Biogeography 2. Analysis Flashcards
For biogeography studies you need information on what 3 things
–> form, space, and time
Define vicariance
the splitting of lineages (cladogenesis) caused by division of the range of a taxon by formation of a barrier
–> so formation of barrier causes the speciation event
Define dispersal
extension of range of a species beyond an existing barrier
–> so barrier exists before the dispersal event
What theory coincides with the rise of phylogenetic systematics (cladistics)
- plate tectonic theory
–> the splitting of the continents seemed to provide an explanation for the splitting of lineages
How do you do an area cladograms
- modern cladistics biogeography uses this
- you start with the species cladogram and then convert to area cladograms by replacing species with areas
General area cladogram relies on what concept
it relies on concept of biogeographic homology
- compatibility of cladograms helps resolve biogeographic history by showing generalized patterns
describe comparative biogeography
- panbiogeography, general area cladograms
- look for the common patterns among independent cladograms (area cladograms from taxon cladograms)
–> BUT not knowing the timing of events can lead to false appearance of congruence (pseudocongruence) or false appearance of incongruence (pseudo incongruence)
- dispersal/extinction can add noise in general
area cladograms anytime
Which signal is stronger: the vicariance signal or the dispersal/extinction noise
- most assume the vicariance signal is stronger than the dispersal or
extinction “noise” (it helps if the latter are random)
Which islands show clear dispersal scenarios early in phylogenies
- hot spot island chains allow clear dispersal scenarios
- Hawaiian Islands provide a classic example, the western islands are older and have more ancient lineage - dispersal is the favored model with these islands
Explain fossils as a test of vicariance scenarios
- looking at distributions of extant taxa only gives a partial picture of biogeographical history
- adding fossils can make a big difference to the preferred hypothesis
- for example when you look at just the living species you miss out on things, but if you add fossil lineages that can give more information
Give an example of a land bridge and major faunal dispersal
- The great american interchange: Late Pliocene, ca. 3 mya
- NA has 29 (21&) of mammals from SA
SA has 85 genera (50%) of mammals from NA
–> mammals of SA replaced by NA taxa, some of them only gradually
ex. porcupines, and sloths
Explain the lungfish example
- is about reconciling vicariance conflicts
- fossils were added and an area cladogram was made
- it suggested that vicariance events occurred due to break up of gondwana
- the problem is the wrong sequence of continental splitting events
What did Enghoff and Sanmartin’s studies of holarctic taxa find
When they did a general cladogram based on phylogeny of younger taxa and a general cladogram based on phylogeny of older taxa they found that there were different vicariance timings being indicated
What is phylogeography
this is biogeography at the level of closely related species and subspecies
–> it is based on mtDNA alone, and mtDNA is maternally inherited in most animals
So what are some explanations for current distributions, which are not necessarily exclusive
- Dispersal: long-distance vs range expansion
- Vicariance: panbiogeographic vs modern cladistic
- Extinctions
- Incorrect phylogeny
- Gene phylogenies vs species phylogenies
- Systematic errors like long branch attraction
- Barriers: mountains, deserts, seas, etc.
- Filters; Island hopping
- Centers of origin; Refugia
- Glaciations; Global sea level rise and fall
- Plate tectonics:
- continental splitting
- continental collisions or reunions
- hot spots and island arcs
