Bacterial Leaf Symbiosis in Angiosperms: Host Specificity without Co-Speciation

Bacterial leaf symbiosis is a unique and intimate interaction between bacteria and flowering plants, in which endosymbionts are organized in specialized leaf structures. Previously, bacterial leaf symbiosis has been described as a cyclic and obligate interaction in which the endosymbionts are vertically transmitted between plant generations and lack autonomous growth. Theoretically this allows for co-speciation between leaf nodulated plants and their endosymbionts. We sequenced the nodulated Burkholderia endosymbionts of 54 plant species from known leaf nodulated angiosperm genera, i.e. Ardisia, Pavetta, Psychotria and Sericanthe. Phylogenetic reconstruction of bacterial leaf symbionts and closely related free-living bacteria indicates the occurrence of multiple horizontal transfers of bacteria from the environment to leaf nodulated plant species. This rejects the hypothesis of a long co-speciation process between the bacterial endosymbionts and their host plants. Our results indicate a recent evolutionary process towards a stable and host specific interaction confirming the proposed maternal transmission mode of the endosymbionts through the seeds. Divergence estimates provide evidence for a relatively recent origin of bacterial leaf symbiosis, dating back to the Miocene (5–23 Mya). This geological epoch was characterized by cool and arid conditions, which may have triggered the origin of bacterial leaf symbiosis

Openness and Growth: Re-Examining Foreign Direct Investment, Trade and Output Linkages in Latin America

The openness-growth connection is still an open question in the empirical literature. Although some studies have found that openness has a positive impact on economic performance, others have seriously questioned the significance of this result. The main point that we try to emphasise in this paper is that openness involves more than just trade liberalisation. The increasing importance of international capital flows and especially foreign direct investment (FDI) seems to be another relevant component of outward oriented policies. Therefore, by using quarterly data from the late seventies to 2000, we investigate the effects of liberalisation in Mexico, Brazil and Argentina by taking into account trade and FDI growth links. The results suggest that it is important to consider both exports and FDI to ascertain the benefits associated to the outward oriented strategies followed by these countries.