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BAGAIMANA SPESIESBAHARU MUNCUL?
Apa asal usulbiodiversiti sekarang ?
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“biodiversiti” – hasil proses evolusi
dan speciasi
HOW we define species also has amassive impact on our view of'biodiversity’ - the study ofTAXONOMY
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kita boleh melihat perbezaan paten variasispesies dan cuba memahami bagaimana ia berlaku
Darwin explains evolution …..
Those animalsthat survive
and reproduce ……. are those animals
that survive
and reproduce ….
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Proses Asas…….
tumbuhan dan haiwan menghasilkan banyakanak untuk pengekalan populasi
biasanya berlaku persaingan untuk mandiri
kerana sumber terhad
anak- anak mempunyai ciri-ciri berbeza
Individu akan cuba menyesuaikan diri denganpersekitaran.
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Individu yang dapat menyesuaikan diridengan persekitaran akan dapat hidupdaripada yang tidak dapat menyesuaikan diri
individu ini akan membiak danmemindahkan sifat-sifatnya kepada generasi
seterusnya.
and so on……….
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Andaian proses yang berlaku
kebanyakan speciasi di kawasan terasing(geografi)
speciasi berlaku di mana desakan untukpemilihan adalah tinggi (ie .hanya beberapaindividu hidup- individu dengan variasimemberi kelebihan persaingan
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Ini berlaku apabila sumber (air, nutrien ?)terhad
Individu yang hidup merupakan pengasaskepada generasi seterusnya
kumpulan baru akan terpisah secara genetik,(terutamanya terasing secara geografi) dantidak boleh membiak antara satu sama lain akan
membentuk spesies baru Bagaimana ini berlaku dan bolehkah kita
lihat kesannya?
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PATEN pada ARAS SPESIES
komuniti hutan hujan mempunyaikepelbagaian pada aras FAMILI tetapi beberapaspesies dalam setiap famili
Jadi komuniti hutan hujan mempunyaibanyak spesies, kebanyakan tidak berkaitanantara satu sama lain dan datang daripadafamili berbeza.
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di kawasan tanah lapang, vegetasi
mempunyai kepelbagaian SPECIES yangtinggi tetapi hanya beberapa famili yang adaeg in W.A.
89 families
5 families = 56% of species
egProteaceae ( Grevil lea, Bank sia )
Myrtaceae ( Eucalyp tus , Lep tosp erm um )Mimosaceae ( Acacia )
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on the sand plain north of Perth at Eneabba
in a 1m X 1m quadrat can get 48species
in a 10m X 10m quadrat can get 110species
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Sand Plain north of Perth
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- alpha diversity- species richness within a habitat
- species richness within forest, or swamp etc
- beta diversity- species difference between habitats
nearby quadrats might have only 60%species in common
- species difference between swamp area andadjacent forest
DIVERSITY PATTERNS
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- gamma diversity- difference within habitats between regions
difference within rainforest habitat betweenOtway rainforest and East Gippsland rainforest
DIVERSITY PATTERNS
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south west Western Australia has aremarkable number of species in a small area
high levels of species r ichness and
endemism
> 8,000 species, 75% endemic
the Fitzgerald River area alone has moreplant species than the whole of the British Isles
Case Study: the Western Australian flora
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GENUS NUMBER of SPECIES Acacia 400+Eucalyp tus 300+Grevil lea 200+Sty l id ium 150+
Melaleuca 150+Hakea 100+Caladenia 100+
there are some 'centres of diversity’ or“diversity hot spots”
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Fitzgerald River1750+ species
Mt Leseur820+ species
Stirling Range
Murchison Gorge
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plantdiversity“hot spots”
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often have largeor showy fruits
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In W.A. there is high ' -diversity' (gamma-diversity)
ie variation ACROSS the landscape
even relatively close areas havedifferent suites of species
how did this diversity arise ?
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EXPLAINING DIVERSITYvegetation types
forest
arid zone
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divide W.A. into three rainfall zones
HIGH (800 - 1500 mm)
TRANSITIONAL (300 - 800 mm)
ARID
(< 300 mm)
decreasingrainfall
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nutrient poor soils
these are some of the least
fertile soils in the world(low P)
plants have evolvedmany adaptations to be ableto compete
proteoid roots,symbiotic relationships
the landscape has barely changed since thePermian
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erosion of laterites resulted in mosaic ofsoil types
typically laterite 'islands' in a sea of salinevalley floors
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adaptation to these nutrient poor soilshas resulted in 'adaptive radiation'
(each species adopts a different survival strategywhich reduces direct competition)
some individuals have shallow extensive roots
some have deep roots
some exploit the surface to target brief rainfall
eventssome have both deep roots and extensive shallow
roots
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reducesdirectcompetition
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plants growing together have different survivalstrategies
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in the Transitional Rainfall Zone climatic changeresulted in significant rainfall fluctuations
mean !
“high”
rainfall
“low”rainfall year
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FREQUENT and UNPREDICTABLE
environmental stresses for a long period
variable climatic conditions result in strong
selection pressure strong selection pressure
results in high levels of speciation
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following a fire
CONDITIONS SEEDLING SURVIVALDrought 780 seedlings nearly zeroArtificial watering 90% survivalWet depressions 90% survival'Good' year 40% survival
strong selection acting on populations isolated bysoil type (“island” effect)
results in different species on different soil“islands”
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SUMMARY
factors contributing to the development of highdiversity in W.A. are:
nutrient scarcity result of long period of environmental
stability and leaching
geographic isolation (eg by arid Nullarbor Plain)mosaic of landforms and soils
(small scale isolation and “island” effect)
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cycles of strong selection pressure following disturbances such as
drought, fire 'flush-crash' cycles
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so we can see that many of our ideasabout speciation are supported by this casestudy
read about some other well knownexample such as Darwin’s finches in thereferences !!
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many species are now at risk of extinction due tofragmented habitat
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composition of roadside patches is very variable
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if we know that our biodiversity isdistributed across the landscape, no single
reserve can conserve all of the speciespresent in the region
every “patch” has a different suite of species
how many patches can we protect ?
with limited resources which patches willwe choose to protect ?
....see the prac exercises !!!!