The tropical rain forest near its northern limits in Veracruz, Mexico: Recent and ephemeral?

(1)

THE TROPICAL RAIN FOREST

NEAR

ITS

NORTHERN

LIMITS

IN

VERACRUZ,

MEXICO: RECENT

AND

EPHEMERAL?*

Alan Graham**

The Tropical Rain Fon'sl is frpqucntlv characlerized as a stable communit_v remaining virtuallv unl'hanged during much of Cenozoic time (Ashlon, 1969; Brieger, 1969; R ichards. 1964). A nothcr fcature ('Ommonlv acknowledged, occasionall_v bv the same aulhor. is thal almos! nothing is known aboul the geologic historv of the community. Conwr (1958) si a les that "Still lcss is known of the geolog~cal history of the Amazon and Congo fon'sls than the Indo-Malavsian foresl, excepl that the_v musl have extended in modern dn·ss since Eocenc limes'·. Recen! evidence documents considerable climatic and sea lr1·el flui·tuation in equalorial regions during the Quaternarv (Bartlell and Barghoorn, 1973). These environmental changes are reflected in pollen diagrams (van dt'r Harnnwn ami González, 1960) and in relicl distribution pallerns of plan!. (Vuillcuruier. 1971) and animals (Haffer, 1970; Vanzolini, 1973). New evidence is now availahk also demonslraling considerable altPralion .in distribution and generic composi -tion in the late TPrlian-.

An assernblage nf 110 identified fossil spores and pollen has been recovered from the Paraj•· Solo Formal ion. soulh-rnastal Veracruz. The Paraje Solo is of uppermosl Miocene age, hast'd on lwn1hi1· ami planktonic foraminifera in the underlving (Concepcion Supnior) and m·crh·ing (Agucguc~'luitc) formalions. Thc pollen and spore assemblage thus represenls remrranls of a vegetal ion growing in south-coastal Veracruz and along the eastern escarpmenl of thc Sierra Madre Oriental approximately 10-12 million years ago. The arrangemenl of these laxa into paleocommunities is facilitated by the recen! Tipos de Vegetacion de la Republica Mexicana, and a summary of the Veracruz llora by Gomez-Pompa (1973). Comparison between·the modern and upper Miocene communities rcveals sorne sorne similarities and other distinct differences, especially with reference to the Tropical Rain Foresl.

Lignrles are depositcd in warm-lemperale to tropical coastaf brackish environments where rnangrol't'S an' frw¡u<'nllv the dominan! 1·egetalion. Pollen of Rlii::ophora is abundan! in Parajr Solo srdimenls, reaching 96% al one locality. Another mangrove, L11p111rnl11ri11. is also prcscnl along with sPveral genera associated with mangrove rnmmunities (flilúsrns. S11¡ú11i11 . . i\Ii1110.rn. L11d11•1jáa. Utrirnlari11). On upland slopes hordering llw lowlands, al clevalions between 1000-2000 m, scaltered remnanls of arr

• H1·:-:1·ard1 fur rlii . .: :-:tud\ \\a:' :-:upporl1·d 11, .\ISF µr¡11JI:' CH-S671 a11d (;B-1186:2. P;:1pc-r '"'P:-;1·111 1·d al tlw

S1·1·011d Pal1·1d1otall\ and Pal.' 110/0µ_, ( :olloµu_, i;1 :\f (•\in1. S1·p11·111lwr 197-L •• Dqxll'lllll'lll ofBio/oµ:i1·al S1·i1•111·1·~. f\.1·111 S1;1h· l'11i\1·r~ÍI\. f\1·111. Ohio. (1.

<

:

\.

