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29 Sep 2017
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Parallel diversifications of Cremastosperma and Mosannona (Annonaceae), tropical rainforest trees tracking Neogene upheaval of the South American continent

Unravelling the history of Neotropical plant diversification

Recommended by based on reviews by Thomas Couvreur and Hervé Sauquet

South American rainforests, particularly the Tropical Andes, have been recognized as the hottest spot of plant biodiversity on Earth, while facing unprecedented threats from human impact [1,2]. Considerable research efforts have recently focused on unravelling the complex geological, bioclimatic, and biogeographic history of the region [3,4]. While many studies have addressed the question of Neotropical plant diversification using parametric methods to reconstruct ancestral areas and patterns of dispersal, Pirie et al. [5] take a distinct, complementary approach. Based on a new, near-complete molecular phylogeny of two Neotropical genera of the flowering plant family Annonaceae, the authors modelled the ecological niche of each species and reconstructed the history of niche differentiation across the region. The main conclusion is that, despite similar current distributions and close phylogenetic distance, the two genera experienced rather distinct processes of diversification, responding differently to the major geological events marking the history of the region in the last 20 million years (Andean uplift, drainage of Lake Pebas, and closure of the Panama Isthmus).

As a researcher who has not personally worked on Neotropical biogeography, I found this paper captivating and especially enjoyed very much reading the Introduction, which sets out the questions very clearly. The strength of this paper is the near-complete diversity of species the authors were able to sample in each clade and the high-quality data compiled for the niche models. I would recommend this paper as a nice example of a phylogenetic study aimed at unravelling the detailed history of Neotropical plant diversification. While large, synthetic meta-analyses of many clades should continue to seek general patterns [4,6], careful studies restricted on smaller, but well controlled and sampled datasets such as this one are essential to really understand tropical plant diversification in all its complexity.


[1] Antonelli A, and Sanmartín I. 2011. Why are there so many plant species in the Neotropics? Taxon 60, 403–414.

[2] Mittermeier RA, Robles-Gil P, Hoffmann M, Pilgrim JD, Brooks TB, Mittermeier CG, Lamoreux JL and Fonseca GAB. 2004. Hotspots revisited: Earths biologically richest and most endangered ecoregions. CEMEX, Mexico City, Mexico 390pp

[3] Antonelli A, Nylander JAA, Persson C and Sanmartín I. 2009. Tracing the impact of the Andean uplift on Neotropical plant evolution. Proceedings of the National Academy of Science of the USA 106, 9749–9754. doi: 10.1073/pnas.0811421106

[4] Hoorn C, Wesselingh FP, ter Steege H, Bermudez MA, Mora A, Sevink J, Sanmartín I, Sanchez-Meseguer A, Anderson CL, Figueiredo JP, Jaramillo C, Riff D, Negri FR, Hooghiemstra H, Lundberg J, Stadler T, Särkinen T and Antonelli A. 2010. Amazonia through time: Andean uplift, climate change, landscape evolution, and biodiversity. Science 330, 927–931. doi: 10.1126/science.1194585

[5] Pirie MD, Maas PJM, Wilschut R, Melchers-Sharrott H and Chatrou L. 2017. Parallel diversifications of Cremastosperma and Mosannona (Annonaceae), tropical rainforest trees tracking Neogene upheaval of the South American continent. bioRxiv, 141127, ver. 3 of 28th Sept 2017. doi: 10.1101/141127

[6] Bacon CD, Silvestro D, Jaramillo C, Tilston Smith B, Chakrabartye P and Antonelli A. 2015. Biological evidence supports an early and complex emergence of the Isthmus of Panama. Proceedings of the National Academy of Science of the USA 112, 6110–6115. doi: 10.1073/pnas.1423853112

Parallel diversifications of Cremastosperma and Mosannona (Annonaceae), tropical rainforest trees tracking Neogene upheaval of the South American continentMichael D. Pirie, Paul J. M. Maas, Rutger A. Wilschut, Heleen Melchers-Sharrott & Lars W. ChatrouMuch of the immense present day biological diversity of Neotropical rainforests originated from the Miocene onwards, a period of geological and ecological upheaval in South America. We assess the impact of the Andean orogeny, drainage of lake Peba...Phylogenetics / Phylogenomics, Phylogeography & BiogeographyHervé Sauquet Hervé Sauquet, Thomas Couvreur2017-06-03 21:25:48 View
09 Feb 2018
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Phylodynamic assessment of intervention strategies for the West African Ebola virus outbreak

Simulating the effect of public health interventions using dated virus sequences and geographical data

Recommended by based on reviews by Christian Althaus, Chris Wymant and 1 anonymous reviewer

Perhaps because of its deadliness, the 2013-2016 Ebola Virus (EBOV) epidemics in West-Africa has led to unprecedented publication and sharing of full virus genome sequences. This was both rapid (90 full genomes were shared within weeks [1]) and important (more than 1500 full genomes have been released overall [2]). Furthermore, the availability of the metadata (especially GPS location) has led to depth analyses of the geographical spread of the epidemics [3].
In their work, Dellicour et al. [4] pursue earlier phylogeographical investigations in an original and yet simple approach to address questions of key public health importance. The originality of the approach is dual. First, from a technical standpoint, they capture the spread of infectious diseases in a continuous framework using a novel model that allows for rare long-distance dispersal events. Second, in a more classical discrete meta-population framework, they simulate the effect of public health interventions by pruning the phylogenetic tree and assessing how this affects key parameters. For instance, to simulate the effect of closing borders they remove subsets of the phylogeny that involved dispersal between countries and to simulate the effect of protecting a region by quarantine they remove all the leaves (i.e. the infections sampled) from this region. This phylogeny pruning is both original and simple. It is however limited because it currently assumes that policies are 100% effective and earlier modelling work on human influenza showed that long distance travel bans had to be implemented with >99% efficiency in order to slow epidemic growth from a time scale of days to weeks [5].
From a biological standpoint, Dellicour et al. [4] corroborate earlier findings that highly populated locations (>1,000,000 inhabitants) were crucial in explaining the magnitude of the epidemics but also show the importance of the transmission between the three capital cities. They also show that rare long-distance dispersing events of the virus are not key to explaining the magnitude of the epidemics (even though they assume 100% efficiency of suppressing long-distance event). Finally, thanks to their continuous model they estimate the speed of spread of the epidemics and are able to detect the effect of border closing on this speed.
Overall, this study [4], which involves state-of-the-art Bayesian inference methods of infection phylogenies using MCMC, stands out because of its effort to simulate public health interventions. It stands as an encouragement for the development of intervention models with increased realism and for even faster and larger virus sequence data sharing.


