Hi Ravi, Most likely you will have to dig into the literature--I don't know if much would be available open access online.  The book "Annotated Bibliography of Mascarene Plant Life" (Lorence & Vaughan,  1992) is a good place to start (copy should be available in MSIRI library, or order through National Tropical Botanical Garden: : http://ntbg.org/programs/research-publications.php). Also,  Rouillard & Gueho published a series of plants of horticulural, medicinal, & economic interest in the Rev. Agric. Suc. Ile Maurice 1981-1986.  Flore des Mascareignes family treatments often lists dates of introduction of exotic species.

I agree with David in that you won't be able to find very much in open access sources. For Rodrigues, try the Plant Red Data Book for Rodrigues by Wendy Strahm1989. I know there is a checklist of introduced plants, but can't remember if there are introduction dates associated with the names and descriptions. Otherwise, you might need to read the papers by Balfour, Leguat and other early naturalists to get this information. I know the University of Mauritius holds copies of many of these early works - perhaps the librarian can help you with this.

Thank you David Lorence and Alexsandra Maljkovic.

Indeed I consulted these suggested publication and I was able to get some of the information I needed.

Regards