Inbreeding, low genetic diversity, and spatial genetic structure in the endemic Hawaiian lobeliads Clermontia fauriei and Cyanea pilosa ssp. longipedunculata

Abstract

The endemic lobeliad genera Cyanea and Clermontia (Campanulaceae) are among the largest in the native Hawaiian flora, and contain large numbers of endangered and threatened taxa. As a baseline for future studies of rare species in this group, we used RAD markers to estimate genetic variation and spatial genetic structure in single populations of two common species, Cyanea pilosa ssp. longipedunculata on Hawai`i and Clermontia fauriei on Kaua`i. We found low to moderate levels of genetic diversity (He ≈ 0.13 and πall ≈ 0.0013 for both species), consistent with studies of several other island plant species, and substantial inbreeding (Fis ≈ 0.17). There was no evidence for spatial genetic structure in Cyanea, and in Clermontia SGS was weak and restricted to small spatial scales (<10 m). The relative dearth of genetic diversity and high levels of inbreeding in these common lobeliads may reflect pre-existing conditions in this group or selfing in response to a decline in native avian pollinators, raising concerns that inbreeding and loss of genetic variation may be even more severe in rare species of this highly diverse but endangered group.