Figure 1.

Expected phylogenetic patterns in host ranges of plant pests and pathogens. Phylogenetic signal in the host range of pests is a measure of the probability that two hosts (two branch tips on the phylogenetic tree) would share a particular pest, given the phylogenetic distance between the hosts. (A) The host ranges of most pests and pathogens are expected to show a phylogenetic signal, with a tendency to be clustered within an evolutionary clade (filled circles). The probability of sharing a pest (prob(S)) decreases quickly with increasing phylogenetic distance between the hosts. (B) Phylogenetically dispersed host ranges (open circles) should be less common, because phylogenetically dispersed hosts should present diverse defensive traits that would be challenging for a single pest to overcome. (C) Pests with broad host ranges are likely to show a phylogenetic signal (open diamonds), where expanded host range comes with the ability to attack several hosts within multiple clades. Phylogenetic distance is measured as time of independent evolution between two taxa, represented here by the thick solid line (short phylogenetic distance) and thick dashed line (long distance). Time of independent evolution is twice the age to most recent common ancestor (vertical dotted lines).