TRENDS in Genetics Vol.18 No.5 May 2002

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272 Forum

A foot in each world

Captivating Life: A Naturalist in the

Age of Genetics

by John C. Avise Smithsonian Institution Press, 2002. $24.95 hbk (222 pages) ISBN 1 56098 957 2

Throughout the history of biology, there has

been an uneasy coexistence between two

very different traditions – a field-orientated

one with its emphasis on natural history, and

a laboratory-based one with its emphasis on

experimentation. Tensions between these

two traditions intensified after the discovery

of the structure of DNA spurred the rise of

molecular genetics. In his autobiography

[1], Edward O. Wilson documented

these ‘molecular wars’as they affected

Harvard’s biology department during the

1950s. Although molecular wars continue

to rage, or at least smolder, in most biology

departments, a new synthesis has emerged

in recent decades. With increasing frequency,

molecular genetic techniques are being

used to address ecological and evolutionary

questions, leading to the creation of new

fields such as molecular ecology and

phylogeography. John Avise, who has been

at the forefront of the creation of these

fields, discusses their maturation and his

own in his autobiography, Captivating Life.

Avise’s first passion was natural history.

Growing up in Michigan, he developed a

particular fondness for birds and fossils.

During summers as a teenager, Avise

assisted Harry Pederson filming undersea

life in the Bahamas. Here, Avise learned

the ‘concept of observational natural

history in its own right, in which novel

secrets of science might be learned with

suitable diligence’. Avise’s maturation as a

natural historian was also substantially

influenced by his reaction to the Vietnam

War. He shares an illuminating excerpt

from the 1970 letter he wrote as part of his

application for Conscientious Objector

status wherein he explains his philosophy

about environmentalism and the war .

Avise was impressed by the power of

genetic tools as a graduate student. Under

the tutelage of Robert Selander, then at

the University of Texas, Austin, Avise

used the then-new technique of allozyme

electrophoresis to examine the genetic

variability of cave- and surface-dwelling

populations of fish in the genus Astyanax. In

less than a year, he collected sufficient data

for a Master’s thesis that was quickly turned

into a classic paper [2]. Among other things,

Avise found that surface populations have

markedly greater genetic diversity than do

cave populations. For his doctorate, Avise

joined Francisco Ayala’s lab at the University

of California, Davis, and examined patterns

of genetic diversity among species of

minnows and sunfish. Although there are

many more species of minnow than of

sunfish, species within each group showed

comparable levels of divergence. This

pattern was interesting in that it was

consistent with phyletic gradualism, the

claim that morphological change generally

occurs gradually and within lineages. The

pattern was seemingly inconsistent with the

competing claim of punctuated equilibrium,

which states that morphological change

occurs in fits and starts and generally

coincides with the splitting of species.

Although working with very diverse

taxa, Avise’s research program has been

unifying. Not only did he bridge the gap

between the lab and the field, Avise

also helped to bridge the gap between

population genetics and phylogenetics by

focusing on phylogenies below the species

level. Avise was one of the driving forces in

investigating how geographical features

influence phylogenetic clustering. He also

attempted to forge a consilience between

the seemingly antithetical biological

species concept (which emphasized

reproductive isolating barriers) and the

phylogenetic species concept (which

emphasized diagnosably distinct character

states) [3]. Perhaps the diversity of taxa

and questions he has worked on helped

Avise to see the conceptual unifications.

Captivating Life provides a rare

glimpse into the thoughts of an active

researcher in mid-career. Avise not only

discusses issues related to science, but

also those of lab management and

graduate student training. For instance,

Avise strongly disagrees with the

conclusion by the National Research

Council (NRC) that the US grants too

many PhD degrees ‘relative to its needs’

in the biomedical sciences. Instead, he

believes that the current and looming

environmental crises and the

technological breakthroughs in genetic

engineering require the training of many

more biologists in both genetics and

environmental biology. Although my

personal opinion is closer to that of the

NRC, Avise’s defense of his position is well

considered and worth reading.

