aridoamerica nabhan

7/21/2019 aridoamerica nabhan

1/14

Native Crop Diversity in Aridoamerica: Conservation of Regional Gene PoolsAuthor(s): Gary Paul NabhanSource: Economic Botany, Vol. 39, No. 4 (Oct. - Dec., 1985), pp. 387-399Published by: Springeron behalf of New York Botanical Garden PressStable URL: http://www.jstor.org/stable/4254790.

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2/14

Native

Crop

Diversity

in

Aridoamerica:

Conservationof

Regional

Gene

Pools'

GARY PAUL NABHAN

2

Scholars have

seldom considered

he native

crop

diversity

n northwest

Mexico

and the U.S. Southwestas resourcesof thesame cohesiveecologicaland cultural

region.

The term Aridoamericas introduced

o

describe his overlooked enter

of

plant

domestication

and

diversification,

which

is distinct

rom

centers

of

Meso-

america and the

Mississippi

Valley.

To

understand

why

certain

of

its

landraces

are

unique,

the

systematicrelationships

and

gene-pool

relations

of crops

ound

prehistorically

nd

protohitorically

n Aridoamerica re

reviewed.

ignifcant

crop/

weed

ntrogression

ontinues

where

ndigenousagriculture

ersists,

butnative

ields

are

being

rapidly

abandonedor converted. n

planning

in

situandex situ

conser-

vation

efforts

o maintain this

diversity,

both cultural

actors

and

plant

population

genetics

must

be considered.

Native

crops

are definedhere

as

domesticated

plants

cultivated

prehistorically

or

protohistorically

within a

regionby

its

indigenous

culturessince

prehistoric

or

protohistoric

imes.

Although

they

need

not

be endemic to the

region

of

concern,

their

landraces should have

been

grown

long

enough

in

the

region

to

exhibit

morphological

or

physiological

adaptations

to the soils and

climatesfound

there.

The landraces

may

in

fact be

key ecological

components

of the distinctive

agroeco-

systems

that

native farmershave

developed,

given

the

climatic

and

edaphic

con-

straints

in their

area

(HernandezX.,

198

1).

Native

crops

are

directly

dependent

upon managementby humans; therefore,they have evolved in part under the

influenceof

farming

practices

of

particular

ultures.

As

such,

native

crop

diversity

directly

reflects

a

region's

cultural

diversity.

It is awkward to view

these

resources

merely

as

a

set

of

genes

that

can

be

conserved

simply

by depositing

them in

a

gene

bank. If

isolated from the

folk

science and

traditional

uses

of

the

culturesthat

have nurtured

them,

they

lose

their

historical

cultural

context.

If

isolated

from cultural

selection

and

natural

selection

exerted in

their endemic

agroecosystems

where

they

have

long

evolved,

their

subsequent

evolution

may change

n

direction.If removed

from

native

fields

whereintrogressionwith wild relativeshas continuedfor centuries,othergenetic

changes

will

occur.

Therefore,

n situ and

ex situ

conservation

of native

crops

are

much more

complex

than conservation

of wild

genetic

resources.

In

the U.S. Southwest

and northwestern

Mexico,

much of

the land

is

arid.

Indigenous agriculture

persists

there,

in

some

places

beyond

where

conventional

modern

agriculture

s successful.In

addition

to

the reason

usuallygiven

for

genetic

conservation

-to

preserve

orfuture

generations

genes

that

may

make

commercial

IReceived7 January1985;accepted17 May 1985. Presentedat the Symposiumon Ethnobotany

of the Greater

Southwestat the

Twenty-fifth

Annual

Meeting

of the

Society

for

Economic

Botany,

Texas

A&M

University,College Station,

TX,

11-13

June

1984;

symposium

organized

and

chaired

by

Dr. Robert A.

Bye,

Jr.

2

Office

of

Arid Lands

Studies,

University

of

Arizona,

845 N. Park

Ave.,

Tucson,

AZ

85721;

and

Native

Seeds/SEARCH,

3950

W. New York

Dr.,

Tucson,

AZ

85745.

Economic

otany, 9(4), 1985,

pp.

387-399

1985,

by

the

New York

Botanical

Garden,

Bronx,

NY

10458

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3/14

ECONOMIC

BOTANY

crop

varieties less vulnerable to stresses

and

maladies-there are others

worth

considering

with

regard

to native

crops

of

this

binational

region:

1.

Native

crops may

be critical to

continued food

production

by

indigenous

cultures. This is particularly true for the most marginal lands, where such crops

have

superior

adaptations

to local

peculiarities

of climate

and soil

(Toledo

et

al.,

1981).

Within

southwestern North

America,

certain

crop

landraces

oftepary

beans

and cushaw

squash

outproduce

commercial

cultivars of

related

species.

These

ecotypes

tolerate low soil moisture in

areas

receiving

less than

70

mm

seasonal

rainfall,

air

temperatures

reaching

49C and

soils with

high

pH,

and/or

soluble

salts content as

high

as

1,800

ppm

(Nabhan,

1983;

Nabhan et

al.,

1985).

