Biogeographic Hypotheses Research Articles

Phylogenetic relationships, genetic diversity and biogeography of menhadens, genus Brevoortia (Clupeiformes, Clupeidae)

Brevoortia Gill 1861 is a genus of the Clupeidae (Teleostei) that includes six species of fishes commonly known as menhadens in eastern North America and “savelhas” or “saracas” in southeastern South America. Species of Brevoortia are important components of the marine food web of coastal ecosystems in the Atlantic and contribute significantly to fisheries. In this study, the first phylogenetic and biogeographic hypotheses including all species of Brevoortia are presented. A total of 113 specimens were analyzed using three molecular markers (two mitochondrial: COI and 16s; and one nuclear: RAG2). Maximum Parsimony, Maximum Likelihood and Bayesian Inference were employed to estimate phylogenetic relationships. A Bayesian multispecies coalescent approach was used to estimate a dated phylogeny, which supported biogeographic analyses of ancestral geographic ranges. Results corroborate previous hypotheses that the four North Atlantic species are grouped in two clades, one composed of B. tyrannus (Latrobe, 1802) and B. patronus Goode, 1878, and the second including B. smithi Hildebrand, 1941 and B. gunteri Hildebrand, 1948. The South Atlantic B. aurea (Spix and Agassiz, 1829) and B. pectinata (Jenyns, 1842) form a third clade, which is sister to the clade composed of B. smithi and B. gunteri. The monophyly and validity of the six nominal species of Brevoortia were not supported. Results also indicate that Brevoortia originated in the North Atlantic during the middle Miocene (about 15 Mya). A cooling event of the tropical Atlantic at around 10 Mya likely facilitated the range expansion of the genus to the South Atlantic, whereas a significant warming of the tropical Atlantic waters during the late Miocene at 6–7 Mya possibly promoted the isolation between the northern and southern counterparts of that ancestral lineage. The relevance of the Florida Peninsula in association with sea level fluctuations for the diversification within Brevoortia is also discussed.

Genomic data from the Brazilian sibilator frog reveal contrasting pleistocene dynamics and regionalism in two South American dry biomes

AbstractAimKnowledge about the Neotropical dry formations, particularly the Caatinga, remains rudimentary compared to other biotas in the region. Here we address several biogeographical hypotheses by combining intense geographical and genomic sampling obtained for the Brazilian sibilator frog. We specifically test predictions related to the putative roles of past climate shifts (Pleistocene and Holocene) and local geographical barriers (past and current courses of the São Francisco River, SFR) in causing population differentiation in this species.LocationCaatinga and eastern Cerrado.TaxonBrazilian sibilator frog Leptodactylus troglodytes.MethodsWe sequenced up to ~15,000 single nucleotide polymorphisms for 159 samples from 61 locations. We inferred genetic structure using spatial clustering and examined population sizes through time. We estimated the relationship among populations using phylogenetic reconstruction, estimated historical distributions with ecological niche modelling and inferred demographic history under isolation‐with‐migration models.ResultsGenetic diversity in L. troglodytes corresponds to biome boundaries, with one population in the Cerrado and two populations in the Caatinga, separated by the SFR. Demographic model selection indicates the Caatinga populations expanded since the end of the Pleistocene while the Cerrado population declined. Within the Caatinga, population expansion began earlier and was more extreme in the north. A continuous stability area maintained the two Caatinga populations, which share a common origin and began diverging in the mid‐Pleistocene, first with symmetric gene flow and later under pronounced migration from the north.Main conclusionsWe could not reject a role of past climate change in causing diversification of relictual populations in the Cerrado, but we found no evidence of multiple refuges or long‐term isolation within the Caatinga. Instead, diversification in this biome appears to be caused by the SFR acting as a ‘soft barrier’ that constrains migration over an extended period of time.

