Divergence Date Estimates Research Articles

Lizards of a different stripe: phylogenetics of the Pedioplanis undata species complex (Squamata, Lacertidae), with the description of two new species

The lacertid genus Pedioplanis is a moderately speciose group of small-bodied, cryptically-colored lizards found in arid habitats throughout southern Africa. Previous phylogenetic work on Pedioplanis has determined its placement within the broader context of the Lacertidae, but interspecific relations within the genus remain unsettled, particularly within the P. undata species complex, a group largely endemic to Namibia. We greatly expanded taxon sampling for members of the P. undata complex and other Pedioplanis, and generated molecular sequence data from 1,937 bp of mtDNA (ND2 and cytb) and 2,015 bp of nDNA (KIF24, PRLR, RAG-1) which were combined with sequences from GenBank resulting in a final dataset of 455 individuals. Both maximum likelihood and Bayesian analyses recover similar phylogenetic results and reveal the polyphyly of P. undata and P. inornata as presently construed. We confirm that P. husabensis is sister to the group comprising the P. undata complex plus the Angolan sister species P. huntleyi + P. haackei and demonstrate that P. benguelensis lies outside of this clade in its entirety. The complex itself comprises six species including P. undata, P. inornata, P. rubens, P. gaerdesi and two previously undescribed entities. Based on divergence date estimates, the P. undata species complex began diversifying in the late Miocene (5.3 ± 1.6 MYA) with the most recent cladogenetic events dating to the Pliocene (2.6 ± 1.0 MYA), making this assemblage relatively young compared to the genus Pedioplanis as a whole, the origin of which dates back to the mid-Miocene (13.5 ± 1.8 MYA). Using an integrative approach, we here describe Pedioplanis branchisp. nov. and Pedioplanis mayerisp. nov. representing northern populations previously assigned to P. inornata and P. undata, respectively. These entities were first flagged as possible new species by Berger-Dell’mour and Mayer over thirty years ago but were never formally described. The new species are supported chiefly by differences in coloration and by unique amino acid substitutions. We provide comprehensive maps depicting historical records based on museum specimens plus new records from this study for all members of the P. undata complex and P. husabensis. We suggest that climatic oscillations of the Upper Miocene and Pliocene-Pleistocene era in concert with the formation of biogeographic barriers have led to population isolation, gene flow restrictions and ultimately cladogenesis in the P. undata complex.

Phylogenomics of Brosimum (Moraceae) and allied genera, including a revised subgeneric system

AbstractWe present a phylogenomic study of Brosimum (Moraceae) and the allied genera Trymatococcus and Helianthostylis, with near‐complete taxon sampling. Distributed from Mexico and the Greater Antilles to the Amazon, this clade contains the underutilized crop ramón (bread nut) (Brosimum alicastrum) as well as other species valued for timber or medicinal uses. Target enrichment for 333 genes produced a well‐resolved phylogenetic tree and showed that Trymatococcus and Helianthostylis are nested within Brosimum. We present a revised subgeneric classification of Brosimum (19 spp.) based on phylogenetic and morphological considerations, including the reduction of Trymatococcus and Helianthostylis to subgenera. The monophyletic subgenera can be diagnosed based on stipule, pistillode, and cotyledon synapomorphies. Divergence date estimates suggest a Miocene origin for Brosimum, and ancestral area reconstruction indicated that all four subgenera originated and initially diversified in Amazonia before dispersing into other parts of South and Central America.

Phylogenetics of mud snakes (Squamata: Serpentes: Homalopsidae): A paradox of both undescribed diversity and taxonomic inflation

Mud snakes (Serpentes: Homalopsidae) are a family of 55 described, mainly aquatic, species primarily distributed throughout mainland Southeast Asia and the Indo-Australian Archipelago. Although they have been the focus of prior research, the basic relationships amongst genera and species remain poorly known. We used a combined mitochondrial and nuclear gene dataset to infer their phylogenetic relationships, using the highest levels of taxon and geographic sampling for any homalopsid phylogeny to date (62% generic and 62% species coverage; 140 individuals). Our results recover two reciprocally monophyletic groups: the fangless Brachyorrhos and its sister clade comprised of all rear-fanged homalopsids. Most genera and interspecific relationships were monophyletic and strongly supported, but intergeneric relationships and intraspecific population structure lack support. We find evidence of both undescribed diversity as well as cases of taxonomic inflation within several species. Tree-based species delimitation approaches (mPTP) support potential new candidate species as distinct from their conspecifics and also suggest that many named taxa may not be distinct species. Divergence date estimation and lineage-through-time analyses indicate lower levels of speciation in the Eocene, with a subsequent burst in diversification in the Miocene. Homalopsids may have diversified most rapidly during the Pliocene and Pleistocene, possibly in relation to tectonic shifts and sea-level fluctuations that took place in Sundaland and the Sahul Shelf. Our analyses provide new insights on homalopsid taxonomy, a baseline phylogeny for the family, and further biogeographic implications demonstrating how dynamic tectonics and Quaternary sea level changes may have shaped a widespread, diverse family of snakes.

