DOI: 10.5061/dryad.6hdr7sr8n
title: Data from: Strength of enemy release from parasitoids is context-dependent in the invasive African Fig Fly, Zaprionus indianus

description: Understanding the mechanisms underlying the success of biological
 invasions is essential to employ effective prediction and management
 strategies. The escape from natural enemies in invaded regions (enemy
 release hypothesis) and increased competitive ability are hallmarks of
 invasive species; however, these two processes are rarely studied within
 the same context. Here, we examined the effect of enemy release on the
 competition outcomes of a successful invasive insect pest in North
 America, the African fig fly (Zaprionus indianus). Parasitoid wasps such
 as Leptopilina heterotoma that parasitize drosophilid larvae may seek out
 established species with known host suitability over a novel species, so
 we hypothesized Z. indianus may have low susceptibility to parasitoids,
 giving them a competitive advantage over co-occurring drosophilids. We
 tested this hypothesis by comparing the adult emergence rates from Z.
 indianus larvae reared alone or in competition with Drosophila hydei or D.
 simulans larvae in the presence and absence of parasitoid wasps. These
 interactions might be influenced by larval density, so we tested
 competitive interactions under low and high larval densities. At low
 larval densities, Z. indianus emerged at equal rates to D. hydei but
 outcompeted D. simulans, and these outcomes were not affected by
 parasitoids. However, at high densities, the addition of parasitoids
 shifted competition outcomes in favor of Z. indianus, suggesting enemy
 release provides a competitive advantage under some circumstances. These
 results indicate that the strength of enemy release in Z. indianus is
 widely dependent on contextual factors such as density and competitor
 species. Further investigation of how these results apply to field
 environments could offer insight into how Z. indianus alters ecosystems
 and how productive biological control may limit the spread of Z.
 indianus. 
description: Drosophilid larva (<em>Zaprionus indianus</em>,
 <em>Drosophila simulans</em>, and <em>D.</em>
 <em>hydei</em>) were reared in the presence or absence of the
 parasitoid wasp<em> Leptopilina heterotoma</em> under high or
 low larval densities. We counted the number of adults of each species that
 emerged from each vial to calculate an emergence rate to estimate rates of
 parasitization under different treatments. We conducted five main
 experiments to examine the effects of parasitoids in different
 contexts: 1) <em>Z. indianus</em>
 alone 2) Lines of <em>Z. indianus
 </em>collected from different locations  3)
 <em>Z. indianus </em>competing with <em>D.
 hydei</em> 4) <em>Z. indianus</em>
 competing with <em>D. simulans</em>
 5)<em> Z. indianus </em>competing with <em>D.
 simulans</em> with different exposure times to the
 parasitoid The data were analyzed with generalized
 linear models in R and specific comparisons between experimental groups
 were made using linear contrasts. 
description: # Strength of enemy release from parasitoids is context-dependent in the
 invasive African Fig Fly, *Zaprionus indianus* Invasive species are
 thought to succeed in new environments in part because they are less
 susceptible to diseases and parasites that have co-evolved with local
 hosts, giving them a competitive advantage. We tested this hypothesis by
 competing an invasive fruit fly against established species in the
 presence of parasitoid wasps that lay eggs in fruit fly larvae. We found
 that the invasive species generally experiences less harm from
 parasitoids, but the extent of its advantage depended on the species it
 was competing against and the number of larvae present. # Data file list
 1. ZHcomp.csv 2. ZScomp_2024.csv 3. FL_CT_Y.csv 4. ZSduration.csv # Code
 file list 1. competition_analysis.R 2. FL_CT.R 3. ZS_duration.R #
 Interspecific / intraspecific competition assays These experiments examine
 adult emergence rates of fly larva exposed to parasitoid wasps. Vials
 contained either a single species (*Z. indianus*, intraspecific
 competition), or two species (*Z. indianus* with either *D. simulans* or
 *D. hyde*i, interspecific). Data in these files are shown in Figure 1. #
 Data files: ZHcomp.csv: Data file containing emerged adult fly counts for
 *Z. indianus* and *D. hydei* interspecific/intraspecific competition.
 ZScomp_2024.csv: Data file containing emerged adult fly counts for *Z.
 indianus* and *D. simulans* interspecific/intraspecific competition. #
 Columns * vial: individual vial number * start.num: Starting number of
 total fly larvae * start.date: Start date of experiment * type: Fly
 species present in vial (Two letters = Interspecific vials, One letter =
 Intraspecific vials) * Z = *Z. indianus* * H = *D. hydei* * S = *D.
 simulans* * wasp: Presence or absence of parasitoids * N = Absence of
 parasitoids * Y = Presence of parasitoids * Additional columns are given
 as count dates with the species counted(month/day/year_species): Data in
 the column are the number of that species that emerged. Species key is the
 same as for 'type' above. Missing or nonapplicable data are
 coded as 'NA' # Code The code to perform these analyses is found
 in competition_analysis.R # Host-switching assay This experiment compares
 adult emergence rates of *Z. indianus* and *D. simulans* exposed to
 parasitoids for different amounts of time. These data are shown in Figure
 3. # Data file: ZSduration.csv: Data file containing emerged adult fly
 counts for *Z. indianus* and *D. simulans* host-switching assay # Columns
 * vial: individual vial * start.num: starting number of total larvae *
 start.date (month/day/year): Date of experiment start * time: How long fly
 larvae were exposed to parasitoids (in hours) * wasp: Presence or absence
 of parasitoids * Y: Presence of wasps * N: Absence of wasps * Additional
 columns are given as count dates with the species
 counted(month/day/year_species): Data in the column are the number of that
 species that emerged. Species key is: * Z = *Z. indianus* * S = *D.
 simulans* # Code The code to perform these analyses is found in
 ZSduration.R # FL/CT assay This experiment compares adult emergence rates
 of *Z. indianus* lines collected from Florida (FL) and Connecticut (CT)
 with the presence of parasitoid wasps. These data are shown in Figure 2. #
 Data files: FL_CT_Y.csv: Data file containing emerged adult fly counts of
 FL/CT lines with parasitoids # Columns * vial: individual vial * line:
 line of flies present in vial. There are four unique lines for FL and four
 for CT * start.date: Start date of experiment * start.num: Starting number
 of total fly larvae * Count dates (month/day/year): Date of counting. Data
 are reported as the number of adult flies that emerged from the vial. #
 Code The code to perform these analyses can be found in FL_CT.R #
 Code/Software R Code to produce analysis, figures, and tables from the
 manuscript can be found in the R scripts included in this repository and
 are explained in the descriptions above.