Ichthyofauna as a Regionalization Instrument of the Coastal Lagoons of the Gulf of Mexico

Marine fishes have been used in the determinations and corroborations of biogeographic hypotheses, as in the southwest Gulf of Mexico (GOM), where the warm-temperate and tropical ichthyofaunas of the Carolinian and Caribbean provinces mix. The objective of this study was to determine if the arrangement of the lagoon-estuarine ichthyofauna of the southwest GOM corresponds to a previous biogeographic hypothesis based on coastal marine ichthyofauna. Based on peer-reviewed and specialized literature, an ichthyofauna distribution database of 15 coastal lagoons distributed from southern Texas, USA, to Campeche, Mexico, was constructed and used to determine beta diversity, taxonomic diversity, and the geographical segregation of lagoons. A database of 115 species was obtained, more than expected for the lagoon systems of the southwest GOM. The lagoon ichthyofauna of the southwest of the GOM did not follow the traditional biogeographic hypothesis; instead, it was segregated into three sections: northern section within the Carolinian Province, central section with major Caribbean influence, and southern section within the Caribbean Province.

Ostatnie lata życia Benedykta Dybowskiego (1833-1930) w świetle korespondencji z Januszem Domaniewskim (1891-1954) - przyczynek do biogramu

Wybitny zoolog, popularyzator darwinizmu i działacz społeczny. Absolwent uniwersytetów w Dorpacie i Wrocławiu, doktorat uzyskał na Uniwersytecie Berlińskim (1860). Od 1861 r. profesor zoologii w warszawskiej Szkole Głównej. Jako uczestnik konspiracji niepodległościowej, powstaniec styczniowy i komisarz Rządu Narodowego do spraw Litwy i Białorusi, został aresztowany i skazany w procesie Romualda Traugutta na 12 lat ciężkich robót. W latach 1864-1868 przebywał na zesłaniu nad Jeziorem Bajkał, gdzie pomimo ciężkich warunków bytowych prowadził badania faunistyczne i geograficzne. W uznaniu zasług naukowych został uwolniony, co umożliwiło mu kontynuowanie badań Bajkału, a w latach 1872-1875, wraz z Michałem Jankowskim (1842-1912) i Wiktorem Godlewskim (1833-1900), odbycie wyprawy badawczej po Amurze, aż do Morza Japońskiego. W latach 1879-1882 pracował jako lekarz na Kamczatce, prowadząc jednocześnie badania przyrodnicze i etnograficzne. W okresie 1882-1906, zakończonym odejściem na emeryturę, kierował katedrą zoologii Uniwersytetu we Lwowie. Przez kolejnych 25 lat, aż do śmierci w 1930 r., kontynuował aktywną działalność naukową i społeczną, głównie jako autor oryginalnych opracowań naukowych oraz publicysta. Po 1918 r., zaangażowany w ruch niepodległościowy, aktywnie włączył się w organizowanie polskich instytucji naukowych m.in. Narodowego Muzeum Przyrodniczego w Warszawie, a także nauczanie i popularyzację zoologii. Przez całe życie starał się uczestniczyć w budowie ?lepszego społeczeństwa? aktywnie propagując abstynencję oraz higienę życia, esperanto jako międzynarodowy język pokoju, walcząc o prawa kobiet i sprawiedliwość. Ateista i przeciwnik zarówno religii, jak i kościołów. Z naukowego punktu widzenia światową sławę przyniosło mu opisanie kilkuset nowych dla wiedzy gatunków, głównie spośród kiełży, mięczaków, ryb, płazów i ptaków, a także zwrócenie uwagi na przyrodę Bajkału i jego endemiczną faunę. Wyróżnienie jednolitych zespołów faunistycznych z uwzględnieniem wyników oryginalnych badań prób dennych, a także danych geofizycznych, sprawiło, że Benedykt Dybowski uznawany jest za jednego z pionierów badań hydrobiologicznych, twórców limnologii. Jego hipotezy biogeograficzne wskazują na historyczne drogi migracji gatunków azjatyckich, a także związki geograficznej izolacji ze specjacją fauny kamczackiej. Przeprowadził szereg udanych eksperymentów aklimatyzacyjnych. Wyniki badań przyrodniczych, antropologicznych i etnologicznych przedstawił w ponad 400 publikacjach, jednocześnie zebrał i przekazał do muzeów niezwykle obszerny i cenny materiał badawczy, który do dnia dzisiejszego służy światowej nauce.

