Merrill: Distribution of Dipterocarpaceae 31 



-Palawan-Calamian group to the north. This connection 

 was apparently earlier, more pronounced, and longer continued 

 than the connections between Mindanao and Celebes, Gilolo, the 

 Moluccas, and New Guinea to the south and east. 



5. The dipterocarps were apparently dominant in the Philip- 

 pines as early as the Pliocene, and probably earlier. From the 

 biologic characters of the group it is evident that when they 

 reached the Philippines the entire region was a forested one. 



6. After the earlier connections with Borneo were broken 

 there were later definite connections between Borneo and, 

 apparently, the Zamboanga Peninsula (southwestern Mindanao 

 was during a portion of Pleistocene time a separate island) via 

 the Sulu group to the south, and between the Balabac-Palawan- 

 Calamian group to the north as far as the Mindoro Strait, allow- 

 ing later definite migrations into these regions of Bornean types 

 of animals and plants which could not reach the Philippines 

 proper. 



7. The intermittent isthmuses connecting Mindanao with the 

 islands to the south and southeast have permitted intermi- 

 grations here, and Celebesian, Moluccan, Papuan, and a distinctly 

 important series of Australian types have thus traveled the 

 longer distance, many to northern Luzon and even into the 

 Babuyan Islands, rather than the shorter distance into western 

 Malaysia, not having been able to cross the narrow but long- 

 persistent Macassar Strait. 



8. The entire absence of the dipterocarps in Formosa, the 

 slight evidences of biological relationships between Luzon and 

 Formosa, and the fact that, with very few exceptions, none of 

 the Australian and eastern Malaysian types in the Philippine 

 flora reach Formosa indicate clearly that there have been no 

 land connections here since early Tertiary times. 



9. The distribution of birds, reptiles, fresh-water fishes, 

 mammals, and many groups of insects as between eastern and 

 western Malaysia in general conforms to the distribution of 

 the plants. Thus, very many Asiatic types extend as far as 

 the Macassar Strait and, while some cross it, they appear in 

 rapidly dwindling numbers as we go eastward to New Guinea. 

 Likewise, Australian types decrease with as great or greater 

 rapidity as we go westward from New Guinea. In the Philip- 

 pines we find distinct alliances in the mammals and birds with 

 both eastern and western Malaysia, corresponding to similar 

 alliances in the flora. This likewise holds true for the reptiles 

 and insects, while of the fresh-water cyprinoids twenty-seven 



