1. Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John’s, Canada
2. Department of Ecology, Evolution and Behavior, A. Silberman Institute of Life Sciences, Faculty of Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
3. Department of Mathematics, University of Manitoba, Winnipeg, Manitoba, Canada
4. Biology Department and Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John’s, Canada