[1] Gire et al. 2014. Genomic surveillance elucidates Ebola virus origin and transmission during the 2014 outbreak. Science 345: 1369–1372. doi: 10.1126/science.1259657.
[2] Holmes EC, Dudas G, Rambaut A and Andersen KG. 2016. The evolution of Ebola virus: insights from the 2013-2016 epidemic. Nature 538: 193–200. doi: 10.1038/nature19790.
[3] Dudas et al. 2017. Virus genomes reveal factors that spread and sustained the Ebola epidemic. Nature 544: 309–315 (2017). doi: 10.1038/nature22040.
[4] Dellicour S, Baele G, Dudas G, Faria NR, Pybus OG, Suchard MA, Rambaud A and Lemey P. 2018. Phylodynamic assessment of intervention strategies for the West African Ebola virus outbreak. bioRxiv, 163691, ver. 3 peer-reviewed by Peer Community In Evolutionary Biology. doi: 10.1101/163691.
[5] Hollingsworth TD, Ferguson NM and Anderson RM. 2006. Will travel restrictions control the international spread of pandemic influenza? Nature Medicine 12, 497–499. doi: 10.1038/nm0506-497.

Phylodynamic assessment of intervention strategies for the West African Ebola virus outbreakSimon Dellicour, Guy Baele, Gytis Dudas, Nuno R. Faria, Oliver G. Pybus, Marc A. Suchard, Andrew Rambaut, Philippe Lemey<p>This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology ( The recent Ebola virus (EBOV) outbreak in West Africa witnessed considerable efforts to obtain viral genom...Phylogenetics / Phylogenomics, Phylogeography & BiogeographySamuel Alizon2017-09-30 13:49:57 View
13 Dec 2016
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Repeated replacements of an intrabacterial symbiont in the tripartite nested mealybug symbiosis

Obligate dependence does not preclude changing partners in a Russian dolls symbiotic system

Recommended by and

Symbiotic associations with bacterial partners have facilitated important evolutionary transitions in the life histories of eukaryotes. For instance, many insects have established long-term interactions with intracellular bacteria that provide them with essential nutrients lacking in their diet. However, despite the high level of interdependency among organisms involved in endosymbiotic systems, examples of symbiont replacements along the evolutionary history of insect hosts are numerous. In their paper, Husnik and McCutcheon [1] test the stability of symbiotic systems in a particularly imbricated Russian-doll type interaction, where one bacterium lives insides another bacterium, which itself lives inside insect cells. For their study, they chose representative species of mealybugs (Pseudococcidae), a species rich group of sap-feeding insects that hosts diverse and complex symbiotic systems. In species of the subfamily Pseudococcinae, data published so far suggest that the primary symbiont, a ß-proteobacterium named Tremblaya princeps, is supplemented by a second bacterial symbiont (a ϒ-proteobaterium) that lives within its cytoplasm; both participate to the metabolic pathways that provide essential amino acids and vitamins to their hosts. Here, Husnik and McCutcheon generate host and endosymbiont genome data for five phylogenetically divergent species of Pseudococcinae in order to better understand: 1) the evolutionary history of the symbiotic associations; 2) the metabolic roles of each partner, 3) the timing and origin of Horizontal Gene Transfers (HGT) between the hosts and their symbionts.
Their results show that all species harbour the primary and at least one secondary symbiont, whose intra-bacterial localization was verified using fluorescence in situ hybridization. In one species (Pseudococcus longispinus), Tremblaya even hosts two intracellular bacteria each with a large genome (even though it is not entirely clear whether these two symbionts are indeed found within Tremblaya). The obligate presence of an intra-bacterial symbiont is best explained by the loss in Tremblaya princeps of critical genes for translation that require “intracellular complementation”.
The most striking result concerns the identity of the intra-bacterial symbiont: genome sizes and structures of the “secondary” (intra-Tremblaya) symbionts vary drastically according to the host species. Phylogenetic analyses based on 80 conserved proteins, place all these ϒ-proteoacteria (except one of the P. longispinus symbionts) in a Sodalis allied clade. However, their relationships do not mirror the one of their hosts, and some of them show signs of very recent acquisition. Altogether these results provide strong evidence for several independent acquisitions of these highly intra-bacterial integrated symbionts. Scenarios for the history of the symbiosis are clearly laid out and discussed by the authors, and the scenario involving several independent replacements of a the intra-Tremblaya symbiont by diverse Sodalis-like bacteria appears the most likely given the data presented here. Selected biosynthetic functions are then mapped onto the host and symbiont genomes, showing the high level of interdependency of the partners for the synthesis of essential amino acids and vitamin. These maps also identify genes in the host genome that might have been acquired through HGT from bacteria and show that many of them are shared by all mealybug species sequenced so far. HGT events have thus predated the acquisitions of the current “intra-Tremblaya“ symbionts and have probably been acquired from previous symbiont infections.
Overall, this is a thorough study, using a diverse set of data and meticulous analyses that present convincing evidence that replacements of symbionts occurred repeatedly even in an imbricated symbiotic system. The phylogenetic analyses inferring the timing of HGTs also depict a highly dynamic history of gene losses and retentions in both host and symbiont genomes. Altogether these results demonstrate how the chimeric nature of individuals allows shuffling at different levels of organisation: organisms like symbionts can be replaced, genes can be exchanged among the partners of the chimera. The surprise is that constraints arising from interdependencies do not impede these exchanges. In the discussion, the authors present a very interesting parallel with the evolution of organelles: if the story presented here mirrors the one of mitochondria, it supports a gradualist view where mitochondria arrived late in the evolution of eukaryotic cells that already contained many bacterial genes resulting from HGT from previous symbionts.


[1] Husnik F., McCutcheon JP. 2016. Repeated replacements of an intrabacterial symbiont in the tripartite nested mealybug symbiosis. PNAS 113: E5416-E5424. doi: 10.1073/pnas.1603910113

Repeated replacements of an intrabacterial symbiont in the tripartite nested mealybug symbiosisHusnik F, McCutcheon JPStable endosymbiosis of a bacterium into a host cell promotes cellular and genomic complexity. The mealybug *Planococcus citri* has two bacterial endosymbionts with an unusual nested arrangement: the γ-proteobacterium *Moranella endobia* lives in ...Phylogenetics / Phylogenomics, Species interactionsEmmanuelle Jousselin2016-12-13 14:27:09 View
05 Jun 2018
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Pleistocene climate change and the formation of regional species pools

Recent assembly of European biogeographic species pool

Recommended by based on reviews by 3 anonymous reviewers

Biodiversity is unevenly distributed over time, space and the tree of life [1]. The fact that regions are richer than others as exemplified by the latitudinal diversity gradient has fascinated biologists as early as the first explorers travelled around the world [2]. Provincialism was one of the first general features of land biotic distributions noted by famous nineteenth century biologists like the phytogeographers J.D. Hooker and A. de Candolle, and the zoogeographers P.L. Sclater and A.R. Wallace [3]. When these explorers travelled among different places, they were struck by the differences in their biotas (e.g. [4]). The limited distributions of distinctive endemic forms suggested a history of local origin and constrained dispersal. Much biogeographic research has been devoted to identifying areas where groups of organisms originated and began their initial diversification [3]. Complementary efforts found evidence of both historical barriers that blocked the exchange of organisms between adjacent regions and historical corridors that allowed dispersal between currently isolated regions. The result has been a division of the Earth into a hierarchy of regions reflecting patterns of faunal and floral similarities (e.g. regions, subregions, provinces). Therefore a first ensuing question is: “how regional species pools have been assembled through time and space?”, which can be followed by a second question: “what are the ecological and evolutionary processes leading to differences in species richness among species pools?”.

To address these questions, the study of Calatayud et al. [5] developed and performed an interesting approach relying on phylogenetic data to identify regional and sub-regional pools of European beetles (using the iconic ground beetle genus Carabus). Specifically, they analysed the processes responsible for the assembly of species pools, by comparing the effects of dispersal barriers, niche similarities and phylogenetic history. They found that Europe could be divided in seven modules that group zoogeographically distinct regions with their associated faunas, and identified a transition zone matching the limit of the ice sheets at Last Glacial Maximum (19k years ago). Deviance of species co-occurrences across regions, across sub-regions and within each region was significantly explained, primarily by environmental niche similarity, and secondarily by spatial connectivity, except for northern regions. Interestingly, southern species pools are mostly separated by dispersal barriers, whereas northern species pools are mainly sorted by their environmental niches. Another important finding of Calatayud et al. [5] is that most phylogenetic structuration occurred during the Pleistocene, and they show how extreme recent historical events (Quaternary glaciations) can profoundly modify the composition and structure of geographic species pools, as opposed to studies showing the role of deep-time evolutionary processes.

The study of biogeographic assembly of species pools using phylogenies has never been more exciting and promising than today. Catalayud et al. [5] brings a nice study on the importance of Pleistocene glaciations along with geographical barriers and niche-based processes in structuring the regional faunas of European beetles. The successful development of powerful analytical tools in recent years, in conjunction with the rapid and massive increase in the availability of biological data (including molecular phylogenies, fossils, georeferrenced occurrences and ecological traits), will allow us to disentangle complex evolutionary histories. Although we still face important limitations in data availability and methodological shortcomings, the last decade has witnessed an improvement of our understanding of how historical and biotic triggers are intertwined on shaping the Earth’s stupendous biological diversity. I hope that the Catalayud et al.’s approach (and analytical framework) will help movement in that direction, and that it will provide interesting perspectives for future investigations of other regions. Applied to a European beetle radiation, they were able to tease apart the relative contributions of biotic (niche-based processes) versus abiotic (geographic barriers and climate change) factors.


[1] Rosenzweig ML. 1995. Species diversity in space and time. Cambridge: Cambridge University Press.
[2] Mittelbach GG, Schemske DW, Cornell HV, Allen AP, Brown JM et al. 2007. Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography. Ecology Letters. 10: 315–331. doi: 10.1111/j.1461-0248.2007.01020.x
[3] Lomolino MV, Riddle BR, Whittaker RJ and Brown JH. 2010. Biogeography, 4th edn. Sinauer Associates, Inc., Sunderland, MA.
[4] Wallace AR. 1876. The geographical distribution of animals: with a study of the relations of living and extinct faunas as elucidating the past changes of the earth's surface. New York: Harper and Brothers, Publishers.
[5] Calatayud J, Rodríguez MÁ, Molina-Venegas R, Leo M, Hórreo JL and Hortal J. 2018. Pleistocene climate change and the formation of regional species pools. bioRxiv 149617 ver. 4 peer-reviewed by Peer Community In Evolutionary Biology. doi: 10.1101/149617

