TITLE

EL ENDEMISMO EN LA FLORA FANEROGAMICA MEXICANA: UNA APRECIACION ANALITICA PRELIMINARY

AUTHOR(S)
Rzedowski, Jerzy
PUB. DATE
September 1991
SOURCE
Acta Botanica Mexicana;sep1991, Issue 15, p47
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
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 deals 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 Mexico 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 Mexico is not as large as that of Australia, Madagascar or South Africa, but surpasses that of Cuba and of the California floristic province and is much larger than those of many other parts 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 peninsulas within the territory of Mexico, some of them extending over large portions of the country, and on the other hand, in the events and environmental 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 Mexico bore the form of a peninsula which, much like South Africa, penetrated in form of a wedge toward climatic conditions in sharp contrast with those prevailing 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 large number of weeds and some cultivars. Gypsophytes stand out among edaphic endemics and this group seems to bear a long evolutionary history. A large 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 larger families, Cactaceae, Rubiaceae and Compositae stand out with about 70% of endemic species, while Orchidaceae and Gramineae only reveal 35% and 25% respectively. A remarkable correlation can be observed between the proportion of endemic genera arid the degree of climatic aridity. At the species level, however, temperate and semi-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 concentration of floristic endemism has been detected and in general terms it can be observed that endemic genera are much better represented in the northern half of the country, whereas endemic species are more numerous on the Pacific slopes than 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 includes a high percentage of endemics.
ACCESSION #
21362581

 

Related Articles

  • Seed Plant Endemism on Hainan Island: A Framework for Conservation Actions. Francisco-Ortega, Javier; Wang, Zhong-Sheng; Wang, Fa-Guo; Xing, Fu-Wu; Liu, Hong; Xu, Han; Xu, Wei-Xiang; Luo, Yi-Bo; Song, Xi-Qiang; Gale, Stephan; Boufford, David; Maunder, Mike; An, Shu-Qing // Botanical Review;Sep2010, Vol. 76 Issue 3, p346 

    Hainan, the second largest island of China, has the most extensive and best preserved tropical forests of this country. A network of 68 protected areas (54 of them are terrestrial) provides in situ conservation for the unique ecosystems of the island. We: (1) discuss an updated check-list of...

  • Morphological and molecular phylogenetic context of the angiosperms: contrasting the ‘top-down’ and ‘bottom-up’ approaches used to infer the likely characteristics of the first flowers. Bateman, Richard M.; Hilton, Jason; Rudall, Paula J. // Journal of Experimental Botany;2006, Vol. 57 Issue 13, p3471 

    Recent attempts to address the long-debated ‘origin’ of the angiosperms depend on a phylogenetic framework derived from a matrix of taxa versus characters; most assume that empirical rigour is proportional to the size of the matrix. Sequence-based genotypic approaches increase the...

  • Phylogenomics and Coalescent Analyses Resolve Extant Seed Plant Relationships. Xi, Zhenxiang; Rest, Joshua S.; Davis, Charles C. // PLoS ONE;Nov2013, Vol. 8 Issue 11, p1 

    The extant seed plants include more than 260,000 species that belong to five main lineages: angiosperms, conifers, cycads, Ginkgo, and gnetophytes. Despite tremendous effort using molecular data, phylogenetic relationships among these five lineages remain uncertain. Here, we provide the first...

  • Costs and benefits of the mixed-mating system of Narcissus serotinus (Amaryllidaceae) in the conservation of small fragmented populations. Marques, Isabel; Draper, David; Iriondo, José María // Botany;2014, Vol. 92 Issue 2, p113 

    Small fragmented populations often exhibit reduced plant-pollinator interactions and scarce outcrossing opportunities. In this context, mixed-mating systems can be advantageous since selfing can provide reproductive assurance, but they may also carry relevant costs such as those involved in...

  • After a dozen years of progress the origin of angiosperms is still a great mystery. Frohlich, Michael W.; Chase, Mark W. // Nature;12/14/2007, Vol. 450 Issue 7173, p1184 

    Here we discuss recent advances surrounding the origin of angiosperms. Putatively primitive characters are now much better understood because of a vastly improved understanding of angiosperm phylogenetics, and recent discoveries of fossil flowers have provided an increasingly detailed picture of...

  • Spermatophyte Flora Distribution in Hubei Daqi Mountain Nature Reserve. Zhengyu LEI; Jingyong CAI; Tao BAI; Jianguo JIANG; Shaoming WANG // Asian Agricultural Research;Oct2013, Vol. 5 Issue 10, p88 

    A basic ingredient analysis of flora and geographic elements of plant genera and families in Daqi Mountain Nature Reserve was conducted through the field survey and specimen collection, based on the system investigation of plant flora, and an R/T ratio comparison between the flora in Daqi...

  • The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice. Haifeng Li; Wanqi Liang; Ruidong Jia; Changsong Yin; Jie Zong; Hongzhi Kong; Dabing Zhang // Cell Research;Mar2010, Vol. 20 Issue 3, p299 

    Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-like gene, OsMADS6, in specifying floral organ and meristem identities in rice (Oryza sativa...

  • Testing the recent theories for the origin of the hermaphrodite flower by comparison of the transcriptomes of gymnosperms and angiosperms. Tavares, Raquel; Cagnon, Mathilde; Negrutiu, Ioan; Mouchiroud, Dominque // BMC Evolutionary Biology;2010, Vol. 10, p240 

    Background: Different theories for the origin of the angiosperm hermaphrodite flower make different predictions concerning the overlap between the genes expressed in the male and female cones of gymnosperms and the genes expressed in the hermaphrodite flower of angiosperms. The Mostly Male (MM)...

  • Early Angiosperm Ecology: Evidence from the Albian-Cenomanian of Europe. COIFFARD, C.; GOMEZ, B.; THEVENARD, F.; KVAČEK, J. // Annals of Botany;Sep2006, Vol. 98 Issue 3, p495 

    • Background and Aims The mid-Cretaceous is a period of sudden turnover from gymnosperm to angiosperm-dominated floras. The aim was to investigate the fossil plant ecology in order to follow the spread of angiosperm taxa.• Methods Floristic lists and localities from the latest...

Share

Read the Article

Courtesy of VIRGINIA BEACH PUBLIC LIBRARY AND SYSTEM

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics