DOI: 10.5061/dryad.t1g1jwt7d
title: Soil fertility as a mediator of interactions between an introduced specialist beetle and a native generalist nematode on an exotic invasive plant and its native congener

description: 1. Invasive plants are often attacked by both introduced specialist and
 native generalist natural enemies in new ranges. Soil fertility can
 potentially alter the interactions of these natural enemies with native
 versus invasive plants in ways that have largely unexplored implications
 for biological invasions and biological control.  2. Common
 garden experiment was conducted to compare the performance of an
 introduced specialist flea beetle, Agasicles hygrophila, and / or
 a native generalist nematode, Meloidogyne incognita, on invasive alligator
 weed, Alternanthera philoxeroides, and its native congener sessile
 joyweed, Alternanthera sessilis, under different levels of soil nitrogen
 (N) and phosphorus (P).  3. At a relatively low or moderate N and
 P level, the flea beetle and the nematodes were not significantly affected
 by each other. Under these conditions, alligator weed responded
 plastically by producing more branches and biomass, as well as longer
 stolons, in response to attack by the flea beetle and / or the nematode,
 compared to sessile joyweed responses to similar levels of damage.
 However, under a relatively high N and P level, nematode infestations
 significantly reduced flea beetle damage on alligator weed, resulting in
 significantly greater above- and below-ground biomass and longer stolons
 than plants without herbivory. In contrast, beetle herbivory significantly
 increased the level of nematode infestations on sessile joyweed, resulting
 in significantly fewer fine and coarse roots, and lower above- and
 below-ground biomass compared to plants without herbivory.  4.
 Synthesis and applications. Our findings illustrate the importance of soil
 fertility in mediating interactions between specialist biocontrol agents
 and native generalists on native versus invasive plants. High phenotypic
 plasticity seems to be an important attribute that contributes to the
 success of invasive plants like alligator weed in relatively nutrient-poor
 environments. However, nutrient-rich environments could potentially confer
 greater growth benefits on invasive plants than on native ones by changing
 herbivore-herbivore interactions on plants differently. There is a great
 need to fully investigate the direct and indirect interactions between
 biocontrol agents and generalists across food webs following classical
 biocontrol releases. Nutrient measurements of both soil and water bodies
 should also be incorporated into all stages of biocontrol programs.
description: We conducted a common-garden experiment to investigate effects of
 the level of soil N and P availability (low, moderate, and high) on the
 performance of the specialist beetle <em>Agasicles
 hygrophila</em> and/or the nematode <em>Meloidogyne
 incognita</em> on the invasive plant Alligator weed,
 <em>Alternanthera philoxeroides</em>, and its native congener
 <em>Alternanthera sessilis</em>. When plants were harvested at
 the end of the experiment, the stem diameter, the stolon length, the
 number of leaves, and the number branches of each plant were measured.
 After the aboveground part of each plant had been cut off, the roots were
 carefully dug up and washed. The number of coarse roots (&gt; 2 mm in
 diameter), fine roots (&lt;2 mm in diameter), and the number of
 nematode root-knots on roots were counted. Finally, both the above-ground
 and below-ground parts of each plant were dried separately and weighed,
 and the total biomass was then calculated.
description: # Soil fertility as a mediator in interactions between an introduced
 specialist beetle and a native generalist nematode on an exotic invasive
 plant and its native congener Paper: Soil fertility as a mediator in
 interactions between an introduced specialist beetle and a native
 generalist nematode on an exotic invasive plant and its native congener ##
 Description of the data This README file describes the data package
 accompanying the above publication. Excel Sheets: 1\. Beetle
 performance-1: includes data on the percentage of damage caused by the
 flea beetle on alligator weed under infestation by nematodes. 2\. Nematode
 performance-1: includes data on the number of root knots on the roots of
 alligator weed under herbivory of the flea beetle. 3\. Beetle
 performance-2: includes data on the percentage of damage caused by the
 flea beetle on sessile joyweed under infestation by nematodes. 4\.
 Nematode performance-2: includes data on the number of root knots on the
 roots of sessile joyweed under herbivory of the flea beetle. 5\. Alligator
 weed: includes data on growth (stem diameter, stolon length, branch
 number, leaf number, the number of coarse roots and fine roots) and
 biomass of alligator weed under herbivory by the flea beetle and nematodes
 and different levels of nutrients. Null: missing value. 6\. Sessile
 joyweed: includes data on growth (stem diameter, stolon length, branch
 number, leaf number, the number of coarse roots and fine roots) and
 biomass of sessile joyweed under herbivory by the flea beetle and the
 nematodes and different levels of nutrients. Null: missing value.