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Abstract Background Some of the most difficult phylogenetic questions in evolutionary biology involve identification of the free-living relatives of parasitic organisms, particularly those of parasitic flowering plants. Consequently, the number of origins of parasitism and the phylogenetic distribution of the heterotrophic lifestyle among angiosperm lineages is unclear. Results Here we report the results of a phylogenetic analysis of 102 species of seed plants designed to infer the position of all haustorial parasitic angiosperm lineages using three mitochondrial genes: atp1, coxI, and matR. Overall, the mtDNA phylogeny agrees with independent studies in terms of non-parasitic plant relationships and reveals at least 11 independent origins of parasitism in angiosperms, eight of which consist entirely of holoparasitic species that lack photosynthetic ability. From these results, it can be inferred that modern-day parasites have disproportionately evolved in certain lineages and that the endoparasitic habit has arisen by convergence in four clades. In addition, reduced taxon, single gene analyses revealed multiple horizontal transfers of atp1 from host to parasite lineage, suggesting that parasites may be important vectors of horizontal gene transfer in angiosperms. Furthermore, in Pilostyles we show evidence for a recent host-to-parasite atp1 transfer based on a chimeric gene sequence that indicates multiple historical xenologous gene acquisitions have occurred in this endoparasite. Finally, the phylogenetic relationships inferred for parasites indicate that the origins of parasitism in angiosperms are strongly correlated with horizontal acquisitions of the invasive coxI group I intron. Conclusion Collectively, these results indicate that the parasitic lifestyle has arisen repeatedly in angiosperm evolutionary history and results in increasing parasite genomic chimerism over time.

Negative emotional memory bias is thought to play a causal role in the onset and maintenance of major depressive disorder. Rapid Eye Movement (REM) sleep has been shown to selectively consolidate negative emotional memories in healthy participants, and is greater in quantity and density in depressed patients. Slow-Wave Sleep (SWS) is typically associated with the consolidation of non-emotional memories. However, the effects of REM sleep and SWS on emotional memory consolidation have not been investigated in participants reporting depressive symptoms. In this study, we recruited two groups of healthy participants; one reporting mild-to-moderate depressive symptoms, and another reporting minimal depressive symptoms (assessed using the Beck Depression Inventory; BDI-II). Using a within-subjects split-night design, we measured consolidation of positive, neutral and negative images across a 3 h retention interval rich in either REM sleep or SWS. We found a significant sleep condition x image valence interaction in participants reporting depressive symptoms [F (2, 20) = 4.73, p = .021], but not participants reporting minimal depressive symptoms [F (2, 22) = .17, p = .845]. Participants reporting depressive symptoms consolidated significantly more neutral memories during SWS, and marginally more negative memories during REM sleep, than those reporting minimal depressive symptoms [t (21) = 2.44, p = .023; t (21) = 1.96, p = .064, respectively]. Our preliminary results demonstrate that REM sleep and SWS have differential effects on the consolidation of emotional and neutral images in participants reporting depressive symptoms. Further studies including larger sample sizes are required to investigate whether REM sleep alterations promote the development of negative memory bias in major depressive disorder., (Copyright © 2017 Elsevier Ltd. All rights reserved.)