1 Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal. ssmunzi@fc.ul.pt.
2 Departamento de Ecología, Universidad Autónoma de Madrid, 2, Darwin Street, 28049, Madrid, Spain.
3 Department of Mathematics and Physics, Catholic University of Brescia, Via dei Musei 41, Brescia, Italy.