Phylogeography of a widespread eastern North American shrub, Viburnum lantanoides

Phylogeography of a herbal Pinellia ternata reveals repeated range expansions and inter/postglacial recolonization routes on the fragmented distribution pattern in China

Most plant phylogeographic studies in China have focused on the importance of genetic divergence and where should the shelter be located. Little attention has been paid to range expansion and recolonization routes in this region. In this study, two cpDNA fragments (psbK-psbI and trnL-F), two pairs of nuclear gene sequences (ITS and ETS), and nine pairs of SSR molecular markers were used, combined with Bayesian Skyline Plot method, gene barrier analysis, and species distribution models to explore the phylogeographical pattern, potential expansion routes and population dynamic history of Pinellia ternata from 22 population. The results showed that phylogeograhical pattern and genetic structure for P. ternata are effected by environmental heterogeneity and climate fluctuation, and it can be divided into two groups (Southwest group, Central and Eastern group) and thus there are at least two glacial refugia in China. Three expanding routes within groups were explored to contribute to the phylogeogrephic pattern of P. ternata based on the geographical distribution and network analysis of haplotypes. In a word, our study reveals repeated range expansions and inter/postglacial recolonization routes on the fragmented distribution pattern in China and resolves the refugia distributing in China and has also certain reference value for the protection of the medicinal plant P. ternata.

Floral Diversity and Pollination Syndromes in Agave subgenus Manfreda

The genus Agave is an ecological keystone of American deserts and both culturally and economically important in Mexico. Agave is a large genus of about 250 species. The radiation of Agave is marked by an initial adaptation to desert environments and then a secondary diversification of species associated with pollinator groups, such as hummingbirds and nocturnal moths. Phylogenetic analyses place Agave subgenus Manfreda, or the "herbaceous agaves," in a monophyletic clade that likely evolved in part as an adaptation to novel pollination vectors. Here, we present a morphological and observational study assessing the evolution of floral form in response to pollinator specialization within this understudied group. We found significant visitation by hummingbirds and nocturnal moths to several species within the Agave subgenus Manfreda. These observations also align with our morphological analyses of floral organs and support the evolution of distinct pollination syndromes. We found that not all floral morphology is consistent within a pollination syndrome, suggesting hidden diversity in the evolution of floral phenotypes in Agave. We also characterize the morphological variation between herbarium and live specimens, demonstrating that special consideration needs to be made when combining these types of data. This work identifies the potential for studying the functional evolution of diverse floral forms within Agave and demonstrates the need to further explore ecological and evolutionary relationships to understand pollinator influence on diversification in the genus.

Genome-wide diversity analysis suggests divergence among Upper Guinea and the Dahomey Gap populations of the Sisrè berry (Syn: miracle fruit) plant (Synsepalum dulcificum [Schumach. & Thonn.] Daniell) in West Africa

Although Synsepalum dulcificum is viewed as one of the most economically promising orphan tree crops worldwide, its genetic improvement and sustainable conservation are hindered by a lack of understanding of its evolutionary history and current population structure. Here, we report for the first time the application of genome-wide single nucleotide polymorphism genotyping to a diverse panel of S. dulcificum accessions to depict the genetic diversity and population structure of the species in the Dahomey Gap (DG) and Upper Guinea (UG) regions to infer its evolutionary history. Our findings suggest low overall genetic diversity but strong population divergence within the species. Neighbor-joining analysis detected two genetic groups in the UG and DG regions, while STRUCTURE distinguished three genetic groups, corresponding to the UG, Western DG, and Central DG regions. Application of Monmonier's algorithm revealed the existence of a barrier disrupting connectivity between the UG and DG groups. The Western DG group consistently exhibited the highest levels of nucleotide and haplotype diversities, while that of the Central DG exhibited the lowest. Analyses of Tajima's D, Fu's Fs, and Achaz Y* statistics suggest that while both UG and Central DG groups likely experienced recent expansions, the Western DG group is at equilibrium. These findings suggest a geographical structuring of genetic variation which supports the conclusion of differential evolutionary histories among West African groups of S. dulcificum. These results provide foundational insights to guide informed breeding population development and design sustainable conservation strategies for this species.

