What do the different branch lengths on a phylogeny mean?
What do the different branch lengths on a phylogeny mean?
Answered in the following Video:
When it comes to how to read a phylogenetic tree, the branch lengths can mean very different things, depending on the phylogeny. On a Cladogram, the branch lengths are meaningless and they are only used to the distinguish relationships between the tips. On a Time Calibrated Phylogeny, the branch lengths correspond to units of time.
On a Genetic Distance Phylogeny, the branch lengths correspond to the degree of genetic differentiation between tips.
To know what type of phylogeny you are looking at, refer to the paper methods, figure caption, or axes to see what units they are in. Cladograms and Time Calibrated phylogenies typically have tips which align at the end, while genetic distance phylogenies tips do not align at the end. *NOTE If a phylogeny includes extinction, then the tips will not align on any phylogeny.
The most recent common ancestor is the furthest internal node that connects two or more tips/groups. You’ll often see Most Recent Common Ancestor abbreviated as MRCA. Heres an excerpt from our Reading Phylogenetic Trees course. See the full lesson ...
Alpha diversity describes the amount of diversity local to a specific area. Diversity is then contextualized using: species richness, which is simply the number of species species evenness, which is how equal are the abundances of each species ...
Scale counts Scale counts refer to the number of dorsal scales across a snake. This diagram from AROD.com.au shows the 3 different methods of counting the scales. You can either go across the body diagonally, up to the vertebrae and back down, or ...