Patterns of density dependence in growth, reproduction and survival in the invasive freshwater snail Pomacea canaliculata in Japanese rice fields

Abstract

Summary Patterns of density dependence in growth, reproduction and survival are important for predicting the population dynamics of a species. The patterns may change with environmental factors, such as the harshness of winter, but very little is known about such patterns and their mechanisms in unmanipulated natural populations of invasive animal species. We studied the extent of density dependence in the growth, reproduction and survival of an invasive freshwater snail, Pomacea canaliculata, in rice fields in Nara (cold district) and Kumamoto (warm district), Japan, over 2‐ and 1‐year periods, respectively. In both areas, growth was negatively density dependent within the same generation, and the density of snails in the parental generation negatively affected the growth of offspring. The number of eggs per unit area was independent of adult density, suggesting eggs per adult female were few at high densities. Survival over the cold winter of 2005–2006 was independent of density in Nara. However, survival over the warm winter of 2006–2007 in both Nara and Kumamoto was negatively density dependent. Irrespective of the various negative density‐dependent patterns, population density tended to show positive correlations with the density of the previous generation. This appears to reflect the substantial capacity of this snail to resist extremely low densities due to the various negative density‐dependent patterns rather than indicating susceptibility to extinction at low densities.

Insights from an Integrated View of the Biology of Apple Snails (Caenogastropoda: Ampullariidae)

“…Although snails show dif-ferences in size at hatching, maturity and maximum size, often in response to different densities (Tanaka et al, 1999;Yoshida et al, 2009Yoshida et al, , 2013, such differences disappeared in snails reared under homogeneous laboratory conditions, indicating a strong environmental influence; slightly higher mortality, growth and oviposition rates in laboratory snails from unstable and unproductive habitats were attributable to genetic differences among source populations . The high environmental tolerance of P. canaliculata and its successful establishment in new environments may be associated with this high level of ecophenotypic plasticity .…”

“…Population density and per capita food availability are probably important (Tanaka et al, 1999;Yoshida et al, 2009Yoshida et al, , 2013. For P. canaliculata, the relationship of food availability with size, age at maturity and reproductive performance differ between males and females Estoy et al, 2002a, b;Tamburi & Martín, 2009a.…”

A temperature-dependent physiologically based model for the invasive apple snail Pomacea canaliculata

“…The parameter φ is taken equal to 10 individuals/m 2 for all the stages to account for the reported effect of high density on the mortality (Tanaka et al 1999;Yoshida et al 2013).…”

“…However, because no data are available for the biotic variables affecting population abundance, our analysis is restricted to the consideration of the influence of meteorological variables only. Then, when data on resources, competitors and predators are not known, we retain the value φ = 10 in agreement with Tanaka et al (1999) and Yoshida et al (2013).…”

Overview of Inland Water Habitats

“…Examples include apple snails (Pomacea) in Japan (Yoshida et al, 2013) and Louisiana crayfish (Procambarus clarkii) in Hawaii (Larned et al, 2003). Examples include apple snails (Pomacea) in Japan (Yoshida et al, 2013) and Louisiana crayfish (Procambarus clarkii) in Hawaii (Larned et al, 2003).…”