Habitat specificity

Habitat specificities were often reported without any quantitative measurements (Holttum, 1938; Page 1979a, 1979b; Cortez, 2001), with the exception of recent studies on epiphytes (Moran et al., 2003; Mehltreter et al., 2005) and terrestrial species (Poulsen et al., 2006). The role of mycorrhizae in ferns for mediating habitat specificity has been poorly studied. Despite the obligatory mycorrhizae of some fern groups (e.g., Lycopodium, Ophioglossum, Psilotum, Tmesipteris), only facultative mycorrhizae were reported for the sporophytes in a study of Hawaiian ferns (Gemma et al., 1992).

Terrestrial species

Poulsen et al. (2006) studied the floristic diversity of a plot of 1 ha of lowland Amazonian rain forest in Ecuador with an acidic mean soil pH of 3.33. The distribution and abundance of 29 fern species were correlated with soil calcium and sand content, and to a lesser degree with aluminum content. More studies of this type are needed on ferns at this geographical scale to allow for generalizations; the results of Poulsen et al. (2006) may not be applicable to sites with higher soil pH values, and where the calcium and aluminum contents could be less important to fern distribution. Edaphic niches of Polybotrya spp. in Northwestern Amazonia were best described by differences in soil texture, and cation content (Tuomisto, 2006).

Figure 8.2 (a, b) Vegetative reproduction and (c, d) leaf desiccation in some Mexican ferns. (a) Apical leaf buds of Asplenium alatum with young plant rooted in the ground. (b) Asplenium sessilifolium with completely developed plantlet at the leaf tip. (c) Desiccating leaf of Polypodium furfuraceum, bending pinnae inwards, exposing the lower scaly surface. (d) Desiccating leaf of Asplenium praemorsum folding pinnae accordion-like starting at the leaf tip.

Figure 8.2 (a, b) Vegetative reproduction and (c, d) leaf desiccation in some Mexican ferns. (a) Apical leaf buds of Asplenium alatum with young plant rooted in the ground. (b) Asplenium sessilifolium with completely developed plantlet at the leaf tip. (c) Desiccating leaf of Polypodium furfuraceum, bending pinnae inwards, exposing the lower scaly surface. (d) Desiccating leaf of Asplenium praemorsum folding pinnae accordion-like starting at the leaf tip.

Mangrove species

The three species of mangrove ferns in the genus Acrostichum are exceptionally tolerant to salt stress. They root in the soil and are often flooded, even though never completely submersed. The largest species, A. danaeifolium, is restricted to the Neotropics and is the least salt tolerant (Lloyd and Buckley, 1986; Mehltreter and Palacios-Rios, 2003). The smallest species, A. speciosum, from the Paleotropics seems to be the only obligately halophytic fern species (Kramer et al., 1995). The pantropically distributed A. aureum is ecologically intermediate

Table 8.3 Number of species with substrate specificity of four genera of Mexican rock ferns

Genus Limestone Gypsum Igneous rocks No preference

Argyrochosma 5 0 2 5

Cheilanthes 12 2 11 35

Notholaena 4 2 5 13

Pellaea 2 14 7

Data from Mickel and Smith (2004).

between the other two species. Other species that may grow in the coastal zones adjacent to the mangroves are Stenochlaena palustris in southeast Asia and Ctenitis maritima on La Réunion Island (Mehltreter, personal observation).

Lithophytes

Lithophytes (petrophytes) are plants that grow primarily on rocks and boulders. Species that grow on rocks along rivers and stream banks often reproduce vegetatively by apical leaf buds, e.g., Asplenium (Figure 8.2a, 8.2b). Rock ferns are often good indicators for the underlying chemistry of the substrate. For temperate zones, there are dozens of examples of ferns that only grow on igneous rocks (e.g., granite), metamorphic rocks (e.g., serpentine), or sedimentary rocks (e.g., sandstone, gypsum, and limestone). In some genera such as Asplenium these substrate specificities change in newly formed hybrids compared to their parental taxa, e.g. A. adulterinum is restricted to serpentine rocks, although it is the allopolyploid hybrid between calciphilous A. viride and A. trichomanes which grows on silicate rocks (Kramer et al., 1995). Although in tropical humid zones limestone is scarcely found because it erodes quickly, some species are typically restricted to this habitat, especially those in the genera Argyrochosma and Cheilan-thes (Table 8.3). Mickel and Smith (2004) report rock substrate specificities for 50 out of 110 species of Argyrochosma, Cheilanthes, Notholaena, and Pellaea with more or less equal proportions occurring on limestone (23 species) or igneous rocks (22 species). Consequently, these species are restricted to mountain ranges with these substrates and may be less common and more frequently endangered than more widespread, substrate-generalist species. Over the last twenty years, some ferns have been reported to hyper-accumulate heavy metals, especially arsenic, cadmium, copper, and zinc (Table 8.4) and, thus, may be good indicators of soil type. Recently, some fern species, especially Athyrium yokoscense (Nishizono et al., 1987) and Pteris vittata (Ma et al., 2001), have been used as phytoremediators to manage heavy-metal contaminated soils.

