ABSTRACT
A new legume species from a seasonally dry forest of the Western Río Balsas Depression, in the states of Guerrero and Michoacán, Mexico, Erythrostemon guevarafeferii, is herein described and illustrated. The new species shows morphological affinities with Erythrostemon hintonii, from which it is distinguished in having fewer leaflets per pinna, mature leaflets disposed toward the upper half of the pinnae rachises, long inflorescences on curved slender peduncles, abundant red glands on its flowers and inflorescences, and its fruit glabrous with red stipitate glands at maturity. A taxonomic key to the Río Balsas Depression species of Erythrostemon is included.
ResumenUna nueva especie de leguminosa de la Depresión Occidental del Río Balsas en los estados de Guerrero y Michoacán, Erythrostemon guevarafeferii, se describe e ilustra. La nueva especie muestra afinidades morfológicas con Erythrostemon hintonii, de la que se distingue por tener menos pinnas, folíolos maduros glabros dispuestos hacia la mitad superior de las pinnas, las inflorescencias largas sobre pedúnculos delgados que se curvan y flores con abundantes glándulas; legumbre glabra o con glándulas estipitadas rojas cuando esta madura. Se incluye una clave taxonómica de las especies de Erythrostemon que habitan en la Depresión del Río Balsas.
ABSTRACT
Tropical aquatic legumes of the genus Aeschynomene are unique in that they can be stem-nodulated by photosynthetic bradyrhizobia. Moreover, a recent study demonstrated that two Aeschynomene indica symbionts lack canonical nod genes, thereby raising questions about the distribution of such atypical symbioses among rhizobial-legume interactions. Population structure and genomic diversity were compared among stem-nodulating bradyrhizobia isolated from various Aeschynomene species of Central America and Tropical Africa. Phylogenetic analyses based on the recA gene and whole-genome amplified fragment length polymorphism (AFLP) fingerprints on 110 bacterial strains highlighted that all the photosynthetic strains form a separate cluster among bradyrhizobia, with no obvious structuring according to their geographical or plant origins. Nod-independent symbiosis was present in all sampling areas and seemed to be linked to Aeschynomene host species. However, it was not strictly dependent on photosynthetic ability, as exemplified by a newly identified cluster of strains that lacked canonical nod genes and efficiently stem-nodulated A. indica, but were not photosynthetic. Interestingly, the phenotypic properties of this new cluster of bacteria were reflected by their phylogenetical position, as being intermediate in distance between classical root-nodulatingBradyrhizobium spp. and photosynthetic ones. This result opens new prospects about stem-nodulating bradyrhizobial evolution.
