Hydrobiologia DOI 10.1007/s10750-010-0546-7 SPECIATION IN ANCIENT LAKES Review Paper Scientific drilling and biological evolution in ancient lakes: lessons learned and recommendations for the future Andrew S. Cohen Received: 1 September 2010 / Accepted: 31 October 2010 Ó Springer Science+Business Media B.V. 2011 Abstract Scientific drilling to recover sediment Moreover, fossils allow calibration of molecular core and fossil samples is a promising approach to clocks, which are currently largely inferential. Lake increasing our understanding of species evolution in Malawi Drilling Project results provide some guide- ancient lakes. Most lake drilling efforts to date have posts on what might be expected in a drilling project focused on paleoclimate reconstruction. However, it for studies of evolution. The extreme variability in is clear from the excellent fossil preservation and lake level and environmental history that most high temporal resolution typical of lake beds that ancient lakes experience (exemplified by the Lake significant advances in evolutionary biology can be Malawi record) demonstrates that no one drilling made through drill core studies coordinated with locality is likely to provide a complete record of phylogenetic work on appropriate taxa. Geological phylogenetic history for a radiating lineage. Evolu- records can be used to constrain the age of specific tionary biologists should take an active role in the lakes and the timing of evolutionarily significant design of drilling projects, which typically have events (such as lake level fluctuations and salinity interdisciplinary objectives, to ensure their sampling crises). Fossil data can be used to test speciation and needs will be met by whatever sites in a lake are biogeographic hypotheses and flesh out phylogenetic ultimately drilled. trees, using a better-resolved fossil record to estimate timing of phylogenetic divergences. The extraordi- Keywords Ancient lakes Á Scientific drilling Á nary preservation of many fossils in anoxic lake beds Speciation Á Paleolimnology holds the hope of collecting fossil DNA from the same body fossils that improve our understanding of morphological character evolution and adaptation. Introduction Two central issues in the dynamics of speciation in ancient lakes are (1) the timing and (2) the environ- mental context of evolutionary events. The timing of Guest editors: C. Sturmbauer, C. Albrecht, S. Trajanovski & events determines rates and constrains models of T. Wilke / Evolution and Biodiversity in Ancient Lakes evolution. The environmental context can relate the evolutionary process to an extrinsic driver, such as lake & A. S. Cohen ( ) level fluctuations, water chemistry changes or other Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA ecological crises. This provides the most parsimonious e-mail: [email protected] approach to inferring evolutionary processes. 123 Hydrobiologia Scientific drilling of ancient lakes is a promising advantage of the drilling communities’ prior experi- means of collecting data on the timing of environ- ence in obtaining relevant environmental records and mental change (Brigham-Grette et al., 2007; Walton fossils from ancient lakes. et al., 2010). Data from drill cores can be used to evaluate hypotheses of when and why a particular lake has undergone major environmental changes, Drilling in ancient lakes with a precision and resolution that cannot be equaled by other means, such as outcrop-based, geomorpho- It may come as a surprise to many biologists logical or geophysical studies. Drill cores have the interested in ancient lakes that a relatively large potential to yield fossils of extinct and extant number of these bodies of water have been drilled, members of a clade under study, providing informa- primarily for paleoclimate studies. If we take as an tion about parts of the stem and crown in an arbitrary cutoff for ‘‘ancient lake’’ as any continental evolutionary radiation that would otherwise be water body whose history extends back in time at unavailable to us. In this respect, ancient lakes least 500 ka, then at least 15 such lakes have been, or represent unparalleled opportunities for integrating soon will be, investigated through scientific drilling. detailed geohistory information into evolutionary However, the drill core records do not extend back in studies in ways that are impossible for other model time half a million years for all of these (Fig. 1, systems of species radiations and extinctions, such as Table 1). Additionally, there are several dry basins in islands, caves, or mountaintop habitats. California that have been drilled, which until the Here, I present a brief review of how and where recent geological past held lakes, and which persisted drill cores have been collected in ancient lakes. I will for at least 500 ka. Finally, there are a number of consider some of the prior successes in applying sedimentary basins that have been both drilled and scientific