Table 8.4 Heavy metal hyper-accumulating fern species

Species

Life form

Accumulated heavy metals

Pityrogramma calomelanos5 Azolla caroliniana6 Azolla filiculoides2 Marattia spp.3 Pteris vittata4 Athyrium yokoscense1

terrestrial aquatic aquatic terrestrial terrestrial and lithophytic terrestrial

1Nishizono et al., 1987;

3Kramer et al., 1995;

5Francesconi et al., 2002;

6Bennicelli et al., 2004.

Epiphytes

Ferns are the third most species-rich group of epiphytes after orchids and bromeliads in the New World. The three fern families with the greatest number of epiphytic species are Polypodiaceae, Hymenophyllaceae, and Aspleni-aceae, all with more than 50% of the family occurring as epiphytes. Vittarioid ferns (Pteridaceae) are entirely epiphytic (Gentry and Dodson, 1987).

In comparison to terrestrial ferns, epiphytes must grow in substrates that have a lower nutrient availability and water retention capacity (Benzing, 1990, 1995), and they must cope with large seasonal and daily changes in humidity, as well as an enormous variety of potential hosts (Kramer et al., 1995). Apparent adaptations to prevent water loss include such characteristics as simple or pinnate leaves, thick leaf texture (e.g., Niphidium), an often dense cover of scales (e.g., Polypodium, Elaphoglossum), water storing rhizomes (e.g., Davallia), and leaf succulence together with crassulacean acid metabolism (e.g., Pyrrosia). For humus accumulation and water storage, some ferns have large nest-forming rosettes (e.g., Asplenium) or specific niche-forming leaves (e.g., Drynaria, Platycerium) or leaf bases (e.g., Aglaomorpha). All of the latter group are restricted to the Paleotropics, with the exception of one species of Platycerium (P. andinum) and perhaps Niphidium spp. with large, but morphologically undifferentiated leaves. This nearly complete restriction of humus accumulating fern life forms to the Paleotropics has been interpreted as competitive exclusion by bromeliads, which are absent in the Paleotropics (Kramer et al., 1995). Some other fern species (Solanopteris spp. in the Neotropics, Lecanopteris spp. in the Paleotropics) have ants collecting nutrients for them. These ferns have thick hollow rhizomes that are inhabited by ants. The plants form roots within the interior of the rhizome to take up the nutrients that the ants bring in (Wagner, 1972; Gomez, 1974; Walker, 1986; Gay, 1991).

The concentration of gemmae-forming gametophytes in mainly epiphytic groups such as grammitids (Polypodiaceae), Hymenophyllaceae, and vittarioids (Pteridaceae) is often interpreted as an adaptation of epiphytism (Page, 1979b; Farrar, 1990; Dassler and Farrar, 2001).

Within the understory of wet tropical forests there is a fairly constant air humidity (i.e., from the base of the trunk to about 3 m above ground). Epiphytic ferns abound as lower trunk epiphytes, especially Hymenophyllaceae, and may be the dominant plant group (Zotz and Buche, 2000; Mehltreter et al., 2005). In the drier and exposed canopy, bromeliads and orchids are apparently better adapted to the extreme changes of temperature and humidity (Johansson, 1974; Kelly, 1985; Benzing, 1990).

