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Raw data on acceptance and emergence in intrinsic competition experiments, and guarding behavior in extrinsic competition: Trissolcus cultratus and Trissolcus japonicus

Citation

Gariepy, Tara (2022), Raw data on acceptance and emergence in intrinsic competition experiments, and guarding behavior in extrinsic competition: Trissolcus cultratus and Trissolcus japonicus, Dryad, Dataset, https://doi.org/10.5061/dryad.gmsbcc2p4

Abstract

Understanding competition between scelionid parasitoids that exploit the same host may provide insight into strategies that allow co-existence on a shared resource. Competition studies typically focus on interactions between native and exotic parasitoids that do not share an evolutionary history; however, co-evolved parasitoids may be more likely to demonstrate strategies to avoid or exploit a shared resource. We examined intrinsic and extrinsic competition between Asian Trissolcus japonicus Ashmead and T. cultratus Mayr (Hymenoptera: Scelionidae) associated with Halyomorpha halys Stål (Hemiptera: Pentatomidae) that share an evolutionary history. Interspecific interactions were assessed by providing parasitized egg masses to each species at various intervals post-parasitism, and measuring host acceptance, developmental suitability, and guarding behaviour. Trissolcus japonicus showed high acceptance of parasitized hosts up to 72h following oviposition by T. cultratus, despite a very poor developmental outcome. In contrast, T. cultratus generally avoided ovipositing in H. halys eggs containing T. japonicus early-instar larvae, but did not avoid parasitizing H. halys that contained eggs and third instar larvae. The adaptive value of this behaviour was supported by developmental outcome: T. cultratus outcompeted T. japonicus eggs but not early-instar larvae, and a trophic shift occurred wherein T. cultratus developed as a facultative hyperparasitoid on third instar T. japonicus larvae. Trissolcus japonicus guarded egg masses 8 – 12x longer and displayed more aggressive interactions than T. cultratus, suggesting T. japonicus is the superior extrinsic competitor. Development as a facultative hyperparasitoid provided a competitive niche for Asian T. cultratus and confirms its instrinsic competitive superiority. This also occurs in a biologically-distinct European population of T. cultratus, suggesting that facultative hyperparasitism as a competitive strategy is retained in geographically-separated populations that have not co-evolved with H. halys or T. japonicus.

Methods

Extrinsic competition (Associated with file 05. Extrinsic Competition Behavior Data.csv)

Individual, 4 days old females of T. japonicus (TJ) and T. cultratus (TC) were provided individually with single H. halys egg masses of regular size (28 eggs) in small plastic dishes (5 x 1 cm). Females were observed under the stereomicroscope until they parasitized all eggs and initiated brood guarding behaviour. Single females of the second species were then added to each dish through a small resealable hole on the side. Interactions of competing females were filmed for 30 min with a portable digital microscope and analysed with Observer XT software (Noldus Information Technology B.V., The Netherlands). Replicates in which wasps showed no interest in the egg mass (no searching behaviour, no interaction with the competitor) were excluded from the analysis.For the guarding wasps (1st) the following parameters were recorded: guarding the egg mass, patrolling on the leaf, chasing competing wasp, fighting (direct physical contact with competitor) and walking off the leaf. For the competitor (2nd species) added to the petri dish containing a guarding wasp, seven behavioural categories were defined: walking off the leaf, walking on the leaf, drumming on the egg mass, ovipositing, marking parasitized eggs, chasing guarding wasp and fighting. For both wasp species the last two categories were considered as aggressive behaviour towards the competitor. When the competing wasp was able to complete oviposition (indicated by marking) on at least one of the guarded eggs, extrinsic competition was considered successful.

