Bryological and Lichenological Section/ABLS
Villarreal, Juan Carlos , Schuette, Scott , Cargill, D. Christine , Duff, R. Joel , Renzaglia, Karen S. .
New insights on character evolution in hornworts..
Hornworts are an old lineage of land plants with previously unsuspected levels of morphological diversity. Phylogenetic relationships within hornworts are chaotic largely due to the lack of comprehensive analyses dealing with morphology, ultrastructure and molecular systematics in any of the recognized genera. Traditional delimitation of genera and species has relied on limited morphological features, e.g. thallus growth form, pseudoelater morphology and spore color and ornamentation. This presentation examines structural diversity among seven generic segregates of hornworts: Leiosporoceros, Anthoceros, Folioceros, Phaeoceros, Notothylas, Megaceros, and Nothoceros. Taking a comparative approach based on a molecular phylogeny generated from rbcL gene, we will systematically explore variability in the following features of these taxa: 1) Growth form of the gametophyte; 2) Chloroplast number, shape, thylakoid organization and the presence or absence of pyrenoids; 3) Antheridia number per chamber and jacket cell arrangement; 4) Capsule anatomy, especially organization of the sporogenous region, columella and the presence or absence of stomata; and 5) Pseudoelater shape and wall thickenings. Our results challenge the old concept of morphological homogeneity in hornworts and suggest that a re-evaluation of traditional features used to delimit hornwort taxa is warranted.
1 - University of Akron, Biology Department, Akron, Ohio, 443225-3908, USA
2 - Australian National Botanical Gardens, Centre for Plant Biodiversity Research, Canberra, Australian Capital Territory, 2601, Australia
3 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Presentation Type: Paper
Location: Ballroom 3 (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 3:00 PM