19 pages covering all 12 lectures on biodiversity and conservation. Covers things such as latitudinal gradients of species richness, drivers of biodiversity loss and using butterflies as indicators of environmental change. Definitions are highlighted throughout.
Biodiversity: variety + variability of life on earth
➔ Prioritise conservation efforts
➔ Simplest measure = species richness: number of species in an area nhyi;
Latitudinal gradient of species richness:
Increasing number of species in each taxonomic group from poles to tropics
- Except bats
- Harder to collect data on marine biodiversity patterns -> experience smaller change in
species richness
Poles = Antarctica, Arctic/alpine, Tropics = temperate deciduous forests, temperate grasslands
Low latitude = tropics high latitude = poles
Reverse Latitudinal Patterns:
1. Seabirds: greatest abundance + diversity at high latitudes
2. Lichens: mx diversity in cold regions of boreal forest
3. Microbes = cosmopolitan: live everywhere -> not restricted by geographical barriers
Control of Latitudinal Gradients Hypotheses:
1. Geographical Area Hypothesis: larger surface area in tropics = more species than poles
2. Energy-Species Hypothesis: resource availability + climate -> allows co-existing species
• More energy in tropics = can be used by more organisms
• AET = Annual Evapotranspiration AET > PET
• PET = Potential Evapotranspiration: sum of evaporation + plant transpiration from
earth’s land
• Increasing latitude decreases PET
• decreasing solar radiation decreases PET
a. Productivity Hypothesis: availability of resources dictates number of co-existing
species in an area
More major resources = solar energy + nutrients -> higher plant biomass ->
herbivores -> carnivores
b. Ambient Energy Hypothesis: availability of high temperatures dictates number of co-
existing species in an area
• Low temperature reduces population growth + lowers survival
• Water, temperature, rainfall = limiting factors
• Diversity often declines when resources added to community -> Paradox of
Enrichment: dominant species outcompetes + excludes other species ->
reduces diversity
o Examples: algal blooms in aquatic environments due to
eutrophication, N fertilisation reduces diversity in plant communities
3. Heterogeneity Hypothesis: general increase in environmental heterogeneity towards tropics
Heterogeneity: diversity in habitats
Disproven:
o Only takes place in amphibians
o Latitudinal biodiversity patterns in sea even though there is little heterogeneity
variation
4. Rapoport’s Rule: geographical range of species decreases poles -> tropics
, Low latitudes: narrow range of environmental tolerance
Niche packing: few species with narrow niches
High latitudes: wide range of environmental tolerance
3 Explanations:
a. Climatic variability: greater variability at high latitudes -> more diverse
b. Glaciation: species with high dispersal ability populate north -> wide range
c. Interspecific Competition:
i. Tropics = restricted habitat = more competition = smaller niches + fine
adaptations
ii. Poles = limited by environmental factors = less competition = broader niches
5. Evolutionary Speed Hypothesis: tropics = stable for long time -> allows faster evolution rate
3 traits character
a. Long evolutionary history -> more populations
b. Lack of glaciations -> stable existence of populations
c. Constant warm temperatures
L2 – Measuring Biodiversity
Measures of biodiversity:
1. Species Richness = Alpha Diversity:
= number of species + number of endemic species in each area
2. Species Composition = Beta Diversity:
Compares similarity + differences between areas
Change in species composition between places = opposite of Jaccard Index
3. Phylogenetic Diversity:
How related species in an area are to each other
Find areas with more unique species
Longer branches in phylogenetic tree = higher phylogenetic diversity = more distantly related
4. Functional Diversity:
Diversity in species traits related to function in a community
Elements of biodiversity which influence how ecosystem functions
Hotspots of Species Diversity:
Biodiversity hotspot: geographical location with high species richness
Considering areas of conservation -> overlapping species richness, endemic + threatened species
richness, species agreement
Complementary Approach: conserving as much biodiversity as possible in a limited area of land
available
Uses Jaccard Similarity Index
➔ Higher Simpson index = more even species richness -> higher conservation priority
Ecosystem function: all species have function/dynamics/interactions e.g. stocks of materials, rates of
processes, energy fluxes between trophic levels
➔ Positively related to species richness
Ecosystem service: provides things to humans = life possible + worth living
, 2 species have same function -> one can be removed without affecting ecosystem = lowers species
richness + not functionality
Ecosystem service = functional diversity + ecosystem functioning
L3 – Causes of Local Biodiversity
Regulation of Local Diversity: enable coexistence
1) Equilibrium Theories: evolution + competition develops into stable state
a. Niche Concept: specialisation enables more species to coexist in an area
Different species used different resources -> don’t compete
Tropic community = many species with narrow niches -> resources don’t overlap
Temperate community = species with broad niches -> resources overlap -> increased
competition
b. Heterogeneity Concept: more diverse habitats have more niches
e.g. as tree height increases = more space for insects, plants, birds = tree biodiversity
increases
Problems:
- Mainly followed by animals -> plants compete for same resources
- Resources + conditions not partitioned into discrete packages/niches
- Doesn’t account for most of biodiversity
c. Island Biogeography Theory: Macarthur + Wilson
Central paradigm of island biogeography = determined by extinction + migration
• Discrete, quantified, numerous + bounded communities
Species diversity in oceanic island = island area + distance to mainland
➔ Maximum species richness = when 2 forces overlap = extinction+ immigration =regulated by
area + isolation
- Mainland = Large area = can support larger populations
- Island = Small area = more genetic similarities = more likely to go extinct
• Area -> extinction
• Isolation -> immigration
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