Assessing the contribution of recorder effort to the occurrence of
JTM
In order to assess whether recorder effort affected the distribution of
known occurrences of JTM throughout the study region, four generalised
linear mixed models (GLMMs; one for each data source) were constructed.
GLMMs were constructed for the years 2016–2018, with the
presence/pseudo-absence of JTM throughout the study region as a binary
response variable. Recorder effort, habitat suitability from the
historic model, and the interaction between the two were predictor
variables in each model. Year was included as a random effect to account
for a lack of independence between years. As above, AIC selection was
then implemented to select the best model. Habitat suitability and
recorder effort were both standardised by subtracting their mean and
dividing by their standard deviation. GLMMs were constructed using theglmmTMB package and had a binary error structure and a logit link
function.
All analyses were conducted in R version 4.0.037. Code
is available from https://github.com/nis38/JTM.