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Wetland megabias: ecological and ecophysiological filtering dominates the fossil record of hot spring floras
Author(s) -
Channing Alan,
Edwards Dianne
Publication year - 2013
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/pala.12043
Subject(s) - hot spring , wetland , spring (device) , geology , vegetation (pathology) , mesophyte , ecology , flora (microbiology) , geothermal gradient , ecosystem , habitat , earth science , paleontology , biology , mechanical engineering , medicine , pathology , bacteria , engineering
Siliceous hot spring deposits form at E arth's surface above terrestrial hydrothermal systems, which create low‐sulphidation epithermal mineral deposits deeper in the crust. Eruption of hot spring waters and precipitation of opal‐ A create sinter apron complexes and areas of geothermally influenced wetland. These provide habitat for higher plants that may be preserved in situ , by encrustation of their surfaces and permineralization of tissues, creating T 0 plant assemblages. In this study, we review the fossil record of hot spring floras from subfossil examples forming in active hot spring areas, via fossil examples from the C enozoic, M esozoic and P alaeozoic to the oldest known hot spring flora, the L ower D evonian R hynie chert. We demonstrate that the well‐known megabias towards wetland plant preservation extends to hot spring floras. We highlight that the record of hot spring floras is dominated by plants preserved in situ by permineralization on geothermally influenced wetlands. Angiosperms (members of the C yperaceae and R estionaceae) dominate C enozoic floras. E quisetum and gleicheniaceous ferns colonized M esozoic ( J urassic) geothermal wetlands and sphenophytes and herbaceous lycophytes late P alaeozoic examples. Evidence of the partitioning of wetland hydrophytic and dryland mesophytic communities, a feature of active geothermal areas, is provided by well‐preserved and well‐exposed fossil sinter apron complexes, which record flooding of dryland environments by thermal waters and decline of local forest ecosystems. Such observations from the fossil record back‐up hypotheses based on active hot springs and vegetation that suggest removal of taphonomic filtering in hot spring environments is accompanied by an increase in ecological and ecophysiological filtering. To this end we also demonstrate that in the hot spring environment, the wetland bias extends beyond broad ecology. We show that ecosystems preserved from the C enozoic to the M esozoic provide clear evidence that the dominant plants preserved in situ by hot spring activity are also halophytic, tolerant of high p H and high concentrations of heavy metals. By extension, we hypothesize that this is also the case in P alaeozoic hot spring settings and extended to the early land plant flora of the R hynie chert.