Download Competition, predation and species responses to environmental

OIKOS 106: 217 /224, 2004
Competition, predation and species responses to environmental
change
Lin Jiang and Alexander Kulczycki
Jiang, L. and Kulczycki, A. 2004. Competition, predation and species responses to
environmental change. / Oikos 106: 217 /224.
Despite much effort over the past decade on the ecological consequences of global
warming, ecologists still have little understanding of the importance of interspecific
interactions in species responses to environmental change. Models predict that
predation should mitigate species responses to environmental change, and that
interspecific competition should aggravate species responses to environmental
change. To test this prediction, we studied how predation and competition affected
the responses of two ciliates, Colpidium striatum and Paramecium tetraurelia , to
temperature change in laboratory microcosms. We found that neither predation nor
competition altered the responses of Colpidium striatum to temperature change, and
that competition but not predation altered the responses of Paramecium tetraurelia to
temperature change. Asymmetric interactions and temperature-dependent interactions
may have contributed to the disparity between model predictions and experimental
results. Our results suggest that models ignoring inherent complexities in ecological
communities may be inadequate in forecasting species responses to environmental
change.
L. Jiang and A. Kulczycki, Dept of Ecology, Evolution and Natural Resources, Cook
College, Rutgers Univ., 14 College Farm Road, New Brunswick, NJ 08901-8551, USA.
Present address for LJ: Inst. of Marine and Coastal Sciences, Rutgers Univ., 71 Dudley
Road, New Brunswick, NJ 08901, USA ([email protected]).
Over the 20th century, global surface temperature has
increased by an average of 0.68C, and is projected to
increase by 1.4 to 5.88C over the period 1990 to 2100
(IPCC 2001). Such rapid climate change, unparalleled at
least in the past 1000 years, is likely to have profound
ecological consequences. Ecologists have taken on the
challenge of uncovering the potential impacts of climate
change on ecological systems (Lubchenco et al. 1991).
The past decade has seen a large number of climaterelated ecological studies that significantly improved our
understanding of the ecological impacts of climate
change (reviewed by Hughes 2000, McCarty 2001,
Walther et al. 2001). Many studies have documented
ecological changes in natural communities associated
with climate change. Species have responded by changes
in their demographic rates (Myneni et al. 1997, Post and
Stenseth 1999, Barber et al. 2000), altered timings in lifehistory events (Beebee 1995, Crick et al. 1997, Bradley et
al. 1999, Brown et al. 1999, Dunn and Winkler 1999,
Post and Stenseth 1999, Inouye et al. 2000, Menzel and
Estrella 2001, Post et al. 2001), and changes in geographic range and abundance (Graham and Grimm
1990, Grabherr et al. 1994, Barry et al. 1995, Forchhammer et al. 1998, Reid et al. 1998, Thomas and Lennon
1999, Kiesecker et al. 2001, Parmesan et al. 1999, Sæther
et al. 2000, Sturm et al. 2001). Population extinctions
(Pounds et al. 1999, Harrison 2000, Kiesecker et al.
2001) and changes in community structure (Grabherr et
al. 1994, Brown et al. 1997, Alward et al. 1999, Post et al.
1999) have also occurred.
Despite these considerable efforts, ecologists still do
not have a good understanding of the role of species
Accepted 21 November 2003
Copyright # OIKOS 2004
ISSN 0030-1299
OIKOS 106:2 (2004)
217
interactions in responses to environmental change,
partly because past studies have primarily focused on
responses of single-species populations or whole ecosystems, largely ignoring the involvement of species interactions. This approach has often been justified by
assuming that the observed species responses essentially
reflected their direct physiological responses to environmental change. However, species interactions, particularly competition and predation, have been known to
play dominant roles in determining species abundance
and distribution (Connell 1983, Schoener 1983, Sih et al.
1985, Begon et al. 1998, Morin 1999), and they may
potentially affect how species respond to environment
change (Ives and Gilchrist 1993, Ives 1995, Lawton 1995,
Abrams 2002). Indeed, several empirical studies have
indicated the important effect of community structure
on species responses to environment change (Brown et
al. 1997, Davis et al. 1998a,b Post et al. 1999, Fox and
Morin 2001).
