Species and Niche Flashcards
name the 7 problems with species definitions
1) parthenogenesis
2) apoximis
3) widely distributed species
4) polyploids
5) hybridisation is effectively separated species
6) natural hybridisation
7) polymorphism
describe parthenogenesis
a natural form of asexual reproduction where fertilisation of the egg is not required to develop an embryo and individual.
mostly female offspring, but one individual could found a whole new population
(Moritz 1991)
describe apoximis
the ability of some plants to produce seeds and offspring without fertilisation e.g. blackberries (Amsellem et al 2001)
describe how polyploids interfere with species definitions
cells contain multiple sets of chromosomes, but are technically same species. BUT infertile offspring between diploids and polyploids of same speccies
describe ‘ring species’
species distributed over such large areas that individuals from opposite ends may vary considerably – races are formed, and only neighbouring races may interbreed – genetic isolation through geographical distance
give 2 examples of ring species
greenish warbler has a ring around the himalayas
Larus gulls have a ring around the north pole (Wake, 2001)
how is hybridisation between effectively separated species an issue to the species concept
Individuals of populations (which may already look and behave quite differently) may be able to successfully breed, but will never (hardly ever) do so under natural conditions e.g. tiger+lion=liger/tigon
e.g. geese.
which 3 factors create issues for the field identification of species
hybridisation
(e.g. orchids)
polymorphism
(e.g. many strawberry poison frog morphs)
polymorphism
(sexual dimorphism in mallards and tanzanian butterflies (keilland 1990))
(seasonal dimorphism in map butterflies)
define fundamental niche
the full range of resources an organism requires to replace itself
define realised niche
that part of the fundamental niche an organism occupies in the field
why is there a difference between the realised and fundamental niche?
organisms are best able to compete in their optimal growth conditions, so interspecific competition is there
(ellenberg et al 1992)
when are organisms most competitive
optimal growth conditions
example of spatial resource partitioning for niche differentiation
root systems of european herbs occupying different depths
Kutschera and Lichtenegger (1992)
how do species coexist
niche differentiation - using the same environment is a different way, usually through spatial or temporal partitioning
which disturbances could be exploited for temporal partitioning in niche differentiation
falling trees gaps clearings fire trampling
how is nutrient level affected by clearing forests
wood is harvested, removing nutrients from the ecosystem
how is nutrient level affected by fire?
fires lead to a sudden nutrient flash, which is washed away at the next rain, leaving very poor nutrient levels
3 examples of fire being used in niche differentiation
fire on mt Kilimanjaro has enabled sub-alpine forests to be replaced by bushes. These burn and are replaced by other bush species
seed capsules in Australian pyrophytes only open when a fire occurs
seed pots in a different australian pyrophyte only opens after a fire
what will happen if coexisting species don’t differentiate into niches
If there is no differentiation, or it is precluded by the habitat, then one competing species will eliminate or exclude the other.
what is the biological species concept?
Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
what is the phylogenetic species concept
a species is defined as the smallest set of organisms that share common ancestors and can be distinguished / are isolated from other such sets.
who coined the biological species concept? when?
(Mayr 1942).
what is allopatric speciation
a barrier forms between a population, with different environmental conditions on the other side, and no more gene flow.
example of allopatric speciation
squirrels on either side of the grand canyon
