Data from: Contrasting impacts of precipitation on Mediterranean birds and butterflies

The climatic preferences of the species determine to a large extent their
response to climate change. Temperature preferences have been shown to
play a key role in driving trends in animal populations. However, the
relative importance of temperature and precipitation preferences is still
poorly understood, particularly in systems where ecological processes are
strongly constrained by the amount and timing of rainfall. In this study,
we estimated the role played by temperature and precipitation preferences
in determining population trends for birds and butterflies in a
Mediterranean area. Trends were derived from long-term biodiversity
monitoring data and temperature and precipitation preferences were
estimated from species distribution data at three different geographical
scales. We show that population trends were first and foremost related to
precipitation preferences both in birds and in butterflies. Temperature
preferences had a weaker effect on population trends, and were significant
only in birds. The effect of precipitation on population trends operated
in opposite directions in the two groups of species: butterfly species
from arid environments and bird species from humid habitats are decreasing
most. Our results indicate that, although commonly neglected, water
availability is likely an important driver of animal population change in
the Mediterranean region, with highly contrasting impacts among
taxonomical groups.