Species-Environment Patterns of Forest Vegetation on the Uplifted

Species-Environment Patterns of Forest Vegetation on the Uplifted Reef Limestone of Atiu, Mangaia, Ma'uke and Miti'aro, Cook Islands Author(s): Janet Franklin and Mark Merlin Source: Journal of Vegetation Science, Vol. 3, No. 1 (Feb., 1992), pp. 3-14 Published by: Blackwell Publishing Stable URL: http://www.jstor.org/stable/3235991 Accessed: 08/11/2010 22:22

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Species-environment patterns of forest vegetation on the uplifted reef limestone of Atiu, Mangaia, Ma'uke and Miti'aro, Cook Islands

Franklin, Janetl* & Merlin, Mark2

'Department of Geography, San Diego State University, San Diego, CA 92182, USA; 2Department of General Science, University of Hawaii, Honululu, HI 96822, USA; *Tel. 619 594 5491; Fax 619 594 4938; E-mail [email protected]

Abstract. We examined woody species composition and its areas, the site of agricultural activities; however, native relationto environmentalvariables in native forestgrowing on vegetation is largely intact on the rugged makatea (Sykes four limestone islands in the southern Cook Islands: Atiu, 1976a-d) because the karst topography is unsuitable for Mangaia,Ma'uke, and Miti'aro.Relative dominance(percent most forms of cultivation. basal area)of woody species in 74 sites was sampledusing the There have been few botanical studies in the south- point-centeredquarter method, and the data were analyzed ern Cook Islands (Sykes 1980a), and most have been using clustering and ordination techniques. These tropical based on collections from a island forestshave a relativelylow diversityof native woody species Rarotonga, high (32 native and 10 introducedspecies occurredin our sites). (Cheeseman 1903; Wilder 1931; Philipson 1971; Fosberg Fourforest types were recognized:Pandanus/Guettarda litto- & Sachet 1972; Stoddart 1972; see Stoddart 1975a for ral forest (with several subtypes),Hernandia nymphaeifolia other references), and Aitutaki, an almost-atoll (Fosberg littoralforest, Barringtonialittoral forest, and makateaforest 1975; Townsend 1975; Stoddart 1975b and c). No flora (dominatedby Elaeocarpustonganus and Hernandia moeren- for the entire Cook Islands has been published. Al- houtiana). These types were related, using canonical though there have been some descriptive botanical studies to attributes (wind- correspondenceanalysis, geographical of the makatea islands in the Cook Islands (Sykes 1976a- wardness,elevation, and proximityto the coast or roads) that d, 1980b; Whistler 1988, 1990) and elsewhere in the served as surrogatesfor environmentalvariables (maritime Pacific few of the influence, soil variation, and degree of human disturbance). (Wilder 1934), quantitative analyses The eigenvalues for this direct ordinationwere much lower species assemblages or species/environment relations than for indirect ordination(0.32 vs. 0.71 for the first axis), of native forest have been carried out in the southern indicating that the measured geographical attributescould Cook Islands (Merlin 1985, 1991), or anywhere in the explain only a modest portionof the compositionalvariation. tropical Pacific (e.g. Whistler 1983; Sabath 1977; Kirkpatrick & Hassall 1985) other than Hawaii. Ecological associations on the Pacific islands have Keywords: Canonical CorrespondenceAnalysis; Detrended been altered by both Polynesian and European introduc- CorrespondenceAnalysis; Makatea; Oceania; Ordination; Poly- tions of non-native plants and animals (Olson & James nesia; Tropicalforest; Two-way indicatorspecies analysis. 1982, 1984; Kirch 1982; Merlin 1985, 1991; Steadman 1989; Dye & Steadman 1990). An assessment of the Nomenclature: Whistler(1990). extent of human disturbance is critical to conservation of the indigenous biota of the region (Whistler 1980; Sykes 1983; Dahl 1986; Pearsall in press b). For exam- Introduction ple, many species of landbirds in Polynesia are on the verge of local or complete extinction because of habitat Atiu, Mangaia, Ma'uke, and Miti'aro in the southern disturbance and destruction by humans (Steadman 1989). Cook Islands (Fig. 1) are composed of low central hills A recent study of food resources of native landbirds on of highly weathered volcanic material surrounded by Atiu, Ma'uke, and Miti'aro found that they were almost elevated coral limestone formations known locally as entirely dependent on the fruits and seeds of indigenous makatea. This arrangement of geomorphic features is forest plants (Franklin & Steadman in press). The objec- relatively rare among the Pacific islands (Wood & Hay tive definition of forest community types and ecoclines 1970; Stoddart 1975a; Stoddart, Spencer & Scoffin (sensu van der Maarel 1990) is a prerequisite to biologi- 1985). Alien plant species dominate on the volcanic cal conservation in Polynesia (Pearsall in press a; Franklin 4 Franklin, J. & Merlin, M.

-; Penrhyn

10? Rakahanga Pukapuka Manihiki

Nassau

* . . uwarrow 1: f l...... -: . ., IIIQ: .,.". Suwarrow I --

150 'l-Ij "IV. lll: s

Palmerston ,

Aitutaki .:, Manuae Mitiaro 20? Takutea. COOK ISLANDS At ' Mauke Rarotonga

Mangaia

I I I o ^1 Pno0 4 r 165" 160" 155v

Fig. 1. Map showing location of Atiu, Mangaia,Ma'uke, and Miti'aro in the southernCook Islands. Inset shows the location of the Cook Islandsin the west centralPacific, relativeto new Zealandand Australia.Figure reprinted from Franklin& Steadman(in press) by permissionof Blackwell Scientific Publishing.