Pleistocene climate change and the formation of regional species poolsJoaquín Calatayud, Miguel Á. Rodríguez, Rafael Molina-Venegas, María Leo, José Luís Hórreo, Joaquín Hortal<p>Despite the description of bioregions dates back from the origin of biogeography, the processes originating their associated species pools have been seldom studied. Ancient historical events are thought to play a fundamental role in configuring...Phylogeography & BiogeographyFabien Condamine2017-06-14 07:30:32 View
02 Jan 2019
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Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica

The colonization history of largely isolated habitats

Recommended by based on reviews by Simon Joly, Florian Boucher and 2 anonymous reviewers

The build-up of biodiversity is the result of in situ speciation and immigration, with the interplay between geographical distance and ecological suitability determining the probability of an organism to establish in a new area. The relative contribution of these factors have long interested biogeographers, in particular to explain the distribution of organisms adapted to habitats that remained largely isolated, such as the colonization of oceanic islands or land waters. The focus of this study is the formation of the afrotemperate flora; patches of temperate vegetation separated by thousands of kilometers in Africa, with high levels of endemism described in the Cape region, the Drakensberg range and the high mountains of tropical east Africa [1]. The floristic affinities between these centers of endemism have frequently been explored but the origin of many afrotemperate lineages remains enigmatic [2].
To identify the biogeographic history and drivers of biogeographic movements of the large afrotemperate genus Erica, the study of Pirie and colleagues [3] develops a robust hypothesis-testing approach relying on historical biogeographic models, phylogenetic and species occurrence data. Specifically, the authors test the directionality of migrations through Africa and address the general question on whether geographic proximity or climatic niche similarity constrained the colonization of the Afrotemperate by Erica. They found that the distribution of Erica species in Africa is the result of infrequent colonization events and that both geographic proximity and niche similarity limited geographic movements (with the model that incorporates both factors fitting the data better than null models). Unfortunately, the correlation between geographic and environmental distances found in this study limited the potential evaluation of their roles individually. They also found that species of Erica have dispersed from Europe to African regions, with the Drakensberg Mountains representing a colonization sink, rather than acting as a “stepping stone” between the Cape and Tropical African regions.
Advances in historical biogeography have been recently questioned by the difficulty to compare biogeographic models emphasizing long distance dispersal (DEC+J) versus vicariance (DEC) using statistical methods, such as AIC, as well as by questioning the own performance of DEC+J models [4]. Behind Pirie et al. main conclusions prevails the assumption that patterns of concerted long distance dispersal are more realistic than vicariance scenarios, such that a widespread afrotemperate flora that receded with climatic changes never existed. Pirie et al. do not explicitly test for this scenario based on the idea that these habitats remained largely isolated over time and our current knowledge on African paleoclimates and vegetation, emphasizing the value of arguments based on empirical (biological, geographic) considerations in model comparisons. I, however, appreciate from this study that the results of the biogeographic models emphasizing long distance dispersal, vicariance, and the unconstrained models are congruent with each other and presented together.
Pirie and colleagues [3] bring a nice study on the importance of long distance dispersal and biome shift in structuring the regional floras of Africa. They evidence outstanding examples of radiations in Erica resulting from single dispersal events over long distances and between ecologically dissimilar areas, which highlight the importance of niche evolution and biome shifts in the assembly of diversity. Although we still face important limitations in data availability and model realism, the last decade has witnessed an improvement of our understanding of how historical and environmental triggers are intertwined on shaping biological diversity. I found Pirie et al.’s approach (and analytical framework) very stimulating and hope that will help movement in that direction, providing interesting perspectives for future investigations of other regions.


[1] Linder, H.P. 1990. On the relationship between the vegetation and floras of the Afromontane and the Cape regions of Africa. Mitteilungen aus dem Institut für Allgemeine Botanik Hamburg 23b:777–790.
[2] Galley, C., Bytebier, B., Bellstedt, D. U., & Peter Linder, H. (2006). The Cape element in the Afrotemperate flora: from Cape to Cairo?. Proceedings of the Royal Society B: Biological Sciences, 274(1609), 535-543. doi: 10.1098/rspb.2006.0046
[3] Pirie, M. D., Kandziora, M., Nuerk, N. M., Le Maitre, N. C., de Kuppler, A. L. M., Gehrke, B., Oliver, E. G. H., & Bellstedt, D. U. (2018). Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica. bioRxiv, 290791. ver. 5 peer-reviewed and recommended by PCI Evol Biol. doi: 10.1101/290791
[4] Ree, R. H., & Sanmartín, I. (2018). Conceptual and statistical problems with the DEC+ J model of founder‐event speciation and its comparison with DEC via model selection. Journal of Biogeography, 45(4), 741-749. doi: 10.1111/jbi.13173

Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by EricaMichael D. Pirie, Martha Kandziora, Nicolai M. Nuerk, Nicholas C. Le Maitre, Ana Laura Mugrabi de Kuppler, Berit Gehrke, Edward G.H. Oliver, and Dirk U. Bellstedt<p>The coincidence of long distance dispersal and biome shift is assumed to be the result of a multifaceted interplay between geographical distance and ecological suitability of source and sink areas. Here, we test the influence of these factors o...Phylogeography & BiogeographyAndrea S. Meseguer2018-04-09 10:10:04 View
16 Mar 2023
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Phylogeographic breaks and how to find them: Separating vicariance from isolation by distance in a lizard with restricted dispersal

The difficult task of partitioning the effects of vicariance and isolation by distance in poor dispersers

Recommended by based on reviews by Kevin Sánchez and Aglaia (Cilia) Antoniou

Partitioning the effects of vicariance and low dispersal has been a long-standing problem in historical biogeography and phylogeography. While the term “vicariance” refers to divergence in allopatry, caused by some physical (geological, geographical) or climatic barriers (e.g. Rosen 1978), isolation by distance refers to the genetic differentiation of remote populations due to the physical distance separating them, when the latter surpasses the scale of dispersal (Wright 1938, 1940, 1943). 

