摘要：The freshwater diatom Lindavia intermedia is believed to have been recently introduced to New Zealand lakes. Mucilage (“lake snow”) produced by L. intermedia can block water intakes and/or degrade recreational values. Because nuisance L. intermedia proliferations and lake snow occur rarely in lakes overseas, the species was not initially recognised as invasive and knowledge of its ecology and threat to New Zealand lakes remains sparse. We combined distribution data from several sources with an existing dataset of environmental variables linked to ~ 3800 New Zealand lakes (area > 1 ha) and used a boosted regression trees modelling approach to: (a) describe the environmental niche occupied by L. intermedia; and (b) predict its potential distribution. The effect of human-mediated spread was incorporated using a binary predictor (road200) indicating the presence or absence of vehicle access. “Niche” models were developed using absences (non-detections based on a sensitive molecular method) only in lakes with road access, and “spread” models using all absences and including road200 as a predictor. Lindavia intermedia was observed in 38 lakes, from central North Island to southern South Island, in oligotrophic conditions (total phosphorus < 0.011 mg L-1, total nitrogen < 0.3 mg -1) with cool temperatures (mean annual temperature < 11 °C). All 38 lakes had road access. Likelihood of presence predicted from the combined niche models was lower in North Island lakes (< 1% assessed as vulnerable) than in the South Island (~ 12.5% vulnerable), highlighting that many additional South Island lakes may be environmentally suitable for L. intermedia. However, using the spread models, only 46 lakes were assessed as vulnerable nationwide reflecting a lack of road access to most lakes. Lindavia intermedia was already present in 22 (48%) of the most environmentally suitable lakes with road access. The dataset and models thus implicated humans as important (but not the only) vectors of this diatom within New Zealand, emphasising the critical role of current New Zealand biosecurity policy for reducing the spread of freshwater pests.
关键词：lake snow;nuisance mucilage;oligotrophic lakes;phosphorus;boosted
regression tree models;human vectors;“check;clean;dry”
