DOI: 10.5061/dryad.905qfttgj
title: Contrasting latitudinal patterns in diversity and stability in a high-latitude species-rich moth community

description: 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.
description: The National Moth Monitoring scheme is coordinated by the Finnish
 Environment Institute (SYKE), running annually since 1993 (Leinonen
 <i>et al.</i>, 2016, 2017). Nocturnal moths were sampled using
 “Jalas” light traps (Jalas, 1960) equipped with Hg vapour bulbs, located
 mainly in forested areas across Finland (66% of the traps). The traps were
 located in the same location from year to year and usually emptied weekly.
 Sampling occurs every night from early spring (after snowmelt) to late
 autumn (night frosts and at least one empty trapping period, i.e. one
 week). Sampling effort is constant across years for each trap, but as
 sampling aims to cover the entire moth activity period at each location,
 the trapping period is longer in more southern traps. Voluntary observers
 identified the specimens (Leinonen <i>et al.</i>, 2016), with
 variable number of traps being sampled per year. The
 data used here consists of records of abundance per species collected from
 65 traps (unique Trap Code, with unique coordinates) with at least 8 years
 of sampling between 1993 and 2012. We used data sampled between April and
 October (sparse records outside this period were excluded). The data
 included observations of over 4 million individuals and 782 taxa, and
 specifically 734 moth species. For the species richness and stability
 metrics, records not identified to the species level were excluded, but
 such records were included for measures of abundance.
   Leinonen, R., Pöyry, J., Söderman, G. & Tuominen-Roto, L. (2016) <i>Suomen yöperhosseuranta (Nocturna) 1993-2012 [The Finnish moth monitoring scheme (Nocturna) 1993-2012]</i>, Suomen ympäristökeskuksen raportteja, 15/2016. Leinonen, R., Pöyry, J., Söderman, G. & Tuominen-Roto, L. (2017) Suomen yöperhosyhteisöt muutoksessa – valtakunnallisen yöperhosseurannan keskeisiä tuloksia 1993–2012. <i>Baptria</i>, <b>42</b>, 74–92.
description: Data files contain the necessary data to perform the analyses in
 the linked manuscript. For each Trap, we report their unique location
 coordinates and bioclimatic zone within Finland (from south to north: HB=
 Hemi-Boreal; SB= South-Boreal; MB= Mid-Boreal; NB=
 North-Boreal). File "Trap_Year_diversity.csv"
 contains the number of species, total abundance (i.e. total number of
 individuals) and dominance (i.e. number of individuals of the most
 abundant species) sampled in each Trap and Year. File
 "Trap_stability_synchrony.csv" contains stability and synchrony
 values per Trap.