DOI: 10.5061/dryad.fg8f6
title: Data from: Massive structural redundancies in species composition patterns of floodplain forest moths

description: Terrestrial arthropod communities usually consist of very large species
 numbers. Data from experiments or long time-series would be required to
 ascertain the functional significance of individual species. Both are
 largely unavailable for species-rich natural communities. Recognising
 structural redundancies in species composition allows for an alternative
 approach to address how strong functional redundancy might be in natural
 assemblages, if structural and functional redundancies are related to each
 other. Determining structural redundancies is a regular topic in aquatic
 ecology, but has rarely been applied to terrestrial communities. We
 explored the extent of structural redundancy in species-rich terrestrial
 insect assemblages and whether structural redundancies are contingent to
 species abundances or functional group affiliations. We used the BVSTEP
 algorithm to determine structural redundancies in a large data set of moth
 species (32 181 individuals; 448 species) that had been sampled with
 light-traps in three different floodplain forests in eastern Austria. We
 partitioned the moth species into 12 functional types based on larval
 host-plant affiliations to test if moth species included in reduced
 subsets represent functional groups in the same proportions as they occur
 in the entire fauna. We observed far more massive structural redundancies
 in moth assemblages than previously found in aquatic communities. Subsets
 containing only 8–15 species (1.8–3.3% of all recorded species) were still
 highly representative for the overall data. Subsets selected by the BVSTEP
 procedure performed better than equally small subsets that were defined
 solely by species abundances or by functional group affiliations.
 Effective ‘surrogate’ subsets contained only 6–9 of the 12 functional moth
 types. High abundance only loosely corresponded with the frequency at
 which a moth species was included in the subsets. Thus, certain uncommon
 species contribute importantly to species composition patterns. Our
 results show unexpectedly extensive structural redundancies in complex
 floodplain forest moth communities, which may also indicate strong
 functional redundancies.
description: Classification of moth
 species into 12 functional groups according to larval feeding
 relationships.Moths have been sampled
 in three floodplain forest regions in eastern Austria (along the rivers
 Danube, Morava and Leitha) which differ in flood regimes and forest
 vegetation. Each region contained two classes of forest habitats: ones
 that are regularly inundated once a year, and others that are not or only
 rarely flooded. In each forest habitat five light trap sites were selected
 at a distance of about 100 m from each other to avoid interference between
 traps. In the Leitha floodplain only four light traps were used because of
 the small size of remaining forest fragments. Automatic low-power light
 traps, each equipped with two 15 W lamps (Sylvania Blacklight-Blue,
 F15W/BLB-T8; and Philips TLD, 15W/05) and powered by a 12V car battery
 were placed about 1 m above ground under a closed forest canopy and run
 once a month during the vegetation period (March to November) at each of
 the 28 sites. Light traps within one habitat were operated simultaneously.
 At dusk the light was automatically switched on and run for about 6 hours.
 All 6 forest habitats were sampled on consecutive days, or as soon as
 possible if spells of unfavourable weather had to be avoided. Traps were
 never run during the 5 days before and after full moon to avoid any
 negative impact of moonlight on trap catches. Sampling did not take place
 during rainy weather, in which cases sampling was postponed until
 conditions improved, i.e. sampling was carried out on the next possible
 night with better weather conditions. Altogether, sampling was conducted
 over two complete annual cycles on 103 nights between 20.VIII.2006 and
 24.VIII.2008. The sampling season ended with the first incidence of frost
 in autumn (last sampling dates: 26.XI.2006 and 08.XI.2007) and started
 again at spring time (first sampling dates: 26.III.2007 and 07.IV.2008).
 In all, data from 442 nightly trap samples were analysed. The number of
 moths caught during a single trap night ranged from 0 to 1092 (site MF5,
 08.VIII.2007) individuals. Eighteen nightly trap samples did not contain
 any moths, likely due to cold temperatures and generally low moth activity
 in March, April, October and November. Three further samples did not
 contain moths due to equipment failure. Further information: Truxa, C.
 2012. Community ecology of moths in floodplain forests of Eastern Austria.
 Doctoral dissertation, University of Vienna. URL:
 http://othes.univie.ac.at/25605/Appendix_3.xlsx