Explosive radiation at the origin of Old World fruit bats (Chiroptera, Pteropodidae)

Pteropodidae constitutes one of the most diverse bat families. These bats have evolved a phytophagous diet, likely lost laryngeal echolocation capability, and attained the largest body sizes among bats. Previous phylogenetic studies suggested that the family might have experienced an explosive diversification at its origin. Here, we readdress this hypothesis using a macroevolutionary approach based on Bayesian statistics (BAMM), a sampling of 139 pteropodid species, and divergence date estimates obtained in a comprehensive phylogenetic study of Chiroptera with multiple fossil calibration points. We evaluated the effect of missing data and of a reduced outgroup by repeating the analyses across simulated complete phylogenies and across a comprehensive Yinpterochiroptera phylogeny, respectively. Additionally, we performed an alternative analysis to detect diversification-rate shifts through time, the birth-death-shift method. In contrast with a previous study, we found strong statistical signals of rapid diversification at the origin of Pteropodidae. BAMM also detected diversification-rate shifts (increases) at the origin of Pteropus, as well as at crown Hipposideridae and Rhinolophidae. The birth-death-shift method detected a shift at approximately 25 million years ago, the estimated crown ages of both Pteropodidae and Hipposideridae. Our results point to a complex dynamics in the evolution of bat families, likely related to key innovations, demographic factors, and environmental opportunity enhanced by global-scale climatic and geographic changes.

Bats are key hosts in the radiation of mammal-associated Bartonella bacteria.

Bats are notorious reservoirs of several zoonotic diseases and may be uniquely tolerant of infection among mammals. Broad sampling has revealed the importance of bats in the diversification and spread of viruses and eukaryotes to other animal hosts. Vector-borne bacteria of the genus Bartonella are prevalent and diverse in mammals globally and recent surveys have revealed numerous Bartonella lineages in bats. We assembled a sequence database of Bartonella strains, consisting of nine genetic loci from 209 previously characterized Bartonella lineages and 121 new cultured isolates from bats, and used these data to perform a comprehensive phylogenetic analysis of the Bartonella genus. This analysis included estimation of divergence dates using a molecular clock and ancestral reconstruction of host associations and geography. We estimate that Bartonella began infecting mammals 62 million years ago near the Cretaceous-Paleogene boundary. Additionally, the radiation of particular Bartonella clades correlate strongly to the timing of diversification and biogeography of mammalian hosts. Bats were inferred to be the ancestral hosts of all mammal-associated Bartonella and appear to be responsible for the early geographic expansion of the genus. We conclude that bats have had a deep influence on the evolutionary radiation of Bartonella bacteria and their spread to other mammalian orders. These results support a 'bat seeding' hypothesis that could explain similar evolutionary patterns in other mammalian parasite taxa. Application of such phylogenetic tools as we have used to other taxa may reveal the general importance of bats in the ancient diversification of mammalian parasites.

Out of the Hengduan Mountains: Molecular phylogeny and historical biogeography of the Asian water snake genus Trimerodytes (Squamata: Colubridae)

The Asian water snake genus Trimerodytes (formerly Sinonatrix) is endemic to East and Southeast Asia. Although several species have been included in various phylogenetic studies previously, the evolution and relationships among members of this genus as a whole remain unexplored. In this study, we report the sequencing two protein-coding mitochondrial gene fragments (MTCYB and ND2) and three nuclear genes (c-mos, NT3, and Rag1), reconstruct interspecific phylogeny, and explore biogeography for the genus Trimerodytes. Both Bayesian inference and maximum likelihood analyses consistently recover the monophyly of Trimerodytes with strong support, with T. yapingi the sister-group to the remaining species. The divergence date and ancestral area estimation suggest that Trimerodytes likely originated in Hengduan Mountains (eastern Tibetan Plateau) in western China at 23.93 Ma (95% HPD: 17.09–31.30), and intraspecific divergence began at about 4.23 Ma (95% HPD: 2.74–6.10). Analyses support the validity of T. yunnanensis.

