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Newton RJ, Mackenzie BDE, Lamont BB, Gomez-Barreiro P, Cowling RM, He T. Fire-mediated germination syndromes in Leucadendron (Proteaceae) and their functional correlates. Oecologia 2021; 196:589-604. [PMID: 34159425 PMCID: PMC8241639 DOI: 10.1007/s00442-021-04947-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 05/15/2021] [Indexed: 11/29/2022]
Abstract
A mechanistic understanding of fire-driven seedling recruitment is essential for effective conservation management of fire-prone vegetation, such as South African fynbos, especially with rare and threatened taxa. The genus Leucadendron (Proteaceae) is an ideal candidate for comparative germination studies, comprising 85 species with a mixture of contrasting life-history traits (killed by fire vs able to resprout; serotinous vs geosporous) and seed morphologies (nutlets vs winged achenes). Individual and combined effects of heat and smoke on seed germination of 40 species were quantified in the laboratory, and Bayesian inference applied to distinguish biologically meaningful treatment effects from non-zero, but biologically trivial, effects. Three germination syndromes were identified based on whether germination was dependent on, enhanced by, or independent of direct fire cues (heat and smoke). Seed storage location was the most reliable predictor of germination syndromes, with soil-stored seeds c. 80% more likely to respond to direct fire cues (primarily smoke) than canopy-stored seeds. Notable exceptions were L. linifolium, with an absolute requirement for smoke to germinate (the third serotinous species so reported), and two other serotinous species with smoke-enhanced germination. Nutlet-bearing species, whether serotinous or geosporous, were c. 70% more likely to respond to fire cues than winged seeds, but there was no evidence for an effect of phylogeny or persistence strategy on germination. This comprehensive account of seed germination characteristics and identification of germination syndromes and their predictors, supports propagation, conservation and restoration initiatives in this iconic fynbos genus and other fire-prone shrubs with canopy or soil-stored seeds.
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Affiliation(s)
- Rosemary J Newton
- Conservation Science, Royal Botanic Gardens Kew, Wakehurst, Ardingly, West Sussex, RH17 6TN, UK.
| | - Berin D E Mackenzie
- Science Division, NSW Department of Planning, Industry and Environment, Locked Bag 5022, Parramatta, NSW, 2124, Australia.,Centre for Ecosystem Science, University of New South Wales, Kensington, NSW, 2052, Australia
| | - Byron B Lamont
- Ecology Section, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, WA, 6845, Australia
| | - Pablo Gomez-Barreiro
- Conservation Science, Royal Botanic Gardens Kew, Wakehurst, Ardingly, West Sussex, RH17 6TN, UK
| | - Richard M Cowling
- Department of Botany, Nelson Mandela Metropolitan University, PO Box 7700, Port Elizabeth, 6000, South Africa
| | - Tianhua He
- Ecology Section, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, WA, 6845, Australia
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Roddy AB, van Blerk JJ, Midgley JJ, West AG. Ramification has little impact on shoot hydraulic efficiency in the sexually dimorphic genus Leucadendron (Proteaceae). PeerJ 2019; 7:e6835. [PMID: 31179169 PMCID: PMC6545101 DOI: 10.7717/peerj.6835] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 03/22/2019] [Indexed: 11/20/2022] Open
Abstract
Despite the diversity of branching architectures in plants, the impact of this morphological variation on hydraulic efficiency has been poorly studied. Branch junctions are commonly thought to be points of high hydraulic resistance, but adjustments in leaf area or xylem conduit abundance or dimensions could compensate for the additional hydraulic resistance of nodal junctions at the level of the entire shoot. Here we used the sexually dimorphic genus Leucadendron (Proteaceae) to test whether variation in branch ramification impacts shoot hydraulic efficiency. We found that branch ramification was related to leaf traits via Corner’s rules such that more highly ramified shoots had smaller leaves, but that branch ramification had little consistent impact on shoot hydraulic efficiency, whether measured on a leaf area or stem cross-sectional area basis. These results suggest that the presumed increase in resistance associated with branching nodes can be compensated by other adjustments at the shoot level (e.g. leaf area adjustments, increased ramification to add additional branches in parallel rather than in series) that maintain hydraulic efficiency at the level of the entire shoot. Despite large morphological differences between males and females in the genus Leucadendron, which are due to differences in pollination and reproduction between the sexes, the physiological differences between males and females are minimal.
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Affiliation(s)
- Adam B Roddy
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA, United States of America
| | | | - Jeremy J Midgley
- Biological Sciences, University of Cape Town, Cape Town, South Africa
| | - Adam G West
- Biological Sciences, University of Cape Town, Cape Town, South Africa
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