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Tribute to Daniel Livingstone and Paul Colinvaux
INTRODUCTION
Many lakes in tropical Africa are known for their endemic fishes and for environmental histories that are preserved in the sediments beneath them. The topography of the West African tropics is generally less conducive to the formation of lakes than the East African rift region, but Lake Bosumtwi, Ghana, which formed after a bolide impact ca. 1 million yr ago (Koeberl et al., 1997; Peck et al., 2004), has yielded detailed records of late Quaternary climate (Russell et al., 2003; Peck et al., 2004; Shanahan et al., 2009). An additional 39 crater lakes of volcanic or phreatic origin occur in and around the highlands of western Cameroon (Kling, 1987). Lowland crater lake Barombi Mbo, also ca. 1 million yr old, is home to 11 endemic species of cichlid fish (Schliewen et al., 1994) and has yielded a detailed pollen record of climate and rain forest history spanning the last 33 ka (Trewavas et al., 1972; Cornen et al., 1992; Giresse et al., 1994; Maley and Brenac, 1998; Schliewen and Klee, 2004; Lebamba et al., 2012). The geochemical and microfossil records of Bosumtwi and Barombi Mbo represent the most widely cited paleoenvironmental histories in equatorial West Africa, and the endemic cichlids of Barombi Mbo have been the focus of intensive studies by evolutionary biologists (Trewavas et al., 1972; Schliewen et al., 1994, 2001; Schliewen and Klee, 2004; Martin, 2012; Musilová et al., 2014; Martin et al., 2015). However, other lesser known lakes from this region are also potentially informative.
One of those additional water bodies is Lake Ejagham, Cameroon (Fig. 1). Unlike most West African lakes, Ejagham is of enigmatic origin, and it supports two endemic radiations of endemic cichlids (Schliewen et al., 2001). Some sources have suggested that it is a chemical solution lake (Schliewen et al., 2001), but the late Daniel A. Livingstone (DAL) speculated (personal communication, 1985) with the first author that it may be a bolide impact crater, as is Bosumtwi. He collected two cores (EJ1 and EJ2) from the center of the lake in 1985 in order to reconstruct local climate history and investigate the environmental context for the evolution of the cichlids....