Environmental requirements trump genetic factors in explaining narrow endemism in two imperiled Florida sunflowers


The mechanisms generating narrow endemism have long been of interest to biologists, with a variety of underlying causes proposed. This study investigates the origins of narrow endemism of two imperiled Florida endemics, Helianthus carnosus and Phoebanthus tenuifolius, in relation to a widespread sympatric close relative, Helianthus radula, as well as other members of the genus Helianthus. Using a combination of population genetics and environmental niche modeling, this study compares evidence in support of potential mechanisms underlying the origin of narrow endemism, including environmental specialization versus inbreeding, loss of diversity, or other predominantly genetic factors. The two narrow endemics were found to be comparable in genetic diversity to H. radula as well as other widespread Helianthus species, with little to no evidence of inbreeding. Environmental niche modeling indicates that distributions of both narrow endemics are strongly related to temperature and precipitation patterns, and that both endemics are threatened with severe reductions in habitat suitability under projected climate change. Evidence indicates that genetic factors likely are not the cause of narrow endemism in these species, suggesting that these species are likely ecological specialists and thus historical narrow endemics. This makes both species vulnerable to climate change, and of immediate conservation concern.

Publication Title

Conservation Genetics