Single Dispersal Event Research Articles

Out of Africa: Miocene Dispersal, Vicariance, and Extinction within Hyacinthaceae Subfamily Urgineoideae

Disjunct distribution patterns in plant lineages are usually explained according to three hypotheses: vicariance, geodispersal, and long-distance dispersal. The role of these hypotheses is tested in Urgineoideae (Hyacinthaceae), a subfamily disjunctly distributed in Africa, Madagascar, India, and the Mediterranean region. The potential ancestral range, dispersal routes, and factors responsible for the current distribution in Urgineoideae are investigated using divergence time estimations. Urgineoideae originated in Southern Africa approximately 48.9 Mya. Two independent dispersal events in the Western Mediterranean region possibly occurred during Early Oligocene and Miocene (29.9-8.5 Mya) via Eastern and Northwestern Africa. A dispersal from Northwestern Africa to India could have occurred between 16.3 and 7.6 Mya. Vicariance and extinction events occurred approximately 21.6 Mya. Colonization of Madagascar occurred between 30.6 and 16.6 Mya, after a single transoceanic dispersal event from Southern Africa. The current disjunct distributions of Urgineoideae are not satisfactorily explained by Gondwana fragmentation or dispersal via boreotropical forests, due to the younger divergence time estimates. The flattened winged seeds of Urgineoideae could have played an important role in long-distance dispersal by strong winds and big storms, whereas geodispersal could have also occurred from Southern Africa to Asia and the Mediterranean region via the so-called arid and high-altitude corridors.

An ‘ameridelphian’ marsupial from the early Eocene of Australia supports a complex model of Southern Hemisphere marsupial biogeography

Recent molecular data strongly support the monophyly of all extant Australian and New Guinean marsupials (Eomarsupialia) to the exclusion of extant South American marsupials. This, together with available geological and fossil evidence, has been used to argue that the presence of marsupials in Australia is simply the result of a single dispersal event from South America during the latest Cretaceous or Palaeocene, without subsequent dispersals between the two continents. Here, I describe an isolated ankle bone (calcaneus) of a metatherian from the early Eocene Tingamarra Local Fauna in northeastern Australia. Strikingly, this specimen, QM F30060, lacks the 'continuous lower ankle joint pattern' (CLAJP), presence of which is a highly distinctive apomorphy of the marsupial clade Australidelphia, which includes Eomarsupialia, the living South American microbiotherian Dromiciops and the Tingamarran fossil marsupial Djarthia. Comparisons with a range of marsupials and stem-metatherians strongly suggest that the absence of the CLAJP in QM F30060 is plesiomorphic, and that this specimen represents the first unequivocal non-australidelphian ('ameridelphian') metatherian known from Australia. This interpretation is confirmed by phylogenetic analyses that place QM F30060 within (crown-group) Marsupialia, but outside Australidelphia. Based on these results, the distribution of marsupials within Gondwana cannot be explained by simply a single dispersal event from South America and Australia. Either there were multiple dispersals by marsupials (and possibly also stem-metatherians) between South America and Australia, in one or both directions, or, alternatively, there was a broadly similar metatherian fauna stretching across southern South America, Antarctica and Australia during the Late Cretaceous-early Palaeogene.

Phylogenetics, biogeography, and staminal evolution in the tribe Mentheae (Lamiaceae)

The mint family (Lamiaceae) is the sixth largest family of flowering plants, with the tribe Mentheae containing about a third of the species. We present a detailed perspective on the evolution of the tribe Mentheae based on a phylogenetic analysis of cpDNA and nrDNA that is the most comprehensive to date, a biogeographic set of analyses using a fossil-calibrated chronogram, and an examination of staminal evolution. Data from four cpDNA and two nrDNA markers representing all extant genera within the tribe Mentheae were analyzed using the programs BEAST, Lagrange, S-DIVA, and BayesTraits. BEAST was used to simultaneously estimate phylogeny and divergence times, Lagrange and S-DIVA were used for biogeographical reconstruction, and BayesTraits was used to infer staminal evolution within the tribe. Currently accepted subtribal delimitations are shown to be invalid and are updated. The Mentheae and all five of its subtribes have a Mediterranean origin and have dispersed to the New World multiple times. The vast majority of New World species of subtribe Menthinae are the product of a single dispersal event in the mid-late Miocene. At least four transitions from four stamens to two stamens have occurred within Mentheae, once in the subtribe Salviinae, once in the subtribe Lycopinae, and at least twice in the subtribe Menthinae. Worldwide cooling trends probably played a large role in the diversification and present day distribution of the tribe Mentheae. Additional work is needed to ascertain relationships within some Mentheae genera, especially in the subtribe Menthinae.

