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Ecology of ferns through time (IOPC-VI)
Review of Palaeobotany and Palynology 2427 (2002) vii^viii www.elsevier.com/locate/revpalbo
Editorial
Ecology of ferns through time (IOPC-VI) Margaret E. Collinson, Johanna H.A. van Konijnenburg-van Cittert This special issue contains all the papers presented in the symposium ‘The ecology of ferns through time’ held during the Sixth International Organization of Palaeobotany Conference (IOPCVI) from July 31st to August 3rd 2000 in Qinhuangdao, Hebei Province, China. When the organising committee of IOPC-VI invited us to convene a symposium on ferns, we realised that only a speci¢c theme could be addressed in the short time available. Fern biogeography (including Mesozoic and Cainozoic) had been the subject of a symposium at the International Botanical Congress in St. Louis 1999 and is now published (Moran, 2001). The Holltum Memorial Pteridophyte Symposium held at the Royal Botanic Gardens, Kew in 1995 (Camus et al., 1996) had covered many aspects of fern biology including some papers on fossils. Fern (and pteridophyte) evolution and phylogeny is the subject of much active current research (Pryer et al., 1995, 2001; Rothwell, 1999; papers in Camus et al., 1996). In contrast, we found little recent literature on fern palaeoecology and so we selected this theme in order to compliment the ongoing biogeographic and phylogenetic studies. The aims of the symposium were two-fold: ¢rstly, to bring together a state of the art compilation of the ecology of Palaeozoic, Mesozoic and Cainozoic ferns and place these in context of Recent fern ecology; and, secondly, to consider recent and novel approaches in fern palaeoecology. The scene is set by Chris Page whose compilation of Recent fern ecological strategies is based on a lifetime of observations both in the ¢eld in many areas of the world and from experimental work in cultivation. He recognises seven main
limitations and twelve important advantages of pteridophyte biology which constrain ecological opportunities and provide the potential to extrapolate from the modern ecology for interpretation of palaeoecology and palaeoenvironments. Niklas Wikstro«m and his co-authors use the family Schizaeaceae to show that a rigorous phylogenetic framework (in this case from molecular data on the plastid rbcL nucleotide sequence) can be used in combination with macrofossil evidence to infer the origins of ecological strategies in the Mesozoic and Cainozoic. Margaret Collinson considers the palaeoecology of Cainozoic ferns. She shows that there are no rachis fossils to support the interpretation that Cainozoic Lygodium (Schizaeaceae) was a climber. This means that the placement of Miocene fossils in crown group Lygodium by Wikstro«m et al. may be the best evidence available for climbing habit in Cainozoic ferns. Collinson shows that direct evidence for parent plant ecology is only well-documented for Cainozoic free-£oating water ferns and wetland and swamp ferns, whilst trees, ferns, climbers and epiphytes are very poorly understood. Some Cainozoic ferns grew in ¢re-prone settings like their living relatives. Mesozoic fern ecology is considered in four papers. These papers show the global ecological importance of ferns in the Mesozoic, most of these ferns can be assigned to modern fern families. Three of the papers draw on evidence from fern macrofossils, but Nathalie Nagalingum and co-authors discuss the fern spore diversity and abundance in Australia during the Cretaceous. A decline in the relative diversity and abundance of free-sporing plants during the Late Cretaceous was concurrent with a rise in the angiosperms,
0034-6667 / 02 / $ ^ see front matter H 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 4 - 6 6 6 7 ( 0 1 ) 0 0 1 2 6 - 9
PALBO 2427 7-6-02
viii
M.E. Collinson, J.H.A. van Konijnenburg-van Cittert / Review of Palaeobotany and Palynology 2427 (2002) vii^viii
while the relative contribution of the gymnosperms remained more or less unchanged. The Schizaeaceae mostly account for the decline in fern diversity, while the decline in fern abundance can be mainly attributed to a marked decline in the Osmundaceae. Two of the three papers on Mesozoic fern ecology based on macrofossils are dealing with fossil ferns found in China. Shenghui Deng discusses the ecology of Early Cretaceous ferns in Northeast China (Northern Floristic Province in China), while Yongdong Wang focuses on ferns from the early Jurassic in Western Hubei (Southern Floristic Province). In these papers, the di¡erences between the fern communities and their ecologies are clear, both in time (Early Jurassic versus Early Cretaceous) and in £oral provinces (Southern versus Northern). Han van Konijnenburg-van Cittert deals with the ecology of some Late