2. Certain

crops,

though

not

necessarily

high yielders,

may

be

important

in

efficient utilization

and conservation

of

chronically

scarce

resources

such as

water

and

nitrogen (Romney

et

al., 1978). Water,

in

particular, is in such short supply

that it

is

subject

to

profound

intra- and

intercultural

conflicts

(US

OTA,

1984).

3.

Even

if

introduced and

improved

varieties

yield better,

there

may

be

non-

economic motives

for

honoring

an

"obsolete" native

crop's

right

to exist

(Ehren-

feld,

1977).

For

example,

native

crops

and

special

foods

derived

from them

may

be

symbols

of cultural

identity,

and,

as

such,

may

reinforce

an

indigenous

com-

munity's

pride

and

persistence

(Spicer,

1971).

4.

Native

crops may

cumulatively

provide

a

different

and

perhaps

superior

set

of

nutritional

resources to

indigenous

communities

than

may

be

obtained

through

government

food welfare

programs

or

through

trading posts

(Calloway

et

al., 1974;

Nabhan et

al.,

1985).

Native

Americans

and

"Mexican-Americans"

currently

suffer from

high

incidences of

diabetes

and other

nutrition-related

diseases

(West,

1974).

It

may

be

that fiber-rich

foods

formerly

more

prevalent

in

their

diets-a

diversity

of

beans

(Phaseolus),

mucilaginous

seeds such

as chia

(Salvia),

conivari

(Hyptis)

and cacti

(Opuntia)-served

to flatten

postprandial

blood

sucrose

curves

in

the

same

manner that

artificial

insulin is

used

today,

thereby

reducing

the

side

effects of the

adult-onset

diabetes

syndrome

(Ramos,

1980; Leeds,

1981).

Given

these

reasons for

conserving

native

crop

resources

in

southwestern

North

America,

several

questions

must be

raised.

What

native

crops

were

once

found

in

the

region?

How

are

they

geographically

and

culturally

distributed?

Which

gene

pools

are

diminished

and

in

need of

intervention

before

further

depletion?

What

combination of in

situ and

ex situ

measures will

best

maintain

remaining genetic

variation?

ARIDOAMERICA:

AN

OVERLOOKED

CENTER

OF

DIVERSITY

Table

1

lists the

native

crops

found in

indigenous

communities in

just

4

states

in

the

U.S./Mexico

borderlands:

Arizona,

New

Mexico,

Sonora,

and

Chihuahua.

As can be seen, at least 25 plant species in advanced stages of domestication have

been

cultivated

in

these

states

prehistorically

or

protohistorically.

There is in-

triguing

evidence

that

a

number

of

additional

species

were

cultivated

and/or

genetically

selected

within

the

area

of

these

states

(Table

2),

but

the

degree

of

their

domestication

remains

unclear.

The

point

is

not

that

we

should

inventory

domesticates

state-by-state.

On

the

contrary,

it

can be

demonstrated

that

most

of

these

crops'

distributions

ignore

such

political

boundaries

and

are

shared

by

cultures on

both

sides of

the

current

388

[VOL.

39



4/14

NABHAN: NATIVE

CROP

DIVERSITY

TABLE 1.

DOMESTICATED

PLANT SPECIES

OF ARIDOAMERICA:

PREHISTORIC

AND

HISTORIC

GEOGRAPHY.a

Meso-

Miss.

Crop species AZ

NM CHIH.

SON. amer.

Valley

Amaranthus

cruentus*

0 0

x

x

0

A.

hypochondriacus*

0

x

x

x

0

Canavalia

ensiformis*

0

Capsicum

annuum*

x

x

x

x

0

Chenopodium

berlandieri*

x?

x

x

0 0

Cucurbita

ficifolia

x

x

x

C. mixta*

0

0

x

x

0

C. moschata*

0

0

x

x

0

x

C.

pepo

0

0 0

x

0 0

Gossypium

hirsutum

0

0 0

0 0

x

Helianthus annuus* x x x 0

Hordeum

pusillum*

Indigofera

suffruticosa

x x

x

Lagenaria

siceraria

00

0 0

Nicotiana

rustica 0

x x

x

0 0

N.

tabacum

x

x x

x

0

Panicum

sonorum* 0

x

0

Phaseolus

acutifolius*

0

0

x

0

0

P.

coccineus*

x

x

0

P.

lunatus*

0

0

x

x

0

P.

polyanthus*

x

0

P.

vulgaris*

0 0 x 0 0

Physalis

philadelphica*

x

x

0

Proboscidea

parviflora*

x

Zea mays*

0

0 0

0 0

0

a

Data derived

from numerous

published

and

unpublished

records,

available on

request.

Prehistoric

period,

indicated

by

a

circle,

refers to

archaeological

records

predating

1492.

