Transcript Allopatric Speciation

Biology 3.5
Patterns of Evolution
Credits: 4
External
! Before we begin…
From the examination specifications…
Giraffe Evolution?
Revision
12 bio stuff…
Darwin vs Lamarck
Natural Selection
• Definition
• Types:
– Directional
– Disruptive
– Stabilising
Other Year 12 Concepts
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•
•
•
•
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Founder effect
Population bottlenecks
Genetic drift
Mutation
Migration
Factors affecting allele frequencies…
Species Concept
“a group of actually or potentially interbreeding natural populations that is
reproductively isolated from other such groups”
Main Problem:
- Closely related species produce fertile offspring eg Canis spp.
- Genetically isolated species may be morphologically similar = cryptic species (morph
= “body”)
Main Solution:
- Use DNA analysis to clarify relationships between closely related species.
Extinct: 10,000 ybp
Bio 3.5
Brand new stuff from here
Clines & Ring Species
• Cline: A gradation in one or
more characteristics within a
species esp. between different
populations.
• Ring Species: A series of
neighbouring populations that
can interbreed, but for which
there exist at least two "end"
populations in the series that
are too distantly related to
interbreed
In this diagram, interbreeding
populations are represented by
coloured blocks.
Variation along a cline may bend
right around, forming a ring.
Larus (gull) ring species
A Herring Gull, Larus argentatus
(front) and a Lesser Black-backed
Gull. Larus fuscus (behind)
The Larus gulls interbreed in a ring around the arctic
(1 : Larus argentatus argentatus, 2: Larus fuscus sensu stricto, 3 : Larus fuscus heuglini, 4 : Larus
argentatus birulai, 5 : Larus argentatus vegae, 6 : Larus argentatus smithsonianus, 7 : Larus
argentatus argenteus
Neighbouring groups can hybridise (breed together) but sufficient differences exist to prevent
groups 1 & 7 breeding.
Californian Salamander Ring Species
The many subspecies of
Ensatina salamanders in
California exhibit subtle
morphological and genetic
differences all along their
range. They all interbreed with
their immediate neighbours
with one exception: where the
extreme ends of the range
overlap in Southern California,
E. klauberi and E. eschscholtzii
do not interbreed.
So where do we mark the point
of speciation?
Stages in Species Development
• Species rarely explode suddenly into existence (species
formation is usually slow)
• General pattern:
– Homogenous population splits (cause = geographical
barrier)
– Different natural selection pressures, mutations  gene
frequencies change
– Races form as gene flow reduces, factors preventing
mating begin (“prezygotic”)
– Gene flow further reduces, post zygotic factors occur
(hybrid sterility – eg as in mule)
– Now = two different species.
Stages in Species Development
- A generally predictable series of events occurs as a
homogenous ancestral population evolves into two
separate species.
- The key to this is build up of genetic differences as a
population is split into two populations. Barriers to
frequent mating mean that differing natural selection
pressures and mutations are not shared  populations
go down different genetic pathways.
- Eventually differences build to where the populations
become separate races.
- With enough differences races become difference
subspecies, then separate species.
Extinction Extinction
Sumatran tiger
Sumatran tiger: http://en.wikipedia.org/wiki/Sumatran_tiger
Sumatran tiger clip: http://www.theawl.com/2011/05/get-a-good-look-at-these-awesome-tigers-theyre-almost-extinct
Call of Life (extinction video trailer): http://www.calloflife.org/p-trailer.htm
Extinction
• A natural process – all species that have evolved will eventually go
extinct
• Duration of persistence of a species varies (often from 1 million
years for complex organisms to 10-12 million years for simple
organisms)
• Extinction and mass extinction provides opportunities for other
organisms to evolve and fill vacant ecological niches.
Case Studies
• Humans
How long have we been around? When will we become extinct?
• Anatomical modernity: 200,000 years ago
• Behavioural modernity: 50,000 years ago
• Coelacanth
Coelacanth
Latimeria chalumnae (60kg, 170cm long)
Coelacanths were thought to have gone extinct in the Late
Cretaceous (~65mya), but were rediscovered in 1938 off the coast of
South Africa. 2 Known extant species. The coelacanth has been
nicknamed a “living fossil”, because its fossils were found long before
the actual discovery of a live specimen. The coelacanth is thought to
have first evolved approximately 400 million years ago.
Speciation
• “Formation of new spp. from an existing species”
• Multiplication of spp. not gradual change over time
Allopatric Speciation
• Usually: pops get geographically separated (eg by river)
• Gene flow stops. Genetic isolation occurs.
• Diffs in natural selection can cause diffs in allele
frequencies between the pops over time.
