Since the 1980s, agricultural economy has experienced a profound renewal through the process of territorial differentiation of production. In this perspective, Corsica got a Protected Designation of origin for the Brocciu cheese, as Sardinia for the Pecorino cheese, while Argan oil got a Protected Geographical Indication in Morocco. But are these 'product-leaders' actually hiding other forms of production behind them? The “basket of goods” theory helps to emphasize complementarities between several activities within a territory. Through this framework, we conducted research on by- products, also called joint products. Suckling lamb is a product derived from the main activity, dairy ewes and goats in the cases of Corsica and Sardinia, and argan oil in the case of Morocco. However, the relationships between these joint products present more competitive situations with the main product than real complementarity. This work is based on a PhD thesis in geography realized between 2011 and 2015 in these three regions. We aim to show, based on bio-technical dimensions associated with farming activities, how these relationships are taken into account and how they may be conflicting in a context of agricultural specialization. We approach the features of product certification as a potential vector of specialization where by-products could be excluded. We will develop these case studies further on and over wool as it offers a new perspective for craft products. Finally, our endeavour is to underline governance issues in the implementation of cross-sectoral coordination in contexts of strong social differentiation of the activities.