True or false? The last ice age produced many different species mainly because populations dispersed and colonized new habitats.

False. The species emerged during ice age were due to vicariance events.

Explanation:

There are different types of speciation. Allopatric speciation consists of the geographic separation of a continuous genetic background so that it can give place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flux, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.

When a geographical barrier emerges, this is known as a vicariant event. Vicariance is the geographical separation of a population imposed by discontinuities in the physical environment that divides populations that were originally continuous. The process of vicariant allopatric speciation involves different steps:

The emergence of the barrier. There is a spacial separation that divides the different populations in an area. These separations might be due to migration, tectonic plate, glaciation, among others. In the case of the ice age, the barriers were the glacial formation and retraction of the sea and ocean water. Interruption in the genetic interchange. The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation. Genetic divergence by natural selection and reproductive isolation, which makes it impossible for the two groups to mate even if the barrier disappears. Prezigotic isolation mechanisms favored by selection once it occurs a secondary contact between the new species in formation.

Glaciation is one of the most important drivers of speciation and production of different phylogeographic structures by vicariance. Glacials originate isolated gene-pools that accumulate differences that end in reproductive isolation.