The following abbreviations are used in the table:

Observations.    Replicates

W_Guard.          Wasp species guarding

W_Compet        Wasp species competing

Tguard               Time spent guarding by the guarding wasp

Tempty_GW       Time spent in the empty space by the guarding wasp

Tleaf_GW          Time spent on the leaf by the guarding wasp

Tfight_GW         Time spent fighting by the guarding wasp

Tempty_CW.      Time spent in the empty space by the competing wasp

Tleaf_CW           Time spent on the leaf by the competing wasp

Tdrum                Time spent drumming (logically by the competing wasp)

TOvip                  Time spent ovipositing (logically by the competing wasp)

TMark                 Time spent marking (logically by the competing wasp)

Tfight_CW          Time spent competing by the competing wasp

Nguard                Number of times guarding the egg mass within 30 min (by the guarding wasp)

Nempty_GW   Number of times spent in the empty space (by the guarding wasp)

Nleaf_GW     Number of times spent on the leaf within 30 min ( by the guarding wasp)

Nchase_GW   Number of times chasing the competitor within 30min (by the guarding wasp)

Nfight_GW     Number of times fighting with competing wasp within 30min (by the guarding wasp )

Nempty_CW   Number of times spent in the empty space within 30min (by the competing wasp)

Nleaf_CW        Number of times on the leaf within 30 min (by the competing wasp)

Nchase_CW     Number of times chasing the guarding wasp within 30min (by the competing wasp)

Ndrum              Number of times drumming on the egg mass within 30min (by the competing wasp)

Novip               Number of times ovipositing within 30min (by the competing wasp)

Nmark              Number of times marking within 30min (by the competing wasp)

Nfight_CW      Number of times fighting with guarding wasp within 30 min( by the competing wasp)

Duration           Duration of the observation (30 minutes)

Duration of guarding behaviour (Associated with file 01. Trissolcus japonicus Raw data host guarding experiment.csv and 02. Trissolcus cultratus Raw data host guarding experiment.csv)

Females of each parasitoid species were exposed individually to fresh H. halys egg masses (28 eggs) in small Petri-dishes (5cm diameter) with a 5mm hole in the lid, which was closed with a piece of foam. Females were observed until they had parasitized all eggs and started to guard the parasitized egg mass. Once guarding was observed, each plastic dish containing a wasp was placed individually in a larger 1.2L plastic container, the foam stopper on the petri dish was removed, and the larger container was sealed to prevent escape. Wasps were monitored every hour to determine whether they continued to guard the egg mass (Guarding, G) or had left the egg mass and had entered the larger container, indicating that they were no longer guarding the egg mass (Off the egg mass, O).

Acceptance of and emergence from multiparasitised host egg masses (Intrinsic competition) (Associated with file 03. acceptance and multiparasitism behavior.csv and 04. Emergence from multiparasitized eggs.csv)

Assays were carried out in small plastic dishes (5 x 1 cm), and observations were made using a stereomicroscope, following the experimental design of Konopka et al. (2017). Randomly selected T. japonicus females (2-7 days old, mated, naïve) were offered fresh (< 24 h) H. halys egg masses (12 eggs/ mass) and observed until all eggs were parasitized, indicated by the characteristic marking behaviour. Trissolcus cultratus females (2-7 days old, mated, naïve) were provided egg masses previously parasitized by T. japonicus 0, 24, 48, 96, and 120h earlier (note that 0h refers to an egg mass that was parasitized by the first species, and then immediately offered to the second species), and observed until they parasitized the entire egg mass or until females left the egg mass for >10 min. This approach ensured that parasitoids were provided parasitized hosts at different stages of embryonic development [i.e., parasitoid egg (0h), larvae (24 – 72h), pre-pupae (96h) and pupae (120h); as per Volkoff & Colazza, 1992; Adidharma & Ciptadi, 2012; Konopka et al., 2020]. As controls, fresh H. halys egg masses (12 eggs/mass) were offered to T. cultratus and T. japonicus females separately to estimate emergence without competition. The number of eggs attempted (drilled) and parasitized (marked) by each T. cultratus female was recorded. Egg masses were kept for three weeks and all parasitoid adults obtained were identified to species based on morphological characteristics (Talamas et al., 2017). The same experiment was repeated in reverse order, providing eggs first to T. cultratus followed by T. japonicus.