Skógræktarritið - 15.05.2001, Qupperneq 181

but see Hunter and Elkinton
1999).
As regards mortality of young
larvae, in a greenhouse experi-
ment where natural enemies and
abiotic conditions were under
control, the biggest difference in
survival to the end of second
instar was found between trees
with low contents of both pro-
teins and hydrolizable tannins (96
% of survivors) and trees with
high levels of both proteins and
hydrolizable tannins (70 %).
Although the causes of this pat-
tern are uncertain, likely, bound-
ing of proteins was more effective
when concentration of both pro-
teins and tannins were in was
high concentration (see Zucker
1983 for further discussion), this
would decrease larval growth and
subsequently the probabilities of
dying increased. Interestingly,
individuals who died were those
recording lightest weight at the
beginning of the instar. This last
finding is particularly relevant
when we try to extrapolate the
results to natural conditions.
Mortality in the greenhouse was
unusually low in first instar com-
pared to natural patterns (person-
al observation) and causes of
death during the second instar
were presumably not the same as
in the field. However, results sug-
gest that the main effect of a poor
food quality food is to weaken
individuals feeding on it and this
will probably interact with other
abiotic factors such as tempera-
ture and natural enemies
(Virtanen and Neuvonen 1999).
Acknowledgements
I am grateful to the staff of Kevo
Subarctic Institute Station and
Satakunta Environmental Re-
search Centre for their assistance
during the experiments, to Erkki
Haukioja for introducing me to the
study system, to Seppo Neuvonen
and Kai Ruohomaki for discussing
SKÓGRÆKTARRITIÐ 2001 l.tbl.
with me about ballooning experi-
ments, to Marianna Riipi for her
assistance during the greenhouse
experiment, and to the organizers
of the NSSE workshop for provid-
ing me the opportunity to discuss
References
AYRES, M. P. and MACLEAN, S. F. 1987.
Development of birch leaves and the
growth energetics of Epirrita autumnata
(Geometridae). Ecology 68:558-568.
BUCHNER, A„ ERDFELDER, E. and FAUL,
F. 1997. How to Use G*Power. Available
at: http://www. psychologie.uni-trier.de:
8000/projects/gpower/how_to_use_gpo
wer.html.
GHENT, A. W. 1999. Studies of ballooning
and resulting patterns of locally conta-
gious distribution of the bagworm
Tryridopteryx epfiemeraeformis (Haworth)
(Lepidoptera: Psychidae). Am. Mid. Nat.
142: 291-313.
HARRISON, S. 1995. Lack of strong induced
and maternal effects in tussock moths
(Orgyia vetusta) on bush lupine (Lupinus
arboreus). Oecologia 103: 343-348.
HUNTER, A. F. and ELKINTON, J. S. 2000.
Effects of synchrony with host plant on
populations of a spring feeding
Lepidopteran. Ecology8l: 1248-1261.
HUNTER, M. D„ VARLEY, G. C. and
GRADWELL, G. R. 1997. Estimating the
relative roles of top-down and bottom-up
forces on insect herbivore populations: a
classicstudy revisited. Proc. Natl. Acad.
Sci. USA 94:9176-9181.
KALLIO, P. and LEHTONEN, J. 1973. Birch
forest damage caused by Oporinia autum-
nata (Bhk.) in Utsjoki, N. Finland. Rep.
Kevo Subarctic Res. Stat. 10: 55-69.
KAUSE, A„ OSSIPOV, V„ HAUKIOJA, E„
LEMPA, K. and HANHIMÁKI, S. 1999.
Multiplicity of biochemical factors of
insect resistance in mountain birch.
Oecologia 120:102-112.
LEATHER, S. R . and WALSH, P. J. 1993. Sub-
lethal plant defences the paradox
remains. Oecologia93: 153-155.
