So in conclusion, what can we say about Abiotic factors,
especially climate?
(1) Abiotic factors influence species’ distribution and abundance
But it also –
(2) Shapes organisms: morphology, physiology, and behavior
But, we can ask: “Are most organisms always found where
their abiotic needs are met”?
We’d expect no Arboretums
We’d expect no zoos
We’d expect no Invasive spp
Dispersal limited
While abiotic factors represent a filter for what can exist at a given time
and in a given space, BIOTIC factors play a pivotal role (another filter)
on what does exist
Balanus and Chthamalus show zonation in tidal habitats
Joseph Connell 1961
Experimental
- caged predators
- removed competitors
- transplanted rocks
w/barnacles
- monitored responses
Always
exposed
Always
submerged
Conclusions of Connell’s study
(1) Organisms are limited by abiotic conditions that set ‘hard’ limits
on their distribution (for barnacles it’s the upper tidal zone).
(2) Organisms are also limited in their distribution by the biotic
components of their environment (competitors, predators) that
may set ‘softer’ limits (esp. Chthamalus – competition).
(3) Removal of biotic factors can result in expansion in the
distribution an organism – its geographic range, range of habitats
where it occurs (Connell’s study), abiotic conditions in which its
found, and so on…
‘hard’ = absolute
‘soft’ = dependent on the presence of another organism
Let’s synthesize the material so far in the
Concept of the NICHE
Let’s consider the concept of niche –
If I knew what it meant I’d be rich.
Its dimensions are n
But a knowledge of Zen
Is required to fathom the bitch
- Grant Cottam and David Parkhust
The environmental factors that influence the growth, survival,
and reproduction of a species – Molles Textbook
Functional role of a species in the community, including activities
and relationships – Smith and Smith Textbook
The environmental factors that influence the growth, survival,
and reproduction of a species – Molles Textbook
Species have requirements (water, temp, food, mates, etc…)
Species have impacts (they eat things, i.e., deplete resources,
they build things, they destroy things, etc…)
Functional role of a species in the community, including activities
and relationships – Smith and Smith Textbook
Figure 22.9
A single Niche axis
Abundance
min
max
Temp
Two Niche axes
Abundance
min
max
min
min
max
Temp
min
max
max
Water
Two Niche axes with interactions between variables
Abundance
min
max
min
min
max
Temp
min
max
max
Water
min
max
Temp
min
max
Water
min
max
Temp
Water
PH
Three Niche axes
PH
min
max
Temp
min
max
Water
min
max
A multi-dimensional mess!!
Hutchinson’s n-dimensional niche
min
max
Calcium
PH
min
max
Temp
min
max
Water
The niche can be visualized, conceptually, as an n-dimensional volume
that defines all the conditions in which an organism can survive
min
max
Calcium
min
PH
max
More definitions:
The Fundamental Niche is the total niche volume determined solely
by Abiotic factors
The Realized Niche is a subset of the F. Niche that an organism
actually occupies – the difference being the influence of Biotic factors:
e.g., predators, competitors, food
The Niche concept place in a Population Framework
The environmental factors that influence the growth, survival,
and reproduction of a species – Molles Textbook
Realized Niche
R0 < 1.0
predation
R0 > 1.0
competition
Factor One
Factor Two
Fundamental Niche