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Microgramma sub-genus Solanopteris

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Ant Ferns, New World.

Microgramma sub-genus Solanopteris Ant-house Ferns.

Microgramma bifrons. Microgramma bismarckii. Microgramma brunei. Microgramma fosteri. Microgramma tuberosa.


Microgramma sub-genus Solanopteris Ant-House Ferns.

Microgramma Carl Bořivoj Presl published in Tentamen Pteridographiae 213, 1836. Type Microgramma persicariifolia (Schrad.) C. Presl.  Basionym Polypodium persicariifolium Heinrich Adolph Schrader published in Göttingische gelehrte Anzeigen unter der Augsicht der Königl, 1824.  Solanopteris, the so-called Potato Ferns of the New World tropics are now considered a sub-genus of Microgramma. (Smith et al. 2006.)

  Etymology of Solanopteris is derived from the words solanum pertaining to the potato genus because their tubers are somewhat potato-like and pteris - fern.  Currently most information about these species will be found under Solanopteris in the small amount of literature available but that is now changing, as these weird plants become better known.

  Etymology of Microgramma is derived from the Latin word micro (small) and the Greek word gramma or grammatos meaning "a line or thread" referring to the linear arrangement of sori (spore clusters) on fertile leaves.

  They are primarily high-perching epiphytes living on exposed outermost branches of trees in (ever wet?) forests; therefore, it is only on windfall or near canopy margins such as around clearings and waterways or from jungle ridge tops that they are most visible if not more accessible.

Their long, thin, rhizomes (fern stolons) have, at closely set intervals, very short side branches that end in approximately golf-ball sized tubers each containing a number of hollow chambers.  A single ventral (underneath) entrance hole provides access for both roots and ants, resulting in tubers usually being inhabited by highly protective and very aggressive colonies of Azteca or Camponotus ant species.

  It was long thought that the tubers merely stored utilizable water, as do succulent plants until closer study revealed their intimate relationship with ant colonies.

Over time, resident ants fill home tubers with the remains of their animal prey, uneaten plant scraps, and their bodily wastes, to eventually abandon them for younger, empty domatia as they are grown. Fertilisers derived from resulting nutrient-rich composts are accessed via adventitious roots that spread along inner chamber walls after entering through the same ventral entrance the ants use.

  We will see in other very different plant families that diverse epiphytic ant-house plants often follow essentially similar strategies but they often use very different plant organs.

  Yet something extraordinary happens to mature, debris containing, ant-abandoned Microgramma tubers, events not reported for any other ant-domatia. They shrink, compacting around inner detritus while their surfaces become porous to rainwater, creating novel, spongy, water reservoirs. (Moran, R. 2004.)

Microbes proliferate best in appropriately damp conditions, so wetting detritus speeds up its decomposition enabling faster recycling of nutrients.  Yet as we will see from studies of other ant-house plants, there is possibly more happening here than has so far been reported.

  It has been claimed that resident ants hollow the tubers themselves but I think this is very unlikely.  However, it seems possible that ants might enlarge tuber cavities especially if some internal tissues have evolved to be ant nutritious.

  I am not aware of empirical evidence that confirm nutrient uptake from resident ants and their debris for any Microgramma species; however, as we will see from studies performed on numbers of other ant-house plants including ferns, it is very probable.

  Although ant gardens are common in New World tropics, epiphytic ant-house species are reputedly much rarer in the Americas than they are in southern Asia.  The exceptions in addition to these few fern species are numbers of bromeliads, especially Tillandsia species.  Yet further fieldwork, especially of species such as Markea may widen numbers.

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Microgramma brunei (Wercklé ex H. Christensen) David Bruce Lellinger published in the American Fern Journal 67(2) 1977. Basionym Polypodium brunei Karl (Carl) Wercklé Ex Konrad Hermann Christensen published in Bulletin De La Société Botanique De Genève, Sér. 2 1(5), 1909.  Synonym Solanopteris brunei (Wercklé Ex H. Christ.) Warren Herbert Wagner published in American Fern Journal 62, 1972.

