Question

What does the circled part of the phylogenetic tree above indicate?
A)an adaptive radiation 
B)a mass extinction event 
C)rapid speciation 
D)an adaptive radiation and rapid speciation 
E)evolution of eukaryotes

Accepted Answer

The circled part of the phylogenetic tree indicates both an adaptive radiation and rapid speciation. Adaptive radiation is when a single ancestral species diversifies into several new species that occupy different ecological niches. Rapid speciation refers to the occurrence of speciation at a faster rate than normal, resulting in a relatively large number of new species forming in a short period of time. The branching pattern in the circled area shows rapid diversification and branching of new lineages, indicating both adaptive radiation and rapid speciation have occurred.