Molecular phylogeny and ancestral biogeographic reconstruction of Platanthera subgenus Limnorchis (Orchidaceae) using target capture methods

Platanthera is one of the largest genera of temperate orchids in the Holarctic and exemplifies a lineage that has adaptively radiated into diverse habitats within North America, Asia, Europe, North Africa, Borneo, and Sarawak. Major centers of diversity in this genus are North America and eastern Asia. Despite its diversity, a thorough phylogenetic hypothesis for the genus is lacking because no studies have yet sampled taxa exhaustively or developed a robust molecular toolkit. While there is strong evidence that suggests monophyly of subgenus Limnorchis, most taxa in this group have not been included in a phylogenetic analysis. In this study, we developed a new toolkit for Platanthera consisting of genomic information from 617 low-copy nuclear loci. Using a targeted enrichment approach, we collected high-throughput sequence data in 23 accessions of nine of the 12 diploid species of subgenus Limnorchis and outgroup species across Platanthera. A maximum likelihood analysis resolved a strongly supported monophyletic clade for subgenus Limnorchis. Ancestral biogeographic reconstruction indicated that subgenus Limnorchis originated in western North America ca. 3–4.5 Mya from an ancestor that was widespread in western North America and eastern Asia and subsequently diversified in western North America, followed by dispersal of some species to eastern North America. Our results indicate complex biogeographic connections between Asia and North America, and therefore it suggests that Platanthera is a suitable system to test biogeographic hypotheses over time and space in the Holarctic. Our results are also expected to facilitate further study of diversification and biogeographic spread across Platanthera and lay the groundwork for understanding independent origins, biogeography, and morphological diversification of polyploid species within subgenus Limnorchis.

A new distributional record for the Martin del Campo’s Arboreal Alligator Lizard (Abronia martindelcampoi) with comments on the biogeography of arboreal Alligator-lizards in the Sierra Madre del Sur, Mexico

ABSTRACT Alligator lizards of the genus Abronia are a clade of arboreal and terrestrial squamates distributed throughout much of the highlands of Mexico and Central America. Here, we report a new record of the Mexican endemic A. martindelcampoi that represents the easternmost limit of the species and the lowest known elevational record. We briefly discuss the biogeographical hypotheses that have been proposed in the past concerning this and other related genera.

A new species of Bryconops (Characiformes: Iguanodectidae) from Atlantic coastal drainages of Suriname and French Guiana

ABSTRACT A new species of Bryconops is described based on its unique caudal-fin color pattern, with a dark blotch occupying the mid-basal region of the caudal-fin dorsal lobe, and a combination of 29-32 branched anal-fin rays, 44-47 perforated scales in the lateral line, six rows of scales above the lateral line, and a deep body (30.3-31.7 % SL). The new species belongs to the subgenus Bryconops based on its edentulous and short maxilla, with the posterior extension of that bone not reaching the junction between the second and third infraorbitals. The new species was previously reported in the literature as B. caudomaculatus. However, these species differ from each other in morphometric and meristic characters, as well as in color pattern. Comments on distribution of Bryconops species in coastal drainages of Suriname and French Guiana additional support for biogeographic hypotheses in this area.

When parasites persist: tapeworms survive host extinction and reveal waves of dispersal across Beringia.

