Survivorship of geographic Pomacea canaliculata populations in responses to cold acclimation

1. Pomacea canaliculata, a freshwater snail from South America, has
rapidly established natural populations from south to north subtropical
region in China since its original introductions in the 1980s. Low
temperature in winter is a limiting factor in the geographic expansion and
successfully establishment for apple snail populations. There have been
some studies on population-level of low temperature tolerance for P.
canaliculata, yet little is quantified about its life-history traits in
responses to cold temperatures. Whether these responses vary with the
acclimation location is also unclear. We investigated the survivorship and
longevity of P. canaliculata in responses to cold temperatures and examine
whether these responses vary with the location and snail size. We
hypothesized that survival of the snails depends on their shell height and
the level of low temperature, and P. canaliculata population from the mid-
subtropical zone may exhibit the highest viability over the cold thermal
range. 2. We sampled P. canaliculata populations from five latitude and
longitude ranges of subtropical China: Guangzhou population in
southernmost (SM-GZ), three populations of Yingtan (MR-YT), Ningbo
(MR-NB), Ya’an (MR-YA) in mid-range, and Huanggang population in
northernmost (NM-HG) subtropical zone. For each P. canaliculata
population, survival and longevity at six cold acclimation temperature
levels (12 °C, 9 °C, 6 °C, 3 °C, 0 °C, and -3 °C ) were quantified, and
the effects of location and shell height were examined. 3. The MR-YA
population from mid- subtropical zone of China exhibited the highest
survival rate and prolonged survival time regardless of the temperature
acclimation treatments, whereas the SM-GZ population from southern sub-
tropical was the most sensitive to cold temperatures, particular
temperatures below 9 °C. No individuals of the SM-GZ population could
survive after stressed for 30d (3℃), 5 d (0℃) and 2 d (-3℃), respectively.
For each experimental P. canaliculata population held at 3 °C, 0 °C and -3
°C, individuals with intermediate shell height of 15.0–25.0 mm had
significantly higher survivals. 4. The results highlight a request of a
more thorough investigation on acclimation responses in each of the life
table demographic parameters for P. canaliculata, and pose the question of
whether natural selection or some genetic changes may have facilitated
adaptation in invasive locations.