Geographical Patterns of Genetic Variation in Locoto Chile (Capsicum pubescens) in the Americas Inferred by Genome-Wide Data Analysis

The locoto chile (Capsicum pubescens) is a regionally important food crop grown and marketed throughout the mid-highlands of South andCentral America, but little is known about its evolution and the diversity it harbours. An initial scan of genetic diversity and structure across its cultivation range was conducted, the first one using a genomic approach. The RAD-sequencing methodology was applied to a sampling of C. pubescens germplasm consisting of 67 accessions from different American countries, covering its range of distribution/cultivation on the continent. The RAD-seq SNP data obtained clustered the accessions into three major groups, with a high degree of admixture/reticulation among them. Moderate but significant differentiation and geographic structuration were found, depicting a south-north pattern in the distribution of genetic variation. The highest levels of diversity were found among central-western Bolivian individuals, while the lowest was found across Central America-Mexican germplasm. This study provides new genome-wide supported insights into the diversity and differentiation of C. pubescens, as well as a starting point for more efficient use of its genetic variation and germplasm conservation efforts. The findings also contribute to understanding the evolutionary history of C. pubescens, but further investigation is needed to disentangle its origin and diversification under domestication.

Phylogeography and population genetics of a widespread cold-adapted ant, Prenolepis imparis

As species arise, evolve, and diverge, they are shaped by forces that unfold across short and long time scales and at both local and vast geographic scales. It is rare, however, to be able document this history across broad sweeps of time and space in a single species. Here, we report the results of a continental-scale phylogenomic analysis across the entire range of a widespread species. We analyzed sequences of 1,402 orthologous Ultraconserved Element (UCE) loci from 75 individuals to identify population genetic structure and historical demographic patterns across the continent-wide range of a cold-adapted ant, the winter ant, Prenolepis imparis. We recovered five well-supported, genetically isolated clades representing lineages that diverged from 8.2-2.2 million years ago. These include: 1) an early diverging lineage located in Florida, 2) a lineage that spans the southern United States, 3) populations that extend across the midwestern and northeastern United States, 4) populations from the western United States, and 5) populations in southwestern Arizona and Mexico. Population genetic analyses revealed little or no gene flow among these lineages, but patterns consistent with more recent gene flow among populations within lineages, and localized structure with migration in the western United States. High support for five major geographic lineages and lack of evidence of contemporary gene flow indicate in situ diversification across the species' range, producing relatively ancient lineages that persisted through subsequent climate change and glaciation during the Quaternary.

The phylogeographic history of Megistostegium (Malvaceae) in the dry, spiny thickets of southwestern Madagascar using RAD-seq data and ecological niche modeling

The spiny thicket of southwestern Madagascar represents an extreme and ancient landscape with extraordinary levels of biodiversity and endemism. Few hypotheses exist for explaining speciation in the region and few plant studies have explored hypotheses for species diversification. Here, we investigate three species in the endemic genus Megistostegium (Malvaceae) to evaluate phylogeographic structure and explore the roles of climate, soil, and paleoclimate oscillations on population divergence and speciation throughout the region. We combine phylogenetic and phylogeographic inference of RADseq data with ecological niche modeling across space and time. Population structure is concurrent with major rivers in the region and we identify a new, potentially important biogeographic break coincident with several landscape features. Our data further suggests that niches occupied by species and populations differ substantially across their distribution. Paleodistribution modeling provide evidence that past climatic change could be responsible for the current distribution, population structure, and maintenance of species in Megistostegium.

Evolution of Castanea in North America: restriction-site-associated DNA sequencing and ecological modeling reveal a history of radiation, range shifts, and disease

PREMISE

Although chestnuts and chinquapins are some of the best known and most widely loved of any plants in North America, relatively little genomic sequencing has been done, and much is still unknown about their evolution.

