Abstract Detail

Biology of Isoetales, a colloquium in honor of Dr. W. Carl Taylor

Looy, Cindy [1], Duijnstee, Ivo [1].

The ecology and physiology of Paleozoic and early Mesozoic Isoetaleans.

Lycophytes comprise an ancient clade of vascular plants and their living representatives are sister to all other extant vascular plants. The Isoetales, the lineage represented today by >250 species in the genus Isoëtes, date back to the late Devonian (~360 mya). Although separated by hundreds of million million years, cormose isoetaleans such as the late Carboniferous Chaloneria (~310 mya) and early Triassic Pleuromeia (~250 mya) - although larger - had similar growth habits to modern relatives, and lived in environments characterized by high levels of abiotic stress, such as oligotrophy, acidity and periodic flooding. The occupation of such niches probably dates back to the origin of this group. Fossils of young cormose Isoetaleans show a syndrome of morphological traits associated with a suite of specialized adaptations, also found in Isoëtes and other extant (semi)aquatic plants. This so-called isoetid growth form is characterized by succulent leaves in a rosette around a reduced stem or corm, a large root system, aerenchyma or air channels in shoot and roots, and the facultative production of leaves lacking stomata (sometimes even in the terrestrial ecophenotype). The ecophysiological adaptations that required evolution of this morphological syndrome include aquatic Crassulacean Acid Metabolism and/or Lycopsid Photosynthetic Pathway, uptake of soil CO₂ via roots, and slow growth rates. These traits facilitate a life in stressed environments, such as periodically submerged environments that are depleted of nutrients and/or inorganic carbon, and where the competitive pressure is low. Simultaneously, this ecophysiological strategy places major constraints on biomass production and therefore on competitive ability. The exceptional ecophysiological traits associated with the isoetalean lineage explain how they able to flourish in these high stress, low competition environments over the last 360 million years and into the present. Despite their success, the ephemeral nature, and scarcity of such environments on the landscape causes isoetaleans to be rare elements in most paleobotanical or floristic records.

1 - University of California, Berkeley, Integrative Biology, 3040 Valley Life Sciences Bldg #3140, Berkeley, CA, 94708, US

Keywords:
Isoetaleans
Paleozoic
Mesozoic
Ecology
Physiology.

Presentation Type: Colloquium Presentations
Session: C05, Biology of Isoetales, a colloquium in honor of W. Carl Taylor
Location: 101/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 8:30 AM
Number: C05002
Abstract ID:960
Candidate for Awards:None