An expanded molecular phylogeny of the southern bluebells (Wahlenbergia, Campanulaceae) from Australia and New Zealand

We used nuclear and chloroplast DNA markers to examine relationships and test the current morphology-based taxonomy of several species and subspecies of Australian and New Zealand Wahlenbergia. We sampled nuclear ribosomal ITS regions and the chloroplast regions trnL–F and trnK–psbA from 105 individuals, representing 29 of the 46 species and subspecies currently recognised in New Zealand and Australia. Our phylogeny was incompletely resolved because of low levels of genetic variation in all three markers and some conflict between ITS and chloroplast markers. The New Zealand rhizomatous species appear to have radiated in New Zealand after a single long-distance dispersal event from Australia, but it is unclear to which species in Australia they are most closely related. The New Zealand radicate species do not form a clade; instead they are shown to be very closely related to many Australian radicate species. The four species in the New Zealand lowland radicate W. gracilis complex may all belong to the same morphologically variable species. In contrast, the other New Zealand radicate species, W. vernicosa, is probably a separately evolving lineage, and is not conspecific with the W. gracilis complex, nor the Australian W. littoricola, as previously hypothesised. Two of the New Zealand rhizomatous species, W. albomarginata and W. pygmaea, may be conspecific. By contrast, the morphologically distinctive New Zealand rhizomatous W. cartilaginea, W. matthewsii and W. congesta subsp. haastii each formed monophyletic groups. Samples of two recently described Australian species (W. rupicola and W. telfordii) formed monophyletic groups consistent with their recognition.

High genetic diversity in a remote island population system: sans sex

It has been proposed that long-distance dispersal of mosses to the Hawaiian Islands rarely occurs and that the Hawaiian population of the allopolyploid peat moss Sphagnum palustre probably resulted from a single dispersal event. Here, we used microsatellites to investigate whether the Hawaiian population of the dioicous S. palustre had a single founder and to compare its genetic diversity to that found in populations of S. palustre in other regions. The genetic diversity of the Hawaiian population is comparable to that of larger population systems. Several lines of evidence, including a lack of sporophytes and an apparently restricted natural distribution, suggest that sexual reproduction is absent in the Hawaiian plants. In addition, all samples of Hawaiian S. palustre share a genetic trait rare in other populations. Time to most recent ancestor (TMRCA) analysis indicates that the Hawaiian population was probably founded 49-51 kyr ago. It appears that all Hawaiian plants of S. palustre descend from a single founder via vegetative propagation. The long-term viability of this clonal population coupled with the development of significant genetic diversity suggests that vegetative propagation in a moss does not necessarily preclude evolutionary success in the long term.

Population genetic structure of sexual and parthenogenetic damselflies inferred from mitochondrial and nuclear markers.

It has been postulated that obligate asexual lineages may persist in the long term if they escape from negative interactions with either sexual lineages or biological enemies; and thus, parthenogenetic populations will be more likely to occur in places that are difficult for sexuals to colonize, or those in which biological interactions are rare, such as islands or island-like habitats. Ischnura hastata is the only known example of natural parthenogenesis within the insect order Odonata, and it represents also a typical example of geographic parthenogenesis, as sexual populations are widely distributed in North America, whereas parthenogenetic populations of this species have only been found at the Azores archipelago. In order to gain insight in the origin and distribution of parthenogenetic I. hastata lineages, we have used microsatellites, mitochondrial and nuclear DNA sequence data, to examine the population genetic structure of this species over a wide geographic area. Our results suggest that sexual populations of I. hastata in North America conform to a large subdivided population that has gone through a recent spatial expansion. A recent single long distance dispersal event, followed by a demographic expansion, is the most parsimonious hypothesis explaining the origin of the parthenogenetic population of this species in the Azores islands.

Does multiple seed loading in Blue Jays result in selective dispersal of smaller acorns?

Studies from both tropical and temperate systems show that scatter-hoarding rodents selectively disperse larger seeds farther from their source than smaller seeds, potentially increasing seedling establishment in larger-seeded plants. Size-biased dispersal is evident in many oaks (Quercus) and is true both across and within species. Here, we predict that intraspecifc variation in seed size also influences acorn dispersal by the Blue Jay (Cyanocitta cristata Linnaeus), but in an opposite manner. Blue Jays are gape-limited and selectively disperse smaller acorn species (e.g. pin oaks [Quercus palustris Münchh]), but often carry several acorns in their crop during a single dispersal event. We predict that jays foraging on smaller acorns will load more seeds per trip and disperse seeds to greater distances than when single acorns are carried in the bill. To test this, we presented free-ranging Blue Jays with pin oak acorns of different sizes over a 2-year period. In each of 16 experimental trials, we monitored the birds at a feeding station with remote cameras and determined the number of acorns removed and the distance acorns were dispersed when cached. Jays were significantly more likely to engage in multiple seed loading with smaller seeds in both years of the study. During the second year, these smaller acorns were dispersed farther than larger acorns, and during the first year, larger acorns were dispersed farther, revealing an inconsistent response to seed size during our study. We suggest that in some circumstances, multiple seed loading by Blue Jays may favor dispersal in some plant species.

Mechanistic models of seed dispersal by wind

Over the past century, various mechanistic models have been developed to estimate the magnitude of seed dispersal by wind, and to elucidate the relative importance of physical and biological factors affecting this passive transport process. The conceptual development has progressed from ballistic models, through models incorporating vertically variable mean horizontal windspeed and turbulent excursions, to models accounting for discrepancies between airflow and seed motion. Over hourly timescales, accounting for turbulent fluctuations in the vertical velocity component generally leads to a power-law dispersal kernel that is censored by an exponential cutoff far from the seed source. The parameters of this kernel vary with the flow field inside the canopy and the seed terminal velocity. Over the timescale of a dispersal season, with mean wind statistics derived from an “extreme-value” distribution, these distribution-tail effects are compounded by turbulent diffusion to yield seed dispersal distances that are two to three orders of magnitude longer than the corresponding ballistic models. These findings from analytic models engendered explicit simulations of the effects of turbulence on seed dispersal using computationally intensive fluid dynamics tools. This development marks a bifurcation in the approaches to wind dispersal, seeking either finer resolution of the dispersal mechanism at the scale of a single dispersal event, or mechanistically derived analytical dispersal kernels needed to resolve long-term and large-scale processes such as meta-population dynamics and range expansion. Because seed dispersal by wind is molded by processes operating over multiple scales, new insights will require novel theoretical tactics that blend these two approaches while preserving the key interactions across scales.

Phytogeographic aspects of Lysionotus pauciflorus sensu lato (Gesneriaceae) in the China, Japan and Taiwan regions: phylogenetic and morphological relationships and taxonomic consequences

Comparison of leaf morphometric variation and phylogenetic analyses based on nrITS and partial trnC-D cpDNA sequences were conducted for samples of Lysionotus pauciflorus sensu lato collected from China, Japan and Taiwan. In the morphometric comparison, leaves of plants from Japan proper and those from Taiwan proper were not significantly distinguishable by their leaf length to width ratio. In phylogenetic analyses, monophyly of L. pauciflorus s. l. samples was strongly supported, and Japanese and Taiwanese samples fell into a clade separate from Chinese samples. In the Japan–Taiwan clade, plants from Japan proper formed a sister clade to those from Okinawa Island (Japan) and Taiwan. The present results suggest that (1) the L. pauciflorus s. l. samples from China, Japan and Taiwan must be treated as a single species; (2) L. pauciflorus s. l. originated in China; (3) a single dispersal event, dispersal via a land-bridge during low sea levels in a Pleistocene glacial maximum, from China to Taiwan and Japan is proposed; (4) three oversea dispersal events, probably through anemochory, to Japan proper, across the Tokara Gap, to Okinawa islands crossing the Kerama Gap, and from Taiwan to Lanyu Island are proposed. The study gives further insight into the biogeographical dynamics between the Ryukyus and surrounding areas.