Triassic to Early Cretaceous ferns in Eurasia. Many Mesozoic ferns are shown to be small to large herbaceous plants growing in moist settings even partaking in peat-formation (resulting in coal formation). However, others, especially those in the Matoniaceae and Gleicheniaceae, grew in ¢re-prone settings like some of their Cainozoic and living relatives. Finally, Bill DiMichele and Tom Phillips consider the palaeoecology of Palaeozoic ferns. They show that ferns and fern-like plants have been important elements of terrestrial vegetation since the Late Devonian. Furthermore, by the early Carboniferous, all major body plans and habits of ferns had appeared and they subsequently appeared and disappeared in various lineages. The series of papers draws attention to many interesting avenues for future research and here
we select just a few highlights: (a) assessing the interplay between biology, ecology and phylogeny in the context of rigorous phylogenetic frameworks ; (b) evaluating the role of environmental factors (e.g. ¢re, climate change) in constraining fern ecological strategies and fern evolution; (c) seeking direct evidence of Mesozoic and Cainozoic epiphytic ferns (and indeed all epiphytic £ora) e.g. by studying the stumps, trunks, logs and isolated bark of any fossil trees; (d) reassessing potentially diagnostic spores and further exploiting the dispersed spore record within a rigorous phylogenetic framework ; (e) seeking more direct evidence of ancient fern ecology through documentation of in situ plants and facies context of fossil ferns, and studies emphasising whole plants, including the root system, rhizome and rachis (e.g. twining, indeterminate). We hope that this special issue will stimulate these and many other future research e¡orts on fossil ferns.
References Camus, J.M., Gibby, M., Johns, R.J. (Eds.), 1996. Pteridology in Perspective. Royal Botanic Gardens, Kew, 700 pp. Moran, R.C. (Ed.), 2001. Papers from the Pteridophyte Biogeography Symposium, International Botanical Congress. Brittonia 53, 171^375. Pryer, K.M., Smith, A.R., Skog, J.E., 1995. Phylogenetic relationships of extant ferns based on evidence from morphology and rbcL sequences. Am. Fern J. 85, 205^282. Pryer, K.M., Schneider, H., Smith, A.R., Cran¢ll, R., Wolf, P.G., Hunt, J.S., Sipes, S.D., 2001. Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409, 618^622. Rothwell, G.W., 1999. Fossils and ferns in the resolution of land plant phylogeny. Bot. Rev. 65, 188^218.
PALBO 2427 7-6-02
Editorial
Ecology of ferns through time (IOPC-VI) Margaret E. Collinson, Johanna H.A. van Konijnenburg-van Cittert This special issue contains all the papers presented in the symposium ‘The ecology of ferns through time’ held during the Sixth International Organization of Palaeobotany Conference (IOPCVI) from July 31st to August 3rd 2000 in Qinhuangdao, Hebei Province, China. When the organising committee of IOPC-VI invited us to convene a symposium on ferns, we realised that only a speci¢c theme could be addressed in the short time available. Fern biogeography (including Mesozoic and Cainozoic) had been the subject of a symposium at the International Botanical Congress in St. Louis 1999 and is now published (Moran, 2001). The Holltum Memorial Pteridophyte Symposium held at the Royal Botanic Gardens, Kew in 1995 (Camus et al., 1996) had covered many aspects of fern biology including some papers on fossils. Fern (and pteridophyte) evolution and phylogeny is the subject of much active current research (Pryer et al., 1995, 2001; Rothwell, 1999; papers in Camus et al., 1996). In contrast, we found little recent literature on fern palaeoecology and so we selected this theme in order to compliment the ongoing biogeographic and phylogenetic studies. The aims of the symposium were two-fold: ¢rstly, to bring together a state of the art compilation of the ecology of Palaeozoic, Mesozoic and Cainozoic ferns and place these in context of Recent fern ecology; and, secondly, to consider recent and novel approaches in fern palaeoecology. The scene is set by Chris Page whose compilation of Recent fern ecological strategies is based on a lifetime of observations both in the ¢eld in many areas of the world and from experimental work in cultivation. He recognises seven main
