Current floristk and phytogeographk knowledge . of Mexican Bromeliaceae

A current floristic and phytogeographic knowledge of native Mexican Bromeliaceae is presented. There are 22 genera of Brorll eliaceae recorded from the country Iha! ¡nelude 326 species. The genus Ursulaea with 2 species is endemic to Mexico, wbíle Hechtia with 48 oC its 50 specíesbas its principal center of diversity in the country. 7illandsia ( 1 75 spp), Hechtia (48 spp) and Pitcairnia (46 spp) are tbe genera with tbe greatest number of species. We present a comparative análysisof Mexican Bromeliaceae with tbat of other American regions that buve recently published accounts Cor the Family, .particularly the Mesomerican area, Venezu¡:la, Ecuador,and tbeGuianas.Our results ledus to the cOI1e1usion tbat all tbese floras sbould be considered as distinct. We obse,rve a progressive decre¡¡¡se ofthe Simpson index value related wit� tbe remoteness of the Mexican area. A general análysisof tlrpspeCies numbers of Mexican bromeliad genera shows adistinct preference oftbe species forconiferousand oakfo,rests' ; folÍowed by t�opical caduci­ folious forests. There is also significan! r¡:presentation of tbe family'ifi' other vegetation types such as doud forests and tropical perennifolious forests. Generally Mel\ican Bromeliacea¡: speeies hav¡: scárceand sparse populationsandin many cases they inbabit diffs, bluffs and scaIJÍs in restrlcted areas,Col1cerning tbe .geogl1lphic distribulionof Méxican genera, 77.27 % are neolropical, 4.54% are South Am�rican and tbe remain4er ar¡; Mexican apd Central American. The genericendemism is very low (4.54 %), even ifwe extend the country limits to Megarll exicQsensu Rzedowsi ( 1 991 ) i t reaches only 13.63 %. The family endemism atspecific level reacbes 63.07 %: TherearPcnot avaiIábJe data about a spe­ cifie analysis of tbe conservation status of Mexican Bromeliaceae;bll! we can point()llt iba! a gr¡:llt númber of laxa are only known from tbe type eollection or at the most from the type locality. This can. perhaps béattributed in part to tbe faet that there is a lack of sufficient collections;however, we suppose tbat se\'eral species are surely end<'lngered.

with specíes numbl:}rssurpassing 2dO().'!phe members Oí the .famUy .are generally con §picu ous and-easily distinguished from other mOnO cotyledons by theiJ,-water absorbing peltate scales and their polystichous, most1y rosulate leaves with a broad sheathing base.The family ís enderriic to America, with exception of Pitcairnia feliciana (A.Chev.)Harrns & Mildbr.which is native lo West Africa (Dahlgren et al. 1985  Mexico has the second most richest flora in the Americas, and in the monocots, the Bromeliaceae is fourth in species number after Poaceae, Orchidaceae and Cyperaceae.The Bromeliaceae are an important ecological com ponent in Mexico's natural habitats and vegeta tíon types.Furthennore, several species are eco nomicalIy important, and others have local tra ditional and domestic uses. In these brief notes, we attempt to summa rize the present f10ristic and ecological knowl edge of Mexican Bromeliaceae.Non integrative work on revison of the family for Mexico has been made recently, notwithstanding, partíal works are known (Breckenridge 1991, Burt Utley & Utley 1987, Gardner 1982, 1986, Kiff 1991, Matuda 1952, McVaugh 1989, Smith & Downs 1974, 1977, 1979).Over time nurnerous changes in the delimitation of genera and species have been made (Srnith & Kress 1989, 1990, Varadarajan & Gilmartin 1988a, 1988b, Spencer & Smith 1993, Read & Baensch 1994, Utley & Burt-Utley 1994, Grant 1995a, 1995b), and the taxonorny and nomenclatural situation of the members of the farnily is at present quite different.
There are 22 genera of Bromeliaceae record ed from Mexico, that include 326 species and 27 varieties and/or subspecies (= 353 taxa) (Espejo & López-Ferrari 1994) (Table 1).The genera and species numbers are summarized in Table 2.The subfamily best represented at the generic level is Bromelioideae, with 13 of the 37 genera that comprise it.Second is the TilIandsioideae, with five of its seven genera, and finally the Pitcaimioideae, with four of its 17 genera.The subfamily with the greatest number of species is Tillandsíoideae, with 203, but the highest percentage of endemism at the species level is in the Pitcaimioideae (81.4 %).
The States with the greatest number of genera are Chiapas, Oaxaca, Veracruz and Jalisco;  For fue case ofVenezuela, we use the check list of the Bromeliaceae published by Holst (1994), which comprises 37 genera (modified in generic delimitations by the authors) and 361 species (Table 7).The index obtained was 8.92 %.
For Ecuador we use the data aported by Luther (1989) that we present in Table 8.The index obtained was 6.15 %.
Finally, the infonnation about the Guianas (Table 9), was obtained from Boggan et al      We have registered from Mexico 15 of the 21 species that comprise this genus, two of which are endemic to the country.(Table 2, appendix 1).The genus is taxonomically complex because of the presence of perfect and/or dimor phic and functionally dioecious flowers, a con dition that has caused taxonomic and nomen clatural problems, generating ample synonymy and problems in species delimitation.A revision of the genus is in prepartion (Palací inéd.).
The plants are epiphytic in tropical and tem perate forests and rarely in savannahs (Table 3), between 25 and 2700 m.