& Steadmanin press). (CCA) was used to relate the samples directly to the In the present study, our purpose is two-fold: to measured environmental variables. describe the forest species assemblages on these little- studiedmakatea formations, and to relate species composition gradientsto environmentalvariables. In addi- Study area tion, we wish to answer the following question: given four geomorphologicallysimilar islands, can a general The southernCook Islands lie at the southernedge vegetationclassification system be defined, or do inter- of the persistenttrade wind zone of the South Pacific. island floristic differences have an overridingeffect on Winds are most frequentlyfrom the east and southeast. community composition? We addressedthese objec- Mean annualtemperature is 24 to 26 ?C, with a greater tives by applyingclassification and ordinationmethods diurnalthan annual range. Rainfall is markedlyseasonal to species composition and environmentaldata from 74 with two thirds of the rain falling between November forest sites. Compositionalvariation was relatedto en- and April. The long-term average annual rainfall is vironmentalvariables by calculatingcorrelation coeffi- between 1900 and 2050 mm for the southern Cook cients between the environmentalvariables and ordina- Islands (Thompson 1986). On Atiu, Mangaia,Ma'uke, tion axes derivedby detrendedcorrespondence analysis and Miti'aro the central hills are separatedfrom the (DCA). Finally, canonical correspondence analysis encircling makateaby an annularswampy depression. - Limestone forest vegetation of the Cook Islands - 5

Justoffshore from the makateais a narrowfringing reef. distancefrom the coast andwith leewardness(due south- These islands sharethis raisedlimestone formation with east was considered the extreme windwardposition in makatea in the TuamotuGroup (Wood & Hay 1970). this study);and, (b) soil qualitiesalso vary with distance The makateais an old fringingreef surfacethat has been from the coast. (All sites were located on coralline exposed through tectonic uplift (Wood & Hay 1970; limestone, but inland sites were located on pit and Stoddart1975a; Stoddart,Spencer & Scoffin 1985). pinnacle karst with volcanically derived soil in the fis- The dissectedcentral plateau of Atiu (19? 59' S, 158? sures, while on coastal terracesthe limestone was more 08' W) rises to an elevation of 72 m. The total land area eroded,and the soil containedmore sand.) Depth to and is 2693 ha (Anon. 1983). The makateahas a maximum salinity of the water table are probablycorrelated with elevation of about 30 m, is almost a km wide in some distance from the coast and elevation. Also, introduced places, and covers an area of about 1440 ha. The karst species tended to be located nearerto culturalfeatures surfacehas sinkholes, caves and pinnacles 1 m or more such as roads or tracks. We expected that the species high (Wood & Hay 1970). The cracksin the makateaare composition of sites would be related to these geo- filled with lateritic clay soil that supportsdense forest graphicalvariables. cover 10-15 m tall. Sample site locations were chosen to representthe Miti'aro is 27 km east-northeastof Atiu (19? 52' S, range of environmentalvariables analyzed in the study. 157? 43' W) and about the same size (2226 ha), but Stratificationwas based on field reconnaissanceand air lower lying with much less arable land. The volcanic photos. Sites were sampled using the point-centered centeris composed of four small hills (maximumeleva- quartermethod (Cottam & Curtis 1956) described in tion 15 m), extensive swamps, and a large shallow lake. Mueller-Dombois& Ellenberg(1974) andused by Mer- The makatea is about 1650 ha and has a maximum lin (1985, 1991). In brief, every 10 m along a 90 m elevation of only 10 m. It supportsscrub (ca. 3 m high) transect,the distanceto and diameterof the nearesttree with taller forest only near the inside edge (towardthe larger than 2.5 cm diameterat base (DAB) was meas- swamp) and near the coast on the lee side of the island ured in each quarter,where the quartersare delineated (Sykes 1976b). The surfaceof the makateais generally by the sampling transectand a line perpendicularto it. less rugged than on Atiu. Height of the canopy was also estimated at each point. Ma'uke (20? 09' S, 157? 21' W) is 50 km east- Relative basal area and density of tree species per site southeastof Atiu. It is smallerthan the othertwo islands, (transect)were calculated from the 40 measuredtrees. covering 1842 ha. The centralplateau rises to 29 m, and This method was consistent with our goal of sampling the makateato about20 m. Ma'uke supportsa forest (8- within homogeneousareas of the makateaforest, which 12 m tall) similar to the one on Atiu except that occur in annularrings correspondingto the physiogra- Elaeocarpus tonganusis absent (Sykes 1976c). phy (Wood & Hay 1970;Franklin & Steadmanin press). Mangaia(21? 55'S 157? 58' W) is 116 km south of Species composition tends to remain constant along Atiu, and is 5180 ha. The volcanic centerrises to 169 m transectsoriented parallel to the coast. elevation and the makateato 50-70 m with a steep cliff We sampled a total of 74 sites, 29 on Atiu, 7 on face separatingit from the interiorof the island (Merlin Ma'uke, 18 on Miti'aro, and 20 on Mangaia. (Fewer 1991). sites were sampled on Ma'uke because MM was only In general, the makatea vegetation of the southern able to arrange to spend a short time there.) Most Cook Islandshas been describedas gradingfrom littoral samplingwas done duringJuly 1986 by MM except that strandand coastal scrubcommunities to the tallerforest eight of the Atiu sites were sampled during October of the uplandmakatea. The canopy consists mainly of 1987 by JF. Voucher specimens collected by MM were widespread Polynesian littoral species, and a few deposited in the Bishop Museum, and duplicates were endemics (Whistler 1988, 1990; Merlin 1991). depositedwith A. Whistler,University of Hawaii.Those collected by JF were deposited with M. Simpson, De- partmentof Botany, SDSU. An analysis emphasizing Methods human impact on the vegetation has been published previously for the Mangaiasites (Merlin 1991). We hypothesized, based on field reconnaissance, For each site, the following geographic attributes that environmentalvariation on the makatea has af- were recorded:(1) distance to the coast, (2) elevation, fected the establishmentand survival of forest canopy (3) aspect (direction to the coast) as a measure of species in differentways. Althoughenvironmental fac- leewardness,and (4) distance to the nearestroad, track tors could not be sampledexhaustively, we recognized or othercultural feature (e.g. agriculturalclearing) as an the following gradients: (a) maritime influence (salt index of disturbance.These were all measuredby pac- spray and wind desiccation) decreasedwith increasing ing the distances,or from a topographicmap. An aspect 6 Franklin,J. & Merlin,M.

