Historical Ecology in the Galapagos Islands: I. A Holocene Pollen Record from El Junco Lake, Isla San Cristobal

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Abstract
A pollen history of the Holocene of the Galapagos island of San Cristobal is described. Three cores, taken at different positions in El Junco lake, penetrated the 3 m of gyttja and underlying 12 m of red clay. Evidence of the hypsithermal interval was found in sediment stratigraphy and fossil remains of Azolla. Pollen diagrams are derived from the upper body of gyttja, which was dated from 10,170 .+-. 140 yr B.P. Plants growing near the lake provided much of the pollen, but there was a significant contribution from plants of other vegetation zones. The present-day vegetation surrounding El Junco is described in detail. The pollen record indicates that the vegetation of San Cristobal was stable for more than 9000 yr before settlement. Less than 1000 yr were needed to establish this vegetation at the start of the Holocene moist period. Pollen zones like those of Europe cannot be identified. Production of pollen on the Galapagos is so low as to suggest selection against anemophily. There was apparently no pattern of recurrent extinction and immigration as required by the MacArthur .ALPHA.MP Wilson paradigm.

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