Insights into trophic competition between Pink and Yellow Galapagos Land Iguanas

Interspecific resource competition essentially refers to the occurrence of different species competing for resources, where one species increases in density whilst another decreases due to competition for limiting resources. One such type of resource competition is known as trophic competition and occurs when the two interacting species compete for the same trophic resource. This might lead to dietary shifts, resource partitioning and, in the worst-case scenario, the local extinction of the outcompeted species. This scenario might occur to any species sharing the same ecological requirements, but when two species are phylogenetically similar, this process might be exacerbated. The critically endangered Pink Galapagos land iguana (Conolophus marthae) and the vulnerable Yellow Galapagos land iguana (C. subcristatus) are syntopic and both phylogenetically and morphologically similar. However, trophic competition between these two species is for the most part unknown. In this study I show that there is potential trophic competition between these two reptile species. Through morphological assessment of fecal samples collected in the known habitat of C. marthae I conclude that there is a large dietary overlap, with no significant indication of resource partitioning between the species. I could also conclude based on the plant specimens collected in close proximity to the iguanas and identified through DNA sequencing, that there are no obvious microhabitat differences between the species. Previous work based on stable isotope analysis partly contradicts this lack of resource partitioning, but these studies reflect a longterm assessment whilst morphological dietary investigation reflects a much shorter time frame. As expected, resource competition can potentially occur between these two species but more studies regarding their microhabitat and diet are required for future safeguarding of the Pink Galapagos land iguana.