THE ROLE OF ECOLOGY IN BIOLOGICAL CONSERVATION'

The Role of Ecology in Biological Conservation

Author(s): Peter F. Brussard

Source: Ecological Applications, Vol. 1, No. 1 (Feb., 1991), pp. 6-12

Published by: Ecological Society of America

Stable URL:

http://www.jstor.org/stable/1941843

Accessed: 15/02/2010 11:49

Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at

http://www.jstor.org/page/info/about/policies/terms.jsp

. JSTOR's Terms and Conditions of Use provides, in part, that unless

you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you

may use content in the JSTOR archive only for your personal, non-commercial use.

Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at

http://www.jstor.org/action/showPublisher?publisherCode=esa

.

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed

page of such transmission.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of

content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms

of scholarship. For more information about JSTOR, please contact support@jstor.org.

Ecological Society of America

is collaborating with JSTOR to digitize, preserve and extend access to

Ecological Applications.

? 1991 by the Ecological Society of America

THE ROLE OF ECOLOGY IN BIOLOGICAL CONSERVATION'

PETER F. BRUSSARD

Department of Biology, University of Nevada-Reno, Reno, Nevada 89557 USA

Abstract. The emerging science of conservation biology represents an intersection of elements of ecology, genetics, biogeography, and many traditional applied disciplines such as wildlife management and forestry. Its major concern is providing a valid scientific basis for actions that will slow or stop the accelerating loss of biological diversity worldwide. Ecology's major contributions to conservation biology so far include the equilibrium theory of island biogeography and the theoretical relationship between population size and per- sistence time. In the future ecologists can contribute their skills to conservation biology in numerous ways; I suggest three in particular. These are investigating the autecology and natural history of rare species, testing hypotheses concerning population viability with carefully designed laboratory and field experiments, and working to establish and imple- ment a national policy for the protection of biological diversity on United States public lands.

Key words: biological diversity; conservation biology; extinctions; population persistence times; rare species; Uncompahgrefritillary; Yellowstone National Park.

INTRODUCTION

If current

predictions

are true, and there is little doubt

that most are, the last decade of the twentieth century

and the first few decades of the twenty-first

will be years

of ever-worsening ecological crises. The driving force

behind the crises is the human population, now num-

bering more than five billion and growing at a rate of

:2%/yr. As this population expands, its demand for

food, fuel, and other resources increases proportion-

ally. In the less-developed world human resource de-

mand tends to affect the environment directly, resulting

in easily observed phenomena such as widespread de-

sertification and deforestation. The effects of human

resource demand in more-developed countries are less

direct but just as destructive to the environment; ex-

amples include acid precipitation, the ozone hole, and

global warming.

One of the upcoming ecological crises is a major

extinction event. Within the next century thousands-

some say millions-of species will disappear forever.

Prime candidates for extinction include all the large

carnivores, many large herbivores, most primates, and

countless other plants and animals that have the mis-

fortune to be rare or highly specialized, or to have

restricted habitat requirements and limited distribu-

tions. The prospect of human-caused

extinctions ofthis

magnitude should horrify any thinking person for mor-

al and aesthetic reasons alone, but if it does not, there

are excellent practical reasons for alarm. Not only are

many of these species direct sources of hundreds of

useful products such as drugs, building materials,

chemicals, and food, but they are also the underpin-

nings of the natural ecosystems that currently provide

free environmental

services-waste detoxification,

pest

control, climate amelioration, and flood prevention to

name but a few-that will be extremely costly, if not

impossible, to replace.

The root causes of the pending extinction crisis are

economic, social, and political, and until human in-

stitutions and values change it is unlikely that major

losses of biological diversity can be prevented. How-

ever, the timely application of information from the

biological sciences can help ameliorate the problem.

Conservation biology is a synthetic discipline that fo-

cuses on the application of biological principles to the

preservation of biodiversity; it represents a fusion of

relevant ideas from ecology, genetics, biogeography,

behavior, reproductive biology, and a number of ap-

plied disciplines such as wildlife management and for-

estry. In fact, virtually all of the subdisciplines of bi-

ology have something worthwhile to contribute to the

conservation challenge, and conservation biology ac-

tively seeks to incorporate relevant information from

all of them.