13

Boletín de la Sociedad Botánica de México 36: 13-19, 1977

DOI: 10.17129/botsci.1156

______________

(2)

BOLETIN DE LA SOCIEDAD BOTANICA DE MEXICO No. 36, 1977

oak-Li1¡1iit!a111/mr forest reflect former widesprcad occurrence of the Bosque Caducifoli'o

(Deciduous Forest) in Veracruz. Both the dominants (Q111·r1·11s. lú¡11it!a111/111r) and

numerous associated genera have heen rccovercd from thc Paraje Solo Formation (Psi/11111111 S1•/u¡!i11!'/lu. L.1H1¡uuli11111 .

.4

l.rn¡1ltilu.

Crn//11'11.

Porl11rnr¡ws. Pi1111s.

Cfrn·m.

l/1-r/1'11. Ha111p1•11. H1·rln1s11111.111. E11¡:l'11iallvl.111·ia. G11arl'a. /fr.r . ./11.stici(/. D/1.¡/11/W/I/· lu111. Stru.tl/1111/ltus . ./11.¡d1111s . . 1fr/i11s111(1. P11¡111lus. l/!11111s. lrr·si111•. A/,.lt11n11•a. ¡~·np•/f/llr·

t!i11. T1111m1'fi1rtir1. Clt1111/(ll't!11rl'11).

Bet\\'een. rhe rnastal mangrovcs and upland deciduous forpsfs are Pxlensi\'e areas of suothern Vt>ranuz occupied hv remnants of thc Selrn Alta Pcrcnnifolia (Tropical Rain Forest). According ro Gomez-Pompa (1973). "This is rlw talles! vegctation tvpc in

Veracruz, where it grows in the more humid. ll'arm an•as of the stalP with prccipitation

from 2.500-5.000 mm or more pt>r vear and with frw if a1w dn· months. One of its characteristics is that 80% or more nf the componcnt spPcies are l'H'rgrrcn. or al IPast thl'\' do not follow a dPfinitP pattern of leaf fall al onr •ime. This \'('getation tvpc is one kn~wn as "tropical rain forest", "rain forest", "wcl tropical fon'st'". "p\'l·rgrrrn tropical

forest .. or combination of these namcs. In Veraeruz this tvpe of l'rgrtation is founrf al the

lowland ílatlanrfs al the hase of mountains anrf al thP southrrn end of the statP. In the Sierra de los Tuxtlas it orrupies a great portion of the slope al altitudes helow 700 m.··

011

thc hasis of criteria mentioned h\' Gómez-Pompa (1973). this rommunit\' qualifif's al Tropical Rain Forestas delinee! bv Richards (1964) and is so maprd on thr ren·nt Tipos

de V egetal·ión.

Since this <'Ommunitv occurs marginal to the depositional basin its prt>senc·e should he e\·idenl in the fossil assemhlage. Pollen of 23 gpm•ra found in rain forcst \'Pg•·tation ha\'("

i>e<·n r<'cm·pred. Close scrutinv of thcse gf'1H'ra sho\\'. howr\ '"'· that (a) rnosl arr

\\' ide- rangi ng and cxtenrf in to ot her tvpcs of \'<•gctal ion (

L

1n1¡mdi11111. !'11d11n1r¡111s. Cham111•dorea,

A

frltorne11, Tt'/rorcltidium, CasN1ria, B ursl'fa, fr,,s/111·. Hihisn1s. Cnp(/· nia, Sapium, Cuarea, Hamp('(J, CPdrda, Faram1·a. Paullinia. Spathipln-/111111). and (b)

of tllt' St'\·en rfominants in thc modcrn Vrracruz rain fon·sl (Tr·m1i111tliu. Ca!ophd/11111,

Dialium, BemouLia, Brosimwn, Ficus, and Psr'udolnwdia) only one (Tt'rminalia) has

tentatively been identified in the microflora. The significancc of the latter is difficult to assess since pollinating mechanisms have not be4n studicd critically for anv of the Veracruz species. Pallen of Ficus would not be expected in the microflora because of the small amounts produced and obligatory inseet pollination. However Brosimum alirns· lrum Sw. and Psl'Udolmedia ox.vphyl/aria Donn. Smith are apparently wind pollinated;

