macroecology and conservation principles Flashcards
(50 cards)
1
Q
key features of macroecology
A
- large spatial scale
- strong empirical observational approach
- emergent non-reductionist approach
2
Q
what is range size
A
the geographical distribution of a species
- is scale dependant
- more species have small range sizes
3
Q
how to measure range size
A
- extent of occurrence
- locate every time a species is seen within a boundary - area of occupancy
- found the area of occupied locations within a boundary
4
Q
relationship between range size and abundance
A
- positive relationship
- therefore small populations have an increase probability of extinction
5
Q
what is Rapoport’s rule
A
species at high latitudes have large geographical ranges and species found in low latitudes have smaller ranges
- positive relationship between latitude and geographical distribution
6
Q
mechanisms for Rapoport’s rule
A
- climate tolerances
- historical factors
7
Q
climate tolerances - Rapoport’s rule
A
- seasonal variation greatest at high latitudes
- therfore species here are adapted to cope with a range of tempertaures
- high lat species are physiographically capable of ocurring in a wide range of enrvionmenst
8
Q
historical factors - Rapoports rule
A
- high latitudes have lots of glaciation events
- these cause species extinction and species with smaller geographic ranges are more vulnearble to extinctions
- thereofer more small range species to extict at high latitudes - thereofre range size smaller here
9
Q
climate variability hypothesis
A
taxa from enviornmnetally variable habitats evolve with wider environmnetal tolerances - therefore have wider distributions along climate gradients then taxa originating from stable habitats
10
Q
altitudinal range sizes - climate variability hypothesis
A
- species with grater climatic tolerances should occur at greater altitudinal range sizes
- empirically proven to have a positive correlation
11
Q
factors that limit species distribution
A
- climate tolerances
- biotic factors e.g. food supply
12
Q
importance of islands
A
- natures labs
- inspiration for evolution
- good for study as they are surrounded by a contrasting habitat (sea) so its acts as a barrier against species
13
Q
what do islands represent
A
- 5% land area
- 80% recorded extinctions
-40% of endangered species
14
Q
why do large islands have more species
A
- more area = more habitat diversity = more niches = less competitive exclusion
- more area = larger population = reduced extinction rate = more species
- less likely to be severely impacted by extreme events
- extinction curve will be flatter because of this as it is a buffer
15
Q
relationship between area of an island and number of species
A
- positive
- non linear
- steeper at beginning then levels off
- modelled by Olof Arrhenius
- roughly 10x increase in area = 2x species richness
16
Q
saturation by isolation
A
- measures number of species on an island relative to the number of possibel species that could occure (given the pool on the nearest mainland)
- more distant islands are therefore less saturated as its harder for species to colonise them
17
Q
island biogeography theory
A
- thought that the habitat area relationship was incomplete
assumptions: - species must arrive on island
- speices must persiist on island
- species richness in a balance of imigration and extinction
18
Q
immigration - IBT
A
- on an island with few species most colonising individuals will be from unrepresented species which have high immigration rates
- on an island with many species individuals that arrive will be from a species already present and immigration rates of this species are low
19
Q
extinction - IBT
A
- island with no species has no extinction
- on an island with many species by chance there is some local extinction and increased interspecific competition reduced population sizes so species extinction rates increase
20
Q
equilibrium prediction - IBT
A
- the number of speices on an island will eventailly reach an equilibrium and then the number of speices will reamin relatively constant
- BUT speices composition is dynamic - new speices will arrive and replace other species by driving then to extincting from outcompeting them
21
Q
Krakatoa
A
- natural experiment to test equilibrium theory as a volcanic eruption killed all biota
- number of species returning was counted over time
- data showed that the rate of accumulation of species slows down as the number of species present increases
22
Q
limitations of IBT
A
- slopes of extinctin and immigration curves not know and could vary between islands
- islands may not be in equilibrium
- extinction and immigration vary among species
- extinction and immigration rates are not separate - rescue effect (high immigration rates save species from extinction)
- multiple immigration routes and rates e.g. between islands
- assumes no speciation on islands
23
Q
what is the latitudinal diversity gradient
A
the closer to the tropics you are the greater variety there is
