An analysis of modern pollen representation and climatic conditions on the Galápagos Islands

Abstract

In the first modern pollen trapping study conducted in the Galápagos Islands, 58 clusters of pollen traps were established on four islands: Genovesa, Rocas Bainbridge, Santa Cruz, and San Cristobal. HOBO data loggers collected temperature, humidity, and dew point every 30 min for 1 year at eight locations. The trapping locations were selected to provide a wide diversity of Galápagos habitat types and to support active or future analyses from bog and lake core records recovered from the islands. Pollen influx to the traps was generally low (<100 grains/cm ² per yr), but broad habitat types were clearly identifiable based on the pollen collected. More precise identification of trapping sites and vegetation zones within the islands were identified using ordinations of the pollen and climate data. Long-distance dispersal from the mainland and neighboring islands were found to be significant elements of pollen records, particularly those where local pollen production was low (<150 grains/cm ² per yr). Over-representation and under-representation of ecological dominants was documented, as was the significant representation of invasive exotic species in some settings. Temperature and relative humidity data were used to reconstruct the presence of ground-level cloud (garúa). Garúa caused substantial cooling, beyond what would be expected from adiabatic lapse rate, in the highlands. The cloud formation associated with garúa caused low-elevation temperatures to be cooler than maximum sea-surface temperatures. The data emphasize the importance of garúa to the endemic flora of the islands and their long-term conservation.