Protohistoric

period,

indicated

by

an

x,

refers to

archaeological

and contact-time

written

documents, primarily

from

Jesuits

or

early

explorers

in

Aridoamerica,

postdating

1492. An asterisk behind

the

crop

species

binomial

indicates that

conspecific

or

cross-compatible congeneric

wild

plants

are

found within Aridoamerica.

international border. Of course, no such border existed prehistorically. Its recent

presence

has

hardly

affected

the distribution

of

native

crops

or

of

vegetation types

within

which their

wild

relatives

are found

(Fig.

1-3,

based

on

vegetation types

of

Rzedowski,

1978).

This

point

is

belabored

because

most treatments

of

crop

geography

have in fact

stopped

at or

near

this

border

At

best,

they

consider

the

U.S.

Southwest's

farming

traditions

to be a

crop

and

technology

complex

that invaded

this

"marginal

agricultural

area"

as a

package

from Mesoamerica

(Woodbury

and

Zubrow,

1979).

George

Carter's

(1945)

classic Plant

Geography

and Culture

History

in the

Amer-

ican Southwest dealt only with the U.S. Southwest, plus some 250 km2 of the

Colorado

River Delta

in

northwestern

Mexico.

Subsequent updates

or

summaries

of distributions of

native

crop

complexes

by

Winter

(1974)

and Ford

(1981)

have

again

dealt

only

with those tribes that

are distributed

north of

the

International

Boundary.

Dressler

(1953)

and

others,

in a similar

manner,

have dealt

only

with

pre-Columbian

cultivated

plants

of Mexico.

Such limited

views

obscure the

fact that

this

binational

region

is

the hearth

of

endemic domesticates

such as

Panicum sonorum

that

have been cultivated

in

a

1985]

389



5/14

ECONOMICBOTANY

TABLE 2. ADDITIONAL

PLANT SPECIESTHAT MAY

HAVE BEEN

CULTIVATED AND/OR

CULTURALLY

SELECTED IN

ARIDOAMERICA.a

Meso- Miss.

Incipient

domesticate

AZ NM

CHIH. SON. amer.

Valley

Allium

sp.

x

Agave

angustifolia

x x

x

A.

murpheyi

?

x?

Brassica

campestris

x

x

?

Cleome serrulata

0

x

Dactyloctenium

aegypticum

x

x

Distichlis

palmeri

x

x

Hyptis

suaveolens

x x

Jaltomata

procumbens

x

x

Nicotiana attenuata

0

N. trigonophylla 0 x

Solanum

jamesii

x x

I

ee footnote

for

Table

1.

restricted

area on both

sides of the

border but

not

in

Mesoamerica or in the

Mississippi

Valley

(Nabhan

and

de

Wet,

1984).

Whereas

Ford

(1981)

and

Doebley

(1984)

failed to

recognize

a

truly

domesticated

form

of

this

species

with

prehistoric

and historic

presence

north

of

the

border,

others

(Harlan,

1975)

have

erroneously

assigned

this

plant

to a

Mesoamerican

origin.

Other

crops

such as

tepary

beans

(Phaseolus

acutifolius)

and cushaw

squash

(Cucurbita

mixta)

may

have

noncentric

origins

stretching

from

Guatemala

to

Sonora,

but

have been

considered

strictly

Mesoamerican

in

origin (Harlan,

1975).

Most

delimitations of a

Mesoamerican

center of

crop

origins

extend from

Mexico

City

or

Durango

southward

to Honduras

(Vavilov, 1951;

Harlan,

1975). However,

Zhukovsky (1975)

and Zeven

and de

Wet

(1982)

define

a

Mexican

and Central

American

region

with

northern limits

exactly

where

the

present

day

United

States-Mexico

boundary

is situated

(Fig.

1).

It is

remarkable

that

crop

geographers

would

pretend

that

plants

domesticated

prehistorically

were

wise

enough

to

anticipate

where the

Gadsden

Purchase

would

finally place

a

political

boundary

in 1849

Notably,

the

term

Mesoamerica is

commonly

used in

another manner

by

Latin

American

geographers.

It

refers

to a

region

with

climate and

vegetation

that is

predominantly tropical

and

mesic-intermediate

between xeric

and

hydric

in

its

access to

water-that is

located south

of the

extratropical

dry

lands and

adjacent

semiarid

highlands

of

North

America

(Kirchhoff, 1954;

West

1964).

In

an excellent

but

little-cited

publication

that is

available

in

both

Spanish

and

English,

Dr.

Jorge

Leon

(1979)

details

the

distribution of

Mesoamerican

crop

genetic

resources. Leon

notes that

anthropologists place

the

northern

limits

of

Mesoamerica

near the

watershed divide between the Rio Panuco and Rio Santiago at about 22N, and

the

southern

limits at

about

11N in

northeastern

Costa

Rica. His

map, however,

further

limits the

Mesoamerican

center

of

crop

diversity

around

the southern

boundaries

of the

Sonoran and

Chihuahuan

Deserts

(Fig.

