DOI: 10.5061/dryad.qg7p3
title: Data from: Test of biotic and abiotic correlates of latitudinal variation in defences in the perennial herb Ruellia nudiflora

description: 1. Geographic variation in abiotic factors and species interactions is
 widespread and is hypothesized to generate concomitant patterns of species
 trait variation. For example, higher rates of herbivory at lower latitudes
 are thought to select for increased plant defences, although latitudinal
 variation in defences may also be influenced directly by abiotic factors
 and indirectly by predators and parasitoids reducing herbivore pressure.
 2. We measured defences of the herb Ruellia nudiflora among 30 populations
 spanning a latitudinal gradient from northern Yucatan to southern Belize
 that vary substantially in leaf herbivory (four-fold), seed herbivory
 (25-fold), and seed herbivore parasitism (14-fold). These surveyed
 populations span one-third of the species’ latitudinal distribution (5° of
 latitude), the entire precipitation gradient of its distribution, and
 one-third of the temperature gradient of its distribution. Our prior work
 showed that leaf herbivory decreased with latitude and that seed herbivory
 increased with latitude. Here, we measured leaf trichome density and leaf
 and seed phenolics and tested whether latitudinal variation in climate,
 herbivory, and parasitism explained latitudinal variation in these
 defensive traits. 3. Patterns of variation in leaf trichomes fully
 supported predictions, with trichome density increasing with a parallel
 increase in herbivory towards lower latitudes. While seed phenolics were
 positively associated with herbivory, and seed herbivory tended to
 increase with latitude, the predicted (positive) association between
 latitude and defence was not detectable. There was no detectable
 association between parasitoids and seed defences. In addition, the
 association between leaf herbivory and phenolics was weak, and leaf
 phenolics were not associated with latitude. Importantly, variation in the
 abiotic environment was associated with plant defence, indicating that
 abiotic factors can play a major role in shaping plant defences,
 independently of herbivory. 4. Synthesis: Latitudinal variation in abiotic
 factors may drive concomitant patterns of variation in plant defences,
 independently of herbivory. Collectively, these findings highlight the
 need for assessing geographic variation in plant defences from a
 multi-factorial perspective, testing for the simultaneous influence of
 biotic and abiotic factors.
description: latitude, herbivore
 attack, plant defenses, and climatic dataRuellia nudiflora
 population-level values for defenses, herbivore attack, and parasitoid
 attack. Variables are ordered and labeled in the following way:
 "population" = plant population name; "latitude" =
 decimal degrees latitude for each population ; "pctemperature" =
 z-score values from first principal component of PCA analysis of
 temperature-related variables (from WorldClim);
 "pcprecipitation" = z-score values from first principal
 component of PCA analysis of precipitation-related variables (from
 WorldClim); "seedphenolics" = concentration of phenolic
 compounds in seeds; "leafphenolics" = concentration of phenolic
 compounds in leaves; "fruitattack" = mean proportion of attacked
 fruits by seed herbivore; "parasitoidattack" = mean proportion
 of seed herbivores parasitized; "leafdamage" = mean leaf damage
 score; "trichomedensity" = mean leaf trichome
 density.latitudinalvariation_Abdalaetal.csv