Aliso: A Journal of Systematic and Floristic Botany Aliso: A Journal of Systematic and Floristic Botany The palms (Arecaceae) of Sonora, Mexico The palms (Arecaceae) of Sonora, Mexico

This publication is an account of the palms (Arecaceae) in the state of Sonora in northwestern Mexico. Six native palm species in three genera are recorded for Sonora: Brahea with four species, and Sabat and Washingtonia each with one species. Relationships and taxonomy within Brahea, especially B. elegans, remain unresolved. Brief botanical descriptions, taxonomic synopses, local names, identification keys, conservation status and recommendations, and distributional and ethno botanical information are provided for each species. Basionyms and types are cited. Distributions are documented with citations of nearly all herbarium specimens known to us from Sonora. Many palm populations in this arid and semiarid region are threatened by development and in some cases over exploitation. There is an urgent need for formal management and conservation action for local pop ulations, although as a whole none of these species in Sonora are rare or immediately threatened. presentan basionimias e infor macion sobre los tipos y sfnonimos. Distribucion con citas de casi todos los especfmenes de herbario de las Arecaceas de Sonora conocidos por nosotros es propocionada. Muchos de las poblaciones de palmas en este region anda y semi-arida son amenzadas por el desarollo y en algunos casos por Ia sobre-explotacion. Hay una necesidad urgente para el manejo formal y acci6n de conservaci6n para poblaciones locales; sin embargo en general ninguna de las especies en Sonora se considera espe cialmente rara o en peligro inmediato.

Writing from Europe in the late 18th century, more than a decade after suffering through the Jesuit expulsion, lgnaz Pfefferkorn (1949: 74) stated: "Many palm trees grow in the region near the sea, especially in the vicinity of Guaymas. Since these palms neither yield fruit nor attain the height which is reached by genuine palms, they seem to be either degenerate or false mem- Table I. Ecological distribution of palms in Sonora: Sonoran Desert (SD), tropical deciduous forest (TDF), tropical thornscrub (TIS), oak woodland (OAK), and pine-oak woodland or forest (PIN The purpose of this work is to provide information on the natural history, ethnobotany, horticulture, distributions, and location of principal collections of Sonoran palms, and to help clarify their taxonomy and nomenclature. Palms in northwestern Mexico are keystone species, and we trust that this information will aid in efforts to conserve them and their special habitats.

DISTRIBUTION, DIVERSITY, AND ECOLOGY
Three genera and six species of palms are native to Sonora: Brahea with four species, and Saba/ and Washingtonia each with one species (Table 1; Fig. 1). These are among the northernmost native palm genera in the Western Hemisphere. All are medium-to largesized fan palms in the tribe Corypheae of the subfamily Coryphoideae. In addition, the date palm (Phoenix dactylifera) is occasionally encountered in noncultivated habitats.
Washingtonia occurs naturally northward to Arizona and California, whereas Brahea and Washingtonia occur in both states of Baja California (Wiggins 1964;Turner et al. 1995). W ashingtonia robusta, restricted to a few riparian canyons at the southern edge of the Sonoran Desert, appears to be relictual in Sonora. It occurs naturally otherwise only in Baja California Sur. Saba/ uresana scarcely extends beyond the confines of Sonora, whereas Brahea elegans is endemic to Sonora. Brahea aculeata, B. dulcis and B. nitida range southward in Mexico and B . nitida extends to Guatemala.
Palm species represent less than 2% of the tree flora of Sonora, which includes more than 275 species in a vascular flora of perhaps 5000 species (Felger and Johnson 1995;Felger and Wilson 1995). Palms in Sonora are distributed in a variety of habitats (Table 1). For discussion of Sonoran habitats see Brown (1982), Steinmann and Felger (1997), and Burquez et al. (in press). Four Sonoran species occur within the Sonoran Desert as mapped by Shreve (1951). Washingtonia robusta occurs only in riparian habitats within the Sonoran Desert, and is geographically and ecologically the most narrowly restricted palm species in the state. In northern Sonora, about 100 km south of the Arizona border, Brahea nitida occurs in riparian canyons at the uppermost edge of the Arizona Upland region of the Sonoran Desert at its ecotone with oak woodland. Four species occur in tropical deciduous forest and tropical thornscrub (Felger and Joyal 1998). Palms of nondesert habitats in Sonora commonly extend into the lower oak zones and sometimes even intermingle with pines in pine-oak woodland of eastern Sonora. Although some Sonoran populations are relatively widespread, most are highly localized and niche-specific.
Most of the inland groves contain only a single palm species, although in some places two or three species may occur together or in close proximity to each other. Where these palm species occur sympatrically, the maximum densities for each species are in somewhat different niches. Three species, Brahea elegans, Saba/ uresana, and W ashingtonia robusta, occur together in a number of the palm oases near the coast north of Guaymas in the Sierra El Aguaje and vicinity, e.g., Caii6n del N acapule (Felger 1999), Los Anegados, La Huerta (Ojo de Agua), and Caii6n Las Barajitas. Washingtonia robusta is the most narrowly restricted, with the fewest number of plants, and concentrated closest to water sources. Saba/ uresana occupies somewhat less restricted habitats and is more numerous, while B. elegans is the most widespread of the three and is truly abundant. Elsewhere in Sonora, Saba/ sometimes occurs together with B. aculeata or B. elegans.
Apparent adaptations to aridity and/or winter freezing among palms of southwestern North America include larger (thicker) trunks and larger leaves with tougher and more reflective, duller-colored leaf blades. The two truly Sonoran Desert species, Brahea armata S. Watson and Washingtonia filifera (Linden) H. Wendl., have exceptionally thick trunks and dull-colored leaves. Their congeners to the south have more slender trunks and thinner, greener leaf blades. Brahea aculeata of southeastern Sonora and Sinaloa is smaller in stature and has smaller, thinner leaves than B. elegans, its northern, desert-edge and desert-inhabiting relative. A similar trend is seen among Saba/ species in western Mexico (e.g., Zona 1990). These trends may also be intraspecific-the northernmost popula-,,. tions of Brahea elegans are larger and more robust than those farther south, and desert-inhabiting populations along the coast tend to have more glaucous leaves than those in the mountains of eastern Sonora.

