Population ecology of Banksia saxicola (Proteaceae)

Banksia saxicola A. S. George is a rare species with a disjunct distribution, at Wilsons Promontory National Park and the Grampians National Park, Victoria. Phenetic classification and ordination analyses using 13 leaf, inflorescence and infructescence characters, indicated that population differences are present but individual plants do not exclusively group into geographically isolated populations. Plants from Mt William (Grampians) are different from those at Wilsons Promontory, but those from Mt Rosea (Grampians) overlap with both of these populations. Leaf flavonoid analysis revealed minor differences between Grampians and Wilsons Prom ontory populations, with the latter being intermediate between B. integrifolia and Grampians B. saxicola. Germination of seed extracted from 1, 2-3 and >3 year old infructescences varied from 15-35% at 50 days. Seed from Wilsons Promontory had the highest germination rate. Cold stratification of seed only promoted germination of seed > 3 years of age from Mt William. Banksia saxicola, from Wilsons Promontory, had the highest level of serotiny, although more seed was stored per plant at Mt William due to greater fecundity. Granivory of canopy stored seed was highest at Wilsons Promontory. At the Grampians, B. saxicola is locally common, plants are generally healthy, and spontaneous seed release together with favourable environmental conditions, have allowed populations to regenerate in the absence of fire. At Wilsons Promontory, however, plants are less abundant, and with no regeneration in the last 19 years the population is aging. For continued existence of B. saxicola at Wilsons Promontory, conservation management strategies need to include burning

Morphometric study of Euchiton traversii complex (Gnaphalieae: Asteraceae)

A morphometric study was undertaken into alpine and subalpine species of Euchiton Cass. (Gnaphalieae: Asteraceae) in the Euchiton traversii species complex in south-eastern Australia and New Zealand. Phenetic analysis of both field-collected and herbarium specimens resolved the following six taxa included: Euchiton traversii (Hook.f.) Holub, Euchiton argentifolius (N.A.Wakef.) Anderb., Euchiton lateralis (C.J.Webb) Breitw. & J.M.Ward, Argyrotegium mackayi (Buchanan) J.M.Ward & Breitw., Argyrotegium fordianum (M.Gray) J.M.Ward & Breitw. and Argyrotegium poliochlorum (N.G.Walsh) J.M.Ward & Breitw. The results support the segregation of the genus Argyrotegium J.M.Ward & Breitw. from Euchiton. E. argentifolius is distinct from E. traversii, but conspecific with A. mackayi. E. lateralis is present in Tasmania as well as New Zealand. The distribution of Australian E. traversii is redefined to mainland alpine regions with a few rare occurrences in Tasmania. Australian E. traversii was shown to be similar to its New Zealand counterparts. Differences between E. lateralis and E. traversii were clarified. A. fordianum and A. poliochlorum are distinct species and their transfer to Argyrotegium is supported

Not so ancient: the extant crown group of Nothofagus represents a post-Gondwanan radiation

This study uses a molecular-dating approach to test hypotheses about the biogeography of Nothofagus. The molecular modelling suggests that the present-day subgenera and species date from a radiation that most likely commenced between 55 and 40 Myr ago. This rules out the possibility of a reconciled all-vicariance hypothesis for the biogeography of extant Nothofagus. However, the molecular dates for divergences between Australasian and South American taxa are consistent with the rifting of Australia and South America from Antarctica. The molecular dates further suggest a dispersal of subgenera Lophozonia and Fuscospora between Australia and New Zealand after the onset of the Antarctic Circumpolar Current and west wind drift. It appears likely that the New Caledonian lineage of subgenus Brassospora diverged from the New Guinean lineage elsewhere, prior to colonizing New Caledonia. The molecular approach strongly supports fossil-based estimates that Nothofagus diverged from the rest of Fagales more than 84 Myr ago. However, the mid-Cenozoic estimate for the diversification of the four extant subgenera conflicts with the palynological interpretation because pollen fossils, attributed to all four extant subgenera, were widespread across the Weddellian province of Gondwana about 71 Myr ago. The discrepancy between the pollen and molecular dates exists even when confidence intervals from several sources of error are taken into account. In contrast, the molecular age estimates are consistent with macrofossil dates. The incongruence between pollen fossils and molecular dates could be resolved if the early pollen types represent extinct lineages, with similar types later evolving independently in the extant lineages

Respostas de plantas de Schizolobium amazonicum [S. parahyba var. amazonicum] e Schizolobium parahyba [Schizolobium parahybum] à deficiência hídrica Responses of Schizolobium amazonicum [S. parahyba var. Amazonicum] and Schizolobium parahyba [Schizolobium parahybum] plants to water stress

Plantas jovens de S. amazonicum (paricá) e S. parahyba (guapuruvu) foram submetidas a dois ciclos de deficiência hídrica em casa de vegetação. O déficit hídrico induziu o aumento dos teores de aminoácidos solúveis totais, prolina, açúcares solúveis totais e K+ nos tecidos foliares, ocasionando o abaixamento do potencial osmótico em ambas as espécies. Porém, a análise dos resultados das curvas pressão-volume indica que as espécies respondem, de maneira diferente, ao estresse hídrico e o S. amazonicum apresenta maior capacidade de adaptação osmótica do que o S. parahyba.<br>Juvenile plants of S. amazonicum (paricá) and S. parahyba (guapuruvu) were subjected to two cycles of water stress in greenhouse conditions. The water deficit induced the increase in total soluble amino acids, proline, total soluble sugars and K+ contents in the leaf tissues, lowering osmotic potential values in both species. However, the analysis of the pressure-volume curve results suggests that the species respond differently to water stress, and that S. amazonicum presents greater capacity of osmotic adaptation than S. parahyba