Abstract
Adult aquatic insects with a terrestrial life-stage are important vectors transferring resources assimilated in freshwater environments to terrestrial consumers. Research on this linkage has focused particularly on how terrestrial environmental features affect dispersal of adult aquatic insects, and on the responses of terrestrial consumers. However, both the timing and extent of dispersal by adult aquatic insects are further regulated by their species-specific life history traits. We sampled aquatic invertebrates from nine streams in central Sweden, and assessed how the composition of key traits related to dispersal and life history varied between in-stream habitats (riffles, pools), seasons (autumn, spring), and among streams differing in catchment land use (forested, agriculture). Traits indicative of more limited adult dispersal (e.g. small adult size and weak flying strength), along with traits indicative of strongly pulsed peaks in emergence (e.g. univoltinism and well-synchronised emergence) were all more abundant in the agricultural than forested streams in the autumn. However, these differences had disappeared by late spring, possibly reflecting early emergence by the univoltine taxa that dominated the agricultural stream communities and/or elevated mortality in the agricultural streams. Riffles supported higher abundances of insects with strongly flying adults, whereas traits associated with more limited dispersal were characteristic of insect assemblages in pools, which also supported the highest proportion of invertebrates completely lacking an adult flying stage. This result is likely to have implications at larger scales, given the dominance of soft-bottomed pool habitats and scarcity of riffles in many agricultural landscapes. Overall, our analysis indicates that while overall production of aquatic invertebrates with a winged adult was greater in agricultural streams, availability of this productivity for terrestrial consumers is more likely to be spatially restricted closer to the stream channel, and potentially also more temporally pulsed .
Highlights
The transfer of aquatic resource subsidies into terrestrial food webs via the winged adult stages of aquatic insects is recognized as a key component in the functioning of riverine networks (Moldenke and Linden 2007; Lamberti et al 2010; Muehlbauer et al 2014)
Width of the riparian vegetation at the individual sampling reaches differed between the two groups: average widths of riparian vegetation for the four agricultural streams ranged from 5 to 34 m, whereas the forested streams flowed through extensive woodland, extending well over 100 m from the stream channel
Differences between habitats, seasons and land use categories were overall similar for the total abundances of benthic invertebrates both with and without an adult flying stage (Fig. 1)
Summary
The transfer of aquatic resource subsidies into terrestrial food webs via the winged adult stages of aquatic insects is recognized as a key component in the functioning of riverine networks (Moldenke and Linden 2007; Lamberti et al 2010; Muehlbauer et al 2014). Much research attention has focused on how terrestrial environmental features regulate subsidy dispersal and the responses of terrestrial consumers (e.g. forest cover, complexity of ground habitats, availability of terrestrial resources), and on how human activities alter these linkages (Petersen et al 2004; Greenwood and McIntosh 2008; Marczak and Richardson 2008; Stenroth et al 2015) Both the timing and extent of dispersal by adult aquatic insects are further regulated by their species-specific life history traits (Greenwood and Booker 2016). These traits are components of a species’ phenotype that regulate when and how often individuals emerge from the aquatic larval to terrestrial adult state (e.g. voltinism, seasonal syncronicity), and how far from the natal stream individuals might disperse (e.g. adult flying strength, flight distance, body size) (Petchey and Gaston 2006; Truchy et al 2015; Greenwood and Booker 2016), and which thereby influence their availability as resource subsidies to terrestrial consumers in time and space (Table 1)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
