This will happen if the two populations diverge genetically so that either their appearance or their behaviour changes. Once differences have built up which prevent interbreeding the two populations have become two different species.
Increased immigration can lead to a larger population by adding more individuals to the existing population. This can result in higher birth rates due to increased availability of potential partners and greater genetic diversity.
This is known as assortative mating, where individuals choose partners based on specific traits that are heritable. This can lead to the reinforcement of those traits within a population over generations.
The population of Guggenheim Partners is 2,200.
Elevation Partners's population is 20.
Apax Partners's population is 100.
Reading Partners's population is 130.
The population of Lexington Partners is 60.
AlpInvest Partners's population is 115.
AlpInvest Partners's population is 2,010.
MDC Partners's population is 6,561.
Giuliani Partners's population is 2,008.
The population of Giuliani Partners is 2,010.