In this study, we examined the effects of interspecific
competition and predation on species responses to
temperature change. Species interactions may either
alleviate or aggravate a species’ response to environmental change. Models, based on the assumption that
populations follow stationary population distributions
(analogous to stable equilibria, Ives and Gilchrist 1993)
and that environmental change affects population
growth rates, predict that species occupying distinct
ecological roles are buffered against environmental
change and that species sharing similar ecological
positions are susceptible to environment change (Ives
and Gilchrist 1993, Ives 1995). A corollary that follows is
that predator /prey interactions should buffer species
against environmental change, and that competitive
interactions should exacerbate species response to environmental change (Ives and Gilchrist 1993, Ives 1995).
Empirical studies on lake ecosystems also led to similar
speculations (Carpenter et al. 1993).
These predictions make biological sense. Considering
a linear food chain, if the abundance of the prey
increases (decreases) in response to environmental
change, such positive (negative) response will lead to
the increase (decrease) in predator abundance, which
should put a limit on the prey response. The same logic
applies to the predator. In contrast, for species involved
in competitive interactions, an increase (decrease) in one
species’ abundance, in response to environmental
change, will lead to the decrease (increase) in the
abundance of other species. Such among-species inverse
density dependence should make competing species
relatively sensitive to environmental change.
Only one study has tested these predictions (Fox and
Morin 2001). In their experiments, Fox and Morin raised
temperature gradually to simulate global warming. This
approach, although a good representation of ongoing
climate change, makes it difficult for populations to
218
reach stationary population distributions. Because Ives
and Gilchrist’s models were based on the stationary
distribution assumption, the study of Fox and Morin
(2001) did not constitute a strictly valid test of the
models.
In this study, we instead used different constant
temperatures to simulate environmental change, as
populations are more likely to approach stationary
distributions in constant environments. We assembled
predator /prey communities and communities of competitors in laboratory microcosms, subjected them to
different temperature regimes, and examined how species
in different communities responded to warming. The
short generation times (/3 to 24 hours) of protozoan
species used in the experiments allowed us to collect
multi-generational population dynamics data over a
period of several weeks. We expected that the average
abundance of prey species engaged in predator /prey
interactions would be more buffered against temperature
change compared to without predators, and that the
average abundance of species engaged in competitive
interactions would be more affected by temperature
change compared to without competitors.
Material and methods
Three ciliate species were used: Colpidium striatum
(hereafter Colpidium ), Paramecium tetraurelia (hereafter
Paramecium ), and Didinium nasutum (hereafter Didinium ). Colpidium and Didinium were obtained from
Carolina Biological Supply Company (Burlington, NC,
USA), and Paramecium from the American Type
Culture Collection (Rockville, MD, USA). Colpidium
is reniform-shaped, about 50 mm in size; Paramecium is
slipper-shaped, about 120 /180 mm in size. Both are freeswimming bacterivores. Didinium is an oval-shaped
predator ranging in size from 100 to 200 mm, and it
actively searches and attacks suitable prey, such as
Colpidium and Paramecium , in the water column.
The experimental microcosms were 240 ml capped
glass bottles each containing 100 ml of nutrient medium
plus 2 wheat seeds. The medium was made from 0.55 g of
protozoan pellets (Carolina Biological Supply, Burlington, NC, USA) dissolved in 1 liter of well water. Bottles,
medium and wheat seeds were autoclaved before use.
Medium was first inoculated with three bacterial species:
Serratia marcescens, Bacillus cereus and Bacillus subtilis,
all obtained from Carolina Biological Supply Company
(Burlington, NC, USA). These bacteria served as food
resources for Colpidium and Paramecium . Bacterivores
were introduced into the microcosms 24 hours after
bacteria inoculation. The predatory species Didinium
was introduced into the microcosms one week after the
introduction of bacterivores.
OIKOS 106:2 (2004)
Our main experiments employed a factorial design in
which temperature and presence/absence of interspecific
interactions were the two main factors. The temperature
factor had three constant levels: 22, 26, and 308C. The
species interaction factor had three treatments: control
treatment with the bacterivore (Colpidium or Paramecium ) raised in monocultures, competition treatment
with the two bacterivores competing for resources
(Colpidium /Paramecium ), and predation treatment in
which the bacterivore was preyed upon by predators
(Colpidium /Didinium or Paramecium /Didinium ). We
set up three, four, and six replicates for the control,
competition, and predation treatment, respectively.
