Abstract Detail

Patterns and Processes of American Amphitropical Plant Disjunctions: New Insights

Guilliams, Matt [1], Mabry, Makenzie [2], Hasenstab-Lehman, Kristen [3], Baldwin, Bruce G. [4], Simpson, Michael [5].

Exploring patterns and mechanisms of American amphitropical disjunction in the Amsinckiinae (Boraginaceae).

Amsinckiinae is a diverse and ecologically important subtribe of annual herbaceous or perennial suffrutescent taxa with centers of distribution in western North America and southern South America. Recent analyses show the subtribe to consist of at least two, early-diverging, North American genera (with two additional, monotypic genera of ambiguous placement), plus a large clade of North and South American genera, referred to here as the “core Amsinckiinae.” This core group minimally includes 9 genera: Amsinckia, Cryptantha s.s., Eremocarya, Greeneocharis, Harpagonella, Johnstonella, Oreocarya, Pectocarya, and Plagiobothrys; overall minimum-rank taxonomic diversity in core Amsinckiinae is 330-342 taxa, with 245-257 taxa occurring in North America, 86 in South America, and 4 in Australia. Despite their prevalence on the landscape and a history of botanical research for well over a century, much research remains to be done in Amsinckiinae, especially with respect to biogeographic patterns in the Americas. Here we present new biogeographic analyses spanning the subtribe based on high-throughput genome skimming data, with a focus on inferring the number, directionality, and timing of dispersal events between North America and South America. Using a subset of Amsinckiinae, we then assess putative morphological correlates of dispersal such as reduced fruit size and increased ornamentation using phylogenetic comparative methods. Our analyses show that the common ancestor of the Amsinckiinae was likely from North America, with all inferred dispersals going from North America to South America or Australia. Amsinckiinae taxa have dispersed between North America and South America 17 to 19 times. Model comparison in BioGeoBEARS strongly supports a biogeographic model that includes dispersal-cladogenesis. Therefore, using node age estimates as an approximation for dispersal age, our analyses show strongly non-synchronous dispersals, with most occurring between roughly 5 MYA and 30 KYA. Comparative analyses show a statistically significant negative relationship between dispersal and fruit size, as well as a statistically significant positive relationship between dispersal and some but not all aspects of fruit ornamentation. Taken together, our analyses support the relatively recent development of the American amphitropical disjunction pattern in the core Amsinckiinae, beginning in the Miocene to early Pliocene. Based on the strongly asynchronous dispersal ages and statistically significant relationships between dispersal and morphological features of the fruit that may promote animal dispersal, we favor the hypothesis that the American amphitropical disjunction in the Amsinckiinae, and perhaps more generally, is the result of long-distance dispersal by migratory birds.

1 - Santa Barbara Botanic Garden, Conservation & Research, 1212 Mission Canyon Road, Santa Barbara, CA, 93105, USA
2 - University of Missouri, Division of Biological Sciences, Bond Life Sciences Center, Columbia, MO, 65211, USA
3 - Rancho Santa Ana Botanic Garden, 1500 N. College Avenue, Claremont, CA, 91711, USA
4 - University of California, Berkeley, Jepson Herbarium and Department of Integrative Biology, 1001 Valley Life Sciences Building, Berkeley, CA, 94720, USA
5 - San Diego State University, Biology, 5500 Campanile Drive, San Diego, CA, 92182, USA

Keywords:
Amsinckiinae
long-distance dispersal
amphitropical
Biogeography
Boraginaceae
Cryptantha
Amsinckia
Plagiobothrys
Johnstonella
Pectocarya.

Presentation Type: Colloquium Presentations
Session: C2, Patterns and Processes of American Amphitropical Plant Disjunctions: New Insights
Location: 204/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 2:45 PM
Number: C2006
Abstract ID:764
Candidate for Awards:None