Transcript Abundance, Diversity, & Invasive Species

Plant Ecology - Chapter 13
Abundance, Rarity, Invasives
Abundant vs. Rare - Why?
Some plants are
common in many
areas, and have
widespread
distribution
Others are rare, and
have restricted
range
Abundant vs. Rare - Why?
Common plants may
be dominating
competitors
E.g., removal of
goldenrod increases
species richness,
allows less
competitive species
to survive
Abundant vs. Rare - Why?
Common plants may
be dominant, but not
strong competitors
E.g., orchard grass
often dominant in old
fields, but removal
may affect few other
plant species
Abundant vs. Rare - Why?
Rare species may be
ecological specialists
Tend to have low
abundances, small
geographic ranges
Minnesota dwarf trout
lily
Abundant vs. Rare - Why?
Other causes of rarity
might be:
Lack of dispersal
Historical
accident
Abundant vs. Rare - Why?
One combination produces commonness, all
other combinations produce some form of rarity
Abundance Curves
Few common species, many rare species
Invasive Species
Species that are
rapidly expanding
outside of their
native range
Usually exotics from
from their native
habitats
Invasive Species
What makes a plant
potentially invasive?
Reproduction at
younger ages
Smaller seeds
Large seed crops
produced at shorter
intervals
Invasive Species
Invasive Species
“Tens Rule” on the success of invaders
1 in 10 plants brought into a region will
escape into the wild
1 in 10 escapees will become
naturalized and self-sustaining
1 in 10 of these naturalized species will
become invasive
Communities Susceptible to
Invasion
Original ideas:
disturbed
communities and
species-poor
communities more
vulnerable to
invasion
Communities Susceptible to
Invasion
Disturbance may
hinder invasions,
and invasive
species often more
common in speciesrich communities
Communities Susceptible to
Invasion
Nutrient-poor soils
more resistant to
invasive species
Invasives do well in
absence of native
herbivores,
pathogens (e.g.,
bladder campion)
Abundance and Community
Structure
Species richness
may change as
community
productivity
changes, but no
clear pattern
Adaptation,
competition, growth
rates, other
explanations
More individuals, more
species?
Greater
environmental
heterogeneity
(space and time),
more niches, more
potential
specialization, more
species
Disturbance vs. Diversity?
Intermediate disturbance hypothesis species diversity should be highest at
intermediate levels of disturbance
Species
richness
Disturbance frequency
Disturbance vs. Diversity?
No relationship
between
disturbance and
diversity is the most
common
observation
Only 16% of studies
show “expected”
pattern
Diversity Concerns
Will reduction in plant species diversity
(failure to conserve species adequately)
lead to decrease in primary
productivity?
Potential to reverberate through food
chain, leading to extinctions of
consumers.
Diversity Concerns
Are more diverse plant communities
less stable, or less likely to return to
their original state after disturbance?
Do more diverse communities have less
year-to-year variation in productivity
than less diverse communities?