Conservation biology emerged as a nomothetic dis-

cipline nearly a decade ago with the publication of

Soule and Wilcox's (1980) book Conservation

biology:

an evolutionary-ecological

perspective. When I made

this claim a few years ago (Brussard 1985) I did not

mean to imply that there were no biologists working

in the field of conservation or that conservationists

ignored biology prior to 1980. Rather, the Soule and

Wilcox volume breached traditional disciplinary

boundaries, brought together a great deal of diverse

February 1991 ECOLOGY AND BIOLOGICAL CONSERVATION 7

information, and attempted to apply this information

directly to the preservation of global biodiversity.

Subsequently,

I believe that the book has had at least

three major impacts. First, it stimulated many basic

biologists to apply their expertise to conservation prob-

lems; second, it provided a broader perspective to sci-

entists already working in the field. Third, it defined a

new interdisciplinary

area that is now somewhat of a

growth industry. For example, over a dozen books have

appeared with conservation biology in the title, and

several more are in preparation

or in press. The Society

for Conservation Biology, barely four years old, now

has >2000 members, and Volume IV of its journal

Conservation

Biology is currently being published. The

Ecological Society of America now recognizes conser-

vation biology as a legitimate enterprise and is pro-

viding a publication outlet through Ecological Appli-

cations.

Although conservation biology is not just applied

ecology, ecology has played a central role in its devel-

opment, and it will continue to do so in the future.

Major intellectual contributions from ecology include

the theory of equilibrium biogeography (MacArthur

and Wilson 1968) and the relationship between pop-

ulation size and persistence

time (e.g., May 1973). These

topics have recently been reviewed in detail by Sim-

berloff (1988) and Pimm and Gilpin (1989), and their

papers are strongly recommended to those who wish

to pursue these topics in depth.

Rather than cover much of this same ground here,

I address three areas in which ecologists can apply their

expertise to current problems in conservation biology.

These are (1) investigating the autecology and natural

history of rare species, (2) testing hypotheses concern-

ing population persistence through laboratory

and field

experimentation, and (3) working to establish and im-

plement a national policy for maintaining biodiversity

on United States public lands. While this is far from

an exhaustive list of what needs to be done to minimize

extinctions in the next half-century, these three areas

will provide dozens of challenging problems for con-

servation-oriented

ecological research.

THE AUTECOLOGY AND NATURAL HIsToRY OF RARE SPECIES

It is usually taken as a sine qua non that sensible

management begins with a solid, fundamental under-

standing of a species' ecological relations and natural

history. Unfortunately, we are woefully short on this

information for most species of conservation concern.

While this may come as no surprise for rare and little-

known species, it is also true for many of the more

charismatic birds and mammals. For example, tens of

millions of dollars are spent annually on grizzly bear

research, but there are no reliable data on male mating

success in this species. Such information is of critical

importance for calculating genetically effective popu-

lation size, a key element in population viability es-

timates. In the absence of such data, managers are

forced either to extrapolate from other species or to

ignore the parameter

altogether.

Neither choice is likely

to result in sound management plans.

As another example, I describe a project recently

completed by my research group. The Uncompahgre

fritillary Boloria acrocnema is probably the rarest but-

terfly in North America. It has been proposed for listing

as endangered,

and the agencies involved (United States

Fish and Wildlife Service, United States Forest Service,

United States Bureau of Land Management, Colorado

Natural Areas Survey) were anxious to have infor-

mation on its status and recommendations

for its man-

agement and recovery. Funds were provided for a

2-yr survey of its distribution and abundance.

Although this species was described almost a decade

ago (Gall and Sperling 1980), it has not been the object

of intensive study by ecologically minded lepidopter-

ists. The following information was available in the

literature and agency reports: The two known colonies

are both located above 4000 m in elevation on north-

east-facing slopes in the San Juan Mountains of Col-

orado. Evolutionarily, it represents the southern ter-

minus of an increasingly differentiated series of

populations of an arctic butterfly,

Boloria improba

(Gall

and Sperling 1980, Ferris 1984, 1986). Its larval food

plant is snow willow, Salix nivalis, and the larvae take

two years to develop (Scott 1986). Flights were ob-

served, and the butterflies were abundant at both col-

onies for a few years after their initial discovery. Cap-

ture-mark-recapture

studies were performed on one

colony in 1979-1980 (Gall 1984a, b), but no other

quantitative data were obtained on the species' abun-

dance after that time.

