3 - Global diversity patterns Flashcards
Land sea diversity rule deterministic explanations
- Land more productive
- More difficult movement in water
- Greater habitat heterogeneity on land
Heterogeneity
the quality or state of being diverse in character or content
Land sea diversity rule evolutionary explanations
- More geographic isolation on land
- Reduced dispersal on land
- speciation / extinction
- Time
- Rates of transition between habitats
- Diversification within habitats
Speciation
When a group within a species separates from other members of its species and develops its own unique characteristics
Biodiversity hotspot
Regions that contain a high level of species diversity, many endemic species (species not found anywhere else in the world) and a significant number of threatened or endangered species.
Biodiversity hotspots around the world
- Madagascar - world’s second-largest island after Indonesia and is over 150 million years old
- Brazil’s Atlantic Forest Region
- The California Floristic Province
- South Africa’s Cape Floristic Region
- The Philippines
- Thailand
- The Tropical Andes
The latitudinal gradient of diversity
- Richness increase at equator
- Richness increases at low elevation, depth or aridity
- Richness increase with an increase in topographic complexity
Mid-domain effect
The hypothesis states that if the ranges of the species are randomly distributed within a bounded domain then more ranges will overlap near the middle of the domain than at the edges, and thus decreasing species richness will be observed from the mid-domain to the edges.
Area theory
Larger habitat areas hold more species than smaller ones.
As one extends the sampled area, the total recorded species increases at a diminishing rate.
The latitudinal gradient of diversity – the earth’s structure
- Mid-domain effect
- Area theory
The latitudinal gradient of diversity – abiotic
- Species-energy theory
- Physiological tolerance
hypothesis
The latitudinal gradient of diversity – biotic
- spatial heterogeneity theory
- competition theory
- enemies theory
Species-energy theory
If energy has a causal relationship with richness, then species-energy theory implies that energy causes richness to increase in low-energy areas, energy has little effect in intermediate-energy areas, and energy depresses richness in the highest-energy areas.
Physiological tolerance
hypothesis
Proposes that plant species richness is highest in warm and/or wet climates because a wider range of functional strategies can persist under such conditions.
spatial heterogeneity theory
It refers to the uneven distribution of various concentrations of each species within an area.
competition theory
Competition is a relationship between organisms that strive for the same resources in the same place.
Intraspecific competition occurs between members of the same species. It improves the species’ adaptations.
Interspecific competition occurs between members of different species.
enemies theory
- The Enemy release hypothesis is the idea that invasive species are less impacted by enemies (e.g., herbivores) than native species, because in the new geographical location, the invasives species are freed from the parasites that kept their growth in check in their native environment.
-Predicts a positive correlation between plant species richness and natural enemy abundance, which results in the regulation of herbivores at lower levels in diverse vegetation than in pure stands.
Intraspecific competition
occurs between members of the same species. It improves the species’ adaptations.
Interspecific competition
Occurs between members of different species.
The latitudinal gradient of diversity – evolutionary
- time/stability theory
- tropical conservatism hypothesis
- evolutionary
speed theory
Time/stability theory
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tropical conservatism hypothesis (TCH)
tries to explain the generally observed latitudinal gradient of increasing species diversity towards the tropics.
evolutionary speed theory (ESH)
Proposes a causal mechanism for the latitudinal diversity gradient — warmer temperatures lead to shorter generation times and increased mutation rates.
Dimensions of diversity (local vs regional diversity patterns)
- Scale
- Grain
- Latitudinal range
- Global richness
- Dispersal mode
- Body mass
- Thermoregulation
- Trophic level
- Longitude
- Hemisphere
- Realm
