Skip to main content
ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #276778
Title: No evolution of increased competitive ability or decreased allocation to defense in Melaleuca quinquenervia since release from natural enemies

Author
item FRANKS, STEVEN - Former ARS Employee
item Pratt, Paul
item Dray, F Allen
item SIMMS, ELLEN - University Of California

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2007
Publication Date: 8/8/2008
Citation: Franks, S.J., Pratt, P.D., Dray Jr, F.A., Simms, E.L. 2008. No evolution of increased competitive ability or decreased allocation to defense in Melaleuca quinquenervia since release from natural enemies. Biological Invasions. 10(4):455-466.

Interpretive Summary: If invasive plants are released from natural enemies in their introduced range, they may evolve decreased allocation to defense and increased growth, as predicted by the evolution of increased competitive ability (EICA) hypothesis. A field experiment using the invasive tree Melaleuca quinquenervia was conducted to test this hypothesis. Seeds were collected from 120 maternal trees: 60 in Florida (introduced range) and 60 in Australia (home range). Trees grown from these seeds were either subjected to herbivory or protected from herbivores using insecticides. Genotypes from the introduced range were initially more attractive to herbivores than genotypes from the home range, supporting EICA. However, genotypes from the introduced and home range did not differ in resistance to insects or in competitive ability, which does not support EICA. Plants from the introduced range had a lower leaf hair density, lower leaf: stem mass ratio, and a higher ratio of nerolidol: viridifloral chemotypes compared to plants from the native range. Plants with an intermediate density of leaf hairs and with high specific leaf area were more susceptible to herbivory damage, but there were no effects of leaf toughness or chemotype on presence of and damage by insects. Herbivory had a negative impact on performance of Melaleuca. Other than an initial preference by insects for introduced genotypes, there was no evidence for the evolution of decreased defense or increased competitive ability, as predicted by the EICA hypothesis. It does not appear from this study that the EICA hypothesis explains patterns of trait evolution in Melaleuca.

Technical Abstract: If invasive plants are released from natural enemies in their introduced range, they may evolve decreased allocation to defense and increased growth, as predicted by the evolution of increased competitive ability (EICA) hypothesis. A field experiment using the invasive tree Melaleuca quinquenervia was conducted to test this hypothesis. Seeds were collected from 120 maternal trees: 60 in Florida (introduced range) and 60 in Australia (home range). Trees grown from these seeds were either subjected to herbivory or protected from herbivores using insecticides. Genotypes from the introduced range were initially more attractive to herbivores than genotypes from the home range, supporting EICA. However, genotypes from the introduced and home range did not differ in resistance to insects or in competitive ability, which does not support EICA. Plants from the introduced range had a lower leaf hair density, lower leaf: stem mass ratio, and a higher ratio of nerolidol: viridifloral chemotypes compared to plants from the native range. Plants with an intermediate density of leaf hairs and with high specific leaf area were more susceptible to herbivory damage, but there were no effects of leaf toughness or chemotype on presence of and damage by insects. Herbivory had a negative impact on performance of Melaleuca. Other than an initial preference by insects for introduced genotypes, there was no evidence for the evolution of decreased defense or increased competitive ability, as predicted by the EICA hypothesis. It does not appear from this study that the EICA hypothesis explains patterns of trait evolution in Melaleuca.