Anagenesis vs. Cladogenesis

Anagenesisnoun

The evolution of a new species by the large scale change in gene frequency so that the new species replaces the old rather than branching to produce an additional species.

Anagenesis

Anagenesis is the gradual evolution of a species that continues to exist as an interbreeding population. This contrasts with cladogenesis, which occurs when there is branching or splitting, leading to two or more lineages and resulting in separate species.

Cladogenesisnoun

(genetics) An evolutionary splitting event in which each branch and its smaller branches forms a clade

Cladogenesis

Cladogenesis is an evolutionary splitting of a parent species into two distinct species, forming a clade.This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, opening up ecological niches for the survivors and causing population bottlenecks and founder effects changing allele frequencies of diverging populations compared to their ancestral population. The events that cause these species to originally separate from each other over distant areas may still allow both of the species to have equal chances of surviving, reproducing, and even evolving to better suit their environments while still being two distinct species due to subsequent natural selection, mutations and genetic drift.Cladogenesis is in contrast to anagenesis, in which an ancestral species gradually accumulates change, and eventually, when enough is accumulated, the species is sufficiently distinct and different enough from its original starting form that it can be labeled as a new form - a new species.