Ecology in action: invasion Flashcards
why are islands good for research?
small, simple, isolated, bounded, defined area of study
what can you analyse on islands?
natural selection, ecological organisation, ecological development, impact of global change
Christmas Island
tropical ‘high’ (not sandy) island
high plateaus and terrace edge
uninhabited until 1888
deep ocean - never been connected ti another land mass (organisms crossed through water)
island rainforest
75% or 100km squared
diversity is low but abundance is high
more tree species on plateau
crabs
red crab
1 crab per square m in rainforest
omnivores
60 million
is the crab a strong regulator of the forest?
more seedlings where crabs are excluded
reproduction of crabs
lay eggs in sea and are fertilised by males in spring (Nov, Dec)
baby crabs come back to land on spring tides (Jan)
attack of yellow crazy ant
unintentional introduction
in 1990s they formed super colonies
generalised nesting habitats- can nest anywhere
eat anything high and low
comparisons between invaded and uninvaded areas
ants kill crabs - leaf litter and seedlings build up
15-20 mill (1/3) diead
ants have mutualitic relationship with scale insects (protect for honey dew) which harms trees
- honey dew drips from trees so sooty mould grows on trees
- canopy opens up and light so there are more seedlings
thrushes do behaviours to avoid ants so less reproductive behaviours
- no successful nests in invaded areas
- eat more in uninvaded areas
solutions
scope island of ants
23% of waypoints had super colonies
fishmeal granular brain with fipronil as active ingredient - non-target impacts?
99.4% reduction of ands in areas baited
biological control
wasp kills scaly insect, less food for ants
- crab numbers are increasing!
comparisons in the study
compare invaded and non-invaded areas. mo manipulation of variables