Chevaliera Gaudich. ex Beer
Only one species with two varieties of the 23 included in the genus occurs in Mexico.Chevaliera magdalenae André is terrestrial and known from tropical perennifolious forests in Chiapas, Oaxaca and Veracruz in Mexico, and south to Venezuela and Ecuador, between 50 and 640 m.The leaves of Ch. magdalena e are used for the extraction of fibers for the elabora tion of rope.The species has the local name of "Pita" or "Pita floja".
Fosterella L. B. Sm.This genus is represented in Mexico by the single species F. micrantlza (Líndl.)L. B. Sm.It is a terrestrial plant that inhabits tropical peren nifolious, tropical subperennifolious or cloud forests in the states of Jalisco, Guerrero, Oaxaca, Veracruz and Chiapas in Mexico, and in Guatemala and El Salvador in Central America.The species occurs between 200 and 1200 m.

Greigia Regel
This genus is mainly South American in dis tribution, with only six species present in the mesoamerican area.The saxicolous G. juareziana L. B. Sm. and G. vanlzyningii L. B. Sm. are endemic to Mexico (Table 2, appendix  1).The Mexican species inhabit oak and conif erous forests (Table 3) in Chiapas, Oaxaca and Veracruz between 2100 and 2700 m.The plants of Greigia are easily recognized by carrying their flowers in flattened heads deeply disposed in the axils of the leaves, so their presence is hardly conspicuous.

Guzmania Ruíz & Pavo
The genus includes 150 species.Of them G. nicaraguensis Mez & C. F. Baker and G. lin guiata (L.) Mez are epiphytic species that inhabit tropical perennifolious and cloud forests in the states of Chiapas and Oaxaca (Table 3).The species grow at altitudes between sea-Ievel and 1800 m.As with Greigia, this genus is mainly South American, and the Mexican species represent the northern limit of the generic distribution.
The unappendaged and connate petals clear ly distinguish Guzmania from other genera of the Mexican Tillandsioideae.

Hechtia Klotzsch
Heclztia is the largest genus in the country after Tillandsia, and moreover, has its principal center of diversity in Mexico. 96 % (48) of its species occur in the country, and 91.5 % (43) of them are endemic (Table 2, appendix 1).Using the Megamexico concept proposed by Rzedowski (1991) the level of endemism reach es 100%.The taxonorny of the genus is not yet clearly understood and a revision is badly need ed.Hechtia species are dioicous and this condi tion, in addition to scarce and/or incomplete collections, has generated many taxonomic and nomenclatural••problems.
The species of Hechtia are terrestrial or saxi colous in habit, living mostly in cliffs, bluffs, and precipitous walls in diverse vegetation types, though they prefer tropical caducifolious forests, and xerophilous sc rubs (Table 3).Their altitudi nal range varies from sea-level to 2800 m.
Most species of Hechtia are easily distin guished by their rosettes of spinose-serrate Ieaves in combination with their unisexual flowers disposed in separate plants.3) at an altitudinal range of 800-1800 m.The filaments are basally connate forming a tube which is adnate to the unappendaged petals.In addition, the pollen dispersed in tetrads making this genus unmistakable.

Macrochordion De Vriese
Only one of the ten species comprising this genus occurs in Mexico.M. bromeliifolia (Rudge) Beer is found in the southeastern state of Quintana Roo, and inhabits tropical sub perennifolious forests (Table 3) near sea-leve!.
It is an epiphytic plant characterized by the presence of yellow-greenish petals that turn blackish after the anthesis.

