Bryological and Lichenological Section/ABLS
Schuette, Scott , Renzaglia, Karen .
Evolution of Endospory in Bryophytes.
Spores are the morphological manifestation of a plantís ability to package their genetic information in a desiccation resistant structure and ensure continued existence in harsh, often water-limited environments. Spore wall ornamentation and cellular content are not strictly related to dispersal and perennation but are also linked to patterns of spore germination. In bryophytes, germination patterns are often diagnostic of species and genera. In endosporic germination, cell divisions occur within the spore wall and either progressively decrease cell size or stretch the spore wall. Endospory may occur after the unicellular spore is released into the environment or prior to spore release. The latter condition, known as precocious endospory, is characterized by spores that undergo programmed cell divisions within the capsule, giving rise to multicellular spores. Endosporic germination in released spores is found in taxa from sixteen bryophyte orders, namely the Blasiales, Marchantiales, Pelliales, Metzgeriales, Pleuroziales, Ptilidiales, Porellales, Andreaeales, Scouleriales, Dicranales, Bryales, Orthotrichales, Hedwigiales, Ptychomniales, Hypnales, and Dendrocerotales. Within liverworts, endospory is present in the basal lineages of liverworts excluding the Haplomitriopsida, suggesting this trait evolved some 400 million years ago. Precocious endospory in liverworts is restricted to the orders Pelliales, Porellales and Ptilidiales, thus is interpreted as homoplastic and is a function of the mesohabitats in which these groups evolved. Given the scattered presence of endospory in mosses, the condition most likely had at least three independent origins. Among hornworts, only Dendroceros and Nothoceros exhibit precocious endospory, thus suggesting one origin in this derived assemblage. We demonstrate that endospory is likely plesiomorphic in liverworts, the sister group to all land plants, but has a complex evolutionary history in other bryophytes due to parallel evolution. The occurrence of precocious endospory across bryophytes is suggestive of convergent evolution in epiphytic/ epiphyllous taxa as an adaptation to newly available forest mesohabitats.
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1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 554A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 10:45 AM