Floral trait evolution and pollination ecology in the Hawaiian lobeliad genus, clermontia (campanulaceae)

Abstract

The Hawaiian lobeliad genus, Clermontia, contains 22 species and 9 subspecies of bird-pollinated shrubs and small trees endemic to wet and mesic forests on the main Hawaiian Islands. This dissertation summarizes four studies concerning the floral trait evolution and pollination ecology of the genus. First, the floral nectar sugar composition, concentration, and nectar standing crop of 21 Clermontia taxa were investigated. All taxa produced nectar with low sugar concentrations dominated by hexoses (glucose and fructose). These results support the assumption that the genus has evolved a bird pollination syndrome. Second, existing distribution projections for 25 Clermontia taxa and six extant nectarivorous passerine taxa, and comparisons between floral and bird bill dimensions, were used to predict interactions between the potential mutualists. Seventeen taxa have floral morphologies (eg., corolla tubes > 27 mm) that likely prevent short-billed nectarivores (five taxa) from acting as pollinators. As a consequence, these plant taxa are likely to be dependent upon 'i'iwi (Vestiaria coccinea) for pollination. Third, the phylogenetic relationships in Clermontia are inferred from six non-coding chloroplast gene regions. The study found that the genus is not monophyletic. Clermontia pyrularia belongs either in the closely related genus Cyanea or is an intergeneric hybrid. The genus appears to have evolved either on Kaua'i or O'ahu with subsequent inter-island colonization events to the younger islands. Petal-like sepals have evolved once, with five or more reversals back to the simple sepal phenotype. Fourth, pollination ecology studies were undertaken to assess if four endangered ornithophilous Hawaiian lobeliads are pollinated by extant nectarivorous passerines at two separate restoration sites; Hakalau National Wildlife refuge on Hawaiʻi Island and Kahanaha¯iki and Pahole Gulches on O'ahu. Two honeycreeper species, 'i'iwi and Hawaiʻi 'amakihi (Hemignathus virens), were infrequent floral visitors to Clermontia lindseyana and Cl. pyrularia at Hakalau. However, both 'i'iwi and 'amakihi were not effective pollinators of either lobeliad species. Introduced Japanese white-eye (Zosterops japonicus) were not effective pollinators of Cyanea superba subsp. superba and Delissea waianaeensis at Kahanaha¯iki and Pahole. All four lobeliad species were significantly pollen limited, suggesting that none of the animals that visited the flowers were effective pollinators.