Evolutionary origins of the SARS-CoV-2 sarbecovirus lineage responsible for the COVID-19 pandemic.

There are outstanding evolutionary questions on the recent emergence of human coronavirus SARS-CoV-2 including the role of reservoir species, the role of recombination and its time of divergence from animal viruses. We find that the sarbecoviruses-the viral subgenus containing SARS-CoV and SARS-CoV-2-undergo frequent recombination and exhibit spatially structured genetic diversity on a regional scale in China. SARS-CoV-2 itself is not a recombinant of any sarbecoviruses detected to date, and its receptor-binding motif, important for specificity to human ACE2 receptors, appears to be an ancestral trait shared with bat viruses and not one acquired recently via recombination. To employ phylogenetic dating methods, recombinant regions of a 68-genome sarbecovirus alignment were removed with three independent methods. Bayesian evolutionary rate and divergence date estimates were shown to be consistent for these three approaches and for two different prior specifications of evolutionary rates based on HCoV-OC43 and MERS-CoV. Divergence dates between SARS-CoV-2 and the bat sarbecovirus reservoir were estimated as 1948 (95% highest posterior density (HPD): 1879-1999), 1969 (95% HPD: 1930-2000) and 1982 (95% HPD: 1948-2009), indicating that the lineage giving rise to SARS-CoV-2 has been circulating unnoticed in bats for decades.

The origin of the endemic African grasshopper family Lentulidae (Orthoptera: Acridoidea) and its climate‐induced diversification

AbstractAimForest relicts in the mountainous regions of Africa represent one of the most diverse ecosystems on our planet, but the processes that have generated this remarkable diversity are still poorly understood. We estimate divergence times for an endemic, flightless grasshopper family and reconstruct a potential scenario for their colonization of Africa to test the hypothesis that the diversity of these mountain‐top endemics has been generated by multiple fragmentations and reconnections of tropical rain forests in parallel with climatic fluctuations.LocationSub‐Saharan Africa.TaxonLentulidae (Orthoptera).MethodsWe inferred the phylogeny of 7 genera and 28 species of the Lentulidae based on COI, 16S and Histone 3 sequences by using a Bayesian approach and we also estimated divergence dates. Based on our molecular phylogeny as well as the available information on the relationship of six additional genera and local occurrence records for 120 lentulid species across Africa, we reconstruct a potential colonization scenario for most species of this group.ResultsOur findings indicate that the forest‐bound lentulids of East Africa represent a monophyletic group that originates from South Africa. We show that major splits in the phylogeny of the Lentulidae coincide with three known fragmentation events of the African rain forests (27, 16 and 9 Ma) and that lentulids subsequently diversified rapidly in parallel with the aridification and strong geological activity in East Africa.Main conclusionsOur results corroborate the diversification patterns reported for several endemic African forest‐bound animal taxa at small scales and endemic African plant taxa at larger scales, highlighting the finding that much of the biodiversity presently found in the forest relicts of the Eastern Arc Mountains biodiversity hotspot has been generated by the interplay between humid periods that allowed the spread of forest‐bound lineages across Africa and periods of aridity‐driven isolation of forests and their associated fauna.

Phylogenomics indicates Amazonia as the major source of Neotropical swarm-founding social wasp diversity.

The Neotropical realm harbours unparalleled species richness and hence has challenged biologists to explain the cause of its high biotic diversity. Empirical studies to shed light on the processes underlying biological diversification in the Neotropics are focused mainly on vertebrates and plants, with little attention to the hyperdiverse insect fauna. Here, we use phylogenomic data from ultraconserved element (UCE) loci to reconstruct for the first time the evolutionary history of Neotropical swarm-founding social wasps (Hymenoptera, Vespidae, Epiponini). Using maximum likelihood, Bayesian, and species tree approaches we recovered a highly resolved phylogeny for epiponine wasps. Additionally, we estimated divergence dates, diversification rates, and the biogeographic history for these insects in order to test whether the group followed a 'museum' (speciation events occurred gradually over many millions of years) or 'cradle' (lineages evolved rapidly over a short time period) model of diversification. The origin of many genera and all sampled extant Epiponini species occurred during the Miocene and Plio-Pleistocene. Moreover, we detected no major shifts in the estimated diversification rate during the evolutionary history of Epiponini, suggesting a relatively gradual accumulation of lineages with low extinction rates. Several lines of evidence suggest that the Amazonian region played a major role in the evolution of Epiponini wasps. This spatio-temporal diversification pattern, most likely concurrent with climatic and landscape changes in the Neotropics during the Miocene and Pliocene, establishes the Amazonian region as the major source of Neotropical swarm-founding social wasp diversity.

