questions and comments here regarding this matter but I am still a bit lost. My problem: I am constructing GLMM's in order to ...
8
votes
3answers
6k views

Variance of a distribution of multi-level categorical data

I am currently analyzing large data sets with various characteristics (such as city). I wanted to find a measure which would essentially say how much or how little of a variance there was across the ...
7
votes
3answers
394 views

Can I test for correlation between variables before standardize them?

What I want to do is to construct GLMM's to evaluate resource selection, and I have a set of variables (some representing distances and others representing % of land cover). Can I test for ...
3
votes
1answer
63 views

Can I reduce the AICc penalty for multiple variables, when some variables should be grouped?

I have a data set of mean trait values for each of 18 populations, and want to test whether several ecological variables are related to variation in traits. I'm using the corrected Akaike information ...
2
votes
2answers
754 views

How do I avoid multiple t-tests (or is it ok to use multiple t tests here?)

I've searched around CV for a bit, and have not found a good answer as to what test to use instead of multiple t-tests in my particular situation. I am interested in comparing mean size (of fish) ...
1
vote
0answers
588 views

Permanova for microbial ecology using adonis (R): should I include block?

I know this is a very basic question, but I have been quite unsuccessful in finding a good solution to the following issue. First the data. My spreadsheet is too big, so here is a fictional example: ...
1
vote
0answers
107 views

What would be the best analysis / analyses for the over time coral bleaching recovery data?

I am analyzing this MISeq microbial community data with Phyloseq and vegan R-packages from coral hosts and I would much appreciate some help and ideas as this is my first analysis of this kind. We ...
0
votes
1answer
77 views

Correlation between several variables in different study areas

I want to test the correlation between variables considering several study areas. I aim to study habitat selection using telemetry data (locations) in five study areas, and I have variables regarding ...
3
votes
1answer
2k views

When to use distance biplot vs. correlation biplot in PCA

I wonder what could be good examples of using scaling 1 and 2 for a principal component analysis biplot. By examples, I mean ecological examples or applied examples of the PCA scaling so that one can ...
3
votes
0answers
112 views

Lack of independence - how to analyze data from a time-series that are spatially correlated? [closed]

I am dealing with a species distribution. From aerial imagery, the species' presence has been assessed at specific locations by identifying the presence/absence of the species of interest under 9500 ...
1
vote
0answers
218 views

Most appropriate test for count data

So I've performed an experiment whereby I had 12 1km transects. 6 of these were along rivers running through agricultural land and 6 through woodland. These were arranged in pairs so that each agri ...
1
vote
0answers
19 views

Different Effects of Detection Probability Between Presence and Count Data at the Same Location

I'm modeling habitat suitability for a large, mobile animal using occurrence data (presence only---I have no true absence data in this case) collected from camera traps (stations with automatic motion/...
4
votes
1answer
226 views

Multivariate Analysis of Ecological Data: Procrustes analyses or GLM?

I have a dataset containing 6 variables (vegetation cover in percent) and the number of species found in 30 areas. I would like to test if the different vegetation covers explain species richness. ...
6
votes
1answer
281 views

Check for significant difference between numbers of sightings per cardinal direction

I have data in a form like this: quantity direction 10 n 5 e 6 ne 12 n 20 nw 5 s 8 n 1 sw 3 se 2 ne 6 nw 8 n 2 se 3 e 4 w 9 nw The information behind these ...
2
votes
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) ...
8
votes
1answer
9k views

Interpreting output of dredge

I ran a GLM for the first time in R and am not sure how to interpret the result. This is the input: ...
0
votes
1answer
415 views

Row normalization before correlation analysis for abundance data

I work with datasets in which protein abundances are reported across samples. I have some measurements of biological samples that should be more or less equal in protein abundance. After getting ...
2
votes
1answer
1k views

GLM - which probability distribution to use for abundance data?

I'm fitting a generalized linear model to try to understand how the abundance of a species of freshwater fish varies in response to some environmental variables. I'm using the AIC to choose between ...
1
vote
0answers
48 views

How to incorporate intraspecific variation in discrete characters in comparative analysis?

I'd like to run a multivariate analysis (Pavoine et al. 2011) that aims to disentagle the effect of environmental gradients on traits, considering its autocorrelation with phylogeny and space. It uses ...
1
vote
1answer
1k views

GLMM or LME? Repeated measures help?

