Are botanical gardens a risk for zooplankton invasions?

Abstract

A number of zooplankton invasions have been linked with the movement of plants to botanical and other public gardens. Although most of these records are historical, several recent examples indicate that aquatic fauna may still be transported by plant movements among gardens, or that there are unrecognised long-standing established populations in garden ponds around the world. We sampled 40 ponds from 10 gardens, in the United Kingdom and United States, to determine whether there is a high prevalence of non-indigenous zooplankton in garden ponds that could spread more widely if provided opportunity. No non-indigenous species were recorded from any of the gardens visited. We conclude that most well-established gardens do not pose a major threat for zooplankton invasions, mainly due to the destruction of ponds and associated populations through time, which apparently occurs commonly. In addition, ponds are regularly cleaned, insecticides are used on plants that may enter the water, and small fish are frequently added to conservatory ponds, further reducing the probability of zooplankton survival. Extirpation of populations may be occurring at a greater rate than re-introduction, due to greater restrictions on movement of plants, while the increasing focus on ex-situ conservation and science rather than aesthetics by botanical gardens means that fewer aquatic plants are being moved.