Models of lake invasibility by Bythotrephes longimanus, a non-indigenous zooplankton

Abstract

We built a family of hierarchical risk models for the spread of invasions by the spiny waterflea (Bythotrephes longimanus) in lakes in Ontario, Canada. Knowledge of covariates determining lake invasibility and ability to predict risk of future invasions may help to develop management policy and slow the invasions in the future. The models are based on two component submodels. The first component was a stochastic gravity submodel for the propagule pressure between lakes via recreational boaters. The second component was a submodel for establishment risk, given that the invader has already been introduced to a lake. This component was a logistic regression model, incorporating up to 17 measured covariates that describe the physical and chemical condition of the lake. Variants of the risk model, each incorporating different subsets of the covariates, were calibrated using presence/absence data from a 300-lake survey conducted in 2005-2006 by the Canadian Aquatic Invasive Species Network (CAISN). The predictive capacity of the best model was high, giving AUC values close to 0.94. Of the model covariates considered, the most important predictors of existing invasions were propagule pressure and lake pH, and, to lesser extents, phosphorus (P) and lake elevation. Our fitting of the propagule pressure submodel demonstrated a significant Allee effect for Bythotrephes. Our development of the establishment risk predictor showed that it is essential to account for temporal variability in lake physico-chemistry. We demonstrated that invasions of lake networks by the spiny waterflea follow highly predictable patterns which can be understood with a properly calibrated, hierarchical risk model.

The spread, establishment and impacts of the spiny water flea, Bythotrephes longimanus, in temperate North America: a synopsis of the special issue

“…Research in this collection dramatically enriches this understanding. In independent modeling efforts, Potapov et al (2011);, and Muirhead and MacIsaac (2011) all demonstrate the central role of propagule pressure in explaining the current pattern of Bythotrephes presence on the Canadian Shield. Further prove that the component of propagule pressure contributed by stream connections in this landscape is so low it can be practically ignored, while it certainly can be high in much larger rivers (e.g.…”

“…Such comparisons are rarely possible, but are very useful for consideration of the consequences of subtle differences in model structure (i.e., analysis of model uncertainty), for identification of the potential importance of different underlying invasion processes, and for testing alternative hypotheses when multiple processes or model structures yield similar fits to the data. We assemble that research here, with four papers focused on modeling the growth and spread of the invader on the south- Muirhead and MacIsaac 2011;Potapov et al 2011;Wang and Jackson 2011). Combined, this work provides insight into where potential colonists are going, how quickly they are moving, and which sites will allow them to survive and prosper, information crucial to understanding and managing secondary spread.…”

“…Bythotrephes incidence is increasing in lakes on the south-central Canadian Shield (Weisz and Yan 2010), and the modeling efforts of Potapov et al (2011), Muirhead and MacIsaac (2011) and in this collection were built on that growing data set. However, Kerfoot et al (2011) add their own survey data to other recent American survey data (e.g.…”

“…1e). Wang andJackson (2011) andPotapov et al (2011) demonstrate that habitat information can improve predictions of invader prevalence, with consideration, respectively, of sport fish composition and habitat acidity, while Jokela et al (2011) prove that interactions with numerous native macro-invertebrate predators will not slow the spread of the invader. 3.…”

Invasive species triggers a massive loss of ecosystem services through a trophic cascade

“…Despite this planktivory and large documented ecological impacts on zooplankton communities (19,20), Bythotrephes has not been found to have cascading effects on lake primary production and water clarity (21). The lack of cascading effects of Bythotrephes invasion is perhaps because the productive lakes most vulnerable to impaired water clarity are thought to be relatively unsuitable for Bythotrephes establishment (22).…”