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q-bio.PE · Populations and Evolution

Equal-count sampling removes the recorded decrease in moth list differences at 19 Finnish traps from 1993–1999 to 2013–2019

We tested whether moth communities at fixed Finnish light traps became more alike between 1993–1999 and 2013–2019. The open Nocturna archive gave 19 traps, 211 eligible trap-years and 171 trap pairs. We selected three years per trap and period. We compared full catches with samples of 500 moths per year, drawn without replacement, in 400 repeats. Full-catch Sørensen dissimilarity decreased by 0.0253. Its descriptive 95% interval from 100 km spatial blocks was −0.0376 to −0.0065. With equal counts, the change was +0.0021 (−0.0089 to +0.0187). A paired comparison with the same selected years gave a shift of +0.0269 (+0.0046 to +0.0460) after count control. Exact expected richness in equal-count pools rose from 181.2 to 194.0 species. All seven other count-controlled list checks had intervals that included zero. Count control changes the weight of rare species. This result does not prove that the full-catch signal is an observation error. The sample spans 59.8–64.8 degrees north and cannot represent all of Finland. We do not identify a climate or habitat cause. The package includes the unmodified source archive, code, provenance, figures, results and repeat instructions.

moth monitoring · Finland · community composition · rarefaction · spatial dissimilarity · sampling · biodiversity

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References

8
  1. usesTotal macro-moth catch in Finnish light traps decreased in 1993–2012 but was 29% above that trend in 2013–2019, so the 1993–2019 trend was near zero sci:sha256:d822a63b1c4cd0121a7355ecdc2a96b5e0ead210d99b084ab04c9d55c4560226

    We use its retained Nocturna source archive and its trap and species-name conventions. We test spatial differences between fixed traps.

  2. usesdoi:10.15468/j82xqf

    This is the open Finnish National Moth Monitoring source dataset.

  3. doi:10.1111/geb.13073

    This study reports rising richness and falling moth abundance in 1993–2012.

  4. doi:10.1111/icad.12657

    This study tests biomass trends at 85 Finnish moth traps in 1993–2019.

  5. doi:10.1111/1365-2656.70107

    This study shows that climate and habitat effects depend on site and species context.

  6. usesdoi:10.1111/j.1466-822X.2006.00214.x

    We use the definition of homogenization as an increase in similarity over time.

  7. usesdoi:10.2307/1934145

    We use count rarefaction, an established finite-sample method.

  8. usesdoi:10.1111/j.1466-8238.2009.00490.x

    We use the turnover and nestedness partition in an exploratory diagnostic.

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