Invasive traits of veronicellid slugs in the Hawaiian Islands and temperature response suggesting possible range shifts under a changing climate.
Understanding life history traits is important for assessing potential invasiveness, particularly in the context of the future spread of invasive species under climate change. A number of species of Veronicellidae have been introduced beyond their native ranges and have become invasive. Two of these species, Veronicella cubensis and Laevicaulis alte, are widespread in Hawaii, yet little is known of their life histories. This study of growth and reproduction and their relation to temperature in these two species was undertaken using laboratory stocks derived from individuals collected in Hawaii. More data were collected for V. cubensis than for L. alte because of difficulty maintaining the latter in the lab. Veronicella cubensis grew faster at 22°C than at 27°C. At 22°C, the mean age at which V. cubensis first mated was 203 d, and the mean age when eggs were first laid was 226 d. Mating in V. cubensis lasted more than a day, and it took up to 4 d to lay an egg mass. Mating took less than a day in L. alte. No self-fertilization was recorded in V. cubensis, but a single L. alte individual maintained alone from hatching laid fertilized eggs. Sperm storage after a single mating in V. cubensis was estimated to last up to 6 months. In both species the time for eggs to hatch was shorter at 27°C than at 22°C. Hatchability was between 74 and 93%. Veronicella cubensis lived for at least 2 years and was estimated to produce at least 400 eggs over its life. Climate warming will probably lead to expansion of the ranges of V. cubensis and L. alte to higher elevations in Hawaii and elsewhere. Growth and reproduction will also be affected by a warming climate and therefore impact the success of these invasive species.