Study system
Insects and their parasitoids are an excellent system for studying
effects of climate change on species interactions (Hance et al.2007; Jeffs & Lewis 2013). The strength of host-parasitoid interactions
are predicted to be particularly sensitive to phenological shifts and
global warming due to 1) age-related vulnerability of host to successful
parasitism and 2) high thermal sensitivity given their obligate ties to
host thermal performance (Tuda & Shimada 1995; Hance et al.2007). Furthermore, the duration of host vulnerability and degree of
phenological synchrony have been suggested to influence local stability
within host-parasitoid systems. Stable host-parasitoid interactions
require that not all hosts have been parasitized, so some degree of
asynchrony may be adaptive (Singer & Parmesan 2010). Thus, precise
timing is critical for these tightly co-evolved interactions and any
shift in the optimal temporal overlap is hypothesized to have
significant effects on long-term persistence (Tuda & Shimada 1995).
We used a native Drosophila -parasitoid system from the seasonal
tropical forests of North Queensland, Australia. Two species ofDrosophila , D. sulfurigaster and D. birchii , were
collected from the field in March 2018 and maintained at the Czech
Academy of Sciences (CAS) as a collection of isofemale lines (Shipped to
the Czech Republic under permit no. PWS2016-AU-002018 from Australian
Government, Department of the Environment). These species coexist across
elevational gradients that span 900m at Kirrama (S18° 12.676’ E145°
47.530’) and Paluma (S19° 00.386’ E146° 12.732’) mountain ranges in
Queensland, and are attacked by a shared suite of parasitoid wasp
species
(Jeffset al. 2021). Individuals used in this experiment were collected
as eggs from mass bred population cages, which originated from eight
isofemale lines from each fly species respectively.
We used two hymenopteran parasitoid species, collected from the same
tropical Australian locations: Asobara sp.1 (Braconidae:
Alysiinae; strain KHB from site Kirrama, elevation 900m, reference
voucher no. USNMENT01557097, reference sequence BOLD process ID:
DROP043-21, and Ganaspis sp.1 (Figitidae: Eucolinae; strain 69B
from site Kirrama, elevation 900, reference voucher no. USNMENT01557100,
USNMENT01557297 reference sequence BOLD process ID:DROP164-21) (Lueet al. 2021). These species await description by taxonomists but
are precisely identified above so that this study can be linked to
species names once available. Each parasitoid species specializes on
larval stages of Drosophila and are known to successfully attackD. birchii and D. sulfurigaster . All parasitoids were
maintained on D. melanogaster , so no parasitoid used in this
experiment had prior experience with D. sulfurigaster or D.
birchii , and thus no acquired oviposition preference.