BPmoulia .flamm('(/ Oliver can be pollinated by birds but produces large numbers of

flm\ c·rs in <'onspit·uous panielt>s: Cu/11¡1'1.1'1!11111 l1rr1sili1·11sr· Camh. and f)/ufi11111 ¡!11iu111·11s1·

(Aubl.) Sandwith are inseel pollinated but nol <'iosclv assol'iatrd with a single \T<'lor (prornis .. uouslv pollinalt'd). lt is significan!, howt'\'Cr, that f'\'t'n when a SJH'f'i1·s is

primarilv insect or bird pollinatcrf this r!oPs nol ¡m·clurfc 1·ntn· of tlw poll1·n into the sedimentarv record. One frature of Cenozoil' sediml'nls from lropic~ rcgions, in C'Onlrast

lo those of tempPratf' environmrnts, is thc ratlwr comrnon occwTe11t·r of polkn from

(3)

ornamented pollen exceeding 100-125u in size are not unusual in Tertiarv tropical sedimcnts. One explanation mav be the 'out·washing' of pollen under the heavv rainfall of

tropical environments. According to Germeraad et al. (1968, p. 206), "Studies of Recen!

tropical sediments have s1nce shown that, in a humid environment al leas!, waler

transporl ma1· he of far greater quantitative importance than wind transport (Muller,

1959) ·•. Where thc hasin of deposition is in close proximitv, pollen of entomophilous

plan Is rnmmonlv enters thc sedimrnlarv record in tropical em·ironmrnts more frequentlv

!han under seasonal tcmperale conditions. Since many of the dominants and rommon

assoriated genera in the Veranuz rain forest are not exclusivelv insert pollinated, and

sinn· pollen of this 1.1vc does cntcr the fossil record in tropical regions, entomophilv in

itself cannot explain the exceptionallv poor represenlation of rain foresl genera in the

Paraje Solo sediments.

A few non-dominan! genera commonlv associated with the rain forest are represented

in the microflora (.41!0¡1!n-/11s. cf. Astmrnrrnm. cf. Him1•a. Mata1·/w. and possihly

lhrria identified as f;11w·11ial.l,hrria). PoUen of ali hui /llfrráa is present in onlv trace

amoonts (

<

l %). Both in numher of genera (dominants and associates) and amounts of

pollcn the Deciduous Forcsl, presentlv remo1·ed bv 1000 m elevation al minimum from

tlw

clepositional hasin, is hetter represented than the Tropical Rain Foresl which grows

marginal to the hasin. Tlwse data suggest the Tropical Rain Forest was not a prominant

componen! of upper Miocene 1·cgetation in Veracruz and there is other corroborating

e1·idt•nt't'.

Pollen grains of Vi1·1·a have becn found in 5 samples distributed among 3 sities of the·

Paraje Solo Formation. The gcnus does not occur in southern Mexico al present, and is

found onlv al high el1•1ations (2300-3200 m) in Coahuila, Durango and Nuevo León ~P.

1111·.1 i1w111 Martínez,

P.

1.fii/11uil111r11111 Martínez; Gordon, 1968). The presence of spruce 1000 km south of its prrsent rangc. through 8'.> of latitude, clearlv argues for cooler

dirnates in soutllt'astcrn Mcxico during Mio-Pliorcne times. The curren! studies of

Conzúlcz-Quintcro on Miocent' derosits in Mexico are of interest and preliminarv resulrs

show thc presencc of Pin•a and rhe virtual absence of the rain forest also in Chiapas.

Scn·ral genera charactcristic of temperate eommunities (viz., the oak-Liquirlamlwr

fon·st) are o<Tasionalh· found srnllered in the Tropical Rain Forest of Veracruz

(Podornr¡)(/s . . lhrin1). These have bcen interpreted as relicts of former cool periods aºnd

Sarukhan (Prrs. Comm., 1974) suggests a lower annual mean temperature of 3.4'.>C

woulcl accounl for the ecological anomalies of the lowland forests of Yeracruz.

