Feeding Selectivity and Performance of a Semi-Terrestrial Caddisfly (Trichoptera: Limnephilidae) on Leaf Litter from Native and Invasive Plants

Seasonal biodiversity and productivity of prairie wetlands are dictated by wet and dry cycles (van der Kamp 1995; Whiles and Goldowitz, 2005). These ephemeral systems are greatly influenced by a range of geomorphologic and hydrologic conditions, which alter plant and benthic macroinvertebrate species assemblages (Whiles and Goldowitz, 2001; van der Valk, 2012). Water impoundments that control seasonal flooding and provide irrigation water sources have resulted in increases of woody riparian vegetation in many areas (Johnson, 1994). Increasing concerns over the loss of prairie wetlands have prompted numerous management and restoration projects (Sidle et al., 1989; Currier, 1998; Liske, 2001). In Nebraska, between the towns of Overton and Chapman, most wetland restoration projects are conducted within the Big Bend region of the Platte River Valley (Kessler et al., 2011). Prior to human landscape changes, Platte River riparian communities were regulated by June floods, summer drought, and spring ice scouring; however, changes to the Platte River hydrology and efforts to control fires in riparian areas have allowed invasion by both invasive vegetation and native woody plants and trees (Johnson, 1994). Recently, attention has been given to how invasive riparian plants surrounding the braided Platte River channels are affecting native fauna (Rapp et al., 2012) with special concern for sandhill cranes, Grus canadensis (Kessler et al., 2011) and river otters, Lontra canadensis (Williams, 2011). The semi-terrestrial Platte River caddisfly, Ironoquia plattensis Alexander and Whiles, has a limited distribution and resides in palustrine wetlands along the Platte, Loup, and Elkhorn River systems found in central Nebraska (Vivian et al., 2013). Among the six sites from where I. plattensis was first described, plant communities consisted of native lowland tallgrass prairies with occasional patches of riparian forest (Whiles et al., 1999). Anthropogenic alterations to Nebraska river system hydrology have disrupted the annual maintenance of native plant species (Johnson, 1994), allowing the proliferation of invasive plant communities and modifying allochthonous inputs. Larvae of I. plattensis are coarse particulate organic matter (CPOM) shredders that consume decomposing vegetative material (Whiles et al., 1999). This caddisfly displays an uncommon terrestrial life phase in which it migrates to land in late May. This movement is associated with the drying of its habitat (Whiles et al., 1999; Geluso et al., 2012). Wetlands too ephemeral or permanent are not suitable for Platte River caddisfly (Whiles et al., 1999); occupied sites retain water 75–90% of the time (Goldowitz, 2004). Ironoquia plattensis was first described from an intermittent slough in south-central Nebraska in 1999 (Alexander and Whiles, 2000). When described, I. plattensis attained average aquatic densities of 802 ± 194 larvae per m2, making it the most abundant invertebrate component of the sloughs (Whiles et al., 1999). Because its lifecycle includes a terrestrial aestivation phase, it was also noted that the I. plattensis is likely an important component of energy transfer between the aquatic and terrestrial environments (Whiles et al., 1999). In Nebraska, I. plattensis is listed as a Tier I species, which are those species at-risk of going extinct or becoming threatened, and was petitioned for inclusion as a federally protected species in 2007 (U.S. Fish and Wildlife Service [USFWS] 2009). USFWS decided the species did not warrant federal protection in 2012; however, habitat changes threaten remaining populations (Vivian et al., 2013). These changes include hydrological modifications that allow fish predators to survive in areas occupied by I. plattensis (Cavallaro et al., 2015) and may expose terrestrial pupae to flooding and hypoxia (Cavallaro and Hoback, 2014). In addition to these potential threats, changing plant communities may affect growth and survival of I. plattensis.