Animals and their mating calls

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Animals and their mating calls
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More about diversity Speciation

• Interestingly, Darwin did not write much about
  this topic.

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• Species Concepts (continued)
• Morphological (Typological) Species
• Idea dates from Plato, Aristotle, through
  Linnaeus
• Claims that the universe has a limited number of
  types, models, or kinds of species
• All individuals reflect the copying of the type
• Variation is simple a product of poor copying
• Similarity in morphology provides means for
  species recognition

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• Nominalistic Species
• Species are so called by man as a means of
  convenience
• Species dont exist only individual organisms
• Advocates deny discontinuity between species
• Few modern adherents

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• Biological Species Concept
• Species consists of populations that share an
  evolved genetic program
• Emergent properties
• 1) A genetic unit - individuals possess genes
  from total gene pool
• 2) A reproductive unit - individuals respond to
  one another as potential mates
• 3) An ecological unit - functions as a unit with
  other species in its environment

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Simple Phyletic Speciation
A B C D
Time
One transformed species still present after
several speciation events
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Multiplication of Species
A A B C D A B C D E A B C E
Time
Ancestoral species gives rise to one or more
species, but itself does not necessarily disappear
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• Models of Speciation
• 1) Allopatric Speciation
• 2) Parapatric Speciation
• 3) Sympatric Speciation
• 4) Polyploidy

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• Allopatric Speciation
• 1. Separation of orginal gene pool into two or
  more isolated groups
• 2. Differentiation - two or more populations
  evolve in different directions to become
  morphologically or physiologically or
  behaviorally different
• 3. Secondary Merger - leads to species
  interactions
• a. one form may outcompete other form and
  eliminate it
• b. no competition, no hybridization
• c. hybridize and form one population
• d. competition leads to further divergence

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• Most common model of speciation in groups of
  sexually reproducing animals
• Premating isolating mechanisms are usually major
  barrier to hybridization

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• Stages in Allopatric Speciation
• Freely Interbreeding
• Barrier Formation
• Range Expansion
• Stabilization

A
A A
A
A
A
B
Time
A
B
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• Parapatric Speciation - may yield sibling
  species, arises whenever species evolve as
  contiguous population in a contiguous cline
• 1. No spatial isolation required
• 2. Species show little in the way of dispersal
• 3. Reproductive isolating mechanisms arise by
  selection as genetically unique individuals
  exploit new habitat

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• Populations normally occur as small groups that
  are semi-isolated
• Inbreeding is common
• Little long-range dispersal (sessile, sedentary
  lifestyles)
• e.g.,
• Plants
• Mole rats
• certain snail species
• flightless insects

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• Stages in Parapatric Speciation

Dry
A
Presence of Gradient
Wet
Time
A1
A
Limited gene flow
New species becomes adapted
B
A
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• Sympatric Speciation - origin of isolating
  mechanisms within the dispersal area of the
  offspring of a single cline
• 1. Initial step involves the establishment of a
  premating isolating mechanism
• 2. Speciation often occurs at or near center of
  the species range
• 3. Gives rise to sympatric sibling species

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• Largely limited to plant and animal parasites
  (gt500,000 species of insects)
• Host and changes in host selection appears to
  explain how sympatric speciation occurs
• e.g.,
• 1. Courtship, mating, and egg laying of
  parasites occurs on or near host
• 2. Mate selection, therefore depends on host
  selection
• 3. A shift to new hosts has a profound effect on
  mate selection and provides a barrier to gene
  exchange

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Sympatric Speciation
A
Polymorphism forms within population
A
A1
Time
A
B
New species evolves
B
A
New species exploits new habitat
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• Example Hawthorne Fly, Rhagoletis pomonella
• originally parasitized fruits of N. American
  Hawthorne apple (Crataegus)
• Around 1864, a race of the fly was found to
  parasitize introduced Old World apples (Malus)
• It first appeared in New York and then spread to
  other regions
• In 1960, a new race was found that parasitized a
  cherry (Prunus) orchard in Wisconsin
• Genetic changes involve genes that control host
  recognition and selection
• In some species, 1 locus controls host plant
  selection

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• Speciation by Polyploidy - abrupt speciation that
  arises with change in chromosome number
• Haploid (n) gt Diploid (2n), egg sperm
• Egg 2 sperm gt Triploid (3n)
• Polyploidy - multiple sets of chromosomes
• Found in about half of Angiosperms
• Organisms are often sterile, but reproduce
  vegetatively
• Also found in certain shrimp, insects, and lizards

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• Isolating Mechanisms - various devices that
  prevent the breeding of a species with another
  species that are actually or potentially
  sympatric
• In many cases, closely related species are not
  sterile when interbreeding occurs
• e.g., Mallard x Pintail Duck
• hybrids and backcrosses are fertile
• Reproductive Isolating Mechanisms may be due to
  habitat, seasonality of reproduction, behavior,
  and physiological differences.