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Yoneoka K, Fujiwara T, Kataoka T, Hori K, Ebihara A, Murakami N. Morphological and functional evolution of gametophytes in epilithic Hymenasplenium murakami-hatanakae (Aspleniaceae): The fifth family capable of producing the independent gametophytes. JOURNAL OF PLANT RESEARCH 2024; 137:815-828. [PMID: 38918283 PMCID: PMC11393290 DOI: 10.1007/s10265-024-01553-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Accepted: 06/02/2024] [Indexed: 06/27/2024]
Abstract
The fern independent gametophytes that can maintain populations by vegetative reproduction without conspecific sporophytes have been considered an unusual phenomenon found in some epiphytic or epilithic species of Hymenophyllaceae, Pteridaceae, Lomariopsidaceae, and Polypodiaceae. By chance, the discovery of mysterious strap-like gametophytes on Izu-Oshima Island, Japan, has led to the hypothesis that Hymenasplenium murakami-hatanakae, a fern species belonging to Aspleniaceae, can also form independent gametophytes. Our investigation revealed gametophyte populations of H. murakami-hatanakae on three islands in the Izu Islands. Based on chloroplast DNA analysis of the gametophyte and sporophyte populations, the gametophytes were found to be maintained by vegetative reproduction without a new supply of spores from sporophytes. A comparison of the surrounding vegetation at the collection sites showed that environmental factors such as light and humidity may influence the maintenance of gametophyte populations. These results clearly show that H. murakami-hatanakae is one of the ferns capable of forming independent gametophytes. This is the first report of independent gametophytes from the suborder Aspleniineae (eupolypod II). The discovery of the independent gametophyte within a phylogenetic lineage previously thought not to form independent gametophytes will provide important insights into the morphological and functional evolution of gametophytes in ferns.
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Affiliation(s)
- Katsuhiro Yoneoka
- Makino Herbarium, Tokyo Metropolitan University, 1-1 Minami-Osawa 1-1, Hachioji, Tokyo, 192-0397, Japan.
| | - Tao Fujiwara
- The Mt. Fuji Institute for Nature and Biology, Showa University, 4562 Kamiyoshida, Fujiyoshida, Yamanashi, 403-0005, Japan
| | - Toshifumi Kataoka
- Makino Herbarium, Tokyo Metropolitan University, 1-1 Minami-Osawa 1-1, Hachioji, Tokyo, 192-0397, Japan
| | - Kiyotaka Hori
- Makino Botanical Garden, 4200-6 Godaisan, Kouchi-City, Kouchi, 780-0870, Japan
| | - Atsushi Ebihara
- Department of Botany, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki, 305-0005, Japan
| | - Noriaki Murakami
- Makino Herbarium, Tokyo Metropolitan University, 1-1 Minami-Osawa 1-1, Hachioji, Tokyo, 192-0397, Japan
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Edwards‐Calma K, Jiménez L, Zenil‐Ferguson R, Heyduk K, Thomas MK, Tribble CM. Conservation applications of niche modeling: Native and naturalized ferns may compete for limited Hawaiian dryland habitat. APPLICATIONS IN PLANT SCIENCES 2024; 12:e11598. [PMID: 38912653 PMCID: PMC11192160 DOI: 10.1002/aps3.11598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 04/04/2024] [Accepted: 04/22/2024] [Indexed: 06/25/2024]
Abstract
Premise Competition from naturalized species and habitat loss are common threats to native biodiversity and may act synergistically to increase competition for decreasing habitat availability. We use Hawaiian dryland ferns as a model for the interactions between land-use change and competition from naturalized species in determining habitat availability. Methods We used fine-resolution climatic variables and carefully curated occurrence data from herbaria and community science repositories to estimate the distributions of Hawaiian dryland ferns. We quantified the degree to which naturalized ferns tend to occupy areas suitable for native species and mapped the remaining available habitat given land-use change. Results Of all native species, Doryopteris angelica had the lowest percentage of occurrences of naturalized species in its suitable area while D. decora had the highest. However, all Doryopteris spp. had a higher percentage overlap, while Pellaea ternifolia had a lower percentage overlap, than expected by chance. Doryopteris decora and D. decipiens had the lowest proportions (<20%) of suitable area covering native habitat. Discussion Areas characterized by shared environmental preferences of native and naturalized ferns may decrease due to human development and fallowed agricultural lands. Our study demonstrates the value of place-based application of a recently developed correlative ecological niche modeling approach for conservation risk assessment in a rapidly changing and urbanized island ecosystem.
