Meet Alpha, the Canadian dealer's latest, greatest attempt to keep a good thing going in equity trading. Alpha was launched this morning as an alternative trading system or ATS that links the biggest players in the domestic market. The key word here is domestic: The founding member of this ATS does not include the global dealers that are winning an increasing share of trading in stock, particularly those that are inter-listed on Canadian and U.S. exchanges. This is a defensive move by the locals, and if they can create enough stock trading in Alpha. If the founders can draw enough stock trading, with minimal market impact and low cost, then it's a strong defensive move. Alpha's backers are BMO Nesbitt Burns, Canaccord Capital Corporation, CIBC World Markets, National Bank Financial, RBC Dominion Securities, Scotia Capital and TD Securities. These seven dealers have built lucrative franchises trading Canadian stocks, and now they have shown how they intend to protect their turf. These dealers all recognize that at least one ATS is going to emerge as a rival to the Toronto Stock Exchange. However, most experts agree that in the relatively small Canadian market, only one ATS is likely to thrive. Several networks are bidding for this prize. The seven Alpha dealers have clearly decided that since they control the bulk of domestic trading, they will dictate which ATS gets the patronage of investors, and they will own a piece of the action. Alpha's seven founding dealers said in a press release today: "The new trading system will be open to all dealer institutions who want to join as participating organizations." If the Alpha system works as advertised when launched next year, with the Canadian dealers pushing big volumes of stock through the network, then rivals will have no choice but to join. Rival ATS concepts woke up today to a dramatically different competitive landscape. For the TSX, and for domestic upstart Pure Trading and ventures by Bloomberg LP and Instinet, there is simply not enough stock trading to go around.