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A review of the information on the richness and distribution of the Mexican aquatic and wetland (herbaceous) monocots, is presented, for the purpose of contributing to a better understanding of the flora distributed in the wetlands of the national territory. Three hundred eighty one species (392 taxa) belonging to 104 genera and 28 families, considered as strict aquatics or wetland plants, were registered; as well as 114 tolerant or facultative hydrophytes of lacustrine and pond habitats. Half of the 28 families correspond to taxa considered by most botanists as terrestrial, but they represent a large component of the Mexican aquatic flora (71% of the genera and 75% of the species). The endemics make up 14% of the monocots. Their presence throughout a great diversity of habitats and its representation in several vegetation types and communities, make them one on the most diverse ecological and geographical components in the American continent. About 46% of the species belong to meridional elements, while 25% correspond to boreal one; while the Mexican element (13.9%) is equivalent to the sum of the cosmopolitan and introduced species. [ABSTRACT FROM AUTHOR]

Among the many explanations for the large biological diversity of Mexico is that it is the result of the contact between the Nearctic and Neotropical biotas; however, this contact-related explanation is not fully satisfactory and needs further examination in the light of historical biogeography. We offer newer insights into this issue by examining the history of the flora and the vegetation heterogeneity of the seasonally dry tropics of this country. Several environmental criteria can be used to define the seasonally dry tropical regions, but setting their precise geographical boundaries is not always straightforward. This is largely due to the large vegetation heterogeneity of this region, within which the tropical dry forest (TDF) is prominent. The origin of the TDF flora can be traced back at least as far as 20 million years before present and seems to be associated with the Tertiary North American flora. Available evidence does not support a South American origin of the TDF flora. Similarly, the separation of the TDF and the hot North American desert floras into two different bio-geographical realms is not warranted. The history of the seasonally dry tropical flora of Mexico strongly suggests that this bio-geographical dichotomy should be replaced by the recognition of the existence of a Pan-American Realm. [ABSTRACT FROM AUTHOR]

A morphological description of the genus Mimophytum greenm. (Boraginaceae) is provided, as well as a dichotomous key to the species and ecological and distributional information. The genus is endemic to the Sierra Madre Oriental of Mexico. morphological descriptions for the two species are provided. One of them, M. benitomartinezii, is proposed as new to science. It differs from M. omphalodoides in that the stems are rhizomatous-stoloniferous, the upper leaf surfaces are glabrous, the leaf blades possess 3 basal nerves, the inlorescence is an ebracteate, scorpioid cyme, the pedicels are shorter, and the fruits have glochids forming a ring around the edges. [ABSTRACT FROM AUTHOR]

The nomenclatural statuses of Tillandsia parryi Baker and T. sueae Ehlers are clarified, and 72 suesilliae is described as new. Data relative to the distribution, ecology and phenology of the studied taxa are provided. [ABSTRACT FROM AUTHOR]

We report, for the first time, the presence of Nierembergia angustifolia in the state of Jalisco, Mexico. The distinctive characteristics of this species and an update of its known geographical distribution are discussed. [ABSTRACT FROM AUTHOR]

A phytosociological study of 59 relevés was carried out at Laguna Quila, National Park Lagunas de Zempoala, México, using the Zürich-Montpellier approach. Eleven communities were identified and described. A distinction was made between a submerged and a helophytic hydroseral vegetation. A pronounced humidity gradient was identified in a north-south direction, and also a continuous desiccation was observed. A vegetation map scale 1:1900 is included. 21 families of vascular plants including 41 species and 33 genera have been identified. Families best represented include Cyperaceae with seven species and Ranunculaceae with four species. Phytogeographical analysis on the generic level revealed that the temperate component reached 65%, the cosmopolitan 30% and the tropical 5%. The species of Laguna Quila have a wide distribution in Mexican hydroseries and elsewhere in temperate America. Aquatic and semi-aquatic communities are vanishing rapidly in Mexico, and it is important to understand the dynamics for adequate management of this natural resource. In order to protect this lake it is recommended to control the water extraction of the laguna, to exclude cattle and other activities who can affect indirectly Laguna Quila. [ABSTRACT FROM AUTHOR]

Two species of Valeriana of apparently very restricted distribution are described as new. V. emmanuelii, collected in two localities of the southern extreme of the municipality of Morelia, Michoacán, is related to V. retrorsa Fern. and to V. densiflora Benth. V. zamoranensis belongs to the series Ceratophyllae and is only known from the highest part of Cerro Zamorano; it seems to be related to V. zapotecana Barrie and to V. otomiana Barrie. [ABSTRACT FROM AUTHOR]

We report, for the first time, the presence of five species of Solanum for the Bajío and neighboring regions flora. Solanum brachistotrichum, S. hintonii, S. jamesii y S. morelliforme are grouped in Solanum section Petota while S. triquetum is part of Solanum section Dulcamara. We highlight the distinctive characteristics of each species and update their known geographical distribution. Finally, we present a drawing of S. triquetrum. [ABSTRACT FROM AUTHOR]

