any reduction in harvesting effort… These conditions are common in fisheries.’ The second phrase referred to a means of controlling harvest by allowing a constant proportion of the population to be taken each year. We said ‘harvesters do not make constant attempts to circumvent the regulations if they are free to use any technology they please’ in comparison with what happens under rules limiting effort, when ‘there is an incentive for the hunters to use technological innovation to circumvent the regulations’. By quoting phrases out of context, he misrepresents our argument. He suggests that another way of approaching the problem of natural resource harvesting is to treat resources as ‘natural capital’. This is indeed a well known alternative approach, and one that he discusses in his pioneering work on resource economics3. However, this method is subject to the same problems of oversimplification as the simple models that we analyse in the first chapter of our book; it has now been superseded by approaches that emphasize the importance of the social and institutional frameworks within which people live. In chapter 1, we outline simple, theoretical models that were, and still are, fundamental to
Conserving biological resources C.W. Clark makes two substantive criticisms in his recent TREE review1 of our book, Conservation of Biological Resources 2. First, he objects to two phrases that both appear on p. 28. However, he has been selective in his reading. He says that it is irresponsible to suggest that limiting harvesting to a constant level of effort ‘can be administered without monitoring population size’. We agree that, in isolation, this phrase might send the wrong message to resource managers. But elsewhere on the same page, and on previous pages, we give a lengthy discussion of the dangers of using CPUE (catch per unit effort) in resource management, including ‘a stable CPUE could be due to undetected increases in technological efficiency, giving a false picture of stability as the population declines… If a population aggregates into large groups even at low population sizes, or if its location is always predictable, then the costs of harvesting are not related linearly to population size… The population declines dramatically without
carotenoids are necessary, and their structures should be represented as in the figure below.
The structure of carotenoids
Centre for Cellular and Molecular Biology, Tarnaka, Hyderabad-500007, India ([email protected]
) nic.in) References 1 2 3 4 5
distinct carotenoids have been chemically characterized8,9. The structures of the molecules shown in Box 1 of Olson and Owen’s article do not contain 19,20 19 19 ,20 ,20 methyl groups, and the double bond in the -cyclic ring was represented between positions 1 1 and 2 2. The double bond cannot exist between these positions and should be between positions 5 5 and 6 6. (The positions referred to here are numbered in a conventional manner.) More details on the structures of
6 7 8 9
Olson,V.A. and Owens, I.P.F. (1998) Trends Ecol. Evol. 13, 510–514 Johnson, E.A. and Schroeder, W.A. (1995) Adv. Biochem. Eng. Biotechnol. 53, 119–178 Jagannadham, M.V., Rao, V.J. and Shivaji, S. (1991) J. Bacteriol. 173, 7911–7917 Chattopadhyay, M.K. et al. (1997) Biochem. Biophys. Res. Commun. 239, 85–90 Gabrielska, J. and Gruszecki, W.I. (1996) Biochim. Biophys. Acta 1285, 167–174 Di Mascio, P., Kaiser, S. and Sies, H. (1989) Arch. Biochem. Biophys. 274, 532–538 Strand, A., Shivaji, S. and Liaaen-Jensen, S. (1997) Biochem. Syst. Ecol. 25, 547–552 Straub, O. (1987) in Key to Carotenoids (2nd edn) (Pfander, H., ed.), pp. 9–276, Birkhäuser Kull, D. and Pfander, H. (1995) in Carotenoids (Vol. 1A) (Britton, G., Liaaen-Jensen, S. and Pfander, H., eds), pp. 295–317, Birkhäuser
3 5 18
Renewable Resources Assessment Group, Imperial College London, 8 Princes Princes Garden Gardens, s, Londo London, n, UK SW7 1NA ([email protected]
Ruth Mace Dept of Anthropology, University College London, Gower Street, London, UK WC1 WC1E E 6BT (r.mac ([email protected] [email protected]
cl.ac. ac.uk) uk) References 1 2 3
Sexual selection and the Y chromosome
In a very interesting article, Roldan and Gomendio1 suggest that sexual selection could have favored genes on the mammalian Y chromosome, and that these would include genes on the Y with effects on embryonic growth and tooth size, as well as on spermatogenesis. spermatogenesi s. There are other effects of the Y chromosome on brain and behavior in mice. These include effects of the Y on hippocampal morphology, whole-brain levels of serotonin, open field activity, copulation, aggression and learning2. There are sex differences in these brain and behavior traits that might be due to sexual selection3. Also, the Sry gene (sex determining region on the Y) is expressed in brains of adult mice and humans 4,5; this gene may have effects on the above-mentioned brain and behavioral traits2.
Stephen C. Maxson Dept of Psychology and Biobehavioral Sciences Graduate Degree Program, The University of Connecticut Storrs, CT 06269-4154, USA ([email protected]
5' 3' 13'
Astaxanthin (a common xanthophyll)
Clark, C.W. (1999) Trends Ecol. Evol. 14, 161 Milner-Gulland, E.J. and Mace, R. (1998) Conservation of Biological Resources , Blackwell Clark, C.W. (1976) Mathematical Bioeconomics: the Optimal Management of Renewable Resources , John Wiley & Sons
In a recent perspective in TREE , Olson and Owens1 presented some important points about the significance of carotenoids in sexual signalling. Carotenoids occur in a wide variety of bacteria, fungi and plants and carry out diverse biological functions. They have also been proposed to play a crucial role in evolution, cold adaptation, sexual signalling, etc.1–4 The individual structures of these molecules have an important role in these respective biological functions5–7. Carotenoids are isoprenoids containing a characteristic characterist ic polyene chain of conjugated double bonds and are either acyclic or cyclic with one or two cyclic end groups. The hydrocarbons are called carotenes and the oxygenated derivatives derivatives are called xanthophylls. About 600 structurally
much of resource management, stressing both their strengths and their weaknesses. And then, for the next 350 pages, we explore how ecological, social and political complexities can be taken into account when managing the interaction between people and the resources upon which they depend.
0169-5347/99/$ – see front matter © 1999 Elsevier Science. All rights reserved.
) 1 . g i F : e n i l n O (
Roldan, E.R.S. and Gomendio, M. (1999) Trends Ecol. Evol. 14, 59–62 Maxson, S.C. (1996) Behav. Genet. 26, 471–476 Maxson, S.C. (1997) Biomed. Rev. 7, 85–90 Lahr, G. et al. (1995) Mol. Brain Res. 33, 179–182 Mayer, A. et al. (1998) Neurogenetics 1, 281–288 TREE vol. 14, no. 6 June 1999