The Ptychanthoideae of Latin America : An Overview ( Studies on Lejeuneaceae Subfamily Ptychanthoideae XVI )

Recent taxonomic studies on the Lejeuneaceae subfamily Ptychanthoideae indicate that there are 59 species in 21 genera in Latin America. The ptychanthoid flora is very different from that of the Old World and has much fewer species but is slightly richer in endemic genera. About one third of the species are widespread neotropical elements, eleven species are transoceanic- wide tropical, and the remaining species have more restricted distributions and belong to the endemic, Caribbean, Amazonian or Andean element. Data on sex distribution in the species indicate that bisexuality in Ptychanthoideae is much more common than previously assumed. The biogeography of the transoceanic species is briefly discussed. The Lejeuneaceae subfamily Ptychanthoideae in- clude about 170 species in 25 genera world-wide (Gradstein 1985a). They are primarily recognised by the seta, which is made up of 20 or more tiers of cells (usually 16 outer and 4 inner). In addition, Ptychanthoideae have a number of characteristics which are less constant or exclusive than the seta

. They are primarily recognised by the seta, which is made up of 20 or more tiers of cells (usually 16 outer and 4 inner).In addition, Ptychanthoideae have a number of characteristics which are less constant or exclusive than the seta structure, e.g., 1) the relatively robust size of the plants and stems; stems with 10-75 rows of epidermal cells and a ventral merophyte of 4-16 cells across (except Dicranolejeunea and Acanthocoleus), 2) the frequent presence of brownish or blackish pigmentation and Frullania type branching, 3) en- tire underleaves ("holostipous"), 4) the hyaline pa- pilla of the lobule apex, which is usually positioned on the inner surface of the lobule (by exception marginal in modified lobules), 5) the presence of bracteoles throughout the male spike (except in Neurolejeunea, Stictolejeunea and Symbiezidium ), and 6) the frequent presence of pinguisane-type ses- quiterpenes (Gradstein et al., in press).
Gametophytically, this genus is very similar to Ptychanthus and when sterile the two genera may easily be confused.The absence of leaf brace cells in Bryopteris can scarcely be taken as a major taxo- nomic character (Aphanolejeunea lacks brace cells too, see Thiers 1982), and a seta with more than 20 tiers of cells and a Frullania type sporeling, char- acteristic for Bryopteris (Stotler & Crandall-Stotler   1974), are also found in Trocholejeunea sandvicen- sis.Van Slageren ( 1985) recently showed that Trocholejeunea infuscata also has a seta of more than 20 rows of cells.I believe that the occurrence of a rather massive seta and sporeling in Bryopteris and Trocholejeunea is probably the result of parallel evolution within the Ptychanthoideae.It should also be realized that sporophytes have been examined thus far in only about 30% of the species and it may well be possible, therefore, that such deviating setas and sporelings do occur in other taxa of Ptychanthoideae as well.We certainly need more work on the morphology of the sporophyte of the Ptychanthoideae to arrive at a proper understanding of the variation of sporophytic characters within the subfamily.

Distribution
The areas of distribution of the Latin American species of Ptychanthoideae fall into the following categories: endemic (7 species), Caribbean (5 species), Amazonian (10 species), Andean (7 species), wide- spread neotropical (19 species) and wide tropical (11 species).The endemic element includes three species which are thus far known from only one collection: Blepharolejeunea chimantaensisfrom the Chimanta table mountain in Venezuela (leg.Steyermark), Spruceanthus theobromae collected by Spruce around Guayaquil, Ecuador and Verdoor- nianthus griffinii which, surprisingly, is known only from the campus of the university of Manaus, Brazil (leg.D. Griffin) and has never been found elsewhere in Amazonia.
Other endemic species include Frullanoides la- ciniatiflora from Peru and Fr.mexicana known from a few localities in southern Mexico and northern Honduras.The latter species should be looked for elsewhere in Central America.At the infraspecific level several endemic taxa have been recognised as well and these include Frullanoides densifolia ssp.
grandidentata (Clark) van Slag, from the Galapagos Islands, Stictolejeunea balfourii var.bekkeri Gradst.from the Guianas (Suriname, French Guiana (new)) and Symbiezidium transversale ssp.dentatum(Herz.) Gradst.& van Beek from the Pacific coast of north- ern South America (Colombia, Ecuador).The latter subspecies is an example of a "Choco element" (Gentry 1982).This element is very rich in endemic vascular plants, but among bryophytes only few en- demic taxa are known; this may be due to poor knowledge of the bryoflora of the area.Other ex- amples of Choco elements in Lejeuneaceae seem to be Spruceanthus theobromae (to be re-collected!) and Luteolejeunea herzogii (Buchloh) Piippo (see Piippo 1986).