24
Q
alpha diversity
A
number of species found in a location
25
beta diversity
change in composition between 2 locations or the same location over time
26
is the LDG real
on the basis of widespread evidence - yes
has existed for millions of years in some taxa
27
what causes the LDG
1. speciation vs extinction
2. immigration vs emigration
27
what influences the LDG
- chance events
- ecological factors
- evolutionary factors
28
theories based on chance events
1. land availability
- if species are randomly distributed through space, its expected more species in locations with more land area
2. mid domain models
- is species are randomly distributed across an area, there should be increased overlap of species towards the centre
29
theories based on energy/productivity
- places with more energy availability should have higher species richness
30
why are there more species instead a greater number of the same species
- more energy in an area allows more individuals to randomly occur
- larger populations have reduced extinction risk
- more energy at the base of a food chain can support more trophic levels
- more energy enables a population to recover faster from disturbances
- higher energy environments have more niches
- reduced niche breadth reduced competition exclusions as species can have their preferred resource
31
evolutionary hypotheses for the LDG
1. cradles - tropics home to new speices
- high rates of speciation
- tropics are diverse
2. museums - tropics home to old species
- low rates of extinctions
- tropics are diverse
3. engines - species originate in tropics then spread to other regions
- high speciation, low extinction
32
evidence for the LDG
1. fossils
- created a record through time
- cradles - in 5/6 species they fist occurred in tropics
- museums - last 6 million years extinction rates lowest in tropics
2. phylogenies
- used to date the birth and death of taxa
33
why do the tropics have higher diversification rates
1. mutation rates higher - high temp and UV
2. more opportunities and niches
3. Climate stability
34
lapse rate
- air cools 3C/300m (saturated) and 1.5C/300m (dry)
- as the air cools it condenses = precipitation on windward side and dry on leeward side
35
diurnal climatic variation
0-1100m = lowland rainforest
1100-1800m = montane forest
1800-3200m = giant heath forest
3200-5000m = alfro-alpine zone
5000+ = nival zone
36
diversity of amazon basin
- alpha diversity highest in world = 942 plant species in 1ha
- biologically impoverished in invertebrates
37
global diversity of montane regions
- montane regions have higher beta diversity than amazon
- because they have a range in climate
- mountains hotspots for biodiversity (especially tropical ones)
38
why is allopatric speciation lower in mountainous regions than the tropics
the tropics have narrower physiological tolerances with no overlap = increased cost to dispersal over a climate gradient = low gene flow = high allopatric speciation
opposite for mountainous regions
39
landscape scale speciation
- quaternary climatic shifts lead to periods of isolation of biota on mountain tops = more allopatric speciation
- inversion layer refugia - small valleys at high elevations have caps of cold air that can trap stable warm air for long periods = isolated area with high speciation as species cannot move through valleys
40
local scale speciation
- temp decrease with elevation = lower species richness
- negative correlation between SR and elevation
- however this depends on the taxonomical group
41
Preston's canonical log distribution
- if data for abundance is plotted on a 2 log scale histogram a normal bell shaped curve is produced
- no of species (Y) vs log 2 abundance (X)
42
Simpsons diversity index
- 0 (no diversity) to 1 (infinite diversity)
43
Shannon-Weiner diversity index
- expresses the probability that 2 individuals that are drawn randomly from a community will belong to the same species
- 0-1
44
rank abundance distributions
- good for assessing the community structure (species richness and evenness)
- gradient of line shows how even a species abundance is
- captures changes over time
45
range size relationships
- relationship between how big a species geographical range is and how big their abundance is
- larger range size = high abundance
46
niche breadth/ Browns hypothesis
- positive correlation between large range and high abundance because of wide niche breadth so lots of different resources at one side that can tolerate lots of different environments
47
population dynamics
- species with higher r occupy more patches therefore have larger ranges
48
abundance and conservation
should areas that are hotspots for rare species by focus areas for conservation?
49
what is a rare species
- small geographic range size
- small population size
- habitat specialist (can only occupy one specific habitat type)
- some species are naturally rare - this is not a bad thing and humans should not try to increase their population