PALMS AND PEOPLE IN SONORA
Palms are one of the most highly utilized plant families worldwide, especially in tropical regions. Sonora, at the edge of the tropics, is no exception. The most widely used part of Sonoran palms are the leaves which are or have been employed in weaving, thatching, and broom-making. The trunks have been used for construction, and the fruit and sometimes the palm heart for food (e.g., Rose 1899;Standley 1920;Gentry 1942Gentry , 1963Pfefferkorn 1949;Hinton 1959Hinton , 1969Di Peso and Matson 1965;Sobarzo 1966;Nentvig 1977;Pennington 1980;Felger and Moser 1985;Joyal 1996a). Although much traditional knowledge of palms in northwestern Mexico has been lost, considerable knowledge remains unrecorded as well as culturally robust (e.g., Joyal 1996a, b).
Sabat uresana, the most widespread Sonoran palm, is an important nontimber resource, and the most economically valuable of the six regional palm species. Although other palm species and a few palmlike monocots are mentioned in the literature, Sabal is the most commonly and consistently cited Sonoran palm in more than three centuries of historical references (Joyal 1996a).
The newly emerging, unexpanded palm leaf is called a cojoyo (this term is also used as a vulgar term for penis). Cojoyos, primarily of Sabat, are highly valued for weaving twilled and coiled baskets, mats, and other items, and people travel considerable distances to harvest them. Sabat is the only Sonoran palm employed in hat-making. The fully expanded leaves called pencas, especially those of Sabal, are widely used for broom-making. The leaves of Sabal and Brahea aculeata are extensively used for thatching. Brahea aculeata is also used to make mats by the Guarijfo as well as other local people. Strips of leaf blades, especially of Brahea aculeata and to a lesser degree, those of B. nitida, are woven into a coarse cordage or rope and used for such purposes as tethering animals (Felger and David Yetman, unpublished field notes for Guarijfo ethnobotany;Gentry 1942;Joyal 1996a).
Palm leaves, primarily Sabal, Brahea aculeata, and B. nitida, are traditionally harvested at the time of the full moon. The quality and durability is said to be compromised if the leaves are harvested at other times. However, harvesting does occur at other times, especially if for sale without regard for quality. Juvenile palms, called palma del suelo 'palm of-the ground,' are harvested for cojoyos for weaving mostly during the monsoon season. Leaves from mature palms, called palma del taco "fruiting palm" in the case of Sabat, are mostly harvested for thatch in the spring dry season.
In the desert region, especially near Ures, the trunks of Sabal have been used to build corrals and as crossbeams (vigas) for houses. Traditionally only the trunks of dead trees were used to make corrals, but in recent years living trees have been cut, contrary to the policy of certain local forestry offices. Farther east and southward in the mountains, palm logs are occasionally used in construction and as benches, and are also hollowed out to make planters. During the 19th century the trunks of Washingtonia robusta were used in Guaymas "as rafters for houses. It is said to be a durable wood." (Rose 1899: 255).
The blackish, sugary mesocarp of the ripe fruit of Sabat, locally called taco, is eaten fresh in northeastern and east-central Sonora but is considered unpalatable in the desert area near Ures. The fruits of Washingtonia are sweet and edible, and apparently were used for food by the Seri (Felger and Moser 1985). In northeastern Baja California, the Cocopa people pit-roasted the large seeds of Brahea armata (Felger and Amadeo Rea, unpubl. 1980). Some Brahea species, especially B. edulis H. Wendl. ex. S. Watson from Guadalupe Island off the Pacific coast of Baja California, have a sweet, datelike mesocarp. The fruits of certain Brahea were used for food in Sonora, but the information is fragmentary. For example, the fruits of B. aculeata are eaten by the Guarijfo (Felger and David Yetman, unpubl. 1997), and those of B. elegans are eaten in the Ures region (Joyal 1996a). However, especially in the case of the coastal palms north of Guaymas, the lack of ethnobotanical information is meaningless since indigenous people have not lived in the area for nearly one and one-half centuries and the information was not recorded (Felger and Moser 1985).
In the 17th century Nentvig (1672) reported the use of palm hearts (terminal buds) for food in northeastern Sonora. Gentry ( 1942Gentry ( , 1963 likewise reported that the Guarijfo ate palm heart (corazon), apparently of Sabal and perhaps Brahea aculeata, a practice that kills the plant. Palm hearts are apparently no longer harvested in Sonora.
The fibers that hang between the leaflets of Sabal uresana were used by the Mountain Pima to weave saddle blanke ts. Orioles, including hooded and streaked-back, make nests from these fibers. These nests are sometimes used as sponges. Sabat petioles are employed to make racks for aging cheeses, stirring sticks, and broom handles.
Writing from Populo in 1692, Adamo Gilg mentioned that the Seri wove, " . . . mats of palms and reeds" (Di Peso and Matson 1965: 55). Populo was a Jesuit mission for the Seri during the 17th and 18th centuries along the Rfo Sonora near Ures; the palm would have been Sabal uresana, which is common in the region. More than a century after the Seri no longer lived in places where palms occur (the coast north of Bahia San Carlos, northwest of Guaymas), the people still had knowledge of palms and their uses from that region (Felger and Moser 1985). Some hint of earlier palm use is found in the modem terms for any wooden box, he he zamij "palm wood," and the personal carrying box, hehe zamij an iqui ihacalca "box to put belongings in," which have long been made from other kinds of wood. Zamij is the generic term for any palm including the introduced date palm. Seri oral history of the mid-to late 20th century included two kinds of native palms: zamij cmaam "female palm," which most likely refers to Brahea elegans, and zamij ctam "male palm," which most likely refers to S. uresana and/or Washingtonia robusta. The fruit of zamij ctam was eaten. A hat to provide protection from the sun was woven from tender, inner palm leaves. This kind of hat was called zamij yeen haonam "palm-face hat." "Face" refers to the inner, or youngest leaf or cojoyo. Date palms, Phoenix dactylifera, brought to Sonora by the Jesuits during Spanish colonial times, have long been known to the Seri people. According to oral history, one Seri man planted dates at one or more camps south of Bahia Kino in the mid-19th century.

