EE Lecture 11: Species and Speciation Flashcards
why do species matter
theyre fundamental unit of biodiversity important in terms of evoln, ecology,conservation
what are main types of definitions for species
- morphological species concept
- biological species concept
- phylogenetic species concept
what is the morphological species concept
species are a collection of individuals with a similar morphology that differ from other such groups
what species concept is one that states species are a collection of individuals with similar morphological traits that differ from other groups
morphological species concept
what is the biological species concept
species are a collection of individuals that can interbreed to produce fertile offspring and there is reproductive isolation from other species
what species concept is one that states species are a collection of individuals that can interbreed to produce fertile offspring
biological species concept
what is the phylogenetic species concept
species are a distinct group that share a common ancestor and can be distinguished from other such groups
give an example of a species that cant be categorized/ defined by any of the species concepts
Conodonts ~380MYA
why cant the Conodonts be defined by any species concepts
not all parts of body fossilise - only apatin mouthparts
theyre extinct - only known from their fossil record
have no known close relatives
give pros of morphological species concept
easy
adaptive traits
give cons of morphological species concept
plasticity in species - polymorphism
eg. worms in hydrothermal vents
cryptic species
purely descriptive therefore subjective
give an example of a species that defies the morphological species concept (plasticity terns)
hydrothermal vent worms show plasticity within the same species
HOT vents: short, fat, flexible white tubes
COLD DIFFUSE VENT: long skinny
initially described as 2 Ridgeia species, but now names R.piscesea
describe classification of Ridgeia piscesae species
they show plasticity dependent on which hydrothermal vent they live in
worms in hot vents are fat and short - flexible white tunes
worms in cold vents are long and skinny
they were initially described as 2 separate species, but now 1
give an example of a species that defies the morphological species concept (due to cryptic)
limpets in deep sea trenches - deep ocean exploration
multiple species with one formn
what are cryptic species
give example
one of two or more morphologically indistinguishable biological groups that are incapable of interbreeding
eg. lepetodrilid limpets in deep sea trenches
vesicomyid clams
what pros of biological species concept
key evolnary concept for sexuals
cons of biological species concept
asexuals
hybrids/ring species
hard to use in practise as need crossing experiments
give an example of species that defy the biological species concept
blue whale and fin whale two different species but can interbereed to bproduce a hybrid
outline differences between blue whale and fin whale
blue whale: darke baleen plates, large dlippers
fin whale: short snout, dark back&flanks
give an example of a ring species
Ensantina salamanders in California
what is a ring species
different species arrange themselves in a circle within their own territories, the ones directly next to eachother CAN interbreed however the ones not directly next door neighbours cant interbreed
which species concept is defied by ring species
biological species concept
what are the pros of the biological species concept
practical guide to delimitation, still based on evolnary concept and applies to asexuals
cons of phylogenetic species concept
cryptic species
taxonomic inflation - where known subspecies are raised to species as a result of a change in species concept rather than new discovery
what is taxonomic inflation
where known subspecies are raised to species due to a new description of species concept as opposed to new species discovery
how has taxonomic inflation affected primates
nearly double, mostly subspecies raised to spcies by phylogenetic species concept
what is speciation
single ancestral pop splits into two genetically distinct daughter pops
what causes speciation
- isolation
2. divergent selection
what is isolation
something that stops interbreeding between 2 parts of the ancestral pop
eg. geographic barrier to migration
what is a geographic barrier to migration causing
reproductive isolation
name examples of geographical barriers to migration
river
mountain range
habitat fragmentation
what is divergent selection
accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species to different and isolated environments which blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics
what is the accumulation of different traits between groups which can elad to the formation of a new species called
give example
divergent selection
eg. trait: beak size in finches
one for seeds one for insects
how can you test ideas about speciation
- experiments: artificial selection
- fossil record tracking
- genetic crosses
- phylogenies
what is allopatric speciation
geographic speciation occxurs when biological pops of same species become isolated
eg. marine life seperated by emergence of Isthmus of Panama ~3MYA - lots of sister species pairs - One Carribean and one PAcific
what speciation is caused when pops of same species become isolated by a reproductive barrier
allopatric speciation
give an example of allopatric isolation
