Distribution of Anthurium in Panama
Panama represents the richest area for Araceae in North America. The
species diversity of Anthurium that really begins in Costa Rica
to the north, increases considerably as one moves southward to Panama and
especially to Colombia. Costa Rica has over 80 of the total 219 species
recognized for Mexico and Central America, but there are almost twice that
many species in Panama. In addition, the discovery rate of new species
Table 1. Distribution of Panamanian Anthurium.
|From Mexico||From Middle America||From Costa Rica||From Panama|
|to Brazil||2||To Brazil, Peru
|3||to Colombia||11||to Venezuela||1|
|to West Indies
and South America
|1||to Venezuela||1||to Panama||23||to Colombia||11|
|to Panama||3||to Ecuador||5||Endemic||88|
in Panama is also much higher than in Costa Rica. I estimate that the present revision of Panamanian Anthurium represents a maximum of 95% of the species of Anthurium inhabiting the country. A number of suspected new species have already been collected but are inadequately known and are not included here. Relatively little of the Atlantic slope west of the Canal Zone has been investigated in detail, and little adequate botanizing has taken place in large sections of eastern Panama where species diversity is expected to be highest. As an example, a single expedition to one small area of the Serrania del Sapo near the Pacific coast turned up four unusual new species. Species richness in Panama is greatest at middle elevations along both sides of the Continental Divide and in the isolated mountain ranges in southeastern Daricn near the Colombian border, notably the Serrania de Pirre and the Serrania del Sapo. Although the mountains in the Azuero Península show considerable amounts of tropical wet and premontane rain forest (known to be the life zones of greatest species diversity in Anthurium), the dry season there is too severe to support many epiphytes. Natives of the region report that it generally does not rain at all during the dry season. During an expedition there, a six hour walk from Jobero Los Sanios Province) to the headwaters of the Río Pedregal yielded few aroids. A comparable trek through similar parts of the Continental Divide would have yielded scores of species of Anthurium.
Although little of the Serrania de Canasas has yet been investigated, it also appears to be less rich in species than the Continental Divide. While little is known of the rainfall in this area, it also lies to some extent in the rain shadow of the Continental Divide, which may create situations of prolonged drought in the dry season from December to May. As a means of evaluating the phytogeographic characteristics of Anthurium in Panama, a study was made to determine the geographical affinities of the Panamanian Anthurium flora with that of adjacent areas and to determine areas of local endemism that occur within Panama. The results are summarized in Table 1.
Perhaps the most striking feature of the distribution of Anthurium is the restricted geographical range of most species. For example, only two taxa are truly Pan-American in their distribution, namely A. gracile (Rudge) Lindl. and A. scandens (Aubl.) Engl. ssp. scandens, ranging from Mexico to Brazil. Nine additional taxa range less widely but extend from Middle America (Guatemala to Costa Rica) to at least northern South America (excluding Colombia). These are A. clavigerum Poepp., A. cuspidatum Mast., A. interruptum Sodiro, A. kunthii Poepp., A. ravenii Croat & Baker, A. scandens ssp. pusilium Sheffer, A. trinerve Miq., A. trisectum Sodiro, and A. williamsii K. Krause. One species, A. cubense Engl., has a circum-Caribbean distribution occurring in Cuba, Central America, and northern South America. Surprisingly few species are strictly Central American. Aside from the 26 species shared by Panama and Costa Rica, only five Panamanian species range further north: A. acutangulum Engl. (to Honduras), A. ramonense Engl. ex K. Krause (to Guatemala), A. flexile Schott, A. salviniae HemsL, and A. pentaphyllum var. bombacifolium (Schott) Madison (to Mexico). Only two additional species, A. bakeri Hook. f. and A. friedrichsthalii Schott, are principally Central American, ranging from Guatemala to Colombia. The 26 species shared by Costa Rica and Panama are A. acutangulum Engl., A. acutifolium Engl., A. angustispadix Croat & Baker, A. caperatum Croat & Baker, A. carnosum Croat & Baker, A. concinnatum Schott, A. consobrinumSchott, A. cotobrusii Croat & Baker, A. cuneatissimum (Engl.) Croat, A. davidsoniae Standl., A. fatoense K. Krause, A. hacumense Engl., A. hoffmannii Schott, A. ochranthum C. Koch, A. pallens Schott, A. pittieri Engl., A. pluricostatum Croat & Baker, A. purpureospathum Croat, A. ranchoanum Engl., A. seibertii Croat & Baker, A. spathiphyllum N. E. Brown, A. standleyi Croat & Baker, A. tilaranense Standl., A. tonduzii Engl., A. validifolium K. Krause, and A. wendlingeri G. M. Barroso.