In 1987, the first year of our study, we found it to

be extirpated at one of the two known localities and

very rare at the other; in 1988 it was present at both,

although at greatly reduced numbers from those pre-

viously reported. Although we surveyed the surround-

ing area extensively, no other colonies of any size were

found even though there had been anecdotal reports

of their existence in previous years.

as a metapopulation with a dynamic equilibrium be-

tween the rate of colonization of new patches and the

extinction of old ones; and (4) that the species' biennial

life history has led to both odd- and even-year broods,

which function essentially as separate populations with

independent demographic trends.

Since there had been several extremely hot and dry

summers in southwestern

Colorado during the past few

years, and since both colonies apparently declined si-

multaneously during this period, we proposed that cli-

matic stress was responsible for the observed declines

in the known colonies and the apparent extirpation of

the others that were rumored to exist. During our sur-

vey we identified >50 sites at the appropriate

elevation

and exposure that supported thriving populations of

snow willow and had suitable adult nectar sources. We

quantified 29 variables related to these habitat param-

eters and searched for both univariate and multivariate

correlations that might separate the two occupied sites

from the rest. None was found, consistent with our

assumption of ample habitat availability. However,

there will always be the nagging doubt that we had

overlooked the importance of some critical habitat

component, and that unoccupied sites were vacant for

reasons other than a long run of bad weather.

We interpreted the lack of a flight at one known site

in 1987 as the extirpation

of the odd-year brood there-

in other words, the loss of one quarter of the species'

entire population. However, there is a possiility that

acrocnema may actually have only one brood, with

individual larvae showing a large variance in devel-

opmental rates, some maturing in 2 yr, others in ?3

yr, depending on ecological conditions. Such a life his-

tory pattern is known in other butterflies, and if true

for the Uncompahgre fritillary, it would make the ab-

sence of the 1987 flight at one colony much less om-

inous for the species' continued existence.

Clearly, adequate ecological data on this species

would have provided us with a much more firm foun-

dation on which to base interpretation of the results

of our survey and to prescribe appropriate manage-

ment strategies.

It is important to note that such studies

need not have been mindless exercises in data gath-

ering; rather, the four assumptions listed above could

have been used as testable hypotheses to drive several

research projects. During the early 1980s the species

was abundant enough to produce respectable sample

sizes, and the two colonies are located within 160 km

of the Rocky Mountain Biological Laboratory, a field

station well known for its research on lepidopteran

populations. However, for whatever reasons-reluc-

tance to work on rare species, lack of interest or funding

opportunities, logistical problems, etc. -the excellent

early work on B. acrocnema was not followed by de-

tailed ecological studies. As a result we had to make

our recommendations on the basis of seemingly rea-

sonable, but largely untested, assumptions. If these as-

sumptions are valid, the return of more normal weather

I %J. v I I 1l W. v

conditions should eventually result in the recovery to

early 1980's levels of both broods at one colony and

of the even-year brood at the other. After this level of

recovery has occurred, artifical translocation to other

apparently suitable, but currently unoccupied, sites

could provide a greater margin of safety for the species

in the future. If our assumptions are not valid, how-

ever, B.

may be the first full species of

butterfly to go extinct in North America.

EMPIRICAL

VERIFICATION

OF POPULATION

CONCEPTS

One of the major tenets of conservation biology is

that stochastic, rather than deterministic, processes

govern the dynamics of small populations. Four types

of stochasticity are recognized, two of which have been

modeled fairly extensively (see Soule [ 1987] for a recent

review and appropriate

references).