Vicariance and dispersal have long been considered as separate forces leading to separate scenarii of speciation (e.g. reviewed in Hickerson and Meyer 2008). Nevertheless, these two processes are strongly linked, as, for example, vicariance theory relies on the assumption that ancestral lineages were once linked by dispersal prior to physical or climatic isolation (Rosen 1978). Low dispersal and vicariance are not mutually exclusive, and distinguishing these two processes in heterogeneous landscapes, especially for poor dispersers, remains therefore a severe challenge. For example, low dispersal (and/or small population size) can give rise to geographic patterns consistent with a phylogeographic break and be mistaken for geographic isolation (Irwin 2002, Kuo and Avise 2005).

The study of Rancilliac and colleagues (2023) is at the heart of this issue. It focuses on a nominal lizard species, the red-tailed spiny-footed lizard (Acanthodactylus erythrurus, Squamata: Lacertidae), which has a wide spatial distribution (from the Maghreb to the Iberian Peninsula), is found in a variety of different habitats, and has a wide range of morphological traits that do not always correlate with phylogeny. The main question is the following: have “the morphological and ecological diversification of this group been produced by vicariance and lineage diversification, or by local adaptation in the face of historical gene flow?” To tackle this question, the authors used sequence data from multiple mitochondrial and nuclear markers and a nested analysis workflow integrating phylogeography, multiple correspondence analyses and a relatively novel approach to IBD testing (Hausdorf & Henning, 2020). The latter is based on regression analysis and was shown to be less prone to error than the traditional (partial) Mantel test. 

While this set of methods allowed the partitioning of the effect of isolation by distance and vicariance in shaping contemporary genetic diversity in red-tailed spiny-footed lizards, some of the evolutionary history of this species complex remains blurred by ongoing gene flow and admixture, retention of ancestral polymorphism, or selection. The lack of congruence between mitochondrial and nuclear gene trees once again warns us that proposing evolutionary scenarii based on individual gene trees is a risky business. 


Hausdorf B, Hennig C (2020) Species delimitation and geography. Molecular Ecology Resources, 20, 950–960.

Hickerson MJ, Meyer CP (2008) Testing comparative phylogeographic models of marine vicariance and dispersal using a hierarchical Bayesian approach. BMC Evolutionary Biology, 8, 322.

Irwin DE (2002) Phylogeographic breaks without geographic barriers to gene flow. Evolution, 56, 2383–2394.

Kuo C-H, Avise JC (2005) Phylogeographic breaks in low-dispersal species: the emergence of concordance across gene trees. Genetica, 124, 179–186.

Rancilhac L, Miralles A, Geniez P, Mendez-Aranda D, Beddek M, Brito JC, Leblois R, Crochet P-A (2023) Phylogeographic breaks and how to find them: An empirical attempt at separating vicariance from isolation by distance in a lizard with restricted dispersal. bioRxiv, 2022.09.30.510256, ver. 4 peer-reviewed and recommended by Peer Community in Evolutionary Biology.

Rosen DE (1978) Vicariant Patterns and Historical Explanation in Biogeography. Systematic Biology, 27, 159–188.

Wright, S (1938) Size of population and breeding structure in relation to evolution. Science 87:430-431.

Wright S (1940) Breeding Structure of Populations in Relation to Speciation. The American Naturalist, 74, 232–248.

Wright S (1943) Isolation by distance. Genetics, 28, 114–138.

Phylogeographic breaks and how to find them: Separating vicariance from isolation by distance in a lizard with restricted dispersalLoïs Rancilhac, Aurélien Miralles, Philippe Geniez, Daniel Mendez-Arranda, Menad Beddek, José Carlos Brito, Raphaël Leblois, Pierre-André Crochet<p>Aim</p> <p>Discontinuity in the distribution of genetic diversity (often based on mtDNA) is usually interpreted as evidence for phylogeographic breaks, underlying vicariant units. However, a misleading signal of phylogeographic break can arise...Phylogeography & Biogeography, Population Genetics / Genomics, Speciation, Systematics / TaxonomyEric Pante Kevin Sánchez2022-10-05 13:11:28 View
26 Oct 2021
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Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North Africa

The evolutionary puzzle of the host-parasite-endosymbiont Russian doll for apples and aphids

Recommended by based on reviews by Pedro Simões and 1 anonymous reviewer

Each individual multicellular organism, each of our bodies, is a small universe. Every living surface -skin, cuticle, bark, mucosa- is the home place to milliards of bacteria, fungi and viruses. They constitute our microbiota. Some of them are essential for certain organisms. Other could not live without their hosts. For many species, the relationship between host and microbiota is so close that their histories are inseparable. The recognition of this biological inextricability has led to the notion of holobiont as the organism ensemble of host and microbiota. When individuals of a particular animal or plant species expand their geographical range, it is the holobiont that expands. And these processes of migration, expansion and colonization are often accompanied by evolutionary and ecological innovations in the interspecies relationships, at the macroscopic level (e.g. novel predator-prey or host-parasite interactions) and at the microscopic level (e.g. changes in the microbiota composition). From the human point of view, these novel interactions can be economically disastrous if they involve and threaten important crop or cattle species. And this is especially worrying in the present context of genetic standardization and intensification for mass-production on the one hand, and of climate change on the other.