55341333444433343334 12251741555 1166766 26455615124 5766667 222122127 78624137305602544897451163218312479675701913789094860916520236328358902544 Origin Species I Ficus tinctoria -______-_------4 A* Casuarinaequisetifolia ------32314444443244-4 ----2------2- E Myrsinecheesemanii --11- -111211111121------1------1----1- - I Timoniuspolygamus --11------1--1----1------1------I Planchonella grayana - E Ixora bracteata --2-11-1111------E Geniostomasykesii -- -1 -33333 -11 1------I Santaluminsulare 1 --11---1-11--1 ------I Pisonia grandis --4444334443444444444455444-334444444-----12------1----- 1--4 ---- I Scaevola sericea ------11-1---1 ------I Guettardaspeciosa 31-313344333334431-11112-2134433234334231-11-111--11 -----11-32123431111211 I Pandanustectorius 45333444243413-2-12232121-11-4332-11-2344311-11-1--11 ----1343111 -----1---- I Xylosmasuaveolens --11---1---- 1 ------1-- 1-1------1------I Schleinitziainsularwn I Pipturusargenteus --21 ---1-- 1-1 ------112211-13-21244-----1-1-1 ----211-11-1------I Pittosporumaborescens ------1------2-1-1------1------I Eugenia reinwardtiana ------1----1-1------1------I Celtis pacifica ------3------1------1------I Calophylluminophyllwn ------322131331------1------123--1---- I Glochidionramiflorum ------11-1--1------12 ----1-1-113 ------1--1----1212 -- I Ficus prolixa ------1 -----11-33243------112--1111-11- 2------A Morindacitrifolia 11------1------1-----1-1--1--1-1--1-1------1--1--1----111111-11-1---11-1-1 I Elaeocarpustonganus ------1-1-1 -----3-34443 ------111122-413334523333444311- I Canthiumnbarbatuwn ------1--- 1 ------1------1112-1 ----- 1-1-1-1-1-3111111111-- I Allophylustimorensis ------1 1--1------21-1------A Cordylinefruticosa ------1------11 I Hernandiamoerenhoutiana ------2-----332-1-2------2111113144443131334443333 --- I Hernandianymphaeifolia ------4------1------414554- A Aleuritesmoluccana ------13 ------332-12-344132 ------I Streblusanthropophagorum ------12 A* Cordia subcordata ------1---?-1-- -3 A Inocarpusfagifer R Adenanthera ------1--1-1-- - pavonina - A Cocos nucifera ------111---1-422-43--4----? 13 - A* Hibiscus tiliaceus ------11---3------1-----3- --- I Caesalpinamajor ------1------I Mucunagigantea ------1 ------_- I Homaliumacuminatum R Psidium cattleianum R Psidiumguajava ------1 ------R ------1------Syzygiumjambos ------I Barringtoniaasiatica ------1-1 -----55555555554531------3

IA I IC , i I . , i IA IB IC ID n IV

Fig. 2. TWINSPAN ordereddata table for 74 sites showing linkages based on similarityof site scores (columns) and species scores (rows). Hierarchicallinkages of sites are shown in the bottomrows, andof species in the rightcolumns. Symbols for originof species are: E - endemic; I - indigenous to the Cook Islands;A - aboriginalintroduction; R - recent or historicalintroduction; * - may be indigenous. Numbering of sites (top row) is as follows: 1-29: Atiu sites; 30-47: Miti'aro sites; 48-54: Ma'uke sites and 55-74: Mangaiasites.

of 135? (the prevailing wind direction) was set to zero (TWINSPAN) (Hill, Bunce & Shaw 1975). In this and all aspects were coded 0-180? symmetrically from method site scores and species scores are calculated by southeast (windward) to northwest (leeward). Environ- reciprocal averaging, as in the ordination techniques mental variables were sorted and plotted against quantiles described below. The sites are ordered first by divisive, of the normal distribution to examine for normality. hierarchicalclustering, and then the species are clus- Based on this analysis, aspect was square-root trans- tered based on the classificationof the samples.We set formed and distance to the coast and distance to distur- the pseudo-speciescut levels (equally-weightedclasses bance were log transformed. Sampled elevation values of relative dominance)to 0-5, 5-10, 10-25, 25-75, and were normally distributed and were not transformed. 75-100 percentbasal area. Unfortunately, environmental data were not available We examined the makateaforest communitycom- for the Mangaia sites because the study was initiated positionusing indirectand direct gradient analysis (Noy- there before direct ordination was considered as a data Meir & Whittaker1977; ter Braak 1987a). Ordination analysis method. assumes that species occurrencesare determinedby a The clustering technique applied to the species in few environmentalvariables according to a simple re- sites data was Two-Way Indicator Species Analysis sponse model. In particular,Correspondence Analysis - Limestone forest vegetation of the Cook Islands - 7

6- IA. Littoral 4-- 2 n r- 7 7k H h rm-

IB. Littoralwith Casuarina 8 _ 6- 4- . 2: I m-n-HI - --I

IC. Littoralwith Calophyllum

2rhl n ,-,, Ih , 11 II 1

8- II. Barringtonia 6 - 4- 2-

6 III. H. nymphaeifolia 2 rfT n rHf

8- IV. Makatea 6- 4-

2-- rlT ] 1 n o rM c. n PO - - _M -_o- A ( nM OCo X (D 0 000 0 0 0 0 0 0 0 ( 0 0 0 0 0 0 O 0 O 0 0 0 0 0 0 000 3. Fig. Histograms showing distributionof Distance from Elevation (m) Distance from Aspect from environmentalvariables within the types de- Disturbance (m) Coast (m) Southeast (?) fined in Fig. 2. Undisturbed -* Inland - Leeward -

(CA) assumes unimodal species response curves along environmental gradients (ter Braak 1987a). Detrended Correspondence Analysis (DCA) (Hill & Gauch 1980) is a heuristic modification of CA that corrects for the Table 1. Average density, basal area and canopy height for compression of the ordination axes near their ends and based on TWINSPAN types dendrogram(Fig. 2); n is the the arching of the second axis with respect to the first, number of sites in the type. Values for III included Type and so on (ter Braak 1987a). These ordination tech- transitionalsites 20, 22, 29 and 12 (the latterwere also used in niques do not necessarily yield axes that are stable the average calculated for their respective types). Standard & Peet deviationin parentheses. (Knox 1989; Knox 1989) or that can be inter- preted in terms of underlying environmental variables Type Density Basalarea Height beyond one or two dimensions (Peet 1980) because the n (per 1OOm2) m2/10Om2 (m) environmental factors may not conform to a consistent, geometric model (Oksanen 1988). However, correspond- IA 16 24.5 (16.7) 0.43 (0.50) 4 (2) ence analysis is robust with respect to violations of the IB 12 30.0 (11.4) 0.86 (0.46) 6 (1) IC 9 16.0 (5.1) 0.41 (0.30) 8 (3) underlying statistical model (Hill & Gauch 1980). ID 5 12.5 (3.4) 0.09 (0.01) 4(1) In the indirect gradient analyses, the relative domi- II 12 6.8 (3.5) 1.67 (1.11) 11 (3) nance values were log-transformed in order to decrease III 7 19.8 (10.2) 0.84 (0.54) 11 (4) the influence of the nearly monospecific stands on the IV 17 15.1 (5.3) 0.54 (0.41) 10 (3) ordination, and rare species were down-weighted. Sites 8 Franklin,J. & Merlin,M.

