Premium
Trophic cascades in bell miner‐associated dieback forests: Quantifying relationships between leaf quality, psyllids and P syllaephagus parasitoids
Author(s) -
Steinbauer Martin J.,
Sinai Katherine M. J.,
Anderson Annette,
Taylor Gary S.,
Horton Bryony M.
Publication year - 2015
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/aec.12170
Subject(s) - biology , abundance (ecology) , ecology , trophic level , parasitism , leaf miner , botany , rainforest , relative species abundance , host (biology) , lepidoptera genitalia
Coteries of the meliphagid bird M anorina melanophrys are associated with a form of eucalypt defoliation and recovery called bell miner‐associated dieback ( BMAD ). Through their defence of cooperative colony boundaries against other insectivorous birds, bell miners may foster greater abundances of lerp‐forming psyllids ( H emiptera: A phalaridae), some of which reduce the lifespan of leaves. Trophic cascades in BMAD forests need to be understood to have a complete picture of regulatory processes. We studied relationships between leaf quality, psyllid and P syllaephagus parasitoid/hyperparasitoid abundances within the Gondwana Rainforest World Heritage Area, NSW , Australia; our focal tree species were E ucalyptus propinqua and E . biturbinata . E ucalyptus biturbinata had tougher leaves than E . propinqua ; leaf toughness of both species varied with site and tree. We found a statistically significant, negative relationship between toughness (surrogate for leaf age) and foliar nitrogen content; younger leaves had higher nitrogen contents. Both bell miner abundance and foliar nitrogen were positively correlated with psyllid abundance. The abundance of G lycaspis species (the psyllid that produces lerps with the highest sugar content) was more closely correlated with foliar nitrogen content than was the abundance of all five psyllid genera combined. We identified 14 P syllaephagus spp./morphospecies, comprising 11 primary parasitoids and three hyperparasitoids. The abundance of all P syllaephagus combined was positively correlated with the abundance of lerps. However, psyllid parasitism was not correlated with the abundance of lerps. The abundance of the three hyperparasitoids was positively correlated with the abundance of P syllaephagus hosts. The availability of epicormic foliage (young, morphologically juvenile leaves produced following defoliation) is likely to alter the nutritional ecology underpinning the diversity and abundance of psyllid populations. Higher quality epicormic foliage should favour populations of G lycaspis species (by enhancing nymphal survival) creating lerp hotspots that induce residency by opportunistic bell miners. The positive contribution of induced amelioration, interacting with feedbacks from parasitoids and hyperparasitoids, to BMAD requires longitudinal investigation.