limitations and twelve important advantages of pteridophyte biology which constrain ecological opportunities and provide the potential to extrapolate from the modern ecology for interpretation of palaeoecology and palaeoenvironments. Niklas Wikstro«m and his co-authors use the family Schizaeaceae to show that a rigorous phylogenetic framework (in this case from molecular data on the plastid rbcL nucleotide sequence) can be used in combination with macrofossil evidence to infer the origins of ecological strategies in the Mesozoic and Cainozoic. Margaret Collinson considers the palaeoecology of Cainozoic ferns. She shows that there are no rachis fossils to support the interpretation that Cainozoic Lygodium (Schizaeaceae) was a climber. This means that the placement of Miocene fossils in crown group Lygodium by Wikstro«m et al. may be the best evidence available for climbing habit in Cainozoic ferns. Collinson shows that direct evidence for parent plant ecology is only well-documented for Cainozoic free-£oating water ferns and wetland and swamp ferns, whilst trees, ferns, climbers and epiphytes are very poorly understood. Some Cainozoic ferns grew in ¢re-prone settings like their living relatives. Mesozoic fern ecology is considered in four papers. These papers show the global ecological importance of ferns in the Mesozoic, most of these ferns can be assigned to modern fern families. Three of the papers draw on evidence from fern macrofossils, but Nathalie Nagalingum and co-authors discuss the fern spore diversity and abundance in Australia during the Cretaceous. A decline in the relative diversity and abundance of free-sporing plants during the Late Cretaceous was concurrent with a rise in the angiosperms,
0034-6667 / 02 / $ ^ see front matter H 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 4 - 6 6 6 7 ( 0 1 ) 0 0 1 2 6 - 9
PALBO 2427 7-6-02
viii
M.E. Collinson, J.H.A. van Konijnenburg-van Cittert / Review of Palaeobotany and Palynology 2427 (2002) vii^viii
while the relative contribution of the gymnosperms remained more or less unchanged. The Schizaeaceae mostly account for the decline in fern diversity, while the decline in fern abundance can be mainly attributed to a marked decline in the Osmundaceae. Two of the three papers on Mesozoic fern ecology based on macrofossils are dealing with fossil ferns found in China. Shenghui Deng discusses the ecology of Early Cretaceous ferns in Northeast China (Northern Floristic Province in China), while Yongdong Wang focuses on ferns from the early Jurassic in Western Hubei (Southern Floristic Province). In these papers, the di¡erences between the fern communities and their ecologies are clear, both in time (Early Jurassic versus Early Cretaceous) and in £oral provinces (Southern versus Northern). Han van Konijnenburg-van Cittert deals with the ecology of some Late Triassic to Early Cretaceous ferns in Eurasia. Many Mesozoic ferns are shown to be small to large herbaceous plants growing in moist settings even partaking in peat-formation (resulting in coal formation). However, others, especially those in the Matoniaceae and Gleicheniaceae, grew in ¢re-prone settings like some of their Cainozoic and living relatives. Finally, Bill DiMichele and Tom Phillips consider the palaeoecology of Palaeozoic ferns. They show that ferns and fern-like plants have been important elements of terrestrial vegetation since the Late Devonian. Furthermore, by the early Carboniferous, all major body plans and habits of ferns had appeared and they subsequently appeared and disappeared in various lineages. The series of papers draws attention to many interesting avenues for future research and here
we select just a few highlights: (a) assessing the interplay between biology, ecology and phylogeny in the context of rigorous phylogenetic frameworks ; (b) evaluating the role of environmental factors (e.g. ¢re, climate change) in constraining fern ecological strategies and fern evolution; (c) seeking direct evidence of Mesozoic and Cainozoic epiphytic ferns (and indeed all epiphytic £ora) e.g. by studying the stumps, trunks, logs and isolated bark of any fossil trees; (d) reassessing potentially diagnostic spores and further exploiting the dispersed spore record within a rigorous phylogenetic framework ; (e) seeking more direct evidence of ancient fern ecology through documentation of in situ plants and facies context of fossil ferns, and studies emphasising whole plants, including the root system, rhizome and rachis (e.g. twining, indeterminate). We hope that this special issue will stimulate these and many other future research e¡orts on fossil ferns.
References Camus, J.M., Gibby, M., Johns, R.J. (Eds.), 1996. Pteridology in Perspective. Royal Botanic Gardens, Kew, 700 pp. Moran, R.C. (Ed.), 2001. Papers from the Pteridophyte Biogeography Symposium, International Botanical Congress. Brittonia 53, 171^375. Pryer, K.M., Smith, A.R., Skog, J.E., 1995. Phylogenetic relationships of extant ferns based on evidence from morphology and rbcL sequences. Am. Fern J. 85, 205^282. Pryer, K.M., Schneider, H., Smith, A.R., Cran¢ll, R., Wolf, P.G., Hunt, J.S., Sipes, S.D., 2001. Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409, 618^622. Rothwell, G.W., 1999. Fossils and ferns in the resolution of land plant phylogeny. Bot. Rev. 65, 188^218.
PALBO 2427 7-6-02