Higher replication was used in the predation treatment,
because among-replicate variation in the predation
treatment is generally of larger magnitude than in the
control and competition treatment (L. Jiang, pers. obs.).
Both control and competition experiments ran for 44
days. Colpidium /Didinium and Paramecium /Didinium
predation experiments ran for 37 and 18 days, respectively, reflecting the longer persistence time of Colpidium
than Paramecium in the predation treatment. For each
bacterivore (Colpidium and Paramecium ), we also measured its intrinsic growth rate at 22, 26, and 308C,
according to the procedures described in Fox and Morin
(2001).
We monitored population dynamics of each protist in
the microcosms every two to three days. To sample, we
swirled each microcosm to mix its content and used a
Pasteur pipette to withdraw approximately 0.35 ml of the
medium. We weighed each sample on an electronic scale
to determine its exact volume, and counted the number
of each protist in the sample under a Nikon SMZ-U
dissecting microscope. We replaced 10% of the medium
in each microcosm with fresh medium every week to
replenish nutrients and prevent metabolic waste buildup.
We recorded density for each protist species as the
number of individuals per ml and log transformed the
data (log10(individuals/ml/1)) to reduce heteroscedasticity in preparation for statistical analysis. We calculated
geometric mean density over time for each species,
excluding the post-extinction zero counts if species
went extinct before the end of the experiment. Our
analyses did not involve the predatory species Didinium ,
because we were only interested in how predation and
competition affect the responses of the two bacterivores,
Colpidium and Paramecium , to environmental warming.
We used geometric mean densities of bacterivores as
the main response variables in our analyses. We
performed separate analyses for the two bacterivores,
Colpidium and Paramecium . For each of them, we first
ran a one-way ANOVA to test whether its growth rate
and mean density in the control treatment (monocultures) was affected by ambient temperature. We then
performed two-way ANOVA on the data from control
and competition treatments for each bacterivore, with
OIKOS 106:2 (2004)
temperature and presence/absence of interspecific competition as the two main factors. Significant interaction
terms in the two-way ANOVA would indicate that
interspecific competition influences response to environmental change. We performed two-way ANOVA on the
data from control and predation treatments for each
bacterivore, with temperature and presence/absence of
predation as the two main factors. Significant interaction
terms in the two-way ANOVA would indicate that
predation influences responses to environmental change.
Results
The effects of temperature on Colpidium
Increasing temperature significantly reduced Colpidium
growth rate (one-way ANOVA, temperature: F2,6 /
47.18, P/0.002; Fig. 1). At all three temperatures in
monocultures (the control treatment), Colpidium grew
very quickly to high density, and then declined to
relatively steady density (Fig. 2, left panels). The steady
density was lower at higher temperatures (Fig. 2, left
panels). Increasing temperature significantly reduced
Colpidium average density in monocultures (one-way
ANOVA, temperature: F2,6 /179.41, P B/0.0001; Fig. 3).
In the Colpidium /Didinium predation experiment,
Didinium increased in abundance and reduced Colpidium abundance at all three temperatures (Fig. 2, right
panels). Sometimes population fluctuation of both
species was observed, but extinction of Colpidium never
occurred during the experimental period. Didinium
persisted for a shorter period of time at higher temperatures, perhaps due to lower prey abundance and higher
metabolic costs at higher temperatures. Both increasing
Fig. 1. The effects of temperature on the intrinsic growth rates
of Colpidium and Paramecium . Error bars represent one
standard error.
219
Fig. 3. Effects of temperature on mean population densities of
Colpidium and Paramecium . Upper and lower panels represent
Colpidium and Paramecium , respectively. Errors bars indicate
one standard error.