Science, as Avise concisely and accurately

describes, is ‘…a principled manner by which

phenomena are explored. The epistemological

hallmarks of science are objectivity, critical

open-mindedness and the ruthless evaluation

of alternative hypotheses against evidence’.

Avise’s autobiography also shows that the

science of life, from natural history to

molecular genetics, can be captivating.

Norman A. Johnson

Dept of Entomology, University ofMassachusetts, 102 Fernald Hall, Amherst,MA 01003, USA.e-mail: njohnson@ent.umass.edu

References

1 Wilson, E.O. (1994) Naturalist, Island Press

2 Avise, J.C. and Selander, R.K. (1972)

Evolutionary genetics of cave-dwelling fishes of

the genus Astyanax. Evolution 26, 1–19

3 Avise, J.C. and Wollenberg, K. (1997)

Phylogenetics and the origin of species. Proc.

Natl. Acad. Sci. U. S. A. 94, 7748–7755

A history of genetics?

Gene Action: A Historical Account

by Werner Maas Oxford University Press, 2001. £22.50 hbk (176 pages) ISBN 0 19 514131 8

I had always assumed that Werner Mass

was a biochemist by training who had

exploited genetics in his studies of

biosynthesis and its regulation in bacteria.

From this book, however, I learnt that he

was initially a geneticist and viewed his

work as biochemical genetics; he was not,

as I had thought, only a user of mutants.

Gene Action is a historical account of

genetics, and it begins with Mendel rather

than with Miescher. Based on lectures Maas

has given on the history of molecular

genetics, it is an amalgam of material taken

from books and his own recollections. Many

of the founders of modern genetics have

written accounts of the past 50 years and, of

course, we have Horace Judson’s book, The

Eighth Day of Creation [1]. It is difficult to

cover such a long story, from the beginnings

of genetics to the human genome sequence

in 150 pages, and, inevitably, there are

sections where the accounts are sketchy

and, on occasion, inaccurate.

Book Review

TRENDS in Genetics Vol.18 No.5 May 2002

http://tig.trends.com

273Forum

Only the old are interested in history,

the young, as I have written elsewhere,

think only of the past two years – although,

perhaps, this now needs to be amended to

the past two weeks. One has to have gone

far down the road to be able to discover

how the roots of one’s life and work are

connected with others in time and place.

For those interested only in the new

buds, history must seem a tedious

preoccupation, and unless it is well done

and challenges the reader with perhaps a

new view or a different integration of the

past, it can become very boring. I am much

more interested in the personal slant on

past events; Stendahl’s letters describing

Napoleon’s retreat from Moscow give one

a strong feeling of participation that no

military history could accomplish. The

memoir, cast on a small scale, is much

more fascinating than the broader picture

of the past events. The book livens up

considerably when it becomes the memoir

and Maas tells us of his personal

experiences; of working with Bernie Davis

and his encounters with the great.

The best part of the book is the picture

on the front cover, showing the younger

Jacques Monod with that intense and

half-amused look those who knew him will

always remember. Even the young, who

know nothing about β-galactosidase

induction will be gripped by it.

Sydney Brenner

The Molecular Sciences Institute, Inc., 2168 Shattuck Avenue, 2nd Floor, Berkeley,CA 94704, USA.e-mail: sbrenner@molsci.com

Reference

1 Judson, H.F. (1996) The Eighth Day of Creation:

Makers of the Revolution in Biology, Cold Spring

Harbor Laboratory Press

Changing times for

heterochrony

Beyond Heterochrony

edited by Miriam Leah ZelditchWiley Liss, 2001. £74.50 hbk (392 pages)ISBN 0 471 37973 5

Despite the recent growth of ‘Evo-Devo’,

there is still a large conceptual gulf

between evolutionary and developmental

biologists. The main area of common

ground is the discovery, of a remarkable

degree of homologous mechanism in the

development of apparently disparate

creatures. Indeed, developmental

biologists are often tempted to think

that there are not really any significant

differences between Caenorhabditis

elegans, Drosophila and the mouse! Those

developmental biologists who take a

particular interest in evolutionary change

tend to try to identify individual items of

the genetic program that have been altered

to bring about particular morphological

alterations in closely related organisms.

