Lake construction has facilitated calanoid copepod invasions in New Zealand

Aim We tested the hypothesis that construction of lakes and ponds has facilitated both inter‐ and intracontinental invasions of calanoid copepod species. Location North Island, New Zealand. Methods We sampled both natural and constructed lakes, ponds and reservoirs for calanoid copepods in the North Island, New Zealand. Species records were supplemented by examining historically collected samples and literature review. Distributions of non‐indigenous calanoid copepod species were compared between constructed and natural waters. Species distributions of native species were compared with the basement terranes (microplates) of the North Island to determine if they possess ‘natural ranges’, and to assess whether construction of new water bodies had altered these distributions. Results Ten calanoid copepod species have been recorded. At least four, and possibly five, of these species are non‐indigenous and were restricted to constructed water bodies. Occurrences in constructed water bodies were not restricted to dammed valleys, but also included ponds constructed on farms, ornamental ponds, disused quarries and retired mines. Four Boeckella species had distributions in natural waters closely related to the North Island basement terranes, and therefore possess ‘natural ranges’ on the island. One species, Boeckella propinqua, was found in natural lakes over a small geographical range only, but has spread with construction of new water bodies to now be widely distributed over the island. Main conclusions Construction of lakes and ponds has facilitated the invasion of calanoid copepod species at both inter‐ and intracontinental scales. Our findings suggest that resident native calanoid copepod species may reduce the risk of invasion to natural water bodies, as similar‐sized species are commonly unable to co‐occur. Spread of the non‐indigenous representatives from constructed into natural waters is inevitable, with established populations providing local propagule supplies for regular introductions.