• Diffs may accumulate, when the pops are reunited they
now no may longer interbreed = separate spp.
• NZs isolation/islands has led to many egs of allopatric
speciation.
Allopatric Speciation Questions
1. Why have many NZ birds lost the ability to fly (cf
to their Aussie relatives)?
2. Glaciation creates many isolated mountaintops –
how would this contribute to allopatric speciation?
3. How could sea level rise/fall create new species
through allopatric speciation?
4. Describe how an ancestral robin species gave rise
to the Chatham Island robin and the mainland
robin.
Sympatric Speciation
Reproductive Isolating Mechanisms
Polyploidy
Teosinte  Modern Corn (~1000yrs)
Wheat
Spelt
• Where does this fit in wheat development?
• http://en.wikipedia.org/wiki/Spelt
Evolutionary Relationships
• Phylogenetics: the study of evolutionary relatedness between
groups of organisms. Relatedness is determined by DNA
sequencing data and comparing morphological data
• Phylogeny: The evolutionary development and history of a
species or higher taxonomic grouping of organisms.
• Cladogram: Diagram which shows ancestral relations
between organisms
• Cladistics: method of classifying species of organisms into
groups called clades, which consist of an ancestor organism
and all its descendants (and nothing else).
Cladograms
• Show ancestral relations between taxa
– Using DNA analysis or morphological comparisons
• Species are at the “leaves”
• Common ancestor at the “trunk”
• Have an implicit time axis (runs forward from
base to leaves) but: problems of scale, data
quantity & quality
• May show extinct species, but: DNA from
extinct species is rare
Simplified
Canid Phylogeny
*The canids are an old lineage, separating from the
other carnivores about 60 million years ago.
Separation of a "wolf" branch, a "South American"
branch, and a "red fox" branch occurred more
recently, 7-10 million years ago.
*Mitochondrial DNA analysis of both modern and
historical specimens of red wolves failed to
distinguish red them as a species separate from gray
wolves or coyotes. They appear to be a hybrid
species, and can interbreed with either gray wolves
or coyotes.
*Two different dates for the origin of dogs have
been suggested. Mitochondrial DNA analysis
suggests a date between 60-100,000 years ago -well before the beginning of human agriculture.
Other genetic and archeological evidence suggests a
more recent date -- about 15,000 years ago.
Neolithic cave drawings also show dogs hunting
with humans.
*All domestic dogs are the descendants of a few
ancestral wolf stocks originating in Asia. Surprisingly
this includes New World dogs, who were once
thought to have been independently domesticated
from New World wolves.
Molecular Phylogeny (DNA analysis) may revise
past phylogenies (based on morphology)…
Hedges, S. Blair, and Poling, Laura L. A Molecular
Phylogeny of Reptiles. Science, Vol. 283,
No.5404, pp.998-1001
• The study also cast in doubt the relationship
between the tuatara and squamates. While
fewer gene sequences were available for the
tuatara, six of eight comparisons showed
closer affinities with archosaurs or turtles,
while only two showed squamates as the
closest relative. While the results of this
study are not conclusive, it clearly
demonstrates that we don't know all that we
thought we knew about the phylogenetic
relationships of living or fossil reptiles.
http://home.pcisys.net/~dlblanc/articles/TurtleP
hylogeny.php
Homologous Structures
• The structures shared by a set of related
species because they have been inherited,
with or without modification, from their
common ancestor. For example, the bones
that support a bat's wing are similar to those
of a human arm.
Convergent Evolution
• The evolution of the same biological trait in unrelated
groups / species.
• Examples:
– Shark, icthyosaur, dolphin, penguin (a fish, reptile, mammal
and bird respectively) are unrelated but have evolved a
similar streamlined shape and “fins” in response to their
environment (water)
– Unrelated plants have evolved water storage tissue
(succulent tissues) eg Euphorbia, cacti
• Analogous structures “structures that are alike in
function but have a different evolutionary origin”
– Egs: wings of insects and birds; mammalian and octopus eye
Convergence in Plants
Ferocactus pilosus (Mexican lime cactus)
These unrelated plants have separately evolved the ability to store water in
their stems.
This is a response to the natural selection pressure of dryness in the desert.
The swollen stems are an example of an analogous structure
Divergent Evolution
• When one ancestral group evolves into two or more species, usually
in different habitats
• Features:
– Accounts for most evolutionary change
– Often due to ancestral spp. Increasing range / colonising new areas /
habitats (new ecological niches) The different conditions cause
different selection pressure  different genetic pathways  genetic
isolation  speciation
• Alternatively:
– Sequential evolution: small changes build up over time until a new
species emerges (aka anagenesis, pyletic graduation)
– Budding: a new species branches off while the ancestral species
remain unchanged.
