Data from: Combining geostatistical and biotic interactions modelling to predict amphibian refuges under crayfish invasion across dendritic stream networks

Aim: Biological invasions are pervasive in freshwater ecosystems, often
causing native species to contract into areas that remain largely free
from invasive species impacts. Predicting the location of such ecological
refuges is challenging, because they are shaped by the habitat
requirements of native and invasive species, their biotic interactions,
and the spatial and temporal invasion patterns. Here we investigated the
spatial distribution and environmental drivers of refuges from invasion in
river systems, by considering biotic interactions in geostatistical models
accounting for stream network topology. We focused on Mediterranean
amphibians negatively impacted by the invasive crayfishes Procambarus
clarkii and Pacifastacus leniusculus. Location: River Sabor, NE Portugal
Methods: We surveyed amphibians at 168 200-m stream stretches in 2015.
Geostatistical models were used to relate the probabilities of occurrence
of each species to environmental and biotic variables, while controlling
for linear (Euclidean) and hydrologic spatial dependencies. Biotic
interactions were specified using crayfish probabilities of occurrence
extracted from previously developed geostatistical models. Models were
used to map the distribution of potential refuges for the most common
amphibian species, under current conditions and future scenarios of
crayfish expansion. Results: Geostatistical models were produced for eight
out of 10 species detected, of which five species were associated with
lower stream orders and only one species with higher stream orders. Six
species showed negative responses to one or both crayfish species, even
after accounting for environmental effects and spatial dependencies. Most
amphibian species were found to retain large expanses of potential habitat
in stream headwaters, but current refuges will likely contract under
plausible scenarios of crayfish expansion. Main conclusions: Incorporating
biotic interactions in geostatistical modelling provides a practical and
relatively simple approach to predict present and future distributions of
refuges from biological invasion in stream networks. Using this approach,
our study shows that stream headwaters are key amphibian refuges under
invasion by alien crayfish.