According to these

models, demographic stochasticity-the random vari-

ation in individual birth and death rates-has little effect

on the persistence of any but the smallest populations

(i.e., those with <20 breeding individuals). On the oth-

er hand, environmental stochasticity-environmen-

tally driven variability in birth and death rates that

affect the population as a whole-has a much more

important effect on persistence probabilities,

and much

larger numbers are required for a population to be

immune from its effects. Catastrophe,

the third type of

random occurrence that can affect persistence times,

may be considered as the endpoint of a continuum of

environmental stochasticity. If the catastrophe is suf-

ficiently severe and widespread, no population size will

be large enough to guarantee the avoidance of extinc-

tion-witness the events at the Cretaceous/Tertiary

boundary.

The fourth type of stochasticity involves random

genetic processes that occur in small populations: spe-

cifically, increased inbreeding and loss of variability

by drift. The influence of genetic stochasticity on pop-

ulation persistence has proved to be particularly re-

fractory to prediction for several reasons. First, its ef-

fects depend not on the census size of a population but

on its genetically effective size, a number notoriously

difficult to estimate. Second, past population history

enters into the picture, and this is hardly ever known.

Third, genetic events often interact with demographic

ones in complex ways, and it is very difficult to sort

out cause from effect.

February 1991 ECOLOGY AND BIOLOGICAL CONSERVATION 9

populations are liable to local extinction in relatively

short times, and that the variance in population growth

rates is a robust predictor of persistence times. Fur-

thermore, Goodman suggests protocols for testing his

model by accumulating data on the spectrum of ac-

cessible sizes in a number of carefully chosen popu-

lations.

I take Goodman's recommendations

one step further

and point out that the requirements

for an appropriate

test organism would be a species that is rather seden-

tary and inhabits well-defined patches of habitat. In-

dividuals must be easy to census so that sampling error

is a minor component of population size estimation.

The species must have a relatively high intrinsic rate

of increase (r), and its reproductive success must be

dependent to some extent on easily monitored envi-

ronmental variation (e.g., the extent and timing of rain-

fall, temperature

at critical times, etc.). Generation

times

must be short enough so that useful data, including the

observation of several extinctions, can be obtained

within reasonable time periods. If the populations are

located within normal dispersal distances for the spe-

cies it will also be possible to use the experimental

system to test several aspects of metapopulation the-

ory and to relate metapopulation dynamics to the

structure of the environment and to the size and iso-

lation of habitat patches (e.g., Hanski 1989). Habitat

patches arrayed along an environmental gradient of

known effect on the species would be ideal for this. If

tissue samples can be obtained nondestructively, or if

individuals can be sampled after reproduction

with no

effect on subsequent demographic

trends, then gel elec-

trophoresis can furnish information on changes occur-

ring in genetic parameters within the populations as

well. Many insects or other invertebrates,

many plants,

and some small vertebrates have natural history char-

acteristics that would make them amenable to such

studies. Several examples have appeared in the recent

literature. Forney and Gilpin (1989) used laboratory

populations of Drosophila to test the relationship be-

tween population size and persistence times, and to

test the efficacy of corridors in preventing extinctions.

A semi-natural field experiment on population persis-

tence using marine snails is described by Quinn et al.

(1989), and McCauley's

(1989) paper on milkweed bee-

tles should convince the skeptical that natural extinc-

tions ofpopulations ofthis species are common enough

to merit detailed study.

It must be noted that studies like these increase in

value considerably if they are carried out for long pe-

riods of time. Although some meaningful investiga-

tions of population persistence may be reasonable

graduate student projects, the most significant payoffs

will come from long-term commitments. Perhaps the

ideal situation would be that every ecologist, upon tak-

ing a permanent position somewhere, choose an ap-

propriate system and work on it faithfully-even at a

low level-for at least 15 yr.

PROTECTION AND MANAGEMENT OF BIOLoGIcAL DIvERsITY

Ecologists study populations of vertebrates, inver-

tebrates, plants, and microbes, and they seek to un-

derstand the patterns and linkages among these pop-

ulations when they assemble into communities. Thus

biological diversity truly is the ecologists' bread and

butter. Yet anyone who has done field work for more

than a decade knows that biodiversity is disappearing,

not only in the tropics, but in North America as well.

Favorite field sites have vanished under condomini-

ums or parking lots; species once common are now

rare or extirpated;

unusual community types no longer

exist locally.

