What the Scientific Tropical Rainforests?” Community Can Do
search efforts, or the mobilizing of private-donor support to see the economic benefits.
Novotny et al. (Reports, 25 August 2006, p. 1115) argued
IN HIS EDITORIAL “SHOW US THE MONEY” (8
The Chicago area has benefited mightily from
that higher herbivore diversity in tropical forests resultsfrom greater phylogenetic diversity of host plants, not from
our efforts, as Atlanta has benefited from
higher host specificity. However, if host specificity is related
gests that the scientific community should tell
Emory’s efforts and Baltimore from those of
to host abundance, differences in relative host abundance
the Administration, the public, and Congress
between tropical and temperate regions may limit any gen-
what it can accomplish for our society. As
Elias Zerhouni, director of NIH, is correct
eral conclusion that herbivore diversity scales directly withhost-plant diversity.
to note that we in the research community
Full text at www.sciencemag.org/cgi/content/full/315/5819/1666b
Universities and as president of Northwestern
return on investments in NIH (“NIH in the
University, which has made large investments
post-doubling era: realities and strategies,”
RESPONSE TO COMMENT ON “Why Are There So Many Species of
last decade, especially in the life and nano
refers to scientific and health care benefits. Herbivorous Insects in Tropical Rainforests?”
expressed in job creation and multiple effects
accomplishments. A discovery in our chem-
of investment from the partnerships among
Vojtech Novotny, Pavel Drozd, Scott E. Miller,
istry labs by Richard Silverman led to the drug
the federal government, private donors, and
Miroslav Kulfan, Milan Janda, Yves Basset,
Lyrica, licensed to Pfizer, which has proved an
effective neuropathic pain reliever for tens of
Norton and Didham suggest that differences in plant abun-
thousands of patients. Many other universities
President, Northwestern University, Evanston, IL 60201,
dance between tropical and temperate forests may influ-
can also point to new therapies and diagnostics
ence the host specificity of herbivores in these forests. We
that were discovered or developed in their lab.
agree in principle but show that this is likely only for veryrare plant species in tropical forests. Studies of herbivores
TECHNICAL COMMENT ABSTRACTS
hosted by rare plant species would help our understanding
research are equally striking. One only has to
of tropical plant-insect interactions.
look at the jobs created in the construction
COMMENT ON “Why Are There So Many
Full text at www.sciencemag.org/cgi/content/full/315/
industry when we built the Robert H. Lurie
Species of Herbivorous Insects in Get daily and weekly E-alerts on the latest breaking news and research! News This Week Science ScienceNOW Weekly Alert Science Posting Notification Science Express Notification Science Express has been posted,peruse the latest table of contents
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similar to virtually all others from tropicalforests (4), did not include rare species of plants.
Apart from methodological difficulties of
sampling rare plant species for herbivores, there
There So Many Species of Herbivorous areothercomplicationsinthestudyoftheef-
fect of plant rarity on herbivores. Most insectherbivores prefer young foliage (5, 6). The
biomass of young leaves may be a better mea-sure of resource abundance than the total plantbiomass, which is mostly inedible to most of the
Vojtech Novotny,1* Pavel Drozd,2 Scott E. Miller,3 Miroslav Kulfan,4
herbivores. Low seasonality of leaf flush typical
Milan Janda,1 Yves Basset,5 George D. Weiblen6
for many trees in tropical rain forests makes thisresource available at lower densities for a longer
Norton and Didham suggest that differences in plant abundance between tropical and temperate
time, compared with young leaves produced
forests may influence the host specificity of herbivores in these forests. We agree in principle but
during a synchronized leaf flush in temperate
show that this is likely only for very rare plant species in tropical forests. Studies of herbivores
forests. Young foliage in the nonseasonal tropics
hosted by rare plant species would help our understanding of tropical plant-insect interactions.
thus supports more herbivore generations, butpossibly at lower population sizes, than similarly
NortonandDidham(1)arguethatdiffer- tropical forest, including forests we studied abundantbutseasonalresourcesinthetemperate
Extremely rare plant species are expected to
The plant species with extremely high or low
the general conclusion that herbivore diversity
host fewer specialists, and herbivore species
densities may also be unusual in other aspects
scales directly with host plant diversity. They
overall, as they represent a rare and scattered
of their ecology. For instance, monodominant
point out that our study (2) did not include
resource difficult to use by herbivores. How-
forests offer an opportunity to study tropical
locally rare tree species. Our temperate/tropical
ever, it is not known what resource abundance
herbivores feeding on exceptionally common
comparison was standardized for sample size
is limiting for herbivorous insects. Specialized
tree species (7). However, these forests exist
and plant phylogeny but not for plant abundance
herbivores may be few in communities coloniz-
only in low-nutrient environments, such as
and, indeed, there are more rare tree species in
ing rare plants with unpredictable distribution in
sandy or swampy soils, which can also influence
space and time, such as annual herbaceous
the quality of plant resources for herbivores.
species limited to brief, early stages of ecolog-
This is probably why the diversity of insect her-
Institute of Entomology, Czech Academy of Sciences, and
Department of Zoology, University of South Bohemia,
ical succession after unpredictable disturbance
bivores in these forests is low (8) and why they
Branisovska 31, 370 05 Ceske Budejovice, Czech Republic.
events (3). It is less clear what represents
are not exceptionally host specific, contrary to
2Department of Biology, University of Ostrava, Chittussiho
extreme rarity for herbivores from large peren-
expectations for an abundant resource (9).
