Transcript Species concept

Ecosystem
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Ecosystem Level:
Ecological Area = number of species (species richness)
Taxonomic definition: Morphology & Life History differences
Molecular genetics
Phylogenetics tree construction
Maintain max. diversity of evolutionary lineages
Combining morphological and molecular tools can reveal historical
forces = possibly leading to conservation actions or evolutionary
explanation of events.
Example:
Microbial communities
Ecotones (between forest and savanna) generation of diversity
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Defining species
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Taxonomical Point of View
• Groups within a species defined as being of a
taxon lower than a species
• Zoology = subspecies
• Botany = variety, subvariety,form
• Conservation Biology = Evolutionary
significant units (ESU) [species or smaller
distinct population segments]
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Difficulty in defining "species" and
identifying particular species
• Species = ??
• Before Evolution Concept:
Carl Linneaus invented
classification system
(religious concept, all
creatures already exist)
• Hybrid = ??
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“Text book” definition
• Species = individual organisms from a natural
population; generally interbreed and produces
fertile offspring (Ernst Mayr)
• Exclude unusual or artificial mating: eg. horse to
donkey = a mule (sterile) and only occur in
captivity
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Species
• Previous definition relies on sexual
reproduction
• Asexually reproducing organism eg. fungi or
certain clone plants the previous definition
would not apply
• Often difficult to tell based on morphology
alone
• Natural or experimental hybridization
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Different way of thinking….
• Barriers to create species
– Reproductive (Mating behaviour eg. aerial dance,
song, physical trait selection)
– Geographical (Pangaea to current geography)
Allopatric speciation
—Look for historical evidence for possible evolution
events
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Different way of thinking…..
• Be careful when sampling; possible Ring species eg.
D. Irwin’s study on Greenish warbler
• Morphological differences pending source of samples
• Possibly no obvious species boundary except at the
“end” …otherwise interbreed
East Siberia two
West Siberia
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one bar on wing bars
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Species side by
side
• Species can diverge
while living side by side
Sympatric speciation
• Cichlid (Amphilophus
citrinellus) versus (A.
zaliosus)
• A. citinellus = prey on
snails
• A. zaliosus = prey on
insect larvae
• Evolve different body
shape and mating
preferences
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Some examples of species
definition
Species
Definition
Textbook (Biological)
Individual organism; generally interbreed; produce fertile
offspring (E. Mayr)
Typological
Classical; Fixed properties; Phenotypic based (Linnaeus)
Genetic (Phenetic)
Similar DNA; DNA-DNA hybridization; Bar coding project
(Current)
Evolutionary (Darwinian)
Shares an ancestor; subspecies
Phylogenetics
Shares an ancestor; not subspecies (Current)
Ecological
Adapted to a particular niche
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Thoughts on species concept
• No species concept are
entirely objective
• Complexity of life the
likelihood of objective
definition would be
impossible
• Many disagreements in
labeling a species or defining
a species
• Biologist would settle for
what works for them;
mixture from different
definitions would be ideal
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Example of species
identification
• Example of defining different subspecies of Koala
bears
• Due to dramatic local declines perhaps there are
different Koala species
• Based on morphology there could be 3 subspecies
• Minisatellites, mtDNA, RAPDs and SSRs failed to
identify differences
• Data show strong North/South continuous cline
• Morphological differences possibly due to
environment and not genetics (Sherwin et al 2000
Cons Biol 14:639-649)
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Example of species
identification
• Sea bird (Petrel)
• mtDNA revealed different
haplotypes for different
morphological types
• 3 (B,C,D) for the dark
species
• 5 (A,E,F,G,H) for the light
species
• Assortative mating to
maintain species
differences (Brooke and Rowe, 1996
Ibis 138:420-432) (See Textbook p.78)
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Example of subspecies
• Ursus americanus
kermodei (Kermode Bear)
• White phase of the black
bear (mtDNA confirm)
(Marshall and Ritland
2002 Molecular Ecology 11:
685-697)
• Possibly due to population
isolation, assortative
mating (SSR data)
• Due to a single nucleotide
change (Ritland et al
(2001) Tyr-to-Cys
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Hybrids
Abies veitchii
Abies homolepis
• Interbreeding of two separate species
• Using maternal and paternal markers to
determine hybrid zones and extensiveness
of the zone
• Conifer species in Abies (paternal cpDNA
and maternal mtDNA)
• Using mtDNA, cpDNA and RAPD show
hybrid saplings however little adult hybrids
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Hybrids
• Detection of invasive species is very important and
an important sign is the detection of hybrids
between invasive and native species
• Use of molecular markers are especially important
for species that lack many morphological differences
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Individuals
• Identification of individuals to species can be difficult
pending on life stage (eg. non flowering plants or
tadpoles) or lack of morphological characters
• To delimit a population, it is important to be able to
identify individuals
• Biomonitoring by using larvaes is difficult without some
kind of unique identifiers
• Barcoding of life project will greatly improve these
problems but it will not work for many organisms eg.
anaerobic organisms, many plant groups, prokaryotes
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• Forensic investigations calls for identification
of suspect and victims
• Use of genetic markers great aid in the
investigation
• Recall VNTR marker usage in previous lecture,
can use RAPD, AFLP and now a suite of SNP
markers to have compare evidential material
with known samples (eg. saliva, hair, tree
stumps etc.)
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Regions for barcoding of life
http://www.destination360.com/c
entral-america/costa-rica/costarica-animals
http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield
/polysiphonia.html
http://oceanexplorer.noaa.gov/explorations/04alaska/logs/summary/media/live_bamboo.html
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Reproduction: determination of Sex
• With immaturity and cryptic morphology the
identification of the sex of an individual is not
always easy
• To calculate an effective population size the sex of
breeding individuals needs to be identify
• Specific primers eg. SRY gene on the Y
chromosome can help detect mammalian males
• Appropriate control is required to eliminate
“false” females by using a housekeeping gene eg.
actin
• Dart samples from whales to identify individuals
and the sex of an individuals is an active area of
molecular ecology (Barrett-Lennard, Van.
Aquarium)
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Determination of Sex
• Exceptions in standard sexing of mammals
such as bird (females = WZ, males = ZZ)
there is the helicase DNA binding gene
(CHD1) which produce different size
products for the WZ chromosomes
• Even in plants there is an example of Y
(male) specific PCR product eg. hops
[diecous plants]
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Prey vs Predator
• Predator-prey interactions, most commonly
look at the gut contents to study
relationship
• Diet analysis eg. prey “crumbles”
• Fecal content eg. coyote diet
• Tracking predator eg. gut cells in fecal
matter
• Identify individual prey using mtDNA eg.
COI gene, 12S rRNA
• Multiple copies of mtDNA great chance of
prey amplification
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Prey vs Predator
• Complication of possible secondary prey with PCR
techniques, there is a great chance of this
problem with non-invasive sampling
• Some techniques are more problematic eg. RAPD.
AFLP
• Usage of specific primers such as SSR will reduce
generation of incorrect amplicons, dropout of
specific alleles will bias genetic variation
estimates
• No techniques are 100% error proof
• Replication of 10% of samples will be important
and negative control when doing PCR must be
done
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