With this perspective, the international team led by Amandine Cornille presents a study aiming at understanding the evolutionary history of the rosy apple aphid Dysaphis plantaginea Passerini, a major pest of the cultivated apple tree Malus domestica Borkh (1). The apple tree was probably domesticated in Central Asia, and later disseminated by humans over the world in different waves, and it was probably introduced in Europe by the Greeks. It is however unclear when and where D. plantaginea started parasitizing the cultivated apple tree. The ancestral D. plantaginea could have already infected the wild ancestor of current cultivated apple trees, but the aphid is not common in Central Asia. Alternatively, it may have gained access only later to the plant, possibly via a host jump, from Pyrus to Malus that may have occurred in Asia Minor or in the Caucasus. In the present preprint, Olvera-Vázquez and coworkers have analysed over 650 D. plantaginea colonies from 52 orchards in 13 countries, in Western, Central and Eastern Europe as well as in Morocco and the USA. The authors have analysed the genetic diversity in the sampled aphids, and have characterized as well the composition of the associated endosymbiont bacteria. The analyses detect substantial recent admixture, but allow to identify aphid subpopulations slightly but significantly differentiated and isolated by distance, especially those in Morocco and the USA, as well as to determine the presence of significant gene flow. This process of colonization associated to gene flow is most likely indirectly driven by human interactions. Very interestingly, the data show that this genetic diversity in the aphids is not reflected by a corresponding diversity in the associated microbiota, largely dominated by a few Buchnera aphidicola variants. In order to determine polarity in the evolutionary history of the aphid-tree association, the authors have applied approximate Bayesian computing and machine learning approaches. Albeit promising, the results are not sufficiently robust to assess directionality nor to confidently assess the origin of the crop pest. Despite the large effort here communicated, the authors point to the lack of sufficient data (in terms of aphid isolates), especially originating from Central Asia. Such increased sampling will need to be implemented in the future in order to elucidate not only the origin and the demographic history of the interaction between the cultivated apple tree and the rosy apple aphid. This knowledge is needed to understand how this crop pest struggles with the different seasonal and geographical selection pressures while maintaining high genetic diversity, conspicuous gene flow, differentiated populations and low endosymbiontic diversity.


  1. Olvera-Vazquez SG, Remoué C, Venon A, Rousselet A, Grandcolas O, Azrine M, Momont L, Galan M, Benoit L, David GM, Alhmedi A, Beliën T, Alins G, Franck P, Haddioui A, Jacobsen SK, Andreev R, Simon S, Sigsgaard L, Guibert E, Tournant L, Gazel F, Mody K, Khachtib Y, Roman A, Ursu TM, Zakharov IA, Belcram H, Harry M, Roth M, Simon JC, Oram S, Ricard JM, Agnello A, Beers EH, Engelman J, Balti I, Salhi-Hannachi A, Zhang H, Tu H, Mottet C, Barrès B, Degrave A, Razmjou J, Giraud T, Falque M, Dapena E, Miñarro M, Jardillier L, Deschamps P, Jousselin E, Cornille A (2021) Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North Africa. bioRxiv, 2020.12.11.421644, ver. 3 peer-reviewed and recommended by Peer Community in Evolutionary Biology.


Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North AfricaOlvera-Vazquez S.G., Remoué C., Venon A, Rousselet A., Grandcolas O., Azrine M., Momont L., Galan M., Benoit L., David G., Alhmedi A., Beliën T., Alins G., Franck P., Haddioui A., Jacobsen S.K., Andreev R., Simon S., Sigsgaard L., Guibert E., Tour...<p style="text-align: justify;">With frequent host shifts involving the colonization of new hosts across large geographical ranges, crop pests are good models for examining the mechanisms of rapid colonization. The microbial partners of pest insec...Phylogeography & Biogeography, Population Genetics / Genomics, Species interactionsIgnacio Bravo2020-12-11 19:22:54 View
09 Dec 2019
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Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails

The challenge of delineating species when they are hidden

Recommended by based on reviews by Pavel Matos, Christelle Fraïsse and Niklas Wahlberg

The science of naming species (taxonomy) has been renewed with the developments of molecular sequencing, digitization of museum specimens, and novel analytical tools. However, naming species can be highly subjective, sometimes considered as an art [1], because it is based on human-based criteria that vary among taxonomists. Nonetheless, taxonomists often argue that species names are hypotheses, which are therefore testable and refutable as new evidence is provided. This challenge comes with a more and more recognized and critical need for rigorously delineated species not only for producing accurate species inventories, but more importantly many questions in evolutionary biology (e.g. speciation), ecology (e.g. ecosystem structure and functioning), conservation biology (e.g. targeting priorities) or biogeography (e.g. diversification processes) depend in part on those species inventories and our knowledge of species [2-3]. Inaccurate species boundaries or diversity estimates may lead us to deliver biased answers to those questions, exactly as phylogenetic trees must be reconstructed rigorously and analyzed critically because they are a first step toward discussing broader questions [2-3]. In this context, biological diversity needs to be studied from multiple and complementary perspectives requiring the collaboration of morphologists, molecular biologists, biogeographers, and modelers [4-5]. Integrative taxonomy has been proposed as a solution to tackle the challenge of delimiting species [2], especially in highly diverse and undocumented groups of organisms.
In an elegant study that harbors all the characteristics of an integrative approach, Alda et al. [6] tackle the delimitation of species within the snail genus Galba (Lymnaeidae). Snails of this genus represent a peculiar case study for species delineation with a long and convoluted taxonomic history in which previous works recognized a number of species ranging from 4 to 30. The confusion is likely due to a loose morphology (labile shell features and high plasticity), which makes the identification and naming of species very unstable and likely subjective. An integrative taxonomic approach was needed. After two decades of taxon sampling and visits of type localities, the authors present an impressively dense taxon sampling at a global scale for the genus, which includes all described species. When it comes to delineate species, taxon sampling is often the key if we want to embrace the genetic and morphological diversity. Molecular data was obtained for several types of markers (microsatellites and DNA sequences for four genes), which were combined to morphology of shell and of internal organs, and to geographic distribution. All the data are thoroughly analyzed with cutting-edge methods starting from Bayesian phylogenetic reconstructions using multispecies coalescent models, followed by models of species delimitation based on the molecular specimen-level phylogeny, and then Bayesian divergence time estimates. They also used probabilistic models of ancestral state estimation to infer the ancestral phenotypic state of the Galba ancestors.
Their numerous phylogenetic and delimitation analyses allow to redefine the species boundaries that indicate that the genus Galba comprises six species. Interestingly, four of these species are morphologically cryptic and likely constitute species with extensive genetic diversity and widespread geographic distribution. The other two species have more geographically restricted distributions and exhibit an alternative morphology that is more phylogenetically derived than the cryptic one. Although further genomic studies would be required to strengthen some species status, this novel delimitation of Galba species has important implications for our understanding of convergence and morphological stasis, or the role for stabilizing selection in amphibious habitats; topics that are rarely addressed with invertebrate groups. For instance, in terms of macroevolutionary history, it is striking that an invertebrate clade of that age (22 million years ago) has only given birth to six species today. Including 30 (ancient taxonomy) or 6 (integrative taxonomy) species in a similar amount of evolutionary time does not tell us the same story when studying the diversification processes [7]. Here, Alda et al. [6] present a convincing case study that should foster similar studies following their approach, which will provide stimulating perspectives for testing the concepts of species and their effects on evolutionary biology.


