Steve 3 Flashcards
Why does being a species matter
Definition can carry huge weight as to whether something is protected or not and how much resource is allocated
Are all species equal? Should we prioritise ancient and distinct genetic entities?
Important to have a robust definition bc protecting 90 species of birds of paradise is different than 40.
What is and isnt a species is continually changing based on newly gathered evidence. Better to remain open-minded and cautious (should always be cautious in conservation)
Biologists agree races and subspp are valuable biodiversity. Still cons proper spp focussed. Should we prioritise conserving a unique genus/family over another spp with many related spp?
Plus not all populations of a species play the same adaptive role eg difference in metal tolerance in plants. Those that are more could be important for revegetating landscape
Classification
Typological- changeless. Perfect type of a species, Early taxonomists viewed variation as unimportant. Sppm subspp, and races were considered discrete and invariant. Distinctiveness and fixity of spp were central features. Take one specimen and say THIS is it. Everything else that conforms is that species. Not v realistic bc variation. They dealt with variation by having subspecies and races. These groups would then be typified by an individual. Largely rejected by contemporary biologist
Population (evolutionary) view- focusses on variation within species. Groups of individuals possessing genetic, morphological, physiological, and behavioural variation. The basis of evolutionary change and adaptation. Aspect margin of variation that is used to describe what a species is.
Biological Species Concept
Also known as the isolation concept.
“Groups of actually or potentially interbreeding population that are reproductively isolated from other such groups”
Essential criteria is the reproductive isolation or the ability to reproduce and therefore exchange genetic material. Genetically based definition
Issues with the BSC
- difficult to determine reproductive isolation if not sympatric- so species often judged on surrogate criteria eg morphological measurements
- Taxonomists generally end up using morphology
- Problematic for asexual species, chronospecies, and groups eg plants can hybridise and genetic introgression is common (eg dandelions)
- If two groups never co occur how do you know if they could reproduce –> definition hard to test
What is the phylogenetic species concept
aka cladistic species concept
Argues classification should reflect the branching (cladistic) relationship between species, regardless of their degree of genetic relatedness. Relationships described in a cladogram. Presumably reflects actual evolutionary relationship and pathways.
A species is “the smallest diagnosable cluster of individual organisms within which there is a pattern of ancestry and decent”
So its groups of individuals that are genetically dissimilar from other groups. The species is an irreducible, or basal unit, distinct from other such units.
Adoption of PSC would result in the elevation of subspp to full spp in many groups and the recognition of even smaller groups species. Can mean species you thought were the same in different areas may be separate- all of which need protecting
How do species concepts affect conservation?
Northern swift fox and red wolf.
NSF was not considered a distinct species until recently in which case it needed urgent conservation action
Red Wolf turns out to be a hybrid of a coyote and a wolf- so we were spending conservation money on a hybrid that doesn’t need it. Less genetic value.
Alternatively- crested lark population is across 5/6 different groups. Have to look closely at variation across populations. Protecting one or 2 sites in the centre won’t protect full genetic diversity. Turkey
Regardless of concept, there is a need for the greater emphasis of variation within the species. Critical evolutionary and ecologically functional unit is not the species but the population. here 2 example highlight how conservation plans will differ if we attempt to conserve across all races rather than just spp - but if we use PSC then CL are species
Lots os species of dandelion have adapted for coping to some situation. They tend to self fertilise and not interbreed. Spp can be lumped into spp complex or treated separately.
Adding confusing to defining species
- Species may co-occur on wintering grounds but separate to breeding grounds.
- Sub-species/ races of crow may interbreed but given the option preferably mate with the same type
- Different forms of the same spp may have colour variation
- Ring species complex- small amount of interbreeding on periphery, Sometimes pop goes all circle and come back together and species full reproductively isolated eg gull species around sub arctic. Lesser black backed and herring gull come back together.
Models of speciation
- Allopatric- barrier causes reproductive isolation if 2 groups came together again wouldn’t reproduce
- Peripatric- spp enters new niche, niche is/becomes isolated. Repro iso
- Parapatric- spp enters new, adjacent niche. Develop in niche, repro iso
- Sympatric- genetic polymorphism within pop
Effects of environmental degradation on spp
Fragmentation normally only occurs over long periods of time. Humans fragment much quicker. Hummingbirds all different spp on Andes Mountain tops. Andes are relatively new mountain range. Hummingbirds evolved quite recently. Probably have similar genetics and have similar roles in ecosystem (pollination) so could potentially replace one with another. Are these as valuable as species with no other representatives?
Genetic drift rather than natural selection is often important
How many species?
10-50 mill
Only 1.5M named
So we protect areas we guess will have more. When you have one endemic often have others.
No idea really, estimates usually extrapolations from eg spp area relationships - as you increase area the number of species you find tends to incr in a non-linear way so can estimate how many more spp missing from a non-surveyed area. Fumigate small area, see how many new species and assume same for rest of area
Richness of higher taxa
Distinctiveness of evolutionary lineages is an important component of biodiversity. Higher taxa categories give an indication of lineages. By this measure marine»terrestrial biodiversity
Marine have 34 phyllo of extant multiple cellular organisms (out of 35), 16 exclusively so. But more effort goes into terrestrial world. eg platypus very genetically distinct but they don’t get prioritisation
EDGE- Evolutionary Distinct Genetically Endangered spp
eg long beaked echidna
Spp richness
No of species in a given area
Spp diversity
Takes relative abundance into account
