Recebido em 15/06/2002. Aceito em 08/04/2004 RESUMO -(Flora e aspectos auto-ecológicos de um encrave de cerrado na chapada do Araripe, Nordeste do Brasil). Este trabalho visa conhecer a composição e riqueza florística, os padrões fenológicos reprodutivos, as síndromes de dispersão e as formas de vida das espécies de uma disjunção de cerrado em clima semi-árido, na chapada do Araripe, Estado do Ceará. Foram encontradas 107 espécies e 41 famílias. Fabaceae, Myrtaceae, Poaceae, Apocynaceae, Euphorbiaceae e Malpighiaceae foram as mais ricas em espécies. Foi feita a distribuição geográfica de 47 espécies arbustivas e arbóreas em 27 listagens de cerrados brasileiros. Doze espécies apresentaram ampla distribuição geográfica e 13 foram registradas apenas neste trabalho. Cerca de 76% das espécies floresceram e frutificaram no período chuvoso. As síndromes de dispersão predominantes foram: zoocoria, autocoria e anemocoria. O espectro biológico foi predominantemente constituído por fanerófitos (50,7%), hemicriptófitos (14,9%) e caméfitos (13,1%). O cerrado estudado apresentou menor riqueza taxonômica que os cerrados contínuos e comportamento das fenofases reprodutivas, percentagem de síndromes de dispersão e formas de vida similares. Palavras-chave: cerrado, flora vascular, dispersão, fenologia, formas de vidaABSTRACT -(Flora and autecology's aspects of a disjunction cerrado at Araripe plateau, Northeastern Brazil). This study subject to investigate the floristic composition and richness, the reproductive phenological patterns, the dispersal syndromes and life forms of species of a disjunt cerrado in semiarid climate at Araripe plateau during a one year period. We found 107 species and 41 families. Fabaceae, Myrtaceae, Poaceae, Apocynaceae, Euphorbiaceae and Malpighiaceae showed the largest number of species. For 47 of the woody species found, we studied the geographical distribution based on 27 papers of the Brazilian cerrados. Twelve species are of widespread occurence in the cerrado, and 13 are restricted to the Araripe plateau. Zoocory, autocory, and anemocory are the predominant syndromes of dispersal. The predominant life forms were phanerophytes (50.7%), hemicriptophytes (14.9%) and camephytes (13.1%). The cerrado of Araripe have lower species richness than continous cerrados, but a similar pattern of reproductive phenology, dispersal syndromes and life forms in more humid zones.

Polyploidy is a key process in plant evolution, with the asexual formation of embryos representing a way through which polyploids can escape sterility. The association between polyploidy and polyembryony is known to occur in Bignoniaceae. In this study, we investigate polyembryony in four polyploid species of Anemopaegma: A. acutifolium, A. arvense, A. glaucum and A. scabriusculum as well as in one diploid species, A. album. Polyembryony was observed only in polyploid species. We used seed dissection and germination tests to compare the number of polyembryonic seeds. We tested how the pollen source influences the number of polyembryonic seeds and the number of embryos per seed and tested the correlation between the number of viable seeds per fruit and mean number of embryos per seed. The number of polyembryonic seeds observed by seed dissection was higher than the number of polyembryonic seeds determined by the germination test, with the number of embryos produced per seed being higher than the number of seedlings. The dissection of seeds of A. glaucum indicated that a higher number of polyembryonic seeds and a higher number of embryos were present in seeds from cross-pollination than in seeds from self-pollination. On the other hand, germination tests indicated that a higher number of polyembryonic seeds were present in fruits from self-pollination than from cross-pollination. The mean number of embryos per seed was not influenced by the number of viable seeds per fruit in fruits from open pollination. These results indicate a positive relationship between polyembryony and polyploidy in Anemopaegma.

In Myrtaceae, reports regarding the nuclear DNA content are scarce. The aim of this study is to present genome size data for fleshy-fruited Myrteae, and to test their relation with chromosome number and ploidy, the available data for cytoevolutionary studies in Myrtaceae. Thirty species out of ten genera were investigated for chromosome number and genome size using flow cytometry. Twenty-eight species were diploid with 2n = 2x = 22 and two species were tetraploid with 2n = 4x = 44. All genome sizes measured are new. Among the diploid species, a gradual and small variation in 2C-values (0.486 pg in Gomidesia schaueriana to 0.636 pg in Eugenia multicostata) was observed, whereas the tetraploid genomes of Psidium acutangulum and P. cattleianum had about twice as much DNA (1.053 and 1.167 pg, respectively). The total interspecific variation of C-values was 2.45-fold. The fleshy-fruited Myrteae have smaller holoploid genomes than the capsular-fruited Eucalypteae and Melaleuceae.

Summary Anemopaegma (Bignonieae, Bignoniaceae) includes 45 species distributed from Mexico to Northeastern Argentina. The genus is monophyletic and well supported by morphological and molecular characters. However, the delimitation of species within Anemopaegma is complex. In this study, we determined chromosome numbers and interphase nuclei structure for 5 shrubby species of Anemopaegma, 3 of which belong to the Anemopaegma arvense species complex. While most shrubby species analyzed were polyploids (2nϭ4xϭ80), polyploidy was not encountered among the climbing members of the genus. Furthermore, interphase nuclei was shown to vary among species. In particular, A. album was the only species that presented semi-reticulate interphase nuclei, while A. glaucum and A. scabriusculum presented areticulate nuclei. Anemopaegma acutifolium and A. arvense, on the other hand, presented an interphase nuclei structure that was intermediate between the areticulate and semi-reticulate types. Overall, our findings suggest that ploidy level may have had an important role in the diversification of the Neotropical genus Anemopaegma.

The shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora.