Data from: Biotic resistance to tropical ornamental invasion

We examined invasive, casual (found occasionally outside cultivation) and
non-invasive (found only in cultivation) species to investigate the role
of species traits and two forms of biotic resistance (plant neighbours and
herbivores) in limiting invasion in Hawaiian lowlands. Seeds of 21 species
of common woody ornamentals from three plant families (Acanthaceae,
Apocynaceae, Bignoniaceae) that are non-invasive, casual or invasive in
Hawai'i were outplanted at two field sites. We measured germination
of seeds and growth and survival of seedlings for one year in plots with
and without neighbours from the naturally-assembled community. The
presence of neighbours reduced survival in some species, mostly
non-invasive or casual species and completely excluded two non-invasive
species from community plots. Damage from the existing community of
herbivores was correlated with lower survival in the Acanthaceae and
Bignoniaceae, but not the Apocynaceae. Non-invasive and casual species had
lower survival and growth rates than invasive species and lower
photosynthetic rates in the presence of neighbours than invasive species.
Non-invasives without neighbours also had lower specific leaf area than
invasives and casuals. We found evidence for barriers to invasion in some
non-invasive and casual species, including low growth rate, low survival,
or low survival in the presence of neighbours. By contrast, five of the
six invasives flowered and three began setting fruit within the duration
of the experiment, as did one of the casual species. Synthesis: Our
research demonstrates biotic resistance, presumably as a result of
competition. Neighbouring plants reduced survival and growth for most
species. For non-invasive species with low survival and growth even
without competition from neighbouring plants, this resulted in complete
exclusion from community plots or such low growth rates that exclusion
over longer time frames was likely. We also provide evidence for
traits-based barriers to invasion in non-invasive and casual species.
However, no single barrier to invasion was shared across all non-invasive
and casual species.