CONSERVATION AND MANAGEMENT
Three of the Sonoran palms are listed by the Mexican government on its most recent list of species needing protection (SEDESOL 1994). SEDESOL lists Brahea aculeata as "threatened, endemic," B. nitida as "endangered," and Sabal uresana as "rare, endemic." SEDESOL did not list B . dulcis, B. elegans, or Washingtonia robusta. The SEDESOL determinations apply to a species' status throughout Mexico.
Based on our field experiences in Sonora, we recommend the following IUCN 1997 Red List categories (Walter and Gillett 1998): Brahea elegans and Sabal uresana are endemic or nearly endemic in Sonora and most closely fit the IUCN criteria for Vulnerable (VU) status. The remaining four species largely fit the IUCN criteria for Lower Risk (LR), Near Threatened (NT) status in Sonora and Data Deficient (DD) in Mexico.
Both B. aculeata and S. uresana are still abundant in many places. Many of their populations are declining or extirpated due to overexploitation and habitat loss, primarily due to clearing of tropical deciduous forest habitat for buffelgrass (Pennisetum ciliare [L.] Link) pasture (Bt1rquez and Martinez-Yrizar 1997). In addition the oases and riparian canyons where palms occur are often heavily exploited for cattle gra2:ing, settlements, and recreation. Cattle eat seedlings of S. uresana and probably other species too, especially dur-ing spring drought if no other forage is available. Brahea dulcis and B. nitida, at least in Sonora, do not seem to be at risk, largely because they grow on inaccessible cliffs and in remote canyons. Individual groves or stands of B. elegans are vulnerable but countless thousands of them occur at higher elevations on remote, uninhabited mountains and on steep cliffs.
The palm canyons in the San Carlos-Bahia San Pedro region of central-coastal Sonora deserve vigorous management and protection. The more accessible, magnificent palm oases in the vicinity of Bahia San Carlos have been decimated by development, clearing of undergrowth, and removal of plants for landscaping (see S. uresana below). The Sabal grove, or Palmar, near the present Hotel Club Med, supported perhaps as many as 2000 adult palms in the 1960s and early 1970s. Today about 500 adult palms remain, but undergrowth vegetation has been destroyed and there is virtually no seedling survival. Unless there is a change to conservation management, these palm-dominated communities are essentially "living dead" sensu Janzen (1988). Other extensive palm groves, such as those in the canyons north of Bahfa San Carlos, on the old road to Bahia Algodones, and at the San Carlos golf course, have been annihilated during the past few decades. No vestige remains of their former existence apart from an occasional lone palm.
The magnificent palm oasis at Cafi6n del Nacapule, supporting all three genera, is being devastated by mining of ornamental rock, cattle grazing, and vandalism (Felger 1999). However, many intact palm oases remain in this region (Sierra El Aguaje, from the vicinity of Bahia San Carlos to Bahia San Pedro; see Johnston 1924;Schnabel 1962Schnabel , 1964Felger 1966). The most extensive palm groves in the region are at Cafi6n Las Barajitas (between San Carlos and Bahfa San Pedro), where all three genera are common.
Overharvesting has occurred at least since the 19th century (e.g., Gentry 1942). Rose (1899: 255) reported that "At Guaymas a few trees remain of the rare Neowashingtonia sonorae [= W. robusta], but most of them have been cut out." Practices which ameliorate nonsustainable use of palms in Sonora include limiting access to populations on privately controlled property, "sparing" (not cutting living trees in agricultural fields and pasture), and restricting harvest according to lunar cycles. Choice of palm size and leaf age, and controlling harvest times (e.g., season as well as lunar cycle) further regulate leaf harvest (Joyal 1"995, 1996b).
Throughout Sonora the dry dead leaves, or "skirts," of palms are often purposely burned because they harbor nests of aggressive paper wasps (Mischocyttarus and Polistes). Palms generally recover from burning, which may be beneficial in destroying insect pests, opening up oasis vegetation, and increasing palm seed germination (Hicks 1989). However, many thriving palm populations in Sonora occur in remote areas that are not burned by people, and in the case of Saba/ uresana statewide only about 10% of trunks show signs of fire.

THE SONORAN PALMS
The following treatment of the Sonoran palm species is based on our field experience, study of herbarium specimens, and the literature. We have studied palm specimens and photos, especially those of northwestern Mexico, from the following herbaria: ARIZ, ASU, BCMEX, BH, CAS/DS, DES, FI, GH, HBG, MEXU, MO, P, RSA, SD, UC, UCR, and US. These collections include nearly all known Sonoran palm specimens. Unless otherwise noted, we have seen all specimens cited. The first set of Felger's specimens is at ARIZ and the second at MEXU, with additional duplicates when available at BH, FTG, CAS, etc. The first set of Joyal's specimens is at ARIZ and the second at MEXU, with additional duplicates at BH, US, and FTG. Specimen localities are listed by the present-day municipio (mpio.; see Steinmann and Felger [ 1997] for a map of Sonoran municipios ).
In most instances heights of palms are visual estimates. Seed measurement for Brahea and Washingtonia include the thin and essentially inseparable endocarp. The thin endocarp of Saba/ uresana does separate and the seeds were thus measured without the endocarp. The following keys and brief descriptions are based on palms from Sonora and might not apply to plants in other regions.
KEY TO THE GENERA 1. Plants often branching from the base (suckering); leaves pinnate; dioecious; seeds more than twice as long as wide, conspicuously grooved ; date palm, c ultivated, rarely surviving at abandoned settlements or marginally naturalized . . Phoenix I' Plants single-trunked; leaves palmate (fan palms); flowers bisexual; seeds less than twice as long as wide, not grooved; native palms. 2. Petioles always entire, the leaves prominently costapalmate (petiole extending we ll into blade on the lower surface), the hastula narrowly triangular, more than twice as long as wide, firm, and glabrous, the margins entire, persiste nt; inflorescences shorter than, or sometimes as lo ng as the leaves ; seeds broader than long, depressed globose . only moderately so, the hastula broadly triangular to irregular, broader than wide to less than twice as long as wide, the margins papery to variously pubescent, not e ntire, ultimately deciduous; inflorescences often lo nger than the leaves; seeds ro unded to longer than broad . 3. Leaf blades often green above , silvery-blue glaucous beneath or to ugh and dull green or gray-green on both surfaces; sepals separate, entire; widespread . . . Brahea 3' Leaf blades shiny green on both surfaces; sepals united below, the lobes with ragged margins; in Sonora  (Quero 1992). Moore (1973) and Uhl and Dransfield (1987) consider Brahea and Erythea to be congeneric, although Quero (1989Quero ( , 1992 treats them as distinct genera. These taxa are in need of taxonomic study (Uhl and Dransfield 1987).
Brahea sensu stricto includes five species ranging from Central America to northern Mexico excluding the Baja California peninsula. These palms are reported as being restricted to limestone substrates (Bailey 1943;Quero 1992), although this is not the case in Sonora for B. dulcis and some populations of B. nitida. The two species in Sonora are distinctive and not closely related. Erythea S. Watson includes seven species (Quero 1992). Five of them are confined to northwestern Mexico, one occurs farther south in western Mexico, and another is in southern Mexico and Central America. They grow on soils derived from igneous rocks.
Erythea in Sonora is represented by a highly variable and taxonomically ill-defined complex of often isolated populations. Plants at the geographic and ecological extremes are quite distinctive but populations showing intermediate features are commonplace. A comprehensive study of Erythea is sorely needed but is outside the scope of this paper. We choose to treat the Sonoran taxa as two species within Brahea, while acknowledging that further research may result in a different arrangement and/or the circumscribing of new taxa.
Erythea was "one of the daughters of the Hesperides, daughters of the Evening or the West who, in Greek mythology, dwelt on an island on the western edge of the world and who guarded the golden apples there" (Bailey 1937: 85). Bailey suggested that Watson's choice of this poetic name indicated that Watson meant for Erythea edulis (H. Wendl. ex S. Watson) S. Watson, which is endemic to Guadalupe Island (about 500 km west of the then sparsely inhabited Pacific Coast of Baja California), to serve as the type species for the genus, and not E. armata, which he also transferred into the newly erected genus at that time. Bailey, however, never went so far as to designate E. edulis as the type species. KEY  Description.-Trunks mostly 2-9m tall, 12.7-25 em in diameter. Leaves often l0-30 in number, often 95-180 em long; petioles commonly about as long as the leaf blade, 39-116 em long, 0.7-1.9 em wide just below the blade, armed with mostly stout, often yellow, single and sometimes also double marginal teeth 1-6 mm long, often fewer and reduced apically, or sometimes young plants and smaller-leaved adult plants with the teeth greatly reduced or essentially absent; hastula small, hyaline; blades often 55-90 em long, 60-110 em wide, glaucous bluish-green, especially below and slightly greener above, often discoloring with darker blotches upon drying. Inflorescences about equal to, or longer than the leaves, the branches and rachillae sparsely to densely tomentose. Rachillae (3-)5-11 em long. Flowers white, very fragrant (at least in the late afternoon), the buds 1, 2, or 3 together, usually only l developing into a flower. Sepals 1 mm long, broadly triangular, greenish white. Petals 1 mm long. Petals, starninal ring, and anthers white. Ovary green, 3-lobed. Fresh fruits 25-30 mm maximum diameter, nearly round, the surfaces smooth, yellow-brown and somewhat mottled. Seeds 15.5-20.0 mm maximum diameter, rounded or nearly so. 2n = 36 (Read 1964  Distribution.-Valleys, hills, mountains, and canyon bottoms and slopes, the distribution decidedly patchy but the plants often locally abundant. Tropical decid~ uous forest and lower oak woodland, and sometimes extending into higher elevation zones in oak woodland and lower pine-oak woodland; Rio Mayo and Rio Fuerte drainages in the Municipio de Alamos, southeastern Sonora, ca. 320-1500 m. Populations slightly farther north along the Rio Mayo, in the vicinity of Los Bajios, in the Municipio de Quiriego may be B. aculeata. Likewise a sterile specimen from the vicinity of La Quema, in the Rio Yaqui drainage, in the Municipio de Yecora, appears to be B. aculeata. Also southwestern Chihuahua, Sinaloa, and Durango. Notes and horticulture.-This palm is readily grown from seed and is sometimes cultivated in southern Arizona. Plants more than 25 years old at the Arizona-Sonora Desert Museum west of Tucson have shown no signs of freeze damage. The precise northern limit for B. aculeata and its relationship to the southernmost B. elegans remains unresolved. Both in cultivation and in their natural habitats B. aculeata is a much smaller palm but with larger fruits and usually larger seeds. Grown side by side, these palms demonstrate clear differences in size and growth rates (Fig. 2).   Fig. 3.
Vernacular name.-Palma ceniza "ashy palm," used at Los Bajios by Guarijio men "for a palm that grows to the east up in the mountains," apparently this species.
Description.-Solitary palms, often to 5+ m tall, the trunk often 10+ em in diameter, the older leaves falling away. Leaves reaching ca. 125 em long, the petioles 52-80+ em long, usually entire apically and with some broad teeth basally often 1-1.5 mm long, glaucous, 14-25 mm wide near base, tapering to 8-15 mm just below the blade; hastula as wider or wider than long, to ca. 1.5 em long, thin, brown, scarious and fraying into fibers; blades often 65-85 em long, about as wide as long, shiny green above, glaucous-blue below, with deciduous, sordid, sparse tomentum on the segment midribs near the base of the blade on both surfaces, this tomentum and the hastula usually wearing away with age. Inflorescences arching, usually longer (sometimes twice as long) than the leaves, 4-times branched; flowering branches and rachillae crowded, purple-brown, often becoming cream-colored and very densely woolly-tomentose; branching angles acute. Rachillae catkinlike, floriferous to their bases, 4-10 em long, 2.2-3.0 mm in diameter. Flowers greenish white, spirally arranged, not paired or clustered (more or less equally spaced from one another), the buds longer than wide, the flower bases submerged in the woolly hairs of the rachillae. Sepals ca. 1 mm long, overlapping, short woolly (tomentose-canescent) on exposed surfaces, the margins scarious. Petals 2.3-2.4 mm long, glabrous except sometimes sparsely canescent with some small hairs basally, striate (longitudinal lines formed by prominent veins). Filaments slender from broadly expanded, thick, deltoid bases. Young fruits densely pubescent with short hairs. Fruits with a fleshy pericarp, smooth, purplish black when ripe, rounded, 10.5-12.5 mm in diameter, glabrous or sparsely pubescent at base, wrinkling on drying, 8.5-11.5 mm in diameter. Seeds brown, 6.5-9.0 mm long, broadly ovoid. Flowering as early as March, but mostly June and July. Mature fruits found in January and February.
Distribution.-In Sonora known for certain from Sierra de Alamos, and two remote areas farther east along the Rio Cuchujaqui drainage in the southeastern part of the state at 700-1400 m. Often growing out of rock crevices on precipitous cliffs and canyon walls, including south-facing cliffs, cliff tops, moist slopes, and riparian canyons; at the upper elevationallimits of tropical deciduous forest, and oak woodland, or the lower limits of pine-oak woodland. The substrates do not seem to be limestone, unlike those of populations elsewhere in Mexico. The Sonoran B. dulcis is not in cultivation.
Sonora and northeastern Mexico to Central Ameri-ca. Probably also in southwestern Chihuahua but not documented from that state. Brahea dulcis is quite variable across its entire range and there may be more than one taxon involved. Description.-Medium to large palms, the trunks often 6-12(-ca. 20) m tall, 16-33 em in diameter. Petioles often 80-135 em long, armed with teeth reaching 7.5-8.5 mm long, these usually stout, curved or straight, solitary or double. Hastula to about 3 em long, often hyaline, the sides unequal, irregularly narrowed or pointed. Leaves about 40 or fewer in number, the blades often approx. 1 m long, strongly glaucous with much variation in leaf color and indumentum, from green to silvery glaucous. Inflorescences 10-12 per tree, mostly longer than the leaves, 205-340 em long. Bractlets 1.0-1.5 mm long. Flowers (1)2 or 3 in clusters. Sepals l mm long, thin, cupped, broad, and scarious. Corollas sympetalous below, the lobes 1.6 mm long, thick and broadly deltoid. Filaments short and slender. Fruits rounded, (15.8--)18.0-19.5 mm maximum diameter. Seeds 14.5- 19.0 mm maximum diameter, nearly rounded or with the maximum diameter 10-20% larger than the minimum diameter. Mostly flowering in late spring, the fruits ripening the following spring.
Distribution.-This palm is endemic to Sonora, and shows considerable variation across its geographic range. Future studies may reveal geographic variation that could warrant infraspecific recognition.
Populations in the northeastern part of the range in Sonora occur at the upper elevations of the Sonoran Desert, while at their southeastern limits these palms occur in tropical thornscrub and the northernmost limits of tropical deciduous forest. At the higher elevations, throughout eastern Sonora, this palm extends into the lowermost oak zones.
We distinguish three populations-which are geographically definable (Fig. 1). There appear to be morphological differences in trunk and leaf size, and color and indument of leaf blades. These are as follows: Western Sonora.-Hesper palms occur in three areas in western Sonora-from the Sierra El Aguaje and vicinity northward to the Sierra Seri. These palms are generally large and robust, especially compared with ALISO those in east-central Sonora but seem to be somewhat less robust than those of northeastern Sonora. The leaf blades are generally tougher and much duller ("whiter'') than those of the east-central and northeastern Sonora populations.
Many thousands or perhaps millions of hesper palms occur in and about the rhyolitic Sierra El Aguaje between Bahfa San Carlos in the south and the vicinity of Bahia San Pedro in the north. These palms range across many habitats such as canyon bottoms, steep slopes, rock clefts, and cliffs, including sea cliffs, and sometimes extend onto upper beaches and beach dunes. Numerous palms grow out of crevices in otherwise solid rock and on north-as well as south-facing slopes, and they are especially abundant in the higher mountain mass (the summit is ca. 860 m). Among the larger groves, such as in Caii.6n del Nacapule and Caii.-6n Las Barajitas (Fig. 4), there is considerable variation in leaf color, ranging from green-leaved plants to the much more common dull, more glaucous-or whitish-leaved plants. In this region B. elegans often grows alongside Saba[ and/or Washingtonia in riparian canyons and low-elevation palm groves.
An even larger population occurs in similar habitats in the Sierra Libre where they are likewise abundant at higher elevations across the main mountain mass.
These palms grow in riparian canyons such as La Pintada at the western base of the range to peak elevation at ca. 1160 m. No other palm species is known from this range.
The most isolated and undoubtedly the smallest palm population in Sonora occurs on a north-facing slope below Pico Johnson in the Sierra Seri. There are probably fewer than one dozen of these palms, hidden from view and far from any road. The colony includes juvenile and adult plants. Known to us only from photographs taken in 1988, they appear indistinguishable from the Sierra El Aguaje hesper palms about 185 km to the south. No palms occur farther north in the desert of western Sonora.
During the 1970s a Seri fisherman brought Mary Beck Moser an immature Brahea leaf which he claimed he obtained from a single plant on the west side of Isla Tibur6n. Other Seri people also knew of this palm. Repeated attempts by Felger, even with aerial searches, have failed to locate this plant. Narrow, slotlike canyons on the west coast of this large island might shelter a palm, but the region is extremely arid and hardly seems suitable habitat for palms (see Felger and Moser 1985). However, B. armata does occur in semiriparian canyons on the not-too-distant Isla Angel de Ia Guarda. Strangely, the Seri did not tell Moser or Felger about the isolated colony in the Sierra Seri.
North-central Sonora.-These are the northernmost hesper palms in Sonora, occurring within the Rio Sonora drainage. They are scattered in localized populations in the Sierra Aconchi between Ures and Nacozari, and north through the Sierra to the valley bottoms near Arizpe (Fig. 5). Some are planted in the town of Arizpe. They have relatively green leaves and are strikingly large and robust, often reaching 18 min height. From a distance these palms might be mistaken for Washingtonia robusta. They appear to be morphologically continuous with the increasingly smaller hesper palms farther south in east-central Sonora.
East-central Sonora.-Numerous, mostly widely scattered, and often small groups of these palms occur in eastern Sonora from the vicinity of Onavas and Nuri northward to the vicinity of Moctezuma. The region is entirely in the Rio Yaqui drainage. Some of these palms can be seen from Highway 16 (the Hermosillo-Yecora road) in the vicinity of El Palmar de Onavas and Agua Amarilla. The southernmost of these palms approach B. aculeata in appearance but seem to be larger in overall size, and bear the smaller fruits characteristic of B. elegans.
Horticulture.-Plants grown from seeds, most often obtained in the Sierra El Aguaje region, are occasionally grown in southern Arizona and Sonora. This palm is relatively slow-growing, and thrives under cultivation in the Sonoran Desert, tolerating freezing weather in Tucson without damage. It is worthy of wide cultivation in very hot climates.
Notes.-The source plant for the type of Erythea elegans Franceschi ex Becc. was a cultivated palm grown from seed said to have been collected about 25 years earlier by a miner "in the vicinity of Hermosillo" (Beccari 1907). The type specimen has spiny petioles, glaucous leaves, and mature fruits 1. 7-1.8 em long. Wright's letter to Beccari pointed out that the source plant (the Buddington plant, Los Angeles, CA) and other plants grown from its seeds were different from the Baja Californian E. armata and E. brandegeei (Purpus) H.E. Moore.
Based on its cultivation in southern California in the late 19th and early 20th centuries, B. elegans was reported to be dwarf in habit and slow-growing. In fact plants from the hot desert of Sonora often are stunted when cultivated in the nondesert regions of California (see Bailey 1937).
Hesper palms in western Sonora have also been called B. roezlii Linden (e.g., Wiggins 1964), like~ise based on a poorly documented cultivated specimen. Bailey (1943) showed B. roezlii to be a synonym of B. armata of Baja California.
The relationships with the geographically neighboring hesper palms, B. aculeata, B. armata, and B. brandegeei remain unresolved. The hesper palm of western Sonora is distinguished from B. armata by its more slender trunk, generally greener (not as "white" or "silvery") leaves that are more variable in color, and smaller inflorescences. However, some cultivated hesper palms at the Huntington Botanical Gardens in southern California. grown from seed obtained in the vicinity of Bahia San Carlos, are exceptionally robust and approach B. armata in gross appearance. Henderson et al. (1995) show B. armata in northwestern Sonora in a region where there are no native palms. Brahea armata is endemic to Baja California and Isla Angel de Ia Guarda in the Gulf of California.
Brahea brandegeei was considered to be endemic to the Cape Region in southern Baja California Sur prior to the field guide by Henderson et al. ( 1995). Wendy Hodgson and Jon Rebman found a large population of hesper palms in the Sierra San Francisco, in northeastern Baja California Sur (Hodgson & Rebman 8171, ASU, BCMEX, DES). Are the Sierra San Francisco palms conspecific with B. brandegeei s.s. and/or the Sierra El Aguaje palms? Henderson et al. (1995) list B. elegans as a synonym of B. brandegeei but offer no explanation for their decision. The Sierra San Francisco hesper palms grow among Sonoran Desert vegetation in deep semiriparian canyons. Unlike their Sonoran counterparts, they seem to be confined to canyon bottoms and there appears to be a larger percentage of very tall palms. Brahea brandegeei from the Cape Region of Baja California Sur seems to differ from the Sierra San Francisco and western Sonora plants by having generally greener and thinner leaves and other characters cited by Bailey (1937) including inflorescences only as long as or shorter than the leaves. These characteristics, however, have not been quantified or studied in depth.  (BH). 14.1 km N of Bahfa San Carlos, ca. 3.2 km from the ocean, steep canyon with spring, stream, and palm oasis, 100m, Boutin 2017, 2018 (BH, HBG Vernacular names.-Babiso (vicinity of Nacori Chico and Cucurpe). Jabehui (Rio Satachici. Palma liza "smooth palm" (name given at Los Bajfos "for a palm that grows to the east up in the mountains"). Metajcu

(Guarijio).
Description.-Graceful palms, the trunk to ca. 10 m tall, usually much shorter, and 15.5~a. 30 em in diameter. Petioles entire or sometimes with a few minute teeth near the base, bluish glaucous, about as long as the blades, 1.6-:-4 em wide the near base, tapering to 1.1-2 em wide near the blade; hastula often 3-5 mm long, glabrous or ciliate. Leaf blades of larger trees ca. 80-100 em long, slightly wider than long, relatively fiat, shiny green above, bluish glaucous below, the segments divided to about half way, with a very slender, brown, curled fiber in the sinus of each leaf segment. Inflorescences arching, often reaching ca. 2.0-2.3 m long, 4-times branched; inflorescence branches and branchlets (includes rachillae) with fine, whitish hairs. Rachillae floriferous nearly to their bases, 20-56 mm long, 0.7-0.9 mm in diameter. Aowers sessile, subtended by minute, broadly deltoid bractlets with acute tips. Calyces 1.2-1.5 mm long, cuplike, the sepals imbricate, separate, broadly triangular, very thick towards the base, puberulent with short, thick, white hairs. Petals 2.2-2.8 mm long, with sparse hairs below like those of the calyx, valvate in bud, slightly cupped near the apex, faintly indented (grooved) to accommodate the anthers, the filaments only united basally, broadly triangular with the upper portion slender and free. Young fruits pubescent; mature fruits 11.0-13.0 mm long, 8.5-9.0 mm maximum width, broadly ellipsoid, smooth and yellow-brown to purplish when fresh with a thin fleshy pericarp, wrinkled when dry, and often with short, sparse hairs near the base, otherwise glabrous. Seeds 8.3-11.0 mm long, 6.4-7.2 mm maximum width, ovoid-ellipsoid, light brown, smooth. Aowering primarily June and July; fruits mature late July of the same season, at least among northern Sonora populations. ently also on rhyolite; growing in crevices or among rocks on steep slopes, sheer cliffs, and canyon walls, and less often along canyon bottoms. The northernmost populations are in riparian canyons in Sonoran Desert-oak woodland ecotone in northeastern and north-central Sonora (Fig. 6, 7). This palm also occurs in widely scattered mountain canyons east of the Sonoran Desert. In southeastern Sonora it is sometimes common in narrow, riparian canyons and on cliffs in tropical deciduous forest, oak woodland, and pine-oak woodland or pine forest.