An arrav of nt•w indepcndrnt evidence argues for cooler temperatures in suutheastern

Mexico during the late Cenozoic: (a) poor representation of the Tropical Raín Forest in

upper Miocene sediments deposite<l in lowland environments, (b) presence of spruce

pollen irl Miocene deposits of Veracruz and Chiapas, (e) substantial representation of the

pr~st•nt mid·altitude deciduous forest in the Paraje Solo lignites, suggesting a l91wering of

(4)

hasin, and (d) presen1·e of upland tempera!!' elenwnts as relicts in the modern lowland lropil'al forest. Sarukhan (Pers. Comm .. 1974) notes that disaggregation of the Tropical

Rain Forest through lower tcmperatures would favor expansion of th<' lowland warm-oak l'Ollllllunitv (l'.g., Q111·n-11s o/l'Oi<frs Cham.

&

Sl'hl.¡. This suggt•stion is l'Onsistent with

high f'l'l"l'l'ntages of oak pollrn (30-343) al Site 6, l'onsiderahlv greatrr than could he 1·ontrihut<'d IJ1· Q111·n-11s frorn tlw high altitude pine-oak or mid·altitudl' oak-li1¡11id11111/111r

fon·sts.

Th!'Sl' data d!'monstral•' that although l'icnwnls of ·the Tropil·al Rain Forrsl wen·

prt'Sl'lll in V!'ranuz in tlw up¡H'r Mio1·l'll<' (Allo¡iln-/11s. l'f. .'lstmmrrn111 . . lfatai-fw. l'f. lliri11·11. and possihlv lhrl"/11 and Tl'r111i1111/i11) thev wl'rc not rnalrsc!'d into thP well-dl·fin.('d rxtensivt· asso!'iation of n•1·1·11t tinw. lf thr rain forPsl was ahsent or poorlv

d!'\l'loped in Veracruz during the Mio-Pliocene. it is interPsting to ('()nsidl'r the agr of this

formal ion so frequentlv charal'lrrized as stahle and of greal antiquit_, .. Tlw 1011 rr

tern¡wralures apparent in Veranuz during the Mi(}-Pliocene wer<' Parh· stages in a

dimalil' drtl·rioration rventualh· l'ulrninating in the Pleistocene glal'iations. If thesr lower trrnperatures were. al least in par!. rPsponsihle for poor definition of tlw rain forrst. it is

diflicult lo en,·ision am· sustained period hetwPen thc Mio-Plio1·Pn<' and end of tfl(' gl<ll'iations when tlw lropil'al ef Pnll'nls could rnalf'scc into a relatin·h· pcrrnanl'nl association of mod1·rn aSpP!'I (Flint. 1971. p. 422). This raises tlw intriguing possihilit,· that tlw modern Tropical Rain Forl'SI in Vcranuz mav

ill'

of post-glal'ial origin of IPss

than 11.000 ,.l'ars.

5,.,.l'ral models ar<' arnilahlc lo l'xplain s¡wcies di, l'rsit_,. in tropil'al l'm·ironments.

Somc (Ashton, 1969) assumr an ancient ~tahl1· \'l'gt'lal ion wh1•1T n1·w gi·notvpes 111av

pcrsist, whill· othl'rs (VuillPumicr. 1971: Haff1•r. 1970: Yanzolini. 1973: Vanzolini anrl Williams, 1970) rrl¡uirr a dvnamil' "ommunit_,. 1·xperil'111·ing rn·11 hahitals and srlPl'li11· prcssures. Evidrncc from modern allfl Qua teman· hiotas of tlw Amazon Basi n sugg<'sls

the Tropical Rain Forcsl has rpn•nth- und!'rgo1H' rnnsidPrahl1· alteration in rangc and composition. The l'vidPnl'l' from VPranuz dcmonstrates this drnamic as¡wl"I has

l'haral'l<'riz1•d the rain forrst. near its northcrn limits. sinc1· al ll·asl si1H·1· Mio-Plion·np '

times.

