fi::st

ONCIIOCERCIASIS OONIROL PROGRAI',IME IN WE T ATRTCA

PROGRAMI'IE DE LL]IIE @NIRE LTONCHOCRGE EX,I AITPJQUE DE L'CuEgf

E@IffICAL GROUP

Eleventl: session

IGr'a, 27 Febnrarlr-2 l,Iarch l-990 wryq]/wrBTo/eo.L4

ORIGII,IAL: FRB{CH

GMGRAPrIIC DTSARTBI}TION OF II{E PRTNCIPAL TRTGIOIITERA SPT,qIES

IN ^WEST AFRICA

by

F.

!I.

Gilcon

i

\,

2-

The attached rnaps represent the data obtajr€d on the distribution

of

^tJ.e principal TYictroptera species present

in

^{We^st} Africa.

This

fi::st

^group

of

^{rnaps ccnprises the}

rcst

ah:rdant species. ^We

will

serd

to

oCP,

in

the cdrr€e

of

^3-990, a secord docr:nent h,trich

will

ccnprise, on t}le one

hand, the genera Ecncnus ard Orthotridria \^rtridr pose delicate ta<oncrdc prrcblems

ard, on ttre ottrer hard, about a hurdrred species $hich are less concerned with the antiblacJcfly spr:ayirg because they a:e

strictly

forest species or onfined to snall

tributaries il

high altihrcle areErs. Itre geogaraphic area shxlied does not coincide o<actly with

tllat of

the ^Prcgramne partly because we have never been

able

to

obtain sh.rfy materials fi:cnr certain areas

like

G|rana ard ^BeniJr ard ^pa:f,Iy

because ORSIOM missions have enabled us

to

strr{r ttre far:na

of certail

rre>ft,erna}

basinsrr lilce ttrat

of

the Cavally or

of

the l(orikrr.r:e. ^SonE

of

ttrese data cannot threrefore be used

directly

but they have rnade

it,

^pmsible

for

us

to

be rnore

specific abcut tlre ecology

of

the species.

A synthesis docunent presentirq tlre analysis

of

these data accorrlirg to certain pa:areters

(for

o<anple, catdrirg date) cannot be made available before

ttp

erd

of

l-990

h:t

^{a series}

of

conclusions atrpear f:sn tlre shlc1r

of

these rnaps

(they are developed belcrar).

First

obsenrations

ltre TYictropter:a faurn

in

^West

Mrica is

^not homogeneor:s ard there are

dif-

ferent far:nistic arieas. The

lirnits

^between these sectors are gradual ard ^can present seasoral variatiorrs.

A

first.

trtrrenorenon appear:s c1early,

i.e.,

basin liJnits are not barrier^s for the TYiclroptera.

ltris

resuLt ^r.,ras orpected because

it

correspords

to drat is

obserrred on otlter continents tx.lt

it

^appear:s inpodant

to

us

to

r:rderscore

it

because

it

^leads aquatic entonologists

to

tackle tlre ^problems

of

^geo$aphic distriJartion

in

a ^vray $rat

differs

frqn that

of

ictrtlryologists.

Cenerally spealcirg, ard

ttris is

particularly apparent

in rpst of

tlrese

doctments, ttre species have a vast distriJartion area

(in

the case

of

many savanna

species,

it

strretches sonetimes up

to

scnrthern

Africa).

WitI tlre ^pr:esent state

of

)<ncruledge, ttrc distri-bution

of ce*ain

species

is

limited

to

one basin ard even only one

site.

This rnay be due

to

the

relatively

^{lovu sarpling} or

to

^the

youthfulness

of

or.tr taxonon-ic )orcr^fledge part,

of

rirhich

is still in

^gestation

(tius,

ottt

of

tlre nine chj:r'arra species napped irt

ttris

^document

six

were de- scribed

after

tlre

start of

the ronitorirg)

.

Hcnrcsrer, there are species wittr ^a Undted distrjlertion

area.

They are fcurd

in

ttre hi$r-altitude a::eas,

i.e.,

nrainly

in

the rnassifs

of

^{Mount Njrnba} ard

of

the Fouta

Djalon.

Ttre far.:nistic ricluress

of

the I,Ian (Cote d'Ivoire)/C;aoua1 (tuixea) axis whichr npre or less covers the highest areas

of ttris

region

will

be noted on the maps. FUthermore, most

of

the species whrich are sti11 beirg studied (wtrose distrjla,rtion rnatrs

will

be provided

to

^the Ecolcgical Group's 1991 nreetirg) are for:rd therre. Ttrese

species are

stricaly

localized because tl.e hiqh-altitrrde areas a::e rrot, wide.

Their watercor:::ses are

in

qeneral snaII, the wate::s are cold ard, ttrerefore, the developxnent rates ard derrsities are

less.

