Macroecology Flashcards
What is Macroecology?
studying relationships between organisms and their environments at larger spatial scale that involves characterizing and explaining patterns of species abundance, distribution and diversity
What kind of approach for Macroecology take?
- top-down
- focuses on understanding the properties of an ecosystem rather than individuals
What is Biogeography
the study of variation in species composition and diversity among geographic locations
Global scale
rates of speciation, extinction, long distance dispersal
Regional Scale
- climate is roughly uniform, dispersal important
- regional species pool (gamma diversity)
landscape scale
- physical geography of a region
- landscape connectivity shapes immigration and emigration
- beta diversity: change in species diversity and composition (turnover) from one community to another
Local Scale (i.e., community)
- competition, predation, species interaction
- alpha diversity: local diversity at a site
What is Ecological Niche Modelling?
attempt to predict species geographic distribution ranges, including expansion and retractions based on information of species current distribution and niche requirements, and spatial information
How is niche modelling predictive?
combine species’ niche requirements with spatial distribution of environmental conditions on a landscape to identify specific locations where species could occur
How to assess a species fundamental niche?
need to grow/raise the species along along an environmental gradient, in controlled experiments
What two types of Data do you need for ENM?
- info on the realized niche of the species of concern (environmental data, climate, geographic sites, etc.)
- need to know the distribution of environmental factors in the range (climate, geological data, remote sensing data)
Example of ENM (crabs)
- predicting the spread of an invasive crab species through NA
- native to east asia
- spread across the planet by hitchhiking in ballast water of trade ships
Herborg et al. used data on distribution of crab it its native range to model areas of suitable habitat
Limitations of ENM
- focuses on realized niches
- harder to model rare species bc we will have few observations from which to gather environmental data
What are some other applications of ENM?
- can be used to direct researchers to areas in which rare species may be found
- can predict species movements/extinctions/immigrations under future environmental conditions
In which areas are broader patterns of diversity across large geographic scales explored?
- island biogeography
- latitudinal gradients in species richness
island biogeography
relationships between the size of a given geographic area, isolation and overall diversity
What is considered an island?
any portion of isolated habitat
What kinds of patterns are found on islands?
- species richness increases with island area
- species richness decreases with island isolation - distance from mainland and/or other islands
Why is there a relationship between area and species richness?
larger areas likely have more resources, can support larger populations, less vulnerable to extinction, and have greater niche diversity
What mechanisms might increase species richness on large islands while reducing richness on small, isolated islands?
species richness on islands can be modelled as a dynamic balance between immigration and extinction of species
Rate of Immigration
rate of arrival of new species on the island
- highest on new islands because every species is new, this rate declines as speculate accumulate, until all possible species are present
Rate of extinction
- more species creates bigger pool of possible extinctions
- as number of species increases, population size of each likely to decrease
- as the number of species on island increases, potential for competitive interactions will increase
What does the point of equilibrium represent
- predicted number of species for an island
- immigration and extinction rates are equal
- species composition can turn over but species number remains constant
What is turnover and where is it the highest and lowest?
- turnover is change in species composition
- is highest on islands that are small (high extinction) but near the mainland (high immigration)
- lowest on large islands (low extinction) and far from mainland (low immigration)
In terms of Latitude, where does species richness increase?
from middle and high latitudes towards the equator
Why are the tropics more diverse? (three hypotheses)
- species diversification rate is higher in the tropics
- diversification rates are similar, but evolutionary time is greater in the tropics
- higher productivity results in more abundant resources in the tropics that can support more species
Species diversification rate
- the tropics have the most land area on Earth, and temp is very stable
- large, thermally stable areas should decrease extinction rates - population sizes and geographic ranges would be larger
- speciation by geographic isolation woudl be more likely
Species Diversification time
- the tropics have been more climatically stable over time
- 65 mya entire earth was warm
- then during the Pleistocene glaciers disrupted the land that now makes up the temperate zone
- life that is currently at the temperate zone is much younger than that at the tropics
productivity
- terrestrial productivity is highest in the tropics
- high productivity promotes large population sizes bc carrying capacity is larger
