Vebrová et al. BMC Ecol (2018) 18:19 https://doi.org/10.1186/s12898-018-0175-y BMC Ecology RESEARCH ARTICLE Open Access Seasonality and weather conditions jointly drive fight activity patterns of aquatic and terrestrial chironomids Lucie Vebrová1, Andre van Nieuwenhuijzen2, Vojtěch Kolář1,3 and David S. Boukal1,3* Abstract Background: Chironomids, a major invertebrate taxon in many standing freshwaters, rely on adult fight to reach new suitable sites, yet the impact of weather conditions on their fight activity is little understood. We investigated diel and seasonal fight activity patterns of aquatic and terrestrial chironomids in a reclaimed sandpit area and ana- lysed how weather conditions and seasonality infuenced their total abundance and species composition. Results: Air temperature, relative humidity, wind speed, and air pressure signifcantly afected total fight activity of both groups, but not in the same way. We identifed an intermediate temperature and humidity optimum for the fight activity of terrestrial chironomids, which contrasted with weaker, timescale-dependent relationships in aquatic species. Flight activity of both groups further declined with wind speed and increased with air pressure. Observed fight patterns also varied in time on both daily and seasonal scale. Flight activity of both groups peaked in the evenings after accounting for weather conditions but, surprisingly, aquatic and terrestrial chironomids used partly alternating time windows for dispersal during the season. This may be driven by diferent seasonal trends of key environmental variables in larval habitats and hence implies that species phenologies and conditions experienced by chironomid larvae (and probably other aquatic insects with short-lived adults) infuence adult fight patterns more than weather conditions. Conclusions: Our results provide detailed insights into the drivers of chironomid fight activity and highlight the methodological challenges arising from the inherent collinearity of weather characteristics and their diurnal and seasonal cycles. Keywords: Aquatic insects, Dispersal, Seasonality, Environmental conditions, Collinearity Background or populations [2]. While zooplankton disperses mostly Long-term survival of species in changing environments as resting eggs, nearly all aquatic insects disperse depends on the ability of local populations to reach new between discrete localities by fight as adults [3]. Teir suitable sites [1, 2]. Tis is particularly true for biota in seasonal fight patterns refect species phenologies and highly dynamic, small standing freshwaters [3]. Domi- long-term environmental conditions afecting the pre- nant invertebrate groups occupying these habitats utilize adult stages. diferent strategies for dispersal, defned as any move- Various biotic and abiotic factors, including weather ment between spatially or temporally discrete localities conditions, provide environmental flters that modify adult fight patterns on daily timescales [4]. Tese con- straints ultimately shape dispersal patterns of aquatic *Correspondence: [email protected] insects at diel and seasonal timescales [5–7] that may 1 Department of Ecosystem Biology, Faculty of Science, University afect community assembly through priority efects [8] of South Bohemia, Branišovská 31a, 37005 Ceske Budejovice, Czech Republic and metapopulation dynamics [9]. However, teasing apart Full list of author information is available at the end of the article the contribution of species phenology and environmental © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/ publi​cdoma​in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Vebrová et al. BMC Ecol (2018) 18:19 Page 2 of 13 conditions to fight patterns is inherently difcult due to of dispersal activity of aquatic insects. Chironomids liv- ubiquitous strong collinearity of environmental variables ing in standing waters can move between diferent micro- and their seasonality in many ecosystems [10]. habitats within the same water body as frst-instar larvae Flight activity of aquatic insects is strongly afected by [27], but cannot cross land in the larval stage. Adult fight weather conditions including air temperature [6, 11, 12], is therefore crucial for their dispersal between water bod- wind speed [12–14], light intensity [15, 16], and relative ies, while terrestrial species in more contiguous habitats air humidity (i.e., the amount of water vapour in the air might in principle combine dispersal in both larval and relative to the full saturation) [17, 