The first fern epiphytes (e.g., Botryopteris forensis) are known from the Carboniferous, where they grew on marattiaceous tree ferns of the genus Psa-ronius (Rothwell, 1991). For contemporary epiphytes, three main host groups are available as substrate: tree ferns, gymnosperms (e.g., pines), and woody angiosperms. One species usually found growing on tree ferns is Polyphlebium capillaceum (syn. Trichomanes capillaceum) (Mickel and Beitel, 1988; Moran et al., 2003; Mehltreter et al., 2005; Ebihara et al., 2006; (see Table 8.5, Figure 8.3b). It develops especially on the trunk bases when the tree fern develops its adventitious roots forming a continuous root mantle up to half way to the top. This root mantle has a high water retention capacity and porosity because of its entangled roots, which makes it a favorable substrate for many epiphyte species (Heatwole, 1993; Medeiros et al., 1993; Mehltreter et al., 2005), including recently derived fern clades (e.g., Elaphoglossum, Polypodium) that diversified along with the angiosperms (Schneider et al., 2004). However, most modern epiphytes are not restricted to tree ferns and also grow on a wide range of angiosperm hosts. Nevertheless they may be very abundant on tree fern trunks (Table 8.5), which they can cover entirely, for example Asplenium harpeodes, Blechnum fragile (Figure 8.3c), Elaphoglossum lonchophyllum (Figure 8.3a), and Terpsichore asplenifolia (Figure 8.3a) in Mexican cloud forest (Mehltreter, personal observation). On the other hand, some epiphytic ferns do not occur on tree ferns, perhaps because of the acidic pH and high tannin content of the root mantle (Frei and Dodson, 1972), e.g., Elaphoglossum peltatum (Table 8.5, Figure 8.3d). Another example is Vittaria isoetifolia on La Réunion Island, which is only found on angiosperm trees. Its short rhizome may have problems attaching to the surface of the root mantle or even may be overgrown by the latter. Horizontally extended branches of angiosperm trees allow the large leaves of V. isoetifolia to hang down freely and avoid touching the

Table 8.5 Epiphytic ferns with significant host specificities for tree ferns or angiosperm trees in order of their frequency on tree ferns; data are percentages of presence on host trunks

Tree ferns Angiosperm trees

Elaphoglossum decursivum1 95 30

Blechnum fragile1 90 0

Trichomanes capillaceum2 89 0

Pecluma eurybasis1 65 20

Dryopteris patula1 50 0

Elaphoglossum stenoglossum1 50 10

Blechnum attenuatum3 41 4

Campyloneurum sphenodes1 40 0

Hymenophyllum elegans1 35 0

Asplenium auriculatum1 35 5

Asplenium serratum1 30 0

Elaphoglossum petiolatum2 29 4

Trichomanes reptans2 18 67

Asplenium nitens3 2 24

Vittaria isoetifolia3 0 16

Elaphoglossum peltatum2 0 19

1Moran et al., 2003;

2Mehltreter et al., 2005;

3Mehltreter, unpublished data from La Réunion Island.

vertical trunk surface where they would be exposed to competition with other epiphytes.

In conclusion, dozens of epiphytic ferns exhibit host specificity but few are restricted to one host group. Tree ferns are generally a better substrate for trunk epiphytes than angiosperm trees, but there are important exceptions, for which we only have speculative explanations. Specific needs of the gametophyte, the life form of the sporophyte, pH, content of tannins, and structural differences of the root mantle of tree ferns may be involved. Moreover, fern epiphytes specific to angiosperm trees may have been overlooked (Callaway et al., 2002), because these may be restricted to regions where no tree ferns occur. For example, palm trees are especially good substrates when their leaf bases stay attached to the trunk (Zotz and Vollrath, 2003). Their epiphyte communities have been studied mainly in cultivated species. In Costa Rican oil palm fields, Nephrolepis spp. and Phlebodium spp. commonly occur at palm leaf bases (Mehltreter, personal observation). Interestingly, tree fern skirts formed by old leaves that stay attached to the

Figure 8.3 Habitat specificities of Mexican trunk epiphytes on tree ferns (a-c) or on angiosperm trees (d). (a) Elaphoglossum lonchophyllum with entire leaves and Terpsichore asplenifolia with pinnate leaves on Alsophila firma. (b) Trichomanes capillaceum on Alsophila firma. (c) Blechnum fragile on the root mantle of Dicksonia sellowiana. (d) Elaphoglossum peltatum on the tree stem of Quercus spp.

