The origins of the trypanosome genome strains Trypanosoma brucei brucei TREU 927, T. b. gambiense DAL 972, T. vivax Y486 and T. congolense IL3000

The genomes of several tsetse-transmitted African trypanosomes (Trypanosoma brucei brucei, T. b. gambiense, T. vivax, T. congolense) have been sequenced and are available to search online. The trypanosome strains chosen for the genome sequencing projects were selected because they had been well characterised in the laboratory, but all were isolated several decades ago. The purpose of this short review is to provide some background information on the origins and biological characterisation of these strains as a source of reference for future users of the genome data. With high throughput sequencing of many more trypanosome genomes in prospect, it is important to understand the phylogenetic relationships of the genome strains

The roles of vicariance and isolation by distance in shaping biotic diversification across an ancient archipelago: evidence from a Seychelles caecilian amphibian

© 2020 The Authors. Published by BMC. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1186/s12862-020-01673-wBackground Island systems offer excellent opportunities for studying the evolutionary histories of species by virtue of their restricted size and easily identifiable barriers to gene flow. However, most studies investigating evolutionary patterns and processes shaping biotic diversification have focused on more recent (emergent) rather than ancient oceanic archipelagos. Here, we focus on the granitic islands of the Seychelles, which are unusual among island systems because they have been isolated for a long time and are home to a monophyletic radiation of caecilian amphibians that has been separated from its extant sister lineage for ca. 65–62 Ma. We selected the most widespread Seychelles caecilian species, Hypogeophis rostratus, to investigate intraspecific morphological and genetic (mitochondrial and nuclear) variation across the archipelago (782 samples from nine islands) to identify patterns and test processes that shaped their evolutionary history within the Seychelles. Results Overall a signal of strong geographic structuring with distinct northern- and southern-island clusters were identified across all datasets. We suggest that these distinct groups have been isolated for ca. 1.26 Ma years without subsequent migration between them. Populations from the somewhat geographically isolated island of Frégate showed contrasting relationships to other islands based on genetic and morphological data, clustering alternatively with northern-island (genetic) and southern-island (morphological) populations. Conclusions Although variation in H. rostratus across the Seychelles is explained more by isolation-by-distance than by adaptation, the genetic-morphological incongruence for affinities of Frégate H. rostratus might be caused by local adaptation over-riding the signal from their vicariant history. Our findings highlight the need of integrative approaches to investigate fine-scale geographic structuring to uncover underlying diversity and to better understand evolutionary processes on ancient, continental islands.Funding for this research was provided by two grants from the National Science Foundation (BSR 88–17453, BSR 90–24505) [funding for fieldwork and lab work], two grants from the National Geographic Society (Grants 1977: 1633, 1743) [funding for fieldwork], three grants from the University of Michigan Office of the Vice President for Research, and a Research Partnership Award from the University of Michigan to RAN [morphology work]; a joint NHM-UCL IMPACT studentship [to fund STM’s PhD, lab work and fieldwork], Mohamed Bin Zayed Species Conservation Fund [funding for fieldwork] and Systematics Research Fund [funding for fieldwork] to STM; an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under Grant #P20GM103408 to LL [funding for lab work]; a NERC/BBSRC SynTax grant [funding for fieldwork and collaboration], and Darwin Initiative (grant 19–002) [funding for fieldwork, lab work and capacity building] with partners Bristol University, Islands Conservation Society, Seychelles Islands Foundation, Seychelles Ministry of Environment, Seychelles National Parks Authority, Seychelles Natural History Museum, University of Kent, Zoological Society of London to MW, DJG, JJD. The funding bodies played no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.Published onlin

Contrasting isotopic mantle sources for Proterozoic lamproites and kimberlites from the Cuddapah basin and eastern Dharwar craton: Implication for Proterozoic mantle heterogeneity beneath southern India

Kimberlites intruding the Precambrian basement towards the western margin of the Cuddapah basin near Anantapur (1090 Ma) and Mahbubnagar (1360 Ma) in Andhra Pradesh have initial Sr-87/Sr-86 between 0.70205 to 0.70734 and epsilon Nd between +0.5 to +4.68. Mesoproterozoic lamproites (1380 Ma) from the Cuddapah basin (Chelima and Zangamarajupalle) and its NE margin (Ramannapeta) have initial Sr-87/Sr-86 between 0.70520 and 0.7390 and epsilon Nd from -6.43 to -8.29. Combined Sr- and Nd-isotonic ratios suggest that lamproites were derived from "enriched" sources which have time-averaged higher Rb/Sr and lower Sm/Nd ratios than the Bulk Earth whereas kimberlites were derived from "depleted" source with lower Rb/Sr and higher Sm/Nd ratios. Calculated T-DM model ages suggest that the lamproite source enrichment (similar to 2 Ga) preceded that of kimberlites (similar to 1.37 Ga). Our work demonstrates the existence of isotopically contrasting upper mantle sources for Southern Indian kimberlites and lamproites and provides evidence for a lateral, isotopically heterogeneous mantle beneath the Cuddapah basin and eastern Dharwar craton. The significance of our results in the context of diamond exploration is also highlighted

Petrogenesis of Proterozoic lamproites and kimberlites from the Cuddapah Basin and Dharwar Craton, southern India

Proterozoic mafic potassic and ultrapotassic igneous rocks implaced at the Cuddapah Basin and Dharwar Craton of the southern Indian shield are among the earliest recorded on Earth. Lamproiles intrude the basin and its NE margin, whereas kimberlites intrude the craton to the west of the basin. Kimberlites occur in two spatially separate groups: the non-diamondiferous Mahbubnagar cluster that was emplaced at 1400 Ma and is of a similar age to the Cuddapah lamproites, and the predominantly diamondiferous Anantapur cluster, emplaced at ∼1100 Ma. Despite their Proterozoic ages, some of the kimberlites are petrographically fresh. Distinct variations are evident in the major and trace element concentrations ofthe diamondiferous and non-diamondiferous kimberlites. The latter have higher concentrations of Fe, Ti, Zr, Hf and Sc, and lower Ni contents and La/Sm ratios. All of the kimberlites have high La/Yb ratios (65-180) and positive εNdi values (0.5-4.5), which suggests that their source regions were metasomatized by small-fraction melts derived from the depleted upper mantle, shortly prior to kimberlite genesis. Cuddapah Basin lamproites have similar La/Yb ratios but much lower εNdi values (-6 to -7) and appear to have been derived from ancient metasomatized sub-continental lithospheric mantle. The Proterozoic ambient mantle is believed to have had a higher potential temperature than at the present day such that small amounts of lithospheric extension may account for the genesis of the kimberlites and lamproites of southern India without the need for a mantle plume. © Oxford University Press 2004; all rights reserved