Diversity and specificity of sap‐feeding herbivores and their parasitoids on Australian fig trees

Abstract

The ecology, diversity, and parasitoid complex of plant–sap feeding insects of the family Homotomidae (Hemiptera: Psylloidea) specialised on fig trees (Ficus) have so far received little research attention. They are ecologically important, however, as occasional outbreaks of the homotomid Mycopsylla fici may cause complete defoliation of its host plant, the Moreton Bay fig (Ficus macrophylla). Mycopsylla proxima, the only other species reported from Australia, feeds on F. rubiginosa without any recorded outbreaks. We searched for homotomids and their parasitoids on eight Ficus species on the east coast of Australia, Lord Howe Island (LHI), and in Auckland, New Zealand, and detected them on three Ficus species. Using mitochondrial and nuclear DNA sequences, we delimited three Mycopsylla species, including a putative new species on F. watkinsiana. We also characterised six (including one previously described) parasitoid species of the genus Psyllaephagus (Hymenoptera: Encyrtidae) based on congruent morphological characters and molecular data. Each of the homotomid species was highly host specific to a single fig species, whereas parasitoid species varied in host specificity: three host specific to M. fici and three host generalists. Geographic distribution varied among parasitoid species; e.g. one host‐specific species was found on both the mainland and LHI, but a second species only on LHI. Our study revealed previously unrecognised diversity in fig homotomids and especially in their parasitoids. The herbivores and parasitoids showed contrasting patterns of host specificity. Interestingly, M. fici, the only outbreak species, had the highest diversity of associated parasitoid species and was the only species with host‐specific parasitoids.

An ancient and a recent colonization of islands by an Australian sap‐feeding insect

“…The M. fici population on LHI may represent such a case. Our current study shows divergence of nuclear microsatellites from mainland populations, and reinforces our previous studies showing that the insects from LHI have distinct mtDNA haplotypes and harbour a different strain of Wolbachia endosymbiont (Fromont et al., , ).…”

“…We found support for an older northern (Brisbane region) origin for the LHI population of M. fici and a recent southern (Sydney region) origin for the population in Auckland. These results from nuclear microsatellites match patterns of similarity observed in the mtDNA of these insects (Fromont et al., ). The estimated colonization of LHI is very recent (5,140–43,700 years ago) compared to the estimated age of the island (7 Myr), which could have various explanations.…”

“…fici samples from Auckland with insects from the southeastern part of the native Australian range, and also showed that LHI insects formed a clade genetically distinct from the Australian mainland insects (Fromont et al, 2017). Another study focusing on bacterial endosymbionts provided evidence that the LHI insects carry a different strain of Wolbachia bacteria than the mainland ones (Fromont et al, 2016).…”

“…ex Pers (Moraceae: Urostigma sect. Malvanthera; Dixon, 2003;Froggatt, 1901;Fromont, DeGabriel, Riegler, & Cook, 2017). The insect has periodic massive outbreaks, which can cause up to 70%-100% defoliation of a given tree (e.g., in Sydney in 1996, Newman, 2004.…”

“…It was introduced to Auckland (New Zealand) as an ornamental plant in the mid 19th century, and is now common on the North Island along with its pollinator wasp (Gardner & Early, 1996). Mycopsylla fici is found along the eastern coast of Australia and also on LHI, corresponding to the natural distribution of its host tree (Fromont, Riegler, & Cook, 2016;Fromont et al, 2017) and was reported in NZ for the first time in 1995 (Bain, 2004).…”