18]. Weather condi- adult stage. Previous comparisons of aquatic species (i.e., tions thus represent a strong environmental flter [19, with larvae living in various aquatic habitats) and terres- 20] that ultimately afects individual ftness. Temperature trial species (i.e., with larvae living in wet soil or damp can drive species composition of the colonizing insects vegetation [27]) of chironomids focused only on difer- because few individuals fy at temperatures outside the ences in spatial distribution [34, 35]. species-specifc thermal windows of fight activity [16]. Te main purpose of this paper was to investigate and Relative air humidity provides an important constraint compare the diel and seasonal fight activity patterns of as fight during inappropriate conditions may increase aquatic and terrestrial chironomids, focusing on their the risk of dehydration and mortality as lower relative assemblage in a reclaimed sandpit as a case study. We humidity leads to faster drying [5]. Joint impact of air characterized the patterns and disentangled the efects of temperature and relative humidity on fight activity of temporal and environmental factors on fight activity of aquatic insects was recognized for many groups [21–23] both groups. We expected a strong dependence of fight including chironomids [24], but the individual contribu- activity on wind speed, temperature and relative humid- tions of humidity and temperature are often difcult to ity because chironomids rely on dispersal by wind and separate due to their collinearity [10]. Dispersal fight of have relatively soft bodies, but had no a priori expecta- aquatic beetles and heteropteran bugs is further inhibited tion on the diferences between fight patterns of aquatic by wind [13, 14] and modifed by light intensity and solar and terrestrial species. elevation, which determines the amount of horizontally polarized light refected by water surface that helps indi- Methods viduals locate suitable habitats and oviposition sites [25]. Study site To our knowledge, the joint efects of weather condi- Te study was carried out in the Cep II sandpit near Such- tions and seasonality on fight activity in aquatic insects dol nad Lužnicí, Czech Republic (GPS 48°91′85.51′′N, were studied only in stream Plecoptera [12] and Culi- 14°87′42.58′′E). Most of the sandpit area is covered by a coides biting midges [23] but are virtually unknown in deep and turbid lake with ongoing sand extraction [36]. chironomids, a highly speciose and abundant macroin- Shore area in the south-western part of the sandpit was vertebrate group in fresh waters [26]. Chironomids are remodelled and a cluster of ca. 40 small temporary to generally poor fiers that disperse by wind [27] rather permanent pools (clayey-sandy bottom, surface area: 2 than through self-propelled fight within their ‘fight mean ± SD = 8.6 ± 3.5 m ; depth, 0.28 ± 0.09 m) created boundary layer’ (sensu [28]). Te adults are mostly short there in October 2012 to conduct a community assem- lived [29] and their presence is driven by larval phenol- bly experiment. Aquatic invertebrates began to colonize ogy, while weather conditions strongly afect their fight the pools in early 2013 (Boukal et al. unpublished data). activity that should primarily relate to reproduction and Immediate vicinity of the pools consisted of bare clayey- oviposition, although adults may also seek plant food sandy ground with very sparse cover of herbs and no sources such as nectar, pollen and honeydew [27, 30, 31]. shrubs. We sampled fying chironomids near the pools Small and soft-bodied insects such as chironomids (Additional fle 1: Figure S1) using two standard methods: are also more vulnerable to weather conditions because sweeping with a hand-held aerial net and Malaise traps. they can cool down, overheat or desiccate rapidly [10] and stop fying in strong winds [32]. Tese diferences in Diel fight activity in autumn 2013 key individual characteristics related to dispersal suggest To observe the diurnal fight patterns of chironomids and that environmental conditions may afect chironomids select the method for the subsequent long-term study, we diferently from other aquatic insect groups, with poten- sampled fying insects with a handnet and Malaise traps tial implications for the process of colonization of new for 8 days in late summer (11–15 August and 23–25 Sep- habitats and local community assembly [33]. Moreover, tember 2013). Sweeping was carried out with a handnet chironomids include both aquatic and terrestrial