Fig. 2. Colpidium population dynamics in the control and
predation treatments at different temperatures. Left panels
represent the control treatment in which Colpidium was in
monoculture, and right panels represent the predation treatment
in which Colpidium was a prey of Didinium . Each panel
corresponds to one representative microcosm.
temperature and Didinium predation significantly reduced Colpidium average abundance (two-way ANOVA,
temperature: F2,21 /28.99, P B/0.0001, predation:
F1,21 /41.10, P B/0.0001; Fig. 3). However, the nonsignificant interaction terms in the two-way ANOVA
(F2,21 /0.89, P/0.4256) indicated that predation from
Didinium did not change the responses of Colpidium to
temperature change.
In the Colpidium /Paramecium competition experiment, Colpidium was not negatively affected by the
presence of Paramecium . In fact, Colpidium attained
higher abundance in the competition treatment than in
the controls (two-way ANOVA, competition: F1,15 /
12.22, P /0.0033; Fig. 3, 4). The non-significant interaction terms (F2,15 /0.21, P/0.8116) in the two-way
ANOVA indicated that competition from Paramecium
did not change the response of Colpidium to temperature
change.
220
The effects of temperature on Paramecium
Increasing temperature significantly increased Paramecium growth rate (one-way ANOVA, temperature:
F2,6 /6.29, P/0.0336; Fig. 1). In monocultures, Paramecium maintained a relatively steady density after
initial rapid population growth (Fig. 5, left panels).
Temperature change did not affect Paramecium mean
density in monocultures (one-way ANOVA, temperature: F2,6 /3.75, P /0.0879; Fig. 3).
In the Paramecium /Didinium predation experiment,
predation from Didinium reduced Paramecium abundance, and eventually caused Paramecium extinction in
all replicates at all three temperatures (Fig. 5, right
panels). In all microcosms, Paramecium uniformly went
extinct four days after the introduction of Didinium .
Predation from Didinium significantly reduced Paramecium average abundance before extinction (two-way
ANOVA, predation: F1,21 /808.21, P B/0.0001; Fig. 3).
However, the non-significant interaction terms in the
two-way ANOVA (F2,21 /1.49, P/0.2477) indicated
that predation from Didinium did not change the
responses of Paramecium to temperature change.
In the Colpidium /Paramecium competition experiment, Paramecium coexisted with Colpidium as the
OIKOS 106:2 (2004)
Fig. 4. Colpidium and Paramecium
population dynamics in the
competition treatment at different
temperatures. Each panel corresponds
to one representative microcosm.
sub-dominant species at 228C, went extinct in all
replicates before the end of the experiment at 268C,
and coexisted with Colpidium as the co-dominant species
at 308C (Fig. 4). Competition from Colpidium significantly reduced Paramecium average abundance (two-way
ANOVA, competition: F1,15 /673.72, PB/0.0001). Significant interaction terms between temperature and
competition in the two-way ANOVA (F2,15 /103.16,
P B/0.0001) revealed that competition from Colpidium
altered the response of Paramecium to temperature
change.
Discussion
Our experimental results, to a large extent, did not
support the hypothesis that a species engaged in
predator /prey interactions should be more buffered
against environmental change, and that species engaged
in competitive interactions should be more susceptible to
environmental change, compared to responses in the
absence of interspecific interactions. Increasing temperaOIKOS 106:2 (2004)
ture reduced both the growth rate and average density of
Colpidium in monocultures, but neither competition
from Paramecium nor predation from Didinium changed
its response to elevated temperature, although both
changed its average abundance. Increasing temperature
increased the growth rate but did not affect the average
density of Paramecium in monocultures. Predation from
Didinium also did not alter Paramecium’s response to
temperature change. However, competition from Colpidium did change the way Paramecium responded to
elevated temperatures. As the only case consistent with
the hypothesis, Paramecium was more affected by
temperature change in the presence of interspecific
competition: it went extinct at 268C, but coexisted with
Colpidium at 22 and 308C.
The extinction of Paramecium at 268C in the competition treatment is unexpected, because increasing temperature raised its growth rate and did not affect its
abundance in the absence of interspecific interactions,
and because increasing temperature reduced both the
growth rate and abundance of its competitor, Colpidium .