A new species of Lepidodactylus (Squamata: Gekkonidae) from the mountains of northeastern Papua New Guinea: older than the hills.

We describe a new species of Lepidodactylus with an unusual distribution across scattered localities in three isolated mountain ranges of northeastern New Guinea. It is a member of the Lepidodactylus pumilus group and can be distinguished from all other Melanesian Lepidodactylus by aspects of size, scalation, digital webbing, and coloration. Previously published genetic and morphological data indicate that the new species is most similar to Lepidodactylus magnus, but it diverged from this species and other close relatives in the mid-Miocene or earlier, potentially on islands of the former South Caroline Arc. Estimated divergence dates between the new species and its sister taxon suggest that cladogenesis occurred before the uplift of the mountains that they currently inhabit. Recent systematic work also emphasizes an apparent pattern of increasing body size with elevation in species from the Lepidodactylus pumilus group from northeastern New Guinea, with the largest species occurring in montane habitats where few or no other gecko species are known. Both lines of evidence are consistent with an existing hypothesis that the Lepidodactylus pumilus group is an old insular lineage within which contemporary species diversity and distributions have been strongly shaped by low ability to effectively compete against other aggressive geckos in species-rich lowland rainforests. The role that biotic interactions may have played in shaping tropical gecko communities along elevational gradients warrants further investigation.

Patterns of coevolution between ambrosia beetle mycangia and the Ceratocystidaceae, with five new fungal genera and seven new species.

Ambrosia beetles farm specialised fungi in sapwood tunnels and use pocket-like organs called mycangia to carry propagules of the fungal cultivars. Ambrosia fungi selectively grow in mycangia, which is central to the symbiosis, but the history of coevolution between fungal cultivars and mycangia is poorly understood. The fungal family Ceratocystidaceae previously included three ambrosial genera (Ambrosiella, Meredithiella, and Phialophoropsis), each farmed by one of three distantly related tribes of ambrosia beetles with unique and relatively large mycangium types. Studies on the phylogenetic relationships and evolutionary histories of these three genera were expanded with the previously unstudied ambrosia fungi associated with a fourth mycangium type, that of the tribe Scolytoplatypodini. Using ITS rDNA barcoding and a concatenated dataset of six loci (28S rDNA, 18S rDNA, tef1-α, tub, mcm7, and rpl1), a comprehensive phylogeny of the family Ceratocystidaceae was developed, including Inodoromyces interjectus gen. & sp. nov., a non-ambrosial species that is closely related to the family. Three minor morphological variants of the pronotal disk mycangium of the Scolytoplatypodini were associated with ambrosia fungi in three respective clades of Ceratocystidaceae: Wolfgangiella gen. nov., Toshionella gen. nov., and Ambrosiella remansi sp. nov. Closely-related species that are not symbionts of ambrosia beetles are accommodated by Catunica adiposa gen. & comb. nov. and Solaloca norvegica gen. & comb. nov. The divergent morphology of the ambrosial genera and their phylogenetic placement among non-ambrosial genera suggest three domestication events in the Ceratocystidaceae. Estimated divergence dates for the ambrosia fungi and mycangia suggest that Scolytoplatypodini mycangia may have been the first to acquire Ceratocystidaceae symbionts and other ambrosial fungal genera emerged shortly after the evolution of new mycangium types. There is no evidence of reversion to a non-ambrosial lifestyle in the mycangial symbionts.

Rapid morphological evolution in placental mammals post-dates the origin of the crown group.

