Phylogeographic analysis of the red seaweed Palmaria palmata reveals a Pleistocene marine glacial refugium in the English Channel

Phylogeography has provided a new approach to the analysis of the postglacial history of a wide range of taxa but, to date, little is known about the effect of glacial periods on the marine biota of Europe. We have utilized a combination of nuclear, plastid and mitochondrial genetic markers to study the biogeographic history of the red seaweed Palmaria palmata in the North Atlantic. Analysis of the nuclear rDNA operon (ITS1-5.8S-ITS2), the plastid 16S-trnI-trnA-23S-5S, rbcL-rbcS and rpl12-rps31-rpl9 regions and the mitochondrial cox2-3 spacer has revealed the existence of a previously unidentified marine refugium in the English Channel, along with possible secondary refugia off the southwest coast of Ireland and in northeast North America and/or Iceland. Coalescent and mismatch analyses date the expansion of European populations from approximately 128,000 BP and suggest a continued period of exponential growth since then. Consequently, we postulate that the penultimate (Saale) glacial maximum was the main event in shaping the biogeographic history of European P. palmata populations which persisted throughout the last (Weichselian) glacial maximum (c. 20,000 BP) in the Hurd Deep, an enigmatic trench in the English Channel.     

Post‐glacial colonization of eastern Europe from the Carpathian refugium: evidence from mitochondrial DNA of the common vole Microtus arvalis

There is now considerable evidence for the survival of temperate species within glacial refugia that were situated at relatively high latitudes, notably the Carpathian Basin and Dordogne region in Europe. However, the prevalence of fossil remains in such locations is rarely matched by molecular evidence for their contribution to subsequent geographical and demographic expansion of the species in question. One obstacle to this has been insufficient analysis of modern samples from the relevant areas, in particular the parts of eastern Europe that surround the Carpathian refugium. In the present study, we examine the patterns of variation in mitochondrial DNA of the common vole (Microtus arvalis), obtained from existing museum specimens and from newly‐collected samples obtained in this area. We show that common voles from one of six extant mitochondrial DNA lineages have colonized most of the species' range in eastern Europe. We contend that the post‐glacial dispersal of this lineage most likely originated from the Carpathian refugium, adding support to the argument that such northern refugia made an important contribution to existing genetic diversity in Europe. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

A long‐standing Pleistocene refugium in southern Africa and a mosaic of refugia in East Africa: insights from mtDNA and the common eland antelope

Aim Previous genetic studies of African savanna ungulates have indicated Pleistocene refugial areas in East and southern Africa, and recent palynological, palaeovegetation and fossil studies have suggested the presence of a long‐standing refugium in the south and a mosaic of refugia in the east. Phylogeographic analysis of the common eland antelope, Taurotragus oryx (Bovidae), was used to assess these hypotheses and the existence of genetic signatures of Pleistocene climate change. Location The sub‐Saharan savanna biome of East and southern Africa. Methods Mitochondrial DNA control‐region fragments (414 bp) from 122 individuals of common eland were analysed to elucidate the phylogeography, genetic diversity, spatial population structuring, historical migration and demographic history of the species. The phylogeographic split among major genetic lineages was dated using Bayesian coalescent‐based methods and a calibrated fossil root of 1.6 Ma for the split between the common eland and the giant eland, Taurotragus derbianus. Results Two major phylogeographic lineages comprising East and southern African localities, respectively, were separated by a net nucleotide distance of 4.7%. A third intermediate lineage comprised only three haplotypes, from Zimbabwe in southern Africa. The estimated mutation rate of 0.097 Myr^?1 revealed a more recent common ancestor for the eastern lineage (0.21 Ma; 0.07–0.37) than for the southern lineage (0.35 Ma; 0.10–0.62). Compared with the latter, the eastern lineage showed pronounced geographic structuring, lower overall nucleotide diversity, higher population differentiation, and isolation‐by‐distance among populations. Main conclusions The data support the hypothesis of Pleistocene refugia occurring in East and southern Africa. In agreement with palynological, palaeovegetation and fossil studies, our data strongly support the presence of a longer‐standing population in the south and a mosaic of Pleistocene refugia in the east, verifying the efficacy of genetic tools in addressing such questions. The more recent origin of the common eland inhabiting East Africa could result from colonization following extinction from the region. Only two other dated African ungulate phylogenies have been published, applying different methods, and the similarity of dates obtained from the three distinct approaches indicates a significant event c. 200 ka, which left a strong genetic signature across a range of ungulate taxa.     