This species, as defined by Quero (1989), ranges southward in western Mexico to Guatemala. There are large distributional gaps between the Sonoran populations and those of southern Mexico. These gaps, however, could be an artifact of the collection records since this palm tends to grow on cliffs in remote mountain regions with dangerous access due to illicit agriculture.
In riparian canyons along the Rio Satachi, near Nacori Chico, in northeastern Sonora, these palms grow alongside maples (Acer grandidentatum Nutt.), oaks (Quercus spp.), and organpipe cacti (Stenocereus thurberi [Engelm.] Buxbaum). The main palm canyon at Cerro Cinta de Plata (Sierra Baviso, about 25 km southeast of Magdalena de Kino), on the southwest side of this limestone mountain, supports the largest and densest population of this species in Sonora. Thousands of palms are crowded in the rocky canyon bottom and below north-facing cliffs of this deep, rugged, and steep bowl-shaped box canyon, locally called El Baviso. Cattle are excluded from the canyon by huge boulders and rock faces at its lower end. Smaller populations occur in other nearby canyons and mountains that are likewise inaccessible to cattle. These palms were misidentified by Shreve ( 1951: 7 4) as Sahal uresana and by Wiggins (1964: 324) as Erythea roezlii.
Horticulture.-Brahea nitida is readily grown from fresh seed and is occasionally cultivated in southern Arizona in Phoenix and in warmer areas in Tucson. It is the most frost-sensitive of the cultivated Sonoran palms. In Tucson the leaves are often severely damaged by freezing weather, and it probably cannot be grown out-of-doors in the colder areas of the city. This magnificent palm is worthy of extensive cultivation in hot, arid to semiarid climates.
Note.-We are following Quero (1989)  Description.-Large palms branching (suckering) from the base. Leaf bases persistent on the trunk. Leaves glaucous gray-green, several meters long. The genus is "easily distinguished from all other palms by the induplicate [leaflets V-shaped in cross-section] pinnate leaf with the lower leaflets modified as spines" (Uhl and Dransfield 1987: 217). Dioecious; inflorescence branches orange, much shorter than the leaves. Male flowers with very short filaments. Pericarp sweet and edible, the seeds ca. 1.5-3 em long, more than twice as long as wide, and conspicuously grooved.
Distribution.-A few date palms are marginally naturalized, or perhaps only persistent, on Isla Lobos, a coastal, sand-bar island of southwestern Sonora. Elsewhere date palms occasionally persist from abandoned plantings. In contrast, this palm is naturalized at widely scattered riparian or semiriparian habitats in Baja California Sur.
Horticulture.-The date palm is native to the Middle East, although truly wild populations are not known with certainty to exist. It was apparently first brought to Sonora by the Jesuit missionary Padre Eusebio Kino in the late seventeenth century. At that time only seeds could be transported. Vegetatively propagated varieties Were first successfully introduced into the southwestem United States in 1890 (Nixon 1950) and presumably soon taken to Sonora. Date palms are widely cultivated, sometimes commercially, in the lowlands throughout Sonora. The widely cultivated P. canariensis Hort. ex Chabaud is distinguished by its massive, solitary trunk, and green leaves.
Southeastern United States to northern South America including most of Mexico except the Baja California peninsula, most of the Caribbean, and Bermuda; 16 species (Quero 1989;Zona 1990 Description.-Large palms, often ca. 5-15 m tall, the trunks often 26-36 em. in diameter. commonly firescarred. Leaves large, reaching 4.4 m long, the petioles entire, (64-)80-260 em long, to 9 em wide near base and 2.5-5 em wide just below the blade, the hastula 5-18 em long, triangular, more than twice as long as wide, persistent and firm with entire margins, the blades often ca. 90-180 em long (from base of hastula to apical tip), markedly costapalmate (the petiole extends well into the blade on the lower or abaxial surface), partly curved, glaucous bluish green, often with coarse intersegmental fibers. Inflorescences including peduncles 96-235 em long, spreading to arching (not drooping), much branched, shorter than, to sometimes nearly as long as the leaves. Flowers sessile; sepals united below, the lobes entire, the petals 4.4-5.3 mm long; filaments rather fleshy, united below into a tube about as long as the sepals, the free portion relatively long. Fruits 13-23 mm in diameter, 12-18 mm in height, globose, brown to blackish; seeds 10-16 nun in diameter, 4-10 nun in height, depressed-globose, dark red-brown ("chestnut") to blackish, glossy. Flowering April to June, mostly in May; fruits ripening in August in the desert, and September and October in the mountains. 2n = 36 (Eichhorn 1957).
Distribution.-Sonoran desertscrub, thomscrub, tropical deciduous forest, and lower elevations in oak woodland. West-central and eastern Sonora, from near sea level-1220 m. Mostly on deep, gravelly to sandy or silty soils. Scattered groves along or near the coast from Bahia San Carlos northward to Bahia San Pedro, mostly along the bottom of riparian canyons including Nacapule and Barajitas, low-lying swales or depressions, and occasionally on coastal dunes and upper beaches. Farther inland on sandy plains, baj(os (lowlying areas), hills, floodplains, and canyon bottoms. On low hills in eastern and central Sonora from Opodepe southward, especially near the desert-thomscrub ecotone (Fig. 8). Seldom on rocky slopes. Sabal palms are often left standing in fields, orchards, and pastures.
