Figure 2.
Variation in spread metric values and indices of collection effort as a function of the year of first observation. (a) Colonization rate, c, (b) maximum spread (in km yr−1), (c) fitted search effort (constant b), (d) sampling effort (or number of publications in which observations of the species are mentioned, per year of observation). Only points for taxa where both the maximum rate of spread and colonization rate were defined by significant regression relationships are shown (species group D).