Plant/Leaf traits and adaptive strategies of Cistus species to Mediterranean drought and insolation in southern Portugal

The effects of climate change can result in dramatic consequences in specific ecosystems such as montados that are seriously threatened by the absence of cork and holm oak (Quercus suber and Q. rotundifolia) natural regeneration. Shrubs of the genus Cistus, which are among the most important elements of encroached montados, seem to promote soil rehabilitation and enhance oak regeneration (Simões et al. 2009). In this context, we compared the life strategies and evaluated the potential ability of Cistus species to adapt to the increasing drought expected for the Mediterranean region, and thus their role on the sustainability of cork oak montados.

Genetic diversity and population structure of the sea lamprey (Petromyzon marinus L.) across its distributional range

Lampreys are a group of ancient vertebrates with 360 million years of existence. Throughout their evolution, they have acquired local adaptations to the colonized habitats, showing high plasticity and adaptive capacities. The sea lamprey (Petromyzon marinus L.) is a parasitic and anadromous species that occurs in both sides of the North Atlantic. The aims of this study were to analyse, using microsatellite markers, the genetic diversity and population structure of sea lamprey throughout its distributional range. Analyses demonstrated consistent signs of high population differentiation between European and North American samples (two-groups structure), most probably due to isolation by distance, but low differentiation among populations from the same coast. The apparent lack of homing in this species is in line with its high evolutive success, as homing may bring adults back to natal habitats that have changed, or that are intermittently unfavourable. Analyses also demonstrated higher levels of genetic diversity in North American samples; DIVERSIDADE GENÉTICA E ESTRUTURA POPULACIONAL DA LAMPREIA-MARINHA (PETROMYZON MARINUS L.) AO LONGO DA SUA ÁREA DE DISTRIBUIÇÃO Resumo: As lampreias são organismos ancestrais com cerca de 360 milhões de anos de existência. No decorrer da longa escala evolutiva têm vindo a adquirir adaptações aos locais que colonizaram, tendo uma forte capacidade evolutiva e adaptativa. A lampreia-marinha (Petromyzon marinus L.) é uma espécie parasita e anádroma que ocorre em ambas as costas do Atlântico Norte. Este estudo teve como principal objetivo estudar a diversidade genética e a estrutura populacional desta espécie ao longo da sua área de distribuição, através do uso de microssatélites. Os resultados demonstraram forte divergência entre populações das costas Este e Oeste do Atlântico Norte, provavelmente devido à elevada distância entre populações, mas pouca diferenciação entre populações da mesma costa. A ausência de homing nesta espécie terá contribuído para o seu sucesso evolutivo, uma vez que o homing pode levar indivíduos a reproduzirem-se em habitats que se tornaram desfavoráveis ou intermitentemente inapropriados. Os resultados demonstraram também uma maior variabilidade genética nas populações americanas.

Effects of dark or of red, blue or white light on germination of subterranean clover seeds

Dry or imbibed seeds of the negatively photoblastic burr burying subterranean clover cv. ‘Seaton Park’ were treated with dark or with red, blue or white light to evaluate the effects of light on seed germination. Dry seeds treated with constant white light, red light or blue light during 8 days and subsequently incubated in dark had final germination and duration of germination reduced, and the distribution of germination changed from highly asymmetric to symmetric respectively. Imbibing seeds incubated under constant blue or white light had final germination strongly reduced seven days after sowing (7.3% and 50.1% of the germination under dark) with significant differences between them. After transferral to dark, true complete recovery of germination of seeds treated with white light was observed 19 days after sowing, but only partial recovery in seeds treated with blue light. Results of dry and imbibed seeds are consistent with no activity of phytochromes, as expected in negatively photoblastic seeds. Results of dry seeds are seemingly contradictory because total germination data imply the inactivity of red and blue light photoreceptors, the opposite being implied by duration and shape of germination. A tentative hypothetical solution for the contradiction is presented. Results of imbibed seeds are fully consistent with cryptochromes but not with phototropins mediation of responses to light of seed germination in ‘Seaton Park’. The ecological and adaptive significance of such responses are discussed in the framework of light attenuation in soil and the requirement and ability of subterranean clover ‘Seaton Park’ to bury seeds.