TY - JOUR
T1 - Direct and indirect effects of native plants and herbivores on biotic resistance to alien aquatic plant invasions
AU - Petruzzella, Antonella
AU - van Leeuwen, Casper H.A.
AU - van Donk, Ellen
AU - Bakker, Elisabeth S.
PY - 2020/7/1
Y1 - 2020/7/1
N2 - Biotic resistance to alien plant invasions is mainly determined by ecological interactions in two layers of the food web: competition with native plant species and herbivory by native herbivores. While the direct effect of native plants on alien plant performance via competition has been well documented across ecosystems, less is known about the direct and indirect effects of herbivores in providing biotic resistance. Our main aims were to determine whether temperate native aquatic plants and herbivores can provide biotic resistance to plant invasions, understand the underlying mechanisms and search for potential interactive effects of competition and herbivory on invader performance (i.e. growth). We mimicked natural temperate mesotrophic and eutrophic freshwater lakes in mesoscosms, by growing three native submerged plant species in monocultures (Ceratophyllum demersum, Myriophyllum spicatum and Potamogeton perfoliatus) at three competition levels (no, low and high) without and with the native aquatic generalist snail Lymnaea stagnalis. We subsequently simulated an early stage of establishment of the South American highly invasive alien plant species Egeria densa. We found that competition by native plant biomass significantly reduced invader performance but depended on native species identity. Herbivory had no direct negative effect on invader performance as the snails fed mainly on the available filamentous algae, which are commonly found in meso- and eutrophic systems, instead of on the plants. However, the consumption of filamentous algae by herbivores indirectly had positive effects on the invader total biomass, thus facilitating the invasion by E. densa. Nonetheless, these indirect effects worked through different pathways depending on the native plant identity. Synthesis. We found evidence for biotic resistance through competition by native plant species. However, we show that herbivores can indirectly facilitate South American plant E. densa invasion promoting its growth through selective feeding on filamentous algae, but this effect depends on the native plant species involved. Our experiment illustrates the important role of indirect interactions to understand the potential of biotic resistance in natural ecosystems.
AB - Biotic resistance to alien plant invasions is mainly determined by ecological interactions in two layers of the food web: competition with native plant species and herbivory by native herbivores. While the direct effect of native plants on alien plant performance via competition has been well documented across ecosystems, less is known about the direct and indirect effects of herbivores in providing biotic resistance. Our main aims were to determine whether temperate native aquatic plants and herbivores can provide biotic resistance to plant invasions, understand the underlying mechanisms and search for potential interactive effects of competition and herbivory on invader performance (i.e. growth). We mimicked natural temperate mesotrophic and eutrophic freshwater lakes in mesoscosms, by growing three native submerged plant species in monocultures (Ceratophyllum demersum, Myriophyllum spicatum and Potamogeton perfoliatus) at three competition levels (no, low and high) without and with the native aquatic generalist snail Lymnaea stagnalis. We subsequently simulated an early stage of establishment of the South American highly invasive alien plant species Egeria densa. We found that competition by native plant biomass significantly reduced invader performance but depended on native species identity. Herbivory had no direct negative effect on invader performance as the snails fed mainly on the available filamentous algae, which are commonly found in meso- and eutrophic systems, instead of on the plants. However, the consumption of filamentous algae by herbivores indirectly had positive effects on the invader total biomass, thus facilitating the invasion by E. densa. Nonetheless, these indirect effects worked through different pathways depending on the native plant identity. Synthesis. We found evidence for biotic resistance through competition by native plant species. However, we show that herbivores can indirectly facilitate South American plant E. densa invasion promoting its growth through selective feeding on filamentous algae, but this effect depends on the native plant species involved. Our experiment illustrates the important role of indirect interactions to understand the potential of biotic resistance in natural ecosystems.
KW - alien invasive species
KW - aquatic macrophytes
KW - biological invasion
KW - competition
KW - Egeria densa
KW - freshwater ecosystems
KW - herbivory
KW - plant–herbivore interactions
UR - http://www.scopus.com/inward/record.url?scp=85081977629&partnerID=8YFLogxK
U2 - 10.1111/1365-2745.13380
DO - 10.1111/1365-2745.13380
M3 - Article
AN - SCOPUS:85081977629
SN - 0022-0477
VL - 108
SP - 1487
EP - 1496
JO - Journal of Ecology
JF - Journal of Ecology
IS - 4
ER -