trees

the alternative dna sequence of a gene

when a species carries two or more haplotypes of a given gene

phylogeneic tree showing evolutionary relationships among haplotypes

phylogenetic tree without a root, showing more similar species closer to each other than to more different species, no nodes

homplasy is common and there could be several trees

can occur relatively fast without leaving enough evolutionary time for intermediate ancestors to aquire distinct synapomorphies, makes node difficult

may not agree with species phylogenies because of incomplete lineage sorting

between closely related species may obscure their true phylogenetic relationship which may result in a reticulated (netlike) tree

possibly mediated by viruses that transfer a few genes of one species into the genome of another species

A speciation event is defined as the dichotomous branching of one ancestor species into two new species (a dichotomy). When a phylogeny is not resolved entirely, it may contain unresolved nodes with three of more new species radiating from one ancestor (sometimes referred to as a “star phylogeny”. Such a star phylogeny may suggest a very “rapid” burst of speciation, at the scale of geological time.