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La pendejada que dejo el pholiantes: A classification for excent fernsLa pendejada que dejo el pholiantes: A
classification for excent ferns Increasingly robust pylogenetic hypotheses for ferns utilizing data from morphology, seven choloplast markers , one numlear gene and, three mitochondrial genes prompt us to reevaluate the classification of these vascular plants. Multiple-gene phylogenetic analyses studies by Wolf , Wolf and al. Pryer& Schneider & al, Wikstrom &pryer, and Schuattplez & al, have griven rise to growing conviction in both the composition and relationships of taxa at familial and ordinal ranks. Five recent mnorphological analyses of relationships, by Pryer al, Schneider, Stevenson & Loconte, and Sneider & al. have increased support for the molecularbased consensus topology. For eusporangiate and basal leptosporangiate ferns, evidence is now sufficient to allow us to circumscribe confidently most clades and assign ranks . However. For some more derived leprosporangiate ferns the phyologeneti evidence is still somewhat equivocal . Consequently, declararion os phylogenetic position for some taxa and assiqnment of ranks in a classical “Linnenan –style” hierarchy, are tentavtive .In this paper we present a revised view of the classification of extant ferns , taking into account all revelant evidence. We focus our classification at the ranks of class. Orden and family believing that the information at hand is most appropriate for resolution ane understanding of relationships ayh these levels. Whitin most families, and especialy at the generic level. There is still insufficient evidence to attempt many classificatory decisions. In the classification proposed herein, we account for and place in revisedtaxonomic framework, all names et family and ordinal rank utilized in previousmajor classification directed at ferns , particulary those that have been proposed in the eighty years: Bower, Chritensen, Ching, Dickanson, Coperland, Holttum Pichi Semolli, Mehra Wagner Nayar Tagawa&Iwatsuki, Mickel , Tryon & Tryon Karmer and Stevenson & Loconte. WE also consider various herbarium schemes in common use such as the on by Crabbe & al . Many of these Classification as well as others , have been reviemed and reproduced by Pichi Sermolli, who also summarized detailed information on family names of ferns . Smith provided a recent summary and discussion of these classification. ï‚· La selva alta perennifolia también conocida ï‚· La selva mediana también denominada bosque tropical subcaducifolio, se caracteriza porque cuando menos la mitad de sus árboles pierden las hojas en la temporada de sequía. Se distribuye entre altitudes entre 0 a 1,300 m, con temperaturas entre 0°C a 28 °C y con precipitaciones anuales entre 1,000 a 1,600 mm. En general se considera que se trata de bosques densos que miden entre 15 a 40 m de altura, y más o menos cerrados por la manera en que las copas de sus árboles se unen en el dosel. Entre sus formas arbóreas se pueden encontrar ejemplares de Enterolobium cyclocarpum, conocida como “parota” o “guanacaste”, Cedrela mexicana o “cedro rojo” así como varias especies de Ficus spp. junto con distintas especies de lianas y epífitas. Su distribución geográfica se presenta de manera discontinua desde ï‚· La selva baja conocida también como bosque tropical caducifolio, es característica de regiones de clima cálido, que se desarrolla entre los 0 a 1,900 msnm, con una temperatura media anual de 20 a 29°C, que presenta en relación a su grado de humedad, una estación de secas y otra de lluvias muy marcadas a lo largo de año, por lo que su precipitación media varía de 300 a 1,800 mm. Son comunidades relativamente bajas, que en condiciones poco alteradas suelen ser densas con árboles de hasta 15 m de alto, más frecuentemente entre 8 a 12 m. Pueden presentar colores llamativos y pierden las hojas en forma casi total durante un lapso de 5 a 8 meses del año. Este tipo de vegetación es más bien propio de la vertiente pacífica del país, cubriendo grandes extensiones casi continuas desde el sur de Sonora y el suroeste de Chihuahua hasta Chiapas, así como parte de baja California Sur. En la vertiente del Golfo se presentan tres franjas aisladas mayores: una en Tamaulipas,San Luis Potosí y norte de Veracruz, otra en el centro de Veracruz y una más en Yucatán y Campeche (Rzedowski & Equihua, 1987). Entre las especies más frecuentes de este tipo de vegetación se encuentran la Bursera spp “cuajiote” o “copal”, Ceiba aesculifolia “pochote” e Ipomea spp, en Classification srve many purposes , amog them to provide a genealogical framework In ehich to iidentify plants , organize gebaria , retrieve information , and to conduct many kinds of studies : milti-use classification serve us best if we name only those clades that are readily recognizable and characterized by morphological synapomorphjic characters, at least at family abd higher rakns. Hopwever . more traditional and practical classification are sometimes incompatible with the results and classifications implied by phylogenetic studies , especially when the principle of monophyly is used as a grouping criterion .when a traditionally recognized family nests qithin another , complex classificatory choices ensue: 1 recognition of araphyletic pamilies 2.- dismemberment of a recognized family into smaller families 3.- integration of the traditional family that causes the paraphyly into the “progenitor” family The first choice , preferred by some , leads to recognition or natural gropus, which in our opinion often retards or obscures investigation into interesting biological, phytogeogrqphic, and evolutionary questions. Tha second solution supposes that we have morphological synapomoirphies for nodes that lead to all of the segregate families and this is not often the case , although ojne hopes that eventually we chall find these synapomorphies . until then , it may be nearly find these dynapomorphyiees . until then , it may by nearly impossible to define some segregate families in such a way that they would be both kyable and circunscrible. The third solution is a fast fix to the problem but expendiency oftem demands that at least some of the problem, but expendiency often demands that at least some of the intrafamilial subclades also be recognized taxonomically , either of, or with an unranked informal name until further decisions on rank can be made Política de privacidad |
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