Conserving biologicalresources

C.W. Clark makes two substantive criticisms in hisrecent TREE review1 of our book, Conservation ofBiological Resources2. First, he objects to twophrases that both appear on p. 28. However, hehas been selective in his reading. He says that it isirresponsible to suggest that limiting harvesting toa constant level of effort can be administeredwithout monitoring population size. We agree that,in isolation, this phrase might send the wrongmessage to resource managers. But elsewhere onthe same page, and on previous pages, we give alengthy discussion of the dangers of using CPUE(catch per unit effort) in resource management,including a stable CPUE could be due toundetected increases in technological efficiency,giving a false picture of stability as the populationdeclines If a population aggregates into largegroups even at low population sizes, or if itslocation is always predictable, then the costs ofharvesting are not related linearly to populationsize The population declines dramatically without

any reduction in harvesting effort Theseconditions are common in fisheries.

The second phrase referred to a means ofcontrolling harvest by allowing a constant proportionof the population to be taken each year. We saidharvesters do not make constant attempts tocircumvent the regulations if they are free to useany technology they please in comparison withwhat happens under rules limiting effort, whenthere is an incentive for the hunters to usetechnological innovation to circumvent theregulations. By quoting phrases out of context, hemisrepresents our argument.

He suggests that another way of approaching theproblem of natural resource harvesting is to treatresources as natural capital. This is indeed a wellknown alternative approach, and one that hediscusses in his pioneering work on resourceeconomics3. However, this method is subject to thesame problems of oversimplification as the simplemodels that we analyse in the first chapter of ourbook; it has now been superseded by approachesthat emphasize the importance of the social andinstitutional frameworks within which people live.

In chapter 1, we outline simple, theoreticalmodels that were, and still are, fundamental to

much of resource management, stressing boththeir strengths and their weaknesses. And then, forthe next 350 pages, we explore how ecological,social and political complexities can be taken intoaccount when managing the interaction betweenpeople and the resources upon which they depend.

E.J. Milner-Gulland

Renewable Resources Assessment Group,Imperial College London, 8 Princes Gardens, London, UK SW7 1NA (e.j.milner-gulland@ic.ac.uk)

Ruth Mace

Dept of Anthropology, University CollegeLondon, Gower Street, London,UK WC1E 6BT (r.mace@ucl.ac.uk)

References1 Clark, C.W. (1999) Trends Ecol. Evol. 14, 1612 Milner-Gulland, E.J. and Mace, R. (1998)

Conservation of Biological Resources, Blackwell3 Clark, C.W. (1976) Mathematical Bioeconomics:

the Optimal Management of Renewable Resources, John Wiley & Sons

Sexual selection and the Y chromosome

In a very interesting article, Roldan andGomendio1 suggest that sexual selection couldhave favored genes on the mammalian Y chromosome, and that these would includegenes on the Y with effects on embryonic growth and tooth size, as well as onspermatogenesis. There are other effects of the Y chromosome on brain and behavior in mice.These include effects of the Y on hippocampalmorphology, whole-brain levels of serotonin, open field activity, copulation, aggression andlearning2. There are sex differences in these brain and behavior traits that might be due tosexual selection3. Also, the Sry gene (sexdetermining region on the Y) is expressed inbrains of adult mice and humans4,5; this genemay have effects on the above-mentioned brainand behavioral traits2.

Stephen C. Maxson

Dept of Psychology and BiobehavioralSciences Graduate Degree Program, The University of Connecticut Storrs, CT 06269-4154, USA (maxtiger@aol.com)

References1 Roldan, E.R.S. and Gomendio, M. (1999) Trends

Ecol. Evol. 14, 59622 Maxson, S.C. (1996) Behav. Genet. 26,

4714763 Maxson, S.C. (1997) Biomed. Rev. 7,

85904 Lahr, G. et al. (1995) Mol. Brain Res. 33,

1791825 Mayer, A. et al. (1998) Neurogenetics 1,

281288

CORRESPONDENCE

The structure of carotenoids

In a recent perspective in TREE, Olson and Owens1presented some important points about thesignificance of carotenoids in sexual signalling.Carotenoids occur in a wide variety of bacteria, fungiand plants and carry out diverse biologicalfunctions. They have also been proposed to play acrucial role in evolution, cold adaptation, sexualsignalling, etc.14 The individual structures of thesemolecules have an important role in theserespective biological functions57.

Carotenoids are isoprenoids containing acharacteristic polyene chain of conjugated doublebonds and are either acyclic or cyclic with one ortwo cyclic end groups. The hydrocarbons arecalled carotenes and the oxygenated derivativesare called xanthophylls. About 600 structurallydistinct carotenoids have been chemicallycharacterized8,9. The structures of the moleculesshown in Box 1 of Olson and Owens article donot contain 19,20 199,209 methyl groups, and thedouble bond in the b-cyclic ring was representedbetween positions 19 and 29. The double bondcannot exist between these positions and shouldbe between positions 59 and 69. (The positionsreferred to here are numbered in a conventionalmanner.) More details on the structures of

carotenoids are necessary, and their structuresshould be represented as in the figure below.

M.V. Jagannadham

Centre for Cellular and MolecularBiology, Tarnaka, Hyderabad-500007,India (jagan@ccmb.ap.nic.in)

References1 Olson,V.A. and Owens, I.P.F. (1998) Trends Ecol.

Evol. 13, 5105142 Johnson, E.A. and Schroeder, W.A. (1995) Adv.

Biochem. Eng. Biotechnol. 53, 1191783 Jagannadham, M.V., Rao, V.J. and Shivaji, S.

(1991) J. Bacteriol. 173, 791179174 Chattopadhyay, M.K. et al. (1997) Biochem.

Biophys. Res. Commun. 239, 85905 Gabrielska, J. and Gruszecki, W.I. (1996)

Biochim. Biophys. Acta 1285, 1671746 Di Mascio, P., Kaiser, S. and Sies, H. (1989)

Arch. Biochem. Biophys. 274, 5325387 Strand, A., Shivaji, S. and Liaaen-Jensen, S.

(1997) Biochem. Syst. Ecol. 25, 5475528 Straub, O. (1987) in Key to Carotenoids (2nd

edn) (Pfander, H., ed.), pp. 9276, Birkhuser9 Kull, D. and Pfander, H. (1995) in Carotenoids

(Vol. 1A) (Britton, G., Liaaen-Jensen, S. andPfander, H., eds), pp. 295317, Birkhuser

Astaxanthin (a common xanthophyll)

OOH

OHO

b -Carotene 13 5

17 16

6

19

9

20

1315

15'13'

20'

9'

19'

5' 3'

1'6'

16' 17'18

18'

(Onl

ine:

Fig

. 1)

236 0169-5347/99/$ see front matter 1999 Elsevier Science. All rights reserved. TREE vol. 14, no. 6 June 1999