The Pacific coast Anthurium flora of both Colombia and Ecuador is considerably related to species from both Panama and Costa Rica, and this affinity is likely to be bolstered as more intensive collecting occurs, especially in the Department ofChoco in northern Colombia. There are ten species that range from Costa Rica to Colombia, namely A. brownii Mast., A. formosum Schott, A. lancifolium Schott, A. lentii Croat & Baker, A. michelii Guillaumin,A. microspadix Schott, A. obtusilobum Schott, A. paludosum Engl., A. panduriforme Schott, and A. watermaliense Hon. ex L. H. Bailey. Eleven additional species are already known from Panama to Colombia, namely A. alticola Croat, A. cineraceumCroat, A. concolor K. Krause, A. crystallinum, Linden & Andre, A. dressleri Croat, A. erythro-stachyum Croat, A. fragrantissimum Croat, A. garagaranum Standl., A. malianum Croat, A. myosuroides (H.B.K.) Endl., and A. vallenseCroat. One species, A. fendleri Schott, ranges from Panama to Colombia and Venezuela.
Of the 148 species of Anthurium in Panama, 82 (or 55%) are now considered endemic. This is very high compared with the average rate of endemism for other taxa in Panama. For example, only 7% of all species in the "Flora of Barro Colorado Island" (Croat, 1978) were endemic to Panama. The figure was somewhat higher (12%) for epiphytic herbs even though this group also contained many species of ferns with easily dispersed wind borne spores. Fruits of Anthurium are much less likely to be widely dispersed. Most Anthurium species occur in the understory of dense forests and their fleshy, colorful fruits are ideally suited for bird dispersal. Moreover, the majority of species are probably dispersed by forest dwelling birds rather than by migratory birds or birds living in clearings or along forest margins. Forest bird species are much more likely to be territorial or otherwise restricted in their movements. This may help to explain why there are so many apparent local endemic species of Anthurium. Anthurium appears to have an even higher rate of endemism than the other genera of Araceae. For example in Syngonium (Croat, 1982) only two of the 13 Panamanian species (ca. 15%) are endemic, and in Monstera
(Madison, 1977) only one of the 12 Panamanian species is endemic (ca. 8% of the genus).
Perhaps even more surprising than the high rate of endemism in Panama is the fact that there seem to be several areas of endemism even within Panama (Table 2). Not surprisingly most of these areas are associated with hilltops, but other apparent areas of endemism are not strongly related to mountaintop isolation.
Of the 82 species endemic to Panama, 26 are restricted to western Panama (i.e., west of the former Canal Zone) and 30 are restricted to the area east of the Canal Zone. Only three of the endemic species are found to be relatively widespread (or at least occurring in both Chiriquí and in Darien Provinces). These are A. hutchisonii Croat, A. sanctifidense Croat, and A. antonioanum Croat. Three additional species are known from central Panama only and occur on both sides of the Canal Zone: A. cerrocampanense Croat, A. melastomatis Croat, and A. roseospadix Croat. Five species range from Veraguas to Darien, namely A. bicollectivum Croat, A. colonense Croat, A. cucullispathum Croat, A. curvispadix Croat, and A. luteynii Croat. One species, A. papillilaminum Croat, ranges from Colón (west of the Canal Zone) to Darien.
Of the western Panama endemics, 14 taxa are restricted to Chiriquí Province, which has higher average elevation than the rest of western Panama. Most have been discovered in forest along the Continental Divide such as on Cerro Colorado or on the Pacific slope along the Fortuna Dam Road. The Chiriquí endemics include A. chiriquense Standl., A. circinatum Croat, A. coloradense Croat, A. fusiforme Croat, A. globosum Croat,A. gracililaminum Croat, A. gracilispadix Croat, A. lancifolium var. albifructum Croat,A. longistipitatum Croat, A. madisonianum Croat, A. pauciflorum Croat, A. protensum ssp. arcuatum Croat, A. pseudospectabile Croat, and A. validifolium K. Krause. Almost no exploration for Anthurium has taken place on the much wetter Caribbean slopes though three taxa are newly described here from the Atlantic slope in Bocas del Toro Province. These are A. hammelii Croat, A. teribense Croat, and A. wedelianum Croat ssp. wedelianum.
None of the species from Chiriquí, nor any of those from Veraguas or Code to be mentioned next, would appear to be particularly isolated on mountaintops, and the Chiriquí region is connected to Veraguas and Code by a continuous belt of forest along the Continental Divide. Yet despite the relatively close proximity of the rich Chiriquí sites mentioned (e.g., Cerro Colorado and the Fortuna Dam area), only two species, A. hornitense Croat and A. intense Croat are common to these provinces. How much this is related to real differences and how much to collecting deficiencies is not known.
