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The timing of speciation events among warblers (small insectivorous woodland birds) in the Himalayas of India and in the White Mountains of New Hampshire, USA, is compared. Sequence divergence in the mitochondrial cytochrome b gene for 13 New World species in six genera averages 2.6%, which according to standard calibrations places most of the diversi¢cation in the early Pleistocene. In contrast, eight Himalayan species in the single genus Phylloscopus di¡er by an average of 10.7% in the same gene sequence. The New Hampshire warblers appear to have undergone a relatively recent burst of speciation and morphological evolution, but there is a detectable slowing of speciation rates (or increase in extinction rates) within the community towards the present. Other North American passerine groups that have been studied show no signs of explosive diversi¢cation in the Pleistocene. In these groups, pairs of sister species are often older than the entire warbler radiation. Boreal forest migrated south from very high latitudes towards the end of the Pliocene and this apparently created conditions ripe for explosive diversi¢cation among the warblers, but not for many other groups.

RESUMOA Caatinga, quarto domínio fitogeográfico brasileiro em número de espécies de angiospermas, é composta por um mosaico de florestas secas e vegetação arbustiva, com enclaves de florestas úmidas montanas e cerrados. Entretanto, é o segundo bioma brasileiro com menos áreas protegidas e com poucos estudos paleoambientais. Buscando contribuir para a discussão sobre a evolução deste bioma durante o Quaternário, foram escolhidos como indicadores os fitólitos. Por ser um trabalho pioneiro com esse tipo de proxy na região, foi necessário investigar primeiro se as plantas da Caatinga produzem bastante fitólitos e se os mesmos se preservam nos solos. Foram coletadas na Depressão Sertaneja Setentrional amostras de 33 plantas de 16 famílias e 5 amostras superficiais de solo (Assembleias Modernas) sob diferentes formações vegetais (AM1 Caatinga Arbustiva Aberta, AM 2 Floresta de Caatinga Média, AM3 Floresta de Caatinga Alta, AM4 Floresta Ciliar e AM5 Caatinga Arbustiva Densa), para servir de referência para futuros trabalhos com assembleias fósseis. Constatamos que as plantas da Caatinga produzem uma grande quantidade e variedade de fitólitos, predominando os traqueídeos, poliédricos, globular granulate e tricomas. Foi encontrado um bom grau de preservação dos fitólitos, variando nos tipos e na quantidade de acordo com a vegetação sobrejacente e a granulometria do solo. A assembleia com maior quantidade de fitólitos classificáveis foi AM3 e a com menor porcentagem foi a AM1. Os maiores estoques de fitólitos foram encontrados nas AM 3, 2 e 5, e os menores nas 1 e 4. Os morfotipos fitolíticos predominantes foram o globular granulate, globular echinate e elongate, o que é esperado nesse tipo de vegetação. Os índices fitolíticos D/P (0,6 a 15), Bi (50 a 78%), Iph (53 a 87%) e Pa/P (0,1 a 8,9) são compatíveis com os tipos de formação vegetal analisados. Os fitólitos se mostraram ferramentas promissoras para o melhor conhecimento da vegetação da região, bem como para estudos paleoambientais no bioma.Palavras-chave: fitólitos; semiárido; Depressão Sertaneja Setentrional. ABSTRACTThe Caatinga is the fourth Brazilian phytogeographical domain in number of angiosperm species, composed of a mosaic of dry forests and shrub vegetation, with enclaves of humid montane forests and savanna. Despite this, it is the second Brazilian biome in terms of least protected areas in its domain and has few paleoenvironmental studies. In order to contribute to the discussion on the evolution of this biome during the Quaternary, phytoliths were chosen as indicators. As this is a pioneering study for this type of proxy in the region, it was first necessary to investigate whether the plants of the Caatinga are producers of phytoliths and if they are preserved in the soils. Samples of 33 plants from 16 families and 5 superficial soil samples (Modern Assemblages) were collected in the Northern Sertaneja Depression (MA1 -Caatinga Open Shrubland, MA2 -Medium Caatinga Forest, MA3 -High Caatinga Forest, MA4 -Riparian Forest and MA5 -Dense Caatinga Shrubland)...

Cyperus is a Pantropical genus and the second richest in species in Cyperaceae. It encompasses about 550 species worldwide, with about 100 of these occurring in Brazil. Studies on the taxonomy of this genus are scarce and punctual in Brazil. In this study, the occurrence of species was surveyed through 27 collecting expeditions across different regions in the state of Rio Grande do Norte and analyzis of specimens of several herbaria. Twenty four species of Cyperus were identified, including six new occurrences and one new species, here described, but that will be properly published in other work. This study includes a dichotomous key for the identification of the species, as well as illustrations, descriptions, taxonomic comments and geographical distribution.