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Affiliation(s)
| | - Laura Jiménez
- School of Life SciencesUniversity of Hawaiʻi at MānoaHonoluluHawaiʻi 96822USA
- Centro de Modelamiento MatemáticoUniversidad de ChileSantiagoChile
| | | | - Karolina Heyduk
- School of Life SciencesUniversity of Hawaiʻi at MānoaHonoluluHawaiʻi 96822USA
- Department of Ecology and Evolutionary BiologyUniversity of ConnecticutStorrs06269ConnecticutUSA
| | - Miles K. Thomas
- Herbarium Pacificum, Bernice Pauahi Bishop MuseumHonoluluHawaiʻi 96813USA
| | - Carrie M. Tribble
- School of Life SciencesUniversity of Hawaiʻi at MānoaHonoluluHawaiʻi 96822USA
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Pittermann J, Baer A, Campany C, Jansen S, Holmlund H, Schuettpelz E, Mehltreter K, Watkins JE. A reduced role for water transport during the Cenozoic evolution of epiphytic Eupolypod ferns. THE NEW PHYTOLOGIST 2023; 237:1745-1758. [PMID: 36484140 DOI: 10.1111/nph.18667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 11/15/2022] [Indexed: 06/17/2023]
Abstract
The Cretaceous-Cenozoic expansion of tropical forests created canopy space that was subsequently occupied by diverse epiphytic communities including Eupolypod ferns. Eupolypods proliferated in this more stressful niche, where lower competition enabled the adaptive radiation of thousands of species. Here, we examine whether xylem traits helped shape the Cenozoic radiation of Eupolypod ferns. We characterized the petiole xylem anatomy of 39 species belonging to the Eupolypod I and Eupolypod II clades occupying the epiphytic, hemiepiphytic, and terrestrial niche, and we assessed vulnerability to embolism in a subset of species. The transition to the canopy was associated with reduced xylem content and smaller tracheid diameters, but no differences were found in species vulnerability to embolism and pit membrane thickness. Phylogenetic analyses support selection for traits associated with reduced water transport in Eupolypod 1 species. We posit that in Eupolypod epiphytes, selection favored water retention via thicker leaves and lower stomatal density over higher rates of water transport. Consequently, lower leaf water loss was coupled with smaller quantities of xylem and narrower tracheid diameters. Traits associated with water conservation were evident in terrestrial Eupolypod 1 ferns and may have predisposed this clade toward radiation in the canopy.
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Affiliation(s)
- Jarmila Pittermann
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95060, USA
| | - Alex Baer
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95060, USA
| | - Courtney Campany
- Department of Biology, Shepherd University, Shepherdstown, WV, 25443, USA
| | - Steven Jansen
- Institute for Systematic Botany and Ecology, University of Ulm, Ulm, 89081, Germany
| | - Helen Holmlund
- Natural Science Division, Pepperdine University, Malibu, CA, 90263, USA
| | - Eric Schuettpelz
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20560, USA
| | - Klaus Mehltreter
- Red de Ecologia Funcíonal, Instituto de Ecología A.C, Xalapa, Veracruz, 91073, Mexico
| | - James E Watkins
- Department of Biology, Colgate University, Hamilton, NY, 13346, USA
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Mellado-Mansilla D, Testo W, Sundue MA, Zotz G, Kreft H, Coiro M, Kessler M. The relationship between chlorophyllous spores and mycorrhizal associations in ferns: evidence from an evolutionary approach. AMERICAN JOURNAL OF BOTANY 2022; 109:2068-2081. [PMID: 36310350 DOI: 10.1002/ajb2.16094] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/17/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
PREMISE Approximately 14% of all fern species have physiologically active chlorophyllous spores that are much more short-lived than the more common and dormant achlorophyllous spores. Most chlorophyllous-spored species (70%) are epiphytes and account for almost 37% of all epiphytic ferns. Chlorophyllous-spored ferns are also overrepresented among fern species in habitats with waterlogged soils, of which nearly 60% have chlorophyllous spores. Ferns in these disparate habitat types also have a low incidence of mycorrhizal associations. We therefore hypothesized that autotrophic chlorophyllous spores represent an adaptation of ferns to habitats with scarce mycorrhizal associations. METHODS We evaluated the coevolution of chlorophyllous spores and mycorrhizal associations in ferns and their relation to habitat type using phylogenetic comparative methods. RESULTS Although we did not find support for the coevolution of spore type and mycorrhizal associations, we did find that chlorophyllous spores and the absence of mycorrhizal associations have coevolved with epiphytic and waterlogged habitats. Transition rates to epiphytic and waterlogged habitats were significantly higher in species with chlorophyllous spores compared to achlorophyllous lineages. CONCLUSIONS Spore type and mycorrhizal associations appear to play important roles in the radiation of ferns into different habitat types. Future work should focus on clarifying the functional significance of these associations.