, 19 Q 100- Ss. CSe - ' / / \ 2 ~"* \7IBiu CTp I FpS Cb Ha,

' -3 '"- Ft71 7"20 28E *. E t . 300 .. S00

40. 3 244,14...... aPp . . -lOo- 69 Ba ~~~~~:-20*4S,6i'i . A^St ,.061*GI 1i i 2 6 I

-300 -200 -100 0 100 200 300 400 500 DCA1

Fig. 4. DCA ordinationdiagram for 74 sites (s) and42 species (*) plottedon first (DCA 1) and second (DCA2) ordinationsaxes. Units are average standard deviations of species turnover x 100(Gauch 1982). Numbering of sites is as in Fig. 2. The types (groups of sites) identified in Fig. 2 are circled. Species are labelled by the first letter of genus and species (refer to Fig. 2) with the following exceptions: Ge = Geniostomasykesii, My = Myrsinecheesemanii, Ps = Psidiumguajava, Sc = Schleinitziainsularum.

were analyzed by DCA (detrended by segments) using I. Pandanus/Guettarda littoral forest the computer program CANOCO (ter Braak 1987b). Finally, a direct ordination technique, canonical corre- The first division in the dendrogram separates the spondence analysis (CCA), was performed using littoral forest sites dominated by Pandanus tectorius CANOCO. CCA constrains the axes to be linear combi- and Guettarda speciosa from all other sites. The major- nations of environmental variables, and maximizes the ity of the sites on Miti'aro (sites 30-47) and Ma'uke dispersion of species scores by the method of reciprocal (sites 48-54) fall into this category. This group is further averaging using iterative multiple regression of site differentiated into (IA) with Pisonia grandis as a domi- scores on environmental variables (ter Braak 1986, nant; (IB) also with Casuarina equisetifolia, considered 1987b). Ter Braak (1986) suggests using DCA and to be an aboriginal introduction in this study; (IC) also CCA together to see how much of the variation in the with Calophyllum inophyllum; and (ID) without Pisonia species data is accounted for by the environmental data. grandis or C. inophyllum but with Ficus prolixa and The Mangaia sites were included in the CCA as passive Pipturus argenteus as codominants (this group com- samples because environmental data were not available. posed only of sites from Mangaia). It has been sug- gested that C. inophyllum is rare on Mangaia as a result of human impact (Merlin 1991), but it is not known if Results the other differences between IC and ID are of ecological or biogeographical significance. Inspection of the dendrogram produced by TWIN- SPAN (Fig. 2) reveals that sites tend to cluster into four main groups: - Limestone forest vegetation of the Cook Islands - 9

C 1~~~~~^ ^ \ \ *Mc~~?~M mm 18,64,49 1 Cb 50- 1.' 70 60 .20 68,27 IA 41 37 a51S'' k 0 j 0 ...... ' S^ 45 45 * 19 -50- ^46 APg

-100-

Er CeC Xl /12 22' - M i50 43,21,53,11 S<- i 47,4,5,26 74 fo. 15 \ -200- 39,38 s Tp (nor-250 ,Tphwest- H2 -250 -200 -150 -100 -50 0 50 100 150 200 250 CCA 1

Fig. 5. CCA ordination diagram showing sites (.), species scores (*) and environmental variables (vectors with circled labels), plotted on theon first(CCA1) and second (CCA2) ordinations axes. See captionof Fig.4 forexplanation of specieslabels. Environmental variablesare labeled: U = undisturbed(distance from disturbance); E = elevation;I = inland(distance from coast); L = leewardness (northwest aspect).

II. Barringtonialittoral forest basal area and taller trees, and IC is composed of lower density stands. Type ID consists of short, sparse stands This type consists of almostpure standsof Barring- with very low basal area. Type II is composed of open toniaasiatica andwas sampledon all islandsbut Miti'aro stands of Barringtonia asiatica with very high basal (although site 41 from Miti'aro is transitionalbetween area.Type III (Hernandianymphaeifolia littoral forest) types II and IV). is similar in structureto IB, and makatea forest (Type IV) is similarto IC. It has been suggestedthat the point- III. Hernandianymphaeifolia littoral forest centered quarter(PCQ) sampling method gives higher basal area estimates than fixed-area plot methods be- This type is dominatedby Hernandianymphaeifolia cause basal area is overestimatedin sites with a large and is composed of sites from Atiu and Mangaia, the rangeof diameterclasses (Mark,Dickinson & Fife 1989 two larger,higher islands. and references therein). PCQ-derivedbasal area estimates in this study are somewhat higher than those IV. Makateaforest calculatedfrom plot methodsfor similarforests in Tonga and Hawaii (D. Drake unpubl.data), and one should be This type is dominated by Hernandia moeren- cautious when comparing these figures to estimates houtiana and Elaeocarpus tonganus, and is also com- based on other sampling methods. The basal area for posed of sites from Atiu and Mangaia (with one site type II is high because individual Barringtonias have from Miti'aro,41, mentionedabove). large basal diameters(one was 244 cm). The patternsof environmentalvariables within types Table 1 shows that these types differ structurallyas (Fig. 3) are ambiguousbecause of the small variancein well, although the sample size is small and variance the observed values (especially distance to disturbance high. Among the littoralforest type (I), IA is composed and to the coast), but some trends are evident. Littoral of dense standsof small shorttrees, while IB has higher types IB, II and III only occurredclose to the coast and 10 Franklin, J. & Merlin, M.

