Friday November 17,  2 – 3 p.m.

Join us each month as plant science and conservation efforts are presented by San Diego Botanic Garden’s staff, research associates, colleagues, and guest speakers. This month we will feature Dr. Michael Simpson,  Professor Emeritus at the Department of Biology, San Diego State University and Collections Manager of the SDSU Herbarium.

For over a hundred years, botanists and biogeographers have noticed an interesting pattern: the occurrence of the same plant species or very close relatives on either side of the tropics in North and South America. This biogeographic pattern, known as an American amphitropical disjunction or AAD, represents the repeated formation of North America–South America sister lineages through dispersal and subsequent diversification on separate continents. This phenomenon has been recognized and studied by Asa Gray and Joseph Hooker (1880), Peter Raven (1963), and other prominent botanists.

Since subtribe Amsinckiinae (Boraginaceae), known as the Popcorn Flowers, is one of the richest groups of plants displaying the AAD pattern, it has undergone particular study of late. Michael has been involved with investigating that plant group for years and is therefore in a prime position to take advantage of new and emerging data. The field of systematics (on which Michael wrote the book) now has the phylogenetic, biogeographic, and dating tools to assess the evolutionary and biogeographic history of AAD organisms and to begin relating these with common mechanisms of dispersal, climatic shifts, and geologic events. Finally, Michael will present an upcoming research center that will aid in future research studies of “AADs”. 

SDBG follows local safety and health guidelines, and supports staff and visitors who choose to wear masks as they prefer.


Cost: Free with Garden admission.

Class format: In person, indoors

Please register by November 16, walk-ins welcome, space permitting.