Fragments of the earliest land plants

Wellman, Charles H.; Osterloff, Peter; Mohiuddin, Uzma

doi:10.1038/nature01884

Cited by 527 publications

(326 citation statements)

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“…While there is reasonable evidence for thalloid life forms in the early fossil record (Wellman et al 2003;Graham et al 2004;Taylor & Haas 2005), and they are certainly rooted as forerunners of the land plant revolution from their molecular phylogenies, we have little in the way of a fossil record to reconstruct their subsequent diversification. Recently, however, it has been suggested that some leafy liverworts have indeed shown significant speciation since the angiosperms arose (Ahonen et al 2003;Heinrichs et al 2007;Wilson et al 2007), presumably diversifying in the lee of forest canopies, just as it had been posited for ferns (Schneider et al 2004).…”

Section: Introductionmentioning

confidence: 99%

To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

Meyer

Seibt

Griffiths

2008

Phil. Trans. R. Soc. B

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A comparative study has been made of the photosynthetic physiological ecology and carbon isotope discrimination characteristics for modern-day bryophytes and closely related algal groups. Firstly, the extent of bryophyte distribution and diversification as compared with more advanced land plant groups is considered. Secondly, measurements of instantaneous carbon isotope discrimination (D), photosynthetic CO 2 assimilation and electron transport rates were compared during the drying cycles. The extent of surface diffusion limitation (when wetted), internal conductance and water use efficiency (WUE) at optimal tissue water content (TWC) were derived for liverworts and a hornwort from contrasting habitats and with differing degrees of thallus ventilation (as intra-thalline cavities and internal airspaces). We also explore how the operation of a biophysical carbon-concentrating mechanism (CCM) tempers isotope discrimination characteristics in two other hornworts, as well as the green algae Coleochaete orbicularis and Chlamydomonas reinhardtii. The magnitude of D was compared for each life form over a drying curve and used to derive the surface liquid-phase conductance (when wetted) and internal conductance (at optimal TWC). The magnitude of external and internal conductances, and WUE, was higher for ventilated, compared with non-ventilated, liverworts and hornworts, but the values were similar within each group, suggesting that both factors have been optimized for each life form. For the hornworts, leakiness of the CCM was highest for Megaceros vincentianus and C. orbicularis (approx. 30%) and, at 5%, lowest in C. reinhardtii grown under ambient CO 2 concentrations. Finally, evidence for the operation of a CCM in algae and hornworts is considered in terms of the probable role of the chloroplast pyrenoid, as the origins, structure and function of this enigmatic organelle are explored during the evolution of land plants.

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Section: Introductionmentioning

confidence: 99%

To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

Meyer

Seibt

Griffiths

2008

Phil. Trans. R. Soc. B

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“…The oldest convincing evidence for life on land consists of spores from primitive liverworts, which are close relatives of vascular plants (Wellman et al 2003). Molecular evidence for earlier phases of terrestrialization, most notably a putative date of 700 Ma for the first vascular land plants (Heckman et al 2001), is still controversial, not being supported by fossil or biomarker evidence.…”

Section: Diversification Of Life On Landmentioning

confidence: 99%

The origins of modern biodiversity on land

Benton

2010

Phil. Trans. R. Soc. B

140

107

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Comparative studies of large phylogenies of living and extinct groups have shown that most biodiversity arises from a small number of highly species-rich clades. To understand biodiversity, it is important to examine the history of these clades on geological time scales. This is part of a distinct 'phylogenetic expansion' view of macroevolution, and contrasts with the alternative, nonphylogenetic 'equilibrium' approach to the history of biodiversity. The latter viewpoint focuses on density-dependent models in which all life is described by a single global-scale model, and a case is made here that this approach may be less successful at representing the shape of the evolution of life than the phylogenetic expansion approach. The terrestrial fossil record is patchy, but is adequate for coarse-scale studies of groups such as vertebrates that possess fossilizable hard parts. New methods in phylogenetic analysis, morphometrics and the study of exceptional biotas allow new approaches. Models for diversity regulation through time range from the entirely biotic to the entirely physical, with many intermediates. Tetrapod diversity has risen as a result of the expansion of ecospace, rather than niche subdivision or regional-scale endemicity resulting from continental break-up. Tetrapod communities on land have been remarkably stable and have changed only when there was a revolution in floras (such as the demise of the Carboniferous coal forests, or the Cretaceous radiation of angiosperms) or following particularly severe mass extinction events, such as that at the end of the Permian.

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“…Considering the sequence of phylogenetic divergences within the lineage Chloroplastida, which also reflects ecological adaptations from marine to fresh water environments and colonization of terrestrial realm, the Charophytes and land plants are derived and later evolved lineages (Paleozoic; Graham and Gray, 2001;Wellman et al, 2003;O'Kelly, 2007;Rubinstein et al, 2010) than primary lineages of Prasinophytes and Chlorophytes (Turmel et al, 2002(Turmel et al, , 2008Raven et al, 2005;Baldauf, 2008). Prasinophytes are known to reproduce asexually and, although producing protective cysts, they lack superficial processes.…”

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confidence: 99%

Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China

Agić¹,

Moczydłowska²,

Yin

2015

J. Paleontol.

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Abstract.-Light microscope and scanning electron microscope observations on new material of unicellular microfossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the Mesoproterozoic Ruyang Group in China, provide insights into the microorganisms' biological affinity, life cycle and cellular complexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoic microfossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties of resistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgal cysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development of reproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst) stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates a reproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolically expensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these characters and from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stem group of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera and Shuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembrane system and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biota reveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryotic evolution and the development of complex life cycles with sexual reproduction by 1200 Ma.

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Fragments of the earliest land plants

Abstract: . We also thank A. Knoll and L. Yin for providing samples for bulk rock analyses, and J. Hayes for comments on an earlier version of this manuscript.

Cited by 527 publications

References 25 publications

To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

To concentrate or ventilate? Carbon acquisition, isotope discrimination and physiological ecology of early land plant life forms

The origins of modern biodiversity on land

Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China

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