METHODS

We used double-digest restriction-site-associated DNA (ddRAD) sequencing data to infer the species-level phylogeny for Castanea and assess the phylogeography of the North American species using samples collected from populations that span the full extent of the species' ranges. We also constructed species distribution models using digitized herbarium specimens and observational data from field surveys.

RESULTS

We identified strong population structure within Castanea dentata (American chestnut) that reflects a stepwise northern migration since the last glacial maximum. Our species distribution models further confirmed this scenario and matched closely with the Castanea fossil pollen record. We also found significant structure within the Castanea pumila lineage, most notably a genetic cluster that corresponds to the frequently recognized Castanea pumila var. ozarkensis.

CONCLUSIONS

The two North American Castanea species have contrasting patterns of population structure, but each is typical of plant phylogeography in North America. Within the C. pumila complex, we found novel genetic structure that provides new insights about C. pumila taxonomy. Our results also identified a series of distinctive populations that will be valuable in ongoing efforts to conserve and restore chestnuts and chinquapins in North America.

Genetic diversity and population structure in Vitis species illustrate phylogeographic patterns in eastern North America

Geographical distribution and diversity of current plant species have been strongly shaped by climatic oscillations during the Quaternary. Analysing the resulting divergence among species and differentiation within species is crucial to understand the evolution of taxa like the Vitis genus, which provides very useful genetic resources for grapevine improvement and might reveal original recolonization patterns due to growth habit and dispersal mode. Here, we studied the genetic structure in natural populations of three species from eastern North America: Vitis aestivalis, V. cinerea and V. riparia using different marker types. Vitis aestivalis and V. cinerea showed higher diversity than V. riparia. The two former species are less differentiated, confirming an earlier divergence of V. riparia. V. aestivalis and V. riparia exhibited different genetic groups on both sides of the Appalachian Mountains that could mirror different recolonization routes from southern refugia. Genetic structure was stronger in V. cinerea, for which two varieties (var. berlandieri and var. cinerea) are morphologically recognized. Our results confirm this distinction and suggest the existence of three other lineages within var. cinerea. These discontinuities appear linked to adaptation of var. berlandieri to dry and limy areas of Texas and partially to the Mississippi River Valley. Rapid range expansions from refugia upon climate warming are also suggested by the low linkage disequilibrium values observed. Furthermore, large variation for downy mildew resistance was observed in the three species. Our findings appeared consistent with the vegetation history of eastern North America.

Phylogeography and demographic expansion in the widely distributed horned passalus beetle, Odontotaenius disjunctus (coleoptera: Passalidae)

Dynamic climatic oscillations during the Pleistocene had profound effects on the distribution of species across North America. Although the role of historical climate change on speciation remains controversial, the impact on genetic variation within species has been well documented. Analyses of mtDNA sequences from the cytochrome oxidase I gene (911 bp) for 115 individuals of Odontotaenius disjunctus was combined with ecological niche modelling (ENM) to infer the demographic and population differentiation scenarios under present and past conditions. We inferred three lineages that diverged during the Pleistocene and replace each other geographically across the eastern United States. One of these lineages traverses previously identified genetic barriers for terrestrial animals including the Mississippi and Apalachicola Rivers and the Appalachian Mountains. We observed overlapping ranges between two haplotype groups as well as a region of secondary contact associated with ecological transition zone in northern Florida. The two continental lineages depict a genetic signature of a recent population increase associated with expanding niche envelope, whereas the clade restricted to peninsular Florida shows stable populations in a shrinking niche envelope. Given the lack of ecological separation, overlapping distribution of haplogroups and the presence of secondary contact zones, the taxonomic status of these lineages must await robust testing using multilocus DNA data to assess species boundaries.