Table 2. Comparisonof the results of DetrendedCorrespond- Table 3. Intrasetcorrelations of environmentaldata with the ence Analysis (DCA), Canonical CorrespondenceAnalysis firstthree species axes of CanonicalCorrespondence Analysis (CCA), and Detrended(by segments) CanonicalCorrespond- (CCA).The environmentalvariables were standardizedto unit ence Analysis (DCCA) of makateavegetation data (42 species varianceafter some were transformed(see text). in 74 sites); eigenvalues and species-environmentcorrelation coefficients for the four species ordinationaxes. Correlationcoefficients Axis 1 2 3 Axis Environmentalvariables 1 2 3 4 Undisturbed - 0.44 - 0.09 0.02 Eigenvalues Elevation 0.28 0.34 - 0.05 Inland - 0.39 0.27 0.25 0.10 DCA 0.71 0.33 0.18 Leeward 0.16 - 0.02 0.42 CCA 0.32 0.15 0.07 0.05 DCCA 0.32 0.14 0.05 0.03

Species-environmentcorrelation coefficients 0.51 0.41 0.17 DCA 0.55 indicate that the measured environmental variables do CCA 0.65 0.55 0.46 0.42 DCCA 0.67 0.56 0.42 0.42 account for some of the species variation. However, the eigenvalues for the CCA axes are substantially lower than for DCA (Table 2) suggesting that important site variables have not been measured. The correlations of the environmental variables with IB only at the lowest elevations, while types IA and IC the CCA axes (Table 3) provide the following interpre- (with Calophyllum inophyllum) also occur at higher tation for the CCA ordination diagram shown in Fig. 5: elevations, further inland, and on undisturbed sites. Type axis 1 is increasingly coastal, disturbed and leeward, IA tends to occur more often on windward aspects and and axis 2 shows increasing elevation and distance from Type II on leeward aspects. Makatea forest occurs at the coast. Axis 3 (not shown in Fig. 5) is increasingly higher elevations more frequently than any of the littoral leeward. However, intraset correlations are low (Table types except IC; but, makatea forest occurs more fre- 3). Some arching is apparent in the CCA biplot (Fig. 5, quently on leeward aspects than IC. axis 2 has a quadratic relationship to axis 1), but detrended When plotted on the first two DCA ordination axes CCA (detrended by segments) yielded essentially the (Fig. 4), the sites tend to group into the types and same results (DCCA, Table 3) and pattern of species subtypes described above. The ordination biplot dis- and sites distributed on the ordination axes (not shown). plays graphically which sites are transitional in their In the CCA ordination (Fig. 5), the position of sites composition between the types differentiated by cluster- relative to each other is similar to the DCA ordination ing. The first DCA axis is associated with increasing (Fig. 4), although the dispersion of sites is different. Barringtonia (Ba) and decreasing Casuarina (Ce), and Type I sites occupy more of the ordination space defined the second axis with increasing Hernandia nymphaeifolia by the first two axes, while Type II occupies less. The (Hn) and decreasing Calophyllum inophyllum (Ci) and only major difference in the pattern of sites in the two Ficus prolixa (Fp). Table 2 shows that eigenvalues, at ordinations was that Types IC and ID did not occur in least for the first DCA axis, were relatively high (this separate groups in the CCA ordination. This was pre- ordination axis captured a large portion of the variation sumably because the Mangaia sites (comprising ID) in species composition among sites), but the species- were passive and therefore had no influence on the environment correlation coefficients were low for the extraction of the ordination axes, but were added after- DCA axes. The species-environment correlation is "the wards using transition formulae (ter Braak 1987b). The correlation between the site scores which are weighted position of the groups of sites relative to the environ- species scores and the site scores which are linear com- mental vectors (Fig. 5) provides support for the patterns binations of environmental variables" (ter Braak 1986 inferred from Fig. 3. Type IB is more disturbed and p. 1169). The ordination axes based on the species data coastal than Type IA, and Type IC occurs at higher alone were not strongly related to the measured environ- elevation than IA and B. Type IV occurs on leeward mental variables. aspects. Note that Barringtonia asiatica (Ba) and The species-environment correlations are slightly Hernandia nymphaeifolia (Hn) tend to occur in coastal higher for the CCA axes (Table 2). This is expected as and leeward sites, the introduced species Aleurites the axes in CCA are calculated based on species scores moluccana (Am), Adenanthera pavonina (Ap), Inocar- and environmental variables. Correlation coefficients pus fagifer (If), Morinda citrifolia (Mc), and Hibiscus - Limestone forest vegetation of the Cook Islands - 11

