cladogenesis

Cladogenesis is a mode of evolution in which a lineage splits into two or more genetically distinct descendants, increasing the diversity of life. It contrasts with anagenesis, in which a single lineage changes over time without branching.

Cladogenesis typically requires reproductive isolation between diverging populations. It can occur through various modes that reduce or halt gene flow: allopatric speciation due to geographic barriers; peripatric speciation with a small founder population at the edge of a range; sympatric speciation within the same geographic area often driven by ecological niche differentiation or chromosomal changes (polyploidy in plants); parapatric speciation where ranges are adjacent and gene flow is limited.

Evidence for cladogenesis comes from phylogenetic trees showing branching patterns, the fossil record, and comparative molecular data. Its study helps explain the origin of higher biodiversity and informs taxonomy and systematics.

Classic examples include the adaptive radiation of Darwin's finches in the Galapagos and cichlid fishes in African lakes, where rapid branching has produced many species from a common ancestor. Rate and mode of cladogenesis vary across taxa and environments, with some lineages exhibiting rapid bursts and others accumulating diversity more gradually.