Impacts of Indian waterfern (Ceratopteris thalictroides (L.) Brongn.) infestation and removal on macroinvertebrate biodiversity and conservation in spring‐fed streams in the Australian arid zone

Abstract

Removal of invasive macrophytes is a priority for river managers. However, the ecological effects of macrophyte removal on macroinvertebrate diversity are rarely examined but may be of particular significance in conservation reserves and when threatened species are present. This study investigated the macroinvertebrate fauna inhabiting invasive and native macrophytes in spring‐fed channels in the Millstream‐Chichester National Park, Australia. The effects of waterfern management (periodic hand‐weeding) were examined by comparing assemblages at weeded and unweeded reaches on three occasions. Ceratopteris thalictroides harboured a diverse, insect‐dominated macroinvertebrate assemblage, including the endangered damselfly Nososticta pilbara. Total taxon richness was similar between waterfern and native macrophytes, but macroinvertebrate assemblages differed in the dry season. Damselflies (including N. pilbara) were associated with waterfern‐dominated reaches, whereas dragonfly nymphs were more common among native macrophytes. Weeding altered macroinvertebrate assemblage composition. Some weeded reaches developed assemblages indistinguishable from those in native‐dominated reaches, but others did not. Weeded reaches often supported taxa that were rare or absent from waterfern‐dominated reaches, including suspension feeders, found also in native‐dominated reaches. Odonata are particularly diverse at Millstream, with 18 species recorded. Odonate species richness was significantly lower at weeded reaches than unweeded reaches. Nososticta pilbara and other short‐range endemic species were absent from weeded reaches. As most odonates are univoltine, these adverse effects on local population size may affect species persistence. Invasive macrophyte species may support a high diversity of native invertebrates, including endangered and short‐range endemic species. Furthermore, although hand‐weeding appeared to enable a greater diversity of species to co‐exist, the removal of a large biomass of macrophytes appeared to remove whole cohorts of insect populations from stream reaches, including endangered species. Removal of invasive macrophytes should not be implemented without understanding their effects on invertebrate assemblage composition and life‐cycles.

The impacts of invasive ecosystem engineers in freshwaters: A review

“…were consistently found to be associated with living invasive dreissenid mussels, presumably due to the protection and additional food sources provided by their shells (DeVanna et al, ). Invasive Indian waterfern ( Ceratopteris thalictroides ) also provided the majority of habitat for a short‐range endemic damselfly in the Pilbara, Australia, necessitating careful management of aquatic vegetation (Carey et al, ). Although such relationships may be unusual, it is important that they are identified where they occur, because they can be locally important for preventing extirpation or extinction of threatened taxa.…”

“…However, positive effects of invasive ecosystem engineers have been identified in some cases, and these positive effects have important implications for management of invasive and rare species (e.g. Carey et al, ). Therefore, more studies that are designed to identify positive, negative or minimal impacts on native species or biodiversity are necessary to fully understand and perhaps predict the potential suite of impacts of invasive ecosystem engineers in freshwaters.…”

“…Potentially, invasive ecosystem engineers may have positive, as well as negative effects (e.g. Carey, Strachan, & Robson, ). However, whether the impact of an ecosystem engineer is viewed as positive or negative can be subjective.…”

Short-term effects of macrophyte removal on aquatic biodiversity in rivers and lakes

“…Reduced taxonomic richness was found in a study covering a single river in Australia (Carey et al, 2018), while other studies in lakes and rivers did not find changes in richness (Bickel and Closs, 2009;Ward-Campbell et al, 2017). Shannon-diversity was shown to increase in a study in a river in the U.S. (Lusardi et al, 2018), while other studies in rivers did not detect a change in Shannondiversity (Buczyński et al, 2016;Dabkowski et al, 2016).…”

Outcrossing mating system in natural populations of the endangered aquatic fern Ceratopteris thalictroides in China as revealed by microsatellite markers: implications for conservation

“…In several other countries, including neighboring Vietnam and India, the species is also listed as endangered (Raju, 1983). Earlier studies on C. thalictroides mainly dealt with its distribution, taxonomy, evolution, morphology, ecology, reproductive development, conservation genetics, and molecular biology (Lloyd, 1974a;Hickok et al, 1995;Masuyama et al, 2002;Adjie et al, 2007;Liao et al, 2011;Carey et al, 2018;Chen et al, 2019;Guan et al, 2019). Research on molecular biology has mainly evaluated the genetic diversity, genetic structure, cryptic species status, molecular systematics and phylogeography, and adaptive evolution of C. thalictroides using Simple Sequence Repeat (SSR), RAD-seq, RNA-seq, nrDNA, hemoglobin genes, the MADS-box gene family, and cpDNA rbcL (Adjie et al, 2007;Dong et al, 2008;Masuyama and Watano, 2010;Yang et al, 2016;Qi et al, 2016;Zhang et al, 2020;Kinosian et al, 2020).…”