Abstract Detail

A synthesis of new paleontological and phylogenomic perspectives on gymnosperm evolution

Ng, Molly [1], Smith, Selena [2].

Evaluating stasis in Metasequoia (Cupressaceae): linking fossil and modern leaf anatomical traits to climate.

The gross morphology of Metasequoia (Cupressaceae) has remained unchanged since its first appearance in the fossil record and is thus considered to be in stasis. The natural distribution of modern Metasequoia is restricted to central China. In the early Cenozoic it was widespread across the Northern hemisphere, in contrast to its current restricted range, yet it is effectively cultivated in much of the Northern Hemisphere, leaving in question what are the drivers for its biogeographic range constriction and whether it was truly in stasis. Because plant physiognomy has consistently been shown to reflect climate, studying leaves that interact directly with the environment and are frequently preserved in the fossil record provide opportunities to study both stasis and evolutionary history. We use leaf anatomy to investigate links between physiognomy and climate of Metasequoia, incorporating anatomically preserved fossils. Leaves of extant Metasequoia were collected across different climate regimes in North America, Europe, and Asia (70 samples, 19 sites) for anatomical analysis and from fossil localities in North America. Eight anatomical traits were measured including entire transverse area, leaf thickness and width, area of resin canal and vascular bundle, and mesophyll thickness. WorldClim climate data from 19 variables were extracted from each location, assembled, and analyzed in principal components analysis (PCA) and canonical correlation analysis (CCA) with measurements of modern and fossil Metasequoia, and close relatives, Sequoia sempervirens and Taxodium distichum. The first two PCA axes explained 93.1% variance of data, with PC1 (49.7%) showing strong correlation to area of resin canal and PC2 (43.4%) showing strong correlation with area of vascular bundle. Modern samples of Metasequoia and Taxodium overlap in morphospace, while Sequoia occupies its own morphospace, and fossils overlap all three taxa. The first two CCA axes explained 97.4% variance of data, Axis 1 (90.8%) showed highest correlation with diurnal temperature range and Axis 2 (6.6%) showed highest correlation with precipitation during driest periods and temperature of the warmest period. Fossil and extant North American Metasequoia show less variance from each other than from Asian and European samples, suggesting plasticity in North American Metasequoia. Fossils occupy morphospace that is outside extant taxa suggests Metasequoia once occupied a different morphospace, and has not experienced stasis along with restriction of its natural range. Incorporating more Metasequoia fossils from North America and Eurasia will empirically show the extent of disparity of climo-morphospace over geologic time.

1 - 1100 N University Ave , 2534 North University Building , Ann Arbor, MI, 48109, United States
2 - Department Of Earth & Environmental Sciences, 1100 North University Avenue, 2534 CC Little Building, Ann Arbor, MI, 48109, United States

Keywords:
Metasequoia
Cupressaceae
conifer
anatomy
climate
stasis
Evolution
fossil.

Presentation Type: Colloquium Presentations
Session: C04, A synthesis of new paleontological and phylogenomic perspectives on gymnosperm evolution
Location: 102/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 4:15 PM
Number: C04011
Abstract ID:775
Candidate for Awards:None