The Ferns of Brazilian Amazonia

An annotated list of the pteridophytes of Brazilian Amazonia is presented, with the geographic occurrence of the species by States and Territories. The flora includes 12 families, 58 genera and 279 species, with only four species possibly endemic. Two new combinations are Arachnoides macrostegia (Hook.) Tryon & Conant and Thelypteris juruensis (C. Chr.) Tryon & Conant. Some general comments on the geography of Amazoruan ferns are included as well as ecological studies presenting data on the local environmental preferences of six species. There have been no general accounts of the fern flora of the Amazon Basin and few reports on fern ecology from the region. This paper presents an annotated, geographic list of the Pteridophyta of the States of Amazonas, Pará and Acre, and the Territories of Amapá, Rondônia and Roraima. Records from the Amozonian (northern) part of the State of Mato Grosso have not been included since there are so few collections from that region. ·oetailed studies on t ropical American fern ecology are limited and much more work is required even to establish such fundamental aspects as the relation of species to environment. Ecological studies were made in the vicinity of Manaus, as part of the Class on Pteridophyta, Curso de Botânica Tropical do INPA. These indicate a strong preference of each of the species analyzed for a portion of an environmental gradient.

There have been no general accounts of the fern flora of the Amazon Basin and few reports on fern ecology from the region.This paper presents an annotated, geographic list of the Pteridophyta of the States of Amazonas , Pará and Acre, and the Territories of Amapá, Rondônia and Roraima.Records from the Amozonian (northern) part of the State of Mato Grosso have not been included since there are so few collections from that region.
•oetailed studies on t ropical American fern ecology are limited and much more work is required even to establish such fundamental aspects as the relation of species to environment.Ecological studies were made in the vicinity of Manaus, as part of the Class on Pteridophyta, Curso de Botânica Tropical do INPA.These indicate a strong preference of each of the species analyzed for a portion of an environmental gradient.

GEOGRAPHIC COMMENTS
The most outstanding fact of Amazonian fern geography is that species endem:sm is either extremely low or entirely absent.The regicrt is a very large and rather diversified one, yet only four species among 279 listed are Rolla M. Tryon ( *) David S. Conant (**) confined to the area.These are Selaginel/a manausensis, S. Terezoana, lsoetes amazonica and /. triangu/a.These species are known from so few collections that their actual distribution is not certa in.Other, presently dubious, species may be added to this list.However, endemism among the Pteridophyta is exceptionally low, in contrast to the significant endemism in the flowering plants.For example, in 5 genera discussed by Prance (1973), Ltcania, Hirtella, Tapura, Dichapetalum and Cariniana, there is a total of 25 endemics in Brazilian Amazonia.
Most of the species we have listed may be considered as truly Amazonian ferns in the sense that they grow, rarely to commonly, in one or more of the habitats that are distributed through the Amazon Basin.A small element, however, enters our list only because of the political-geographié definition of the area.This is a clear Andean element known only in the State of Acre.lt consists of about 15 species, for example, Nephelea cuspidata, Adiantum platyphyllum, A. scalare, Diplazium marginatum, D. praestans, and Pteris pungens.
The largest genera are Selaginella with 31 species, Polypodium with 30, Trichomanes with 27, Lindsaea w ith 22, and Adi antum and Asplenium with 16 species each.The large number of species i n Trichomanes and Lindsaea is especially notable.In each genus they are predominantly species of the Guayana region to the north.Most, but not ali, o f the Polypodium species are widely distributed in tropical Ame rica.Their number reflects the large size of the genus in America when it is construed, as we do here, in the broad sense.The species of Se/aginella also reflect the size ot the genus, for there are about 130 speci es in tropical South America.
Genera that are notably under-represented are Thelypteris (in the broad sense) with 12 species, Elaphog/ossum with 9, Pteris with 6 (3 of them in the Andean element of Acre), and Lycopodium with 5 species.The reasons for the relatively few species in genera that are much better represented to the north, west and south, are not clear.Perhaps the absence of relatively cool and nearly constantly moist environments is a decisive factor in limiting their development in Amazonia.

