Morphological diversity under controlled conditions for the Halophila ovalis-H. minor complex and the Halodule uninervis complex from Shark Bay, Western Australia

Abstract

The wide range of leaf types that occurs within the populations of Halophila and Halodule in Shark Bay, Western Australia, was studied for plants under laboratory conditions. In the Halophila ovalis-H. minor complex, two types of plants appeared in the cultures, a large-leaved variant that is similar to typical H. ovalis (R.Br.) Hook. f. and a small-leaved variant that is more similar to H. minor (Zoll.) den Hartog. In Shark Bay, the two variants were not clearly separated because both produced leaves that varied in size, degree of waviness of leaf margins and intensity of anthocyanin pigmentation. In the Halodule uninervis (Forsk.) Aschers. complex, two types of plants, wide- and narrow-leaved variants, appeared in the cultures. In Shark Bay, the narrow-leaved plants differed in leaf width in muddy and silty microsites, but were always narrower than the wide-leaved variants. Only the narrow-leaved Halodule plants produced anthocyanin pigmentation both under field and laboratory conditions. The studies under controlled conditions indicate that the highly diverse leaves in Shark Bay result primarily from environmental influences on two types of Halophila and two types of Halodule.