tiliaceus (Ht) in disturbedinland sites, and the indig- scale thatcould be detectedusing this samplingmethod, enous or endemic species Santalum insulare (Si), and therefore that disturbed and undisturbedclasses Geniostomasykesii (Ge) andMyrsine cheesemanii (My) could be differentiated. in undisturbedsites. Hernandiamoerenhoutiana (Hm) Franklin& Steadman(in press) defined physiogno- and Elaeocarpus tonganus (Et) tend to occur at higher mic vegetation types using aerialphotographs based on elevation, inland sites. tone, textureand topographic position for the purposeof mappingbird habitat,and their classification included: (a) littoralforest (within 150 m of coast), (b) Hernandia Discussion nymphaeifolialeeward littoralforest, (c) coastal forest (50-200 m from coast), (d) makatea forest (more than The species groups and the species-environment 100 m from the coast and on the makatea),(e) disturbed relationshipsidentified in this study are similarto those makatea forest (indicatedby the presence of Aleurites describedin otherstudies in the region. Whistler(1980) moluccanawhich has a light tone on air photos), and (f) stated that littoral forest species composition is deter- Barringtoniaforest (which has a darktone and smooth mined primarily by substratum,and identified four texture on air photos). The present study revealed no subcommunitiesin AmericanSamoa dominatedby: (a) 'coastal forest' of distinctcomposition on these islands, Pandanus(rocky, unprotected shores), (b) Pisonia (sandy butonly an areatransitional between littoral and makatea shoreswith seabirdguano), (c) Barringtonia(coral plates forest (e.g. sites 19, 22, 7, 9, 16, 17, 65, 67 and 70). The andrubble), and (d) mixed (in some areasdominated by quantitativedescription of the compositionof the types Hernandianymphaeifolia). Whistler (1983) andPearsall derived in the present study will be used to revise the (in press a) identifiedBarringtonia, Pisonia, Hernandia classification by deleting the coastal forest type. The and mixed littoralforest in WesternSamoa. observation that stands of Aleurites moluccana were Ourmakatea forest would be a type of coastalforest, clearly visible on 1:30 000 airphotos suggests thatmore defined by Whistler(1980) as lying immediatelyinland extensive field sampling would result in the identifica- from littoralforest but having differentspecies compo- tion of a disturbedmakatea forest type. Certainlyit is sition. In the Samoa study,as in ours, therewere several useful to mapidentifiable stands of Aleuritesmoluccana, 'littoral' species found in this type (e.g. Calophyllum if only because they are not used for food by native inophyllum,Guettarda speciosa and Pandanus tectorius). landbirds. The makatea forest type, dominated by Elaeocarpus Littoral forest species (for example Barringtonia tonganusand Hernandia moerenhoutiana, has not been andHernandia) tend to be salt waterdispersed, or, in the described for other areas in Polynesia, however it is case of Pisonia, the sticky seeds are dispersed on the composed of species that are widespreadin coastal and feet of seabirds.In contrast,coastal forest species (such montaneforest in the region. as Eleaocarpus) are primarilylandbird-dispersed (van In a separatecluster analysis of only the Mangaia der Pijl 1972). A study based on a very limited sample sites, Merlin (1991) identified (a) Pandanus scrub sites from Atiu, Ma'uke and Miti'aro showed that the two (correspondingto TypeID in this study);(b) Barringtonia dominantmakatea forest trees, Elaeocarpus tonganus asiatica forest (correspondingto II); and (c) native and Hernandia moerenhoutiana,are both importantin forest (correspondingto IV). Merlin (1991) differenti- the diet of two native landbirds,Pacific Pigeon (Ducula ated disturbedand undisturbednative forest, the former pacifica) and Cook Islands Fruit-Dove (Ptilinopus characterized by the presence of Cocos nucifera, rarotongensis), as are other endemic or indigenous Aleuritesmoluccana, and Morindacitrifolia. However, makatea forest species such as Myrsine cheesemanii thereis new palynologicalevidence thatCocos nucifera (Franklin & Steadman in press). Fruits of a littoral is native,not an aboriginalintroduction, on these islands species, Guettardaspeciosa, are also extremely impor- (Parkes1990). A disturbedmakatea forest type was not tant in their diet. distinguishedin the clusteranalysis or ordinationsin the Althoughthe objective definitionof discretevegeta- present study. Most makatea sites sampled contained tion types is importantfor vegetation and habitatmap- some Aleuritesmoluccana, and Morinda citrifolia, but ping, the ordinationsshow both strongdifferentiation of M. citrifolianever accountedfor > 5%basal area,andA. the four majortypes based on species composition, and moluccanamade up > 25% basal areain only two sites. continuousvariation in species abundanceamong some One could conclude that all of the makatea sites are types (IC, ID and IV, and IA and IB). An understanding disturbedto some extent, although introducedspecies of the variationswithin and transitionsbetween vegeta- are not dominantat this samplingscale. Alternatively,a tion types is also importantfor ecosystem inventory largernumber of samplesmight reveal thatthe distribu- (Noss 1987). This variation can be related to plant tion of introducedspecies on the makateais patchy at a species turnover along environmentalgradients using 12 Franklin,J. & Merlin, M. environmentaldata (e.g. the transitionfrom IA to IB The inter-islandpattern of greatestecological inter- may be related to a disturbancegradient, and from IC est is the absenceof the makateadominants Elaeocarpus andD to IV relatedto increasingdistance from the coast tonganusand Hernandia moerenhoutiana from sample and leewardness). However, in our study the relation- sites on the smaller islands, Ma'uke and Miti'aro (al- ship between environmentalvariables and species com- though H. moerenhoutiana is known to occur on position is somewhat weak. There are several possible Miti'aro),perhaps indicating the lack of suitablehabitat. explanationsfor this. The remaining mysterious pattern is the absence of The geographicalvariables that were measuredmay Pisonia grandis as a littoral dominanton Mangaia (al- not have adequately sampled the underlying environ- though others have noted that it is locally abundant mental gradients, either because the spatial sampling there;A. Whistlerpers. comm.). In spite of the fact that scale (100 m transects)was too coarse,or the geographi- sites from an island tended to cluster together, general cal attributeswere not good surrogatesfor environmen- patternsof the distributionof species on all four islands tal variability(e.g. soil and micrometeorologicalprop- were revealed. Most types occurred on at least two erties). Many studies have shown soil propertiesto be islands. In the only case where a type was restrictedto heterogeneousover a distanceof a few meters(Robertson one island (due to the presenceor absence of a species), et al. 1988; Palmer & Dixon 1990) and this would be it occurredas a subtype (e.g. ID on Mangaia)of a more especially true for the makatea where soil collects in general category (I, Pandanus/Guettardalittoral for- pockets on the pit and pinnacle karst(Harvey, Davis & est). In other cases where a type was present on only Gale 1988). some of the islands, it could be explained in terms of Also, the makatea is small in extent, the geographi- environmentalor terraindifferences (e.g. types III and cal distancesare short(although the environmentalgra- IV occur on Mangaia and Atiu which are much larger, dients may be steep), and the canopy includes many higher makateaislands than Ma'uke and Miti'aro). cosmopolitan littoral species. Biotic factors (dispersal The ruggedmakatea on Atiu, Mangaia,Ma'uke and ability and competition)may have a great influence on Miti'aro supports several forest associations that are species composition at the spatial scale of the sample distinct at our sampling scale where alien species are sites. Withtheir large heavy seeds, Barringtoniaasiatica present but not dominant,as has been found for more and Aleurites moluccana tend to cluster among them- continentalaustral forests in Australia,Madagascar and selves. Barringtoniatends to occur in pure stands,pre- New Zealand (Holland & Olson 1989). Quantitative sumablybecause it shadesout seedlings of otherspecies descriptionsof their composition can be used in map- (Amerson, Whistler & Schwaner 1982; U. Simpson ping and monitoringthese vegetation associations and pers. comm.), and is probably established in cohorts the fauna they support. after stormevents (Merlin 1991). Stochastic processes (colonization events and dis- turbanceregimes) may determine the presence or ab- Acknowledgements. Supportfor this projectwas providedby sence of a species on a particularisland. However, the National Geographic Society (grant 3681-87 to D. S. the Institute although only 10 of the 38 indigenous or aboriginally Simonett and JF), California Space (grant CS- 1087 to J. E. Estes and JF), the National Science Foundation introducedwoody species sampled in this study were (grantBSR-8607535 to D. W. Steadman)and the University on all four 28 of them are known to sampled islands, of Hawaii Office of ResearchAdministration (grant to MM). occur on all four islands (A. Whister unpubl. data; We gratefully acknowledge the assistance of the following Sykes 1976c). Therefore, it is a sampling artifactthat people; G. McCormack,V. Tupa and T. Utanga (Rarotonga); rarerbut widespreadspecies were not foundin our sites. M. Boaza and U. Simpson, (Atiu); N. Pouao and T. Tetava For example, on Ma'uke, where only seven sites were (Miti'aro);and numerous other Cook Islanders,especially the established, several common species, known to occur residentsof Atiu,Mangaia, Ma'uke, and Miti'aro. Plant voucher there, were not sampled (Hernandia nymphaeifolia, specimens were identified by W. A. Whistler;S. E. Schubel, E. D. andV. CarterSteadman assisted with Calophylluminophyllum, Aleurites moluccana, Pisonia Moore, vegetation sampling.We thankK. Bridges, F. Davis, D. Drake,J. Estes, grandis and Canthium While 10 species barbatum). D. Mueller-Dombois,D. Simonett, D. W. Steadman,W. R. were on one of the two Atiu only sampled largerislands, Sykes and A. Whistlerfor theirmany contributionsincluding or Mangaia, six of those occur on all four islands, and commentson the manuscript.R. K. Peet andthree anonymous two more on at least two islands. Of the species sampled reviewers greatlyimproved the manuscriptwith their sugges- on only one island, only Ficus tinctoria was dominant tions. (>75% basal area) at any sample (site 71 on Mangaia). In summary,the inter-islandpatterns of compositiondid not have a primaryeffect on the ordinationor the definition of types. - Limestone forest vegetation of the Cook Islands - 13

