Tropical Diversity Flashcards
Early History
Alfred Russel Wallace:
- Early explorer of the Indo-West pacific.
- Independently theorized on evolution by natural selection.
Alex Van Humboldt:
- First to formally recognize the latitudinal diversity gradient
Biodiversity in the tropics
Highest here
Ecological hypotheses:
- Area, species coexistence, niche partitioning and temperature affects
Evolutionary hypotheses
- Rates of speciation/extinction
- Dispersal into/out tropics
Historical hypotheses:
- Age of the tropics vs temperate regions
Interactions between all
Tropics
Geographic, Region between the most N and S latitude in which the summer can be seen directly overhead during summer/winter solstices
Climatological, various definitions based on temp, precipitation and other climate variables.
Biogeographic, edges of tropics located where geographic ranges of species found primarily within low lats come into contact with those primarily found with higher latitudes.
Dispersion barriers
Tropical mountain passes stronger than equivalent temperate zones
Little seasonality in tropics, mountain appears higher.
Larval development, higher temperatures increase speed of larval development.
Less time for dispersal so go shorter distances.
Over evolutionary time scales
Warm temps limit dispersal and gene flow
Islands are harder to colonize in the tropics
Facilitating conditions for all allopatric speciation and coexistence.
Cradle or museum
Low extinction rates in the tropics, museum
Tropics have little spatial and seasonal variation in SST.
This affects the size of species geographic range
Tropical bivalves tend to have broad latitudinal ranges.
Large range > low extinction rate
large range size should mean more individuals and populations, more reproduction
This leads to more dispersal between populations. Thus if one population goes locally extinct, then dispersal from surrounding populations can re-colonise these areas.
Large range size/ more individual populations which correlates with higher genetic diversity and lower rates of inbreeding which reduces extinction risk.