Investigations of intercontinental dispersal between Asia and North America reveal complex patterns of geographic expansion, retraction and isolation, yet historical reconstructions are largely limited by the depth of the record that is retained in patterns of extant diversity. Parasites offer a tool for recovering deep historical insights about the biosphere, improving the resolution of past community-level interactions. We explored biogeographic hypotheses regarding the history of dispersal across Beringia, the region intermittently linking Asia and North America, through large-scale multi-locus phylogenetic analyses of the genus Schizorchis, an assemblage of host-specific cestodes in pikas (Lagomorpha: Ochotonidae). Our genetic data support palaeontological evidence for two separate geographic expansions into North America by Ochotona in the late Tertiary, a history that genomic evidence from extant pikas does not record. Pikas descending from the first colonization of Miocene age persisted into the Pliocene, subsequently coming into contact with a second wave of Nearctic colonists from Eurasia before going extinct. Spatial and temporal overlap of historically independent pika populations provided a window for host colonization, allowing persistence of an early parasite lineage in the contemporary fauna following the extinction of its ancestral hosts. Empirical evidence for ancient 'ghost assemblages' of hosts and parasites demonstrates how complex mosaic faunas are assembled in the biosphere through episodes of faunal mixing encompassing parasite lineages across deep and shallow time.

Phylogenetic and biogeographical history confirm the Anatolian origin ofBornmuellera (Brassicaceae) and clade divergence between Anatolia and the Balkans in the Plio-Pleistocene transition

Understanding disjunct distribution patterns in the Balkan Peninsula and Anatolia is important in order to reconstruct robust biogeographical hypotheses. This is instrumental in understanding the recolonization patterns of Europe during the Quaternary glaciation/interglaciation periods and the potential role of Anatolia as a refugium. Unfortunately, only a few studies have been conducted to uncover such processes. Here, we used all eight species of the genus Bornmuellera (Brassicaceae) with a scattered distribution in the Balkans and Anatolia to reconstruct its biogeographic history. We applied nuclear internal transcribed spacer (ITS) and plastid trnL-F regions and showed that 1) Bornmuellera is monophyletic and, 2) It is originated in the Pliocene in Anatolia (3.88 million years ago (mya), 3) Anatolian species are not monophyletic and, 4) Divergence between the representatives of one Anatolian clade (B. cappadocica and B. kiyakii) and the Balkan clade coincided with the Plio-Pleistocene transition (3.2-2.6 mya).

Genomic insights into the origin of trans‐Mediterranean disjunct distributions

AbstractAimTwo main biogeographical hypotheses have been proposed to explain the Mediterranean‐Turanian disjunct distributions exhibited by numerous steppe‐dwelling organisms, namely (a) dispersal during the Messinian salinity crisis (∼5.96–5.33 Ma) followed by range fragmentation and vicariance, and (b) Pleistocene colonization and recent processes of population subdivision (<2 Ma). Despite the two hypotheses postulate the role of climatic alterations and changes in landmass configuration on determining such disjunct distributions, estimates of the timing of lineage diversification have not been complemented so far with spatially‐explicit tests providing independent evidence on the proximate processes underlying geographical patterns of population genetic connectivity/fragmentation.LocationMediterranean‐Turanian region.TaxonSaltmarsh band‐winged grasshopper (Mioscirtus wagneri).MethodsWe integrate different sources of genetic (mtDNA and ddRADseq) and spatial information (configuration of emerged lands and niche modelling) to evaluate competing hypotheses of lineage diversification in the saltmarsh band‐winged grasshopper, a halophile species showing a classical Mediterranean‐Turanian disjunct distribution.ResultsPhylogenomic analyses reveal the presence of two North African cryptic lineages and support that trans‐Mediterranean populations of the species diverged in the Pleistocene, with evidence of post‐Messinian permeability of the Strait of Gibraltar to gene flow likely associated with sea level drops during glacial periods. Accordingly, spatial patterns of genetic differentiation are best explained by a scenario of population connectivity defined by the configuration of emerged landmasses and environmentally suitable habitats during glacial periods, a time when effective population sizes of the species peaked as inferred by genomic‐based demographic reconstructions.Main conclusionsOur results support post‐Messinian colonization and Pleistocene diversification as the biogeographical scenario best explaining the trans‐Mediterranean disjunct distributions of halophilous organisms.

Reflections on the Nature, Framing, and Testing of Historical Biogeographic Hypotheses

Reflections on the Nature, Framing, and Testing of Historical Biogeographic Hypotheses

Genomic fingerprints of palaeogeographic history: The tempo and mode of rift tectonics across tropical Africa has shaped the diversification of the killifish genus Nothobranchius (Teleostei: Cyprinodontiformes)

This paper reports a phylogeny of the African killifishes (Genus Nothobranchius, Order Cyprinodontiformes) informed by five genetic markers (three nuclear, two mitochondrial) of 80 taxa (seven undescribed and 73 of the 92 recognized species). These short-lived annual fishes occupy seasonally wet habitats in central and eastern Africa, and their distribution coincides largely with the East African Rift System (EARS). The fossil dates of sister clades used to constrain a chronometric tree of all sampled Nothobranchius recovered the origin of the genus at ~13.27 Mya. It was followed by the radiations of six principal clades through the Neogene. An ancestral area estimation tested competing biogeographical hypotheses to constrain the ancestral origin of the genus to the Nilo-Sudan Ecoregion, which seeded a mid-Miocene dispersal event into the Coastal ecoregion, followed closely (~10 Mya) by dispersals southward across the Mozambique coastal plain into the Limpopo Ecoregion. Extending westwards across the Tanzanian plateau, a pulse of radiations through the Pliocene were associated with dispersals and fragmentation of wetlands across the Kalahari and Uganda Ecoregions. We interpret this congruence of drainage rearrangements with dispersals and cladogenic events of Nothobranchius to reflect congruent responses to recurrent uplift and rifting. The coevolution of these freshwater fishes and wetlands is attributed to ultimate control by tectonics, as the EARS extended southwards during the Neogene. Geobiological consilience of the combined evidence supports a tectonic hypothesis for the evolution of Nothobranchius.

Pennaraptoran Theropod Dinosaurs Past Progress and New Frontiers

ABSTRACT The Coelurosauria are a group of mostly feathered theropods that gave rise to birds, the only dinosaurs that survived the Cretaceous-Paleogene extinction event and are still found today. Between their first appearance in the Middle Jurassic up to the end Cretaceous, coelurosaurs were party to dramatic geographic changes on the Earth’s surface, including the breakup of the supercontinent Pangaea, and the formation of the Atlantic Ocean. These plate tectonic events are thought to have caused vicariance or dispersal of coelurosaurian faunas, influencing their evolution. Unfortunately, few coelurosaurian biogeographic hypotheses are supported by quantitative evidence. Here, we report the first, broadly-sampled quantitative analysis of coelurosaurian biogeography using the likelihood-based package BioGeoBEARS. Mesozoic geographic configurations and changes are reconstructed and employed as constraints in this analysis, including their associated uncertainties. We use a comprehensive time-calibrated coelurosaurian evolutionary tree produced from the Theropod Working Group phylogenetic data matrix. Six biogeographic models in the BioGeoBEARS package with different assumptions about the evolution of spatial distribution are tested against the geographic constraints. Our results statistically favour the DIVALIKE+J and DEC+J models, which allow vicariance and founder events, supporting continental vicariance as an important factor in coelurosaurian evolution. Ancestral range estimation indicates frequent dispersal events via the Apulian Route (connecting Europe and Africa during the Early Cretaceous) and the Bering Land Bridge (connecting North America and Asia during the Late Cretaceous). These quantitative results are consistent with commonly inferred Mesozoic dinosaurian dispersals and continental-fragmentation-induced vicariance events. In addition, we recognise the importance of Europe as a dispersal centre and gateway in the Early Cretaceous, as well as other vicariance events like those triggered by the disappearance of land-bridges.