Pepinia Brongn. ex André
Pepinia is represented in Mexico by P. punicea (Scheidw.)Brongn.ex André and P. amblyosperma (L.B. Sm.) G. S. Varad; & Gilmartin.The former, known only from Chiapas and Tabasco, is a terrestrialplant that grows abunda n tly on river banks in tropical perennifolious and subperennifolious forests, while the latter is endemic (Table 2,appendix 1) to a small region that includes part of the states of San Luis Potosí, Puebla and Veracruz.It is also a terrestrial plant growing in cloud forests (Table 3).The altitudinal range of the species varíes between sea-level and 1000 m, Pepinia had been long-considered a subgenus of Pitcaimia, but recently received generic status (Varadarajan & Gílmartin 1988a, 1988b).Pepinia is differentiated from Pitcaimia by seed and leaf characteristics.The former have winged seeds and monomorphic leaves while Pitcairnia has biappendiculated seeds and dimorphic or trimorphic leaves.
Pitcaírnía is the third best represented genus in Mexico, with 46 of its 266 recognized species growing in the country.The specific endemism reaches 76 % and it is among the highest in the family (Table 2, appendix 1).Most of the species are saxicolous and/or ter restríal and a few are epiphytes.The species grow in diverse vegetation types but mainly in oak and coniferous forests (Table 3), between 100 and 2900 m.
This is an interesting and variable genus that needs the attention o t taxonomists to resolve the numerous problems ofinter and intraspecific delimitation in several Mexican species groups.Thé bright1ycoloured and conspicuous inflores cences and flowers of many species of the genus, make it attractive as an ornamental resource.
Platyaechmea (Baker) L. B. Sm. & W. J. Kress Eighteen species comprise this small genus recently segregated from Aechmea.Platyachmea is distinguished from other mem bers of the "Aechmea complex" by their decur rent floral bracts that form pouches around the flowers.Grant (1994) points out that the correct name of Platyaechmea should be Hoplophytum but does not make the necessary combinations because he questions the merit of the genus.3).
The clearly pedicellate flowers distinguish this genus from the other segregate genera of the "Aechmea complex" in Mexico, which have sessíle flowers.
Represented in Mexico only by Pothuava nudicaulis (L.) Regel, an epiphytic species that grows from sea level to 1140 m, in tropical perennifolious to tropical subpernennifolious forests, in the states of Chiapas, Puebla and Veracruz.
The sol e species of Pothuava in Mexico, is distinguished from other genera segregated from Aechmea by Íts simple, dense and cylin drical inflorescence, its small yellow flowers with free sepals and very small or absent floral bracts.3) between 700 and 2000 m.
Racinaea was recently segregated from Tillandsia (Spencer & Smith 1993).The set of characters that distinguishes the genus from other tillandsioid genera inelude its distichously arranged, inconspicuous flowers, asymmetric sepals that are broadest towards the apex, and free or nearly so, stamens and pistil that are ineluded within the corolla, and a short and stout style.2, appendix 1).
Tillandsia is known from almost all vegeta tion types present in Mexico but it is most abun dant in tropical caducifolious, oak and conifer ous forests (Table 3).Their representatives are almost exclusively epiphytes, and grow from sea-Ievel to upper 3000 m.
There are some groups of species in the genus with problems of taxonomic delimitation in need of carefull revision.In her systematic study of Tillandsia subgenus Tillandsia, Gardner (1982) suggests that the genus should be reclas sified in accordance with a more thorough study of living material.In 1986, Gardner proposed the subdivision of Tillandsia into 5 preliminary taxonomic "groups" circumscribed more natu rally, based chiefly on floral characters.Some species of Til landsia are used locally for food, medicine or ritual purposes, and many others as omamentals.Some of the common popular names of the Tillandsia species are: "Gallitos", "Hen o ", "Paxtle", "Tecolumate", "Tecolomé" .
Both species grow as epiphytes andlor saxi colous plants in tropical subcaducifolious forests (Table 3) dominated by Brosimum, between 500-600 m.Ursulaea species are, with sorne Tilla ndsias, among the most beautiful and spectacular members • of the family in Mexico.

COMMENTS
InTable 3 thespecies numbers ofMexican bromeliad .genera are presented by vegetation type (sensu Rzedowski 1978, appendix 2).A general analysis of the data shows a distinct preference of the species for coniferous and oak forests, followed by tropical caducifolious forests.There is al so significant representation of the family in other vegetatíon types such as cIoud forests and tropical perennifolious forests.
Generally Mexican Bromeliaceae species have scarce and sparse populations and in rnany casesthey inhabit cliffs, bIuffs and scarps in restricted areas.However, there are sorne exceptions, particularly in the c10ud forests where the brome liad s are an importapt compo nent of the epiphytic stratumin additíon to fam iliessuchas orchids.a roids and ferl1s.To date we do not have a specificanalysis of thecbn servation Status of Mexican.Bromeliaceae, ?but we Can point ' ollt that agreat number oftaxa are onIy kQown from the type cüUection Or at the mostJrom the type locality.This can perhaps be attributed in part to thefact thaUhere is alack ofsufficient collections; however, we suppose that several species are surely endangered.One additional point to bear in mind here is the high percentage of specificendemism(63.07 %) pre-.sented by the family in Mexico ( Megamexico sensuRzedowsi(1991)it reaches only13.6$%.Many ofthecomments expressed in this paper are based on the study of speci mens deposited in various herbaria.In general, we observed a poor representation, both in number and in quality, of bromeliads in the Mexican collections, especíally evident in gen era such as Guzmania, Greigia, Androlepis, Ursulaea, Hechtia, and Pitcairnia.

ACKNOWLEDGMENTS
We thank Jerzy Rzedowski, Graciela Calderón de Rzedowski, Walter Till, Werner Rauh, Jason R. Grant, and Emily Wood for their critical revision and helpful suggestions on the manuscript.We also express our gratitude to the curators of the herbaria AA, ClIDIR, ENCB, OH, lEB, MEXU, MICH, UAMIZ, and XAL for the facilities given and their kind assistance.Thís work was partially supported by the Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO-P015).

TABLE I
NlImber of genera and species of Bromeliaceae preselll in Mexico and percentages with respect 10 the world total.Number 01 Bromeliaceae species present in the diffe ren tvegetation types 01 Mexico (sensu Rzedowski. 1978).
p.330, Smith & Downs 1974 p. 57).The gréat majority of the taxa have a tropical or subtropical distribution and are mostly central and southamerican.

Fig
Fig. l.Number of speciesl 1000 km2 by state.

A
brief account of each of the genera found in Mexico follows.Data are based on seven years of field work and library and herbarium study.Aechmea Ruíz & Pavo This is a genus with 114 species, of which only two occur in Mexico, A. bracteata (Sw.)Griseb.with two varieties and A. matudae L. B.

Sm .
Both species inhabit rocks or are epiphytic in tropical perennifolious, tropical subcaducifo lious or tropical caducifolious forests, from sea level to 1000 (-1400 m). A. bracteata grows along both slopes of the country whereas A. matudae is known only from the Pacific slope, in Chiapas and Guatemala.

TABLE2
NlImber of species by genera and subfami/y.In the last column the endemic species lo Mexico are shown, wi/h the percentages, with respect /O the total present in the countT}: , Funk & Kelloff, 1997, with minor generic modifications by the authors.
B.chiapens' ts isendemic, toChiapas he only species pt'e/lent in Mexico of the eightjn the genus, 1/1A.cpmosus (L.)Merr., the pineapple or "Piña".ltis a higlily variable' plant with many foons and cultivars that is widely cultivated in the southeast of the country,main ly in the states of Veracruz, Oaxaca,•¡tind ChiapaS.The fruit is, ,pighly,ppzed.In sorne places•iti�j.t)aturali�d.' occur on the Pacificslope of the country from' Sinaloa toChiapas'andextend to El Salvador and Nicaragua in Central America.,.AH the Mexican species of Billbergia are epiphytic ,or rarely, terrestrial or' saxicolous, ocurring mostIy in tropical perennifolious or tropicalcaducif olious forests, rarely in oak�pine or; ,tborn forests, from nearsea level to 1400 m. , !mexicana

Table 2 )
, It is important tomention that many species are endemicnot onIy at the coU:ntry level but at• the state leve1 (appendix 1).• génera,.77.27%are neo tropical, 4.54% are Soúth American and the remainder are Mexican anel Central American (Table4).The genedc enderrtism is very low (4.54 %), eYeR if• w, e extendthe country limits to Geographic distributiOlí oI the Mexican genera 01 Br(¡me/iaceae.inth e last columnthe number 01 genera present in eath , distribu¡ion type and the perctmtage 01 the tota/ Mexican íaxa that it represents are shown,

TABLE 5
Number of genera and species by state, and the percentge of each wíth respecI lo the national total.

TABLE 6
Comparative species number 01 Mexican and Mesoamerican Bromeliaceae.

TABLE 7
Comparative species number of Mexican and Ven ezuelan Bromeliaceae.

TABLE 8
Comparative species number oi Mexican and Ecuadorian Bromeliaceae.