This species also occurs in southwestern Chihuahua where it is probably not rare. We do not know of any specimens, however. The one record (Zona 1990) is a herbarium sheet at BH with correspondence from George Lindsay but lacks a specimen. We have seen no specimens from Sinaloa, but a large palm extensively utilized for making hats in the vicinity of Choix in northeastern Sinaloa appears to be this species (Barney Bums, pers. com., 1995). Furthermore, Hermilo Quero (pers. comm., 1998) reports that he has documented it from northern Sinaloa.
There seems to be north-south and elevational clinal variation in overall plant size with plants of the northem populations larger than those to the south. There is also geographic variation in fruit size, with the northernmost populations bearing the largest fruits, while plants near Ures and along the coast bear the smallest fruits.
Horticulture.--Occasionally cultivated in Sonora and Arizona, S. uresana is recommended as a landscape tree for large areas. It is not damaged by freezing temperatures at least as far north as Tllcson. The plants seldom survive bare-root transplanting and are not suited to container cultivation since they quickly develop deep roots.
Notes and comments.-Bruchid beetle larvae in the genus Caryobruchus (Bruchidae: Pachymerinae) feed on Sabal seeds, and adults feed on the floral nectar.
Seed predation by bruchids can be as high as 50-90% (Zona 1990;Joyal 1995). The fruits also are eaten by many animals including coatis, coyotes, foxes, raccoons, and ringtail cats. Hooded and streaked-backed orioles weave their nests from the leaf fibers, attaching them to the undersides of leaf blades.
The plants and fruits of S. uresana are among the largest of any species of the genus. Southward in Sinaloa this species is replaced by S. rosei (Cook) Becc., distinguished in part by its more slender trunks and greener leaves. Saba/ rosei in turn is replaced by S. pumos (Kunth) Burret farther south in the Rio Balsas Basin. These three sabals constitute the phylogenetic arm of the genus in western Mexico (Zona 1990). There is a gap of approximately 300 km between the southernmost documented S. uresana and the northernmost S. rosei. However, this intervening area is poorly known botanically and much of it was converted to agriculture long ago.
Description.-Trunks reaching ca. 15-20 m tall, 98-104 em circumference, often fire-scarred. Petioles of juvenile to half-grown trees armed with strong, sharp, orange-brown teeth 10-15 mm long along the full length, some teeth double-pointed; petioles of taller trees often reaching 1.4 m long, the margins entire or with some basal teeth to 3.0-3.5 mm long. Hastula large, papery, more or less triangular, the margins irregular, fraying with age; leaf blades uniformly shiny green on both surfaces, nearly flat, the free portion of the segments usually drooping.
Flowering branches often reaching ca. 2.6 m long, longer than the leaves, arching, then drooping with weight of the fruits. Flowers white, short-pedicelled; sepals united below, the lobes with ragged margins; stamens separate, borne on the corolla tube. Flowering May and June, the fruits ripening in fall to early spring. Fruits ellipsoid, 7.5-9.0 mm long, blackish when ripe, the thin, fleshy pericarp edible and sweet like a date, the fruits mostly falling with the dry, persistent calyx and short pedicel. Seeds 4.7-6.5 mm long, 4.5-4.9 mm wide, ellipsoid to globose, dark redbrown, smooth or nearly so on the dorsal side, the lower surface (hilum side) wrinkled. 2n = 36 (Eichhorn 1957).
Distribution.-In Sonora native only to canyons and oases in the Sierra El Aguaje at ca. (10-) 30-135 m. Locally dense populations occur in the upper part of Cafi6n del Nacapule and in several very steep, seaward-facing canyons and oases in mountains along the coast northwest of Bahia San Carlos, e.g., La Huerta. Also locally abundant along canyon bottoms and oases in the canyon systems of Los Anegados and Las Barajitas. In all of these canyons and oases seedlings and small plants are abundant. These palms are limited to immediate margins of streams and at springs with permanent or near permanent water or wet soil where it locally outnumbers Brahea and Sabal.
The limited distribution and extremely localized groves of W. robusta in Sonora make it vulnerable to local extirpation. Rose (1899: 255) found W. robusta at Guaymas, and reported that "most of them have been cut out and used as rafters for houses." Later reports make no mention of this species occurring naturally at Guaymas. This species is otherwise native only in Baja California Sur.
Palms on the western slopes of the Sierra del Tigre reported as W. sonorae by White (1948, Fig. 21) are actually Brahea, probably B. elegans.
Horticulture.-Although of very local and limited distribution in its native habitats, together with the date palm it is one of the most widely cultivated extratropical palms in the world. This tall, stately palm is a common street tree and landscape subject in northwestern Mexico, southern Arizona, and southern California. It is the fastest-growing of the Sonoran palms. This species is raised in containers or field-grown and commonly transplanted even when large.
Both species of Washingtonia thrive best in dry or seasonally dry climates with some cool winter nights. Washingtonia filifera is much more frost-tolerant than W. robusta (see Turner et al. 1995). In cultivation W. robusta grows well with hot and either dry or humid summer climates, whereas W. filifera is susceptible to lethal bud rot when cultivated in regions with a summer rainy season or wet, foggy climates such as coastal California (Bailey 1936).
Notes.-The fruits are eagerly eaten by many birds and various mammals including badgers, coyotes, and raccoons. Seeds are often found germinating in decaying raccoons droppings. Bailey (1936) pointed out that petioles of mature trees have few or no marginal spines. Cornett's (1986) note on W. filifera confirms Bailey's earlier observations and speculates that there might have been a relationship with Pleistocene mastodons which had a vertical reach of about 6 m. However, Sabal has entire petioles throughout its life history, and certain Brahea species retain stout petiole spines throughout their lifespan.  (BH).