Week 10 Flashcards
What is biodiversity?
The variety of ecosystems, species, populations within species, and genetic diversity within species
Biodiversity = ‘genetic’, ‘organismal’ and ‘ecological’ diversity
What underpins biodiversity?
What drives biodiversity
Why do some areas have more biodiversity?
Why has diversity changed over time?
Has diversity reached a limit?
All contribute to our understanding of the evolutionary framework that drives biodiversity
What do fossils tell us about the history of biodiversity?
General, erratic, rise in overall biodiversity reaching a peak around the end of the Tertiary (2 mya)
What do fossils tell us about the evolution of history of species?
New groups of organisms appear, diversify and generally persist for very long periods of time
What are mass extinctions?
When more than half of multicellular species became extinct in one go
What are examples of the 5 mass extinction?
1 - 440, mya: climate change. 25% of families lost.
2 - 370 mya: global climate change? 19% of families lost.
3 - 245 mya: climate change caused by volcanic activity? 54% of families lost.
4 - 210 mya: shortly after dinosaurs and mammals evolved, causes unknown 23% of families lost.
5 - 65 mya: Wiped out dinosaurs! Asteroid impact and subsequent climate change. 17% of families lost
What are selective cause for determining if a species survives or dies?
Entire groups were lost while others survived
Survival greater for species with wider geographical and ecological distributions…. and for species rich groups
What are random changes for determining if a species survives?
With respect to many characteristics/adaptations, e.g. mode of feeding
Superb adaptive qualities were lost
What is an example of a trait being lost from a mass extinction reevolving?
Oyster drills - The ability to drill through bivalve shells and eat prey - evolved in Triassic gastropods – lost in late Triassic extinction – took 120 MY to evolve again
What are the three tiers of evolution?
1 - Microevolutionary change within populations and species
2 - Macroevolution – differential proliferation and extinction of species during normal ecological time
3 - Shaping of biota by mass extinctions
Why are mass extinctions potentially considered a third tier of evolution?
Physical & biotic conditions differ before and after mass extinction
Wipe the slate clean - allow new evolutionary radiations
Stephen Jay Gould - 1985
What is background extinction?
Failure to adapt to changes caused by abiotic and biotic factors
What are examples of abiotic and biotic factors causing extinction?
Environmental (climate) change
Predation
Disease
Competitive displacement (competition)
What is an example of disease causing extinction?
Chytridiomycosis - caused 7/14 Australian rainforest frog species to go extinct in the last 30 years
What did Knoll et al 1986 discover about competition amogst plants?
Abundance of major plant taxa (fossil record). When a new taxon arises, it often increases rapidly in frequency and drives other taxa to lower abundance and extinction
Rise of Angiosperms 120mya caused a decrease in all other plant species
What is a resistance to extinction will depend on?
Geographical range / Dispersal
Physiological resilience
Rates of mutation - supplying genetic variation – adaptive potential
Population size
How can population size directly and indirectly resistance to extinction?
Directly - more to survive
Indirectly - larger populations create more mutations
What is the trend been for background rate of evolution?
Overall background rate of extinction is decreasing
What are trend for rates of origination?
Highest in early history - Cambrian explosion
Roughly constant thereafter
Peaks in rate of origination - massive spike after mass extinction
Why do mass extinctions cause rise in origination of species?
Probably due to the release in competition etc after mass extinction events
What is the Cambrian explosion?
massive adaptive radiation 530 mya
unexplained - perhaps due to the evolution of key morphological adaptations e.g. the eye, or increased oxygen in the water?
What are causes of origination and diversification?
Release from competition
Ecological divergence
Co-evolution
Provinciality / Vicariance
Environmental variability
Genome duplications - Polyploidy
What is an overview of release from competition?
Expansion into ecological space or vacant niches caused by finding new habitat, or extinction of another group of organisms
What is an overview of ecological divergence?
Evolution of key adaptations enables organism to exploit new ecological niche diversification of the group into new adaptive zones e.g. flight and sonar in bats
Ever greater partitioning of ecological resources
What is an overview of co-evolution?
Species interactions promote the evolution of diversity
Species serve as resources for other species e.g. Parasites and hosts
Figs and fig wasps
What is an overview of Provinciality / Vicariance?
Partitioning of biota among geographical regions into
provinces – with distinctive localised taxa
Plate tectonic processes change land mass distribution
Disjunct land masses and ocean systems
What is an overview of evironmental variability?
Range expansion/contraction - ‘Species pump’
Species retreat to refugia and when condition become faviourable they expand out again having undergone generations of ecosytems becoming new species
What is an overview of Genome duplications - Polyploidy
Allopolyploidy - hybridisation
Autopolyploidy - genome duplication
Often sterile –> haploid and diploid gamestes are not compatible
How do you calculate an overall increase in biodiversity?
Overall increase in biodiversity = = rate of origination of taxa – rate of extinction of taxa
What is the human impact on the future of biodiversity?