Out of America to Africa or Asia: Inference of Dispersal Histories Using Nuclear and Plastid DNA and the S-RNase Self-incompatibility Locus

The plant genus Lycium (Solanaceae) originated in the Americas and includes approximately 85 species that are distributed worldwide. The vast majority of Old World species occur in southern Africa and eastern Asia. In this study, we examine biogeographic relationships among Old World species using a phylogenetic approach coupled with molecular evolutionary analyses of the S-RNase self-incompatibility gene. The phylogeny inferred from nuclear granule-bound starch synthase I (GBSSI), nuclear conserved ortholog set II (COSII) marker C2_At1g24360, and plastid spacer data (trnH-pbsA, trnD(GUC)-trnT(GGU), rpl32-trnL(UAG), and ndhF-rpl32) includes a clade of eastern Asian Lycium nested within the African species, suggesting initial dispersal from the Americas to Africa, with subsequent dispersal to eastern Asia. Molecular dating estimates suggest that these dispersal events occurred relatively recently, with dispersal from the Americas to Africa approximately 3.64 Ma (95% highest posterior density [HPD]: 1.58-6.27), followed by subsequent dispersal to eastern Asia approximately 1.21 Ma (95% HPD: 0.32-2.42). In accordance, the S-RNase genealogy shows that S-RNases isolated from Old World species are restricted to four lineages, a subset of the 14 lineages including S-RNases isolated from New World Lycium species, supporting a bottleneck of S-RNase alleles concomitant with a single dispersal event from the Americas to the Old World. Furthermore, the S-RNase genealogy is also consistent with dispersal of Lycium from Africa to Asia, as eastern Asian alleles are restricted to a subset of the lineages that also include African alleles. Such a multilocus approach, including complementary data from GBSSI, COSII, plastid spacer regions, and S-RNase, is powerful for understanding dispersal histories of closely related species.

Vicariance or long-distance dispersal: historical biogeography of the pantropical subfamily Chrysophylloideae (Sapotaceae)

Aim Continental disjunctions in pantropical taxa have been explained by vicariance or long-distance dispersal. The relative importance of these explanations in shaping current distributions may vary, depending on historical backgrounds or biological characteristics of particular taxa. We aimed to determine the geographical origin of the pantropical subfamily Chrysophylloideae (Sapotaceae) and the roles vicariance and dispersal have played in shaping its modern distribution. Location Tropical areas of Africa, Australasia and South America. Methods We utilized a recently published, comprehensive data set including 66 species and nine molecular markers. Bayesian phylogenetic trees were generated and dated using five fossils and the penalized likelihood approach. Distributional ranges of nodes were estimated using maximum likelihood and parsimony analyses. In both biogeographical and molecular dating analyses, phylogenetic and branch length uncertainty was taken into account by averaging the results over 2000 trees extracted from the Bayesian stationary sample. Results Our results indicate that the earliest diversification of Chrysophylloideae was in the Campanian of Africa c. 73–83 Ma. A narrow time interval for colonization from Africa to the Neotropics (one to three dispersals) and Australasia (a single migration) indicates a relatively rapid radiation of this subfamily in the latest Cretaceous to the earliest Palaeocene (c. 62–72 Ma). A single dispersal event from the Neotropics back to Africa during the Neogene was inferred. Long-distance dispersal between Australia and New Caledonia occurred at least four times, and between Africa and Madagascar on multiple occasions. Main conclusions Long-distance dispersal has been the dominant mechanism for range expansion in the subfamily Chrysophylloideae. Vicariance could explain South American–Australian disjunction via Antarctica, but not the exchanges between Africa and South America and between New Caledonia and Australia, or the presence of the subfamily in Madagascar. We find low support for the hypothesis that the North Atlantic land bridge facilitated range expansions at the Palaeocene/Eocene boundary.