ECOLOGY
Trichomanes arbuscula and Elaphoglossum discolor we1e studied on a densely wooded stream bank at krn 130 on the Manaus to Caracaraí road.Ten 1 m by 1 m plots were laid out at 4 m intervals along the border of the stream, and each of these was extended up the bank by the addition of two 1 m 2 plots.Ali fern plants within these 30 m 2 were identified and counted.They included 176 plants of Trichomanes arbuscula, 76 plants of Elaphog/ossum disco/ar, 3 plants of E. glabellum and 1 plant of Lindsaea Schomburgkii.The distribution of the two common species was analyzed with reference to their occurrence in the m 2 bordering the stream and the ones farther from the stream.The results are tabulated 111 Table 1.Trichomanes arbuscu/a is a terrestrial filmy fern and Elaphoglossum discolor is a coriaceous leaved epiphyte.They both show a pronounced preference for proximity to the stream.Art-important aspect of the environmental gradient for both species is probably the increased light near the stream.The d:stribution of the Trichomanes is probably also 24-influenced by the more constantly wet soil on the lower slopes of the stream bank, partly due to seepage and partly due to seasona! inundation.Polypodium nanum is a small species with thin leaves .lt oeeurred most frequently on the lower 60 em of the trunks and with clearly diminishing frequency above 120 em.This distribution may be based on a humidity gradient that is highest near the base of the trees.
Elaphoglossum glabel/um is a somewhat larger species with narrow, coriaceous leaves.lt occurred with considerable frequency up to 180 em and then diminished in numbers above that height.The relatively even distribution of the Elaphoglossum through 180 em of trunk does not suggest a gradient.lt is a more xeromorphic species than the Polypodium and perhaps is well adapted to a broader range of moisture conditions.The F value computed from the data for both species when they were growing together shows a highly significant statistical difference between them .The F test result of 20. 78 is much higher than the required 6. 79 at the 1% levei.This comparison indicates that each species has different environmental preferences which are expressed in their distribution on the tree trunks.Competition is not indicated as a part of the environment since the data on Elaphoglossum, when growing by itself, shows no statistically significant difference from the data when it was growing with the Polypodium.The F test result of 2.35 is well below the levei of 6. 79 which would indicate a significant difference for these sets of data.
Schizaea pennula and Schizaea stricta were frequent in the sandy soils of the campina at the Estação Experimental de Silvicultura Tropical, km 60 on the Manaus to Caracaraí road.In the area where these species grew, t here were small to rather large clumps of shrubs and small trees separated by irregular areas of open sand.Under the woody growth (Zone A) there is shade, considerable dry leaf litter, and a humus layer about 3-5 em in depth.In the open sand areas (Zone C) there is shade for only a portion of a day, no leaf litter and no definite humus layer .Shade and soil conditions are intermediate in the areas shaded by peripheral branches (Zone B) beyond the trunks of the trees and shrubs.The temperatura.light, and soil moisture condi-tion~ undoubtedly form a step-like, rather than a gradual gradient, with marked changes occurring over a distance of a few decimeters at the border of the zones.An analysis of the The fems of Brazilian ... distribution of the two Schizaea species in the three zones of the campina is shown in Table 3.
Schizaea pennula had a marked preference for the sites under the woody growth of the campina and Schizaea stricta for sites near its periphery.Schizaea incurvata also occurred in the campina.Six plants were seen, four of them in Zone B and 2 in Zone C. The areas of open sand had few Schizaea plants , only 10% of the 50 observed.The following list of the Pteridophyta of the Amazon Region of Brazil and the distribution of the species by States and Territories has been obtained from field work and from studies of the extensive collections in the herbaria of the Instituto Nacional de Pesquisas da Amazônia, Manaus, the Museu Paraense Emílio Goeldi, and the Instituto de Pesquisas e Experimentação Agropecuária do Norte, Belém.A collection in one (or more) of these herbaria is indicated by an X under the appropriate geographic heading, or in the case of the State of Amazonas, species recorded from the Reserva Florestal Ducke have been indicated by a D and those from the Estação Experimental de Silvicultura Tropical by an E. This provides a checklist for the pteridophytes of these two reserves near Manaus that may be useful to botanists working at INPA .A total of 45 species is recorded from Ducke and 47 from the Estação Experimental.
Other recor''s have been cited from modern monographs that include species of the rcgion and , in addition, some other literature and an occasional collection in the Gray Herbarium, Harvard University.These sources are indicated under a geographic heading by a number that refers to the notes that follow the list.Comments on certa in species or on their names are also included in the notes and these are indicated by a number following the na me of the species.
This list of 279 species includes ali of the more common species and many of the rare .lt is expected that further study and collecting will increase the number of species to over 300 and extend the range of many of the species.
( 3 l -Sometimes p<~rts, or ali, of an erect branch system bear small (ca 2 mm long) lateral leaves rather than those of the usual size (ca 3 mm long).These small leaves give a very unusual appearance in contrast to the coarser normal pattern (Conant 1161, 1484).( 4) -lncluding Selaginella penniformis (lam.)Hieron.(12) -This identification is somewhat uncertain.Conant 986, among others, has t he I e aves 2-3 times forked and the fertile not much taller than the sterile .This differs from typical Schizaea incurvata which h as the leaves o-2 times forked .The 3-forked I e aves relate the material to S .stricta, which h as leaves 2-6 times forked .

Amapá Pará Amazonas
Hcwever. S. stricta typically has the leaves much taller than the sterile.Since the material can not be refered to either species with certainty, we prefer to use the name S. stricta to call attention to lhe problern of variation in the two spacies.(13) -Material seen from near Manaus was steri le: it was in a fl oating mat and had spongy stems and large leaflets up to c a 3 em long.Fert i le plants are much smaller and probably occur only wh en the plants are rooted in mud .(14) -Sota, E. R. de la, Salvinia oblongifolia Martlus.

TABLE 2 .
Data were obtained on the height above the ground that plants of eaeh species oecurred.A tota l of 249 plants of Elaphog/ossum glabellum were measured and 125 of Polypodium nanum.The results are presented in Table 2. Distribution of plants of two species of ferns growing on tree trunks.

TABLE 3 .
Number of plants of two Schizaea.species in zon.:s (see text) of the campina.
) Schott is primarily Carribean but reaches Venezuela and possibly has escaped from cultivation in other parts of South America, the upper costa surface is glabrous to sparsely scaly.The native N .biserrata(Sw.)Schot has, in Brazillan col lections such as Prance 15680 and Pires & Black 677, thP costa w it h long, pele, f lexous trichomes often mlxed with much dlssected scales.The feros o f