This contrasts with more general findings that species
coexist at intermediate temperatures and competitive
221
Fig. 5. Paramecium population dynamics in the control and
predation treatments at different temperatures. Left panels
represent the control treatment in which Paramecium was in
monoculture, and right panels represent the predation treatment
in which Paramecium was a prey of Didinium . Each panel
corresponds to one representative microcosm.
extinction or dominance occurs at extreme temperatures
(Park 1954, Hairston and Kellermann 1965, Wilson et
al. 1984, Phillips et al. 1995, Davis et al. 1998a,b,
Taniguchi and Nakano 2000). A probable explanation
is that at 268C the higher feeding rate of Colpidium
outweighed its lower density (compared with 228C),
translating into larger overall competitive effects on
Paramecium populations. The surprising responses of
Paramecium in the competition treatment suggest that,
at least for some species, it may be impossible to use their
direct physiological responses to predict how they would
respond to environmental change, if they are affected by
interspecific interactions.
So why is there such a discrepancy between the
hypothesis and our data? First, asymmetric interactions
between species may have complicated responses to
temperature change. In particular, our data showed
that interspecific competition negatively affected Paramecium but not Colpidium . This competitive asymmetry
222
was probably responsible for the differential responses of
Colpidium and Paramecium to temperature change in
the competition treatment. Interspecific competition
may be more likely to affect species responses to
environmental change in communities characterized
by diffuse competition, i.e. competitive interactions
in which species are affected more or less equally
(MacArthur 1972). Such communities may go through
significant changes in species composition and community structure, in the event of environmental change.
A second plausible explanation for the discrepancy
lies in the assumption of the models. In formulating their
models, Ives and Gilchrist (1993) assumed that environmental change only affects species growth rates. This
assumption fails to hold if environment change also
alters species interaction strength. For instance, temperature generally affects attack rates and handling
times of predators on their prey (Murdoch et al. 1984,
MacRae and Croft 1993, Elliott and Leggett 1996,
Sanford 1999). In our experiments, we did not estimate
the functional responses of the predatory species Didinium on its prey, but it is possible that temperaturedependent functional responses have contributed to the
finding that predation did not affect species responses to
elevated temperatures. Temperature may also alter
strength of competitive interactions. For species involved
in resource competition, such as Colpidium and Paramecium in this study, higher temperatures means individuals of each species must take up more resource to
meet their higher metabolic needs, exerting higher percapita competitive intensity upon each other. The fact
that Paramecium was competitively excluded by Colpidium at 268C suggest that stronger per-capita competitive strength of Colpidium on Paramecium more than
compensated the lower abundance of Colpidium (compared with 228C). As variation in interaction strength
may often occur in association with environmental
change, it is important that future studies take it into
consideration when predicting or explaining the responses of communities to environmental change.
In another study, Fox and Morin (2001) were also
unsuccessful in finding evidence supporting Ives and
Gilchrist’s predictions. They argued that strong density
dependence within species made it impossible to detect
any effects of interspecific interactions on species
responses to environmental change. This is not the case
in our experiments. Weak density dependence governed
Colpidium because both its growth rate and abundance
declined with temperature, and strong density dependence governed Paramecium because its growth rate but
not abundance increased with temperature. Yet it was
Paramecium not Colpidium whose response to temperature change was altered by competition. Different
temperature regimes between our and their experiments
(see Introduction) may have contributed to the differential results.
OIKOS 106:2 (2004)
It is important to note that the ciliates used in this
experiment do not possess complex life-history characteristics. All three ciliates reproduce asexually, and
populations are not structured. This simplicity allowed
us to avoid potential complications caused by complex
life-history traits, and focus on the actual effects of
species interactions. In nature, many ecosystems are
dominated by more complex organisms. These organisms often possess complex life-history traits that may
affect their response to environmental change, and these
species-level responses may further translate into responses at the community level. For example, Beisner et
al. (1996, 1997) found that temperature affected the
reproductive strategy of an invertebrate carnivore on
prey Daphnia , and increasing temperature destabilized
the predator /prey interaction and switched the system
from bottom-up to top-down trophic control. Post et al.
(1999) found that climate variation caused changes in
wolf hunting behavior, leading to community-wide
responses including changes in herbivore abundance
and primary production. Davis et al. (1998a,b) study
on Drosophila demonstrated the importance of dispersal
in species responses to environmental change. Environmental change may also alter plant resource allocation
among growth, reproduction, storage, and defense
against herbivory, affecting the outcome of herbivoreplant interactions (Ayres 1993).
