Many members of the Melastomataceae have a propensity to become
invasive, given the opportunity. This opportunity rarely arises
in the native habitat of a species as there tends to be a higher
rate of competition from other natives. Additionally, in a plants'
home range, there are usually numerous pathogens from herbivores
to fungi and viruses that have co-evolved with the plant keeping
populations in check. These external ecological factors and organisms
make it very unlikely that a species will develop 'invasive' behavior
in its native range or create extensive monodominant stands.
The basic reason for the invasive behavior exhibited by some melastomes
is that they are primary colonizers of secondary areas, disturbed
habitats, pastures, roadsides, landslides, light gaps and rivers.
As such, their life strategies include such adaptations as high
germination rates, rapid growth, early maturity, ability of fragments
to root, apomixis and efficient seed dispersal - frequently employing
birds that are attracted by copious production of berries.
Most of these qualities are present in Miconia calvescens
and Clidemia hirta; this had led to their incredible proliferation
throughout Hawaii, the Pacific Islands, and beyond.
was introduced to Hawaii and Tahiti and is now considered to be
one of the greatest threats to the fragile ecosystems of the islands.
In Tahiti, M. calvescens was first planted as an ornamental
at a private botanical garden in 1937; it can now be found on
approximately 70% of the island. The species is fast growing,
shade tolerant, devoid of natural pests, and sets an abundance
of seed with a high rate of germination leading to monospecific
stands - M. calvescens easily out-competes and has put
the native flora at great risk.
The spread of Clidemia
hirta throughout the Pacific islands has followed a similar
pattern. Like Miconia calvescens, when growing outside
of its native habitats of the Caribbean, Central and South America,
C. hirta often forms nearly impenetrable thickets. It has
had a devastating effect upon the native flora of Hawaii and many
Pacific islands where it is free to grow and spread in a variety
of habitats without impediments. Biological control of this invasive
species has met with limited success.