The Caribbean element includes species which occur preferably in coastal areas and may be tolerant TABLE 1.
A classification of the genera of Lejeuneaceae subfam.Ptychanthoideae from Latin America.For a cir- cumscription of the tribes and subtribes see Gradstein   (1975) and Van Slageren (1985).
1. Tribus Ptychantheae Bischler Subtribus Ptychanthinae Gradst.Bryopteris complex: Bryopteris Ptychanthus complex: Thysananthus, Mastigolejeu- nea, Schiffneriolejeunea Acrolejeunea complex; Frullanoides, Acrolejeunea Caudalejeunea complex: Caudalejeunea Subtribus Archilejeuninae(Gradst.) Gradst.comb, nov,   (Tribus Archilejeuneae Gradst., Bryophyt.Bib-  lioth.4: 146, 1975  1985).Some of them are restricted to the islands of the West Indies (Frullanoides bahamensis, Neuro- lejeunea catenulata), others occur also on the main- land of Central and/or South America (Acanthocoleusjuddii, Frullanoides corticalis, Lopholejeunea quelchii).Frullanoides corticalis is the most widely distributed species in this category and occurs also in the coastal areas of southeastern Brazil, possibly as the result of a long-range dispersal event (van Slageren 1985).Amazonian species include wide- spread taxa such as Archilejeunea fuscescens (=A.juliformis) and Acrolejeunea torulosa, occurring throughout the lowlands of northern South America east of the Andes, and taxa with more restricted distributions such as Archilejeunea porelloides and A. crispistipula and Verdoornianthus marsupiifolius, which are known only from the forests of inner Amazonia.Neurolejeunea seminervis and Schiff- neriolejeunea amazonica are Amazonian species with a wide but rather scattered distribution.Only a few collections are available for each of them.In the Guianas these two species occur in the high canopy of the rain forest (unpublished observation) and I would therefore suspect that the inaccessibility of the habitat is a reason why so few records are known.
The Andean element includes species which are mainly distributed in the Andes of tropical South America.They may also occur in the mountains of Central America, however, and sometimes their About half of the species ofPtychanthoideae oc- curring in Latin America are widespread.Some of them are transoceanic and occur also in palaeotropical regions, but the majority are purely neo- tropical.Wide tropical, transoceanic species include Acanthocoleus aberrans ( =Dicranolejeunea aber- rans), Acrolejeunea emergens, Brachiolejeunea phyllorhiza (=Dicranolejeunea phyllorhiza) (Fig. 1), Caudalejeunea lehmanniana, Frullanoides tristis (Fig. 2), Lopholejeuneasubfusca and L. muelleriana, Mastigolejeunea auriculata, Odontolejeunea lunu- lata, Schiffneriolejeunea polycarpa (Fig. 3) and Stic- tolejeunea balfourii (Fig. 4).Prior to recent mono- graphic work, all of them were known from the various continents under different names except for Stictolejeunea balfourii, which was newly discov- ered in tropical America in 1981 (Gradstein 1985a).
This interesting species grows on roots etc. (occasionally epiphyllous) close to the ground in the understory of the moist primary rainforest, usually very sheltered and in very humid environments(e.g., near streamlets).I would predict therefore, that fur- ther collections of S. balfourii will turn up when careful searching is done in the habitats where it occurs.
Possible explanations of the ranges usually focus on step-by-step overland dispersal prior to the sepa- ration of the land masses in the late Mesozoic, or on long-range dispersal.Usually arguments pro and contra can be given for each of the two explanations and the question as to which of the two causes is responsible usually cannot be answered with cer- tainty (although for genera continental drift is often taken as the explanation and for species long-range dispersal (except for very ancient species)).
In the case of the transoceanic species of the Ptychanthoideae, the following data are relevant (list not exhaustive): 1.All transoceanic species have bisexual spores.

This fact lends
support to the long-distance dis- persal hypothesis.
3. The occurrence of fossil Stictolejeunea cf.squa- mata in Dominican amber (Gradstein msc.) indi- cates that this species is possibly more than 20 mil- lion years old.
Other ptychanthoid species very similar to present-day species have been found in Baltic amber, aged 32 million years (Grolle 1987).
