approximately 9,000 km distant. The motus of Aitutaki, for 

 example, at a similar latitude but further west and wetter, are 

 considered depleted with 45 species. Fanning, at a similar 

 longitude but wetter, has 123 species. Tarawa, 3,900 km to the 

 northwest, receives a similar rainfall but supports 109 species. 



Where an atoll's potential flora is larger, the increased 

 shade and greater protection from wind, salt spray, and storms 

 result in a greater number of natural plant species on its larger 

 motus. However, such atolls are generally inhabited and 

 alterations by both aboriginal and modern man have modified 

 their original flora. Caroline's isolation, variety of islet areas, 

 and minimal human disturbance all contribute to its excellence 

 for the study of atoll evolution. 



The number of species presently established on Caroline's 

 39 motus is 27 (Tables 2, 3). The previous expedition in 

 1 965 (Clapp & Sibley, 1971a) collected 20 species, of which 4 

 were new to the atoll. Their total of 35 species, however, 

 incorporating reports and collections from the 1800's, is 

 misleading. Our total, 6 of which were new records, would 

 have brought the atoll total to 44 (plus about 15 more 

 unestablished, mostly garden, plants). However, following 

 recent custom (see Vegetation section ), we have listed transient 

 orextinct members of the flora separately (Table 1). To include 

 them would obscure the near-pristine nature of the atoll and 

 bias our analyses of species-area relationships. 



The 1 883 drawings of the South Island settlement, inhabited 

 when most of Caroline's species were catalogued, shows that 

 the island was vastly different (compare Pis. 2 and 24). A 

 century ago homes were set amidst large grassy clearings; now 

 the site is completely obliterated beneath shady 21-m-tall 

 coconut palms. Nine exotic plant species have not been seen 

 for over a century (Table 1 ). Evidently most ornamentals and 

 domestic vegetables perished during uninhabited periods. The 

 present residents struggle to keep garden plants alive because 

 of poor soils, irregular rainfall, and foraging land crabs. A few 

 native species might also have been eliminated during the 

 guano and copra-harvesting years. 



Numbers of Indigenous Plants : A comparison of the 

 percentage of indigenous species between different island 

 groups (Table 4) shows that Caroline, with 85%* (N = 23) 

 indigenous, is unusually high. Only 11 of 44 Pacific atolls 

 reviewed have more than 75% of their species indigenous. Of 

 these, nine ( including Caroline) are remote and lack permanent 

 human occupation. 



The Tuamotu Islands ( 149° to 134°W) lie east and south 

 of Caroline, yet they harbor considerably larger floras. Rainfall 

 is similar. Three of them average 121 species (Table 4). 

 averaging 42 indigenous species. When the variables rainfall 

 and distance from a colonization source to the west are 

 considered, the proximity of the Tuamotus to the diverse high 



* Note: Perhaps as high as 93% ; the Digitaria sp., if still extant, 

 is of unknown identity and origin, and Species A has yet to be 

 determined. 



islands of the Societies seems to play a major part in 

 determiningtheir indigenous flora. A similar situation exists in 

 the southern Cook Islands. Caroline and other remote Line and 

 Phoenix Islands are sufficiently isolated from high volcanic 

 islands that they exhibit a much simpler flora. Tahiti, the 

 closest high island (830 km south), is in the wrong direction for 

 direct currents, winds, or vagrant birds to bring seeds to 

 Caroline. 



Composition of the Flora (Tables 2. 3 ): Caroline's botanical 

 affinities lie with other southern Line Islands and the Tuamotus. 

 Although the strand and inland floras consist of pan-Pacific or 

 pantropical species, there are several widespread species and 

 communities that are notably absent. Those that survive have 

 withstood the atoll tests of time — poor soils, scarcity of fresh 

 water, periodic inundation by salt water, intermittent cyclonic 

 storms and hurricanes, harsh climate, and high seedling 

 mortality. Caroline provides an excellent ecological laboratory 

 in which floristic correlations with variations in habitat, motu 

 size, and leeward/windward aspect may be studied. Fosberg 

 (1985) and Sachet (1967) have noted the importance of such 

 details in understanding the biogeography and taxonomy of 

 Pacific plants. 



Caroline's present established flora includes only one 

 weed species (Phyllanthus amarus), represented by a tiny 

 patch less than 2 m : in size. There are two Polynesian 

 introductions (Cocos, Tacca). Pandanus tectorius, Morinda 

 citrifolia, Thespesia populnea, Ximenia americana, and 

 Hibiscus tiliaceus, though indigenous, may have been 

 introduced by Polynesians or 1 9th-century settlers. (See section 

 on Vegetation.) 



Trees: Seven species present. Only three — Pacificwide 

 natives — are widespread: Pisoniagrandis. Morinda citrifolia. 

 and Cordia subcordata. Two are locally abundant: Cocos 

 nucifera and Pandanus tectorius, while the rest, Thespesia 

 populnea and Hibiscus tiliaceus. are rare and limited to the old 

 settlement site. The absence of typical Pacific species such as 

 Calophyllum inophyllum and Guettarda speciosa is notable, as 

 they occur naturally on atolls such as Rangiroa. further east 

 (Stoddart & Sachet. 1969). 



Shrubs: Five species present, at least four indigenous. 

 Only Tournefortia argentea is abundant: its most abundant size 

 class is under4 m. Scaevola and Suriana. tough and widespread 

 elsewhere, are poorly represented on Caroline. It is noteworthy 

 that two varieties of Scaevola sericea are present. Species A is 

 represented by a single individual, Ximenia americana. by a 

 single, large patch. Pemphis acidula. though common on atolls 

 of similar latitude and climate, is absent from most of the Line 

 and Phoenix groups (Stoddart & Gibbs, 1975; Fosberg & 

 Sachet, no date). This may be due to the paucity of its preferred 

 habitats: low rocky substrates (reef rock, conglomerate rock) 

 and sand-gravel ridges. 



Herbs: Fifteen species present, at least 12 indigenous. Of 

 these only seven are common: Heliotropium anomalum. 

 Boerhavia re pens. Portulaca lutea, Laportea ruder alls, 

 Achyranthes canescens, Lepturus repens, and Phymatosorus 



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