Filling the gaps in a highly diverse Neotropical lizard lineage: a new and endemic genus of Cercosaurinae (Squamata: Gymnophthalmidae) with the description of two new species from the Northern Andes of Colombia

In the last decade, understanding of the Neotropical lizards family Gymnophthalmidae has changed dramatically with the recognition of several new genera, resolution of non-monophyly, definition of previously unknown lineages and refined biogeographic hypotheses. Recent field explorations on the northern Cordillera Central in Colombia uncovered two undescribed species that cannot be assigned to any currently recognized gymnophthalmid genus. Based on a molecular phylogenetic analysis combined with morphological and genetic distances, we describe a new genus and two new species from the northern Andes of Colombia. Magdalenasaura gen. nov. is restricted to the Magdalena biogeographic province and is sister to the cis-Andean genus Gelanesaurus. The new genus can be readily distinguished from all other Cercosaurinae genera by a combination of genetic and morphological characters. The new genus contains Magdalenasaura leurosquama sp. nov. and M. adercum sp. nov., both found in forested habitats near streams at altitudes ranging from 1300 to 1850 m on the eastern flank of the northern Cordillera Central in Colombia. We differentiate the Cercosaurinae genera from Colombia based on general scutellation. Filling the gaps of the tremendous diversity of gymnophthalmid lizards will improve taxonomic and biogeographic hypotheses to better understand the evolution of endemic lineages from the north-western corner of South America. http://zoobank.org/urn:lsid:zoobank.org:pub:47E621FD-BEA9-4C65-87D8-D832C4EEC3A4

A bi‐organellar phylogenomic study of Pandanales: inference of higher‐order relationships and unusual rate‐variation patterns

We used a bi-organellar phylogenomic approach to address higher-order relationships in Pandanales, including the first molecular phylogenetic study of the panama-hat family, Cyclanthaceae. Our genus-level study of plastid and mitochondrial gene sets includes a comprehensive sampling of photosynthetic lineages across the order, and provides a framework for investigating clade ages, biogeographic hypotheses and organellar molecular evolution. Using multiple inference methods and both organellargenomes, we recovered mostly congruent and strongly supported relationships within and between families, including the placement of fully mycoheterotrophic Triuridaceae. Cyclanthaceae and Pandanaceae plastomes have slow substitution rates, contributing to weakly supported plastid-based relationships in Cyclanthaceae. While generally slowly evolving, mitochondrial genomes exhibit sporadic rate elevation across the order. However, we infer well-supported relationships even for slower evolving mitochondrial lineages in Cyclanthaceae. Clade age estimates across photosynthetic lineages are largely consistent with previous studies, are well correlated between the two organellar genomes (with slightly younger inferences from mitochondrial data), and support several biogeographic hypotheses. We show that rapidly evolving non-photosynthetic lineages may bias age estimates upwards at neighbouring photosynthetic nodes, even using a relaxed clock model. Finally, we uncovered new genome structural variants in photosynthetic taxa at plastid inverted repeat boundaries that show promise as interfamilial phylogenetic markers.

Evolution between forest macrorefugia is linked to discordance between genetic and morphological variation in Neotropical passerines

The central Andean rainforests and the Atlantic Forest are two similar biomes that are fully isolated by xerophytic and open-vegetation regions (the Chaco and Cerrado, respectively). Even though there is evidence suggesting that these rainforests have been connected in the past, their dynamics of connection, the geographic areas that bridged these regions, and the biological processes that have promoted diversification between them remain to be studied. In this research, we used three passerine species (Poecilotriccus plumbeiceps, Phylloscartes ventralis and Cacicus chrysopterus) as models to address whether the Andean and the Atlantic forests have acted as a refugia system (macrorefugia), and to evaluate biogeographic hypotheses of diversification and connection between them. In order to achieve these goals, we performed traditional phylogeographic analyses and compared alternative biogeographic scenarios by using Approximate Bayesian Computation. Additionally, we performed morphological analyses to evaluate phenotypic divergence between these regions. Our findings support that both rainforest regions acted as refugia, but that the impact of their isolation was stronger on the genetic than on the morphologic characters. Our results provided evidence that both geographic isolation as well as ecological factors have modeled the external traits of forest organisms in the region. Regarding the connection routes between the Andes and the Atlantic Forest, the genetic data rejected the hypothesis of a Chaco connection in the tested species, providing evidence for a connection through the Cerrado or through the transition between the Cerrado and Chaco, in a process that could have started as early as the Late Miocene.