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Affiliation(s)
- Daniela Mellado-Mansilla
- Department of Biodiversity, Macroecology and Biogeography, Faculty of Forest Sciences and Forest Ecology, University of Göttingen, Göttingen, Germany
- Institute for Biology and Environmental Sciences, AG Functional Ecology, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Weston Testo
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
- Gothenburg Global Biodiversity Centre, Göteborg, Sweden
| | - Michael A Sundue
- The Pringle Herbarium, Department of Plant Biology, University of Vermont, Burlington, VT, USA
| | - Gerhard Zotz
- Institute for Biology and Environmental Sciences, AG Functional Ecology, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
- Smithsonian Tropical Research Institute, Panama
| | - Holger Kreft
- Department of Biodiversity, Macroecology and Biogeography, Faculty of Forest Sciences and Forest Ecology, University of Göttingen, Göttingen, Germany
- Centre of Biodiversity and Sustainable Land Use (CBL), University of Göttingen, Göttingen, Germany
| | - Mario Coiro
- Department of Paleontology, University of Vienna, Vienna, Austria
- Ronin Institute for Independent Scholarship, Montclair, NJ, USA
| | - Michael Kessler
- Department of Systematic and Evolutionary Botany, University of Zürich, Zürich, Switzerland
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Nitta JH, Chambers SM. Identifying cryptic fern gametophytes using DNA barcoding: A review. APPLICATIONS IN PLANT SCIENCES 2022; 10:e11465. [PMID: 35495195 PMCID: PMC9039790 DOI: 10.1002/aps3.11465] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 12/09/2021] [Accepted: 12/11/2021] [Indexed: 05/14/2023]
Abstract
Ferns and lycophytes are unique among land plants in having sporophyte (diploid) and gametophyte (haploid) generations that can grow independently of each other. While most studies of fern ecology focus on the more visible sporophytic stage, the gametophyte is critically important, as it is the sexual phase of the life cycle. Yet, fern gametophytes have long been neglected in field studies due to their small size and cryptic morphology. DNA barcoding is a powerful method that can be used to identify field-collected gametophytes to species and allow for detailed study of their ecology. Here, we review the state of DNA barcoding as applied to fern gametophytes. First, we trace the history of DNA barcoding and how it has come to be applied to fern gametophytes. Next, we summarize case studies that show how DNA barcoding has been used to better understand fern species distributions, gametophyte ecology, and community ecology. Finally, we propose avenues for future research using this powerful tool, including next-generation DNA sequencing for in-field identification of cryptic gametophytes.
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Affiliation(s)
- Joel H. Nitta
- Department of Biological Sciences, Graduate School of ScienceThe University of Tokyo2‐11‐16 Yayoi, Bunkyo‐kuTokyo113‐0032Japan
| | - Sally M. Chambers
- Marie Selby Botanical GardensBotany DepartmentSarasotaFlorida34236USA
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Krieg CP, Chambers SM. The ecology and physiology of fern gametophytes: A methodological synthesis. APPLICATIONS IN PLANT SCIENCES 2022; 10:e11464. [PMID: 35495196 PMCID: PMC9039797 DOI: 10.1002/aps3.11464] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 12/21/2021] [Accepted: 01/10/2022] [Indexed: 05/14/2023]
Abstract
All green plants alternate between the gametophyte and sporophyte life stages, but only seed-free vascular plants (ferns and lycophytes) have independent, free-living gametophytes. Fern and lycophyte gametophytes are significantly reduced in size and morphological complexity relative to their sporophytic counterparts and have often been overlooked in ecological and physiological studies. Understanding the ecological and physiological factors that directly impact this life stage is of critical importance because the ultimate existence of a sporophyte is dependent upon successful fertilization in the gametophyte generation. Furthermore, previous research has shown that the dual nature of the life cycle and the high dispersibility of spores can result in different geographic patterns between gametophytes and their respective sporophytes. This variation in distribution patterns likely exacerbates the separation of selective pressures acting on gametophyte and sporophyte generations, and can uniquely impact a species' ecology and physiology. Here, we provide a review of historical and contemporary methodologies used to examine ecological and physiological aspects of fern gametophytes, as well as those that allow for comparisons between the two generations. We conclude by suggesting methodological approaches to answer currently outstanding questions. We hope that the information covered herein will serve as a guide to current researchers and stimulate future discoveries in fern gametophyte ecology and physiology.
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Affiliation(s)
| | - Sally M. Chambers
- Department of BotanyMarie Selby Botanical GardensSarasotaFlorida34236USA
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Nitta JH, Watkins JE, Holbrook NM, Wang TW, Davis CC. Ecophysiological differentiation between life stages in filmy ferns (Hymenophyllaceae). JOURNAL OF PLANT RESEARCH 2021; 134:971-988. [PMID: 34117960 DOI: 10.1007/s10265-021-01318-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/03/2021] [Indexed: 06/12/2023]
Abstract
Desiccation tolerance was a key trait that allowed plants to colonize land. However, little is known about the transition from desiccation tolerant non-vascular plants to desiccation sensitive vascular ones. Filmy ferns (Hymenophyllaceae) represent a useful system to investigate how water-stress strategies differ between non-vascular and vascular stages within a single organism because they have vascularized sporophytes and nonvascular gametophytes that are each capable of varying degrees of desiccation tolerance. To explore this, we surveyed sporophytes and gametophytes of 19 species (22 taxa including varieties) of filmy ferns on Moorea (French Polynesia) and used chlorophyll fluorescence to measure desiccation tolerance and light responses. We conducted phylogenetically informed analyses to identify differences in physiology between life stages and growth habits. Gametophytes had similar or less desiccation tolerance (ability to recover from 2 days desiccation at - 86 MPa) and lower photosynthetic optima (maximum electron transport rate of photosystem II and light level at 95% of that rate) than sporophytes. Epiphytes were more tolerant of desiccation than terrestrial species in both life stages. Despite their lack of greater physiological tolerances, gametophytes of several species occurred over a wider elevational range than conspecific sporophytes. Our results demonstrate that filmy fern gametophytes and sporophytes differ in their physiology and niche requirements, and point to the importance of microhabitat in shaping the evolution of water-use strategies in vascular plants.
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Affiliation(s)
- Joel H Nitta
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
- Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA.
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan.
| | - James E Watkins
- Department of Biology, Colgate University, 13 Oak Drive, Hamilton, NY, 13346, USA
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Tristan W Wang
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA
- Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Charles C Davis
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA
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Campany CE, Pittermann J, Baer A, Holmlund H, Schuettpelz E, Mehltreter K, Watkins JE. Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms. PLANT, CELL & ENVIRONMENT 2021; 44:1741-1755. [PMID: 33665827 DOI: 10.1111/pce.14042] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 06/12/2023]
Abstract
Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.
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Affiliation(s)
- Courtney E Campany
- Department of Biology, Shepherd University, Shepherdstown, West Virginia, USA
- Department of Biology, Colgate University, Hamilton, New York, USA
| | - Jarmila Pittermann
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, USA
| | - Alex Baer
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, USA
| | - Helen Holmlund
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Eric Schuettpelz
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA
| | - Klaus Mehltreter
- Red de Ecología Funcional, Instituto de Ecología A.C., Xalapa, Mexico
- Institute for Systematic Botany and Ecology, University of Ulm, Ulm, Germany
| | - James E Watkins
- Department of Biology, Colgate University, Hamilton, New York, USA
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Aros-Mualin D, Noben S, Karger DN, Carvajal-Hernández CI, Salazar L, Hernández-Rojas A, Kluge J, Sundue MA, Lehnert M, Quandt D, Kessler M. Functional Diversity in Ferns Is Driven by Species Richness Rather Than by Environmental Constraints. FRONTIERS IN PLANT SCIENCE 2021; 11:615723. [PMID: 33505416 PMCID: PMC7829179 DOI: 10.3389/fpls.2020.615723] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Functional traits determine how species interact with their abiotic and biotic environment. In turn, functional diversity describes how assemblages of species as a whole are adapted to their environment, which also determines how they might react to changing conditions. To fully understand functional diversity, it is fundamental to (a) disentangle the influences of environmental filtering and species richness from each other, (b) assess if the trait space saturates at high levels of species richness, and (c) understand how changes in species numbers affect the relative importance of the trait niche expansion and packing. In the present study, we determined functional diversity of fern assemblages by describing morphological traits related to resource acquisition along four tropical elevational transects with different environmental conditions and species richness. We used several functional diversity indices and their standardized effect size to consider different aspects of functional diversity. We contrasted these aspects of functional diversity with climate data and species richness using linear models and linear mixed models. Our results show that functional morphological trait diversity was primarily driven by species richness and only marginally by environmental conditions. Moreover, increasing species richness contributed progressively to packing of the morphological niche space, while at the same time decreasing morphological expansion until a saturation point was reached. Overall, our findings suggest that the density of co-occurring species is the fundamental driving force of morphological niche structure, and environmental conditions have only an indirect influence on fern resource acquisition strategies.
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Affiliation(s)
- Daniela Aros-Mualin
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich, Switzerland
| | - Sarah Noben
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich, Switzerland
| | - Dirk N. Karger
- Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
| | | | - Laura Salazar
- Centro de Investigación de la Biodiversidad y Cambio Climático (BioCamb) e Ingeniería en Biodiversidad y Recursos Genéticos, Facultad de Ciencias de Medio Ambiente, Universidad Tecnológica Indoamérica, Quito, Ecuador
| | | | - Jürgen Kluge
- Department of Geography, Philipps University Marburg, Marburg, Germany
| | - Michael A. Sundue
- The Pringle Herbarium, Department of Plant Biology, University of Vermont, Burlington, VT, United States
| | - Marcus Lehnert
- Department of Geobotany and Botanical Garden, Herbarium, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Dietmar Quandt
- Nees-Institute for Biodiversity of Plants, University of Bonn, Bonn, Germany
| | - Michael Kessler
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich, Switzerland
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10
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Nitta JH, Watkins JE, Davis CC. Life in the canopy: community trait assessments reveal substantial functional diversity among fern epiphytes. THE NEW PHYTOLOGIST 2020; 227:1885-1899. [PMID: 32285944 DOI: 10.1111/nph.16607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 04/02/2020] [Indexed: 06/11/2023]
Abstract
The expansion of angiosperm-dominated forests in the Cretaceous and early Cenozoic had a profound effect on terrestrial biota by creating novel ecological niches. The majority of modern fern lineages are hypothesized to have arisen in response to this expansion, particularly fern epiphytes that radiated into the canopy. Recent evidence, however, suggests that epiphytism does not correlate with increased diversification rates in ferns, calling into question the role of the canopy habitat in fern evolution. To understand the role of the canopy in structuring fern community diversity, we investigated functional traits of fern sporophytes and gametophytes across a broad phylogenetic sampling on the island of Moorea, French Polynesia, including > 120 species and representatives of multiple epiphytic radiations. While epiphytes showed convergence in small size and a higher frequency of noncordate gametophytes, they showed greater functional diversity at the community level relative to terrestrial ferns. These results suggest previously overlooked functional diversity among fern epiphytes, and raise the hypothesis that while the angiosperm canopy acted as a complex filter that restricted plant size, it also facilitated diversification into finely partitioned niches. Characterizing these niche axes and adaptations of epiphytic ferns occupying them should be a priority for future pteridological research.
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Affiliation(s)
- Joel H Nitta
- Department of Organismic and Evolutionary Biology and Harvard University Herbaria, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
| | - James E Watkins
- Department of Biology, Colgate University, 13 Oak Drive, Hamilton, NY, 13346, USA
| | - Charles C Davis
- Department of Organismic and Evolutionary Biology and Harvard University Herbaria, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
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