Conclusions
Despite the simple life history characteristics of the
experimental organisms, our data failed in large part to
support the hypothesis that predation should lessen and
competition should magnify species’ direct response to
environmental change. Asymmetric interactions between
species and temperature-dependent interactions may
have contributed to the discrepancy between the hypothesis and the data.
Communities containing organisms with complex lifehistory characteristics may have more complex and
unexpected responses to environmental change, which
cannot be readily predicted by general models such as
those of Ives and Gilchrist (1993) and Ives (1995). Given
the complexities of ecological communities, if one were
to accurately predict the response of the species to
environmental change, more mechanistic approaches
such as individual-based models may be more appropriate (Dunham 1993, Murdoch 1993). However, individual-based models are notoriously known to be
structurally complex, data hungry, and only pertain to
the particular system being modeled. Predicting ecological consequences of environmental change remains a
serious challenge.
Acknowledgements / Tim Casey, Christina Kaunzinger, Zac
Long, Timon McPhearson, Peter Morin, Jennifer Price and
OIKOS 106:2 (2004)
Christina Steiner provided comments that improved this
manuscript. Funding was provided by US NSF grant DEB9806427 to Peter Morin and Tim Casey. Lin Jiang was
supported by Rutgers University Bevier Fellowship. Alex
Kulczycki was supported by REU supplement to US NSF
grant DEB-9806427.
References
Abrams, P. A. 2002. Will small population sizes warn us of
impending extinctions? / Am. Nat. 160: 293 /305.
Alward, R. D., Ketling, J. K. and Milchunas, D. G. 1999.
Grassland vegetation changes and nocturnal global warming. / Science 283: 229 /231.
Ayres, M. P. 1993. Plant defense, herbivory, and climate change.
/ In: Kareiva, P. M., Kingsolver, J. G. and Huey, R. B. (eds),
Biotic interactions and global change. Sinauer Associates,
pp. 75 /94.
Barber, V. A., Juday, G. P. and Finney, B. P. 2000. Reduced
growth of Alaskan white spruce in the twentieth century
from temperature-induced drought stree. / Nature 405:
668 /673.
Barry, J. P., Baxter, C. H., Sagarin, R. D. et al. 1995. Climaterelated long-term faunal changes in a California rockey
intertidal community. / Science (Washington) 267: 672 /
675.
Beebee, T. J. C. 1995. Amphibian breeding and climate.
/ Nature 374: 219 /220.
Begon, M., Townsend, C. R. and Harper, J. L. 1998. Ecology:
individuals, populations and communities. / Blackwell
Science.
Beisner, B. E., McCauley, E. and Wrona, F. J. 1996. Temperature-mediated dynamics of planktonic food chains: the effect
of an invertebrate carnivore. / Freshwater Biol. 35: 219 /
232.
Beisner, B. E., McCauley, E. and Wrona, F. J. 1997. The
influence of temperature and food chain length on plankton
predator /prey dynamics. / Can. J. Fish. Aquat. Sci. 54:
586 /595.
Bradley, N. L., Leopold, A. C., Ross, J. et al. 1999. Phenological
changes reflect climate change in Wisconsin. / Proc. Natl
Acad. Sci. USA 96: 9701 /9704.
Brown, J. H., Valone, T. J. and Curtain, C. G. 1997. Reorganization of an arid ecosystem in response to recent climate
change. / Proc. Natl Acad. Sci. USA 94: 9729 /9733.
Brown, J. L., Li, S. and Bhagabati, N. 1999. Long-term trend
toward earlier breeding in an American bird: a response to
global warming. / Proc. Natl Acad. Sci. USA 96: 5565 /
5569.
Carpenter, S. R., Frost, T. M., Kitchell, J. F. et al. 1993. Species
dynamics and global environmental change: a perspective
from ecosystem experiments. / In: Kareiva, P., Kinsolver, J.
G. and Huey, R. (eds), Biotic interactions and global
change. Sinauer Associates, pp. 267 /279.
Connell, J. H. 1983. On the prevalence and relative importance
of interspecific competition: evidence from field experiments. / Am. Nat. 122: 661 /696.