SLJMMARY

Paln1ological studies of up¡wr Miocenr deposits, Veracrnz. revea! tlw Tropil'al Rain forest absent or poorlv den·lo¡wd. Pn·setH'l' of sprncP poll1·n i11di!'alcs lower

l<'mperatun·s mav have prP\'entl'd rnall'S('t'lll't' of tropical elements into th1• modern rain forcst until post-glacial times. Tlw data is consisten! with recen! spel'iation models based on fluctuating eyuatorial rnvironments and dvnamic rain forest vrgetation.

(5)

GRAHAM, THE TROPI

CA

L

RAIN FOREST NEAR ITS

NORTHERN

LIMITS

RESUMEN

l·:s111clios ¡1alinoli'1gi""s clt• clqH'1sil<1s cl<'I Mi<11·t•no su¡ll'rior dt• Vt•ra1Tt1z. rt'ITlan una a11st'1lt'ia" 1·s1·as<1 d1·sarroll<1 clt· la s1·h·a alta flt'f't'Il!lifolia. La prt'St'n<'ia dt' polt•n d1· Pil'l'fl

incli1·a liajas l1·111¡1t•ral11ra:' 1¡11•· tft.liit•ron halwr im¡wcliclo la t'o;til'sl't'Il<'ia clt· 1·lt'nH'nlos

ll'llJli1·;tl1·s !'ara ,·onllg11rar a una s1·ha húnwda 1nodnna. lo <'Ual <11·11rri1'i. hasla los l'"ríodos JlOsl·gl;wian·s. La inli1r1n;wi1'1n pn·s1·111;11fa 1·s l'l>nsisl1·n11· 1·on los nwclt•los nTi1·nlt•s d1•

1'SJll'<'i;wiún J1;isaclos 1·n llu .. 111al'illl11·s ;il!llii1·111alt•s 1••·ualorialt•> _1 1·n la clinállli<'a di• la s1·ha

.tila Jll'l'l'll ni folia.

BI

R

l

.

J

()(;

R

:

\

PH

)

.

\SllTO\.

I'

.

S. 1969. Sp1'l'ialion a111ong lmpi1-;tl li1n·s1 ln·1·s: son1t· cl .. d11<'li<1ns in ilw

ligh1 ..

r

n·1·1·111 1·1 id1·11t·1" /11: R. 11. l.0111·-\l..<:on111·1l (Ecl.). S¡!l'lú11i1111 in Tm¡iil'lll

F11riru111111·nts. ·\1·acl1·n1i1· Pr1·s,-. Lond<1n. pp. [.).'i-196.

H

\HTIY'IT. ·\. ancl I·:.

S. B

.\

HLllOOK\. 19/:l.

Ph

i

1og1·<1graphi1· hi:-lon ol' 1111' l:-ihnrn$

.. r

l'ana1na during llw pasl 1

:2.000

.

' 1

·ars ( . .\ Jii,-1on of' 1 •·g1·lalion . ..!i111a11·. ancl

,

.;1·a-l1·1 ,.¡ ..!1ang1·). /11: .\. Crahan1 (Ed.). / ·1·p·t11ti1111 1111rl ¡ ·l'f.!'l'l11li111111! llisl11r\'

11/

.. Vorthl'm f,utin Aml'ri('(t. Elsevier Publ. Co.,-Amsterdam, pp. 203-299.

