Contrasting latitudinal patterns in diversity and stability in a high-latitude species-rich moth community

Aim Biodiversity is currently undergoing rapid restructuring across the
globe. However, the nature of biodiversity change is not well understood,
as community‐level changes may hide differential responses in
individual population trajectories. Here, we quantify spatio‐temporal
community and stability dynamics using a long‐term high‐quality moth
monitoring dataset. Location Finland, Northern Europe. Time period
1993–2012. Major taxa studied Nocturnal moths (Lepidoptera). Methods We
quantified patterns of change in species richness, total abundance,
dominance and temporal variability at different organizational levels over
a 20 year period and along a latitudinal gradient of
1,100 km. We used mixed‐effects and linear models to quantify
temporal trends for the different community and stability metrics and to
test for latitudinal (or longitudinal) effects. Results We found
contrasting patterns for different community metrics, and strong
latitudinal patterns. While total moth abundance has declined,
species richness has simultaneously increased over the study period, but
with rates accelerating with latitude. In addition, we revealed a
latitudinal pattern in temporal variability—the northernmost locations
exhibited higher variability over time, as quantified by both metrics of
richness and aggregated species population trends. Main conclusions When
combined, our findings likely reflect an influx of species expanding their
ranges poleward in response to warming. The overall decline in abundance
and the latitudinal effect on temporal variability highlight potentially
severe consequences of global change for community structure and integrity
across high‐latitude regions. Importantly, our results underscore that
increases in species richness may be paralleled by a loss of individuals,
which in turn might affect higher trophic levels. Our findings suggest
that the ongoing global species redistribution is affecting both community
structure and stability over time, leading to compounded and partly
opposing effects of global change depending on which biodiversity
dimension we focus on.