BIOL359 Study Guide - Final Guide: Species Problem, Isthmus Of Panama, Species Complex
5 May 2018
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BIOL 359 Lecture Notes
Topic 12: Kin Selection
Do behavioural traits evolve like other traits?
➢ A: Yes. Experiment was done where researchers bred experimental females that were the most
aggressive over time, female offspring were very aggressive
Social Interactions
➢ Actor: individuals carrying out an action (or behaviour)
➢ Recipient: individual on the receiving end of the behaviour
➢ Four types of social behaviour
I. Mutually Beneficial = fitness gains for the participants
e.g. communal breeding in the Greater Ani
II. Selfishness = fitness gain for the actor, loss for the recipient
e.g. cane toad tadpole cannibalism
III. Altruism = fitness gain for the recipient, loss for the actor
e.g. alarm calling in the Ground Squirrels
IV. Spite = fitness loss for the actor and recipient
e.g. strains of
E. coli
that produce mutually lethal toxins
➢ Altruism and Inclusive Fitness
• The fitness of an individual can be divided into two components. Individuals of inclusive fitness
consist of direct and indirect fitness
• Direct fitness
o An individual’s direct contribution to the next generation by reproduction (number of offspring
contribution)
• Indirect fitness
o Arises from additional reproduction by relatives that results from an actor’s actions (e.g.
assistance). It is additional reproduction that would not have been achieved without the
assistance provided by the actor.
• Kin selection: the selection for, and spread of alleles that increase indirect fitness
Calculating Coefficients of Relatedness
➢ An allele that favors altruism can spread under certain conditions. The key parameter is
r
➢
r
gives the probability that an allele
in the actor and allele I the
recipient at a given locus are
identical by decent or arose by
replication from the same ancestral
copy of an allele
➢ Hamilton’s rule: an allele for
altruistic behaviour will spread if B x
r – C > 0, where B is the benefit to
the recipient, C is the cost to the
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actor, r is the coefficient of relatedness. The costs and benefits are measured in terms of surviving
offspring
• E.g. adoption in red squirrels females adopt kittens according to Hamilton’s Rule. Adoption
depends on how many kittens she already has. If a female already has a very large litter, she
will be less likely to adopt. The benefit of adopting drops according to the size of the litter and
a lower coefficient or relatedness
Example: Wood Mouse Altruistic Sperm
➢ Polyandrous: mate with more than one male
➢ Sperm from a single male will form sperm trains in order to get to the egg faster
➢ Once the sperm train reaches the egg, it has to break apart the sperm at the back of the train
and will undergo acrosome reaction (self-destruct)
Topic 13: Species Concepts & Speciation
Species species in both singular and plural. There is no such thing as a “specie”
What is a Species?
➢ Species = “kind”. Taxonomic units to which taxonomists assigned to species
➢ Defining “species” has and continues to be controversial due to problems with the establishment of
practical criteria for recognizing evolutionary independence. As a result, there are many species
concepts
Topological or Morphological Species Concept
➢ Type specimen = a single individual that represents the entire species
➢ Specimens are considered to belong to the same species if they agree morphologically with the
“type” of the species
➢ However, many species show a continuum of morphological variation
➢ Today the “type method” is still used, but there is an attempt to select defining characters that have
a genetic basis
➢ There are clearly written rules for naming and renaming taxa: Botanical Code, Zoological Code etc.
➢ Problems:
• Cryptic Species: species that cannot be distinguished on the bases of their morphological
characteristics
• Phenotypic Plasticity: morphological variation that does not have a genetic basis. Environmentally
induced morphological differences
Biological Species Concept
➢ Species are groups of interbreeding natural populations that are reproductively isolated from other
such groups individuals within a species resemble each other due to gene flow and interbreeding
➢ Evolutionary criterion is reproductive isolation and interbreeding
➢ Commonly applied to natural populations but is difficult to test
➢ Cannot be applied to “species” that hybridize freely or reproduce asexually
➢ Cannot be applied to extinct species
➢ Problems:
• Asexual Taxa: obviously does not apply
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• Fossil Taxa: cannot be tested
• Hybridization: difficult to apply the biological species concept to taxa that hybridize (intra- =
among, inter- = between)
Phylogenetic Species Concept
➢ Species consists of a population or group of populations that share a common evolutionary fate
though time
➢ Species are monophyletic groups: taxa that contain all of the known descendants of a single
common ancestor
➢ Populations must have been evolutionarily independent long enough for diagnostic traits to appear
➢ Can be applies to both living and extinct species
➢ Is applicable to species that reproduce asexually or sexually
➢ Based on evolutionary independence – can be applied without direct observation of species
Applying the Species Concepts: The Algae Genus Pseudo-nitzschia (pp. 613)
➢ Cryptic species: indistinguishable morphologically, but divergent in other characteristics
➢ About 2 million species have been described, but there is estimated to be about 1 to 10 billion,
and even greater species
Mechanisms of Speciation
General Process of Speciation: The Allopatric Speciation Model
I. Step 1: physical Isolation of Populations
II. Step 2: Divergence of the Isolated Populations
III. Step 3: Reproductive Isolation
IV. Step 4: Secondary Contact (this will not always occur)
Physical Isolation of Populations
➢ Dispersal rare kind of event. Colonization of a new habitat. Once colonization has occurred there
is no more gene flow (e.g. Hawaiian Drosophila)
➢ Vicariance the erection of an actual
physical barrier that isolates the
population
• E.g. The snapping shrimp
• South America drifted into proximity of
North America. They collided and
created the Panamanian Isthmus
emerged from the sea
• Effects of the formation: separation of
marine organisms of Caribbean and
Pacific Oceans
➢ What drives Divergence after isolation has occurred? A: mutation, genetic drift, bottle necks, viability
selection, sexual selection, fecundity selection
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Document Summary
Experiment was done where researchers bred experimental females that were the most aggressive over time, female offspring were very aggressive. Actor: individuals carrying out an action (or behaviour) Recipient: individual on the receiving end of the behaviour. Four types of social behaviour: mutually beneficial = fitness gains for the participants. Iv. e. g. communal breeding in the greater ani. Selfishness = fitness gain for the actor, loss for the recipient e. g. cane toad tadpole cannibalism. Altruism = fitness gain for the recipient, loss for the actor e. g. alarm calling in the ground squirrels. Spite = fitness loss for the actor and recipient e. g. strains of e. coli that produce mutually lethal toxins. Altruism and inclusive fitness: the fitness of an individual can be divided into two components. Individuals of inclusive fitness consist of direct and indirect fitness: direct fitness, an individual"s direct contribution to the next generation by reproduction (number of offspring contribution)
