NATURE AND EVOLUTION — HAWAIIAN INSHORE FISH FAUNA 353 



slightly longer jaws; a number differ in various details of color pattern; 

 etc. Even within a family no trend of divergence is shown by the various 

 Hawaiian endemic members. Consequently there seems to be no pos- 

 sibility of correlating the morphological peculiarities of Hawaiian en- 

 demics with distinctive features of the Hawaiian environment, e.g., 

 colder water temperatures. One anticipated correlation of this sort is 

 strikingly absent: Hawaiian coral reefs are notably dull colored as 

 compared with those of the central Pacific, yet the fishes seem to be as 

 brightly pigmented as those to the south. It is not, therefore, easy to 

 escape the inference that the morphological peculiarities of Hawaiian 

 endemic fishes are per se non-adaptive. 



Treatment of physiological differentiation is handicapped by the 

 fact that almost nothing is known of the physiological reactions of 

 tropical marine fishes. It might be expected that Hawaiian fishes have 

 become physiologically adjusted to life in colder waters than their more 

 tropical ancestors. There is some indirect evidence for, and none against, 

 this supposition. The best available bit of information in this connec- 

 tion is derived from the spawning seasons of certain Hawaiian fishes. 

 One would expect (Ekman, 1953: 113) that a tropical species living 

 in Hawaii would spawn, at least primarily, during the summer months 

 when water temperatures most closely approximate those of its an- 

 cestral home. However, many Hawaiian fishes spawn primarily or en- 

 tirely in winter at temperatures below those ever reached in more trop- 

 ical regions. One example will suffice. Around Honolulu Pomacentrus 

 jenkinsi spawns from December to March; no ripe females have been 

 taken during the remaining months. At Arno, 10° nearer the equator 

 in the Marshalls, Dr. Strasburg informs me that ripe females of this, 

 same species were taken in July. (Hawaiian specimens of Pomacentrus 

 jenkinsi do not seem to be morphologically distinguishable from their 

 central Pacific counterparts, which further emphasizes the advisabihty 

 of treating the morphological and physiological peculiarities of Ha- 

 waiian forms separately.) 



The restriction of spawning in Pomacentrus jenkinsi (and other 

 similar examples can be given) to winter around Oahu is the reverse 

 of what would be expected, and the explanation for this phenomenon 

 is obscure. Perhaps the Hawaiian populations of P. jenkiiisi have at 

 one time become adapted to waters even colder than exist around 

 Oahu today, e.g., in the Pleistocene, and the winter spawning is merely 

 a holdover from such adaptation. (In any event, the Hawaiian fishes 

 must either have come in since the Pleistocene, under which supposi- 

 tion it is difficult to explain the high degree of endemism, or they must, 

 have been able to survive the Pleistocene water temperatures of Hawaii.), 