The available evidence indicates that speciation in Ptychanthoideaeand other liverworts may have been slow in the last 32 million years and that some species may be millionsof years old.Whether these old species already existed at the time of the sepa- ration of the landmassesin the late Mesozoic cannot be concluded on the basis of this evidence, however.securifolia, Brachiolejeunea laxifolia, Dicranolejeunea axillaris, Frullanoides densifolia and Marchesinia brachiata (all "endemic" to Latin America); Brachiolejeunea phyllorhiza and Sticto- lejeunea balfourii (transoceanic).In the endemic Latin American species drought resistance of spores and sporelings varied from less than one day (a few hours?) in Blepharolejeunea incongrua and B. se- curifolia, a few days (less than five) in Brachiolejeunea laxifolia to 2(-3) weeks in Dicranolejeunea ax- illaris, Frullanoides densifolia and Marchesinia brachiata.These data indicate a poor dispersibility in the two species of Blepharolejeunea and in Bra- chiolejeunea laxifolia, and a moderately good ca- pacity for dispersal in the three other neotropical species tested.Excellent spore and sporeling via- bility of up to two months was found in the Afro- American Brachiolejeunea phyllorhiza (Fig. 1) and this supports the hypothesis that this species might have attained its transoceanic range via long-range air dispersal.In the pantropical Stictolejeunea bal- fourii (Fig. 4), however, drought and frost resistance is very poor (less than a day, possibly less than a few hours) and this would preclude the effectiveness of long-range dispersal in this species.As the species grows in very sheltered locations in dense understories ofnatural,primary forests (see above), where dispersal can hardly be very effective, it may be argued that this species attained its vast range via step-by-step dispersal over ancient land connections rather than via long-range dispersal.Such a reason- ing would indicate that the species is at least 90 million years old.
5. A basic problem in the biogeographyof trans- oceanic species is the question whether such species are indeed "good" biological species.Disjunct pop- ulations may be morphologically and anatomically identical, yet different at the genetic and chemical level.Using electrophoretic analysis of isoenzymes, Odrzykoski (1987) demonstrated the existence in the widespread Conocephalum conicum of five dif- ferent genetic strains which can be interpreted as sibling species.Electrophoresis and other genetic and chemical techniques can be expected to become more widely applied in bryology in future years and this may lead to the discovery of sibling species in transoceanic ptychanthoids, especially among those with poor dispersal capacities.
The few data presented here are meant to illus- trate the kind of (scanty) evidence available for bio- geographic interpretations in Lejeuneaceae.Some Mizutani and Gradstein are found only in the tribe Ptychantheae (van Slageren 1985) and are lacking in the Brachiolejeuneae, which have nodulose-type capsules as in members of the subfamily Lejeuneoideae.Schuster {in Longton & Schuster 1983) esti- mated that about 85% of the species of Ptychanthoideae are dioicous and considered the high rate of unisexuality a character of the subfamily.How- ever, among the 59 Latin American species cur- rently recognised only 19 species (ca.30%) are strict- ly dioicous and the remaining species are monoicous or polyoicous.In 33 Australasian Ptychanthoideae probably only 6 species (18%) are strictly dioicous (Thiers & Gradstein, in press).Polyoicous species, which are made up of dioicous and monoicous pop- ulations, are fairly common in the Ptychanthoideae (e.g., in the genera Marchesinia, Frullanoides and Mastigolejeunea) and this phenomenon may be a reason why estimates of the percentage unisexuality in the species of Ptychanthoideae have been high in the past.The new figures indicate that data on sex distribution from the literature are often unre-liableand that Ptychanthoideae and Lejeuneoideae probably do not differ in the percentages of mon- oicous (including polyoicous) and dioicous species.[VOL. 90teris and Frullanoides, which are represented in the Old World by only one species each.Moreover, Latin America has 5 endemic genera (Dicranolejeunea, Neurolejeunea, Blepharolejeunea, Lindigianthus, Verdoornianthus) whereas in the Old World there are 4 (Cephalolejeunea, Phaeolejeunea, Pty- chanthus and Trocholejeunea).
ranges extend to Mt. Itatiaia and other mountains in southern Brazil and to the highest peaks of the Guayana Highlands and the West Indies.Examples are Thysananthus pterobryoides, Marchesinia ro- busta, and two species of Blepharolejeunea: B. in- congrua and B. securifolia.Frullanoides densifolia and Brachiolejeunea laxifolia are the most wide- spread species in this category and they might also be included with the widespread neotropical ele- ment.
4. Van Zantenand Gradstein (in press) recently examined the feasibility of long-range dispersal, based on a testing of drought, frost and UV resis- tance of spores and sporelings as well as on other evidence, in 86 tropical liverwort species including the following Ptychanthoids: Blepharolejeunea in- congrua, B.
progress has clearly been made in recent times and the results may suggest directions into which future work should go. ). ).
nea of seasonal drought and salt spray (van Slageren