Abstract Detail

Biogeography

Lichter Marck, Isaac H [1].

Plant evolution on cliffs and bare rocky outcrops: a synthesis and case study in the rock daisy tribe (Perityleae; Compositae).

Sheer cliffs and deep canyons are among the world’s most iconic geological landmarks but our understanding of the enigmatic flora that lives in these vertical-rock landscapes remains fragmented. Bringing together a diffuse literature, I review the previously overlooked biology of cliff plants to find that they represent a globally ubiquitous, specialized, and often endangered component of earth’s flora. I also present a case study of the recent radiation of rock daisies (tribe Perityleae) to preliminarily test hypotheses about the evolution and origins of cliff endemism within a diverse clade of Composites. Given that bare rock outcrops comprise stressful, yet stable habitats, individual plants found on them are overwhelmingly old and slow growing. At the macroevolutionary scale, many bare rock endemic plants form the sister lineage to diverse clades found on decomposed substrates, suggesting that specialization onto bare rock may be a stable strategy with low diversification rates. Still, in landscapes of patchy rock outcrops surrounded by forest, savanna, or desert, insular radiations of rock dwelling plants have developed that parallel the striking diversity of oceanic and sky island archipelagos. The recent radiation of 57 spp. of rock daisies in the genus Laphamia are highlighted as an exemplary case of insular radiation onto isolated cliffs and canyons in arid western North America. Endemism onto bare rocky environments in this group has been an important form of exaptation preceding shifts into deserts and the generality of this pattern is discussed. Today, in landscapes severely impacted by poor management and introduced organisms, such as islands, cliffs serve as refuges for endangered plants. Technological advances for botany in rough terrain, including drone assisted reconnaissance, provide a path forward for understanding why the last individuals of once more widespread plant species persist in precipices. The future success of efforts to save plants from devastating habitat loss may depend on the synthesis of current understanding of the evolution and origins of plants in cliffy habitats.

1 - University of California, Los Angeles, Ecology and Evolutionary Biology, 610 Charles E Young East, Los Angeles, California, 90095, United States

Keywords:
Edaphics
Asteraceae
rare plants
ecological specialization
biogeography
sky islands
perityleae
rock daisies
Evolution.

Presentation Type: Oral Paper
Number: BIOG III001
Abstract ID:787
Candidate for Awards:None