I am having trouble using the correct test and r code for my experiment. Essentially I measured insect emergence daily from artificial streams with 3 treatments.: ...
1
vote
1answer
54 views

Test if number of fish differ by location

I have a dataset which consists of location ID's (1 to 29 different locations) and each location has a couple of repeated measures (max n = 780, min n = 50). Each measurement consists of a number of ...
3
votes
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 ...
3
votes
1answer
2k views

Time-series analysis of categorical data

I am attempting to look at nest attendance patterns in birds. I have a dataset looking at 5 nests, every 5 minutes I assessed whether the male=1, female=2, both birds=3 or no birds=4 were at each nest....
2
votes
1answer
81 views

Final test for statistical significance of bird aggression scores

Introduction I'm doing a small pilot research in bird aggression in a colonising frontier regarding their breeding ground. Background The study was conducted over multiple years, presenting the ...
7
votes
1answer
5k views

Principal component analysis with group data

In my experiment I have used 30 different accessions of a species. One group is challenged drought and the other group is control. I have collected data on 6 different parameters. I want to know which ...
4
votes
1answer
64 views

Comparing two groups: a risk of pseudoreplication

I am growing coral on two different structures. I want to compare whether one structure (a table) grows coral more quickly than the other one (a tree). Both structures hold 60 pieces of coral, so a ...
2
votes
2answers
1k views

mixed effects and lme4: Do I need nesting?

I am analyzing data from a field experiment, and I am interested in the effects of fauna and altitude (fixed). Altitude has two levels, and at each site I have 5 blocks for the three levels of fauna (...
0
votes
0answers
29 views

Generalized Linear (Mixed) Modelling for different scales

I am struggling conceptually with how I can best model my dataset. My data is the abundance of spiders collected from 20 permanent traps in a forested area. These traps have been repeatedly re-...
1
vote
1answer
28 views

What's the best statistical method for comparing perceived versus measured ecological functioning?

I'm comparing survey results of respondents' perceptions of creek environmental health to environmental health as measured by scientists with the city. What's the best way to analyze the difference?
1
vote
1answer
33 views

Causation in an agroecosystem?

I'm working in an agroecosystem with one specific crop and am interested in understanding how certain treatments influence given ecosystem characteristics (such as soil organic carbon). Variables that ...
1
vote
1answer
3k views

Why is a correlation coefficient threshold of r = 0.6 among predictors commonly used in ecology?

In my field of study (wildlife ecology), a correlation coefficient of r = 0.6 is a commonly-used threshold for identifying collinearity among pairs of predictor variables. In other words, predictors ...
1
vote
0answers
3k views

What is PERMANOVA and when to use it instead of multivariate ANOVA?

I have some data on spatial and temporal variation of macrobenthic species. I tried to test the difference between seasons and sites, and noticed that PERMANOVA is recommended in the literature. (But ...
0
votes
1answer
95 views

Outputting indicative variables within a specific factor

I have a dataset on bugs that has been processed to incorporate a series of traits (e.g. size; feeding habitats) through displaying proportional values of different properties (e.g. small, medium, ...
4
votes
1answer
1k views

Ecological modelling: multivariate abundance time-series data

I am working with a dataset that consists of abundance counts of 6 microbial taxa in a lake measured weekly for 20 weeks. I also have environmental data (temperature, nutrient concentrations, ...
0
votes
0answers
105 views

Occupancy vs mark-recapture?

What are the differences between occupancy models and mark-recapture in ecology? As I understand it, we use occupancy models when we aren't sure if detectability is a given (not sure of presence/ ...
2
votes
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
votes
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 ...
3
votes
0answers
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 ...
1
vote
0answers
187 views

Multinomial response with repeated measures

I'm studying how sex influences habitat use. I'm looking for suggestions on how to analyze a repeated measure design with a multinomial response variable. I should note that the number of repeated ...
0
votes
1answer
129 views

Vectors for biodiversity indices in RDA plot

I'm doing partial distance based (db-)RDA analysis of nematode community data. I have got the triplots already. They contain vectors of environmental data. Is it possible to overlay a second set of ...
1
vote
0answers
82 views

Detrended correspondence analysis

I have relative abundance data of monkey species in 4 different types of habitat. I would like to use detrended correspondence analysis. Is this a correct way to display my data? If so, how should I ...