• Cladogenesis: When a whole new group of organisms evolves (eg
primates)
Adaptive Radiation
• “The diversification of a group of organisms into
species filling different ecological niches”.
• Can occur very rapidly, usually when a large
number of ecological niches are vacant.
• Example par excellence:
– Dinosaur extinction 68mya opened up many niches for
exploitation (eg Brontosaurus death opened up a large
browsing herbivore niche). Relatively non specialised
mammals (eg Megazostrodon were, as adaptable
‘generalists’, able to fill these niches quickly and
through natural selection speciate into new forms.
• Other examples:
– Galapagos Finches: 1 South American finch evolved into 14 spp. occupying
different niches (desert, grassland…) on the Galapagos Islands
• NZ Examples:
– 100 spp. of Hebe plants
– 10 spp. of Powelliphanta snails (+ subspecies)
– NZ parrots (kakapo, kea, kaka) from one ancestor (100mya)
• Note: In some of these egs radiation was very fast (many vacant
niches) and involved the founder effect.
Powelliphanta spp.
Ale – see folder
for text
Weird Mammal Groups
• Ungulates (meaning roughly "being hoofed" or
"hoofed animal") a
– The odd-toed ungulates are browsing and grazing
mammals, such as horses, tapirs and rhinoceroses,
whose hooves each feature an odd number of toes
– Even toed ungulates: This group includes pigs,
peccaries, hippopotamuses, camels, chevrotains
(mouse deer), deer, giraffes, pronghorn, antelopes,
sheep, goats, and cattle.
Hawaiian
Honeycreepers
Hawaiian islands: volcanic
origin, variety of habitats.
In absence of other bird spp.
they radiated to fill
numerous niches
Galapagos Finch Niches
http://web.visionlearning.com/cus
tom/biology/animations/darwin_f
Anims…
inches_working.shtml
http://faculty.massasoit.mass.edu/whanna/1
22/page4/page7/page58/page58.html
http://faculty.massasoit.mass.edu/whanna/1
22/page4/page7/page58/page58.html
Co-Evolution
• Change in the genetic composition one species (or group) in response to
the change in another.
• Often occurs when close ecological interaction (symbiosis) occurs
– Parasite / host - exploitation
– Flower shape / pollinator - mutualism
– Predator / prey – exploitation
• Examples
– Lions: speed, strength, co-operative hunting (to catch gazelle)
– Gazelle: speed, size, strength, horns, darting behaviour (to escape lion)
– “evolutionary arms race” one species evolves to respond to the other.
• Each party exerts selection pressures on the other  over time the spp
may become mutually dependent on each other.
• Relationship may become so close that extinction of one app means
extinction of the other
– Pollination Syndromes: where only one animal can pollinate only one specific
plant (often the pollinator beak shape co-evolves with the flower shape)
– Eg Adams’ mistletoe probably relied only on one NZ bird for pollination
(pollinator?) when this birds dropped in numbers Adams mistletoe became
extinct.
Pseudomyrmex ant collecting protein-rich Beltian bodies from a bullhorn acacia, Costa Rica.
This is one of the most famous mutualisms of all, the relationship between Pseudomyrmex
ants and Acacia trees. The ants defend these small trees against herbivorous insects and
vertebrates. The ants also chew away and sting any encroaching plants, clearing an area
that may be up to 4 yd (4 m) in radius. In return, the plants give the ants food, such as the
yellow Beltian bodies seen here, and nectar from extra-floral nectaries. The Beltian bodies
contain proteins and lipids and are produced on the youngest and most delicate leaves. The
plants also produce thorns that the ants hollow out for nests.
Anna's Hummingbird (Calypte anna) and bottlebrush sp.
The needle like beak and hovering ability of a
hummingbird is allows it to extract nectar (and pollinate)
funnel shaped flowers or flowers with no “landing pads”
Dactylanthus
taylorii
Pollinated by native bat with which it
shows coevolution.
Bat: nocturnal, blind BUT good sense
of smell
Flowers: drab, open at night, strong
scent (like a bat), wide shape (for
easy access)
Punctuated
Equilibrium
• Evolutionary model where there
are long periods of little change in
a spp punctuated by short bursts of
rapid change.
