, Volume 81, Issue 1, pp 104–110 | Cite as

Interactions among phytophagous insect species colonizing cones of white fir (Abies concolor)

  • Patrick J. Shea
Original Papers


The insect complex colonizing white fir (Abies concolor [Gord. and Glend.] Lindl.) cones is composed of eleven species that can be separated into three feeding guilds: the seed-mining guild, Megastigmus pinus Parfitt, M. rafni Hoffmeyer, Earomyia abietum McAlpine; the cone-and seed-mining guild, Dioryctria abietivorella Grote, Eucosma prob. siskiyouana (Kearfoot), Cydia prob. bracteatana (Fernald), Barbara sp.; the scale-and bract-feeding guild, Asynapta hokinsi (Felt), Dasineura prob. abiesemia Foote, Ressiliella conicola (Foote), Lasiomma abietis Huckett). In three of four study sites the cone crop decreased from one year to the next. As cone crop size decreased there was a concomitant increase in the percent of cones with more than one species. In addition, there was a shift toward an increased co-occurrence of members of different guilds within a single cone. Both positive and negative interactions were detected between selected species-pairs. Present-day competition was only inferred between species-pairs belonging to the cone and seed-mining guild. Decreasing resources over time, combined with increasing insect populations and the absence of acceptable alternate hosts appeared to be important factors for setting conditions conducive to interspecific competition. It is hypothesized, that the aperiodicity of white fir cone crops was important in keeping insect populations below levels which would result in interspecific competition. The possible elimination of aperiodicity in cone crops of white fir, such as might occur in managed seed orchards, may lead to decreased species diversity via competitive exclusion and thereby simplify development of IPM programs.

Key words

Cone/seed insects Competition Abies concolor Interactions 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Begon M, Harper JL, Townsend CR (1986) Ecology. Individuals, populations, and communities. Sinauer Assoc Mc Sunderland, Massachusetts, pp 876Google Scholar
  2. Connell JH (1980) Diversity and coevolution of competitors, or the ghost of competition past. Oikos 35:131–138Google Scholar
  3. Connell JH (1983) On the prevalence and relative imprtance of interspecific competition: Evidence from field experiments. Am Nat 122:661–696Google Scholar
  4. Connor EF, Simberloff D (1979) The assembly of species communities: chance or competition? Ecology 60:1132–1140Google Scholar
  5. DeAngelis DL, Waterhouse JC (1987) Equilibrium and nonequilibrium concepts in ecological models. Ecol Monogr 57:1–21Google Scholar
  6. Diamond JM (1983) Laboratory, field, and natural experiments. Nature 304:586–587Google Scholar
  7. Foote RH (1956) Gall midges associated with cones of western forest trees (Diptera: Itonidae). J Wash Acad Sci 46:48–57Google Scholar
  8. Hairston NG, Smith FE, Slobodkin LB (1960) Community structure, population control and competition. Am Nat 44:421–425Google Scholar
  9. Harvey PH, Colwell RK, Silvertown JW, May, RW (1983) Null models in ecology. Annu Rev Ecol Syst 14:189–211Google Scholar
  10. Hastings A (1987) Can competition be detected using species cooccurrence data? Ecology 68:117–123Google Scholar
  11. Hedlin AF, Yates III HO, Tovar DC, Ebel BH, Koerber TW, Merkel EP (1981) Cone and seed insects of Northern American conifers. Can For Serv, US For Serv, Secretaria de Agricultura y Recursos Hidraulicos, Mexico, pp 122Google Scholar
  12. Keen FP (1958) Cone and seed insects of western forest trees. US Dept Agriculture, Forest Service, Tech Bull 1169, pp 168Google Scholar
  13. Lawton JH, Strong DR (1981) Community patterns and competition in folivorous insects. Am Nat 118:317–338Google Scholar
  14. Mattson WJ (1971) Relationship between cone crop size and damage by insects in red pine seed production areas. Can Entomol 103:617–621Google Scholar
  15. Mattson WJ (1986) Competition for food between two principal cone insects of red pine Pinus resinosa. Environ Ent 15:88–92Google Scholar
  16. Miller GE, Hedlin AF, Ruth DS (1984) Damage by two Douglasfir cone and seed insects. J Entomol Soc B C 81:46–50Google Scholar
  17. Root RB (1967) The niche exploitation pattern of the blue-jay gnatcatcher. Ecol Monogr 37:317–350Google Scholar
  18. Roughgarden J (1983) Competition and theory in community ecology. Am Nat 122:583–601Google Scholar
  19. Schoener TW (1974) Resource paritioning in ecological communities. Science 189:27–39Google Scholar
  20. Schoener TW (1983) Field experiments on interspecific competition. Am Nat 122:240–285Google Scholar
  21. Shea PJ (1989) Phytophagous insect complex associated with cones of white fir (Abies concolor [Gord. and Glend.] Lindl.) and its impact on seed production. CanEnt 121:699–708Google Scholar
  22. Toft CA, Shea PJ (1983) Determining communitywide patterns: Estimating power strengthens statistical inference. Am Nat 122:618–625Google Scholar
  23. Toft CA, Trauger DL, Murdy HW (1982) Test for species interactions: Breeding phenology and habitat use in subarctic ducks. Am Nat 120:586–613Google Scholar
  24. Wiens JA (1977) On competition and variable environments. Sci Am 65:590–597Google Scholar

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Patrick J. Shea
    • 1
  1. 1.Pacific Southwest Forest and Range Experiment StationUSDA/Forest ServiceBerkeleyUSA

Personalised recommendations