Earth Diversity Flashcards
Lecture 1 & 2 - Allan
What is a community?
an assemblage of many interacting populations of different species occurring together in space and time
how are communities established?
The presence of species in the community depends on abiotic factors.
What is community ecology?
study of members of a multispecies assemblage interacting with each other and their surroundings; the ecology of
biodiversity.
Why are some species associated with some communities and not others? - turn over
Interaction networks
Tell us how strongly species interact with each other.
Gives you some idea of the richness of the population in the community.
How many species are there on Earth?
1.5Mil species catelogued.
but around a 10% error due to taxonomic uncertainty.
Diversity in unevenly distributed between phyla.
HOw do determine the estimate total species diversity?
What is species diversity?
WHat is species richness?
the number of species in a community.
The relative abundance of species in the community.
Who came up with the relative abundance?
Robert whitaker.
Lognormal distribution
Low evenness
Why do we care about the relative abundance?
- Population density
- Habitat specificty
- Range size.
Species richness (S)
After you have sampled, you can draw curves.
Rarefaction curve (grey one) - shows the individual based
Species accumulation curve (black one)
old growth vs secondary growth example. Slide 10 lecture 2.
when we try to compare species richness confidence to the … that’s why we use a rarefaction curve.
Chao1 asymptotic species richness estimator.
Sest=Sobs+a2/2b
a=number of species that only occur once in the sample,
b=species that occur twice
need to be thinking about the fact that species are always unevenly distributed and how that affects our ability to estimate them.
Species diversity/ evenness component.
Metric combining species richness and relative abundance.
2 communities with the same amount of species - one with low evenness and one with high evenness.
High evenness have more communities of higher diversity.
Species diversity indicies
Diversity metrics are not linearly scales
NB - give priority to the dominant species in the community.
What is true diversity?
Effective number of species.
NUmber of equally abundant species that would give the observed diversity metric .
True diversity = 2^H
Spatial organization of biodiversity.
species-area relationship
(i) sampling of more individuals,
(ii) spatial habitat heterogeneity,
(iii) immigration-extinction dynamics
(iv) Evolutionary effects
Dimensions of diversity
a diversity - local diversity
β diversity - turnover between communities (like different landscapes/habitats)
y diversity - regional diversity
β diversity = γ diversity / α diversity
The effective number of unique communities in the region
Spatial organization of biodiversity
β diversity = species compositional turnover
between communities
community similarity coefficients:
Based on the similarity of species composition between the two communities:
Jaccard coefficient
Sorenson coefficient
= These coefficients do not take relative abundance into account.
Horn index
Morisita-Horn indices
= These account for relative abundance
Global diversity of distribution?
Correlations around the poles.
Species near the poles
What are deterministic explanations of the land-sea diversity rule?
- Land is more productive - can sustain more species, but that is not always the case. The ocean can be more productive.
- More difficult movement in the water - water is not an easy medium to move through, higher species abundances in the ocean.
- Greater habitat heterogeneity on land - not necessarily that marine systems are less heterogeneous.
What are the evolutionary explanations of the land-sea diversity rule?
- More geographic isolation on land
- Reduced dispersal on land
- speciation/extinction
- Time - the more time the system has been stable, the more likely new species will arise in the system
- Rates of transition between habitats
- Diversification within habitats - increased geographic isolation between terrestrial environments and reduced dispersal ability, but the ocean is also separated by landmasses. Species disperse over longer distances in the ocean.
What is a global diversity hotspot
High richness and relatively high evenness..
What is the latitudinal gradient of diversity?
Lecture 3 sllide 10
Latitudinal gradients of species diversity in deep-sea isopods, gastropods,
and bivalves from the North Atlantic and Norwegian Sea
Holds for virtually all taxonomic groups
(except aquatic macrophytes, parasites)
Has existed for 250 my at least
graphs
2 kinds of explanations:
1. Local determinism = how many species you can pack into a community
2. Evolutionary explanations
What is the mid-domain effect?
no underlying biology, more likely to have more than 1 species overlap in the middle if there is a start and end point. But its unrealistic.
What is the area theory ?
The relationship between climate area and species richness
What is the species-energy theory?
develop predictions of species’ abundances and probabilities of occurrence on an island.
What is the Physiological tolerance
hypothesis?
higher regions provide climates that are extreme, so only a few species have adaptions and restrict the number of species that can exist there. more tropic climates, organisms don’t have many adaptions.
What is the spatial heterogeneity theory?
the uneven distribution of various concentrations of each species within an area.
What is the competition theory?
declining inequality among regions (or groups) promotes competitive conflict among race and ethnic groups
What is the enemies theory?
What is the time/stability theory?
Tropics have more stable environments than in the polar areas = more stable species in the tropic areas.
What is the tropical conservatism hypothesis?
Most species have come out of the tropics and colonized more temperate areas. evolving adaptations necessary to survive more temperate environments. temperate adaptions are derived.
What is the evolutionary speed theory?
speed up the evolutionary process over latitudes due to change in temperatures.
lecutre 3 slide 22 nb