References methodsof vegetationecology. JohnWiley and Sons, New York. Anon. 1983. Maps of the Cook Islands. Rarotonga, Cook Noss, R. F. 1987. From plant communities to landscapes in Islands. Survey Departmentof the Cook Islands. conservationinventories: a look at The Nature Conserv- AmersonJr., A. B., Whistler,W. A. & Schwaner,T. D. 1982. ancy (USA). Biol. Conserv. 41: 11-37. Wildlife and wildlife habitat of American Samoa. U. S. Noy-Meir, I. & Whittaker,R. H. 1977. Continuousmultivari- Departmentof the Interior, Fish and Wildlife Service, ate methods in community analysis: some problems and Washington,D.C. developments.Vegetatio 33: 79-98. Cheeseman, T. G. 1903. The flora of Rarotonga, the chief Oksanen, J. 1988. A note on the occasional instability of island of the Cook Group.Trans. Linn. Soc. 2: 261-313. detrendingin correspondenceanalysis. Vegetatio 74: 9- Cottam,G. & Curtis,J. T. 1956. The use of distancemeasures 32. in phytosociological sampling.Ecology 37: 454-460. Olson, S. L. & James, H. F. 1982. Fossil birds from the Dahl, A. L. 1986. Review of the Protected Area System in Hawaiian Islands: evidence for wholesale extinction by Oceania. UNEP andIUCN Commissionon NationalParks Man before western contact. Science 217: 633. and ProtectedAreas, Gland, Switzerland. Olson, S. L. & James, H. F. 1984. The role of Polynesians in Dye, T. & Steadman,D. W. 1990. Polynesian ancestors and the extinctionof the avifaunaof the HawaiianIslands. In: their animal world.Am. Sci. 78: 207-215. Martin,P. S. & Klein, R. G. (eds.) Quaternaryextinctions, Fosberg,F. R. 1975. Vascularplants of Aitutaki.In: Stoddart, pp. 768-780. University of Arizona Press, Tucson. D. R. & Gibbs, P. E. (eds.) Almost-atoll of Aitutaki:reef Palmer,M. W. & Dixon, P. M. 1990. Small scale environmen- studies in the Cook Islands, S. Pac. Atoll Res. Bull. 190: tal heterogeneityand the analysis of species distributions 73-84. along gradients.J. Veg. Sci. 1: 57-65. Fosberg, F. R. & Sachet, M.-H. 1972. Plants of southeastern Parkes,A. 1990. Humanimpact and environmentalchange in Polynesia 2. Micronesica 8: 43-49. islands of the SouthwestPacific. Abstractsof the V Inter- Franklin,J. & Steadman,D. W. In press. The potential for nationalCongress of Ecology, Yokohama,August 23-30, conservationof Polynesianbirds through habitat mapping 1990. and species introduction.Conserv. Biol. Pearsall, S. In press a. A system of representative nature Gauch Jr., H. G. 1982. Multivariateanalysis in community reservesfor WesternSamoa. FourthSouth Pacific Confer- ecology. CambridgeUniversity Press, Cambridge. ence on Nature Conservationand Protected Areas. Port Harvey,L. E., Davis, F. W. & Gale, N. 1988. The analysis of Vila, Vanuatu,4-12 September1989. class dispersionpatterns using matrixcomparisons. Ecol- Pearsall, S. In press b. A biological diversity information ogy 69: 537-542. networkfor the South Pacific. FourthSouth Pacific Con- Hill, M. O., Bunce, R. G. H. & Shaw, M. W. 1975. Indicator ference on NatureConservation and ProtectedAreas. Port species analysis: a divisive polythetic method of classifi- Vila, Vanuatu,4-12 September1989. cation, and its application to a survey of native pine Peet, R. K. 1980. Ordinationas a tool for analyzing complex woodlands in Scotland.J. Ecol. 63: 597-614. data sets. Vegetatio42: 171-174. Hill, M. 0. & Gauch Jr., H. G. 1980. Detrendedcorrespond- Philipson,W. R. 1971. Floristicsof Rarotonga.Bull. R. Soc. N. ence analysis:an improvedordination technique. Vegetatio Z. 8: 49-54. 42: 47-58. Robertson,G. P., Huston,M. A., Evans, F. C. & Tiedje, J. M. Holland,P. & Olson, S. 1989. Introducesversus native plants 1988. Spatial variabilityin successional plant communi- in australforests. Prog. Phys. Geogr. 13: 262-293. ties: patternsof nitrogen availability.Ecology 69: 1517- Kirch, P. V. 1982. The impact of prehistoricPolynesians on 1524. the Hawaiianecosystem. Pac. Sci. 36: 1-14. Sabath,M. D. 1977. Vegetation and urbanizationon Majuro Kirkpatrick,J. B. & Hassall, D. C. 1985. The vegetation and Atoll, MarshallIslands. Pac. Sci. 31: 321-333. flora along an altitudinaltransect through tropical forest at Steadman,D. W. 1989. Extinction of birds in eastern Poly- Mount Korobaba,Fiji. N. Z. J. Bot. 23: 33-46. nesia: a review of the record and comparisonwith other Knox, R. G. 1989. Effects of detrending and rescaling on Pacific island groups.J. Archaeol. Sci. 16: 177-205. correspondenceanalysis: solution stability and accuracy. Stoddart,D. R. 1972. Reef islands of Rarotonga,with a list of Vegetatio 83: 129-136. vascularflora by F. R. Fosberg.Atoll Res. Bull. 160: 1-14. Knox, R. G. & Peet, R. K. 1989. Bootstrappedordination: a Stoddart,D. R. 1975a. Scientific studies in the SouthernCook method for estimating sampling effects in indirectgradi- Islands:Background and bibliography.In: Stoddart,D. R. ent analysis. Vegetatio 80: 153-165. & Gibbs, P. E. (eds.) Almost-atollof Aitutaki:reef studies Mark, A. F., Dickinson, K. J. M. & Fife, A. J. 1989. Forest in the Cook Islands. S. Pac. Atoll Res. Bull. 190: 1-30. succession on landslides in the Fiord Ecological Region, Stoddart,D. R. 1975b. Vegetationand floristics of the Aitutaki southwesternNew Zealand.N. Z. J. Bot. 27: 369-390. motus. In: Stoddart,D. R. & Gibbs, P. E. (eds.) Almost- Merlin,M. D. 1985. Woody vegetationin the uplandregion of atoll of Aitutaki:reef studies in the Cook Islands.S. Pac. Rarotonga,Cook Islands.Pac. Sci. 39: 81-99. Atoll Res. Bull. 190: 87-116. Merlin, M. D. 1991. Woody vegetation on the raised coral Stoddart,D. R. 1975c. Mainlandvegetation of Aitutaki. In: limestone of Mangaia, southernCook Islands. Pac. Sci. Stoddart, D. R. & Gibbs, P. E. (eds.) Almost-atoll of 45: 131-151. Aitutaki: reef studies in the Cook Islands. S. Pac. Atoll Mueller-Dombois, D. & Ellenberg, H. 1974. Aims and Res. Bull. 190: 117-122. 14 Franklin, J. & Merlin, M.