2).

This

natural

geographic

boundary

is

roughly

the

southern limit

of what

Latin

American

geographers

sometimes refer

to

as

Aridoamerica,

or as

Norteamerica

Arida

(for

those

not

wishing

to

infer that it

includes

the

only

arid

zones in

the

Americas)

(Kirchhoff,

1954).

Actually,

Kirchhoffs

(1954)

cultural

regions

of Ar-

390

[VOL.

39



6/14

NABHAN:NATIVE CROP

DIVERSITY

Fig.

1.

Delimitation

of

North

American

versus Central

American and

Mexican centers of

crop

origins

as

defined

by

Zeven

and de

Wet

(1982).

Base

map

follows

Rzedowski's 1978

map

of the

vegetation

of

Mexico,

extended into

the southern

U.S.

idoamerica

and

Oasis

Americaare

combined in

my

revised

concept

of

Aridoamer-

ica,

since

I

see

a

gradual

ransition in

genetic

resources

available

within

the

two.

Kirchhoffs

Oasis

America

roughly

coincides

with

what was

recently

discussed as

the

Sonoran

Desert

Agricultural

Region

and

its

native

crop

complex

(Nabhan

and

de

Wet,

1984).

However,

a

broader

binational

region

of

Aridoamerica

may

be

more geographically ohesive as a proposedcenterof diversityfor the following

reasons:

1. It

encompasses

the

major

North

American

deserts

within

which

indigenous

agriculture

hared

many

of

the same

crops.

2. Certain

crops

that

were

previously

assigned

to the

Sonoran

Desert

Agricul-

tural

Region

also

extend

beyond

desert

environments

nto

adjacent

semiarid

and

subtropical

sierras.

Though

not arid

in

the

true

sense,

these

upland

areas

share

the same

pattern

of

evapotranspiration

ar

exceeding

precipitation,

and

their

climates are

controlled

by

the

same air

current

patterns.

3. Certainculturalsubfamilies, orexample,the Sonoranbranchof the southern

Uto-Aztecan

languages,

nclude

tribes

that

historicallyoccupied

lands

in

the

So-

noran

Desert,

Chihuahuan

Desert

fringe,

and Sierra

Madre

Occidental

(Miller,

1983). Apaches,

the

southernmost

Athapaskans,

also had

a

binational

distribution

that

extends

from

Great Basin

to

Sonoranand

Chihuahuan

Desert

areas,

and

they

formerly

ranged

nto

the

Sierra

Madres

as well.

Yuman

tribal

distributions

extend

from

the

Mohave

Desert,

into

the

Sonoran

Desert and

adjacentuplands

of

Baja

California,

again

on

both

sides of

the

international

boundary.

1985]

391



7/14

ECONOMIC

BOTANY

Fig.

2. Northern delimitation

of Mesoamerican center

of

crop diversity

and

of

Mesoamerican

cultures

as defined

by

Leon

(1979).

His

Mesoamerica

extends southward

to northeastern Costa

Rica,

and

in

his written

description,

Mexico's Rios Panuco and

Santiago

are

northern borders.

In

short,

an Aridoamerican

enter

of

crop diversity

is

binational,

ncluding

both

deserts and

adjacent

semiarid

uplands,

as do culturaldistributions

n

this

region.

It extends from

roughly

he

southern

GreatBasin

n

Utah,

around

38N,

southward

at least

as faras the

Tropic

of

Cancer,

and

perhaps

arther outh

in

the Chihuahuan

Desert,

to around

23N.

Its farthest

westward reaches

prehistorically

were the

SaltonBasin andCoachellaValleyin California. t extendedeast to theRio Grande

(Rio Bravo)drainage,

but

farther

south,

I

am not sure

of

its eastern

imits.

I

hope

that

the

provisional

boundaries

of an

Aridoamericancenter of native

crop

di-

versity,

as illustrated

in

Fig.

3,

can be refined

on

the basis of criticism from

archaeologists

and

plant geographers.

Until more archaeobotanicalwork is ac-

complished

n

northern

Mexico,

the

geographic

imits of this

region'scrop

heritage

will

remain

imprecise.

GENE POOLS OF ARIDOAMERICAN

CROPS

The genetic diversity of crops within any regionmay be related to a number

of

factors,

such as:

(1)

the

antiquity

and

continuity

of

agriculture; 2)

ecological

(habitat)diversity; (3)

cultural

diversity;

and

(4)

introgression

of

crops

with their

wild or

weedy

relatives

(Harlan, 1975).

Evidence

for

agriculture

n

Aridoamerica

dates back

to between

2000 and 1500 B.C.

(Woodbury

and

Zubrow,

1979).

After

crops

and

farming

technology

emerged

or were

introduced,

they

were

refinedto

fit a

diversity

of local

environments

(Woosley, 1980).

The

diverse cultures

n

the

region

also

applied

distinct

folk

scientific and aesthetic criteria to

crop

varietal

392

[VOL.

