Spatial pattern formation in an insect host-parasitoid system

Science

Volumn 278, Issue 5343, 1997, Pages 1619-1621

  Maron, John L ^a,c   Harrison, Susan ^b  

^a UNIVERSITY OF WASHINGTON   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

^c UNIVERSITY OF CALIFORNIA DAVIS   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

HOST-PARSITOID INTERACTION; POPULATION OUTBREAK; PREDATOR-PREY INTERACTION; SPATIAL PATTERN; TUSSOCK MOTH;

ARTICLE; COMPUTER SIMULATION; ECOLOGY; HOST PARASITE INTERACTION; LEPIDOPTERA; MATHEMATICAL ANALYSIS; NONHUMAN; POPULATION DENSITY; PREDATION; PRIORITY JOURNAL; SPATIAL ORIENTATION;

LEPIDOPTERA; LYMANTRIIDAE; ORGYIA VETUSTA;

EID: 0030697159     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.278.5343.1619     Document Type: Article

References (28)

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13. Our study site is the University of California's Bodega Marine Reserve (BMR) in central coastal California. Grasslands on the BMR abruptly give way to sand dunes where the Pacific Plate abuts the San Andreas fault zone. Bush lupine are sparser in dunes than in grasslands.
14. Tussock moths are native to the area. At our study site, tussock moth larvae feed exclusively on bush lupine, Lupinus arboreus. At other coastal sites to the south, O. vetusta feed on another perennial lupine, silver lupine, L. chamissonis. Larvae hatch from overwintering egg masses in April and May. and undergo five to six instars before pupation. Eclosion and mating occur 1 to 2 weeks after pupation; flightless females lay a single mass of 100 to 300 eggs on the undersides of lupine bushes. For the past 10 years, a high-density tussock moth population has been located within a 1.5-ha lupine stand at our site.
15. S. Harrison, Oecologia 99, 29 (1994).
16. _, Ecol. Entomol. 22, 158 (1997).
17. _, Oecologia 103, 343 (1995).
18. _ and C. Wilcox, ibid. 101, 309 (1995). Predators include the generalist ant Formica Iasioides, several species of web-building spiders, and carabid beetles.
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20. W. G. Wilson S. P. Harrison, A. Hastings, K. A. McCann, in preparation; A. Hastings, S. Harrison, K. A. McCann, Proc. R. Soc. London Ser. B, in press.
21. W. G. Wilson S. P. Harrison, A. Hastings, K. A. McCann, in preparation; A. Hastings, S. Harrison, K. A. McCann, Proc. R. Soc. London Ser. B, in press.
22. Use of two transects creates some risk of spatial autocorrelation; an ideal design would be to place our treatments in random directions from the natural outbreak. However, we were constrained by the fact that the outbreak is located on a peninsula.
23. In a three-way analysis of variance (ANOVA) on mean numbers of larvae per bush, the main effect of predator exclusion was statistically significant [F(1,38) = 24.3 P < 0.001], but the effect of distance, transect location, and interaction terms were not (P > 0.1).
24. We used a logit transformation on (1 + pupa number) to equalize the variance between treatments and then performed a three-way ANOVA on transformed data. Main effects of distance and transect location were statistically significant [F(1,37) = 15.5 and 5.3, respectively; P < 0.03); predator exclusion was marginally significant [F(1,37) = 5.3; P = 0.058]. No interaction terms were significant.
25. 2 = 0.733 and 0.657 for dune and grassland, respectively; P < 0.004).
26. In a three-way ANOVA on number of egg masses per bush, the main effect of distance and the distance × location interaction were statistically significant [F(1,37) = 31.5 and 17.5, respectively; P < 0.001]. No other main effects or interaction terms were significant.
27. We collected one tussock moth egg mass from each experimental bush that had egg masses, dissected it under a dissecting microscope, and counted the number of eggs.
28. We thank M. Greaves and B. Shubin for field assistance H. C. J. Godfray, A. Hastings, A. R. Ives, K. S. McCann, P. Turchin, and W. G. Wilson provided much theoretical inspiration and M. Holyoak, M. Hoopes, S. Strauss, and D. Strong made helpful comments on the manuscript. Funded by NSF grant DEB-9508546.