Speciation i Flashcards
What are the different species definition classifications?
- Phenetic
- Biological
- Ecological
- Phylogenetic
- Unified Species Concept
What type of entity is a species?
Discrete
Species are produced from a
Continuous process
A species is a
Fundamental unit of biodiversity
Evolution might be defined as
Completion of a speciation process
Phenetic species
A set of organisms that are phenotypically similar to one another and different from other sets (Sokal & Crovello 1970)
Biological species concept
Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other groups (Mayr 1942)
Ecological species concept
A lineage (or closely related set of lineages), which occupies an adaptive zone minimally different from that of any other linage in its structure ange and which evolves separately from all lineages outside its range (Van Valen, 1976)
Phylogenetic species concept
Distinct group that shares a common ancestor, distinguished from other groups (Cracraft, 1983)
Describe the Moa species (Bunce et al, 2003)
- ratites; flightless birds
- thought to be 3 species of Dinornis based on morphology: D. giganteus, D. novaezealandiae, D. struthoides
- using genetic data, found to be one species on each island, with extreme size dimorphism (F > M) and habitat linked size variation
What is species plasticity?
When one species has multiple forms
Give an example of a plastic species (Vrijenhoek 2009)
Deep sea vent tubeworms
Describe the species plasticity of deep sea vent tubeworms (Vrijenhoek, 2009)
- short fat worms -> flexible tubes at hot vents
- long skinny worms at cool vents
- found adjacent
Describe the initial misclassification of deep sea vent tubeworms
- originally Ridgeia piscesae and R. phaeophiale
- actually plastic morphs of R. piscesae
How are deep sea tubeworms plastic? (Vrijenhoek 2009)
Developmentally plastic larvae sense conditions
What are cryptic species?
Multiple species that look alike - have “one” form
Give an example of a cryptic species set (Janzen et al, 2017)
- neotropical skipper Udranomia kikkawai in Costa Rica
- whole genome sequencing revealed 3 species
Pros of phonetic species concept
- practical: relatively easy to observe and measure
- applicable to all taxa
Cons of phenetic species concept
- issues for plastic traits, cryptic species, polymorphisms
- purely descriptive, relying on human interpretation, doesn’t incorporate evolutionary concept
What is the evolutionary concept
Why species should be different
Give some pre-mating isolating mechanisms
1) temporal
2) ecological
3) behavioural
4) mechanical
Give some post-mating isolating mechanisms
1) zygote mortality
2) hybrid inviability
3) hybrid sterility
4) hybrid breakdown
Give an example of behavioural reproductive isolation
- western meadowlark Sternella magna
- Eastern meadowlark Sternella neglecta
- changing vocalisation
What is the name of the hybrid between a female horse and a male donkey?
Mule
Give the name of the hybrid between a female donkey and a male horse
Hinny
Cons of the biological species concept
- breeding experiments not feasible
- allopatric forms
- cannot be easily applied to asexually reproducing organisms or fossilised species
What pizzlies (or grolars)
polar-grizzly bear hybrids occurring because of climate change induced range changes
Describe a coywolf
Coyote-wolf hybrids occur in nature
Describe ligers
Lion-tiger hybrids bred in zoos
Describe a ring species
- encircles a geographic barrier
- populations around the ring exchange genes, except where the ring meets: reproductive isolation
- during expansion, adjacent populations exchange genes, but exchange attenuates with distance
Give an example of a geographic barrier that might result in a ring species
Mountain range
Requirements for a ring species
- founded by one population
- one of the terminal populations must be the most recent range expansion
- no geographic barriers to interrupt gene flow now or in the past
- must show isolation by distance
Give 2 examples of ring species
1) Ensatina eschscholtzii salamander in western North America
2) Phylloscopus trochiloides greenish warbler complex in Asia
Molecular evidence reveals sharp genetic breaks consistent with geographic isolation
Ring species under the biological species concept
Terminal populations look like separate species, even though reproductive isolation not seen in other adjacent areas
Give examples of some asexually reproducing organisms
- bdelloid rotifers
- brine shrimp
- New Zealand mud snail
- New Mexico whip tail
- zebra shark
Give pros of the biological species concept
- mechanism-based concept
- key concept for sexual organisms
Monophyly
A group consisting of an ancestor and all of its descendants
The phylogenetic species concept focuses on
Evolutionary relationships among organisms
Pros of phylogenetic species concept
- practical guide to delimitation
- based on evolutionary concept
- can be applied to asexual and fossilised organisms
Phylogenetic relationships reflect
Evolutionary history
Cons of phylogenetic species concept
- needs a highly resolved phylogenetic tree
- can result in taxonomic inflation
What is it essential to do when utilising the ecological species concept
Identify adaptive zones a priori
Pros of the ecological speciation concept
- applies to sexual and asexual forms
- allows for some gene flow among groups as long as they maintain ecological differences
- abiotic “adaptive zones” are relatively easy to measure
Cons of the ecological speciation concept
- assumes the existence of ecologically discrete niches
- assumes organisms are independent of their niche
Ecologically discrete niches and the
Gaps between them
Niche construction
Organisms can change their environment
Which species concept would an evolutionary ecology be most likely to use
Biological species concept
Which species concept would a palaeontologist be most likely to use?
- phonetic species concept
- morphological differences important
Which species concept would a systematist be most likely to use?
- Phylogenetic species concept
- has diagnosability
Under all species concepts, a species is a
Separately evolving meta population lineage
How might be define the Biological Species Concept under the Unified Species Concept?
Separately evolving meta population lineage is hat also has to be intrinsically reproductively isolated from other lineages
How might be define the Phylogenetic Species Concept under the Unified Species Concept?
Separately evolving meta population lineage that also has to be monophyletic
Why are strictly defined species concept incompatible? (de Queiros Syst Biol 2007)
- Speciation is a continuos process that creates discrete entities
- different criteria may be achieved at different times
What does the Unified Species Concept do?
Used contingent properties as lines of evidence for assessing the separation of lineages, and to recognise different types of species based on the properties they possess
What is speciation essentially?
The introduction of a species boundary
What causes species formation?
Microevolutionary processes
Speciation is a
Process, rather than an event
A species is the
Outcome of speciation
Describe the sexual dimorphism of Moa
Females could be up to 280% larger than males
Species plasticity - differences arise from
Plastic effects, rather than genetic events
Explain habitat-based pre-mating isolation
Habitat preferences
Explain mechanical pre-mating isolation
Physically can’t mate
Describe post-mating isolation
- non-viable zygote
- reduced survival and reduced fecundity
Isolation by distance is a
- genetic concept
- closer species are more genetically similar
The BSC can be
Pre- or post-zygotic
PSC
Very definitive
How are fossil cladograms built?
Morphological data
For a highly resolved cladogram, you need
Taxon sampling to be excellent
Meta-population
Inclusive population made up of sub-populations