The vegetation and the vascular plants of an ecotonal zone between the floristic provinces of the Desert Plateau (Chihuahuan Desert) and Gulf Coastal Plain in northeastern México were studied. The study zone has a surface of 2,526.25 km² and it is located in the northern part of the state of Nuevo León. On the basis of physiognomy, ecological characteristics and dominant species, seven types of vegetation were recognized. With the aid of 50 sampling plots, aerial photographs and floristic composition, the units of vegetation were delimited and mapped. 405 species (varieties and subspecies included) were identified. The study zone showed geographical affinity with the vegetation of the Chihuahuan Desert in the Desert Plateau of México (Hilaria mutica grassland, low thornless scrub of Flourensia cernua and medium size mixed scrub of Acacia-Prosopis-Flourensia-Larrea) and with the Gulf Coastal Plain (medium size mixed scrub of Leucophyllum frutescens and Acacia rigidula and high mixed scrub of Helietta parvifolia). The medium size and high thorny scrubs of Prosopis-Acacia showed no clear relationships with any of the floristic provinces. The coexistence of shrubby vegetation characteristic of the lowlands in the Gulf Coastal Plain and the vegetation usually present in the Chihuahuan Desert, can be explained in view of the increment of aridity and gentle raising of the continental surface in east-west direction, and of the absence of notable topographic accidents in the northeastern region of México. [ABSTRACT FROM AUTHOR]

A check list of vascular plants consisting of 89 families, 208 genera and 288 species is presented. The study area, called Sierra de Nanchititla, is located in the southwestern region of the State of Mexico, near the borders with Guerrero and Michoacán. The families Asteraceae, Pteridaceae, Burseraceae, Fabaceae, Mimosaceae and Rubiaceae are best represented. Geographical distribution of families and genera is analyzed. The elements of tropical affinity are dominant. Complementary data on phenology of some life forms are provided as well as information about the state of conservation of original vegetation. [ABSTRACT FROM AUTHOR]

Quercus gambelii Nutt. is a widespread white oak (Quercus, subgenus and section Quercus, subsection Gambelieae) in the southern Rocky Mountain region of the United States, extending to west-central Chihuahua in the Sierra Madre Occidental of Mexico. Quercus arizonica Sarg., rather distantly related (subsection Glaucoideae), has a more southern distribution in the United States, and extends through the Sierra Madre into Durango. In the southwestern United States hybrids between Q. gambelii and several white oaks, including Q. arizonica, are very common, often forming a major portion of the lower elevation oak vegetation, particularly in New Mexico. These hybrids are known in general as Q. x undulata Torr., pro sp. A plant very similar to Q. x undulata, Q. lesueuri C. H. Muller, was collected by Harde LeSueur at "El Salto de Babicora", in west-central Chihuahua, in 1937. It has not been collected since. An oak similar to Q. lesueuri was collected by the author in the nearby Sierra Catarina where it is sympatric with Q. gambelii and Q. arizonica. El Salto de Babicora was determined to be located north of the town of Madera. In this canyon Q. gambelii and Q. arizonica are common. Quercus lesueuri and the newly collected hybrid from the Sierra Catarina are shown to be strongly similar to Q. x undulata and intermediate between Q. arizonica and Q. gambelii through the use of the same six leaf characters (leaf width, relative depth of indentations of leaf margin, conspicuousness of intercostal reticulum, number of major secondary veins, number of rays per stellate hair, curliness of hairs) that Tucker used to assess intermediacy of certain collections to the putative parents Q. gambelii and Q. arizonica. In this paper Q. lesueuri is demonstrated to be part of this hybrid complex. Taxonomically it should be recognized as Q. x lesueuri C. H. Muller, pro sp., and to be considered as a synonym of Q. x undulata, sensu lato. [ABSTRACT FROM AUTHOR]

Commelina nivea López-Ferrari, Espejo et Ceja, and Commelina rzedowskii López-Ferrari, Espejo et Ceja, two white flowered species are described and illustrated in this paper. The former is known only from Las Adjuntas, municipio of Pueblo Nuevo in the state of Durango and the other was collected in the neighborhood of Tenería, municipio of Tejupilco in the state of México. [ABSTRACT FROM AUTHOR]

The present status of the floristic-ecological knowledge of wild Mexican Iridaceae is defined. 16 genera and 98 species of Iridaceae, all of them belonging in the 4 tribes of the subfamily Iridoideae are registered from the country. The tribe Tigridieae has its principal center of radiation in Mexico, where 11 of 18 genera and 52 of approximately 130 species grow; of those, 3 genera (30 %) and 38 species (71.7 %) are endemic. One naturalized species is also known. The best represented genera of Iridaceae in Mexico are Sisyrinchium (40 spp.) and Tigridia (29 spp.). Endemism in the family at species level reaches 54.6 %. Data and comments on habitat, distribution and phytogeography of Mexican Iridaceae are included. [ABSTRACT FROM AUTHOR]

A successional role for each phytogeographical group of seral stands of the pine-oak forests in the Highlands of Chiapas (southern Mexico) could be established after their structural analysis. Most of the Holarctic elements regenerate in early successional conditions, while the regeneration of many Andean and East Asian elements is restricted to the more advanced stands. Forest structure and floristic composition appears as the result of a mixture of species belonging to genera of diverse origin. Their local coexistence seems to depend on their tolerance to those environmental conditions resulting from forest development through succession. We ascribe a central role to the canopy species belonging to Holarctic genera which determine the understory microhabitat for most of the remaining woody species, notably for those of Andean affinity. [ABSTRACT FROM AUTHOR]