Late Pleistocene speciation of three closely related tree peonies endemic to the Qinling–Daba Mountains,a major glacial refugium in Central China

Determining the factors promoting speciation is a major task in ecological and evolutionary research and can be aided by phylogeographic analysis. The Qinling–Daba Mountains (QDM) located in central China form an important geographic barrier between southern subtropical and northern temperate regions, and exhibit complex topography, climatic, and ecological diversity. Surprisingly, few phylogeographic analyses and studies of plant speciation in this region have been conducted. To address this issue, we investigated the genetic divergence and evolutionary histories of three closely related tree peony species (Paeonia qiui, P. jishanensis, and P. rockii) endemic to the QDM. Forty populations of the three tree peony species were genotyped using 22 nuclear simple sequence repeat markers (nSSRs) and three chloroplast DNA sequences to assess genetic structure and phylogenetic relationships, supplemented by morphological characterization and ecological niche modeling (ENM). Morphological and molecular genetic analyses showed the three species to be clearly differentiated from each other. In addition, coalescent analyses using DIYABC conducted on nSSR variation indicated that the species diverged from each other in the late Pleistocene, while ecological niche modeling (ENM) suggested they occupied a larger area during the Last Glacial Maximum (LGM) than at present. The combined genetic evidence from nuclear and chloroplast DNA and the results of ENM indicate that each species persisted through the late Pleistocene in multiple refugia in the Qinling, Daba, and Taihang Mountains with divergence favored by restricted gene flow caused by geographic isolation, ecological divergence, and limited pollen and seed dispersal. Our study contributes to a growing understanding of the origin and population structure of tree peonies and provides insights into the high level of plant endemism present in the Qinling–Daba Mountains of Central China.     

Mitochondrial DNA sequence analysis reveals multiple Pleistocene glacial refugia for the Yellow‐spotted mountain newt,Neurergus derjugini (Caudata: Salamandridae) in the mid‐Zagros range in Iran and Iraq

Phylogeography is often used to investigate the effects of glacial cycles on current genetic structure of various plant and animal species. This approach can also identify the number and location of glacial refugia as well as the recolonization routes from those refugia to the current locations. To identify the location of glacial refugia of the Yellow‐spotted mountain newt, Neurergus derjugini, we employed phylogeography patterns and genetic variability of this species by analyzing partial ND4 sequences (867 bp) of 67 specimens from 15 sampling localities from the whole species range in Iran and Iraq. Phylogenetic trees concordant with haplotype networks showed a clear genetic structure among populations as three groups corresponding to the populations in the north, center, and south. Evolutionary ages of clades north and south ranging from 0.15 to 0.17 Myr, while the oldest clade is the central clade, corresponding to 0.32 Myr. Bayesian skyline plots of population size change through time show a relatively slight increase until about 25 kyr (around the last glacial maximum) and a decline of population size about 2.5 kyr. The presence of geographically structured clades in north, center, and south sections of the species range signifies the disjunct populations that have emerged in three different refugium. This study illustrates the importance of the effect of previous glacial cycles in shaping the genetic structure of mountain species in the Zagros range. These areas are important in terms of long‐term species persistence and therefore valuable areas for conservation of biodiversity.     

