L08-Species Concept2 (Maj)

7/28/2019 L08-Species Concept2 (Maj)

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The CONCEPT of the SPECIES


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we can look at biodiversity at many levels

mostlywe are looking at conserving all thedifferent 'kinds' of things

this usually means the SPECIES


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The composition and levels of biodiversity

Ecologicaldiversity Genetic diversity Organismaldiversity

biomes Populations kingdoms

bioregions Individuals phyla

landscapes Chromosomes families

ecosystems genes genera

habitats nucleotides species

niches subspecies

populations Populations

individuals


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1. reproductively

-individuals able to interbreed with each other(the traditional definition)

mostly relevant to animals(hybridization is relatively common inplants)

SPECIES can be defined in many ways


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there are many waysthat populations can

become reproductivelyisolated

eg Kangaroo Pawthere is variation inflower length whichcan result inreproductive

isolation


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flower length determinesthe type of pollinatorvisiting flowers results

in genetic isolationbetween adjacent plantsof different species


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2. morphologically

- individuals look alike and form a distinctive group

where do we draw the line ? traditionally flower (or reproductivestructures) have been emphasised to definespecies

these are relatively stable within plantgroups


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3. chemically

- individuals which can be consistently identifiedusing a range of compounds

volatile oils, flavonoids, proteins, enzymes useful in detecting hybrids

current emphasis is on DNA and proteins


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eg flavonoidpatterns detected by paperchromatography

Species 1 Species 2 Hybrid

flavonoids are chemicals extracted from leaves


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parent1 parent 2

hybrid


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or proteins detected bygel electrophoresis

Species 1 Species 2 Hybrid

electric

current

gel

proteins


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Sometimes differentiation of species gives differentviews:

eg chemical racesmorphologicallyidentical,

butchemically distinct

examples:

Eucalyptusoil typesHeath (Epacr is impressa) flower colourshemp (Cannabissp) psychoactive compounds


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some morphologically uniform species canbe genetically extremely variable

eg Sty l id iumin WA


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16 chromosomeraces which wereunable to interbreed

what is theirstatus ?are they all the samespecies ?


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are some characters intrinsically moreimportant than others ?

ie should we rely on morphology, orare chemical and genetic structure justas important

genetic make-up is generally acceptednow as the most important characteristic


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EXAMPLES

1. Eucalyptu s yarraensis(Yarra Gum)

now widely accepted as a well defined 'species'

has been recognised as rare andthreatened and listed underFlora and Fauna

Guaranteelegislation

once included as a rough-barked variant ofEucalyptus ovata(Swamp Gum)

which is very common, not needingprotection


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Eucalyptu s yarraens is

Eucalyptu s ovata


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SO . is it

common, and needing no protectionOR

rare, in danger of extinction and needingprotection

depending on the TAXONOMIC STATUS ofthis tree, legislative protection and resources

for conservation will vary


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2. Eucalyptu s X studleyensis

the Xindicates a hybrid

originally described as a species, but nowaccepted as a hybrid between E. ovata(Swamp

Gum) and E. camaldu lens is(River Red Gum)

as a hybrid it cannot breed true should we treat it as a 'once-off' oddity, or worthyof protection ?


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3. Eucalyptus crenulata(Buxton Gum)

only known from two sites at Yering(with only a few trees) and Buxton (with

a few hundred trees)

populations are morphologicallyand chemically virtually identical


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it is easy to propagate - do we need to conserveboth populations ?

do we need anynatural populations ?? ($$$$)

consider as an umbrella or flagshipspecies to conserve the community (which

has some other interesting species such as

Sphagnummoss ) ?


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SHOULD WE EMPHASISE MORPHOLOGY OR

EVOLUTIONARY RELATIONSHIPS IN OURRECOGNITION OF SPECIES ?

(phenetics or phylogeny)

phenetics based on how species appearie morphological similarity

phylogeny based on inferred pastevolutionary relationships


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Eucalyptus - one genus o r nine ??

one recognisable group EucalyptusORninegroups which are virtuallyindistinguishable using adult morphology

base classification on the number ofopercula('caps') in buds which reflects pastevolution

Monocalyptus, Symphyomy rtus etc

groups are accepted generally, but givendifferent RANKS


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eucalypt flowers have a cap or operculum

(instead of separate sepals and petals)

some specieshave two caps(separate fusedsepals andpetals)

scar


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so either:

1. one genusand all groups = Eucalyptus

OR

2. several generasuch as

Corymbia

Symphyomyr tus

Blakella

Monocalyptus etc

(wh ich we can only separate on m icroscopic

characters)


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ARE SOME SPECIES WORTH CONSERVINGMORE THAN OTHERS ?

such asIsop hysis tasmanica

(Hewardia) in Tasmania


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only one species

in a genus(monospecificspecies)

are species with

a unique genepool moreimportant thanothers ?

Isophysis


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HOW MUCH OF EACH SPECIES SHOULD WECONSERVE ?

ALL ? probably not economically orpolitically possible

SOME ? use genetic analysis to decidehow to conserve a representative gene pool

use morphological and chemicalmarkers to indicate likely genetic variation


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in the end, it is our ideas about the nature

of species and the variation within them thatguides our attempts to conserve as muchas possible of the gene pool of species

how much we actually conserve dependson the resources we have available

$$$$$

L08-Species Concept2 (Maj)

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