For C. flavidorsalis I would suggest:

Hasbún, C. R. (2001). Herpetofaunal Biodiversity of the Endangered Spiny-Tailed Lizards of the Ctenosaura quiquecarinata/flavidorsalis Complex: Geographic Variation, mtDNA Phylogeography and Systematics. Unpubl. Unpubl. Ph. D. diss., University of Hull, Hull, UK. Google Scholar.

Ctenosaura in general

Hasbún, C. R. (2001). Additions to the description of Ctenosaura flavidorsalis Köhler & Klemmer 1994 and its occurrence in southern Honduras, El Salvador and Guatemala (Reptilia, Squamata, Iguanidae). Herpetozoa, 14(1), 55-63.

C. macrolopha

Goldberg, S. R. (2009). Note on reproduction of the Sonoran Spiny-tailed Iguana(Ctenosaura macrolopha)(Squamata: Iguanidae). Bulletin of the Chicago Herpetological Society, 44, 42-43.

I am not aware of any study specifically on their ecology, but I'd like to know too.

As a starting point you could go to Giant Lizards: The definitive guide to the natural history, care, and breeding of monitors, iguanas, and other large lizards by Sprackland (TFH Publications, NJ). There are species accounts and numerous references.

General information and references on Ctenosaura available from this source (action plan for C. bakeri): http://www.zoocentral.dk/uploads/4/9/7/5/49755431/utila-spiny-tailed-iguana-ctenosaura-bakeri.pdf

You also may consult the IUCN's Iguana Specialist group, https://www.iucn-isg.org/wp-content/uploads/2013/03/Iguanas_of_the_World_Checklist_v2011-2.pdf