Note disjoint trees as nuance of exact phylogeny

docs/context.md

@@ -4,8 +4,9 @@ There are certain quirks associated with real-time phylogenies that you might no
 
 - **Multifurcations are real**: In phylogenetic reconstructions, there is usually an assumption that any {term}`multifurcation/polytomy` (i.e. a node that has more than two child nodes) is an artifact of having insufficient data. In real-time phylogenies, however, we often observe multifurcations that we know for sure actually happened.
 - **Not all extant taxa are leaf nodes**: In phylogenetic reconstructions, there is usually an assumption that all extant (i.e. still living) {term}`taxa` are leaf nodes in the phylogeny (i.e. none of them are parents/offspring of each other; similar taxa are descended from a shared common ancestor). In real-time phylogenies it is entirely possible that one {term}`taxon` gives birth to something that we have defined as a different taxon and then continues to coexist with that child taxon.
-- **Not all nodes are branch points**: In phylogenetic reconstructions, we only attempt to infer where branch points (i.e. common ancestors of multiple taxa) occurred. We do not try to infer how many {term}`taxa` existed on a line of descent between a branch point and an extant taxa. In real-time phylogenies we observe exactly how many taxa exist on this line of descent and we keep a record of them. In practice there are often a lot of them, depending on you define your taxa. It is unclear whether we should include these non-branching nodes when calculating phylogenetic statistics (which is why Phylotrackpy lets you choose whether you want to).
+- **Not all nodes are branch points**: In phylogenetic reconstructions, we only attempt to infer where branch points (i.e. common ancestors of multiple taxa) occurred. We do not try to infer how many {term}`taxa` existed on a line of descent between a branch point and an extant taxa. In real-time phylogenies we observe exactly how many taxa exist on this line of descent and we keep a record of them. In practice there are often a lot of them, depending on how you define your taxa. It is unclear whether we should include these non-branching nodes when calculating phylogenetic statistics (which is why Phylotrackpy lets you choose whether you want to).
+- **Disjoint trees are possible**: Unlike reconstructed phylogenies, which typically trace biological organisms back to a shared common ancestor (i.e. "Last Universal Common Ancestor" aka LUCA), lineages in real-time phylogenies may instead trace back to independent founding ancestors (i.e. at the beginning of a real-time tracking window). In the case of artificial systems, disjoint lineages may, in fact, correspond to true independent origins (e.g. with randomly-generated initial populations).
 
 ![An example of a full digital evolution phylogeny](images/FullPhylogeny.png)
 
-The above image represents an actual phylogeny measured from digital evolution. Each rectangle represents a different taxon. It's position along the x axis represents the span of time it existed for. Note that there are often sections along a single branch where multiple taxa coexisted for a period of time. Circles represent extant taxa at the end of this run.
+The above image represents an actual phylogeny measured from digital evolution. Each rectangle represents a different taxon. Its position along the x axis represents the span of time it existed for. Note that there are often sections along a single branch where multiple taxa coexisted for a period of time. Circles represent extant taxa at the end of this run.