Determination of baseline ecological conditions in the humid highlands of Santa Cruz Island, Galápagos, Ecuador

Background/Question/Methods

The Galápagos Islands are renowned for their ecological value. However the native biodiversity of this unique region is under threat. This thesis examines and disseminates ecological baseline conditions for the humid highlands of Santa Cruz Island in the Galápagos Archipelago. The aim of the study was to distinguish temporal vegetation transitions within the highlands, identify potential drivers of the transitions, and evaluate the importance of these transitions to conservation and management practices. Furthermore, the study aimed to develop baseline conditions within the soil microbial communities, examine relationships between testate amoebae (Protozoa) and environmental variables, and evaluate the functional diversity of these communities across the highlands. Utilization of palaeoecological proxies including macrofossil analysis, applied to three sediment sequences collected from Sphagnum peat bogs in the highlands of Santa Cruz Island, provided the basis for vegetative reconstructions during the Holocene. Examination of surface samples from differing substrate types and micro-habitat types was employed to evaluate the testate amoebae communities.

Results/Conclusions

The results indicate that these specialized highland ecosystems are relatively young dynamic communities and have undergone considerable changes in vegetation composition, transitioning from diverse hygrophilous herbs and submerged aquatic lake communities to drier fern-sedge-Sphagnum bog systems during the last 10,000 yr BP. A new aquatic genus previously undocumented on the islands, Elatine sp., was discovered at two of the study sites. Additionally, this study confirmed native status of seven plant species once considered introduced or doubtful native species. Results indicate that some of the observed vegetation successions may have been driven by climatic shifts, and recent anthropogenic change. This study helps reveal patterns of change in the humid highlands over the last 10,000 years BP regarding vegetation variability, climatic shifts, influence of fire and anthropogenic impacts on the island. This study also provides insight into testate amoebae community structure and ecosystem function across the highlands.