– Long periods of no evolutionary
change (stasis)
– Stasis punctuated by short periods of
evolution producing new species
rapidly
– Stimulus for evolution =
environmental change
– Species’ spend most of existence in
stasis
– If Correct: no transitional fossils,
sudden appearance of new types
Gradualism
• Evolutionary model where
the accumulation of changes
resulting in speciation occurs
slowly and steadily
– Evolution proceeds slowly but
continuously in response to
selection pressures
– Eventually changes in
adaptive characteristics
accumulate until speciation
occurs
– If correct transitional forms
should be seen (as is the case
with horse evolution)
– Example: Trilobites changed
gradually over three million
years
A Trilobite fossil: Kainops invius
Trilobites…
• Hard-shelled, segmented creatures lived over 520 million
years ago in Earth's ancient seas.
• Extinct before dinosaurs arrived
• Key creatures of the Paleozoic Era, (1st era with complex life)
• Fossils found in rocks in all continents
Body plan: 3 main parts – head,
segmented thorax, and a pygidium
(tail piece)
Trilobite means three lobed (see right).
Huge morphological diversity in
trilobites but all have this basic
structure
www.trilobites.info
Poster Task
Rest of the period to:
• Present an A3 colour poster on an example of
convergent evolution, allopatric speciation or
sympatric speciation.
• You must:
•
•
•
•
Define the type of evolution speciation
Give a captioned example (no kea, kaka, butterfly)
Explain how this example came about
Name it!
Notes Pages
Adaptive Radiation
• “The diversification of a group of organisms into
species filling different e________ n______”.
• Can occur very r_______, usually when a large
number of ecological niches are v____.
• Example par e______:
– Dinosaur e______ 68mya opened up many niches for
exploitation (eg Brontosaurus death opened up a large
browsing h______ niche). Relatively non specialised
mammals (eg M_____ were, as adaptable ‘generalists’,
able to fill these niches quickly and through natural
selection s________ into new forms.
• Other examples:
– Galapagos Finches: 1 South American finch evolved into _____ spp. occupying
different niches (d________, g_________…) on the Galapagos Islands
• NZ Examples:
– 100 spp. of H_________ plants
– 10 spp. of P_________ snails (+ subspecies)
– NZ p______ (kakapo, kea, kaka) from one ancestor (1_____)
• Note: In some of these egs radiation was very fast (many vacant
niches) and involved the f_________ e______.
Powelliphanta spp.
Co-Evolution
“Change in the ________ composition one species (or
group) in ____________ to the change in another”
• Often occurs when close ecological interaction (____________) occurs
– Parasite / ________ - exploitation
– Flower __________ / pollinator - mutualism
– Predator / __________ – exploitation
• Examples
– Lions: speed, strength, __________ hunting (to catch gazelle)
– Gazelle: s__________, size, strength, horns, darting behaviour (to escape lion)
– “evolutionary arms race” one species e________ to respond to the other.
• Each party exerts s__________ pressures on the other  over time the spp
may become m__________ dependent on each other.
• Relationship may become so close that extinction of one app means
e____________ of the other
– Pollination S__________: where only one animal can pollinate only one specific
plant (often the pollinator beak shape co-evolves with the flower shape)
– Eg A__________’ mistletoe probably relied only on one NZ bird for
p____________ (pollinator?) when this birds dropped in numbers Adams
mistletoe became extinct.
Pseudomyrmex ant collecting protein-rich Beltian bodies from a bullhorn acacia, Costa Rica.
This is one of the most famous mutualisms of all, the relationship between Pseudomyrmex
ants and Acacia trees. The ants defend these small trees against herbivorous insects and
vertebrates. The ants also chew away and sting any encroaching plants, clearing an area
that may be up to 4 yd (4 m) in radius. In return, the plants give the ants food, such as the
yellow Beltian bodies seen here, and nectar from extra-floral nectaries. The Beltian bodies
contain proteins and lipids and are produced on the youngest and most delicate leaves. The
plants also produce thorns that the ants hollow out for nests.
Anna's Hummingbird (Calypte anna) and bottlebrush sp.
The needle like beak and hovering ability of a
hummingbird is allows it to extract nectar (and pollinate)
funnel shaped flowers or flowers with no “landing pads”
Punctuated
Equilibrium
• Evolutionary model where there
are long periods of _________
change in a spp _______ by short
bursts of r____ change.
– Long periods of no evolutionary
change (_____)
– Stasis punctuated by short periods of
evolution producing new species
________
– Stimulus for evolution =
environmental change
– Species’ spend most of ____ in stasis
– If Correct: ___ _________ fossils,
sudden appearance of new types
Gradualism
• Evolutionary model where the
________ of changes resulting
in speciation occurs _____ and
steadily
– Evolution proceeds slowly but
continuously in response to
_____ pressures
– Eventually changes in adaptive
characteristics accumulate until
______ occurs
– If correct transitional forms
should be seen (as is the case
with horse _____)
– Example: ________ changed
gradually over three million
years
A Trilobite fossil: Kainops invius