10, 710 00 Ostrava, Czech Republic. 3Smithsonian Institu-
nial plants, such as trees. Our study suggests
The impact of plant abundance on herbivo-
tion, Washington, DC 20013–7012, USA. 4Department of
Zoology, Comenius University, Mlynska dolina B-1, 842 15
that there is no impact of plant abundance on
rous insects depends also on the colonization
Bratislava, Slovakia. 5Smithsonian Tropical Research In-
the species richness or the host specificity of
ability of the insects, which varies among
stitute, Apartado 0843-03092, Balboa, Ancon, Panama. 6
their leaf-chewing communities for plant abun-
species and clades. For instance, aphids are
Department of Plant Biology, University of Minnesota, 220
dance characterized by the basal area from 0.01
inefficient colonizers, which may explain their
Biological Sciences Center, 1445 Gortner Avenue, St. Paul,MN 55108–1095, USA.
to 10 m2/ha (Fig. 1, B and C). This range included
low diversity in tropical forests (10), whereas
117 out of the 151 plant species from 1 ha of the
Lepidoptera typically disperse hundreds of
*To whom correspondence should be addressed. E-mail:[email protected]
tropical forests (Fig. 1A). However, our study,
meters to several kilometers in their lifetime,
Fig. 1. The abundance of woody genera in temperate and tropical forests
and the average number of host plant species of these herbivore species are
(A), and the relationship of plant abundance with species richness (B) and
shown for two sets of 14 tree species from respectively temperate and tropical
host specificity (C) of their folivorous herbivores. Plant abundance, expressed
forests (2). There is no correlation between the plant basal area and either of
as basal area, that is, the combined area of the cross-section of all conspecific
the herbivore variables in any of the two types of the forest (Pearson r, P >
trees at 1.5 m above the ground, was estimated in 1-ha plots in the
0.1, both for the correlation using plant species as independent data points
temperate (dots) and tropical (circles) forests at the study sites used by
and for the independent contrasts analysis, taking into account statistical
Novotny et al. (2, 14). The number of folivorous species per 100 m2 of foliage
nonindependence of tree species due to their shared phylogeny).
www.sciencemag.org SCIENCE VOL 315 23 MARCH 2007
although data from tropical forests are rare
herbivore will be important and interesting, but
9. Y. Basset, N. D. Springate, E. Charles, in Tropical Forests
(11). Good dispersal ability of many tropical
of the Guiana Shield: Ancient Forests in a Modern World,D. S. Hammond, Ed. (CABI Publishing, Wallingford, UK,
folivores is suggested also by their rapid colo-
nization of pioneer trees recently established at
10. A. F. G. Dixon, P. Kindlmann, J. Leps, J. Holman, Am. Nat.
disturbed sites (12) and of isolated plants in the
1. D. A. Norton, R. K. Didham, Science 315, 1666 (2007);
www.sciencemag.org/cgi/content/full/315/5819/1666b.
11. I. Hanski, Metapopulation Ecology (Oxford Univ. Press,
2. V. Novotny et al., Science 313, 1115 (2006).
3. V. Novotny, Oikos 70, 223 (1994).
12. J. Leps, V. Novotny, Y. Basset, J. Ecol. 89, 186 (2001).
tant, but for its technical difficulty so far ne-
4. V. Novotny, Y. Basset, Proc. R. Soc. London Biol. Sci.
13. C. D. Thomas, Ecology 71, 610 (1990).
glected, problem—namely, the effect of plant
14. V. Novotny et al., Cons. Biol. 18, 227 (2004).
5. Y. Basset, Ecology 77, 1906 (1996).
rarity on the composition and ecology of her-
6. L. Cizek, Eur. J. Entomol. 102, 675 (2005).
bivore communities in tropical forests. Finding
7. T. B. Hart, Trends Ecol. Evol. 5, 6 (1990).
23 January 2007; accepted 27 February 2007
what represents a rare species to a tropical insect
8. D. H. Janzen, Biotropica 6, 69 (1974).
23 MARCH 2007 VOL 315 SCIENCE www.sciencemag.org
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What the Scientific
similar to virtually all others from tropicalforests (4), did not include rare species of plants.