insightlmu RESEARCH I s s u e

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1 insightlmu RESEARCH Issue LIFE SCIENCES SUSANNE WEDLICH HIDDEN TREASURES The domestication of the donkey, the genetic diversity of the cheetah and the ancestry of the cucumber. A pretty heterogeneous list but the projects being pursued by the palaeoanatomist Professor Joris Peters and the botanist Professor Susanne Renner do have one thing in common. None of them would be possible without the many unique and irreplaceable specimens in the Bavarian State Collections of Natural History. And there is little doubt that the keys to many other scientific mysteries are slumbering in the storerooms. Maximilian III. Joseph, Prince-Elector of Bavaria, is known to history as The Well Beloved. Schoolchildren might quarrel with the epithet (it was he who introduced compulsory education to Bavaria), but scholars and scientists have reason to be grateful to this scion of the Wittelsbach family. For, in 1795, Maximilian III. Joseph founded the Bavarian Academy of Sciences, and today it remains committed to the purpose he defined for it. Two hundred years ago animals, plants, minerals, fossils and other natural curiosities were highly prized as valuable scientific resources. All over Europe collections were assembled that could shed light on many aspects of natural history. The Bavarian State Collections of Natural History now harbor over 30 million items. LMU Munich has close links with the institution, as the directors of the individual collections normally hold professorships at the University. Most of my work is actually based on materials in the collection, says LMU researcher Professor Joris Peters, Director of the Department of Palaeoanatomy in the State Collection of Anthropology and Paleoanatomy. We benefit from the fact that biological remains recovered by archaeologists are recognized as culturally valuable, and the state has a legal obligation to conserve and care for them. The sheer number of objects in the State Collections makes it essentially impossible to subject every piece to close scientific study. But with the right instinct, one can often find the proverbial needle even in a haystack of this size. And when the right specimen, perhaps collected centuries ago, meets modern methods of 01

2 Cheetah genetics: Samples taken from 1000-year-old specimens of bones kept in the Bavarian State Collections helped clarify relationships between modern cheetahs. Genetic differences between surviving populations in Iran, South Africa (shown here) and Northeast Africa are larger than had been thought. Source: deo koe/sxc analysis, long-standing questions may find surprising answers. Professor Peters, for instance, is currently examining several palaeoanatomical exhibits, including skeletal elements of extinct species of wild cattle and the Asian wild ass. In collaboration with an international team led by the American anthropology professor Connie J. Mulligan, Peters has helped to reconstruct an intriguing episode in cultural history. The team has identified one of the wild ancestors of the domesticated ass. The region of domestication has long been debated, says Peters. The question is so difficult to resolve because all putative ancestors are either extinct in the wild or in acute danger of extinction. To solve the problem the team combined genetic analyses of samples of skin and dung from the extant Somali wild ass with the anatomical examination of remains of this species and of the Nubian wild ass excavated by archaeologists. The results implied that the donkey was domesticated about 5000 years ago, in Northeastern Africa, possibly in response to an urgent need for beasts of burden to facilitate transport and trade in an arid environment. We can also definitively conclude that the Nubian ass contributed to the genome of the donkey, says Peters. And there must have been at least one other ancestor, very probably another African (sub)species, but certainly not the Somali ass. These findings have practical implications. They could prove useful in the design of captive breeding programs to help restock endangered populations and reintroduce species into areas they formerly inhabited. 02

