15 - Species Diversity Flashcards
the number of species increases from ____ to ____ latitudes
high
low
low prey diversity promotes ____ population dynamics
unstable
less species redundancy ____ ecosystem resilience
lowers
more species redundancy _____ ecosystem resilience
increases
this latitudinal gradient includes what animals?
mammals, land birds, ants, butterflies, marine coastal fish, marine bivalves, copepods, snakes, almost universal
species richness may also vary with what other factors?
longitude, elevation, depth, topography, aridity
what hypotheses exist regarding the latitudinal gradient?
history spatial heterogeneity competition predation productivity environmental stability disturbance
describe the history/time hypothesis
Support?
Argument??
topical habitats are older TF more stable and less disturbed.
had time for adaptation and speciation
Support: geological past of boreal less constant that tropics. All communities diversity with time
Argument: as glaciers moved in, species moved south to escape. This hyp cannot be tested
describe the spatial heterogeneity hypothesis
higher diversity in tropics bc of increase in # of potential habitats
decrease in envr complexity moving away from equator
the more heterogenous and complex the physical envr, the more diverse the plant and animal communities
describe the competition hyp
less competition in boreal envr compared to tropics
northern pop regulated by extreme envr conditions, not biological factors. in tropics, pop’s increase to densities where comp for resources is necessary
sources of mortality are abiotic
high competition results in higher rates of speciation
alpha diversity
overall species richness
beta diversity
number of unique species in diff habitats
where is alpha and beta diversity highest why?
tropics
organisms more specialized to habitats
ex of competition leading to speciation?
darwin’s finches
comp for food led to specialized beak morphology (feeding specialization)
describe predation hypothesis
increase species in tropics in function of increased number of predators that regulate the prey species
decrease comp among prey species
allows co-existence of prey species and potential for new
stronger selective pressure on avoiding predation than becoming better competitors
describe the cropping principle
what hyp is this under?
predation increases diversity by reducing intraspecific competition among prey species
example of cropping principle
presence of herbivores creates more niches for plants
under cropping principle, what happens if predators are removed?
prey start competing –> one/few may dominate
two species competing for the same limiting resources cannot exist
What law??
Gause’s law of competitive exclusion
effect on community disproportionate to their abundance
keystone predator
describe cropping principle in lakes
top predators feed on zooplankton
if TP removed, community diversity decreases. Dominated by a few species of large grazing zooplankton
add fish, diversity of small zooplankton and their invert predators increase
describe mesopredator release?
why hyp is this under?
apex predators affect diversity as well as abundance of lower trophic levels
predation hypothesis
describe the productivity hyp
tropics support a greater number of species bc of more resources
*increased production leads to increased diversity
what are the exceptions to the productivity hyp?
marshes
desert
TF there is a correlation between productivity and vertebrate biodiversity
False
environmental stability hypothesis
constant climate –> finer specialization and adaptations, shallower niches
don’t have to deal with such a large amount of envr changes
disturbance hypothesis
if community disturbance freq is high –> local extinction –> decrease in species diversity
if very low –> competitive exclusion by dominant species –> decrease in species diversity
ECOLOGICAL TIME SCALE
intermediate disturbance will maximize diversity and lead to patches at local scale
what are some limitations of all these hypotheses?
circular (based on the assumption of greater diversity in tropics), some no supported by sufficient evidence (no consistent correlation btwn species diversity and envr stability, productivity, physical heterogeneity
role of ice-age extinctions
slow speciation and colonization after glaciations
role of polar harshness
high extinction rates, slow population growth
role of tropical climatic stability
low extinction rates allow specialization and speciation
role of tropical productivity
greater evenness, narrow niches
role of structural heterogeneity
finer niche subdivision, microclimate heterogeneity
role of interspecific interactions
competition, predation, and mutualism promote specialization
TF primitive species are not abundant in the arctic
F - they ARE particularly abundant
–> think about plants
Rapoport’s rule
taxa have larger ranges in polar regions
provide 2 examples of “super dominant” species that are generally plastic
willow
lemmings
____ ____ is the environmental variable that best predicts plant diversity in the arctic
summer temperature
in general, what is expected to happen with a warming climate?
species diversity should increase
what species are most vulnerable?
those that are most abundant in the northernmost part of the tundra or polar deserts
best adapted to climate conditions of high arctic where more competitive species are absent
TF/ southern limits of turn see less specialization among microhabitats
False, greater
what determines the northern borders of the geographic distribution of most animals?
temperatures lower than the species-specific tolerance limits
what determines the southern borders of the geographic distribution of terrestrial arctic animals
biotic factors –> competitors and natural enemies
T/F high temps determine the southern border of terrestrial arctic animals
F
why is biodiversity important in the arctic
there is little functional redundancy among species in the arctic and species redundancy enhances ecosystem resilience
what are the two types of research?
fundamental research
- understand generally how the world works
applied research
- solve problems
- conservation/management and such
why is northern research important
rate of change may be more important than its magnitude
science of change is easier to study in the arctic