Multiple Pleistocene refugia and post‐glacial colonization in the European chub (Squalius cephalus) revealed by combined use of nuclear and mitochondrial markers

Aim To analyse patterns of nuclear and mitochondrial genetic variation in the European chub, Squalius cephalus (Linnaeus, 1758), in order to understand the evolutionary history of this species and to test biogeographical hypotheses for the existence of co‐distributed European freshwater fish species. Location Rivers in Europe (Finland, Poland, Czech Republic, France, Bulgaria, Spain, Italy). Methods We genotyped 12 polymorphic microsatellite markers derived from 310 individuals collected from across the distribution of S. cephalus in Europe (including a total of 15 populations) and sequenced mitochondrial DNA (mtDNA) from a subset of 75 individuals. Sequences of mtDNA cytochrome b were analysed using both phylogenetic (median‐joining networks) and population genetic methods (tests for demographic history, mismatch distributions, Bayesian coalescent analysis). Geographical structure in microsatellite loci was examined using a distance method (F_ST), factorial correspondence analysis (FCA) and a Bayesian clustering method (structure ). Results The mtDNA network showed a clear split into four different haplogroup lineages: Western (separated into Atlantic and Danubian sublineages), Eastern, Aegean (occurring in two distinct sublineages in the Balkans and in Spain) and Adriatic. Our results indicate recent population expansion in the Eastern and Western Atlantic lineages and the admixture of two previously separate sublineages (Atlantic and Danubian) in the Western lineage. Bayesian structure analysis as well as FCA results roughly corresponded to the mtDNA‐based structure, separating the sampled individuals into almost non‐overlapping groups. Main conclusions Our results support hypotheses suggesting origins of extant lineages of freshwater fishes in multiple refugia and the subsequent post‐glacial colonization of Europe via different routes. We confirmed the previously proposed two‐step expansion scenario from the Danube refuge, the existence of a secondary (Atlantic) refuge during the last glaciation (probably in the Rhone River) and population expansion of this lineage. Conspicuous divergences among Mediterranean populations reflect their different origin, as well as their low contribution to the recent genetic pool of chub in central Europe.     

Phylogeography of the freshwater red alga Sirodotia (Batrachospermales,Rhodophyta) in Brazil

Considering the lack of knowledge on genetic variation on members of the freshwater red algal of the order Batrachospermales in tropical regions, phylogeographic patterns in Sirodotia populations were investigated using two mitochondrial regions: the cox2‐3 spacer and partial cox1 gene (barcode). Individuals identified as Sirodotia delicatula were analyzed from 14 stream segments across its distribution in Brazil. Phylogenetic analyses based on the ribulose‐1,5‐bisphosphate carboxylase/oxygenase large sub‐unit gene showed three clades, one representing S. delicatula, from all locations in southeastern Brazil and other regions from Brazil. The remaining samples formed two clades, which were highly divergent and distantly positioned from those of S. delicatula: 2.5–2.7% and 3.4–3.7%. This level of variation would warrant the species split of these taxa from mid‐western Brazil. A total of eight cox2‐3 spacer and nine cox1 haplotypes were observed among the 122 individuals studied. One location had two cox2‐3 haplotypes and three locations had two cox1 haplotypes; all others had a single dominant haplotype each. The existence of high intraspecific genetic variation among individuals of distinct locations (several haplotypes), but little variation within a location seems to be a pattern for the Batrachospermales. Haplotype networks showed low variation among the haplotypes from southeastern Brazil (10 locations with divergence of 0.3–1.1% for cox2‐3, 0.1–0.3% for cox1) and high variation among the haplotypes from the mid‐west region (four locations, 4.0–9.3% for cox2‐3, 6.2–8.4% for cox1). Thus, the present data clearly suggest the existence of cryptic species in Sirodotia in Brazil.     