To be blunt, preserving biodiversity is clearly in ev-

ery ecologist's own self-interest, and he or she should

pledge to spend a measurable portion of time working

to accomplish this goal. The first step is a commitment

to the political action necessary to enact an appropriate

national policy on biodiversity. Such a policy requires

three major elements. First, it must explicitly recognize

that biodiversity includes all species of plants, animals,

and microbial life, the genetic variation within them,

and the full variety of communities that result from

their aggregations.

Second, it must contain provisions

for the inventory and continued monitoring of these

elements. Third, it must mandate that the diversity of

species, genetic variation, and community types now

found in public lands will be maintained over an ac-

ceptable period of time with an acceptable degree of

risk. Environmental groups often need ecological ex-

pertise to articulate

these requirements

adequately,

and

legislators need biologically sophisticated advice when

drafting appropriate legislation. Ecologists can con-

tribute much in either arena. HR 1268, the Scheuer

biodiversity bill currently pending in Congress (see

Blockstein [1989] for details), is not perfect, but it has

many good features. Every ecologist should lobby for

its passage.

I specify public lands in particular

because these are

the major reservoirs of biological diversity in the Unit-

ed States. At present, however, the Forest Service and

the Bureau of Land Management largely manage lands

under their control for the production of certain com-

modities (e.g., timber, cattle, or minerals) without too

much regard for the effects these activities might have

on other components ofthe system, although managing

for "wildlife" (i.e., species subject to sport harvest) or

"wildlife habitat" may be one of several multiple-use

management goals. Lands managed by the Fish and

Wildlife Service and the National Park Service are gen-

erally oriented toward the protection of charismatic,

recreationally

important, or officially listed endangered

or threatened

species, while other elements ofbiodiver-

sity are usually ignored.

Vol. 1, No. 1

activities and left to its own devices, will be self-per-

petuating. This is probably true (at least on a time scale

of decades) if the area is large enough to support a

natural disturbance regime of sufficient magnitude to

ensure continued succession and viable populations of

the species with the largest space requirements. How-

ever, these conditions are rarely met on any of our

public lands. Either preserve areas are not large enough

to support viable populations of the largest species, or

natural disturbances are not allowed to proceed with-

out major human intervention, or both.

Yellowstone National Park is an excellent case in

point. About 20 yr ago Yellowstone chose to follow a

policy of "natural regulation." The philosophy behind

this decision was that if left alone, or at least managed

minimally, Yellowstone would eventually revert to

something resembling its pre-settlement state. Among

other things, natural regulation meant that the elk pop-

ulation would no longer be controlled by park person-

nel; rather, their numbers would be governed by their

food supply. Bears would no longer be fed at garbage

dumps; instead, they would forage completely on their

own. Fires, if ignited by lightning, would be allowed

to burn as long as they did not threaten life or property.

The success of these policies has been mixed at best.

After control of elk stopped, the animals soon reached

very high numbers. Although the effects of this pop-

ulation explosion are still a matter of debate, many

biologists feel that they caused a significant reduction

of aspen communities and riparian vegetation, with

attendant negative impacts on other animal species.

The effects of the natural regulation policy on the griz-

zly seem to be more clear-cut. After the garbage

subsidy

stopped, the bears expanded their foraging areas and

increasingly came into serious conflicts with human

activities both on and off park land-resulting in a

substantial

population decline. The natural burn policy

had little effect in reducing the extent and intensity of

the major fires of 1988, which, at least in retrospect,

could have been predicted from the ecology and fire

history of the region. During years with normal pre-

cipitation few natural ignitions occur, and the fires that

do start do not usually burn very well. However, during

severe drought years such as 1988, fires characteristi-

cally sweep through the Yellowstone area, clearing out

thousands of acres of aged, insect-damaged lodgepole

forests and setting the stage for massive renewal and

regeneration (Christensen et al. 1989).

The major reason that natural regulation does not

work very well in Yellowstone is because of a scaling

incompatibility; the park is too small to contain self-

regulating

populations of large mammals or to support

a natural disturbance regime of the size characteristic

of the northern Rocky Mountain region. When events

such as the 1988 fires or a severe winterkill of ungulates

occur, they are perceived as disasters because they are

concentrated in a relatively small, highly visible, area.