New specimen reveals deltatheroidan affinities of the North American Late Cretaceous Mammal Nanocuris

ABSTRACT Deltatheroida is a small, mostly Asian, clade of Cretaceous mammals with a complicated systematic history and a poor North American fossil record. The recently described latest Cretaceous Nanocuris improvida is a relatively large, morphologically distinctive taxon with carnivorous adaptations; it was tentatively referred to its own family Nanocuridae within Eutheria. Here, we describe a new specimen from the uppermost Cretaceous Lance Formation of Wyoming that is referable to Nanocuris improvida, the second occurrence for the taxon. New morphological information from the specimen allows us to refer five additional Lancian specimens, some of which have been previously described as deltatheroidans, to Nanocuris improvida and ?Nanocuris sp. Results from a phylogenetic analysis remove Nanocuris from Eutheria and reveal strong support for its deltatheroidan affinities and for its nested position within Metatheria. As a result, we subsume Nanocuridae within the deltatheroidan family Deltatheridiidae. Within Deltatheridiidae, Nanocuris forms a clade with the only other North American deltatheroidan in the analysis, Atokatheridium from the Aptian-Albian of Oklahoma. With three Asian deltatheroidans as outgroups to the North American clade, we find support for the hypothesis that deltatheroidans originated in Asia by the Aptian-Albian and undertook a single dispersal event to North America by the Aptian-Albian.

Formulating a Historical and Demographic Model of Recent Human Evolution Based on Resequencing Data from Noncoding Regions

BackgroundEstimating the historical and demographic parameters that characterize modern human populations is a fundamental part of reconstructing the recent history of our species. In addition, the development of a model of human evolution that can best explain neutral genetic diversity is required to identify confidently regions of the human genome that have been targeted by natural selection.Methodology/Principal FindingsWe have resequenced 20 independent noncoding autosomal regions dispersed throughout the genome in 213 individuals from different continental populations, corresponding to a total of ∼6 Mb of diploid resequencing data. We used these data to explore and co-estimate an extensive range of historical and demographic parameters with a statistical framework that combines the evaluation of multiple models of human evolution via a best-fit approach, followed by an Approximate Bayesian Computation (ABC) analysis. From a methodological standpoint, evaluating the accuracy of the parameter co-estimation allowed us to identify the most accurate set of statistics to be used for the estimation of each of the different historical and demographic parameters characterizing recent human evolution.Conclusions/SignificanceOur results support a model in which modern humans left Africa through a single major dispersal event occurring ∼60,000 years ago, corresponding to a drastic reduction of ∼5 times the effective population size of the ancestral African population of ∼13,800 individuals. Subsequently, the ancestors of modern Europeans and East Asians diverged much later, ∼22,500 years ago, from the population of ancestral migrants. This late diversification of Eurasians after the African exodus points to the occurrence of a long maturation phase in which the ancestral Eurasian population was not yet diversified.

A multi‐locus phylogeny of Euryops (Asteraceae, Senecioneae) augments support for the "Cape to Cairo" hypothesis of floral migrations in Africa

AbstractWith about 100 species, Euryops (Cass.) Cass. ranks among the most speciose genera of the tribe Senecioneae (Asteraceae). The genus has its greatest diversity in South Africa, and displays an interesting disjunct distribution with most of the taxa found in southern Africa and a group of eight endemic species confined to the mountains of tropical East Africa and northeastern Africa. Molecular phylogenetic analyses of DNA sequence data from three chloroplast fragments and the nuclear ITS region were used to reconstruct the evolutionary history of 41 Euryops species in order to unravel species relationships and to determine the origin of the disjunct Afromontane taxa. Our results show a lack of support and resolution in the internal structure of the trees, but also reveal strong incongruence between the ITS and cpDNA datasets as assessed by Bayes Factors. We hypothesise that this is a consequence of the isolation and divergence of many populations over a short time period at some point in the history of the genus. Molecular dating based on our phylogenetic tree suggests that the genus diversified in South Africa around four million years ago. The origin of the East African species, dated at 1.9 Ma, well after the uplift of the East African mountains, is consistent with a scenario of a single dispersal event from South Africa northwards into the tropical East African mountains where diversification occurred, creating a monophyletic group of regional Afromontane endemics.