Shifting ecosystem connectivity during the Pleistocene drove diversification and gene‐flow in a species complex of Neotropical birds (Tityridae: Pachyramphus)

AbstractAimWe aim to test the biogeographic drivers of diversification and gene‐flow at the Isthmus of Panama using a species complex of suboscine birds as a case study. We specifically evaluate whether diversification in these birds is better explained by continuous parapatry or a Refuge Model of periodic isolation and gene‐flow due glacial cycling.LocationThe Isthmus of Panama (Neotropics).TaxonPachyramphus aglaiae and Pachyramphus homochrous (Aves: Tityridae).MethodsWe develop an approach to distinguish among the two biogeographic hypotheses—parapatric ecological speciation versus climatically mediated speciation—by making explicit predictions for demographic history, niche evolution and change in geographic connectivity over time. We sequenced genome‐wide markers (ultraconserved elements) to estimate the evolutionary and demographic history of this group. We applied both phylogenomic network analyses and demographic modelling using a supervised machine learning approach. These genetic analyses were combined with a novel distribution modelling method that estimates the probability of interspecies contact as a function of climatic conditions through time.ResultsWe found that both spatial and genetic analyses revealed concordant results. All speciation events occurred during the Pleistocene and were characterized by non‐continuous gene‐flow, supporting a scenario of climate‐mediated diversification. Spatial connectivity was highest at present, consistent with our best demographic model of secondary contact.Main conclusionsThis study exemplifies a mechanism by which speciation, dispersal and introgression unfold in an important region for Neotropical diversification—the Isthmus of Panama—where periods of both isolation and introgression probably drive diversification. Overall, our results are consistent with the Refuge Model of biotic diversification, but suggest that introgression may be a crucial yet underappreciated component of this classic paradigm.

Genotyping-by-sequencing and ecological niche modeling illuminate phylogeography, admixture, and Pleistocene range dynamics in quaking aspen (Populus tremuloides).

Populus tremuloides is the widest‐ranging tree species in North America and an ecologically important component of mesic forest ecosystems displaced by the Pleistocene glaciations. Using phylogeographic analyses of genome‐wide SNPs (34,796 SNPs, 183 individuals) and ecological niche modeling, we inferred population structure, ploidy levels, admixture, and Pleistocene range dynamics of P. tremuloides, and tested several historical biogeographical hypotheses. We found three genetic lineages located mainly in coastal–Cascades (cluster 1), east‐slope Cascades–Sierra Nevadas–Northern Rockies (cluster 2), and U.S. Rocky Mountains through southern Canadian (cluster 3) regions of the P. tremuloides range, with tree graph relationships of the form ((cluster 1, cluster 2), cluster 3). Populations consisted mainly of diploids (86%) but also small numbers of triploids (12%) and tetraploids (1%), and ploidy did not adversely affect our genetic inferences. The main vector of admixture was from cluster 3 into cluster 2, with the admixture zone trending northwest through the Rocky Mountains along a recognized phenotypic cline (Utah to Idaho). Clusters 1 and 2 provided strong support for the “stable‐edge hypothesis” that unglaciated southwestern populations persisted in situ since the last glaciation. By contrast, despite a lack of clinal genetic variation, cluster 3 exhibited “trailing‐edge” dynamics from niche suitability predictions signifying complete northward postglacial expansion. Results were also consistent with the “inland dispersal hypothesis” predicting postglacial assembly of Pacific Northwestern forest ecosystems, but rejected the hypothesis that Pacific‐coastal populations were colonized during outburst flooding from glacial Lake Missoula. Overall, congruent patterns between our phylogeographic and ecological niche modeling results and fossil pollen data demonstrate complex mixtures of stable‐edge, refugial locations, and postglacial expansion within P. tremuloides. These findings confirm and refine previous genetic studies, while strongly supporting a distinct Pacific‐coastal genetic lineage of quaking aspen.