Figure 8.3 Habitat specificities of Mexican trunk epiphytes on tree ferns (a-c) or on angiosperm trees (d). (a) Elaphoglossum lonchophyllum with entire leaves and Terpsichore asplenifolia with pinnate leaves on Alsophila firma. (b) Trichomanes capillaceum on Alsophila firma. (c) Blechnum fragile on the root mantle of Dicksonia sellowiana. (d) Elaphoglossum peltatum on the tree stem of Quercus spp.

trunk were found to inhibit the colonization by larger epiphytes and climbers (Page and Brownsey, 1986).

8.4 Synthesis of current perspectives

Unexpected phenological patterns suggest that we cannot easily draw general conclusions because of limited observations and little quantitative data. We need more detailed quantitative field data across wider geographical and taxonomic scales to understand the fascinating phenology and habitat requirements of ferns. For horticultural purposes, both issues should be of some concern, when species are known to be difficult to cultivate (for example, gram-mitids (Polypodiaceae), Hymenophyllaceae, and Gleicheniaceae). For conservation purposes, specific habitat requirements may restrict some fern species geographically, and may be responsible in part for their endangered status. Hyper-accumulators of heavy metals may be more common in ferns than known until recently and can play an important role in the future as bioindicators and for phytoremediation.

8.5 Future goals and directions

Within the field of ecological research of ferns and lycophytes, there are at least three areas on which future studies should be focused.

(1) Long-term research, especially in the tropics where ferns are most diverse and abundant.

(2) Broad-scale studies within a wide range of species at different latitudes, altitudes, and habitats.

(3) Multi-disciplinary approaches of ecology, physiology, biochemistry, morphology, systematics, and genetics, which combine molecular methods and field experiments.

Whatever approach is selected, quantitative approaches are preferable over observational and merely qualitative studies. Field studies should be comparative or experimental to answer specific questions, for example temperature and soil optima for new species of horticultural interest.

8.6 Importance of long-term studies

Most results of phenological studies depend heavily on climatic conditions at the study site during the years of observation. If these have been exceptional, extrapolations and general conclusions cannot be drawn without the risk of committing significant errors.

For this reason long-term studies are particularly important. Moreover, for conservation purposes it is critical to document complete life cycles of ferns to improve our understanding of demographic processes (see Chapter 9). Long-term growth measurements allow calculation of the ages of individual plants, and determination of quantified survival rates for better estimations of population turnover, which are fundamental values for conservation management.

Our actual understanding of fern phenology is restricted to a few species and even fewer locations. Only studies on a wider geographical scale will allow us to understand, for example, how phenological patterns change within and among species at different latitudes and altitudes. This knowledge is fundamental for addressing future challenges, such as understanding the possible consequences of global warming on ferns. Will tropical fern communities benefit from a warmer climate or will they decline because of a possibly longer dry season? Some species that now produce only one or two fertile leaves per year may discontinue doing so when climatic changes affect their development (Sharpe, 1997; Mehltreter and Palacios-Rios, 2003). Over the long term, this will significantly reduce the reproductive success and increase the chance of extinction of local populations, when these cannot recover from a spore bank.

References

Aide, T. M. (1993). Patterns of leaf development and herbivory in a tropical understorey community. Ecology, 74, 455-466.

Ash, J. (1986). Demography and production of Leptopteris wilkesiana (Osmundaceae), a tropical tree fern from Fiji. Australian Journal of Botany, 34, 207-215.

Ash, J. (1987). Demography of Cyathea hornei (Cyatheaceae), a tropical tree-fern from Fiji. Australian Journal of Botany, 35, 331-342.

Barger, T. W., Durham, T. J., Andrews, H. T., and Wilson, M. S. (2007). Gametophytic and sporophytic responses of Pteris spp. to arsenic. American Fern Journal, 97, 30-45.

Barrington, D. S. (1993). Ecological and historical factors in fern biogeography. Journal of Biogeography, 20, 275-280.

Beever, J. E. (1984). Moss epiphytes of tree-ferns in a warm-temperate forest, New Zealand. Journal of the Hattori Botanical Laboratory, 56, 89-95.

Bennicelli, R., Stepniewska, Z., Banach, A., Szajnocha, K., and Ostrowski, J. (2004). The ability of Azolla caroliniana to remove heavy metals (Hg(II), Cr(III), Cr(VI)) from municipal waste water. Chemosphere, 55, 141-146.

Benzing, D. H. (1990). Vascular Epiphytes. Cambridge: Cambridge University Press.