Glacial survival or late glacial colonization? Phylogeography of the root vole (Microtus oeconomus) in north‐west Norway

Aim It has been proposed that the root vole subspecies, Microtus oeconomus finmarchicus, survived the last glacial period on islands on the north‐west coast of Norway. The Norwegian island of Andøya may have constituted the only site with permanent ice‐free conditions. Geological surveys and fossil finds from Andøya demonstrate that survival throughout the last glacial maximum was probably possible for some plants and animals. In this study we aim to infer the recent evolutionary history of Norwegian root vole populations and to evaluate the glacial survival hypothesis. Methods DNA sequence variation in the mitochondrial cytochrome b gene was studied in 46 root voles from 19 localities. Location Northern Fennoscandia and north‐west Russia with a focus on islands on the north‐west coast of Norway. Results The phylogeographical analyses revealed two North European phylogroups labelled ‘Andøya’ and ‘Fennoscandia’. The Andøya phylogroup contained root voles from the Norwegian islands of Andøya, Ringvassøya and Reinøya and two localities in north‐west Russia. The Fennoscandian phylogroup encompassed root voles from the three Norwegian islands of Kvaløya, Håkøya and Arnøya and the remaining specimens from Norway, northern Sweden and Finland. Nucleotide diversity within the Andøya and Fennoscandian phylogroups was similar, ranging from 0.5% to 0.7%. Main conclusions Both our genetic data and previously published morphological data are consistent with in situ glacial survival of root voles on Andøya during the last glacial maximum. However, the level of genetic diversity observed in the extant island populations, the past periods of severe climatic conditions on Andøya and the ecology of the root vole are somewhat difficult to reconcile with this model. A biogeographical scenario involving late glacial recolonization along the northern coasts of Russia and Norway therefore represents a viable alternative. Our results demonstrate that complex recolonization and extinction histories can generate intricate phylogeographical patterns and relatively high levels of genetic variation in northern populations.     

A multi-compartmented glacial refugium in the northern Rocky Mountains: Evidence from the phylogeography of <Emphasis Type="Italic">Cardamine constancei</Emphasis> (Brassicaceae)

The age and origin of the mesic coniferous forest ecosystem of the Pacific Northwest of North America have long been the subject of debate by biogeographers. Cardamine constancei, an endemic of the Rocky Mountain segment of this ecosystem, was subjected to phylogeographic analysis to test explicit hypotheses on the age of the ecosystem. We have predicted genetic homogeneity among river drainages if C. constancei and other associated species migrated into the region after glaciation, in contrast to the genetic differentiation that may have accrued if the species and its ecosystem have long survived in the relatively warm river canyons south of glaciation. We detected 19 haplotypes with divergence up to 1.5%, and they comprise 4 well-differentiated cpDNA clades. These clades are allopatric except for two haplotypes from the lower Clearwater clade that appear to have dispersed north into partial sympatry with the clade endemic to St.␣Joe River. The divergence and distribution of these clades is consistent with the existence of a complex glacial refugium with at least four compartments. The surprisingly high cpDNA diversity within this species suggests that conservation of mesic coniferous forest ecosystems in the region warrant a conservation plan that accounts for the historically imposed spatial structure of genetic diversity. We are currently testing our phylogeographic hypotheses by the comparative analyses of a suite of plants, animals and fungi.     

Plio‐Pleistocene diversification and genetic population structure of an endangered lizard (the Blue Mountains water skink,Eulamprus leuraensis) in south‐eastern Australia

Aim Although climatic fluctuations occurred world‐wide during the Pleistocene, the severity of glacial and drought events – and hence their influence on animal and plant biogeography – differed among regions. Many Holarctic species were forced to warmer‐climate refugia during glacial periods, leaving the genetic signature of recent expansion and gene flow among modern‐day populations. Montane south‐eastern Australia experienced less extreme glaciation, but the effects of drier and colder climatic conditions over this period on biotic distributions, and hence on the present‐day genetic structure of animal and plant populations, are poorly known. Location South‐eastern Australia. Methods The endangered Blue Mountains water skink (Eulamprus leuraensis) is a viviparous lizard known from fewer than 40 isolated small swamps at 560–1060 m elevation in south‐eastern Australia. We conducted molecular phylogenetic, dating and population genetics analyses using the mitochondrial NADH dehydrogenase 4 (ND4) of 224 individuals of E. leuraensis sampled across the species’ distribution. Results Ancient divergences in haplotype groups between lizards from the Blue Mountains and the Newnes Plateau, and strong genetic differences, even between swamps separated by only a few kilometres, suggest that the species has persisted as a series of relatively isolated populations within its current distribution for about a million years. Presumably, habitat patches similar to current‐day swamps persisted throughout glacial–interglacial cycles in this region, allowing the development of high levels of genetic structuring within and among present‐day populations. Main conclusions Our results suggest that less extreme glacial conditions occurred in the Southern Hemisphere compared with the Northern Hemisphere, allowing cold‐adapted species (such as E. leuraensis) to persist in montane areas. However, additional studies are needed before we can assemble a comprehensive view of the impact of Pleistocene climatic variation on the phylogeography of Southern Hemisphere taxa.     