And if Yellowstone, the largest national park in the

lower 48 states, with an area of 900 000 ha, is too small

for natural regulation to succeed, such a management

philosophy is surely doomed to fail in the smaller na-

tional parks as well.

If our major nature reserves are too small to main-

tain biodiversity over the long term, what can be done?

One possibility might be to increase the preserve area.

Managing the entire 5 200 000 ha of public land in the

"Greater

Yellowstone Ecosystem" as a wilderness pre-

serve has received a great deal of discussion (e.g., Clark

and Harvey 1989). This land area probably is large

enough to support viable populations of all native spe-

cies along with the local disturbance regime on an ap-

propriate scale. Unfortunately, much of this land is

enormously valuable for other uses, and political and

economic realities indicate that commodity production

and multiple-use philosophies will prevail over pres-

ervationist goals for a long time to come.

The second, and more realistic, possibility, is to

manage public lands actively to protect their biodiver-

sity. Management

actions to accomplish this goal would

range from largely laissez-faire to highly manipulative

depending upon the circumstances and the degree of

risk involved, and the policy would apply to both mul-

tiple-use (e.g., Forest Service, Bureau of Land Man-

agement) and Park Service lands. The major advantage

of this approach on multiple-use lands is that under

an active biodiversity management policy relatively

little additional acreage would have to be "locked up"

in preserves, and traditional activities (e.g., mining,

logging, grazing, recreation) would not usually have to

be curtailed. Rather, the effects that these activities

might have on biodiversity would need to be evaluated

in the same manner as their effects on watersheds or

"wildlife" are evaluated now. Any negative impacts

these activities might have on biodiversity would have

to be mitigated; only if no mitigation were possible

would the activities not be allowed.

February 1991 ECOLOGY AND BIOLOGICAL CONSERVATION 11

national parks as backcountry zoos, it is far preferable

to just wishfully thinking that natural regulation will

result in their retaining a full complement of species

and communities a century from now.

In order for active management to work successfully

on either multiple-use or wilderness lands, well-for-

mulated strategic and tactical plans must be designed

and implemented. Unfortunately, the current philos-

ophies of the land management agencies and the skills

of most of their personnel are not up to this task. For

example, the idea that biodiversity includes more than

just "wildlife" sensu stricto is virtually foreign to agen-

cy thinking. Likewise, comprehensive approaches to

management do not characterize the strategies cur-

rently employed by land-management

agencies; rather,

compartmentalization

and specialization have become

their primary foci. Finally, the solid, underlying science

necessary for developing appropriate

conceptual mod-

els for biodiversity management is generally lacking;

even worse, what is known is rarely applied.

For these reasons the active participation of ecolo-

gists in the development and implementation of bio-

diversity management is extremely important. Appro-

priate management actions will often require a wide

variety of interventions at the population to whole-

ecosystem levels of organization. This means that un-

anticipated and unwanted side effects will most likely

accompany many of these actions unless a substantial

amount of modeling and experimentation

has preceded

them. The models will have to be based on current

theory in ecology, biogeography, genetics, and evolu-

tion, and the experiments must be well thought out,

rigorous, adequately replicated if possible, and genu-

inely relevant to the contemplated actions. Even then,

unwelcome surprises will doubtless occur, and the

management must be flexible enough to accommodate

changes and reversals when they are called for.

This interplay among modeling, experimentation,

and management action will require not only increased

communication between resource managers and ecol-

ogists in general but also active involvement of non-

agency scientists in the entire process-from planning

through implementation to evaluation. Such an in-

volvement is a two-way street. First, it will require

overcoming the prevailing apathy of most ecologists

toward conservation issues. Second, it will require that

agency biologists and managers seek out non-agency

scientists and encourage them to utilize their expertise

in solving these critically important problems.

ACKNOWLEDGMENTS

Work on the Uncompahgre fritillary was supported by the U.S. Forest Service, the Bureau of Land Management, and the U.S. Fish and Wildlife Service. David Kuntz of the Col- orado Natural Areas Program was instrumental in securing this funding and in encouraging me to become involved with the project. I have discussed my ideas on biodiversity man- agement with many colleagues both in academia and in the land-management agencies. While hardly any of them agree

with my views, I appreciate their input. Finally, I thank Simon Levin for inviting me to participate in this symposium and to reviewers for useful comments.