Benzing, D. H. (1995). Vascular epiphytes. In Forest Canopies, ed. M. D. Lowman and N. M. Nadkarni. San Diego, CA: Academic Press, pp. 225-254.

Bittner, J. and Breckle, S. W. (1995). The growth rate and age of tree fern trunks in relation to habitats. American Fern Journal, 85, 37-42.

Brokaw, N. V. L. (1996). Treefalls: frequency, timing and consequences. In The Ecology of a Tropical Forest: Seasonal Rhythms and Long-term Changes, ed. E. G. Leigh, A. S. Rand, and D. M. Windsor, 2nd edn., Washington, DC: Smithsonian Institution Press, pp. 101-108.

Bullock, S. H. and Solis-Magallanes, J. A. (1990). Phenology of canopy trees of a tropical deciduous forest in Mexico. Biotropica, 22, 22-35.

Callaway, R. M., Reinhart, K. O., Moore, G. W., Moore, D. J., and Pennings, S. C. (2002). Epiphyte host preferences and host traits: mechanisms for species-specific interactions. Oecologia, 132, 221-230.

Chiou, W.-L., Lin, J. C., and Wang, J. Y. (2001). Phenology of Cibotium taiwanense (Dicksoniaceae). Taiwan Journal of Forestry Science, 16, 209-215.

Christ, H. (1910). Die Geographie der Farne. Jena: Fischer.

Copeland, E. B. (1947). Genera Filicum. Waltham, MA: Chronica Botanica.

Cortez, L. (2001). Pteridofitas epífitas encontradas en Cyatheaceae y Dicksoniaceae de los bosques nublados de Venezuela. Gayana Botanica 58, 13-23.

Dassler, C. L. and Farrar, D. R. (2001). Significance of gametophyte form in long distance colonization by tropical, epiphytic ferns. Brittonia, 53, 352-369.

Durand, L. Z. and Goldstein, G. (2001). Photosynthesis, photoinhibition, and nitrogen use efficiency in native and invasive tree ferns in Hawaii. Oecologia, 126, 345-354.

Ebihara, A., Dubuisson, J.-Y., Iwatsuki, K., Hennequin, S., and Ito, M. (2006). A taxonomic revision of Hymenophyllaceae. Blumea, 51, 221-280.

Ewers, F. W., Cochard, H., and Tyree, M. T. (1997). A survey of root pressures in vines of a tropical lowland forest. Oecologia, 110, 191-196.

Farrar, D. R. (1990). Species and evolution in asexually reproducing independent fern gametophytes. Systematic Botany, 15, 98-111.

Francesconi, K., Visoottiviseth, P., Sridokchan, W., and Goessler, W. (2002). Arsenic species in an arsenic hyperaccumulating fern, Pityrogramma calomelanos: a potential phytoremediator of arsenic-contaminated soils. Science of the Total Environment, 284, 27-35.

Frei, J. K. and Dodson, C. H. (1972). The chemical effect of certain bark substrates on the germination and early growth of epiphytic orchids. Bulletin of the Torrey Botanical Club, 99, 301-307.

Gay, H. (1991). Ant-houses in the fern genus Lecanopteris: the rhizome morphology and architecture of L. sarcopus and L. darnaedii. Botanical Journal of the Linnean Society, 106, 199-208.

Gemma, J. N., Koske, R. E., and Flynn, T. (1992). Mycorrhizae in Hawaiian

Pteridophytes: occurence and evolutionary significance. American Journal of Botany, 79, 843-852.

Gentry, A. H. and Dodson, C. H. (1987). Diversity and biogeography of neotropical vascular epiphytes. Annals of the Missouri Botanical Garden, 74, 205-233.

Gomez, L. D. (1974). Biology of the potato-fern, Solanopteris brunei. Brenesia, 4, 37-61.

Heatwole, H. (1993). Distribution of epiphytes on trunks of the arborescent fern Blechnum palmiforme, at Gough Island, South Atlantic. Selbyana, 14, 46-58.

Hernández, A. C. (2006). Fenología foliar de helechos terrestres en un fragmento de bosque mesáfilo de montaa en Xalapa, Veracruz, Mexico. Tesis de Licenciatura en Biología, Universidad Veracruzana, Xalapa.

Holttum, R. E. (1938). The ecology of tropical pteridophytes. In Manual of Pteridology, ed. F. Verdoorn. The Hague: M. Nijhoff, pp. 420-450.

