plosone-phylo
Figure 1
The sampling and differentiation of lineages impacts the potential to resolve clades.These diagrams depict how patterns of morphological differentiation and sampling of ancestors impact the distribution of potential synapomorphies and thus the intrinsic capability to resolve clades with morphological data. In (a), as there is no morphological change over the duration of the ancestral taxon A, there can be no true synapomorphies which would unite any pair of the sampled taxa (ancestor A or its descendants B and C) to the exclusion of a third. In (b), the taxa with a dashed outline (taxa A and B) have not been sampled and are not included in the supposed cladistic analysis. However, even though A and B are ancestral, the sampled taxa are all descended from the same persistent ancestor and thus no synapomorphy exists to produce an additional nested clade. This causes the node to be intrinsically unresolvable. In (c), under a bifurcating cladogenesis pattern, polytomies are only produced when the ancestor A is sampled, as each morphotaxon can only have two descendants. The fourth example (d) is an example with cryptic cladogenesis and anagenesis, where the formation of several sampled descendants from a cryptic ancestral complex of multiple undifferentiated lineages produces an unresolvable set of relationships. The taxa in (d) labeled A1, A2, A3 and A4 are undifferentiated cryptic lineages, which would be identified as a single morphotaxon ‘A’ for the purposes of taxonomic assessment and phylogenetic analyses.
Figure 1
The sampling and differentiation of lineages impacts the potential to resolve clades.These diagrams depict how patterns of morphological differentiation and sampling of ancestors impact the distribution of potential synapomorphies and thus the intrinsic capability to resolve clades with morphological data. In (a), as there is no morphological change over the duration of the ancestral taxon A, there can be no true synapomorphies which would unite any pair of the sampled taxa (ancestor A or its descendants B and C) to the exclusion of a third. In (b), the taxa with a dashed outline (taxa A and B) have not been sampled and are not included in the supposed cladistic analysis. However, even though A and B are ancestral, the sampled taxa are all descended from the same persistent ancestor and thus no synapomorphy exists to produce an additional nested clade. This causes the node to be intrinsically unresolvable. In (c), under a bifurcating cladogenesis pattern, polytomies are only produced when the ancestor A is sampled, as each morphotaxon can only have two descendants. The fourth example (d) is an example with cryptic cladogenesis and anagenesis, where the formation of several sampled descendants from a cryptic ancestral complex of multiple undifferentiated lineages produces an unresolvable set of relationships. The taxa in (d) labeled A1, A2, A3 and A4 are undifferentiated cryptic lineages, which would be identified as a single morphotaxon ‘A’ for the purposes of taxonomic assessment and phylogenetic analyses.