Study species
P. crispus (curly-leaf pondweed) is native to Eurasia and
invasive in North and South America and New Zealand. It is a
cold-adapted macrophyte with an optimum growth temperature in the range
of 10–20°C (Ren et al., 1997;
Tobiessen & Snow, 1984). Turions of the
plant germinate in fall, overwinter with little growth, and subsequently
grow fast during early spring after which their growth subsides and they
eventually die and senesce in summer
(Catling & Dobson, 1985;
Tobiessen & Snow, 1984;
Peiyu Zhang, Zhang, et al., 2021).V. spinulosa is endemic to
China, mostly occurring in the middle and lower reaches of the Yangtze
River (B. Wang et al., 2010), where it
often coexists with P. crispus . V. spinulosa is a
warm-adapted species with an optimum temperature for germination at
approximately 20 °C (Wang et al., 2021).P. crispus turions and seedlings of V. spinulosa were
obtained from another nearby lake, Lake Honghu (29°51′N, 113°20′ E).
The herbivore used in this experiment is Radix swinhoei (big-ear
radix), a pulmonated freshwater snail widely distributed throughout
Asia, and found in a diverse set of habitats, including lakes, ponds,
streams, rivers, and rice fields (Ziu et
al., 1979). R. swinhoei is
a generalist grazer which feeds on both periphyton and macrophytes
(K. Y. Li, Liu, Hu, et al., 2009;
Xiong et al., 2010). R. swinhoeisnails were collected in a pond in Huazhong Agricultural University
Fisheries College Base in Wuhan City, Central China (30°29′N; 114°22′
E).