Assuming the tiles are 12mm thick, each one weighs in at 7.2Kg, per Sq Mtr that is 30Kg, you need to add adhesive and grout to the calculation at approx 4Kg per Sq Mtr.
Plasterboard can take 32Kg/Sq Mtr unskimmed, so i would suggest VERY borderline.
If tiles are 10mm thick then 25Kg per Sq/Mtr + 4Kg addy and grout then no problem.
We need to know the thickness of the tiles, to calculate accurately.
The board will need to be mechanically fixed, and if in a wet area tanked, your other option would be celotex between the studwork, and then AquaPanel or another cement based 12.5mm tile backerboard. This does not need tanking and will take up to 50Kg per Sq/Mtr.
Make sure you use a quality bagged trade adhesive and grout the stuff they sell in the sheds will not be suitable.
Travertine also needs sealing twice BEFORE installation, and again afterwards, i would also suggest you use white adhesive to stop any possibility of the adhesive bleeding through the stone.
Read the sticky at the top of the page, and do a search on here, this subject has been covered many times, and whilst i am not a professional tiler, i have learnt a lot from the site. All of the above information comes from here.