Breeding system of diploid sexuals within the Ranunculus auricomus complex and its role in a geographical parthenogenesis scenario

The larger distribution area of asexuals compared with their sexual relatives in geographical parthenogenesis (GP) scenarios has been widely attributed to the advantages of uniparental reproduction and polyploidy. However, potential disadvantages of sexuals due to their breeding system have received little attention so far. Here, we study the breeding system of five narrowly distributed sexual lineages of Ranunculus notabilis s.l. (R. auricomus complex) and its effects on outcrossing, inbreeding, female fitness, and heterozygosity. We performed selfing and intra- and interlineage crossings by bagging 481 flowers (59 garden individuals) followed by germination experiments. We compared seed set and germination rates, and related them to genetic distance and genome-wide heterozygosity (thousands of RADseq loci). Selfings (2.5%) unveiled a significantly lower seed set compared with intra- (69.0%) and interlineage crossings (69.5%). Seed set of intra- (65%) compared to interpopulation crossings (78%) was significantly lower. In contrast, all treatments showed comparable germination rates (32%-43%). Generalized linear regressions between seed set and genetic distance revealed positive relationships in general and between lineages, and a negative one within lineages. Seed set was the main decisive factor for female fitness. Germination rates were not related to genetic distance at any level, but were positively associated with heterozygosity in interlineage crossings. Experiments confirmed full crossability and predominant outcrossing among sexual R. notabilis s.l. lineages. However, up to 5% (outliers 15%-31%) of seeds were formed by selfing, probably due to semi-self-compatibility in a multi-locus gametophytic SI system. Less seed set in intrapopulation crossings, and higher seed set and germination rates from crossings of genetically more distant and heterozygous lineages (interlineage) indicate negative inbreeding and positive outbreeding effects. In GP scenarios, sexual species with small and/or isolated populations can suffer from decreased female fitness due to their breeding system. This factor, among others, probably limits range expansion of sexuals.

The Quaternary range dynamics ofNoccaea iberidea(Brassicaceae), a typical representative of subalpine/alpine steppe communities of Anatolian mountains

The responses of Anatolian plants to global climate change have been poorly investigated. In this study, we aimed to understand how climatic oscillation during the Quaternary period helped to shape the current distribution patterns of the Anatolian endemic Noccaea iberidea, a typical representative of tragacanthic (thorny cushion) steppe communities of Anatolia. We used ecological niche modelling combined with statistical phylogeography, based on nuclear ribosomal ITS and plastidic trnL-F and trnS-ycf9 regions. Both the structure of the haplotype networks and the results of the extended Bayesian skyline plot analysis clearly indicated that N. iberidea has been through a recent population expansion. This interpretation was also supported by ecological niche modelling analysis, which showed that the availability of areas of high suitability expanded from the Last Interglacial to the Last Glacial Maximum, suggesting that N. iberidea might have expanded its range during the glacial periods. In conclusion, the study improves our understanding of the demographic history and responses of steppe plant communities of Anatolia to global climate changes through the Late Quaternary glacial–interglacial cycles, which in turn might aid in the development of future conservation strategies.

Westward range expansion from middle latitudes explains the Mississippi River discontinuity in a forest herb of eastern North America

It is often expected that temperate plants have expanded their geographical ranges northward from primarily southern refugia. Evidence for this hypothesis is mixed in eastern North American species, and there is increasing support for colonization from middle latitudes. We studied genome-wide patterns of variation in RADseq loci to test hypotheses concerning range expansion in a North American forest herb (Campanula americana). First, spatial patterns of genetic differentiation were determined. Then phylogenetic relationships and divergence times were estimated. Spatial signatures of genetic drift were also studied to identify the directionality of recent range expansion and its geographical origins. Finally, spatially explicit scenarios for the spread of plants across the landscape were compared, using variation in the population mutation parameter and Tajima's D. We found strong longitudinal subdivision, with populations clustering into groups west and east of the Mississippi River. While the southeastern region was probably part of a diverse Pleistocene refugium, there is little evidence that range expansion involved founders from these southern locales. Instead, declines in genetic diversity and the loss of rare alleles support a westward colonization wave from a middle latitude refugium near the southern Appalachian Mountains, with subsequent expansion from a Pleistocene staging ground in the Mississippi River Valley (0.51-1.27 million years ago). These analyses implicate stepping stone colonization from middle latitudes as an important mechanism of species range expansion in eastern North America. This study further demonstrates the utility of population genetics as a tool to infer the routes travelled by organisms during geographical range expansion.