中国南海硇洲岛潮间带产胞外蛋白酶的可培养海洋真菌多样性

【目的】研究中国南海硇洲岛潮间带产胞外蛋白酶的可培养海洋真菌多样性。【方法】从中国南海硇洲岛潮间带采集海水和沉积物样品,采用分离培养、蛋白酶生产菌平板检测法和基于内转录间隔区1-5.8S rRNA基因内转录间隔区2(ITS1-5.8S-ITS2)序列的系统进化分析法,研究产胞外蛋白酶真菌的多样性。【结果】采用50%海水配制的马铃薯葡萄糖琼脂(PDA)固体培养板从所采集的样品中分离、纯化并收集了198株真菌分离株,并采用ITS1-5.8S-ITS2序列PCR扩增、测序、BLAST和系统进化分析的方法成功鉴定了其中的178株。其中,有10株的ITS1-5.8S-ITS2序列与其在NCBI数据库中最匹配的ITS1-5.8S-ITS2序列的一致性<97,表明它们有可能是新的物种;其余168株的ITS1-5.8S-ITS2序列与NCBI数据库中已存在的相关ITS1-5.8S-ITS2序列的一致性均≥98%。这178株真菌归属为66个种,分布在子囊菌门和担子菌门的6纲,16个目,27个科的45个属中。其中的主要属为青霉菌属,占28.70%;其次为曲霉属,占11.24%。有83株真菌在加在脱脂奶粉的PDA固体培养板上的菌落周围有一透明圈,表明其可产生分泌胞外蛋白酶。【结论】从中国南海硇洲岛潮间带共分离、鉴定和收集了178株真菌,其中10株可能是新的物种,83株为胞外蛋白酶生产菌。     

Phylogeography of the burnet moth Zygaena transalpina complex: molecular and morphometric differentiation suggests glacial refugia in Southern France,Western France and micro‐refugia within the Alps

Patterns of common recolonization routes from glacial refugia to Central Europe during the Pleistocene are generalized to paradigms of postglacial recolonization in Europe. Recent studies indicate, however, that the actual phylogeographic history of many species might be more complex and cannot be simplified to generalized patterns. Burnet moths of the Zygaena transalpina complex represent a group of closely related taxa, which are considered as a typical example for these generalized patterns. At present, three groups are recognized that are assumed to have spread from three classical refugia in Western Europe, Italy and the Balkans to Central Europe. Here, we re‐investigate their phylogeography using a combined molecular and morphometric approach. Phylogenetic and nested clade phylogeographic analyses of 476 samples from 55 localities taken from Southern and Central Europe reveal that the Zygaena transalpina complex consists of three distinct haplotype clusters, which geographically roughly correspond to possible refugia in Western Europe, Italy and the Balkans. A synthesis of the data with a geometric morphometry dataset of 425 specimens from 46 localities corroborates this molecular result but differs in several aspects. Important new aspects are multiple refugia of the western ‘hippocrepidis’ branch and micro‐habitats within the Alps of the central ‘transalpina’ branch. Further, our results display a more complex phylogeographic pattern for this species complex, which is not tractable with a rigid, generalized pattern.     

