Biodiversity and Social Networks...

Exchange networks (not sure what you mean by exchange networks) play a key role in agrobiodiversity through conservation of and preserving local plant varieties. However, exchange patterns of germplasm can change, as economies and livelihoods are changing throughout history. but At the same time, those patterns are telling tell us something about the cultural domain, which drives the conservation of agrobiodiversity despite monetary economy   economic pressures. The way households exchanges plants and seeds, shapes germplasm selection, transmission and conservation even in urban context where those processes are commanded by commercial interests.
Mexico has a long tradition of small scale food production. This tradition is preserved and demonstrated in the domestic space, because the houshold garden's main purpose is to produce food for the not for market but for covering some family, feed needs not for the market.
Urban gardens in San Cristobal de las Casas in Chiapas Mexico have a long history, and have been enriched heritage from by the contrubutions of diverse ethnic groups. First, originarian indiginous people whom developed native crops; then colonial settlers whom carried several crops and cattle species from Spain; and even now by immigrants to in these days, people that comes to San Cristobal from different Mexican regions, and from different regions around the world, contributes to urban agriculture with several their varried vegetable seeds and farming practices.

In order to determine if these three distinct groups (outside Mexico; other parts of Mexico, and people whose families who have lived in San Cristobal for generations) maintain their seed varieties, their agricultural knowledge and other exchanges with each another on urban gardens (I don't understand what this means, we conduced a study in downtown San Cristobal downtown. The sudy included a cluster analysis and a social network description. Information was obtained from semi structured interviews (n=38) carried out from February to May 2012.
Inputs (from the urban garden) exchanged by these three groups were similar (I don't understand this-do you mean that the three groups had similar gardens or similar things to say about their gardens or something else?)  but some of their practices were not. People tended to exchange farming inputs (Inputs is a confusing word here.  Do you mean seed selection, information, proceedures, all of these, something else? with members of their own group. Network analysis indicates five components making up the exchange network found. According to these findings people tended to exchange knowledge first and seeds second.
So, downtown San Cristobol holds a rich seed and knowledge pool, however the access to that pool seems to be limited by social patterns of exchange, which allow seed, plant and knowledge to be localized in a certain social spaces apparently determined by social groups. to which one belongs.