39



8/14

NABHAN:NATIVE CROP DIVERSITY

Fig.

3. Delimitation of Aridoamerica as defined

by

geographical

and

cultural-agricultural

factors.

I

have followed the

vegetational

limits of arid and semiarid

zones to some

extent,

further

limiting

this

center

by excluding

arid areas where there is

no

known

prehistoric

or

protohistoric

evidence of

native

agriculture.

Southern and eastern boundaries

will

require

further

refinement.

selection

for

color, taste,

etc.,

such that

Navajo

blue flour

corn looks

remarkably

different

rom

Hopi

blue flour corn

grown

just

a few

miles

away

from it.

Intraspecificgenetic

variation

within

each

crop

species

in

Aridoamerica can

also be evaluated

from

the

species'

geographic

origins

and

interbreeding

with

species or varieties found within the region. Some crops were introduced after

being

domesticated elsewhere and have had no

gene

exchange

with

wild

species

in

the

region.

These

culturally

allochthonous

crops

include:

Lagenaria

siceraria,

the

bottlegourd;

Gossypium

hirsutumvar.

punctatum,

cotton;

and the

tobaccos,

Nicotiana

rustica,

and

later,

Nicotiana tabacum.

There are additional allochthonous

crops

that have wild

relatives

that

barely

enter

this

region.

Limited

gene exchange

s

theoretically

possible

between the wild

and

domesticated

taxa,

but

it

has not been

documented. Canavalia

ensiformis,

the

jack

bean,

has

a

close wild

relative,

C.

brasiliensis,

n

Sinaloa. The

degree

of

cross-compatibilityanddistributionsof these taxa arepoorlyknown.Pennington's

(1982) ethnohistory

of Eudeve

agriculture

argues

that

the

nearly

extinct

Sonoran

tribe once cultivated a

Chenopodium

species.

If

subsequent

work

confirms the

presence

of C.

berlandieri ar. nuttalliae n this

region,

as

in

the

Mississippi

Valley

and

Mesoamerica

(Wilson,

1981), gene exchange

with

common,

weedy

C.

ber-

landieri varieties

may

have once been

possible

in

Sonora.

The

interrelationships

f Cucurbita

pepo

are

also

not as

simple

as

many

would

think.

Remains of Cucurbita

pepo

in

the

Ocampo

Caves

of

Tamaulipas dating

1985]

393



9/14

ECONOMICBOTANY

from

7000-5000

B.C.

may

represent

he texana

variety,

now known to be

more

widespread

than

formerly

assumed. Whether this

variety

was

native to north-

easternMexico

and

the

adjacent

United States s

currently

unresolved.After

other

C.

pepo

cultivated varieties were

introduced,

it

may

have

exchanged

genes

with

them. Until HughWilson and his colleagueshavereevaluated elationshipsamong

these

taxa,

it

will

remain difficult o

interpret

early

C.

pepo

records

on the

north-

eastern

fringes

of Aridoamerica.

In

published

distributions

of wild

Phaseolus,

no

evidence

is

cited

for

either

P.

vulgaris

or

P.

coccineus

growing

n

arid

northernMexico.

Wild

varieties

of

both

species

have now

been collected on the

fringes

of the

Sierra

Tarahumara

n

Chi-

huahua.

Together

with

my

colleagues

Jose

Muruaga,

Barney

Burns,

and Amadeo

Rea,

I

have

located

populations

of wild

P.

vulgaris

near

Yepachic

and

Balleza,

and wild

P.

coccineusnear

Balleza and

Laguna

de Babicora.

These

newly

located

northernpopulationshave the potentialto hybridizewith cultivatedpopulations

of

domesticates,

and the

2

species

are

cross-compatible.

In

contrast,

Phaseolus lunatus var.

silvester

presently

reaches

Sinaloa,

but

no

farther

north.

Introgression

of

wild

genes

from

this

taxon into

domesticated

imas

or sievas is

hardly

a feasible

explanation

for the

great

varietal

diversity

of lima

bean

landraces found

among

the

Pima,

Hopi,

and Pueblo

Indians

hundreds

of

kilometers to the

north

(Mackie,

1943).

The

Puebloan

cultures

of the

Colorado

Plateau

may

have

harboreda

secondary

center

of

diversity

for

cultivated

Phaseolus

lunatus,

far from

its center of

origin.

Physalisphiladelphica, he tomatillo or miltomate,may be the "tomato"men-

tioned

in

early

accounts of

Eudeve

agriculture

Pennington,

1982).

Its wild

variety

has been

undergoing

selection

and its seeds

are saved

at

Zuni,

far

removed

from

other

wild

populations.

The

cultural

geography

of

Physalis

deserves further

n-

vestigation

in

Aridoamerica.

For another

set

of

allochthonous

crops,

continued

introgression

with wild

rel-

atives is

more

likely,

and this

process

has

probably

contributed

to

landrace

di-

versity

in

the

region.

