Phylogeny and evolution of morphological structures in a highly diverse lineage of fruiting-body-forming amoebae, order Trichiales (Myxomycetes, Amoebozoa)

Early phylogenetic studies refuted most previous assumptions concerning the evolution of the morphological traits in the fruiting bodies of the order Trichiales and did not detect discernible evolutionary patterns, yet they were based on a limited number of species. We infer a new Trichiales phylogeny based on three independently inherited genetic regions (nuclear and mitochondrial), with a fair taxonomic sampling encompassing its broad diversity. Besides, we study the evolutionary history of some key morphological characters. According to the new phylogeny, most fruiting body traits in Trichiales systematics do not represent exclusive synapomorphies or autapomorphies for most monophyletic groups. Instead, the evolution of the features derived from the peridium, stalk, capillitium, and spores showed intricate patterns, and character state transitions occurred rather within- than between clades. Thus, we should consider other evolutionary scenarios instead of assuming the homology of some characters. According to these results, we propose a new classification of Trichiales, including the creation of a new genus, Gulielmina, the resurrection of the family Dictydiaethaliaceae and the genus Ophiotheca, and the proporsal of 13 new combinations for species of the genera Arcyria (1), Hemitrichia (2), Ophiotheca (2), Oligonema (4), Gulielmina (3), and Perichaena (1).

Evolutionary history of the buildup and breakdown of the heterostylous syndrome in Plumbaginaceae

The evolutionary pathways leading to the heterostylous syndrome are not well understood, and models concerning the origins of distyly differ in the order in which reciprocal herkogamy and self-incompatibility evolve. We investigated the evolution and breakdown of distyly in Plumbaginaceae, a family with considerable diversity of floral traits and reproductive systems. Using Bayesian Markov chain Monte Carlo analyses and stochastic character mapping, we examined the evolutionary assembly and breakdown of the heterostylous syndrome based on a well-resolved phylogeny of 121 species of Plumbaginaceae and six outgroup taxa using five nuclear and plastid gene regions. We used the distribution of reproductive traits and reconstructed ancestral characters across phylogenies to evaluate competing models for the evolution of distyly. The most likely common ancestor of Plumbaginaceae was self-incompatible and monomorphic for sex-organ arrangement and pollen-stigma characters. Character state reconstructions indicated that reciprocal herkogamy evolved at least three times and that shifts to selfing and apomixis occurred on multiple occasions. Our results provide comparative support for the early ideas of H. G. Baker on evolutionary pathways in Plumbaginaceae, and the more recent selfing avoidance model by D. & B. Charlesworth in which distyly evolves from self-incompatible ancestors.

The burrowing origin of modern snakes

Modern snakes probably originated as habitat specialists, but it controversial unclear whether they were ancestrally terrestrial burrowers or marine swimmers. We used x-ray virtual models of the inner ear to predict the habit of Dinilysia patagonica, a stem snake closely related to the origin of modern snakes. Previous work has shown that modern snakes perceive substrate vibrations via their inner ear. Our data show that D. patagonica and modern burrowing squamates share a unique spherical vestibule in the inner ear, as compared with swimmers and habitat generalists. We built predictive models for snake habit based on their vestibular shape, which estimated D. patagonica and the hypothetical ancestor of crown snakes as burrowers with high probabilities. This study provides an extensive comparative data set to test fossoriality quantitatively in stem snakes, and it shows that burrowing was predominant in the lineages leading to modern crown snakes.