Crick, H. Q. P., Dudley, C., Glue, D. E. et al. 1997. UK birds are
laying eggs earlier. / Nature 388: 526.
Davis, A. J., Jenkins, L. S., Lawton, J. H. et al. 1998. Making
mistakes when predicting shifts in species range in response
to global warming. / Nature 391: 783 /786.
Davis, A. J., Lawton, J. H., Shorrocks, B. et al. 1998.
Individualistic species responses invalidate simple physiological models of community dynamics under global environmental change. / J. Anim. Ecol. 67: 600 /612.
Dunham, A. E. 1993. Population responses to environmental
change: operative environments, physiologically structured
models, and population dynamics. / In: Kareiva, P. M.,
223
Kingsolver, J. G. and Huey, R. B. (eds), Biotic interactions
and global change. Sinauer Associates, pp. 95 /119.
Dunn, P. O. and Winkler, D. W. 1999. Climate change has
affected the breeding date of tree swallows throughout
North America. / Proc. R. Soc. Lond., Ser. B: Biol. Sci.
266: 2487 /2490.
Elliott, J. K. and Leggett, W. C. 1996. The effect of temperature
on predation rates of a fish (Gasterosteus aculeatus ) and a
jellyfish (Aurelia aurita ) on larval capelin (Mallotus
villosus ). / Can. J. Fish. Aquat. Sci. 53: 1393 /1402.
Forchhammer, M. C., Stenseth, N. C., Post, E. et al. 1998.
Population dynamics of Norwegian red deer: densitydependence and climatic variation. / Proc. R. Soc. Lond.,
Ser. B: Biol. Sci. 265: 341 /350.
Fox, J. W. and Morin, P. J. 2001. Effects of intra- and
interspecific interactions on species responses to environmental change. / J. Anim. Ecol. 70: 80 /90.
Grabherr, G., Gottfried, M. and Pauli, H. 1994. Climate effects
on mountain plants. / Nature 369: 448.
Graham, R. W. and Grimm, E. C. 1990. Effects of global
climate change on the patterns of terrestrial biological
communities. / Trends Ecol. Evol. 5: 289 /292.
Hairston, N. G. and Kellermann, S. L. 1965. Competition
between varieties 2 and 3 of Paramecium aurelia : the
influence of temperature in a food-limited system. / Ecology
46: 134 /139.
Harrison, R. D. 2000. Repercussions of El Niño: drought causes
extinction and the breakdown of mutualism in Borneo.
/ Proc. R. Soc. Lond. Ser. B: Biol. Sci. 267: 911 /915.
Hughes, L. 2000. Biological consequences of global warming: is
the signal already apparent. / Trends Ecol. Evol. 15: 56 /61.
Inouye, D. W., Barr, B., Armitage, K. B. et al. 2000. Climate
change is affecting altitudinal migrants and hibernating
species. / Proc. Natl Acad. Sci. USA 97: 1630 /1633.
IPCC 2001. Climate change 2001: the scientific basis. / Cambridge Univ. Press.
Ives, A. R. 1995. Predicting the response of populations to
environmental change. / Ecology 76: 926 /941.
Ives, A. R. and Gilchrist, G. 1993. Climate change and
ecological interactions. / In: Kareiva, P. M., Kingsolver, J.
G. and Huey, R. B. (eds), Biotic interactions and global
change. Sinauer Associates, pp. 120 /146.
Kiesecker, J. M., Blaustein, A. R. and Belden, L. K. 2001.
Complex causes of amphibian population declines. / Nature
410: 681 /684.
Lawton, J. H. 1995. The response of insects to environmental
change. / In: Harrington, R. and Stork, N. E. (eds), Insects
in a changing environment. Academic Press, pp. 3 /26.
Lubchenco, J., Olson, A. M., Brubaker, L. B. et al. 1991. The
sustainable biosphere initiative: an ecological research
agenda. A report from the Ecological Society of America.
/ Ecology 72: 371 /412.
MacArthur, R. H. 1972. Geographical ecology. / Harper and
Row.
MacRae, I. V. and Croft, B. A. 1993. Influence of temperature
on interspecific predation and cannibalism by Metaseiulus
occidentalis and Typhlodromus pyri (Acarina: Phytoseiidae).