Congruent phylogeographic patterns in a young radiation of live‐bearing marine snakes: Pleistocene vicariance and the conservation implications of cryptic genetic diversity

Aim

To investigate phylogeographic patterns among and within co‐occurring sea snake species from Australia's endemic viviparous Aipysurus lineage, which includes critically endangered species, and evaluate the conservation implications of geographically structured patterns of genetic divergence and diversity.

Location

Australia's tropical shallow water marine environments spanning four regions: Great Barrier Reef (GBR), Gulf of Carpentaria (GoC), Timor Sea (TS) and coastal WA (WAC).

Methods

Samples from >550 snakes representing all nine nominal Aipysurus group species were obtained from throughout their known Australian ranges. Coalescent phylogenetic analyses and Bayesian molecular dating of mitochondrial DNA, combined with Bayesian and traditional population genetic analyses of 11 microsatellite loci, were used to evaluate genetic divergence and diversity.

Results

Mitochondrial DNA revealed highly congruent phylogeographic breaks among co‐occurring species, largely supported by nuclear microsatellites. For each species, each region was characterized by a unique suite of haplotypes (phylogroups). Divergences between the TS, GoC and/or GBR were invariably shallow and dated as occurring 50,000–130,000 years ago, coinciding with the cyclic Pleistocene emergence of the Torres Strait land bridge. By contrast, sea snakes from coastal WA were consistently highly divergent from other regions and dated as diverging 178,000–526,000 years ago, which was not associated with any known vicariant events.

Main Conclusions

Previously unappreciated highly divergent sea snake lineages in coastal WA potentially represent cryptic species, highlighting this region as a high‐priority area for conservation. The cyclic emergence of the Torres Strait land bridge is consisted with observed divergences between the TS, GoC and/or GBR; however, processes involved in the earlier divergences involving the WAC remain to be determined. The observed strong population genetic structures (as surrogates for dispersal) indicate that sea snakes have limited potential to reverse population declines via replenishment from other sources over time frames relevant to conservation.

     

Phylogeography of the freshwater red alga B atrachospermum viride‐brasiliense (Rhodophyta,Batrachospermales)

Phylogeography of B atrachospermum viride‐brasiliense was investigated using two mitochondrial regions: the cox2‐3 spacer and the barcode region of cox1 gene. Eighty‐seven individuals were analyzed from nine stream segments throughout its distribution in Brazil. Ten cox2‐3 spacer and nine cox1 haplotypes were observed among the individuals studied (87 vs. 43, respectively). Divergences among haplotypes were relatively low (≤2.4% for cox2‐3 and ≤1.8% for cox1). Most locations have a single haplotype, whereas only two locations had two haplotypes for both markers. The haplotype network for cox2‐3 showed a phylogeographic trend from the south towards the southeast with haplotypes from the southeast more closely related. For cox1 a trend from the southeast spreading towards the south and north was revealed, with the southern haplotypes more closely associated. Results clearly indicated that B . viride‐brasiliense represents a single species and the phylogeographic pattern consisted of a closely connected group of haplotypes from southern and southeastern Brazil. Levels of intra‐ and inter‐population variation were similar for the two markers with slightly higher values for cox2‐3. The trend observed in this study is similar to that in other members of Batrachospermales with little variation within a stream segment (one or two haplotypes) and more distant haplotypes showing higher divergences. This pattern could be attributed to the fact that colonization of a site might be rare by a single event with subsequent proliferation of the population. The geographic distribution of B . viride‐brasiliense was interpreted according to the biogeographic models proposed for South America being limited to three morpho‐climatic domains or biogeographic provinces: tropical Atlantic rainforest, sub‐tropical rainforest and cerrado (Brazilian savannah).     

Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island South‐East Asian Sus species during the Plio‐Pleistocene climatic fluctuations

In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here, we investigate this issue using genome sequences of three pig (Sus) species, two of which are found on islands of the Sunda‐shelf shallow seas in Island South‐East Asia (ISEA). A previous study revealed signatures of interspecific admixture between these Sus species (Genome biology, 14 , 2013, R107). However, the timing, directionality and extent of this admixture remain unknown. Here, we use a likelihood‐based model comparison to more finely resolve this admixture history and test whether it was mediated by humans or occurred naturally. Our analyses suggest that interspecific admixture between Sunda‐shelf species was most likely asymmetric and occurred long before the arrival of humans in the region. More precisely, we show that these species diverged during the late Pliocene but around 23% of their genomes have been affected by admixture during the later Pleistocene climatic transition. In addition, we show that our method provides a significant improvement over D‐statistics which are uninformative about the direction of admixture.     

Phylogeography of the cold‐water barnacle Chthamalus challengeri in the north‐western Pacific: effect of past population expansion and contemporary gene flow

Aim Phylogeographical patterns of marine organisms in the north‐western Pacific are shaped by the interaction of past sea‐level fluctuations during glacial maxima and present‐day gene flow. This study examines whether observed population differentiation in the barnacle Chthamalus challengeri, which is endemic to the north‐western Pacific, can be explained by the interactions between historical glacial events and patterns of contemporary gene flow. Location Eleven locations in the north‐western Pacific. Methods Partial sequences of mitochondrial cytochrome c oxidase subunit I (COI), 12S, 16S and nuclear internal transcribed spacer 1 (ITS1) were obtained from 312 individuals. Parsimony haplotype networks and analysis of molecular variance (AMOVA) were used to determine whether the observed genetic structure corresponds to marine provinces (Kuroshio Current and China Sea Coastal Provinces), zoogeographical zones (oriental and Japan warm‐temperate zones) and/or potential refugial areas (Sea of Japan and East China Sea) in the north‐western Pacific. Neutrality tests, mismatch distribution analysis and Bayesian skyline plots were used to infer the demographic history of C. challengeri. Results In total, 312, 117, 182 and 250 sequences were obtained for COI, 12S, 16S and ITS1, respectively. A panmictic population was revealed, which did not conform to the ‘isolation by distance’ model. None of the a priori population groupings based on marine provinces, zoogeographical zones or potential refugial areas was associated with observed genetic patterns. Significant negative values from neutrality tests and the unimodal mismatch distribution and expansion patterns in Bayesian skyline plots for the COI and 16S data sets indicate a population expansion in the mid‐Pleistocene (c. 200 ka). Information from the fossil record suggests that there has been a northward range shift of this species from the East China Sea or the Palaeo‐Pacific coast of Japan to the Sea of Japan since the mid‐Pleistocene. Main conclusions Chthamalus challengeri has experienced a population expansion and range shift since the mid‐Pleistocene. The observed lack of population differentiation can be explained by this past population expansion and present‐day wide‐scale larval dispersal (owing to the long planktonic larval duration) across marine provinces, which have led to the successful establishment of the species in different zoogeographical zones and habitats.     

Delineation of Two Sibling Red Algal Species,Gracilaria Gracilis and Gracilaria Dura (Gracilariales,Rhodophyta), Using Multiple DNA Markers: Resurrection of the Species G. Dura Previously Described in the Northern Atlantic 200 Years Ago1

Molecular markers belonging to the three different genomes, mitochondrial (cox2‐cox3 spacer), plastid (rbcL), and nuclear (internal transcribed spacer [ITS] 2 region), were used to compare samples of the two morphologically related species Gracilaria gracilis (Stackh.) Steentoft, L. M. Irvine et Farnham and G. dura (C. Agardh) J. Agardh collected along Atlantic coasts. In northern Europe, the distinction between these two species is ambiguous, and they are currently recognized under the single name of G. gracilis. The low but congruent patterns of genetic divergence observed for markers of the three genomic compartments highly suggest that these two taxa correspond effectively to two different genetic entities as previously described 200 years ago, based on morphological traits. However, thanks to the combination of different DNA markers, occurrence of “incongruent” cytotypes (i.e., mitotypes of G. dura associated with chlorotypes of G. gracilis) in individuals collected from Brittany, suggests interspecific hybridization between the two sibling species studied.