Johansson, D. (1974). Ecology of vascular epiphytes in West African rain forest. Acta Phytogeographica Suecica, 59, 1-130.

Kelly, D. L. (1985). Epiphytes and climbers of a Jamaican rain forest: vertical distribution, life forms and life histories. Journal of Biogeography, 12, 223-241.

Kornás, J. (1977). Life-forms and seasonal patterns in the pteridophytes of Zambia. Acta Societatis Botanicorum Poloniae, 46, 668-690.

Kramer, K. U., Schneller, J. J., and Wollenweber, E. (1995). Farne und Farnverwandte. Stuttgart: Thieme.

Lieberman, D. and Lieberman, M. (1984). The causes and consequences of synchronous flushing in a tropical dry forest. Biotropica, 16, 193-201.

Lloyd, R. M. and Buckley, D. P. (1986). Effects of salinity on gametophyte growth of Acrostichum aureum and Acrostichum danaeifolium. Fern Gazette, 13, 97-102.

Ma, L. Q., Komar, K. M., Tu, C., Zhang, W., Cai, Y., and Kennelley, E. D. (2001). A fern that hyperaccumulates arsenic. Nature, 409, 579.

Medeiros, A. C., Loope, L. L., and Anderson, S. J. (1993). Differential colonization by epiphytes on native (Cibotium spp.) and alien (Cyathea cooperi) tree ferns in a Hawaiian rain forest. Selbyana, 14, 71-74.

Mehltreter, K. (2006). Leaf phenology of the climbing fern Lygodium venustum in a semi-deciduous lowland forest on the Gulf of Mexico. American Fern Journal, 96, 21-30.

Mehltreter, K. and Garcáa-Franco, J. G. (in press). Leaf phenology and trunk growth of the deciduous tree fern Alsophila firma in a Mexican lower montane forest. American Fern Journal.

Mehltreter, K. and Palacios-Rios, M. (2003). Phenological studies of Acrostichum danaeifolium (Pteridaceae, Pteridophyta) at a mangrove site on the Gulf of Mexico. Journal of Tropical Ecology, 19, 155-162.

Mehltreter, K., Flores-Palacios, A., and Garcáa-Franco, J. G. (2005). Host preferences of vascular trunk epiphytes in a cloud forest of Veracruz, Máxico. Journal of Tropical Ecology, 21, 651-660.

Mehltreter, K., Hulber, K., and Hietz, P. (2006). Herbivory on epiphytic ferns of a Mexican cloud forest. Fern Gazette, 17, 303-309.

Mickel, J. T. and Beitel, J. M. (1988). Pteridophyte Flora ofOaxaca, Mexico. New York: New York Botanical Garden.

Mickel, J. T. and Smith, A. R. (2004). The Pteridophytes of Mexico. New York: New York Botanical Garden.

Moran, R. C., Klimas, S., and Carlsen, M. (2003). Low-trunk epiphytic ferns on tree ferns versus angiosperms in Costa Rica. Biotropica, 35, 48-56.

Nishizono, H., Suzuki, S., and Ishii, F. (1987). Accumulation of heavy metals in the metal-tolerant fern Athyrium yokoscense, growing on various environments. Plant and Soil, 102, 65-70.

Oliver, W. R. B. (1930). New Zealand epiphytes. Journal of Ecology, 18, 1-50.

Page, C. N. (1979a). The diversity of ferns. An ecological perspective. In The

Experimental Biology of Ferns, ed. A. F. Dyer. London: Academic Press, pp. 10-56.

Page, C. N. (1979b). Experimental aspects of fern ecology. In The Experimental Biology of Ferns, ed. A. F. Dyer. London: Academic Press, pp. 552-589.

Page, C. N. and Brownsey, P. J. (1986). Tree-fern skirts: a defense against climbers and large epiphytes. Journal of Ecology, 74, 787-796.

Pocs, T. (1982). Tropical forest bryophytes. In Bryophyte Ecology, ed. A. J. E. Smith. London: Chapman and Hall, pp. 59-104.

Poulsen, A. D., Tuomisto, H., and Balslev, H. (2006). Edaphic and floristic variation within a 1-ha plot of lowland Amazonian rain forest. Biotropica, 38, 468-478.