drill core data to understanding lacustrine continuously cored (drilling is sometimes accom- speciation and extinction. Even lakes which lack plished without the collection of a continuous core), significant endemism today may have much to tell which contain the deposits of long-lived lakes of evolutionary biologists once a thorough history of the potential interest to evolutionary biologists for their lake is available; why species flocks are absent from endemic species flocks. some ancient lakes and present in others is a central question. Long core records can also provide a baseline for comparative biodiversity studies, for Why geologists drill lakes example for conservation purposes (e.g. Cohen, 2000). Finally, I recommend future scientific drilling Most of the extant ancient lakes shown in Fig. 1 studies focused on evolution that might take were originally drilled for the study of regional Fig. 1 Map of showing locations of all lakes/lake basins described in text. Numbers refer to list of lakes/basin in Table 1 123 Hydrobiologia Table 1 Ancient lakes that have been or will be drilled in the near future Lake name/location Lake age (Ma) Max. water depth Max. drilling depth Objectives Taxa observed in Key references (depth at deepest in meters below lake drill core sub-bottom drilling floor or oldest core target) at base (estimated age at base of drill core) Extant lakes 1. Bear Lake (USA) *6? 63 (51) 121 (0.22 Ma) Test of GLAD-800 Diatoms, Ostracodes Rosenbaum and system/regional paleoclimate Kaufman (2009), Bright (2009) 2. Clear Lake *0.65 18 (7.5) 177 (0.45 Ma) Paleoseismology and Diatoms, Ostracodes, Fish Sims (1988) (USA) paleoclimate 3. Great Salt Lake [5 Ma (but 10 (9) based on 121 (0.28 Ma) Test of GLAD-800/regional Ostracodes with L. Idaho Kowalewska and (USA) evidence for 1280 m shoreline paleoclimate affinities in selected Cohen (1998), dessication as intervals Balch et al. (2005) recently as Late Pleistocene 4. Laguna Potrok 0.77 Ma 100 (95) 101.5 (*85 Ka) Paleoclimate Zolitschka et al. Aike (Argentina) (2009) 5. Lake Baikal *25 Ma 1741 (1428 600 (*8.4 Ma) Paleoclimate Diatoms Colman et al. (Russia) m-discontinuous (2003), Horiuchi core) et al. (2003), Kuzmin et al. (2000), Kashiwaya et al. (2001) 6. Lake Khubsugul Pliocene? 262 (232) 52 (*1.05 Ma) Paleoclimate Ostracodes, Diatoms Poberezhnaya et al. (=Hovsgol) (2006), (Mongolia) Prokopenko et al. (2009) 7. Lake Biwa 4.5–5.0 Ma 104 (64 m at 1000 (lake margin), Paleoclimate Diatoms Horie (1984), (Japan) 200 mblf core site) *1.5 Ma; 200 TuZino (2010) (lake center) *0.5 Ma 8. Lake Bosumtwi 1.07 Ma 81 (74) 294 (lake sediments Paleoclimate and Koeberl et al. (2007) (Ghana) only) 1.07 Ma Impact Cratering Scholz et al. (2007) 123 9. Lake 3.6 Ma 170 (170) 315 (lake sediment Paleoclimate, Impact Brigham-Grette El’gygytgyn only) 3.6 Ma Cratering and et al. (2007) (Russia) Permafrost studies 123 Table 1 continued Lake name/location Lake age (Ma) Max. water depth Max. drilling depth Objectives Taxa observed in Key references (depth at deepest in meters below lake drill core sub-bottom drilling floor or oldest core target) at base (estimated age at base of drill core) 10. Lake Malawi [7 Ma (early Late 706 (593) 382 (0.5Ma?) Paleoclimate Diatoms, ostracodes, Scholz et al. ( 2006, (Malawi, Pleistocene cichlid and cyprinid fish 2007), Cohen et al. Tanzania, dessication) (2007) Mozambique) 11. Lake Qinghai Early Pleistocene? 28 115 m (1109 m at Paleoclimate Zhisheng et al. (China) (repeated on shore hole but (2006) desiccation) not all lacustrine). Age uncertain 12. Lake Titicaca 2.8 284 (235) 136 (*0.38 Ma) Paleoclimate Diatoms Fritz et al. ( 2007), (Bolivia, Peru) Lavenu ( 1992), Dejoux (1994) 13. Lake Van *0.8 Ma? 451 Drilling planned for Paleoclimate Litt et al. ( 2007) (Turkey) near future for 375 m (est 0.5 Ma) 14. Lake Ohrid 2–5? (poorly 288 Drilling planned for Evolutionary studies Albrecht and Wilke (Macedonia, constrained) near future and paleoclimate (2008) Albania) 15. Dead Sea Pliocene 308 (300) Drilling planned for Paleoclimate Stein (2001) (Israel, Palestine, near future for Jordan) 400 m (est. 0.6–0.8 Ma) Currently dry lakes 16. Owens Lake ? *5 Ma based on N/A (64 m when 323 (0.8 Ma) Paleoclimate Smith & Bischoff sed. thickness filled to spillway) (1997) 17. Searles Lake *5 Ma? N/A (197 m when 930 (3.2 Ma) Economic geology Phillips et al. (1983), filled to spillway) and paleoclimate Smith (2000) Ancient lakes with endemic faunas in ancient (extinct) basins 18. Paleolake Miocene- est. *380 m for 301 m (est. Paleoclimate Ostracodes Malde (1991), Idaho (USA) Pleistocene. Glenns Ferry lake *2.6 Ma) Thompson (1996) Hydrobiologia Glenns Ferry Phase *3.5-2.4 Ma Hydrobiologia Table 1 continued Lake name/location Lake age (Ma) Max. water depth Max. drilling depth Objectives Taxa observed in Key references (depth at deepest in meters below lake drill core sub-bottom drilling floor or oldest core target) at base (estimated age at base of drill core) 19.