Miscellaneous Papers by Marion Wittmann
Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species relies up... more Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species relies upon the ability to predict dispersal pathways and receiving habitats with the greatest risk of establishment. To examine mechanisms affecting species establishment within a large lake, we combined observations of recreational boater movements with empirical measurements of habitat suitability represented by nearshore wave energy to assess the relative risk of Eurasian watermilfoil (Myriophyllum spicatum) establishment. The model was evaluated using information from a 17 year (1995–2012) sequence of M. spicatum presence and absence monitoring. M. spicatum presence was not specifically correlated with recreational boater movements; however its establishment appears to be limited by wave action in Lake Tahoe. Of the sites in the “High” establishment risk category (n = 37), 54% had current or historical infestations, which included 8 of the 10 sites with the highest relative risk. Of the 11 sites in the “Medium” establishment risk category, 5 had current or historical M. spicatum populations. Most (76%) of the sites in the “Low” establishment risk category were observed in locations with higher wave action. Four sites that received zero boater visits from infested locations were occupied by M. spicatum. This suggests that the boater survey either represents incomplete coverage of boater movement, or other processes, such as the movement of propagules by surface currents or introductions from external sources are important to the establishment of this species. This study showed the combination of habitat specific and dispersal data in a relative risk framework can potentially reduce uncertainty in estimates of invasion risk.
Papers by Marion Wittmann
Ecology and Evolution, 2014
Due to socioeconomic differences, the accuracy and extent of reporting on the occurrence of nativ... more Due to socioeconomic differences, the accuracy and extent of reporting on the occurrence of native species differs among countries, which can impact the performance of species distribution models. We assessed the importance of geographical biases in occurrence data on model performance using Hydrilla verticillata as a case study. We used Maxent to predict potential North American distribution of the aquatic invasive macrophyte based upon training data from its native range. We produced a model using all available native range occurrence data, then explored the change in model performance produced by omitting subsets of training data based on political boundaries. We also compared those results with models trained on data from which a random sample of occurrence data was omitted from across the native range. Although most models accurately predicted the occurrence of H. verticillata in North America (AUC > 0.7600), data omissions influenced model predictions. Omitting data based on political boundaries resulted in larger shifts in model accuracy than omitting randomly selected occurrence data. For well-documented species like H. verticillata, missing records from single countries or ecoregions may minimally influence model predictions, but for species with fewer documented occurrences or poorly understood ranges, geographic biases could misguide predictions. Regardless of focal species, we recommend that future species distribution modeling efforts begin with a reflection on potential spatial biases of available occurrence data. Improved biodiversity surveillance and reporting will provide benefit not only in invaded ranges but also within under-reported and unexplored native ranges.
Environmental science & technology, Jan 18, 2014
Recently, authors have theorized that invasive species prevention is more cost-effective than con... more Recently, authors have theorized that invasive species prevention is more cost-effective than control in protecting ecosystem services. However, quantification of the effectiveness of prevention is rare because experiments at field scales are expensive or infeasible. We therefore used structured expert judgment to quantify the efficacy of 17 proposed strategies to prevent Asian carp invasion of the Laurentian Great Lakes via the hydrologic connection between the Mississippi and Great Lakes watersheds. Performance-weighted expert estimates indicated that hydrologic separation would prevent 99% (95,100; median, 5th and 95th percentiles) of Asian carp access, while electric and acoustic-bubble-strobe barriers would prevent 92% (85,95) and 92% (75,95), respectively. For all other strategies, estimated effectiveness was lower, with greater uncertainty. When potential invasions by other taxa are considered, the effectiveness of hydrologic separation increases relative to strategies that are effective primarily for fishes. These results could help guide invasive species management in many waterways globally.
... a , Michael Rosen b , Marion Wittmann c , Joe Sullivan a & Erik Orsak d pages... more ... a , Michael Rosen b , Marion Wittmann c , Joe Sullivan a & Erik Orsak d pages 293-305. ... 200235. Vadeboncoeur, Y, Vander Zanden, MJ and Lodge, D M. 2002. Putting the lake back together: Reintegrating benthic pathways into lake food web models.. Bioscience , 52: 4454. ...
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Miscellaneous Papers by Marion Wittmann
Papers by Marion Wittmann