Experiments on germination and early growth of three rare and endemic species of Hawaiian Tetramolopium (Asteraceae) Original Research Article

We examined the effects of soil moisture, light intensity and seedbed characteristics on the germination and early growth of three rare and endemic Hawaiian species of Tetramolopium Nees (Asteraceae): T. arenarium (A. Gray) Hillebr., T. consanguineum (A. Gray) Hillebr. and T. lepidotum (Less.) Sherff, restricted to the montane dry shrubland community of the Pohakuloa plateau on the island of Hawaii. All three species showed a positive association between germination and soil moisture conditions and higher germination when sown on litter-covered soils than on lava-covered or bare soil. The rarest of the three species, T. lepidotum, generally demonstrated higher germination than its congeners. Light intensity appeared to be the primary factor controlling the successful establishment and growth. However, low light intensity significantly reduced height growth, leaf production and biomass gain of both T. arenarium and T. consanguineum. The presence of herbaceous and woody plants may decrease light intensity and hence the ability of Tetramolopium species to establish and grow, thus restricting recruitment of individuals into the field. Our results indicate that differences in abundance among these species are not related to germination or establishment requirements alone, but rather may reflect multiple aspects of their ecology.