Phylogenetic relationships in the genus Helvella were investigated using both LSU rDNA sequences and morphological features. The latter were coded and included in the analyses, resulting in better-supported clades. Helvella is monophyletic and Wynnella is its sister genus. Aporhynchous vs. pleurorhynchous asci are the synapomorphies for the 2 subgenera, Leucomelaenae and Helvella, which were confirmed as natural groups. Other recovered supported clades were section Leucomelaenae in the subgenus Leucomelaenae, and sections Elasticae, Helvella, and Lacunosae within the subgenus Helvella. Generic description, comments on taxonomically informative features, species complexes, and species that need typification are presented.
ResumenLa tribu Tigridieae (Iridoideae: Iridaceae) es un grupo americano y monofilético. Sus centros de diversificación se localizan en México y la parte andina de Sudamérica. El objetivo del presente trabajo fue analizar la riqueza y distribución de Tigridieae en Norteamérica. Para ello, se utilizó una base de datos con 2,769 registros georreferenciados. Mediante sistemas de información geográfica (SIG) se analizó la riqueza de Tigridieae por división política, ecorregión y una cuadrícula de 45×45 km. Tigridieae está representada por 66 especies y 7 subespecies. De estas, 54 especies y 7 subespecies son endémicas. Tigridia es el género más diverso con 43 especies y 6 subespecies. La riqueza de taxa se concentra en México en los estados de Oaxaca, México y Jalisco. El análisis por ecorregiones muestra al bosque de pino-encino de la Faja Volcánica Transmexicana como la más diversa con 36 taxa. Por último, la celda más diversa contiene 14 taxa y se localiza en donde convergen el bosque de pino-encino de la Faja Volcánica Transmexicana, el bosque tropical caducifolio del Bajío y el bosque tropical caducifolio de la cuenca del río Balsas.
Mexico is a megadiverse country. Presently, 22 126 species of angiosperms have been registered within its territory and 11 001 are considered to be endemic. However, their geographical distributions are far from homogeneous. In addition, Mexico is the center of diversification of several groups. Our analysis focused on such groups. The aims were to identify areas of species richness and endemism. A data matrix with 766 species and 25 579 geographical records was analyzed. It included Calochortus (Liliaceae); Bletia (Orchidaceae); Tigridieae (Iridaceae); Amaryllidaceae; Poliantheae, Echeandia (Asparagaceae); Crassulaceae; Hylocereus (Cactaceae); Solanum, Lycianthes and Physalinae (Solanaceae); Salvia section Membranaceae (Lamiaceae); and Cosmos and Dahlia (Asteraceae). Using Geographic Information Systems, we determined richness and distribution based on: (i) Mexican political divisions, (ii) biogeographical regions and provinces, (iii) a grid of 0.5 × 0.5° cells, and (iv) elevation. The areas of endemism were estimated using the endemicity analysis. The highest number of taxa and endemic plants were concentrated within the Transmexican Volcanic Belt in the Mexican Transition Zone. This mountain range has been recognized as a province on the basis of geologic, tectonic, geomorphologic, physiographic and biogeographic criteria. It is a 1000 km long volcanic arc that extends east to west through Central Mexico and is variably from 80 to 230 km wide, between 17°30′ to 20°25′N and 96°20′ to 105°20′W. Our results represent a local deviation from the global richness latitudinal gradient of angiosperm species.
Native Mexican woody bamboos (Poaceae: Bambusoideae: Bambuseae) are classified in subtribes Arthrostylidiinae, Chusqueinae and Guaduinae. They grow from sea level up to 3200 m along the main mountain ranges and occupy different vegetation types. The aims of this study were to: identify the areas with the most species diversity; detect areas of endemism; and discuss the conservation status of the native Mexican woody bamboos. We gathered presence records for 51 Mexican woody bamboo species, based on herbarium records and personal collections. Richness was analysed taking into account: Mexican political divisions; biogeographical regions and provinces; a grid cell size of 55 × 55 km; and elevation. Areas of endemism were obtained using endemicity analysis. Thirty-five of the 51 species are endemic to Mexico. Chiapas has 24 species, followed by Veracruz with 19 and Oaxaca with 16. However, Veracruz harbours the greatest number of endemics with 14 species, followed by Oaxaca with 13 and Chiapas with 11. The Veracruzan province has the highest species richness with 20 species, followed by Chiapas Highlands and Sierra Madre del Sur with 19 species each. Twenty-six of the 35 endemic species were known only from ten or fewer sites, and eight of the 26 species are considered to be Critically Endangered.
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