species pairs when marine life separated by emergence of Isthmus of Panama ~3MYA
when did emergence of Isthmus of Panama occur
what is its significance
~3MYA
significant because it separated marine life, so now lots of sister species pairs - One Caribbean and One Pacific
what do sister species on opposite sides of the Isthmus show
allopatric speciation
- Reproductive ISolation: mainly behavioural eg.mate choice
- GEnetic Divergence based on mtDNA
- Morphological Divergence``
give genotypes of geographical isolation: allopatric speciation
AABB -> aaBB and AAbb
what happens if 2 popns separated by allopatric speciation reestablish contact
- RI has already evolved (prezygotic or postzygotic) so coexist as separate species
- Interbreed - hybridise and remain one species
- Partial isolation: selection against production of inviable hybrids leads to reinforcement of prezygotic isolation - mating preferences diverge and they coexist as separate species
what is ecological speciation
genetic divergence of pops driven by adaptation to the different (a)biotic enviros
give an example of ecological divergence
Galapagos finches
different enviros on different islands = different available foods
trophic specialisation = song differences, female preferences = RI
in terms of divergent selection and geographic isolation, where is ecological divergence
STRONG divergent selection but GEOGRAPHIC isolation @ ANY level
in terms of divergent selection and geographic isolation, where is allopatric speciation
HIGH geographic isolation and ANY divergent selection (weak to strong)
which divergence is caused from STRONG divergent selection and any geographical isolation
ECOLOGICAL speciation
which divergence is caused from HIGH geographical isolation and any (weak or strong) divergent selection
ALLOPATRIC speciation
what is parapatric divergence
extremely rare
occurs when pops are separated by an extreme change in habitat as opposed to geographical barrier
eg, mimulus copper waste
common on commonness of parapatric divergence
extremely rare
give an example of parapatric divergence
Mimulus on copper waste
M.guttatus is widespread - adj. pops on copper mine waste have evolved copper tolerance - partial gene flow, strong selection - reproductive isolatoin:hybrid lethality
there was a locus that appeared to cause copper tolerance and hybrid lethality
in terms of divergent selection and geographic isolation,what is parapatric divergence
strong divergent selection and medium geographical isolation
what type of divergence does Mimulus guttatus show
parapatric divergence
what type of divergence does Sinningia show
parapatric divergence along altitudinal gradient
S. cochlearis @ high altitudes and S.gigantifolia at low altitudes
how does ecological divergence speed up origin of reproductive isolation
- selection against intermediate hybrids reinforces prezygotic isolation eg. flower type,pollinators
- RI evolves as pleiotropic (by product of ecological divergence)
what is prezygotic reproductive isolation
mate choice
genital morphology
what is postzygotic reproductive isolation
hybrids inviable
sterile
poorly adaptive
what is sympatric speciation
process through which new species evolve from a single ancestral species while inhabiting the same geographic region
in terms of divergent selection and geographic isolation, what is sympatric speciation
low geographic isolation and strong divergent selection
in sympatric speciation, where geographic isolation is low, how does reproductive isolation originate in a popn
originates solely as a result of divergent selection
give an example of a form of sympatric isolation
host-shift speciation
what is host shift speciation a form of
sympatric speciation
what is host shift speciation
a form of sympatric speciation whereby parasite or plant-feeding insect specialised on host, few individuals shift to new host, if mating occurs within host or on natal plant, automatically leads to isolation (micro-allopatry)
adaptations to new condns drives further divergence
give an example of host-shift speciation
host race formation in maggot flies :Rhaglottis
what is host race formation in maggot flies Rhagoletis an example of
host shift speciation
what is microallopatry
occurs in host shift speciation where if mating occurs within host or on natal plant, automatically leads to isolation
discuss the host shift speciation in apple maggot fly : R.pomonella
Host shift from hawthorn to apple
adults mate on native fruit therefore inherent isolation
then divergent selection betwen hosts: apple fruit is easier than haw, hybrids maladapted to both habitas
genetic divergence between host races created allozymes
what is the controversy over sympatric speciation
its hard to show that two sister species actually formed in sympatry, present day sympatry could be secondary contact
host shifts could occur in allopatry
different races could have involved immigration from other areas eg.MExico
what are the main conclusions of ecological speciation
lots of evidence that ecological divergence drives speciation
sympatric speciation is rare
what are the best condns for speciation
strong divergent selection with some geographic isolation
what effect can a major genome change have
major genome change can spontaneously create reproductive isolation and ecological differences
give an example of a major genome change causing speciation
Louisiana irisis - created a hybrid swarm
what does hybridisation produce
ecological novelty as well as reproductive isolation