Novel weapons testing: are invasive plants more chemically defended than native plants?
BACKGROUND
Exotic species have been hypothesized to successfully invade new habitats by virtue of possessing novel biochemistry that repels native enemies. Despite the pivotal long-term consequences of invasion for native food-webs, to date there are no experimental studies examining directly whether exotic plants are any more or less biochemically deterrent than native plants to native herbivores.


RESULTS
In a direct test of this hypothesis using herbivore feeding assays with chemical extracts from 19 invasive plants and 21 co-occurring native plants, we show that invasive plant biochemistry is no more deterrent (on average) to a native generalist herbivore than extracts from native plants. There was no relationship between extract deterrence and length of time since introduction, suggesting that time has not mitigated putative biochemical novelty. Moreover, the least deterrent plant extracts were from the most abundant species in the field, a pattern that held for both native and exotic plants. Analysis of chemical deterrence in context with morphological defenses and growth-related traits showed that native and exotic plants had similar trade-offs among traits.


CONCLUSIONS
Overall, our results suggest that particular invasive species may possess deterrent secondary chemistry, but it does not appear to be a general pattern resulting from evolutionary mismatches between exotic plants and native herbivores. Thus, fundamentally similar processes may promote the ecological success of both native and exotic species.
Lind
Eric M
EM
Smithsonian Environmental Research Center, Edgewater, Maryland, United States of America. linde@si.edu
Parker
John D
JD
D000818:Animals; D044822:Biodiversity; D007814:Larva / Q000502:physiology; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry; D018521:Plant Physiological Phenomena; D010944:Plants / Q000737:chemistry* / Q000235:genetics; D019655:Quantitative Trait, Heritable; D013045:Species Specificity; D013997:Time Factors; D014197:Trees
Proc Natl Acad Sci U S A. 2009 Oct 27;106(43):18097-102
19841257
J Nat Prod. 1999 Jan;62(1):2-4
9917274
Nature. 2003 Feb 6;421(6923):625-7
12571594
Science. 2006 Mar 10;311(5766):1459-61
16527979
Oecologia. 1999 Nov;121(2):183-192
28308558
Ecology. 1987 Dec;68(6):1567-1580
29357161
J Chem Ecol. 2005 Nov;31(11):2541-50
16273427
Ecol Lett. 2009 Feb;12(2):107-17
19143824
Trends Plant Sci. 2006 Dec;11(12):574-80
17092763
Q Rev Biol. 2006 Dec;81(4):349-76
17240728
Ecol Lett. 2009 Aug;12(8):765-71
19392715
J Insect Physiol. 2002 Jun;48(6):655-665
12770076
Oecologia. 2003 Mar;134(4):471-8
12647118
Am Nat. 2002 Apr;159(4):396-419
18707424
Oecologia. 1997 Mar;110(1):99-108
28307474
Ecol Lett. 2005 Sep;8(9):959-967
34517680
Ecol Appl. 2006 Aug;16(4):1367-76
16937804
New Phytol. 2007;176(3):635-643
17822409
Ann Bot. 2003 Aug;92(2):215-22
12805082
Oecologia. 1998 Dec;117(4):449-459
28307669
Am Nat. 2002 Dec;160(6):712-26
18707460
Am J Bot. 2007 Apr;94(4):526-32
21636422
Bioinformatics. 2008 Sep 15;24(18):2098-100
18678590
Biol Lett. 2006 Jun 22;2(2):189-93
17148359
PLoS One. 2009;4(3):e4796
19274098
Nature. 2003 Feb 6;421(6923):628-30
12571595