Table 3. Distribution of Anthurium within Panama
|From Chiriquí||From Veraguas||From Coclé||From Cólon||From Panama||From Darien|
|to Darien||3||to Darien||5||to Darien||1||to Darien||2||to||1||Endemic||16|
|to Veraguas||1||to Panama and Cólon||3||to San Blas||1||to San Blas and Panama||2||Endemic||12||(Serrania de Pirre||8)|
|to Coclé||3||to Coclé||4||to Colón||1||Endemic||1||(Cerro Jefe||8)||(Serrania del Sapo||3)|
|to Bocas del Toro||3||Endemic||2||to Panama||1||(Canasas||3)||(Cerro Tacarcuna||4)|
Three species, A. caloveboranum Croat, A. dichrophyllumCroat, and A. kallunkiae Croat, are restricted to Veraguas Province (most having been collected on Cerro Tute or along the trail from Santa Fe to Calovcbora), and seven taxa, A. brevispadix Croat, A. crassilaminumCroat, A. crassiradix var. purpureospadix Croat, A. curvilaminum Croat, A. hebetatum Croat, A. oxystachyum Croat, and A. sytsmae Croat are restricted to Code (mostly collected along the Continental Divide north of El Copé). Three additional taxa are shared by the two provinces: A. panamense Croat, A. rupicola Croat, and A. wedelianum ssp. viridispadix Croat. The assumed endemic localities in Veraguas and Code are likely to represent artifacts of collecting, as the areas between the two provinces have not been well collected. Nevertheless, some areas such as the El Valle vicinity further east in Code Province have been botanized for many years and have not turned up many of the species now known from El Copé. El Valle is about the same distance from El Copé as the latter is from Santa Fe.
In the eastern half of Panama there are four apparent centers of local endemism, namely the Cerro Jefe region, the Serrania de Canasas, the Serrania de Pirre, and the Serrania del Sapo. Only the first has been well collected, and it is perhaps the most surprising area of endemism as it is not really much isolated from the nearby collecting areas of the El Llano-Carti Road to the east and the Santa Rita Ridge Road to the northeast. Despite the fact that these three areas have many species in common there are still eight very distinct species that have been collected only on Cerro Jefe and in the immediate nearby regions. This is the most startling case of endemism I have encountered in Anthurium. The species found only in the vicinity of Cerro Jefe are A. cinereopetiolatum Croat, A. folsomianum Croat, A. gentryi Croat, A. jefense Croat, A. kamemotoanum Croat, A. sagawae Croat, A. supraglandulum Croat, and A. tysonii Croat.
The El Llano-Carti Road and the Santa Rita Ridge Road, both excellent collecting areas over the past decade, have turned up numerous interesting collections, sometimes shared with Cerro Jefe (A. crassiradix Croat) and, at least in the case of A. cerrocampanense Croat, also with Cerro Campana on the other side of the Canal Zone. Nevertheless these two roads share two species not known elsewhere: A. cartiense Croat and A. correae Croat. Another species, A. angustilobumCroat, is known only from the El Llano-Carti Road. Two other species from the El Llano-Carti Road have been collected considerably to the east on the Continental Divide in the Cordillera de San Bias at Cerro Habu, and it is expected that with better collecting in eastern Panama many of the species now restricted to central Panama will be found throughout the Central Cordillera.
The Serrania de Canasas, an isolated mountain range in southern Panama Province, remains largely unexplored, but I suspect it will prove to be relatively poor in species. This assumption could be wrong as it is based on studies made only of the lower slopes. The recent completion of the Pan-American Highway to Darien Province provides access to the northeast corner of the Serrania de Canasas and the relatively few collections from the area above Torti Arriba have already turned up three endemic species; other collections may prove to represent new species as well.
Relatively few species restricted to the eastern half of Panama occur both in the Canal Zone vicinity and also in Darien. Two species that are known to have this distribution are A. impolitum Croat and A. pendens Croat, although the latter may occur in Colombia.
Unlike the Cerro Jefe, El Llano-Carti, and Santa Rita Ridge areas, the mountain chains of southeastern Darien Province are isolated both from each other to some extent and certainly from the Central Cordillera. On my first visit there, after having collected extensively throughout much of the Central Cordillera, I was surprised to see no species I recognized. No less than seven species have proven to be endemic, namely A. cerropirrense Croat, A. crassitepalum Croat, A. niqueanum Croat, A. pirrense Croat, A. rurifructum Croat, A. subrotundum Croat, and A. terryae Standl. & L. 0. Wms.
The Serrania del Sapo, lying along the Pacific Ocean southwest of the Pirre chain, has scarcely been sampled. However, in two trips there Barry Hammel has collected three endemic species: A. barryi Croat, A. chromostachyum Croat, and A. sapense Croat; in addition, one species, A. redolens Croat, is known from the Serrania del Sapo and Serrania Canasas.
Darien Province has four additional endemic species that are not restricted to these two mountain chains. These are A. dukei Croat and A. rotundistigmatum Croat (both at least partially from lower elevations), A. tacarcunense Croat (from Cerro Tacarcuna in the Serrania del Darien, the end of the Central Cordillera that extends into Colombia), and A. foreroanum Croat (known from both Cerro Tacarcuna and Cerro Pirre).
Further field work on the Pirre and Sapo chains, both of which extend briefly into Colombia, will undoubtedly show that many of the species found occurring on them occur in Colombia as well. Nevertheless, it is unlikely that these species will prove to be widespread in lowland parts of the Choco Department.