Systematic implications of bullate leaves and isozymes for Halophila from Fiji and Western Samoa

Abstract

Small-leaved plants from Fiji and Western Samoa with either bullate or smooth leaves had identical isozyme patterns for five enzyme systems, but plants from Fiji differed from plants of Western Samoa in isozymes of acid phosphatase, esterase and alcohol dehydrogenase. The isozyme patterns for plants of Fiji and Western Samoa differed from those of small-leaved plants of Guam that are referred to Halophila minor (Zoll.) den Hartog and from those of both small- and large-leaved plants of eastern Australia that have been referred to H. ovalis (R. Br.) Hook. f. Plants that had produced bullate or smooth leaves in Fiji or Western Samoa continued to produce bullate or smooth leaves, respectively, under controlled laboratory conditions, but most bullate-leaved plants were induced to produce smooth leaves and some smooth-leaved plants produced slightly bullate leaves under some experimental manipulations, suggesting strong genetic controls with environmental interaction. The small-leaved plants of Fiji and Western Samoa with either bullate or smooth leaves should be separated from H. ovalis, and because of inter-island differences in leaf morphology and isozyme patterning, they should be treated as endemic taxa or placed with other small-leaved populations of the Pacific in H. minor as a polymorphic taxon.