HHll-:LEH. F. C. 1969. P;tlll'I'IlS ol' 1·111l111ionan and gl'llgraphi1·;tl dislrihulion 111

\1·<1ln1pi1·;tl tlrt'hids. /11: R. H. Lm11•-\li-Co111wll (t:d.) . . ~jll'1·i111i1111 i11 Tro¡iil'lll Fnl'imn1111·111s. Al'a1k111i1· Pr1·ss. Lond<111.

l'I'·

197-211.

UlH\l·:H.

!

·:

.

.l.

11 .

19.)8. Tlw 1·1oluli<111ol'11·opi1-;d li1rt·s1. /11:

.l

. fll!'d1•1.

1·1 al .. (Edrs.). l·.'rn/11ti111111s 11 l'ml'l'Ss. :\111·11;111cl1'11\\i11. l.<111d<111. p¡1. .')..J .. 1-6.

f.'1.1\T. H. 1-'. 1911. (,'/11l'i11! 1111rl (i111111·m111T (,'1'11/11g1. Jul111 Wil1·1. N. Y. 892 p¡1.

CERMERAAD,

J.

H.,

C.

A. HOPPING, and

J.

MULLER. 1968. Palynology ofTertiarv S1•di1111'nls l'ro111 Tro¡1i .. ;tl :\ n•a,;. lfi-1'. !'11/111'11/){)/. l'11h1111!11µ:i ():

l

89-:l48.

C()\JEi'.-PO\IP•\. A. l 97:l. Ernl<1g1 ol' liw 1<'g<'lali<111 <11' V1•ranuz. In: A. Lraham (Ed.).

¡ ·"µ·1·/11/i11n 1u11! ¡ ·,·µ1·/11ti11n11! llistun

11/

\11rll/l'm f.11ti11 ·l 1111·ril'11. Els1·1 i1•r Pulil.

<:11

..

\111s11·rtla111. p¡1. 1:3. J-~8.

(;o

H 1 )() '\. :\.

e.

l 96B. l·: .... 1 .. g_1 ..

r

l'i1·1·11 1-!1 ih n11 lill1/// I/ M arl Ílll'Z. Frn/11µT 19: 880-896. 11 \ FFl·:R ..

1 .

1970. < ;,.11J11gi1"1·li111a1 i1· hisl<1n a nd wog1•11graphi1· ,;ig11ili1·a11t·1· ol' 1 lw

l

I rara

rt·gi<111 in 1t<1rll1111·s11·rn C<1lo111lii;1. (.'11/rl11si11 /11:

60:3-6

:

-36.

\ll 'U.l·:H . .

l

.

19::i9. Pah 11ol11g1 111' H1•1·1'11I Ori1u11·11 d1'lla and slwlf' St'dimcnls.

\li1'l'll/ll!l1·1111!11/11µ·1 .): J .:Q.

HIUl:\Hl>S.

P.\\

'.

196-k

T

i,,.

Tm¡1i1·11! l<11i11 F11n·s1. Ca111hridg1• llni1. Pn·ss. London. ~.)()

,.,

..

\. \.\ l>EH

11 .-\

:V

J:VIF

·::.J

.

T.

ancl

E.

CONL\LEZ. 1960. llpp<'r Pl1·isllw•·n<' and HoltH't'IH' 1·li111alt' and V1-gi·lali1111 of' 1lw .. Saliana d1• Bogola" (C<1lo111liia. Soulh Anwri .. a). ¡,,.¡,¡". (,'rn/. \/1'1/i-r/d .l.>:261.:l

J

:'i.

(6)

v

..

\\IZOLINI.

P.

E.

1973.

P,dt

'

Ot'limalt'

S. relit'f

,

and

S

Jlt't'it'

S

muiliplit

'

alion in

t't¡Ualorial

li>rt

's

l

s

.

fo:

B.

Mq~g<'rs.

t'I

al.. (Edr

s

).

Tm¡Jirnl f'11rl's/ f:rn.n-s11·111s i11 .4frirn and S11111h l11fl'rÍl'l1: .·/ C11111¡11//'ali1·1· l<l'l'Í1•1r.