Lecture 9: Species + Lecture 10: Phylogenetics Flashcards
Why did early researchers doubt evolution?
natural selection, genetic drift, mutation, and migration were seen as sources of microevolution not macroevolution (speciation)
main definitions of species
taxonomic and biological
sympatric
same area
allopatric
different area
taxonomic/morphological species concept
based on distinct morphological differences
Is there a universal species concept?
No, nothing encompasses all species.
What did Darwin think of species?
Darwin was not clear on what he thought species were. He talked about species and “varieties”. Thought that species were arbitrary labels humans gave animals and plants to satisfy our own need to categorize and we based it off how they looked (taxonomic).
Who was Ernst Mayr? (1904-2005)
approached the “species problem”. Said that a species was not only a group of organisms that are morphologically similar, but a group that can exclusively interbreed.
What happens on islands?
rapid genetic reorganization due to geographic isolation
Biological Species Concept
Based on the inter fertility of populations, focuses on the process of speciation and how it occurs. Says that a species is a group of individuals that exclusively interbreed in the WILD. States that geographic isolation alone is not enough.
What does the BSC not apply to?
Bacteria, asexuals (would identify each individual as their own species), highly self-fertilizing species, or fossils.
Where can reproductive isolation occur?
Pre-mating isolation (finding a compatible mating, mating and fertilization) and post-mating isolation (development or zygote, adult growth and survival, reproduction and fertility of offspring).
Example of pre mating isolation
- Change in host plant. Any number of things could cause pre mating isolation as soon as one small change occurs, it causes a cascade of reinforcements for speciation.
- Changes in behaviour leads to changes in sexual preference of even determine whether members of a species interact.
What factors can prevent zygote formation?
geographical, ecological, temporal, behavioural, mechanical, prevention of gamete fusion
Apple Maggot flies
Arrival of domesticated apples in 19th century led to host plant shift from hawthorn to apple. Change in host plant resulted in speciation (sympatric) because mating occurred at different times and on different part of the plant. Hawthorns and apples fruit at different times so there is temporal separation. Apple and hawthorn maggot flies are physically indistinguishable but have different genetic profiles. Gene flow is approx. 6% (they can hybridize fine).
Abalone
Binding of sperm lysin to egg vitelline envelope receptor (VERL) required for fertilization. Lysin/VERL interaction has coevolved in different directions in different species causing reproductive isolation.
What factors can prevent the proper functioning of zygotes once they are formed?
Inviability, sterility, or abnormal development of hybrids. Genes don’t work well together. Cannot be favoured by natural selection because the gene combo can’t be passed on.
intrinsic post mating isolation
Sterility or lethality ex. mules cannot self sustain a population
extrinsic post mating isolation
Poorly adapted hybrids ex. two butterflies A and B mate and hybrid has aberrant colour patterns making it more likely to get eaten (predation risk lowers mating success).
What causes adaptive radiations?
- origin of a key innovation (a novel trait)
- ecological opportunity (abundant resources and few competitors often on oceanic islands or aquatic counterparts like African rift lakes)
- high rate of speciation characterize the clade (some species are more likely to radiate ex. Darwin’s finches and the honeycreepers radiated on mainland also whereas Galapagos mockingbirds radiated neither on islands or continents )
polyploidy
an organism, tissue, or cell with more than two complete sets of homologous chromosomes (includes autopolyploidy and allopolyploidy)
Are humans haploid or diploid?
Trick question—we have both. Our somatic cells are diploid and gametes are haploid. The sex cells only contain 1 copy of an allele, while the body cells have two copies (maternal and paternal). If we got a full set from both parents we would be polyploids.
Why are polyploids reproductively isolated from parents?
They have more chromosomes than diploid parents and this cannot interbreed.
Even though polyploidism is a relatively low probability event…
approximately half of flowering plants are of polyploid origin (including many crops and invasive species).
Few characteristics of polyploids
- Permanent heterozygosity = fit hybrid, meaning they survive (in allopolyploids)
- exhibit new phenotypes thus can exploit new environments and niches
Carolus Linnaeus (1707-1778)
father of taxonomy, binomial nomenclature (genus species), predictive hierarchal pattern of classification
Linnaeus’ system
kingdom, phyla, classes, order, family, genera, species
king Philip came over for good soup
monophyletic group
also called clade, a complete set of species that evolved from a common ancestor
paraphyletic group
group that contains some but not all species derived from common ancestor (ingroup) the other species are part of outgroup
outgroup
A less closely related species in a monophyletic group used as a reference point to determine evolutionary relationship between an in group (a group of more closely related species in the clade)
Nodes in a evolutionary tree
represent speciation event
taxon
taxonomic group of any rank (species, family, class, etc)
ancestral trait
trait shared with common ancestor
derived trait
trait that differs from ancestral trait in lineage
homology
similarity of traits due to shared ancestry (fish and human skeletons are homologous structures, bird and bat wings are analogous)
homoplasy
similarity of traits as a result of convergent evolution. Can trick biologists when just examining morphological structure. We must also look to molecular biology to differentiate
features associated with greater diversification
- herbivory (as plants evolve, so do animals because od coevolution)
- species with more sexual selection (showy displays can make pre mating barriers emerge as different females have different preferences)
- animal pollination
- increased dispersal
- increased size range
ecological speciation
evolution of local adaptation (where organism adapts tp their environment) as a result of divergent selection can lead to reproductive isolation and eventually maybe speciation
“Speciation genes”
mechanism of selection, a lot of research focused in this area to try to understand mechanism of selection.
Eda
Key gene in understanding adaptation and speciation during colonization of freshwater lakes from marine environment
- in marine fish bony armour (lateral plates) are favoured to protect against large fish predation
- freshwater fish do not have the plates and this increases growth rate and helps fish survive winter and breed earlier.
What four traits identify adaptive radiation
- Recent ancestry from a single species
- phenotype environment correlation
- trait utility
- rapid speciation
hybridization
exchange of genes between species as a result of occasional inter-specific mating. Common in plants and fish, rare in mammals. The result can be complex variation which could have evolutionary significance.
How does polyploidism occur?
Either the duplication of a diploid genome (autopolyloidy AAAA) or fusion of diploid genomes from two species (allopolyploidy AABB)
Which is more common allopolyploidy or autopolyploidy?
Allopolyploidy — occasional hybridization between species
Polyploidism is…
immediate sympatric speciation
systematics
the study of biodiversity and the evolutionary relationships among organisms
Why is there really no such thing as reptiles?
What we call reptiles is a paraphyletic group. We should include birds or not have this grouping at all.
What is the tree of life project and who is responsible for it?
Purpose is to provide information on tree of life. The web project provides 10 000 webpages about biodiversity and phylogenetic relationships. Wayne Maddison (UBC) and Dave Maddison (university of Arizona) started it but it is collaborative effort.
Sister species
Either of the two species formed when an ancestral species split. Use of replicate sister group comparisons can help identify a key trait is involved in extensive diversification.