Erratum to: DNA sequences from three genomes reveal multiple long-distance dispersals and non-monophyly of sections in Australasian Plantago (Plantaginaceae)

We examined the geographic origins and taxonomic placements of New Zealand and Australian Plantago (Plantaginaceae) by using molecular phylogenetic data. Plantago comprises over 200 species distributed worldwide. Analyses of three markers from the nuclear (ITS), chloroplast (ndhF?rpl32) and mitochondrial (coxI) genomes showed that the New Zealand species form three distinct, well supported clades that are not each others' closest relatives, and were each derived relative to the sampled Australian species. Therefore, at least three long-distance directional dispersal events into New Zealand can be inferred for Plantago, likely from Australian ancestors. This result differs from the biogeographic pattern often reported for New Zealand plant genera of a single dispersal event followed by rapid radiation, and may be attributed to ready biotic dispersal of mucilaginous seeds and habitat similarities of the Australasian species. Molecular dating placed the arrival time and diversification of the New Zealand species between 2.291 and 0.5�million years ago, which coincides with the geological dates for the uplift of mountain ranges in New Zealand. The mitochondrial DNA substitution rate of the Australasian clade relative to the rest of the genus is discussed, as well as implications of the non-monophyly of sections Oliganthos, Mesembrynia and Plantago within subgenus Plantago.

DNA sequences from three genomes reveal multiple long-distance dispersals and non-monophyly of sections in Australasian Plantago (Plantaginaceae)

We examined the geographic origins and taxonomic placements of New Zealand and Australian Plantago (Plantaginaceae) by using molecular phylogenetic data. Plantago comprises over 200 species distributed worldwide. Analyses of three markers from the nuclear (ITS), chloroplast (ndhF–rpl32) and mitochondrial (coxI) genomes showed that the New Zealand species form three distinct, well supported clades that are not each others’ closest relatives, and were each derived relative to the sampled Australian species. Therefore, at least three long-distance directional dispersal events into New Zealand can be inferred for Plantago, likely from Australian ancestors. This result differs from the biogeographic pattern often reported for New Zealand plant genera of a single dispersal event followed by rapid radiation, and may be attributed to ready biotic dispersal of mucilaginous seeds and habitat similarities of the Australasian species. Molecular dating placed the arrival time and diversification of the New Zealand species between 2.291 and 0.5 million years ago, which coincides with the geological dates for the uplift of mountain ranges in New Zealand. The mitochondrial DNA substitution rate of the Australasian clade relative to the rest of the genus is discussed, as well as implications of the non-monophyly of sections Oliganthos, Mesembrynia and Plantago within subgenus Plantago.

Phylogeny, biogeography, and recurrent evolution of divergent bill types in the nectar-stealing flowerpiercers (Thraupini: Diglossa and Diglossopis)

Neotropical tanagers known as flowerpiercers (Diglossa and Diglossopis) have a novel feeding adaptation, comprising a downward curved hook on the maxilla that allows these species to obtain floral nectar without pollination. Using mitochondrial DNA sequences, the phylogenetic relationships of all 18 species of flowerpiercers were studied for the first time. Strong support was found for the monophyly of flowerpiercers and for the monophyly of four superspecies within flowerpiercers. However, previously described species-groups, as well as the genus Diglossopis, are not monophyletic. The biogeographic origin of flowerpiercers was identified as Andean, with a single dispersal event from the northern Andes to Central America and a single dispersal event from the northern Andes to the tepuis. The first principal component, representing a contrast between hook size and bill size, was mapped onto the phylogeny to examine the evolution of relative hook size in the group. Across the phylogeny, a relatively large hook and a relatively small hook evolved multiple times in unrelated lineages, indicating lability in bill morphology. Differences in hook size among sympatric species, together with habitat partitioning and behavioural differences, can explain the coexistence of multiple species of flowerpiercers at the same locality. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 14–28.

Pararhabdodon isonensis and Tsintaosaurus spinorhinus: a new clade of lambeosaurine hadrosaurids from Eurasia

We present new anatomical information showing that Koutalisaurus kohlerorum, from the Maastrichtian of Lleida Province, northeastern Spain, is most probably the junior synonym of Pararhabdodon isonensis from the same region. Dentary and maxillary characters previously considered as autapomorphies of K. kohlerorum and P. isonensis, respectively, are shown to be synapomorphies uniting the latter with Tsintaosaurus spinorhinus from the Campanian of the Wangshi Group, Shandong Province, China. This study provided conclusive evidence of the presence of the Lambeosaurinae in Europe. Tsintaosaurus spinorhinus and Pararhabdodon isonensis were inferred to form a clade of basal lambeosaurines characterized by a maxilla with an elevated articular facet for the jugal (continuous with the ectopterygoid ridge) and an extremely medially projected symphyseal region of the dentary. This clade originated in Asia during the middle or late Campanian. Pararhabdodon isonensis or its ancestors migrated from Asia to the Iberian island of the European archipelago. Reconstruction of ancestral areas by Fitch parsimony attributes the European occurrence of P. isonensis to a single dispersal event from Asia no later than middle to late Campanian.