Resolving the timing and pattern of early placental mammal evolution has been confounded by conflict among divergence date estimates from interpretation of the fossil record and from molecular-clock dating studies. Despite both fossil occurrences and molecular sequences favouring a Cretaceous origin for Placentalia, no unambiguous Cretaceous placental mammal has been discovered. Investigating the differing patterns of evolution in morphological and molecular data reveals a possible explanation for this conflict. Here, we quantified the relationship between morphological and molecular rates of evolution. We show that, independent of divergence dates, morphological rates of evolution were slow relative to molecular evolution during the initial divergence of Placentalia, but substantially increased during the origination of the extant orders. The rapid radiation of placentals into a highly morphologically disparate Cenozoic fauna is thus not associated with the origin of Placentalia, but post-dates superordinal origins. These findings predict that early members of major placental groups may not be easily distinguishable from one another or from stem eutherians on the basis of skeleto-dental morphology. This result supports a Late Cretaceous origin of crown placentals with an ordinal-level adaptive radiation in the early Paleocene, with the high relative rate permitting rapid anatomical change without requiring unreasonably fast molecular evolutionary rates. The lack of definitive Cretaceous placental mammals may be a result of morphological similarity among stem and early crown eutherians, providing an avenue for reconciling the fossil record with molecular divergence estimates for Placentalia.

Phylogenetic relationships in two African Cedreloideae tree genera (Meliaceae) reveal multiple rain/dry forest transitions

Resolving phylogenetic relationships allows the investigation of how species diversity has evolved in various ecosystems. The genera Entandrophragma and Khaya consist of tree species distributed in different African biomes (lowland rain forest, dry forest and savanna, montane forest), and are suitable to examine how (single or multiple events) and when the processes of diversification led to biome transitions. Based on the sequencing of plastome (pDNA: c. 160,000 bp), ribosomal DNA (rDNA: c. 5300 bp), and habitat characteristic data for each species, we have: (i) reconstructed phylogenetic relationships between species and estimated the divergence period between the main lineages, and (ii) reconstructed ancestral states regarding biome preferences. The phylogenetic trees obtained with both markers support monophyly of the five sections of Entandrophragma previously defined based on fruit and floral characters. Nevertheless, the position of some species from the pDNA and rDNA tree topologies varied within sections. In Khaya, pDNA and rDNA show very divergent topologies, possibly due to a more recent diversification involving incomplete lineage sorting and/or recurrent hybridization events. Khaya diversified during the Pliocene and Pleistocene according to both markers; whereas, according to rDNA data, the Entandrophragma sections diverged during the early Miocene and species within sections diverged from the late Miocene to the Pleistocene. Divergence date estimates tended to be more recent using pDNA data. Biome transitions could not be reconstructed in Khaya as the species tree remains unresolved. Contrarily, three independent biome transitions were inferred in Entandrophragma. The first transition from rain to dry forests occurred during the Miocene and two other transitions were inferred during the Pleistocene, one from rain forest to dry forest and another from rain forest to mountain forest. Overall, we demonstrate that multiple biome transitions occurred, starting from a rain forest biome, possibly reflecting the global trend of aridification of Africa throughout the Cenozoic.

Reconstructing the Evolution of Giant Extinct Kangaroos: Comparing the Utility of DNA, Morphology, and Total Evidence.

Combined "total evidence" analysis of molecular and morphological data offers the opportunity to objectively merge fossils into the tree of life, and challenges the primacy of solely DNA based phylogenetic and dating inference, even among modern taxa. To investigate the relative utility of DNA, morphology, and total evidence for evolutionary inference, we sequenced the first near-complete mitochondrial genomes from extinct Australian megafauna: a 40-50 thousand year old giant short-faced kangaroo (Simosthenurus occidentalis) and giant wallaby (Protemnodon anak). We analyzed the ancient DNA and fossil data alongside comparable data from extant species to infer phylogeny, divergence times, and ancestral body mass among macropods (kangaroos and wallabies). Our results confirm a close relationship between Protemnodon and the iconic kangaroo genus complex "Macropus", and unite the giant Simothenurus with the hare-sized Lagostrophus fasciatus (banded hare-wallaby), suggesting that the latter is the closest living link to the once diverse sthenurine kangaroo radiation. We find that large body size evolved multiple times among kangaroos, coincident with expansion of open woodland habitats beginning in the Late Miocene. In addition, our results suggest that morphological data mislead macropod phylogeny reconstruction and in turn can distort total evidence estimation of divergence dates. However, a novel result with potentially broad application is that the accuracy and precision of reconstructing ancestral body mass was improved by tracing body mass on morphological branch lengths. This is likely due to positive allometric correlation between morphological and body size variation-a relationship that may be masked or even misleadingly inverted with the temporal or molecular branch lengths that typically underpin ancestral body size reconstruction. Our study supports complementary roles for DNA and morphology in evolutionary inference, and opens a new window into the evolution of Australia's unique marsupial fauna.