Rivera, G., Elliott, S., Caldas, L. S., Nicolossi, G., Coradin, V. T. R., and Borchert, R. (2002). Increasing day-length induces spring flushing of tropical dry forest trees in the absence of rain. Trees, 16, 445-456.

Rothwell, G. W. (1991). Botryopteris forensis (Botryopteridaceae), a trunk epiphyte of the tree fern Psaronius. American Journal of Botany, 78, 782-788.

Schmitt, J. L. and Windisch, P. G. (2005). Aspectos ecologicos de Alsophila setosa Kaulf. (Cyatheaceae, Pteridophyta) no Rio Grande do Sul, Brasil. Acta Botanica Brasilica, 19, 859-865.

Schmitt, J. L. and Windisch, P. G. (2006). Phenological aspects of frond production in Alsophila setosa (Cyatheaceae, Pteridophyta) in Southern Brazil. Fern Gazette, 17, 263-270.

Schneider, H., Schuettpelz, E., Pryer, K. M., Cranfill, R., Magallon, S., and Lupia, R. (2004). Ferns diversified in the shadow of angiosperms. Nature, 428, 553-557.

Seiler, R. L. (1981). Leaf turnover rates and natural history of the Central American tree fern Alsophila salvinii. American Fern Journal, 71, 75-81.

Sela, M., Garty, J., and Tel-Or, E. (1989). The accumulation and the effect of heavy metals on the water fern Azolla filiculoides. New Phytologist, 112, 7-12.

Sharpe, J. M. (1993). Plant growth and demography of the neotropical herbaceous fern Danaea wendlandii (Marattiaceae) in a Costa Rican rain forest. Biotropica, 25, 85-94.

Sharpe, J. M. (1997). Leaf growth and demography of the rheophytic fern Thelypteris angustifolia (Willdenow) Proctor in a Puerto Rican rainforest. Plant Ecology, 130, 203-212.

Sharpe, J. M. and Jernstedt, J. A. (1990). Leaf growth and phenology of the dimorphic herbaceous layer fern Danaea wendlandii (Marattiaceae) in a Costa Rican rain forest. American Journal of Botany, 77, 1040-1049.

Sharpe, J. M. and Jernstedt, J. A. (1991). Stipular bud development in Danaea wendlandii (Marattiaceae). American Fern Journal, 81, 119-127.

Tanner, E. V. J. (1983). Leaf demography and growth of the tree-fern Cyathea pubescens Mett. ex Kuhn in Jamaica. Botanical Journal of the Linnaean Society, 87, 213-227.

Tuomisto, H. (2006). Edaphic niche differentiation among Polybotrya ferns in western Amazonia: implications for coexistence and speciation. Ecography, 29, 273-284.

Tryon, R. M. (1960). The ecology of Peruvian ferns. American Fern Journal, 50, 46-55.

Tryon, R. M. (1964). Evolution in the leaf of living ferns. Bulletin of the Torrey Botanical Club, 21, 73-85.

van Steenis, C. G. G. J. (1981). Rheophytes of the World. Alpen an den Rijn: Sijthoff and Noordhoff.

van Steenis, C. G. G. J. (1987). Rheophytes of the world: supplement. Allertonia, 4, 267-330.

Wagner, W. H. (1972). Solanopteris brunei, a little known fern epiphyte with dimorphic stems. American Fern Journal, 62, 33-43.

Wagner, W. H., Jr. and Wagner, F. S. (1977). Fertile-sterile leaf dimorphy in ferns. Gardens Bulletin Singapore, 30, 251-267.

Walker, T. G. (1986). The ant-fern Lecanopteris mirabilis. Kew Bulletin, 41, 533-545.

Westoby, M., Warton, D., and Reich, P. B. (2000). The time value of leaf area. American Naturalist, 155, 649-656.

Williams-Linera, G. (1997). Phenology of deciduous and broadleaved-evergreen tree species in a Mexican tropical lower montane forest. Global Ecology and Biogeography Letters, 6, 115-127.

Zotz, G. and Buche, M. (2000). The epiphytic filmy ferns of a tropical lowland forest - species occurrence and habitat preferences. Ecotropica, 6, 203-206.

Zotz, G. and Vollrath, B. (2003). The epiphyte vegetation of the palm Socratea exorrhiza - correlations with tree size, tree age and bryophyte cover. Journal of Tropical Ecology, 19, 81-90.

Was this article helpful?

0 0
10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment