Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets

Abstract

Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed that diversity indices were not significantly different between exotic and native plant communities, but the total abundance of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites-Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense, Spartina invasions in the Yangtze River estuary need to be managed appropriately.

Effects of non-native Spartina patens on plant and sediment organic matter carbon incorporation into the local invertebrate community

“…In contrast, Denno (1980) reported that during the summer, the population of sap-feeding insects on large patches (500-1,000 m 2 ) of S. patens in a New Jersey coastal marsh was high and the effects of feeding and oviposition were evident by the deterioration of the grass over time. Our results also differ from those of Wu et al (2009), which suggested that some native taxa, katydids (F. Tettigoniidae) and crickets (F. Gryllidae), preferred the exotic Spartina (S. alteniflora) over the native Phragmites australis in a salt marsh in the Yangtze River estuary (China). We conducted our sampling during late May, a time period likely to have a high abundance of both enchytraeids and insects, and high food resource use in the study region.…”

“…The impact of Spartina invasions on low intertidal and non-vegetated mudflat habitat has received considerable attention recently (e.g., Dethier and Hacker 2005;Neira et al 2005;Cheng et al 2006; Levin et al 2006;Wu et al 2009). However, there remains a paucity of information on the ecological effects of Spartina invasions on the upper salt marshtransition habitat although there is reason to believe that such effects may be appreciable.…”

“…However, less herbivory may occur on S. patens in invaded habitat if insect herbivores that would normally feed on this plant within its native range are absent. Little information is available on the use of non-indigenous Spartina by native insect herbivores (reviewed by Maron and Vilà 2001; but see Wu et al 2009).…”

“…Herbivorous insects can feed extensively on and adversely influence S. patens in its native habitat (Denno 1980). Stable isotope analysis has been widely used to evaluate the contribution of C 3 versus C 4 plantderived carbon to SOM (e.g., Boutton 1996;Cheng et al 2006), and to the diets of soil detritivores (Martin et al 1992;Briones and Schmidt 2004) and herbivorous arthropods (Fry et al 1978;Petelle et al 1979;Gratton and Denno 2006;Wu et al 2009). Because isotopic differences between C 3 and C 4 plants are large (typically at least 10%, reviewed in Fry 2006), we predicted that SOM in the Spartina zone would be 13 C-enriched compared to SOM associated with native C 3 plants.…”

Macroinvertebrate Prey Availability and Fish Diet Selectivity in Relation to Environmental Variables in Natural and Restoring North San Francisco Bay Tidal Marsh Channels

“…Bollens, WSU, unpublished data, 2013), evidence from the Yangtze River estuary suggests that spatial variation among zooplankton communities corresponds to changes in salinity, while temporal variation results from shifts in water temperature, chlorophyll α concentration, and pH (Zhou et al 2009). Similarly, use of interior marsh channels by neustonic invertebrates is rarely described, but more general studies on salt-marsh arthropod communities indicate that salinity, vegetation assemblage, vegetation coverage, and inundation regime strongly influence the abundance and assemblage structure of these organisms (Stocks and Grassle 2003;Petillon et al 2008;Wu et al 2009;Reynolds and Boyer 2010).…”