[1] Ohl, M. (2018). The art of naming. MIT Press.
[2] Dayrat, B. (2005). Towards integrative taxonomy. Biological Journal of the Linnean Society, 85(3), 407–415. doi: 10.1111/j.1095-8312.2005.00503.x
[3] De Queiroz, K. (2007). Species concepts and species delimitation. Systematic Biology, 56(6), 879–886. doi: 10.1080/10635150701701083
[4] Padial, J. M., Miralles, A., De la Riva, I., and Vences, M. (2010). The integrative future of taxonomy. Frontiers in Zoology, 7(1), 16. doi: 10.1186/1742-9994-7-16
[5] Schlick-Steiner, B. C., Steiner, F. M., Seifert, B., Stauffer, C., Christian, E., and Crozier, R. H. (2010). Integrative taxonomy: A multisource approach to exploring biodiversity. Annual Review of Entomology, 55(1), 421–438. doi: 10.1146/annurev-ento-112408-085432
[6] Alda, P. et al. (2019). Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails. BioRxiv, 647867, v3 peer-reviewed and recommended by PCI Evolutionary Biology. doi: 10.1101/647867
[7] Ruane, S., Bryson, R. W., Pyron, R. A., and Burbrink, F. T. (2014). Coalescent species delimitation in milksnakes (Genus Lampropeltis) and impacts on phylogenetic comparative analyses. Systematic Biology, 63(2), 231–250. doi: 10.1093/sysbio/syt099

Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snailsPilar Alda, Manon Lounnas, Antonio Alejandro Vázquez, Rolando Ayaqui, Manuel Calvopina, Maritza Celi-Erazo, Robert Dillon, Luisa Carolina González Ramírez, Eric S. Loker, Jenny Muzzio-Aroca, Alberto Orlando Nárvaez, Oscar Noya, Andrés Esteban Pere...<p>Cryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in ...Phylogeography & Biogeography, Systematics / TaxonomyFabien Condamine Pavel Matos, Christelle Fraïsse2019-05-25 10:34:57 View
12 Nov 2020
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Limits and Convergence properties of the Sequentially Markovian Coalescent

Review and Assessment of Performance of Genomic Inference Methods based on the Sequentially Markovian Coalescent

Recommended by based on reviews by 3 anonymous reviewers

The human genome not only encodes for biological functions and for what makes us human, it also encodes the population history of our ancestors. Changes in past population sizes, for example, affect the distribution of times to the most recent common ancestor (tMRCA) of genomic segments, which in turn can be inferred by sophisticated modelling along the genome.
A key framework for such modelling of local tMRCA tracts along genomes is the Sequentially Markovian Coalescent (SMC) (McVean and Cardin 2005, Marjoram and Wall 2006) . The problem that the SMC solves is that the mosaic of local tMRCAs along the genome is unknown, both in their actual ages and in their positions along the genome. The SMC allows to effectively sum across all possibilities and handle the uncertainty probabilistically. Several important tools for inferring the demographic history of a population have been developed built on top of the SMC, including PSMC (Li and Durbin 2011), diCal (Sheehan et al 2013), MSMC (Schiffels and Durbin 2014), SMC++ (Terhorst et al 2017), eSMC (Sellinger et al. 2020) and others.
In this paper, Sellinger, Abu Awad and Tellier (2020) review these SMC-based methods and provide a coherent simulation design to comparatively assess their strengths and weaknesses in a variety of demographic scenarios (Sellinger, Abu Awad and Tellier 2020). In addition, they used these simulations to test how breaking various key assumptions in SMC methods affects estimates, such as constant recombination rates, or absence of false positive SNP calls.
As a result of this assessment, the authors not only provide practical guidance for researchers who want to use these methods, but also insights into how these methods work. For example, the paper carefully separates sources of error in these methods by observing what they call “Best-case convergence” of each method if the data behaves perfectly and separating that from how the method applies with actual data. This approach provides a deeper insight into the methods than what we could learn from application to genomic data alone.
In the age of genomics, computational tools and their development are key for researchers in this field. All the more important is it to provide the community with overviews, reviews and independent assessments of such tools. This is particularly important as sometimes the development of new methods lacks primary visibility due to relevant testing material being pushed to Supplementary Sections in papers due to space constraints. As SMC-based methods have become so widely used tools in genomics, I think the detailed assessment by Sellinger et al. (2020) is timely and relevant.
In conclusion, I recommend this paper because it bridges from a mere review of the different methods to an in-depth assessment of performance, thereby addressing both beginners in the field who just seek an initial overview, as well as experienced researchers who are interested in theoretical boundaries and assumptions of the different methods.