LEMPA, K„ MARTEL, J„ KORICHEVA, J„
HAUKIOJA, E„ OSSIPOV, V., OSSIPOVA,
S. and PIHLAJA, K. 2000. Covariation of
fluctuating asymmetry, herbivory and
chemistry during birch leaf expansion.
Oecologia 122: 354-360.
NURMI, K„ OSSIPOV, V., HAUKIOJA, E„
PIHLAJA, K. 1996. Variation of total phe-
nolic content and individual Iow-molecu-
lar-weight phenolics in foliage of moun-
tain birch trees (Betula pubescens ssp.
tortuosssa). J. Chem. Ecol. 22: 2023-2040.
NYLIN, S. and JANZ, N. 1996. Host plant
preferences in the comma butterfly
(Polygonia c-album): do parents and off-
spring agree? Ecoscience 3: 285-289.
OSSIPOV, V., LOPONEN, J„ OSSIPOVA, S„
HAUKIOJA, E. and PIHLAJA, K. 1997.
these results. Seppo Neuvonen
made useful comments on the
paper. The study was founded by
the European Commission
through TMR-Marie Curie fellow-
ship (ERBFMBICT983034).
Gallotannins of birch Betula pubescens
leaves: HPLC separation and quantifica-
tion. Biochem. Syst. Ecol. 25:493-504.
ROFF, D. A. 1990. The evolution of flightless-
ness in insects. Ecol. Monogr. 60: 389-421.
RUOHOMÁKI, K„ TANHUANPÁÁ, M„
AYRES, M. P„ KAITANIEMI, P„ TAM-
MARU, T. and HAUKIOJA, E. 2000 |iw
press]: Causes of cyclicity of Epirrita autum-
nata (Lepidoptera, Geometridae) -
grandiose theory and tedious practice.
Pop. Ecol. 00: 0000-0000.
SAS INSTITUTE. 1996. SAS/STAT software:
changes and enhancements through
Release 6.11. SAS Institute, Cary, North
Carolina, USA.
SUOMELA, J„ OSSIPOV, V. and HAUKIOJA,
E. 1995. Variation among and within
mountain birch trees in foliage phenols,
carbohydrates and amino acids, and in
growth of Epirrita autumnata larvae. J.
Chem. Ecol. 21:1421-1446.
TAMMARU, T. and HAUKIOJA, E. 1996.
Capital breeders and income breeders
among Lepidoptera: consequences to
population dynamics. Oikos 77: 561-564.
TAMMARU, T„ KAITANIEMI, P. and
RUOHOMÁKI, K. 1995. Oviposition choic-
es of Epirrita autumnata (Lepidoptera,
Geometridae) in relation to its eruptive
population dynamics. Oikos 74: 296-304.
TAMMARU, T„ KAITANIEMI, P. and
RUOHOMÁKI, K. 1996. Realized fecundi-
ty in Epirrita autumnata (Lepidoptera:
Geometridae): relation to body size and
consequences to population dynamics.
Oikos 77:407-416.
THOMPSON, J. N. 1988a. Evolutionary ecol-
ogy of the relationship between oviposi-
tion preference and performance of off-
spring in phytophagous insects.
Entomol. Exp. Appl. 47: 3-14.
THOMPSON, J. N. 1988b. Coevolution and
alternative hypothesis on insect/ plant
interactions. Ecology 69: 893-895.
TIKKANEN, O.-P. 2000. Adaptation of a
generalist moth, Operophtera brumata, to
host plants. Ph.D. Dissertations in
Biology 1, University of Joensuu,
Finland. Abstract available at
http://bio.joensuu.fi/PhD/tikkanen.pdf.
VIRTANEN, T. and NEUVONEN, S. 1999.
Performance of moth larvae on birch in
relation to altitude, climate, host quality
and parasitoids. Oecologia 120: 92-101.
ZUCKER, W. V. 1983. Tannins: does struc-
ture determine function? An ecological
perspective. Am. Nat. 121: 335-365.
179