Ecology:  I Quote “The Potato-Ferns, Genus Solanopteris (sic), are associated with ants; in Costa Rica with Azteca species.  The ant associated with S. brunei (sic) has been identified as Azteca traili var. filicis Forel, which has not previously been reported from Costa Rica, but is known from Peru.” “The presence of a South American insect at the northernmost range of Solanopteris implies that the ferns & ants have coevolved not only biologically, but also geographically.” (Gomez 1977.)

Range:  Central America (Nicaragua, Costa Rica, Panama) South America, (Colombia and Ecuador) and from the Gomez Report above probably in Peru.

Records:  Costa Rica, Type Collection 1904 near Araya, Cartago Province, La Selva De Pejibaye.  La Selva De translates as “The Forest Of” and Pejibaye are large, tall, thorny, edible-fruit-bearing palm trees called Peach Palms locally.  This may mean that this species can occupy agricultural forests, as do so many other ant-house epiphytes.  The fern expert Robbin Moran (2002) records a specimen at Alajuela on an isolated tree in pasture near Alberto Brenes Biological Station (Estacion Biologica Alberto Brenes), north of San Ramon at 900 m (2953 ft.)  In 2004, he records another site at Alajuela but higher at 1,000 m. (3281 ft.)Annual rainfall at the station is 3500 mm (138 inches.) and although there is a summer/autumn dry season from Jan to May, it is rainy (but often only light-drizzles) almost all year long.


Unfortunately this program corrupts my following chart

Mean High & Low Temperatures, San Ramon City, Costa Rica at 1057 M (3468 Ft.)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 28°C 29°C 30°C 30°C 29°C 28°C 28°C 28°C 28°C 28°C 28°C 28°C 18°C 18°C 18°C 19°C 19°C 19°C 19°C 18°C 18°C 18°C 18°C 18°C

 Mean Rainfall & Number Of Rainy Days, San Ramon City, Costa Rica.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 8mm 10mm 9mm 45mm 170mm 206mm 141mm 192mm 240mm 290mm 137mm 44mm 4 2 4 8 21 23 22 22 26 26 19 9

Ecuador:  Esmeraldas Province; at 740 m (2428 ft.), grid reference 00°53'31"N. 78°31'41"W. which places the collection site inland, fractionally north of the equator and in the middle of jungle wilderness north of the Esmeraldas River.  This is especially interesting being a very rare record from the Pacific side of the high Andes.  Regions facing the Pacific Ocean must cope with the drought to flood vagaries of El Nino/La Nina, weather patterns.  Perhaps some Microgramma do have to cope with the similar dry spells experienced by many southern Asian arboreal ant-house species.The University Of Connecticut (UCONN) grows M. brunei.  They recommend plants be grown in hanging baskets in fern mix.  To facilitate propagation, allow rhizomes to establish in a new basket before division.  Propagations do not survive well if rhizomes are detached too early.

These plants are not native to the sovereign nation of Brunei on Borneo Island.

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if solanopteris  is a sub genus, why named these one microgramma ?


the revision to 20-07-2001  from M.HASSLER and B.SWALE  speak just to Solanopteris    


if you speak to microgramma  you must write  Migrogramma subgen Solanopteris  brifons  for example  for me it is a taxonomy  aberration


With the others  Microgramma  species ( not myrmecophile) what you make ?


Solanopteris   to COPEL in 1951 ;

Microgramma subgen Solanopteris ( Copel)   Lellinger  1977   no anteriority  problem ?



I do not know the specie fosteri  this one have also a tuber?


In the new revision Solanopteris no trace to this M.fosteri 


may be a dna analysis are more interessant  for this genus  or subgenus  no?


have you the SMITH document to  2006 ? it is a new revision or just a parution?



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