Stoddart, D. R., Spencer, T. & Scoffin, T. P. 1985. Reef ter Braak, C. J. F. 1987b. CANOCO (Version 2.1). TNO growth and karst erosion on Mangaia, Cook Islands: A Instituteof Applied ComputerScience, Statistics Depart- reinterpretation.Z. Geomorph.57: 121-140. ment. Wageningen,the Netherlands. Sykes, W. R. 1976a. Vegetationof Atiu. UnpublishedReport, Thompson, C. S. 1986. The Climate and Weather of the N. Z. Dept.Sci. Indust.Res., BotanyDivision, Christchurch, Southern Cook Islands. N. Z. Met. Serv. Misc. Publ. New Zealand. 188(2). New Zealand Meteorological Service, Welling- Sykes, W. R. 1976b. Vegetation of Miti'aro. Unpublished ton, New Zealand. Report, N. Z. Dept. Sci. Indust. Res., Botany Division, Townsend,C. C. 1975. Bryophytesfrom the Cook Islands.In: Christchurch,New Zealand. Stoddart, D. R. & Gibbs, P. E. (eds.) Almost-atoll of Sykes, W. R. 1976c. Vegetation of Ma'uke. Unpublished Aitutaki:reef studies in the Cook Islands, S. Pac. Atoll Report, N. Z. Dept. Sci. Indust. Res., Botany Division, Res. Bull. 190: 85. Christchurch,New Zealand. van der Maarel,E. 1990. Ecotones andecoclines aredifferent. Sykes, W. R. 1976d. Vegetation of Mangaia. Unpublished J. Veg. Sci. 1: 135-138. Report, N. Z. Dept. Sci. Indust. Res., Botany Division, van der Pijl, L. 1972. Principles of dispersal in higherplants. Christchurch,New Zealand. 2nd ed. Springer-Verlag,New York. Sykes, W. R. 1980a. Botanicalscience. In: Kinloch,D. I. (ed.) Whistler, W. A. 1980. The vegetation of Eastern Samoa. Bibliography of research in the Cook Islands, pp. 9-68. Allertonia 2: 45-190. New ZealandMan and the BiosphereReport No. 4. DSIR, Whistler, W. A. 1983. Vegetation and flora of the Aleipata Lower Hutt, New Zealand. Islands,Western Samoa. Pac. Sci. 37: 227-249. Sykes, W. R. 1980b. Sandalwoodin the Cook Islands.Pacific Whistler,W. A. 1988. The unique flowers of Polynesia:The Science 34: 77-82. Cook Islands.Bull. Pac. Trop.Bot. Garden 18: 89-98. Sykes, W. R. 1983. Conservationon South Pacific islands. In: Whistler,W. A. 1990. The ethnobotanyof the Cook Islands: Given, D. R. (ed.) Symposiumon Conservationof Plant the plants,their Maori names, and theiruses. Allertonia5: Species and Habitats. pp. 37-42. 15th Pacific Science 347-419. Congress, Dunedin, New Zealand. Wilder, G. P. 1931. Flora of Rarotonga.B. P. Bishop Mus. ter Braak,C. J. F. 1986. Canonicalcorrespondence analysis: a Bull. 86: 1-113. new eigenvectortechnique for multivariatedirect gradient Wilder,G. P. 1934. Flora of Makatea.B. P. Bishop Mus.Bull. analysis. Ecology 67: 1167-1179. 120: 1-49. ter Braak,C. J. F. 1987a. Ordination.In: Jongman,R. H., ter Wood, B. L. & Hay, R. F. 1970. Geology of the CookIslands. Braak, C. J. F. & van Tongeren, 0. F. R. (eds.) Data New Zealand Geologic Survey, N. Z. Dept. Sci. Indust. analysis in communityand landscapeecology, pp. 91-173. Res., Wellington, New Zealand. Pudoc, Wageningen.

Received 9 October 1990; Revision received 9 August 1991; Accepted 22 September1991.