The approach of evolutionary biologists

has been totally different. Mesmerized by

Stephen J. Gould’s book Ontogeny and

Phylogeny [1], they seem to be convinced

that just one process, called heterochrony,

underlies most morphological change. There

are various definitions of heterochrony, but

in general it means an alteration in timing

of some aspect of development. The classic

examples of heterochrony are well known;

for instance, the phenomenon of neoteny

(more strictly ‘paedomorphosis’) whereby, in

certain salamanders (including the axolotl),

sexual maturity occurs in what is usually

considered the larval stage.

Beyond Heterochrony is a thoughtful

collection that addresses the current

status of the concept and its utility in

evolutionary studies. An important theme

is the application of sophisticated new

morphometric methods, to determine

whether heterochrony has actually happened

in particular evolutionary changes. For

example, a chapter by Nehm on two extinct

species of margenellid gastropods shows

that their relationship can be interpreted

as heterochronic. By contrast, several

chapters, for example those by Webster

et al. on trilobites and by Zelditch et al. on

modern pirhanas, shows that relationships

can be more complex, and some, such as

Shapiro and Carl’s chapter on skink limbs,

seem to rule out heterochrony as a factor.

Another theme in the book is the

resurrection of the concept of ‘heterotopia’

as an alternative to heterochrony.

‘Heterotopia’means a change in the

position of a structure, and relates more

directly to modern developmental biology

than does heterochrony, because of

the high level of understanding of the

molecular basis of spatial patterning

that now exists. Several of the chapters in

this book conclude that there has been a

degree of heterotopia in their objects of

study; for example, Frolich’s chapter on

the origin of flowers and Roopnarine’s

chapter on species of the bivalve Chione.

It seems to me that there are two general

problems with the obsession of evolutionary

biologists with heterochrony. First,

elaboration of the concept has tended

to broaden its meaning until it conveys

nothing but a vague idea that a change

is rooted in some aspect of development.

The way this can occur is illustrated by

considering the definition of Raff, to whom

heterochrony is, ‘a dissociation in timing

between individual developmental

processes or modules’. This definition

appears at first sight to have a useful

precision, but it widens the potential scope

of heterochrony to encompass all examples

of something occurring or not occurring

because its normal cause has shifted in

time, maybe shifted so much that it never

happens. Developmental biology is replete

with examples of repressive interactions

that prevent the formation of structures

where they are not required, so it follows

that the loss of an interaction can easily lead

to the formation of heterotopic structures.

But this means that the distinction between

heterochrony and heterotopia has been lost.

Second, there is the unfortunate fact

that timing is one of the aspects of

development that is least well understood

by developmental biologists. We simply

have no idea how events can be

programmed to occur at times that are

long relative to biochemical events or

to the cell cycle. The other big hole in

contemporary developmental biology is

any real understanding of the control

of size and proportions. Because size,

proportions and timing are the basic raw

material of most morphometric analysis,

it follows that the persistence of a large

gulf between developmental and

evolutionary biology is not surprising.

The book is written for evolutionary

biologists who are familiar with modern

morphometric analysis. It is quite detailed

and would be most useful for a graduate

student or research level readership. At

£74.50 it is unlikely to have significant

sales to individuals, but it would be a

useful acquisition for libraries serving

evolutionary biologists who have an

interest in morphological change.

Jonathan Slack

Developmental Biology Programme, Dept of Biology and Biochemistry,University of Bath, Bath, UK BA2 7AY.

Reference

1 Gould, S.J. (1977) Ontogeny and Phylogeny,

Harvard University Press