Rhamnus cathartica is an invasive shrub capable of high fecundity in North America. The physiology of R. cathartica has received little attention, but more is needed to understand traits that enhance its success in disturbed environments. Such data may help to predict invasiveness of closely related species such as Frangula caroliniana. We hypothesized that R. catharticawould have greater relat...

A phylogeny for all extant species of the heterosporous fern genus Azolla is presented here based on more than 5000 base pairs of DNA sequence data from six plastid loci (rbcL, atpB, rps4, trnL-trnF, trnG-trnR, and rps4-trnS). Our results are in agreement with other recent molecular phylogenetic hypotheses that support the monophyly of sections Azolla and Rhizosperma and the proposed relationsh...

In order to understand the physicochemical mechanisms that could explain the massive growth of Azolla arctica in the Eocene Arctic Ocean, we carried out a laboratory experiment in which we studied the interacting effects of rain and wind on the development of salinity stratification, both in the presence and in the absence of a dense Azolla cover. Additionally, we carried out a mesocosm experim...

Enormous quantities of the free-floating freshwater fern Azolla grew and reproduced in situ in the Arctic Ocean during the middle Eocene, as was demonstrated by microscopic analysis of microlaminated sediments recovered from the Lomonosov Ridge during Integrated Ocean Drilling Program (IODP) Expedition 302. The timing of the Azolla phase (approximately 48.5 Ma) coincides with the earliest signs...