Panthera is a taxonomic genus within Felidae, including the lion, Panthera leo, and the tiger, Panthera tigris. It is distinct from Felis, the taxonomic genus containing the domestic cat. A genus groups related species; membership does not make those species ecologically or behaviorally interchangeable.[ref]
Living cat species by the IUCN SSC Cat Specialist Group. Panthera lineage and Domestic Cat lineage: genus assignments and scientific names
Molecular comparisons show why reconstructing those relationships is more interesting than sorting animals by appearance. A genomic study compared single-nucleotide polymorphisms, other nuclear markers and mitochondrial sequences across living Felidae. Different parts of their genomes did not always support the same branching history, and the authors found evidence consistent with ancient hybridization among some lineages.[ref]
Phylogenomic evidence for ancient hybridization in the genomes of living cats (Felidae) by Gang Li and others. Abstract: marker comparisons, phylogenetic discordance and historical hybridization
For an illustrative reasoning exercise, suppose two gene regions support different phylogenetic trees. One must examine processes that can generate that disagreement rather than select a tree merely because the corresponding animals look alike. A named taxonomic genus summarizes a classification; individual gene histories supply evidence that can complicate a simple picture of wholly separate ancestry.
New to topics? Read the docs here!