For

example,

Wilkes

(1970)

documented

Nobogame

teosinte

introgression

nto

maize varieties

in

the

northern

Tepehuan

region

of

Chihuahua.

Thisteosinteintrogressionhaslongbeenconsideredasakeyfactor orthepresence

of

certain

morphological

raits

found

in

prehistoric

maize

elsewhere

n

Aridoam-

erica,

but such

influence is now

subject

to

debate

by

corn

geneticists.

The

bewildering

diversity

of

morphological

forms of

Amaranthus

hypochon-

driacus and

A.

cruentus

from the

Warihio

Indians

may

be due

to

introgression

with

A.

hybridus

Sauer,

n

Nabhan,

1979a).

Near the

Sonora-Chihuahua

order

a

few

Warihio,

Mayo,

and

Mountain

Pima

farmers

still

plant

amaranths.

Ama-

ranthus

hybridus

s

found

in

these

fields

in

high

densities

(Nabhan,

1979a).

More

recently,

I

have

encountered

possible

evidence of

A.

powellii introgression

with

A.

cruentus

grownby

the

Hopi

at Lower

Moenkopi, Arizona. Work in progress

may

confirm

whether

gene

exchange

is

actually

occurring

in

Hopi

fields.

It

is

intriguing

hat

Jonathan

Sauer

(1977)

has

proposed

a

North

American

domesti-

cation of

A.

hypochondriacus

rom A.

powellii,

on the

basis

of

geographic

as

well

as

ethnohistoric data from

Aridoamerica.

LauraMerrick

and

I

have

also

begun

documenting

ntrogression

between

wild

Cucurbita

and

Pima landracesof

squashes

(C.

mixta

and

possibly

C.

moschata)

at

Onavas,

Sonora

(Nabhan,

1984).

This

work will

complement

Merrick's

more

extensive

biosystematic

study

of

the

Cucurbita

sororia

complex

(Merrick

and

394

[VOL.

39



10/14

NABHAN: NATIVE

CROPDIVERSITY

Nabhan, 1984; Merrick,

n

prep.).

It

may

be that this

introgression

s

responsible

for the rich varietal

diversity

of C.

mixta

cushaw

squashes

n

Sonoraand

adjacent

Sinaloaand

Chihuahua,

where

silver-seeded,

Taos-type,

and

marginless

seed

seg-

regatesappear

together

in

populations

that evolved within Indian

fields.

In addition, farmersfrom Onavas, Sonora,insist that wild chiltepinesare con-

tributinggenes

to

their local cultivated

chiles,

some of which

thereby

become

too

hot to

market

Cindy

Bakerand

I

have submitted

samples

of

wild and cultivated

Capsicum

annuum from such

settings

to

Dr.

Steve

Tanksley

and FernandoLoasa

of New Mexico State

University. They

hope

to

use

electrophoresis

as a tool

to

resolve whether

chiltepine

genes

indeed have

introgressed

nto

chiles

(Tanksley,

1983).

Dr. Giles Waines

of

the

University

of Californiaat Riverside is

studying

a

similar

story

of

potential

introgression

of wild and

domesticated

tepary

beans

(Phaseolus

acutifolius),

both

of

which

occur

on

the same

floodplains

in

Sonora,

Chihuahua,and Arizona(Nabhan, 1979b).

The

role of

introgression

n

the

diversification

of

sunflower andracesafter nitial

domestication also deserves

further

field

study.

Hopi

dye

sunflowers

Helianthus

annuus)

have

long

been

grown

in

the same

fields where Helianthus

anomalus,

a

cross-compatiblespecies

(Rogers

et

al.,

1982)

is

protected

by

the

Hopi (Nabhan

and

Reichhardt,

1983).

Wild Helianthus

annuus is not common

in

Hopi fields,

although

t is

abundant

n

those

of

other

tribes,

where t could

potentially"swamp"

the domesticate.

Most

important

in

defining

Aridoamericaas a

distinct center of

diversity

are

its endemic domesticates. Panicum sonorum was domesticatedentirely within

this

region,

but its

relationships

with other taxa

in

the

Panicum

hirticaule

omplex

are

not

clear

(Nabhan

and de

Wet,

1984).

Today,

this

domesticate is

extremely

rare.

In

the area inhabited

by

the

prehistoric

Hohokam,

Hordeum

pusillum

ap-

pears

to have

been

culturally

selected. Karen

Adams,

with the aid

of Vorsila

Bohrer,

Robert

Gasser,

and Charles

Miksicek,

is

in

the

process

of

studying

this

little-known

prehistoric

domesticate.

Also,

the

basketry

fiber

plant,

Proboscidea

parviflora

ar.

hohokamiana

appears

o

have been

domesticated

n

the

last

century

in

the

northernSonoran

Desert,

from

which it was

rapidly

diffused

o

the Mohave

Desert and Great Basin (Nabhanand Rea, in press).PeterBretting(1982) and a

teamof

Arizona

scientists

(Nabhan

et

al.,

198

la)

have

published

on the

dynamics

of this

domestication and

continue

to

study

it.