3 This last consideration also holds for an international project devoted to the cheetah, which was led by the Austrian population geneticist Pamela Burger, and in which Peters was involved. At the end of the 19th century the cheetah was widely distributed in Africa and Asia. Since then, populations of this big cat the fastest land animal in the world have declined precipitously. Moreover, the cheetah is regarded by biologists as a prime example of a species with little genetic diversity. If this were true, all the cheetahs alive today would be closely related to each other and equally vulnerable to disease and deleterious environmental factors. D E S C E N D I N G F R O M A S M A L L R E M N A N T P O P U L AT I O N The evidence seemed to indicate a drastic contraction in numbers some 10,000 years ago, with the result that all present-day cheetahs are descended from a small remnant population. However, the latest genetic studies clearly show that the cheetahs found today in Northern East Africa, Southern Africa and Asia belong to genetically distinct groups, and probably diverged from one another at least 30,000 to 70,000 years ago. This finding is alarming for conservationists, because it effectively rules out the use of animals from one region to rejuvenate a shrinking population elsewhere. The unexpectedly high degree of genetic differentiation between the three populations increases the risk that hybridization would result in the loss of the specific genetic variation that enables the animals to adapt to local conditions. In their study the researchers analyzed both mitochondrial and so-called microsatellite DNA. DNA samples were isolated not only from living animals, but also from skeletal remains of cheetahs from Northwestern Iran that were used as hunting animals in the Middle Ages. These extremely rare specimens are among the holdings in the State Collections in Munich and were made available by Professor Peters. Macroscopic examination and documentation of these finds was carried out at LMU s ArchaeoBioCenter. The cheetah bones, which are over a thousand years old, were then sent to French members of the team for DNA analysis. They turned out to contain well preserved DNA fragments whose sequences closely matched those isolated from modern Asian cheetahs. One of the bones, however, differed genetically from the others, says Peters, suggesting that the genetic variation present in the Iranian cheetah population has diminished since the Middle Ages. The Iranian cheetahs are the last representatives of the Asian subspecies and are genetically distinct from their relatives in Africa. The present population comprises 100 individuals at most and is critically endangered. The new findings emphasize the importance of ensuring their survival. Together with the United Nations Development Program, the Iranian Department of the Environment has started a comprehensive conservation effort (Conservation of the Asiatic Cheetah Project). However, the future of the Asian cheetah is far from being assured. The number of animals in Iran is now stable but at a dangerously low level. 03

4 a b c d e f g h i j k l Wild relatives: Herbarium specimens collected many years ago have allowed Munich researchers to re-order the family trees of cucumbers and melons. Surprisingly, Cucumis picrocarpus (a) from Australia is the melon s closest living relative. Cucumis hystrix (c) from the Himalayas is the cucumber s closest kin. Source: Patrizia Sebastian et al., Proc Natl Acad Sci USA 107: Rare animal species are not the only ones whose family trees are poorly understood. The cucumber also belongs to the list, although it is among the top ten cultivated vegetable species worldwide. Members of the genus Cucumis are also popular among botanists, as indicated by the fact that the cucumber, together with such luminaries as rice and grape, is one of the few flowering plants whose genomes have been sequenced. In the past ten years thousands of papers have been published on aspects of cucumber and melon biology, including some on sex determination mechanisms. In spite of this lively interest, little is known about the evolution of the genus Cucumis, to which the honeydew melon also belongs. The general consensus has been that melons originated in Africa, because African species had been erroneously identified as wild relatives of the cultivated form. To clarify the issue, a research team led by Professor Susanne Renner, Director of the Botanical Garden Munich-Nymphenburg and the Bavarian State Collection of Botany, studied DNA from herbarium specimens of more than 100 Cucumis species originating from Africa, Australia and Asia. 04

5 The analysis revealed that the wild species most closely related to our melon is found in Australia, and diverged from the cultivated form about 3 million years ago, says Patrizia Sebastian, who was the first author of the published study. The common ancestor of these two species diverged from their Asian and Australian relatives about 10 million years ago. At least 25 different species of Cucumis are now recognized in Asia and Australia, and all are descended from a common ancestor that separated from the African branch some 12 million years ago. Nine of these were identified genetically in the new study. Overall, the data argue that the common ancestor of cucumber and melon originated in Asia. Possible ancestral populations have been localized in the Himalayas. Indeed, India and China are home to diverse landraces of Cucumis melo. Our data also conclusively show that the closest relative of our garden cucumber is C. hystrix, which is found in the Eastern Himalayas, says Renner. Further studies and breeding programs should therefore focus on Cucumis populations in Asia and Australia. But the new results serve once again to highlight the value of the centuries-old specimens held in institutions like the State Botanical Collection and Herbarium, and LMU s own herbarium. A large fraction of the plants that we analyzed genetically were collected during the 19th century and in many cases promptly forgotten, says Renner. It would be almost impossible to assemble such a collection today, as many of the habitats no longer exist. The Cucumis debilis specimens for example were collected in what is now a suburb of Hanoi. Translated by Paul Hardy Prof. Dr. Susanne Renner holds the Chair of Systematic Botany and Mycology at LMU Munich and is director of the Botanical Garden, the Bavarian State Collection of Botany and the herbarium of LMU. renner@lrz.uni-muenchen.de Prof. Dr. Joris Peters holds the Chair of Palaeoanatomy and the History of Veterinary Medicine at LMU Munich, is head of the ArchaeBioCenter of LMU Munich and director of the Munich-based Bavarian State Collection for Anthropology and Paleoanatomy, division of Paleoanatomy. Joris.peters@palaeo.vetmed.uni-muenchen.de 05