El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar
This contribution is essentially a complement to the data and concepts exposed in a previous paper, devoted to the topic of diversity and origins of the Mexican phanerogamic flora. A part of the mentioned paper deais with the subject of endemism which, according to evidence and estimations, invol...
| Váldodahkki: | |
|---|---|
| Materiálatiipa: | Online |
| Giella: | spa |
| Almmustuhtton: |
Instituto de Ecología, A.C.
1991
|
| Liŋkkat: | https://abm.ojs.inecol.mx/index.php/abm/article/view/620 |
| _version_ | 1799771156585119744 |
|---|---|
| author | Rzedowski, Jerzy |
| author_facet | Rzedowski, Jerzy |
| author_sort | Rzedowski, Jerzy |
| collection | ABM |
| description | This contribution is essentially a complement to the data and concepts exposed in a previous paper, devoted to the topic of diversity and origins of the Mexican phanerogamic flora. A part of the mentioned paper deais with the subject of endemism which, according to evidence and estimations, involves the family level and accounts for *10% of the genera and *52% of known species. If an ecologically more natural area (wich expands the territory of México by about 1/3) is taken as reference, these figures rise respectively to *17% and *72%. If these figures are compared with existing information for other countries and regions of the world, it can be concluded that the extent of endemism in the flora of México is not as iarge as that of Australia, Madagascar or South Africa, but surpasses that of Cuba and of the California floristic province and is much iarger than those of many other parís of the world. The origin of this significant wealth of endemic organisms must be sought on the one hand in the existence of a fair number of regions that behave as true ecological islands and penínsulas within the territory of México, some of them extending over Iarge portions of the country, and on the other hand, in the events and environmentai conditions of the geological past. Particularly, it must be emphasized that during much of the Cenozoic era no terrestrial connection existed with South America and accordingly México bore the form of a península which, much like South Africa, penetrated in form of a wedge toward ciimatic conditions in Sharp contrast with those revailing on the wider part of the continent. Different types and aspects of endemism in Mexican flora are discussed and it is pointed out that an important proportion of very local and/or rare species can be recognized. The majority of endemics, however, do not belong to this group and in fact many of the most common and characteristic plants of the Mexican landscape belong to taxa of restricted distribution, including a Iarge number of weeds and some cultivars. Gypsophytes stand out among edaphic endemics and this roup seems to bear a long evolutionary history. A largó additional assemblage of paleoendemics can be distinguished, in part concentrated in areas which acted as refugia during the epochs of changing climates of the Tertiary and the Quaternary. A rough estimation indicates that endemism in the Mexican flora is most accentuated among shrubs and perennial terrestrial herbs, whereas lianas and aquatic plants show the lowest incidence. Among the Iarger families, Cactaceae, Rubiaceae and Compositae stand out with about 70% of endemic species, while Orchidaceae and Gramineae only revea! 35% and 25% respectively.A remarkable correlation can be observed between the proportion of endemic genera and the degree of ciimatic aridity. At the species ievel, however, températe and semí-humid areas are equally privileged in endemics. On the other hand in warm and humid regions endemism is poorly represented. Numbers of localities and regions are indicated, in which a significant concentraron of floristic endemism has been detecíed and in general terms it can be observed that endemic genera are much better representad in the northern haif of the country, whereas endemic species are more numerous on the Pacific slopes iban on the Atlantic. It is pointed out, however, that in most parts of the country, practically at any point, the flora of terrestrial and not excessively disturbed communities inciudes a high percentage of endemics. |
| format | Online |
| id | oai:oai.abm.ojs.inecol.mx:article-620 |
| institution | Acta Botanica Mexicana |
| language | spa |
| publishDate | 1991 |
| publisher | Instituto de Ecología, A.C. |
| record_format | ojs |
| spelling | oai:oai.abm.ojs.inecol.mx:article-6202023-02-02T00:03:25Z El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar Rzedowski, Jerzy This contribution is essentially a complement to the data and concepts exposed in a previous paper, devoted to the topic of diversity and origins of the Mexican phanerogamic flora. A part of the mentioned paper deais with the subject of endemism which, according to evidence and estimations, involves the family level and accounts for *10% of the genera and *52% of known species. If an ecologically more natural area (wich expands the territory of México by about 1/3) is taken as reference, these figures rise respectively to *17% and *72%. If these figures are compared with existing information for other countries and regions of the world, it can be concluded that the extent of endemism in the flora of México is not as iarge as that of Australia, Madagascar or South Africa, but surpasses that of Cuba and of the California floristic province and is much iarger than those of many other parís of the world. The origin of this significant wealth of endemic organisms must be sought on the one hand in the existence of a fair number of regions that behave as true ecological islands and penínsulas within the territory of México, some of them extending over Iarge portions of the country, and on the other hand, in the events and environmentai conditions of the geological past. Particularly, it must be emphasized that during much of the Cenozoic era no terrestrial connection existed with South America and accordingly México bore the form of a península which, much like South Africa, penetrated in form of a wedge toward ciimatic conditions in Sharp contrast with those revailing on the wider part of the continent. Different types and aspects of endemism in Mexican flora are discussed and it is pointed out that an important proportion of very local and/or rare species can be recognized. The majority of endemics, however, do not belong to this group and in fact many of the most common and characteristic plants of the Mexican landscape belong to taxa of restricted distribution, including a Iarge number of weeds and some cultivars. Gypsophytes stand out among edaphic endemics and this roup seems to bear a long evolutionary history. A largó additional assemblage of paleoendemics can be distinguished, in part concentrated in areas which acted as refugia during the epochs of changing climates of the Tertiary and the Quaternary. A rough estimation indicates that endemism in the Mexican flora is most accentuated among shrubs and perennial terrestrial herbs, whereas lianas and aquatic plants show the lowest incidence. Among the Iarger families, Cactaceae, Rubiaceae and Compositae stand out with about 70% of endemic species, while Orchidaceae and Gramineae only revea! 