This

domesticate no

doubt ex-

changesgenes

with

wild

P.

parviflora

var.

parviflora hroughout

much of

its

range

of

cultivation.

Although

I

will

not review them

here,

incipient

domesticates

such

as Jaltomata

in

Mesoamerica

andsouthern

Aridoamerica

Davis

and

Bye, 1982),

and an

Allium

cultivated

by

the

Papago

open

many

new

questions.

At the

same

time,

we

must

reconsiderwhether

or not

early

historic

cultivation of

Agave

(Robertson,

1972)

andof a turniporrutabaga-like ativeroot (Pennington,1982)resulted n distinct

genotypes.

There

is

intriguing

archaeological

videncethat

southern

Arizona

Ho-

hokam

may

have

cultivated an

undetermined

Agave

n

Classic

andLate

Sedentary

times,

in

habitats

where wild

agaves

are

not now

found

(Fish

et

al.,

in

prep.).

DRAINING OF

GENE

POOLS

Of

the

above-mentioned

native

crops,

Hordeum,

Chenopodium,

nd

Canavalia

regional

gene pools

have

dried

up

completely, i.e.,

these

crops

are

extinct in

indigenous

communities of

Aridoamerica.

Locally

adapted Panicum,

Amaran-

1985]

395



11/14

ECONOMIC

BOTANY

thus,

Gossypium,

and several

species

of the cultivated

but

perhaps

not

necessarily

domesticated

plants

(e.g.,

Hyptis)

are near extinction

within

the

region.

Regional

ecotypes

of

chiles, maize,

and sunflowersare

being

rapidlyreplaced

by

introduced,

improved varieties. Other native crops are not threatened,but have certainly

decreased

in

abundance as modem

cash-crop

monoculture has

replaced

indige-

nous mixed

cropping.

Modem

agricultural

management practices

are

likely

de-

creasing

he

potential

for

introgression

of

crops

with

weeds,

since more

intensive

tillage

and

herbicide

use

are

commonplace

in

certain

subregions.

Let

me

emphasize

that the oft-cited

example

of

Green Revolution

hybrids

replacing

ocal

landraces

hardly

accounts for much of

the

genetic

erosion of

in-

digenous

cultivated

plants

in

Aridoamerica.

Most,

but

not

all,

of

this

erosion has

occurredwithin

the last

century,

and is

the

result of several

interacting

actors:

1.

Acculturation/abandonment f

farming raditionsbyindigenouspopulations.

2.

Economic

change/rural

migration

to cities.

3. Destruction of

indigenous

agricultural

"habitats"via

man-inducedenviron-

mental

change.

4.

Usurpation

of traditional

farming

areas or

irrigation

water

by

others.

5.

Replacement

of

small-scalemixed

cropping

by

mechanized

farming

of

single

(often

exotic) crops.

On the

scale

of

villages

and

fields,

there has

been

a

decrease

in

the

genetic

variation found within

certain

crop

species

due

to:

1. Fewer

neighboring

armers

growing

a

particular

crop,

resulting

n

a

smaller

population/gene

pool

overall.

2.

Smaller

populations

of

crops

per

field.

3. Less

frequent

planting

of a

crop

or

landrace.

4. Loss

of the

skills

of

seed

selection and

storage.

5.

Change

in

exposure

to

cross-compatible

weedy

species.

6.

Change

n

vulnerability

to

competition

by

weeds

and

consumption

by

pests

(including

ntroduced

species).

7.

Collapse

of

several

landraces

nto one

multiline

gene

pool.

CONSERVATION OF EXTANT NATIVE-CROP DIVERSITY

A

number of

ex situ

and

in

situ

conservation

strategies

for

conserving

extant

genetic

diversity

have

been

proposed.

One

might pursue

emergency

funding

for

plant

collecting

in

localities

where

rapid

cultural

or

environmental

change

is

occurring,hoping

to

salvage

as

many

varieties as

possible

for

placement

in

seed

banks or

botanical

gardens.

At

the

other

extreme,

perhaps,

is

the

Iltis

(1974)

suggestion

hat we

"freeze he

genetic

andscape."

ltis

argues

hat

scientists

should

urge

politicans

to

negotiate

the

"deliberate

exclusion

of

agricultural

mprove-

ments"

into

"selected

specific

ocal

genetic

landscapes"

where

primitive

landraces

continue to exchange genes with adjoining

weedy

and wild

populations.

He

sug-

gests

that

genetic

erosion

and

environmental

destruction

caused

by

"economic

development"

projects

be

controlled

by

creating

biosphere

reserves

where

indig-

enous

farmers

would be

subsidized

to continue

with their

traditional

agriculture.