For

all

tlrese reasons, a considerable

3-

prospection

effort will

be necessaqf

for

^tlre obterrtion

of

a good faunistic

description

of

ttrese ernrirorunerrts. I{e only have an atrprcximate }monrl$e becar:se access

difficr.tties

are ofterr

great.

lfioreover, arxl

t]ris is

an iJrportant

poht,

almost

all of

these water:courses are located o.rtside the OCP |tecological _arearr ard

will

t}terefore not be subjected

to lanricidiry.

on the other hard, the fauna slrcns grreat nortq/scnrth variations rrhich corre- spord

to

different vegetational zones \"fiich are also caused by the

rainfall

variations and arueual

distritution. ft

appears q.lite natr-r::al today

tlrat

the forest ard sanranna river^s shroul-d be poprlated by

different

species. EI.rt

if

the idea had been suggested

for

^tJle Tficfroptoa by Gibs ard then by

ttarlier, it

was based only on hypotheses. Ihe situation

of

tlre otlrer rheophilos gtpLps was

hardly better ]mc'hln ard tlre study

of

tlre distrilxrtion

of

these species

of

ttre s.

damnostrn grctp represents the

first

stuty seriorsly docurented

in this field.

suJcsequently, statzner ard Gibon, on tlre llydropqrchidae, Gibon, on

tlp

Philopotanidae, Couturier ard legrard, on the Odonata, have strrdied

tl.is

^prrenone-

'

_r

_non.

The results shcw a good concordance between ttre big vegetational zones ard

t}re rheophilo:s fauna. Ttrere

is,

therefone, a good cojlcidence between the distributions

of

the species

of

the S. danunosun grqlp ard ttrose

of

tlre

Trici-ropt*a species. Thus, there

is

a savanna

lticlrrytera

faurla ttrat

is

rela-

tively

uniform throughout the area colonized

fy

S. aamnosr:rn

s.s.

ard S.

sirbam.un. A rictrer ard

slightly different

fauna

is

fourd

in

ttre a::eal

of

^cnrerlap

between S. sirtcam:rn ard S. damnosrrn

s.s.,

on the one hard, arxt S. sanctifnuli and

S. soubrense on the other hard (typical ocarples

of ttris

sitr:ation are fourd on

the upper Sassard::a, the lor,.rer Bardarna ard ttre Niardan).

First

conclusions

To conclude,

it

appears t},at ttre

poliqf

\^rhich consists

jl

_{rnaXirg an irrvento-}

ry of

^the non-tarrget faurn any tinre a ne$/ geoqraphic area

is

included

in

tne

Progranune

is

less significant

in

entorrclogy tlran

ix

ictrttryology. The strrdy of the Trichropter:a

of

T@o (rrichoptera

of

the southern/eastern o<tension a::ea of ttre onchrocs:ciasis Control kogrannne, trar:asitofogy ard l,Iedical Ertomology docu*

ment

of

Centrre Pasteur du Canreroun given

to

^oCP

for

the l-989

reetirg of

the

Ecological Gr.oup)

is

a good o<anpIe

of ttris.

^We have shoun

that tle

fauna

of

^the

'

greater par{.

of

^{t}re Mono} basj:r

is

^not

different

fron t}rat

of

thre rivers already

--- ncnitored ard located urder sjmil-ar

corditions.

ol1 the otlrer harxl, thre Anrou

basin presents faunistic parbicularities related

to

the fact

tlnt it

flcws

in

an

average-altitude area with a npre nnrked forest ctnrircter.

These data can also be used

for

an in-depth arnlysis

of

tJ-e lorg-term irpact

of

tJ:e tr:eaturcnts on tl.e T?iclroptera.

ft

seems

difficL[t to

unCertake

light

Lrap

monitorilg becar:se

it is

a

hi$rly

techu:icaI work (ard

calls for

^much labor-atory

work). 'Hcn^rever,

all

our

trials

sho,ued that one or tr,vo sanple collections per

site is sufficient for

the obtention

of

a good faunistic

[st;

^{sorre year-s-} Iater, a sinple

visit to

the station

is sufficient for

tlre qraluation

of

a fssiJcle

evolution.

Fina1ly,

this

work, vlhich was ca:ried out on a large scaierconfirms the faunistic richness

of

the untreated

trjlartaries,

as weII as the

ability

of

most

of tie

species

to

colonize rivers with different disctrarrEes,

tfnt is

Lo say

the o<istence irr the ocP area

of

"faunistic ^{refuge zonesrt.} Ttlis'elenrent

will

appear better i:r the arnlysis docr.unent. On a rcre rcduced sc6ls,

it

^rnns well develo@

in

thre work trlorrgitudixal zorntion

of

ttre Bardama /rhver Basin", by Gibon ard Statzner.