35% and 25% respectively.A remarkable correlation can be observed between the proportion of endemic genera and the degree of ciimatic aridity. At the species ievel, however, températe and semí-humid areas are equally privileged in endemics. On the other hand in warm and humid regions endemism is poorly represented. Numbers of localities and regions are indicated, in which a significant concentraron of floristic endemism has been detecíed and in general terms it can be observed that endemic genera are much better representad in the northern haif of the country, whereas endemic species are more numerous on the Pacific slopes iban on the Atlantic. It is pointed out, however, that in most parts of the country, practically at any point, the flora of terrestrial and not excessively disturbed communities inciudes a high percentage of endemics. Esta contribución constituye esencialmente una ampliación de algunos datos y conceptos vertidos en un trabajo anterior, dedicado al tema de la diversidad y de los orígenes de la flora fanerogámica de México. Una parte de dicho artículo se ocupó del endemismo, habiéndose determinado que éste involucra el nivel de familia, es del orden de *10% de los géneros y de *52% de las especies conocidas. Si se toma como marco de referencia una área más natural desde el punto de vista ecológico, que expandiera en cerca de un tercio el territorio del país, estos alores se elevarían a *17% y *72% respectivamente. Al comparar tales cifras con la información existente para algunos otros países y regiones del mundo, se concluye que la magnitud del endemismo en la flora de México no es tan grande como la de Australia, Madagascar y Sudáfrica, pero supera la de Cuba y la de la provincia florística de California y por muy amplio margen a otras muchas porciones de la Tierra.Las raíces de esta significativa riqueza en organismos de distribución restringida se ubican por una parte en la existencia de un buen número de regiones que funcionan como verdaderas islas y penínsulas ecológicas en el territorio de la República, varias de ellas de gran extensión, y por la otra en los eventos y condiciones ambientales del pasado geológico. En particular se enfatiza la circunstancia de que durante la mayor parte del Cenozoico, al no existir comunicación terrestre con Sudamérica, México tenía la forma de una península que, a semejanza de Sudáfrica, penetraba en forma de cuña hacia condiciones climáticas contrastantes con respecto a las que prevalecían en la parte ancha del continente. Al comentar los diferentes tipos y facetas del fenómeno en México, se puntualiza el hecho de que, si bien existe una importante proporción de especies de área muy local y/o raras, el grueso de los endemitas no comparte tales rasgos y en realidad muchas de las plantas más comunes y características del paisaje mexicano, incluyendo un buen número de malezas y algunos cultivares, corresponden a taxa de distribución restringida.Entre los endemismos edáficos destacan sobre todo las gipsófitas, muchas de las cuales parecen atestiguar una antigua historia evolutiva. Además de estas últimas existe un gran conjunto adicional de grupos paleoendémicos, en parte concentrados en áreas que han funcionado como refugios durante las épocas de clima cambiante del Terciario y Cuaternario.Una estimación gruesa indica que en la flora mexicana el endemismo es particularmente acentuado entre arbustos y plantas herbáceas terrestres perennes, en cambio los bejucos y los vegetales acuáticos son los más pobres en este sentido. En cuanto alas familias grandes, Cactaceae, Rubiaceae y Compositae llevan la primacía con alrededor de 70% de especies de distribución restringida, mientras que Orchidaceae y Gramineae sólo registran 35% y 25% respectivamente. Se observa una notable correlación entre la proporción de géneros endémicos y el grado de aridez climática. A nivel de especies, sin embargo, son igualmente privilegiadas en elementos de distribución restringida las áreas templado-semihúmedas. Las regiones cálido-húmedas, a su vez, son las más pobres en tales elementos. Se indican algunas localidades y regiones de México, en las cuales se ha detectado una significativa concentración de endemismos floristicos y en términos generales se observa que los géneros de esta categoría están mucho mejor representados en la mitad septentrional del país, en cambio las especies prevalecen más en las vertientes del Pacífico que en las atlánticas. Se enfatiza, sin embargo, la circunstancia de que en la mayor parte del país, prácticamente en cualquier punto, la flora de comunidades terrestres, no excesivamente perturbadas, contiene un elevado porcentaje de elementos de distribución restringida a sus límites territoriales. Instituto de Ecología, A.C. 1991-07-01 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion artículo evaluado por pares application/pdf https://abm.ojs.inecol.mx/index.php/abm/article/view/620 10.21829/abm15.1991.620 Acta Botanica Mexicana; No. 15 (1991); 47-64 Acta Botanica Mexicana; Núm. 15 (1991); 47-64 2448-7589 0187-7151 spa https://abm.ojs.inecol.mx/index.php/abm/article/view/620/786 Derechos de autor 2016 Acta Botanica Mexicana https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Rzedowski, Jerzy El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title | El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title_full | El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title_fullStr | El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title_full_unstemmed | El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title_short | El endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| title_sort | el endemismo en la flora fanerogámica mexicana: una apreciación analítica preliminar |
| url | https://abm.ojs.inecol.mx/index.php/abm/article/view/620 |
| work_keys_str_mv | AT rzedowskijerzy elendemismoenlaflorafanerogamicamexicanaunaapreciacionanaliticapreliminar |