LITERATURE CITED

Agee, J. K., and D. R. Johnson, editors. 1988. Ecosystem management for parks and wilderness areas. University of Washington Press, Seattle, Washington, USA.

Blockstein, D. E. 1989. Biodiversity bill update. BioScience 37:677.

Brussard, P. F. 1985. The current status of conservation biology. Bulletin of the Ecological Society of America 66: 9-11.

Christensen, N. L., J. K. Agee, P. F. Brussard, J. Hughes, D. H. Knight, G. W. Minshall, J. M. Peek, S. J. Pyne, F. J. Swanson, J. Ward Thomas, S. Wells, S. E. Williams, and H. A. Wright. 1989. Interpreting the Yellowstone fires of 1988. BioScience 39:678-685.

Clark, T. W., and A. H. Harvey. 1989. Management of the Greater Yellowstone Ecosystem: an annotated bibliogra- phy. Northern Rockies Conservation Cooperative, Box 2705, Jackson, Wyoming, USA.

Ferris, C. D. 1984. Overview of Clossiana improba (Butler) in North America with a description of a new subspecies from Wyoming (Nymphalidae: Argynninae). Bulletin of the Allyn Museum number 89.

. 1986. Field notes of Clossiana improba harryi Ferris (Lepidoptera: Nymphalidae). Journal of Research on the Lepidoptera 25:71-72.

Forney, K. A., and M. E. Gilpin. 1989. Spatial structure and population extinction: a study with Drosophila flies. Conservation Biology 3:45-51.

Gall, L. F. 1984a. Population structure and recommenda- tions for conservation of the narrowly endemic alpine but- terfly Boloria acrocnema (Lepidoptera: Nymphalidae). Bi- ological Conservation 28:111-138.

. 1984b. The effects of capturing and marking on subsequent activity in Boloria acrocnema (Lepidoptera: Nymphalidae) with a comparison of different numerical models that estimate population size. Biological Conser- vation 28:139-154.

Gall, L. F., and F. A. H. Sperling. 1980. A new high-altitude species of Boloria from southwestern Colorado (Nymphal- idae) with a discussion of phenetics and hierarchical deci- sions. Journal of the Lepidopterists' Society 34:230-252. Goodman, D. 1987a. Thedemographyofchanceextinction.

Pages 11-34 in M. E. Soule, editor. Viable populations for conservation. Cambridge University Press, Cambridge, En- gland.

. 1987b. How do any species persist? Lessons for conservation biology. Conservation Biology 1:59-62.

. 1987c. Consideration of stochastic demography in the design and management of biological reserves. Natural Resource Modeling 1:205-234.

Hanski, I. 1989. Metapopulation dynamics: does it help to have more of the same? Trends in Ecology and Evolution 4:113-114.

MacArthur, R. H., and E. 0. Wilson. 1968. The theory of island biogeography. Princeton University Press, Prince- ton, New Jersey, USA.

May, R. M. 1973. Stability and complexity in model eco- systems. Princeton University Press, Princeton, New Jer- sey, USA.

McCauley, D. E. 1989. Extinction, colonization, and pop- ulation structure: a study of a milkweed beetle. American Naturalist 134:365-376.

Newmark, W. D. 1987. A land-bridge perspective on mam- malian extinctions in western North American parks. Na- ture 325:430-432.

Vol. 1, No. 1 R. M. May, and S. A. Levin, editors. Perspectives in eco-

logical theory. Princeton University Press, Princeton, New Jersey, USA.

Quinn, J. F., C. L. Wolin, and M. Judge. 1989. An exper- imental analysis of patch size, habitat subdivision, and ex- tinction in a marine intertidal snail. Conservation Biology 3:242-251.

Scott, J. A. 1986. The butterflies of North America. Stanford University Press, Stanford, Califomia, USA.

Simberloff, D. 1988. The contribution of population and community biology to conservation science. Annual Re- view of Ecology and Systematics 19:473-51 1.