Data from: Strength of enemy release from parasitoids is context-dependent in the invasive African Fig Fly, Zaprionus indianus
Data files
Dec 13, 2024 version files 10.21 KB
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FL_CT_Y.csv
1.02 KB
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README.md
4.05 KB
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ZHcomp.csv
2.63 KB
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ZScomp_2024.csv
1.80 KB
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ZSduration.csv
701 B
Abstract
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.
README: 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
- ZHcomp.csv
- ZScomp_2024.csv
- FL_CT_Y.csv
- ZSduration.csv
Code file list
- competition_analysis.R
- FL_CT.R
- 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.
Methods
Drosophilid larva (Zaprionus indianus, Drosophila simulans, and D. hydei) were reared in the presence or absence of the parasitoid wasp Leptopilina heterotoma 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) Z. indianus alone
2) Lines of Z. indianus collected from different locations
3) Z. indianus competing with D. hydei
4) Z. indianus competing with D. simulans
5) Z. indianus competing with D. simulans 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.