[1] Li, H., and Durbin, R. (2011). Inference of human population history from individual whole-genome sequences. Nature, 475(7357), 493-496. doi:
[2] Marjoram, P., and Wall, J. D. (2006). Fast"" coalescent"" simulation. BMC genetics, 7(1), 16. doi:
[3] McVean, G. A., and Cardin, N. J. (2005). Approximating the coalescent with recombination. Philosophical Transactions of the Royal Society B: Biological Sciences, 360(1459), 1387-1393. doi:
[4] Schiffels, S., and Durbin, R. (2014). Inferring human population size and separation history from multiple genome sequences. Nature genetics, 46(8), 919-925. doi:
[5] Sellinger, T. P. P., Awad, D. A., Moest, M., and Tellier, A. (2020). Inference of past demography, dormancy and self-fertilization rates from whole genome sequence data. PLoS Genetics, 16(4), e1008698. doi:
[6] Sellinger, T. P. P., Awad, D. A. and Tellier, A. (2020) Limits and Convergence properties of the Sequentially Markovian Coalescent. bioRxiv, 2020.07.23.217091, ver. 3 peer-reviewed and recommended by PCI Evolutionary Biology. doi:
[7] Sheehan, S., Harris, K., and Song, Y. S. (2013). Estimating variable effective population sizes from multiple genomes: a sequentially Markov conditional sampling distribution approach. Genetics, 194(3), 647-662. doi:
[8] Terhorst, J., Kamm, J. A., and Song, Y. S. (2017). Robust and scalable inference of population history from hundreds of unphased whole genomes. Nature genetics, 49(2), 303-309. doi:

Limits and Convergence properties of the Sequentially Markovian CoalescentThibaut Sellinger, Diala Abu Awad, Aurélien Tellier<p>Many methods based on the Sequentially Markovian Coalescent (SMC) have been and are being developed. These methods make use of genome sequence data to uncover population demographic history. More recently, new methods have extended the original...Population Genetics / GenomicsStephan SchiffelsAnonymous2020-07-25 10:54:48 View
04 Sep 2019
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The discernible and hidden effects of clonality on the genotypic and genetic states of populations: improving our estimation of clonal rates

How to estimate clonality from genetic data: use large samples and consider the biology of the species

Recommended by based on reviews by David Macaya-Sanz, Marcela Van Loo and 1 anonymous reviewer

Population geneticists frequently use the genetic and genotypic information of a population sample of individuals to make inferences on the reproductive system of a species. The detection of clones, i.e. individuals with the same genotype, can give information on whether there is clonal (vegetative) reproduction in the species. If clonality is detected, population geneticists typically use genotypic richness R, the number of distinct genotypes relative to the sample size, to estimate the rate of clonality c, which can be defined as the proportion of reproductive events that are clonal. Estimating the rate of clonality based on genotypic richness is however problematic because, to date, there is no analytical, nor simulation-based, characterization of this relationship. Furthermore, the effect of sampling on this relationship has never been critically examined.
The paper by Stoeckel, Porro and Arnaud-Haond [1] contributes significantly to the characterization of the relationship between rate of clonality and genetic and genotypic parameters in a population. The authors use an extensive individual-based simulation approach to assess the effects of rate of clonality (fully sexual, fully clonal and a range of intermediate levels of clonality, i.e., partial clonality) on genetic and genotypic parameters, considering variable population size, sample size, and numbers of generations elapsed since population initiation. Based on their simulations, they derive empirical formulae that link for the first time the rate of clonality to the genotypic richness and to the size distribution of clones (genotypic parameters), as well as to the population inbreeding coefficient and to a metric of linkage disequilibrium (genetic parameters). They then use the simulated data to assess the accuracy of their predictions. In a second phase, the authors use a Bayesian supervised learning algorithm to estimate rates of clonality from the simulated data.
The authors show that the relationship between rate of clonality and genotypic richness is not linear: genotypic richness decreases slowly with increasing clonality, a large drop in genotypic richness is only seen for rates of clonality ≥ 0.90. Genetic parameters are only sensitive to high rates of clonality. The practical implications of these results are that genotypic and genetic parameters can complement each other for the estimation of rates of clonality, with genotypic parameters most useful throughout most of the range of clonality values and with genetic parameters complementing them meaningfully at higher values. The most meaningful practical result of the paper is the demonstration of sampling bias on the estimation of genotypic richness. Commonly used population sample sizes in population genetics studies (n ≤ 50) lead to great overestimation of genotypic richness, which consequently leads to a severe underestimation of the rate of clonality in most systems, irrespectively of whether they have reached stationary equilibrium. Only in small populations, these effects are attenuated.
Biologists interested in the estimation of the rate of clonality will find this paper highly useful to design their sampling, and to choose their statistics for inference in a meaningful way. This paper also calls for a careful reappraisal of previously published works that infer rates of clonality from genetic data, and highlights the prime importance of complementary information on species life history data for a correct understanding of partial clonality.


[1] Stoeckel, S., Porro, B., and Arnaud-Haond, S. (2019). The discernible and hidden effects of clonality on the genotypic and genetic states of populations: improving our estimation of clonal rates. ArXiv:1902.09365 [q-Bio] v4 peer-reviewed and recommended by Peer Community in Evolutionary Biology. Retrieved from

The discernible and hidden effects of clonality on the genotypic and genetic states of populations: improving our estimation of clonal ratesSolenn Stoeckel, Barbara Porro, Sophie Arnaud-Haond<p>Partial clonality is widespread across the tree of life, but most population genetics models are conceived for exclusively clonal or sexual organisms. This gap hampers our understanding of the influence of clonality on evolutionary trajectories...Population Genetics / Genomics, Reproduction and SexMyriam Heuertz2019-02-28 10:10:56 View