IPA: /əˈsɔːtəˌtɪvli/
KK: /əˈsɔrtəˌtɪvli/
In a manner that involves grouping or selecting based on similar characteristics or qualities.
The species in the study were assortatively paired based on their size.
Assortatively → It is formed from "assort" (from Old French *assortir*, meaning to sort or arrange) and the suffix "-ively" (meaning in a manner). The word "assortatively" means in a manner that involves sorting or arranging things based on certain characteristics.
Think of sorting things based on their characteristics — that's what 'assortatively' means, as it describes doing something in a way that involves arrangement.