W10 limits on geographic distributions wrap up Flashcards
what are the 3 primary factors that limit species ranges?
- physical and chemical factors (eg. we focused on temperature, moisture and salt)
- dispersal
- other species
what is dispersal? what what challenges does studying this field (dispersal) encounter? give an example of which species was tracked and how?
an ecological process that involves the movement of species away from the population in which they were born to another location. or population, where they will settle and reproduce
a challenge with studying dispersal is that it is hard to track.
- that the geographic distribution of most species is rarely well characterized, so many dispersal events go unnoticed
example: salamanders
- within the geographical region, there are different coloured dots representing something different: one is for after and before, one is for before, one is for after.
- sufficient observation power is easier to track dispersal
what is a striking invasive species example of dispersal? and what re the 3 factors that are affected by this invasive species dispersal?
zebra mussels lays up to 1million eggs each breeding season and after the eggs are fertilized, the larvae are free-swimming (able to move in a certain direction) for a month. They were spreading all across US altering food webs by removing native species’ food sources such as plankton where they can remove food by filter feeding plankton creating clear water.
When it creates a clearer water is allows sunlight to penetrate deeper increasing the growth of submerged aquatic vegetation which leads to toxic algal blooms considering the zebra mussels don’t feed on toxic algae. This increase of toxic algae increases pathogenic bacteria, avian botulism, and localized anoxia.
Also affecting fish spawning areas by changing important substrates which impacts the survival of fish eggs. They were successful and a concern to native ecosystem.
zooplankton that feed on phytoplankton are being declined
what are the 3 modes of dispersal? give an example for all three
note: there are 2 examples for one of them
- jump dispersal
- the movement of individuals across large distances followed by the successful establishment of a population in the new area, usually over unsuitable habitat (e.g. colonization of island or other patches of habitat)
- ex: zebra mussel distribution which had a rapid spread (but also failed to colonize the central US) - diffusion
- gradual movement of populations over favourable terrain
- ex: cane toads in australia were first introduced (jump dispersal) but then became a diffusion dispersal. There was a gradual spread of Cane Toads across Australia, driven in part by the movement of longer-legged individuals which this evolving trait helped them spread more rapidly into new territories.
- ex2: sea otters in california were not an invasive species but were hunted to almost extinction. once the hunting pressure was relaxed their population expanded and dispersed new establishment of the population along the coast - secular dispersal
- more of a evolutionary view point: diffusion taking place so slowly that the diffusing species undergoes appreciable evolutionary change during the process.
- these species experience natural evolution or natural selection in these new environments as it’s moving. the geographic range expands over geologic time where at the same time, natural selection causes migrants to diverge from the ancestral population.
- ex: camelids (camels and llama) are a family of species that evolved and diversified during a secular migration process over many thousands of years. today there are 7 species in the family camelidae who moved both south and north and asia and africa
what is the time frame in which this form of dispersal, jump dispersal, occurs?
a short-time during the life of an individual
how is island colonization achieved?
by jump dispersal, and human introductions such as the zebra mussel introduction, can often be viewed as an assisted form of jump dispersal
whats the time frame which diffusion dispersal occurs?
dispersal occurs over time period of generations
whats the time frame which secular dispersal occurs?
tens-hundreds of generations timescale
how does dispersal influence range expansion? what paradox is associated with this question?
If we imagine a population where all the individuals disperse, then reproduce, and then die and that this population is placed into a large area of suitable vacant habitat, the population will advance its range as individuals disperse.
reid’s paradox: Reid’s Paradox of Rapid Plant Migration or Reid’s Paradox, describes the observation from the paleoecological record that plant ranges shifted northward, after the last glacial maximum, at a faster rate than the seed dispersal rates commonly occur
what was reid’s question?
how did the British Isles become recolonized with vegetation after the glaciation?
what explains Reid’s paradox how it occurs “at a faster rate than the seed dispersal rates commonly occur”?
reid’s paradox: found that seeds were not dispersed through dispersal themselves by extreme dispersal events
- long-distance events are difficult to record and measure
Even though the mean dispersal distance is small, colonization rates are driven not by the mean dispersal distance but by extreme dispersal events
- A few seeds are blown by wind or moved by animals a long distance from the parent tree
- thereby difficult to record and measure
does dispersal limitation generally limit range size? what is a factor
look at the life cycle: many animals have a life stage that is highly mobile, they mobilize themselves
e.g., Marine Pelagic fishes spawning in the water column with highly mobile larvae Many spiders are light enough to be blown on the wind Many Insects are obviously highly mobile
explain how dispersal and colonization occurs rapidly at a local scale after the huge eruption that wiped out a large area wiping most lives.
scientist followed the recolonization of different islands following this event and after 1 year they found a spider and after 3 years algae and so on the number of population grew.
the plants were quick to recolonize and the species followed that recolonization having the food and habitat which they quickly found it. so birds colonization of the islands depended on vegetation colonization and the flora of the islands has continued to increase
- majority of the plants and animals were probably transported by wind where the larger vertebrates probably arrives on driftwood rafts or in a few cases by swimming.
so dispersal may be limiting for species that have not yet arrived but overall we see species that are able to disperse rapidly
- When there is vacant space, animals and plants are not long in finding it. The role of dispersal in limiting distributions may often be dependent on local conditions (including biotic interactions)
- one thing for sure for a;; will see that dispersal and world limiting of dispersal may not be working alone and have biotic and abiotic factors working along
what are the two reasons why other species limit distributions? (why one might limit another’s distribution?)
negative interactions with other organisms (eg. predation, disease, competition) or lack of positive interactions such as mutualism or symbiosis
predation limits the local distribution of some species. what are the 4 criterias that must be met to conclude that a predator is restricting the distribution of its prey?
1) Prey will survive if transplanted outside to an area where they
don’t occur if they are protected from predators
2) The distributions of prey and (suspected) predator are inversely
correlated
3) The (suspected) predator is able to kill the prey
4) The (suspected) predator is shown to be responsible for killing the prey in transplant experiments