Population grew slowly until 19th century – then developments in agriculture, industry and public health triggered an exponential rise!
Use more than one third of primary production of land
What is an overview on human caused extinction preindustrial revolution?
Some large terrestrial species in prehistory.
Up to the 1900’s - habitat change and exploitation - caused the extinction of ca. 800 species.
What is an overview of the sixth mass extinction?
Post 1900 estimated that 30,000 species go extinct every year, many before they have even been described
What is an example of human caused extinction?
Introduction of Nile perch (Predation)
Lake Victoria cichlids – 500 species extinct
Why is this extinction event different than other mass extinction?
Humans caused it, rather than a single event like meteor
What are important things for conservation?
Genes, species, ecosystems and geographical regions
What is an overview of gene conservation?
Genetic diversity underpins adaptive potential e.g. hybridisation between related endangered and common species (genetic rescue?).
Even if a species disappears, its genetic variation persists, allowing future selection and adaptation to operate
What is an overview of species conservation?
Which species to conserve? Are all equal value?
What is an overview of ecosystem conservation?
Is it practical? How to prevent the loss of ‘keystone’ species?
What is an overview of geographical region conservation?
Which regions are important? Areas of endemism, refugial areas during climate change?
How can we measure conservation and biodiversity?
Needed to determine ‘where‘ to focus conservation action
Can we simply ‘count species’ at a location ?
Are all sites of equal value?
Do all species contribute equally to biodiversity?
We should quantify the relative values we attach to species. Vane-Wright et al 1991
Assign a value to a species’ ‘taxonomic distinctiveness’ or degree of ‘independent evolutionary history’ (IEH)
How much independent evolutionary history can we preserve?
If we choose at random
With topological information about phylogenetic tree
If we also have branch lengths for the phylogenetic tree
What is the overview of the IEH of the Tuatara (Sphenodon guntheri)
Iguana-like reptile - sole survivor of a group that flourished in the Triassic.
Currently two species on a few islets off New Zealand
Branched off reptilian phylogeny so long ago, almost a two species sub-class
If all reptiles are considered equal, it’s taxonomic distinctiveness = only 0.03%
More differentiation than between crocodiles and birds = 20% IEH !!!
Are such species/groups with high IEH evolutionary ‘dead-ends’?
Rare because the group lacks the ability to adapt?
What is an example of species/groups with high IEH but with a singlularly sucessful species?
Lagomorphs (rabbit, hares and pikas)
Most Genera with only one species (monospecific) are critically endangered but the European rabbit (Oryctolagus cuniculus) is highly successful
Which areas to focus on to conserve biodiversity?
Phylogeny
Rarity
What is phylogeny?
Phylogeny – maximise genetic or character diversity
What is an example of conservation of phylogeny?
African milkweed butterflies. Phylogeny derived from 217 phenotypic characters.
Branch lengths = number of character changes (vertical ticks).
Considering combinations of three species to conserve genetic or character richness
Most diverse set = niavius, echeria ,damocles, - have most differences between them.
What is the downside of determining phylogeny to maximise genetic diveristy
Very time consuming to do this for each family
What is a surrogate for gene richness?
When dealing with large numbers of species, species richness within families is a reasonable surrogate for gene or character richness
What is the relationship between number of higher taxa eg families and number of species in an area?
Positive correlation between the two
What is indicator taxa?
How good is species/family richness of one group for predicting the richness of other groups, or of entire biotas?
How good are species with indicating richness of other taxa?
Indicator relationships cannot always be assumed, - can be weak, absent or even negative
Different groups may differ in their habitat associations because different factors govern their distributions.
What is an example of two distantly related families not working to understand species richness?
UK butterflies and birds live in seperate areas and dont always overlap
What are the 2 conditions for rarity?
Rarity among areas (range-size rarity)
Rarity of individuals within areas (density rarity).
How can species rarity vary in different areas?
Species with restricted ranges do not always have low local abundances (and vice versa)
Bluebells - restricted range in Europe, but very common within Britain
What is endemism?
Condition of being restricted to a particular area
What is the distrubution of dragonflies in the UK?
Southern GB particually south east and North west highlands
What is rare quartile richness?
Species richness in the 25% of species most narrowly distrubuted
What is the rare quartile richness of dragon flies in uk?
South east of GB and North west highlands
What are biodiverse hotspots around the globe?
Amazon
Southeast asia eg malaysia
Caucases,
Central america
New Zealand
What is Intra-specific genetic variance?
Generated through mutation and subject to drift and selection, is the foundation of the evolutionary process by which biodiversity is generated
What is the priority of conservation
Genetic diversity - lowest level of this hierarchy.
Species are evolving lineages- their ability to evolve requires genetic diversity.
Hence, preservation of genetic diversity should be high priority in conservation programmes
What is the theoretical aim for conservation of genetics?
In theory we should aim to preserve as much existing genetic diversity as possible for future adaptive potential