Late Cretaceous neornithine from Europe illuminates the origins of crown birds.

Our understanding of the earliest stages of crown bird evolution is hindered by an exceedingly sparseavian fossil record from the Mesozoic era. The most ancient phylogenetic divergences among crown birds are known to have occurred in the Cretaceous period1-3, but stem-lineage representatives of the deepest subclades of crown birds-Palaeognathae (ostriches and kin), Galloanserae (landfowl and waterfowl) and Neoaves (all other extant birds)-are unknown from the Mesozoic era. As a result, key questions related to the ecology4,5, biogeography3,6,7 and divergence times1,8-10 of ancestral crown birds remain unanswered. Here we report a new Mesozoic fossil that occupies a position close to the last common ancestor of Galloanserae and fills a key phylogenetic gap in the early evolutionary history of crown birds10,11. Asteriornis maastrichtensis, gen. et sp. nov., from the Maastrichtian age of Belgium (66.8-66.7 million years ago), is represented by a nearly complete, three-dimensionally preserved skull and associated postcranial elements. The fossil represents one of the only well-supported crown birds from the Mesozoic era12, and is the first Mesozoic crown bird with well-represented cranial remains. Asteriornis maastrichtensis exhibits a previously undocumented combination of galliform (landfowl)-like and anseriform (waterfowl)-like features, and its presence alongside a previously reported Ichthyornis-like taxon from the same locality13 provides direct evidence of the co-occurrence of crown birds and avialan stem birds. Its occurrence in the Northern Hemisphere challenges biogeographical hypotheses of a Gondwanan origin of crown birds3, and its relatively small size and possible littoral ecology may corroborate proposed ecological filters4,5,9 that influenced the persistence of crown birds through the end-Cretaceous mass extinction.

A well‐resolved transcriptomic phylogeny of the mite harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi) reveals signatures of Gondwanan vicariance

AbstractAimWe explored the extent to which Gondwanan vicariance contributed to the circum‐Antarctic distribution of the mite harvestman family Pettalidae, a group of small, dispersal‐limited arachnids whose phylogeny has been poorly resolved, precluding rigorous biogeographic hypothesis testing.LocationContinental landmasses of former temperate Gondwana (Chile, South Africa, Sri Lanka, Australia and New Zealand).TaxonPettalidae, Opiliones.MethodsWe generated transcriptomes for a phylogeny of 16 pettalids, spanning 9 genera. Data were analysed using maximum likelihood, Bayesian inference and coalescence methods. The phylogenetic position of the Sri Lankan genus Pettalus was further explored using quartet likelihood mapping and changes in gene likelihood scores. We also estimated divergence times and looked for signatures of extinction across Antarctica and central Australia using previously published phylogenies with near‐complete species sampling constrained to match our transcriptomic results. Finally, we estimated ancestral ranges and inferred instances of vicariance.ResultsWe recovered a well‐supported topology with a division between taxa from landmasses that made up East Gondwana, and a grade of taxa from West Gondwana. Pettalus was resolved either as the sister group of the Queensland‐endemic Austropurcellia, or as the sister group to a larger clade from East Gondwana, though favouring Pettalus + Austropurcellia. Divergence times for multiple vicariance events coincided with Gondwana's breakup. Speciation–extinction analysis found one diversification process for the family: an initial burst of cladogenesis that slowed down through time.Main ConclusionsGiven that the order of cladogenesis corresponds to the order in which Gondwana fragmented, and the concurrent timing of vicariance and rifting, Gondwanan breakup explains major biogeographic patterns in Pettalidae. Some divergences predate initial rifting, but there is no evidence of trans‐oceanic dispersal. The Sri Lanka–eastern Australia relationship makes sense in the light of large‐scale extinction across Antarctica and central Australia; however, we find no clear signatures of mass extinction.