/ Environ. Entomol. 22: 770 /775.
McCarty, J. P. 2001. Ecological consequences of recent climate
change. / Conserv. Biol. 15: 320 /331.
Menzel, A. and Estrella, N. 2001. Plant phenological changes.
/ In: Walther, G. R., Burga, C. A. and Edwards, P. J. (eds),
224
‘‘Fingerprints’’ of climate change. Kluwer Academic/Plenum Publishers, pp. 125 /139.
Morin, P. J. 1999. Community ecology. / Blackwell Sciences.
Murdoch, W. W. 1993. Individual-based models for predicting
effects of global change. / In: Kareiva, P. M., Kingsolver, J.
G. and Huey, R. B. (eds), Biotic interactions and global
change. Sinauer Associates, pp. 147 /162.
Murdoch, W. W., Scott, M. A. and Ebsworth, P. 1984. Effects of
the general predator Notonecta (Hemiptera) upon a freshwater community. / J. Anim. Ecol. 53: 791 /808.
Myneni, R. B., Keeling, C. D., Tucker, C. J. et al. 1997.
Increased plant growth in the northern high latitudes from
1981 to 1991. / Nature 386: 698 /702.
Park, T. 1954. Experimental studies of interspecific competition.
II. Temperature, humidity, and competition in two species of
Tribolium . / Physiol. Zool. 27: 177 /238.
Parmesan, C., Ryrholm, N., Stefanescu, C. et al. 1999. Poleward
shifts in geographical ranges of butterfly species associated
with regional warming. / Nature (London) 399: 579 /583.
Phillips, D. S., Leggett, M., Wilcockson, R. et al. 1995.
Coexistence of competing species of seaweed flies: the role
of temperature. / Ecol. Entomol. 20: 65 /74.
Post, E. and Stenseth, N. C. 1999. Climatic variability, plant
phenology, and northern ungulates. / Ecology 80: 1322 /
1339.
Post, E., Peterson, R. O., Stenseth, N. C. et al. 1999. Ecosystem
consequences of wolf behavioural responses to climate.
/ Nature 401: 905 /907.
Post, E., Forchhammer, M. C., Stenseth, N. C. et al. 2001. The
timing of life-history events in a changing climate. / Proc.
R. Soc. Lond. Ser. B: Biol. Sci. 268: 15 /23.
Pounds, J. A., Fogden, M. P. L. and Campbell, J. H. 1999.
Biological response to climate change on a trophical
mountain. / Nature 398: 611 /615.
Reid, P. C., Edwards, M., Hunt, H. G. et al. 1998. Phytoplankton change in the North Atlantic. / Nature 391: 546.
Sæther, B.-E., Tufto, J., Engen, S. et al. 2000. Population
dynamical consequences of climate change for a small
temperate songbird. / Science (Washington) 287: 854 /856.
Sanford, E. 1999. Regulation of keystone predation by small
changes in ocean temperature. / Science (Washington) 283:
2095 /2097.
Schoener, T. W. 1983. Field experiments on interspecific
competition. / Am. Nat. 122: 240 /285.
Sih, A., Crowley, P., McPeek, M. et al. 1985. Predation,
competition, and prey communities: a review of field
experiments. / Annu. Rev. Ecol. Syst. 16: 269 /311.
Sturm, M., Racine, C. and Tape, K. 2001. Climate change:
increasing shrub abundance in the Arctic. / Nature 411:
546 /547.
Taniguchi, Y. and Nakano, S. 2000. Condition-specific competition: implications for the altitudinal distribution of stream
fishes. / Ecology 81: 2027 /2039.
Thomas, C. D. and Lennon, J. J. 1999. Birds extend their ranges
northwards. / Nature 399: 213.
Walther, G.-R., Burga, C. A. and Edwards, P. J. (eds). 2001.
‘‘Fingerprints’’ of climate change: adapted behaviour and
shifting species ranges. / Kluwer Academic/Plenum Publishers.
Wilson, D. S., Knollenberg, W. G. and Fudge, J. 1984. Species
packing and temperature dependent competition among
burying beetles (Silphidae, Nicrophorus). / Ecol. Entomol.
9: 205 /216.
OIKOS 106:2 (2004)