|Non-indigenous species have become a global issue of increasing importance in recent years, with many causing significant environmental and economic damage. Identifying locations vulnerable to invasion allows for focus of management efforts towards prevention of invasions at those locations. In order to determine whether constructed water bodies, such as reservoirs, ornamental lakes or retired mines, are more easily invaded environments than natural water bodies, owing to decreased biotic resistance, the distributions of native and non-indigenous freshwater calanoid copepod species in the North Island were examined. Calanoid copepods in ports and other coastal environments were also examined, in order to determine whether ports are more frequently invaded owing to increased propagule supplies from visiting ships and other sources.
The distributions of the native freshwater calanoid copepod species Boeckella hamata, B. propinqua, B. delicata and B. tanea are confined in the North Island of New Zealand to specific technostratigraphic terranes when natural waters only are examined, and as such each species can be considered to have a native range. The recently colonised calanoid copepod species Boeckella minuta (6 locations), Skistodiaptomus pallidus (3 locations) and Sinodiaptomus valkanovi (2 locations) are to date confined to constructed water bodies. Boeckella symmetrica (2 locations) may be confined to constructed water bodies, but the status of one location is unclear. Boeckella triarticulata, a species common in the South Island, is known only from a single farm dam in the North Island. The native species Boeckella hamata, B. propinqua and B. delicata were found to occur in constructed waters, but only B.
propinqua was found in constructed water bodies outside their natural ranges (9 locations). Calamoecia lucasi is found in lakes throughout most of the North Island, and is not confined to any one terrane. My results indicate that constructed water bodies are more easily invaded by non-indigenous species than natural water bodies, represents a potential pathway for future invaders to establish, and provides locations for species to spread.
In order to determine whether recently established freshwater calanoid copepod species have the potential to spread from their present habitats into other water bodies, the prosomal lengths of non-indigenous calanoid copepod species were measured and compared with those for native species. The results suggest that dietary overlap should prevent the non-indigenous species present to date from spreading into any water bodies with established Boeckella populations, although Sinodiaptomus valkanovi and Boeckella triarticulata could potentially spread to lakes containing only Calamoecia lucasi. Data on the co-occurrences of native freshwater calanoid copepod species support the theory of dietary exclusion, as Boeckella species have not been found to coexist.
In order to test whether New Zealand marine environments have been invaded by non-indigenous calanoid copepods, and whether ports have been more regularly invaded than non-port areas, calanoid copepods were sampled from various coastal locations around the North Island. With the possible exception of Sulcanus conflictus, no non-indigenous species were found, indicating that non-indigenous marine calanoid copepod species are not establishing in New Zealand despite a history of invasion elsewhere.