Explaining language change: an evolutionary approach Book

Croft addresses both the why and how of language change using the biological evolution as a metaphor. In his theory, linguemes -- lingustic structures embodied in utterances (constructions?) -- are replicators and speakers are interactos responsible for lingueme selection and propagation. Language change happens with any unconventional use; possible reasons for unconventional usage are social identity as well as under-/over- interpretation when analyzing form-function pairs. Being more familiar with the generative P&P approach to language change (e.g., Lightfoot) I learned a lot from this book although it seems that many ideas have been articulated before. One weak point is that, as far as I understand, there is no clear idea about how to adequately represent the network of linguemes (this is true for most construction grammar theories). E.g., at some point Croft mentions "activation propagation" among linguemes but does not give any example of how they are related to each other.