Much more work must be done to establish the impacts of habitat conversion to oil palm plantation on biodiversity.
http://plosone.org/article/info:doi/10.1371/journal.pone.0001572#article1.front1.article-meta1.abstract1.p1

We have published a paper on ant diversity in Malaysian oil palm plantations in Ecography:

Martin Pfeiffer, Ho Cheng Tuck, Teh Chong Lay (2008) Exploring arboreal ant community composition and co-occurrence patterns in plantations of oil palm Elaeis guineensis in Borneo and Peninsular Malaysia
Ecography 31 (1), 21–32 doi:10.1111/j.2007.0906-7590.05172.x

The abstract can be downloaded at http://www.blackwell-synergy.com/doi/abs/10.1111/j.2007.0906-7590.05172.x

In this extensive study arboreal ant diversity was investigated in about 1100 oil palms at two sites in Malaysia. The results were alarming. Altogether we sampled only 52 species of canopy ants, in both sites. Species estimators predicted 38 ant species for the site in Borneo, and 41 species for the site in Peninsular Malaysia, while the regional species pool in Borneo might exceed 420 species (Floren & Linsenmair 2005). Moreover 46 % of all species occurrences in oil palms (SOCs) belonged to 12 pan tropical tramp ant species, and at least four of these species were invasive (comprising 34% of all SOCs). Ten species (40% of all SOCs) were exotic ants from outside Malaysia.

Reference: Floren, A. and K. E. Linsenmair. 2005. The importance of primary tropical rain forest for species diversity: An investigation using arboreal ants as an example. Ecosystems 8:559-567doi: 10.1007/s10021-002-0272-8
http://www.springerlink.com/content/u072224311077422/?p=a536ca0a21fb431ea888fca1764e2243&pi=8