Joint Phylogenetic Estimation of Geographic Movements and Biome Shifts during the Global Diversification of Viburnum

Phylogeny, molecular sequences, fossils, biogeography, and biome occupancy are all lines of evidence that reflect the singular evolutionary history of a clade, but they are most often studied separately, by first inferring a fossil-dated molecular phylogeny, then mapping on ancestral ranges and biomes inferred from extant species. Here we jointly model the evolution of biogeographic ranges, biome affinities, and molecular sequences, while incorporating fossils to estimate a dated phylogeny for all of the 163 extant species of the woody plant clade Viburnum (Adoxaceae) that we currently recognize in our ongoing worldwide monographic treatment of the group. Our analyses indicate that while the major Viburnum lineages evolved in the Eocene, the majority of extant species originated since the Miocene. Viburnum radiated first in Asia, in warm, broad-leaved evergreen (lucidophyllous) forests. Within Asia, we infer several early shifts into more tropical forests, and multiple shifts into forests that experience prolonged freezing. From Asia, we infer two early movements into the New World. These two lineages probably first occupied warm temperate forests and adapted later to spreading cold climates. One of these lineages (Porphyrotinus) occupied cloud forests and moved south through the mountains of the Neotropics. Several other movements into North America took place more recently, facilitated by prior adaptations to freezing in the Old World. We also infer four disjunctions between Asia and Europe: the Tinus lineage is the oldest and probably occupied warm forests when it spread, whereas the other three were more recent and in cold-adapted lineages. These results variously contradict published accounts, especially the view that Viburnum radiated initially in cold forests and, accordingly, maintained vessel elements with scalariform perforations. We explored how the location and biome assignments of fossils affected our inference of ancestral areas and biome states. Our results are sensitive to, but not entirely dependent upon, the inclusion of fossil biome data. It will be critical to take advantage of all available lines of evidence to decipher events in the distant past. The joint estimation approach developed here provides cautious hope even when fossil evidence is limited. [Biogeography; biome; combined evidence; fossil pollen; phylogeny; Viburnum.].

Phylogeography and the Evolutionary History of Sunflower (Helianthus annuus L.): Wild Diversity and the Dynamics of Domestication

Patterns of genetic variation in crops are the result of selection and demographic changes that occurred during their domestication and improvement. In many cases, we have an incomplete picture of the origin of crops in the context of their wild progenitors, particularly with regard to the processes producing observed levels of standing genetic variation. Here, we analyzed sequence diversity in cultivated sunflower (Helianthus annuus L.) and its wild progenitor (common sunflower, also H. annuus) to reconstruct phylogeographic relationships and population genetic/demographic patterns across sunflower. In common sunflower, south-north patterns in the distribution of nucleotide diversity and lineage splitting indicate a history of rapid postglacial range expansion from southern refugia. Cultivated sunflower accessions formed a clade, nested among wild populations from the Great Plains, confirming a single domestication event in central North America. Furthermore, cultivated accessions sorted by market type (i.e., oilseed vs. confectionery) rather than breeding pool, recapitulating the secondary development of oil-rich cultivars during its breeding history. Across sunflower, estimates of nucleotide diversity and effective population sizes suggest that cultivated sunflower underwent significant population bottlenecks following its establishment ~5000 years ago. The patterns inferred here corroborate those from previous studies of sunflower domestication, and provide a comprehensive overview of its evolutionary history.