biogeography and speciation Flashcards
Biogeography
The sicence devoted to dcoumenting spatial patterns of biodiversity
The study of distributions or organisms in both the past and present
of the 1.5 milion names naimals they are less than 20% of extant animals and less than 1% of extinct aniamls
Speciation
The process that produces new and distrinct life forms
Evolution can be about speciation, teh engine that generates biodiversity
Biological Species Concept
Species are groups of actually or potentially interbreeding populations that are reproductvly isolated from other such groups
reproductive isolation is defining charcteristic of species
The problem with this is hybrids - they interbreed and from viable offpsring but they are usually infertile
Cant always be used beacsue expensive or some species might not breed in the trials
Morphospecies concept
Topological species cocnept
Members of the same species usally look alike
Not accurate so we rely on geentic testing
Some things can only be named species through this method like dinosaurs
Consider things like cryptic species which look the same but dont breed with eachother - but have gentic differences
Hybrids
Species that are morpholgically distinct form independt populations but can still interbreed would be consideed the same species under the BSC
this presents prob to BSC
Other Concepts for species
Biological species concept tells us the mechanism of speciation - reproductive isolation
Species characterized by niche (the range of envirmntal variables occupied by a species)
Two species that coexist in the same location will drive one to extinction is there is too much overlap in their niches due to competition
This led to ecolgical niche concept: a one to one correspondce between a species and niche (not rlly true)
Phylogentic species concept: memebrs of a species all share a common ancestry and common fate - a species is defined as a monophyletic group - no a priori assumptons abt population structure
Prezygotic and Post Zygtoic isolation factors
○ Prezygotic factors:
§ Geographic: indivduals are seperated in space
§ Ecolgical: indivduals are separated by habitat or other ecological specilization
§ Temporal: indivduals are reprodcutvly active at diff times
§ Behavioural: indivduals mate with others based on specific corutship rituals, songs or displays
§ Gametic: gametes are infompatble and cant fuse to form a fertalized egg
§ Mechanical: indivduals are unable to mate
○ Postzygotic factors:
§ Hybrid inviability: embry forms but doesn’t fully develop
§ Hybrid sterility: offspring are prodcued but are sterile
Allopatric
Speciation can occur through creation of allopatric (diff places) populations - species speciate because they are seperated into two geographic areas - physical seperation of species
Physical sepration doesnt create allopatric populations immediatly - its a gradual process - it can give rise to subspecies where there are distinct traits that have accumulated
Vicariance
(form of allopatric)
A geographical speration of a population typically by a physical barrier like a mountain range or river, resulting in a pair of closely related species
ex. ismus of panama and the snapping shrimp - their closest related sister taxa are just across the ismus
Dispersal and peripatric speciation
(form of allopatric)
Dispersal - where indivduals colonize a distant place/isaldn is a prominent example
imprtant as a specific kind of allopatric speciation known as peripatric speciation ( a small group of the orgnal poplation founds a new population through dispersal)
Darwins finches are an example of peripatric speciation - yet allopatric speciation played a role in geographic isolation
Sympatric Speciation
Same geographic place speciation
When a population is driven by diff seletive pressures - disruptive selectionforces them apart - more and more changes and if disprutive selection is long lasting then it can lead to speciation
Instantaneous speciation is a form of sympatric - it happen in polyploidization - something with the genes duplicating to be a diploid instead of haploid sex cells
Plate Tectonics
Pangaea broke up 180m years ago
South america and afric seprated 125 m years ago
Vicariance played a factor in how organisms were split up in teh world
Populations existed together before speraton so now similar animals on seperate continents
Ex. Ratite birds are flightless birds and apart from kiwi are long necked and long legged - found in south america, australia and new zealand
Isthmus of Panama
rising of asthmus of panama was terestrial dispersal (large groups moving) event and marine vicariance (phsyical barrier) event
South america was islated until panamanian isthmus
Terrrestrial species could now move
presents prob of opssoum and possum
more animals went from NA to SA and less from SA to NA