Historical connections among river basins and climatic changes explain the biogeographic history of a water rat

BackgroundThe water rat Nectomys squamipes (Cricetidae: Sigmodontinae) is a semiaquatic rodent from eastern South America that shows shallow genetic structure across space, according to some studies. We tested the influence of hydrography and climatic changes on the genetic and phylogeographic structure of this semiaquatic small mammal.MethodsDNA sequences of two mitochondrial genetic markers (Cyt b and D-loop) and six microsatellite loci from water rats were collected at 50 localities in five river basins in the Atlantic Forest along the eastern coast of South America. We evaluated the genetic structure within and among river basins, and we estimated divergence dates. Species distribution models for the present and past were built to identify possible gene flow paths.ResultsMitochondrial data and species distribution models showed coherent results. Microsatellite loci showed a more complex pattern of genetic differentiation. The diversification of N. squamipes haplotypes occurred during the Pleistocene and the river basin cannot explain most of the genetic structure. We found evidence of population expansion during the last glacial maximum, and gene flow paths indicate historical connections among rivers in the Atlantic Forest.DiscussionHistorical connections among rivers in the Atlantic Forest may have allowed N. squamipes to disperse farther across and within basins, leading to shallow genetic structure. Population expansions and gene flow through the emerged continental shelf during glacial period support the Atlantis forest hypothesis, thus challenging the forest refuge hypothesis.

Molecular phylogeny and diversification of Malagasy bright-eyed tree frogs (Mantellidae: Boophis)

We investigate the molecular phylogeny of Boophis, a group of arboreal frogs from the Malagasy-Comoroan family Mantellidae. Based on newly acquired DNA sequences of five mitochondrial and five nuclear markers (7444 base pairs), we infer a phylogeny of Boophis with complete species-level taxon sampling. We reconstruct the phylogeny using Bayesian inference and maximum likelihood and estimate divergence dates for the major clades of the genus. The phylogenetic analyses together support the monophyly of the two subgenera (Sahona and Boophis), and provide strong support for most previously identified species groups, except that the B. ulftunni group is nested within the B. majori group. We also erect a new species group related to the B. mandraka group, the B. blommersae group, composed of small-sized, brown stream-breeding frogs previously included within the B. majori group. Finally, we use the resulting phylogeny to illustrate striking examples of repeated evolution of coloration and ventral transparency and address the biogeographic history and broad pattern of species diversification in the genus. Ancestral area reconstructions provide evidence that Boophis diversified within the Eastern highland forests of Madagascar, and we suggest that adaptation to these highland areas was important in their diversification.

Dating phototrophic microbial lineages with reticulate gene histories.

Phototrophic bacteria are among the most biogeochemically significant organisms on Earth and are physiologically related through the use of reaction centers to collect photons for energy metabolism. However, the major phototrophic lineages are not closely related to one another in bacterial phylogeny, and the origins of their respective photosynthetic machinery remain obscured by time and low sequence similarity. To better understand the co‐evolution of Cyanobacteria and other ancient anoxygenic phototrophic lineages with respect to geologic time, we designed and implemented a variety of molecular clocks that use horizontal gene transfer (HGT) as additional, relative constraints. These HGT constraints improve the precision of phototroph divergence date estimates and indicate that stem green non‐sulfur bacteria are likely the oldest phototrophic lineage. Concurrently, crown Cyanobacteria age estimates ranged from 2.2 Ga to 2.7 Ga, with stem Cyanobacteria diverging ~2.8 Ga. These estimates provide a several hundred Ma window for oxygenic photosynthesis to evolve prior to the Great Oxidation Event (GOE) ~2.3 Ga. In all models, crown green sulfur bacteria diversify after the loss of the banded iron formations from the sedimentary record (~1.8 Ga) and may indicate the expansion of the lineage into a new ecological niche following the GOE. Our date estimates also provide a timeline to investigate the temporal feasibility of different photosystem HGT events between phototrophic lineages. Using this approach, we infer that stem Cyanobacteria are unlikely to be the recipient of an HGT of photosystem I proteins from green sulfur bacteria but could still have been either the HGT donor or the recipient of photosystem II proteins with green non‐sulfur bacteria, prior to the GOE. Together, these results indicate that HGT‐constrained molecular clocks are useful tools for the evaluation of various geological and evolutionary hypotheses, using the evolutionary histories of both genes and organismal lineages.

A Kolmogorov-Smirnov test for the molecular clock based on Bayesian ensembles of phylogenies.

Divergence date estimates are central to understand evolutionary processes and depend, in the case of molecular phylogenies, on tests of molecular clocks. Here we propose two non-parametric tests of strict and relaxed molecular clocks built upon a framework that uses the empirical cumulative distribution (ECD) of branch lengths obtained from an ensemble of Bayesian trees and well known non-parametric (one-sample and two-sample) Kolmogorov-Smirnov (KS) goodness-of-fit test. In the strict clock case, the method consists in using the one-sample Kolmogorov-Smirnov (KS) test to directly test if the phylogeny is clock-like, in other words, if it follows a Poisson law. The ECD is computed from the discretized branch lengths and the parameter λ of the expected Poisson distribution is calculated as the average branch length over the ensemble of trees. To compensate for the auto-correlation in the ensemble of trees and pseudo-replication we take advantage of thinning and effective sample size, two features provided by Bayesian inference MCMC samplers. Finally, it is observed that tree topologies with very long or very short branches lead to Poisson mixtures and in this case we propose the use of the two-sample KS test with samples from two continuous branch length distributions, one obtained from an ensemble of clock-constrained trees and the other from an ensemble of unconstrained trees. Moreover, in this second form the test can also be applied to test for relaxed clock models. The use of a statistically equivalent ensemble of phylogenies to obtain the branch lengths ECD, instead of one consensus tree, yields considerable reduction of the effects of small sample size and provides a gain of power.

The Pangean journey of ‘south forestflies’ (Insecta: Plecoptera) revealed by their first fossils

The ‘south forestflies’ (Notonemouridae) are known from the southern hemisphere. However, their successive closest sister-groups all occur in the northern hemisphere, suggesting a north-to-south migration at some stage of their evolution. No reliable fossil remains that would provide age constraints for this event have been identified. According to previously published divergence date estimates, the group arose recently (65–98 Ma), implying a late transcontinental dispersal. Here, we describe a new fossil insect, Paranotonemoura zwicki Cui & Béthoux sp. nov. (Daohugou, China), and revise Paranotonemoura fidelis Sinitshenkova, 1987 comb. nov. (Bakhar, Mongolia), both of Jurassic age (c. 165 Ma). Based on the study of their wing venation pattern and of that of extant ‘south forestflies’, we demonstrate that the fossils belong to this group, and therefore are its first fossils. Our discovery demonstrates that the lineage is much more ancient than previously estimated. Plausible scenarios on the origin, migration and partial extinction are proposed based on the dispersal abilities of these insects and palaeogeographical reconstructions during the Mesozoic. We assume that the north-to-south migration took place between 220 and 160 Ma.http://zoobank.org/urn:lsid:zoobank.org:pub:66E22602-FE0D-4641-AB14-D8CB129D8F67

Lower Cretaceous fossils from China shed light on the ancestral body plan of crown softshell\xa0turtles (Trionychidae, Cryptodira)

Pan-trionychids or softshell turtles are a highly specialized and widespread extant group of aquatic taxa with an evolutionary history that goes back to the Early Cretaceous. The earliest pan-trionychids had already fully developed the “classic” softshell turtle morphology and it has been impossible to resolve whether they are stem members of the family or are within the crown. This has hindered our understanding of the evolution of the two basic body plans of crown-trionychids. Thus it remains unclear whether the more heavily ossified shell of the cyclanorbines or the highly reduced trionychine morphotype is the ancestral condition for softshell turtles. A new pan-trionychid from the Early Cretaceous of Zhejiang, China, Perochelys hengshanensis sp. nov., allows a revision of softshell-turtle phylogeny. Equal character weighting resulted in a topology that is fundamentally inconsistent with molecular divergence date estimates of deeply nested extant species. In contrast, implied weighting retrieved Lower Cretaceous Perochelys spp. and Petrochelys kyrgyzensis as stem trionychids, which is fully consistent with their basal stratigraphic occurrence and an Aptian-Santonian molecular age estimate for crown-trionychids. These results indicate that the primitive morphology for soft-shell turtles is a poorly ossified shell like that of crown-trionychines and that shell re-ossification in cyclanorbines (including re-acquisition of peripheral elements) is secondary.