The Impact of Plant Enemies Shows a Phylogenetic Signal

<div><p>The host ranges of plant pathogens and herbivores are phylogenetically constrained, so that closely related plant species are more likely to share pests and pathogens. Here we conducted a reanalysis of data from published experimental studies to test whether the severity of host-enemy interactions follows a similar phylogenetic signal. The impact of herbivores and pathogens on their host plants declined steadily with phylogenetic distance from the most severely affected focal hosts. The steepness of this phylogenetic signal was similar to that previously measured for binary-response host ranges. Enemy behavior and development showed similar, but weaker phylogenetic signal, with oviposition and growth rates declining with evolutionary distance from optimal hosts. Phylogenetic distance is an informative surrogate for estimating the likely impacts of a pest or pathogen on potential plant hosts, and may be particularly useful in early assessing risk from emergent plant pests, where critical decisions must be made with incomplete host records.</p></div

Observed phylogenetic signal in severity of impact of plant-enemy interactions.

<p>Regressions are based on weighted mean regression coefficients of relative impact on the log of the phylogenetic distance between hosts in meta-analysis of published studies. Regression coefficients are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.t001" target="_blank">Table 1</a>. Thick lines are based on mean intercept and slope, and the thin lines are 95% confidence intervals. For comparison in panels A and B, the dashed black lines show the expected probability that two hosts at that phylogenetic distance would share a particular enemy based on re-analysis of data in Gilbert et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.ref018" target="_blank">18</a>], using the present phylogenetic tree. In panel C, Pathogen development has no confidence intervals because it was derived from only one study unit (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.t001" target="_blank">Table 1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.s001" target="_blank">S1 Fig</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.s003" target="_blank">S1 Table</a>).</p

Weighted means of intercept (<i>b</i>_•0) and slope (<i>b</i>_•1) from the study-unit regressions described in S2 Table, for each of five types of interaction type and measured impact.

<p>^aCoefficients are for the model <i>RI</i> = <i>b</i>_•0 + <i>b</i>_•1log₁₀(<i>PD</i> + 1), where <i>PD</i> is the phylogenetic distance in Ma from the most strongly affected host.</p><p>^bStandard errors for the weighted means are not available for disease—enemy development category because there was only one study unit (N), but were significant in the original study.</p><p>^cThe 95% confidence intervals are presented for the weighted mean slopes.</p><p>Weighted means of intercept (<i>b</i>_•0) and slope (<i>b</i>_•1) from the study-unit regressions described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123758#pone.0123758.s004" target="_blank">S2 Table</a>, for each of five types of interaction type and measured impact.</p

ReadMe_ParkerEtAl_Data2015Nature

Metadata for four sets of data used in Parker et al. 2015. Phylogenetic structure drives disease pressure in communities. Nature. In press

Meadow_ExperimentalPlant_visualdisease

Estimates of percent of leaf area lost to disease for experimentally introduced plant species in each of 10 plots in grassland on the University of California Santa Cruz campus, Santa Cruz, CA USA (36°59'18.09"N, 122° 3'31.29"W). Data were collected in April 2012. (Used for Fig 3) plot: Plot number (1 to 10) for estimates of cover and disease genus: Plant genus species: plant species visualdisease: Percent of foliar tissue lost to disease (necrosis and chlorosis

Meadow_traitstable

Attributes of the wild and experimentally introduced plant species from the study in grassland on the University of California Santa Cruz campus, Santa Cruz, CA USA (36°59'18.09"N, 122° 3'31.29"W) in 2011 and 2012. Used for Fig 2 and Fig 3 source: plant species found wild or experimentally introduced in grassland community origin: plant species native to Santa Cruz region or nonnative genus: genus of plant species: species of plant name: aggregate genus species name of plant code: 6-letter mnemonic code for plant species family: family of plant species phyloname: phylomatic-style family/genus/name of plant specie

RSAmeadow phylogenetic distance matrix

Phylogenetic distances (in My of independent evolution) between all pairs of wild and experimentally introduced plant species. (Used for Fig 2 and Fig 3