PSYLLIDS or 'jumping plant lice' (PSYLLOIDEA, HEMIPTERA)
Welcome to psyllids.org
This site is an ongoing project to present and summarize general information about psyllids, their biology, host plant associations and the economic and ecological impact that pysllids have on man-made and natural environments. It also presents specific research on psyllid faunas in different parts of the world.
Psyllids (Psylloidea, Hemiptera)
Psyllids or 'jumping plant lice' are small phytophagous, phloem feeding insects that are typically monophagous (feed on a single plant) or oligophagous (feed on a few related plants). Together with aphids, coccids and whiteflies they form the monophyletic group, Sternorrhyncha (Homoptera), which is considered basal within the true bugs (Hemiptera). Psyllids are probably the most benign of these four insect groups and therefore the least well studied. ‘Sternorrhyncha’ refers to the rearward position of the mouthparts relative to the head. The Homoptera are no longer considered to be monophyletic, refer to:
'Hemiptera and Homoptera' at University of California, Berkeley
and the Hemipteran 'Tree of Life' page
Psyllid fossils have been found from the early Permian before the angiosperms evolved. Thus, psyllids may have primitively fed on gymnosperms, or even lycopods (Hodkinson, 1980). The explosive radiation of the angiosperms in the Cretaceous was paralleled by a massive radiation of associated insects, and many of the morphological and metabolic characters that the angiosperms exhibit may have evolved as defenses against herbivorous insects. Primitively, insects were probably saprophagous with a shift to the more complex lifestyle of herbivory, a secondary adaptation (Mitter, Farrell & Wiegmann, 1988). Allocation of resources in plants can vary seasonally, within an individual plant, between individuals, and from species to species. An example of this is the phenological changes in chemical profile of flowers, leaves, stems, and fruit for the legume species, Adenocarpus (Greinwald et al., 1992). The changing character of an individual plant is a complex and challenging landscape to herbivorous insects (Wink, 1992). An insect that attains an adaptive peak on one plant species is likely to be in an adaptive trough on another species (Janzen, 1979).
Insect/plant interactions have been important in defining models of coevolution and cospeciation. In the Canary Islands metapopulation structures combined with local variation in host plant ecology and habitat/island fragmentation may support Thompson’s ‘geographic mosaic theory of coevolution’ (Thompson 1994; Gomulkiewicz et al. 2000; Thompson & Cunningham 2002; Percy 2003). However, in many cases it is believed that herbivorous insect speciation is sequential in relation to the host plant (Jermy, 1976; Menken, 1996; Percy et al. 2004).
Plant/insect interactions have been important in contributing to the debate on coevolution. Thompson (1994) challenged the conventional co-speciation model in his book ‘The Coevolutionary Process’ pointing out that - interactions between plants and insects may not result in fixed traits in species that can then be mapped onto a phylogenetic tree, but instead there may be a shifting geographic mosaic, combining differences in the physical environment and the local genetic and demographic structure of populations. So that plant/insect interactions may involve localized coevolution, that is not taken into consideration by a strict model of pairwise species for species coevolution.
Greinwald, R., Bachmann, P., Witte, L., Acebes-Grinoves, J.R. & Czygan, F-C. (1992) Taxonomic significance of alkaloids in the genus Adenocarpus (Fabaceae-Genisteae). Biochemical and Systematic Ecology 20, 69-73.
Hodkinson, I. D. (1980) Present-day distribution patterns of the holarctic Psylloidea (Homoptera: Insecta) with particular reference to the origin of the nearctic fauna. Journal of Biogeography 7, 127-146.
Janzen, D. H. (1979) New horizons in the biology of plant defences. In Herbivores. Their Interaction with Secondary Plant Metabolites. (ed. G. A. Rosenthal and D. H. Janzen), pp. 331-350. Academic Press, New York.
Percy, D.M. (2003) Radiation, diversity and host plant interactions among island and continental legume-feeding psyllids. Evolution 57, 2540-2556. pdf (1599 kb)
Percy, D.M., Page, R.D.M. & Cronk, Q.C.B. (2004) Plant-insect interactions: double-dating associated insect and plant lineages reveals asynchronous radiations. Systematic Biology 53, 120-127. pdf (233 kb)
All images, unless otherwise noted, are copyright © Diana M. Percy
Created 2002. Updated 20/01/2005. Return to top of page
psyllid taxonomy, host plants, and bibliography site by David Ouvrard et al