Historical biogeography of the endemic Campanulaceae of Crete

AbstractAim The clade Campanulaceae in the Cretan area is rich in endemics, with c. 50% of its species having restricted distributions. These species are analysed in the context of a larger phylogeny of the Campanulaceae. Divergence times are calculated and hypotheses of vicariance and dispersal are tested with the aim of understanding whether Cretan lineages represent remnants of an older continental flora.Location The Cretan area: Crete and the Karpathos Islands (Greece).Methods We obtained chloroplast DNA sequence data from rbcL, atpB and matK genes for 102 ingroup taxa, of which 18 are from the Cretan area, 11 are endemics, and two have disjunct, bi‐regional distributions. We analysed the data using beast, a Bayesian approach that simultaneously infers the phylogeny and divergence times. We calibrated the tree by placing a seed fossil in the phylogeny, and used published age estimates as a prior for the root.Results The phylogenetic reconstruction shows that all Campanula species fall within a well‐supported campanuloid clade; however, Campanula is highly polyphyletic. The Cretan endemics do not form a monophyletic group, and species are scattered throughout the campanuloid clade. Therefore, the Cretan taxa did not evolve following a single vicariance or dispersal event. Most Cretan lineages represent remnants of an older continental flora, with the exception of one clade that radiated in situ after island isolation, and one lineage that appears to have arrived by dispersal.Main conclusions Most Cretan species were present in the islands at the time of their isolation, and very little long‐distance dispersal to Crete and diversification within Crete has occurred since then. Endemism is probably driven by loss of species on the mainland after island isolation. Species on the islands may have been more widespread in the past, but they are now restricted to often inaccessible areas, probably as a result of human pressure.

Conyza canadensis seed ascent in the lower atmosphere

Long-distance dispersal of wind dispersed plant seed is dependent on seeds ascending in the atmosphere's surface boundary layer (SL). However, seed dispersal research often focuses on the near-surface dynamics of abscission and deposition, with little attention paid to seed ascent and transport beyond the surface boundary layer. Our research sought to estimate the vertical seed density flux of Conyza canadensis, a common agricultural weed, in the surface boundary layer. Using a 2.7 ha field infested with Conyza canadensis, the vertical seed concentration profile was measured on 5 days, three times per day while simultaneously monitoring micrometeorological conditions to connect the mechanisms of release with the process of ascent. Vertical seed sampling was conducted from two to six meters above ground level using removable screen frames. Remotely piloted airplanes were used to quantify seed concentration at 68 and 120 m above ground level and provide a connection between near surface dynamics and dynamics higher in the SL. Seed flux density (area under seed concentration curve) decreased with height and decreased from morning to afternoon. The seed flux density was significantly correlated with mean mechanical turbulence and the interaction of mean mechanical and mean thermal turbulence, supporting earlier research of meteorological effects on seed dispersal. While fewer total seeds were collected in the afternoon, more seeds were collected at 68 and 120 m during this period and may suggest more seeds were present in the upper SL where dispersal distance may be greater. Seeds collected above the SL will potentially be carried for hours before descending, depositing seeds in the range of 2–122 m, and influencing a much greater area than seeds unable to ascend through the lower SL. While this range is very wide, the dispersal distances reported herein are several orders of magnitude greater than previously reported for plants. These findings are all the more striking since the study species has evolved resistance to glyphosate herbicide, an herbicide now widely used in soybean, cotton, and corn crops in the US. Therefore, aerial transport of C. canadensis seeds carrying genes coding for glyphosate resistance enables seed to move tens or hundreds of kilometers in a single dispersal event, a spread rate corroborated by number of cases of reported glyphosate resistance occurrences in North America.