Wilkes

(1971) proposed

that

"world

genetic

resource

areas"

be

established

where

native

agriculturalists

would

become

curatorsof

living

collectionsof

crossbreeding

crops

and

weedy

relatives.

To

preserve

areas of

maize-teosinte

introgression,

or

396

[VOL.

39



12/14

NABHAN:

NATIVE CROP

DIVERSITY

example,

Wilkes

suggests

that

only

5

carefully

chosen 5

x

20

km

strips

would

be

needed.

While bothof

these

strategies

are

motivated

by

a trueconcernabout

the

alarming

rate of genetic erosion, they have been criticized for being somewhatinoperable

and ethnocentric.

By relying

solely

on ex situ conservation

measures,

we

make

the

collected

materialvulnerable o

(1)

decreased

population

variation

and

genetic

shifts due to

inbreeding,

2)

the

effectsof seed

storage,

occasional,

recurrent

row-

outs,

and

(3)

human errors

in

sampling

and

handling (Roos,

1980, 1984).

Even

with better

handling

of

germplasm

n

seed

banks,

we

cannot

duplicate

the

"dy-

namic

evolutionary

potential"

of

crops

still found

in

their cradles of

origin(Iltis,

1974).

But

by relyingsolely

on

in situ

conservation

measures,

we would

be

fighting

the

tide of

acculturation,

assimilation,

and economic

change

that affect

virtually

every human population on the planet. Today, it is inevitable that a sizeable

portion

of

any indigenous

community

will

want

to

seek

opportunities

other

than

those

traditionally

open

to

them

in

their

village,

even

if

it

means

foresakingpart

or all of their

agricultural

heritage. "Freezing"

an

agroecosystem

may

not even

be

possible,given

that culturaland environmental

changes

will

continue

regardless

of intentional

efforts

to

stop

or

slow them.

Instead,

it

may

be

possible

to

combine

selected in

situ

and

ex situ

conservation

measures

in a

dynamic way.

Each

crop

or landrace

may

be

suffering

rom a differentrate of

genetic

erosion. The rarer

a

landrace

or

crop

complex

has become

in

a

village,

the

more

important

it

is

to

consider "rescue"

techniques

to

assure

that

some seeds

are conserved

ex situ.

Whena

landrace

s still

grownby

a numberof families

in different

villages,

greater

effortshould

be

exerted

to

encourage

at

least

a few

growers

o

conserve

it in situ.

Various combinations of

in situ

and

ex

situ

crop

conservation are now

being

attempted

by

a number of

organizations,

ncluding

the

nonprofit

Native

Seeds/

SEARCH

organization

basedin Tucson. When Native

Seeds/SEARCH

taff

makes

field

collections,

farmerswho donate seeds are

usually

asked

if

they

have

enough

surplus supply

to

spare

and

if

there are other kinds of

native seeds

that

they

formerlygrew

which

we

might

help

obtain for

them.

In

general,

conservation

measures

will

be

most effectivewhen

communities

of

native farmers

are

cognizant

of,

and involved

in,

their

planning

and

implemen-

tation.

They

should become aware that

reciprocal

exchanges

of seeds with

gene

banks

are

possible

and that other

options

are available as well.

Farmers

who

donate seeds

to

a

gene

bank

or botanical

garden

must

be

informed how

to

gain

access

to

subsamples

of seed increasesheld

in

gene

banks and botanical

gardens,

in

case

they

happen

to

lose their

remaining

seeds.

They

must know

the

reasons

that

others are interested

n

these

seeds,

and their own effortsto

propagate

hem

must

be

reinforced.

In

this

respect,

it

is

heartening

that

agricultural

education

programs

on

Indian reservations

now include

information from tribal

elderson

traditionalplanting echniques,seedsaving,andselection(BinghamandBingham,

1979;

Nabhan et

al.,

1981

b).

In the

future,

indigenous

foods, seeds,

and

farming

practices

should

be

further

encouraged

as

part

of

cultural

revival

movements,

tribal

health,

and

gardening

projects,

and educationaloutreach

programs.

New cultural

and

economic

incen-

tives for

diversified,regionally

adapted

agriculture

must be

considered,particu-

larly

whenextant ncentives

for

growing

certainnative

crops

no

longer

are

effective.

1985]

397



13/14

ECONOMIC

BOTANY

ACKNOWLEDGMENTS

Research

on native

crop/weed

introgression

n Aridoamericahas

been

supported

by grants

from

the Wenner-GrennFoundationand

the

National

Science

Foundation

Anthropology

and

Linguistics

Sections

BNS-8317190), hrough

he

University

of Arizona.

Researchon the causesof

geneticerosion

and

conservation

trategies

pplicable

n

this

region

has

been

aided

by

C.S. Fund

and Tides

Foundation

support

to Native Seeds/SEARCH.

thank

Mahina

Drees,

Karen

Reichhardt,

Barney

Burns,

Laura

Merrick,

Robert

Bye,

Charles

Miksicek,

and Garrison

Wilkes

for

helpful

discussion.

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