Abstract
Host specificity of parasitoids may be measured by various specialization indices to assess the variation of interaction strength among species and the structure of the wider interaction network. However, the conclusions from analyses at the species and network levels may differ, which remains poorly explored. In addition, the recovery of cryptic species of hosts and parasitoids with molecular data may affect the structure of inferred interaction links. We quantified host specificity of hymenopteran parasitoids (family Encyrtidae) on armored scale insects (Hemiptera: Diaspididae) from a wide geographic sampling range across the Chinese Mainland based on both morphological and molecular species delimitation. Mitochondrial COI and nuclear 28S markers detected high cryptic species diversity in the encyrtids and to a lesser degree in the diaspidids, which divided generalist morphospecies into complexes of specialists and generalists. One‐to‐one reciprocal host–parasite links were increased in the molecular data set, but different quantitative species‐level indices produced contrasting estimates of specificity from various one‐to‐multiple and multiple‐to‐multiple host–parasite links. Network indices calculated from DNA‐based species, compared to morphology‐based species definitions, showed lower connectance and generality, but greater specialization and compartmentalization of the interaction network. We conclude that a high degree of cryptic species in host–parasitoid systems refines the true network structure and may cause us overestimating the stability of these interaction webs.
Highlights
Insect parasitoids have been commonly included in food web studies (Lafferty, Dobson, & Kuris, 2006), and host specificity has been suggested to have a significant effect on the structure of interaction webs
The assessment of host specificity and food web structure relies on the accurate delimitation of species, which may be affected by the existence of unrecognized “cryptic” species within the morphologically distinguishable entities (Wirta et al, 2014)
Stone, Hearn, Lohse, and Roslin (2010), studying gall-inducing wasps, were the first to investigate the effects of resolving cryptic species on the structure of a host–parasitoid food web, but despite the greater number of entities and difference in species circumscriptions, they found the overall structure of the interaction web to be largely unchanged
Summary
As one of the most fundamental species traits of parasitoids (Poulin & Keeney, 2008) has been of great interest to ecological and evolutionary biologists (Dyer et al, 2007; Godfray, 1994; Hawkins, 1994; Machado, Robbins, Gilbert, & Herre, 2005; Memmott, Godfray, & Gauld, 1994; Morris, Gripenberg, Lewis, & Roslin, 2014; Novotny & Basset, 2005; Rohde, 1992; Willig, Kaufman, & Stevens, 2013). The effects of molecular versus morphological species delimitation for the structure of interactions webs remain to be studied in a larger number of host–parasitoid systems sampled from a broader taxonomic and ecological range. Among various other parasitoids reared from the same set of diaspidids, the encyrtid parasitoids obtained in the current study were mostly from the tribe Habrolepidini, which is composed of about 160 known species of about 0.5–2 mm body length (some species in our study are only 0.3 mm) Identification of these species has mainly relied on color patterns on antenna and forewing, or dimensions of antennal segments or setae on the forewing (Noyes & Hayat, 1984; Trjapitzin, 1989). A side-by-side comparison of networks constructed under morphological and molecular species delimitation can reveal the specific effects of taxonomic resolution on the structure of interaction webs
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