Evolution of the Fucaceae (Phaeophyceae) inferred from nrDNA-ITS

Sequences of the internal transcribed spacer region (ITS-1, 5.8S, and ITS-2) of nuclear ribosomal DNA were obtained from 16 species representing all six genera of Fucaceae (Ascophyllum, Fucus, Hesperophycus, Pelvetia, Pelvetiopsis, and Xiphophora) plus one outgroup (Hormosira). Parsimony analysis indicated that the family Fucaceae is monophyletic and that the northern hemisphere taxa are highly divergent from the only southern hemisphere genus, Xiphophora. The genus Pelvetia is not monophyletic because the European P. canaliculata is more closely related to Fucus, Hesperophycus, and Pelvetiopsis than to other Pelvetia species. We establish Silvetia, gen. nov. and transfer the 3 Pacific species of Pelvetia to the new genus. Fucus is monophyletic and not ancestral in the Fucaceae. The ITS sequences identified two strongly supported lineages within Fucus, one with F. serratus sister to the clade containing F. gardneri, F. distichus, and F. evanescens and a second including F. vesiculosus, F. spiralis, F. ceranoides, and F. virsoides. The ITS was not useful for resolving relationships within each of these clusters and between populations of F. vesiculosus. Within-individual variation in ITS sequences is high in Fucus, a derived genus, compared to Ascophyllum, a more ancestral genus. Mapping of the two characters that form the basis of Powell’s model for speciation in the Fucaceae showed that 1) number of eggs per oogonium has not followed a gradual reduction and that 2) monoecy/dioecy has changed several times during evolution of this family

Fine-scale genetic breaks driven by historical rangedynamics and ongoing density-barrier effects in theestuarine seaweed Fucus ceranoides L.

Factors promoting the emergence of sharp phylogeographic breaks include restricted dispersal, habitat discontinuity, physical barriers, disruptive selection, mating incompatibility, genetic surfing and secondary contact. Disentangling the role of each in any particular system can be difficult, especially when species are evenly distributed across transition zones and dispersal barriers are not evident. The estuarine seaweed Fucus ceranoides provides a good example of highly differentiated populations along its most persistent distributional range at the present rear edge of the species distribution, in NW Iberia. Intrinsic dispersal restrictions are obvious in this species, but have not prevented F. ceranoides from vastly expanding its range northwards following the last glaciation, implying that additional factors are responsible for the lack of connectivity between neighbouring southern populations. In this study we analyze 22 consecutive populations of F. ceranoides along NW Iberia to investigate the processes generating and maintaining the observed high levels of regional genetic divergence. Results Variation at seven microsatellite loci and at mtDNA spacer sequences was concordant in revealing that Iberian F. ceranoides is composed of three divergent genetic clusters displaying nearly disjunct geographical distributions. Structure and AFC analyses detected two populations with an admixed nuclear background. Haplotypic diversity was high in the W sector and very low in the N sector. Within each genetic cluster, population structure was also pervasive, although shallower. Conclusions The deep divergence between sectors coupled with the lack of support for a role of oceanographic barriers in defining the location of breaks suggested 1) that the parapatric genetic sectors result from the regional reassembly of formerly vicariant sub-populations, and 2) that the genetic discontinuities at secondary contact zones (and elsewhere) are maintained despite normal migration rates. We conclude that colonization and immigration, as sources of gene-flow, have very different genetic effects. Migration between established populations is effectively too low to prevent their differentiation by drift or to smooth historical differences inherited from the colonization process. F. ceranoides, but possibly low-dispersal species in general, appear to be unified to a large extent by historical, non-equilibrium processes of extinction and colonization, rather than by contemporary patterns of gene flow.Peer Reviewe

Driving south: a multi-gene phylogeny of the brown algal family Fucaceae reveals relationships and recent drivers of a marine radiation

<p>Abstract</p> <p>Background</p> <p>Understanding the processes driving speciation in marine ecosystems remained a challenge until recently, due to the unclear nature of dispersal boundaries. However, recent evidence for marine adaptive radiations and ecological speciation, as well as previously undetected patterns of cryptic speciation is overturning this view. Here, we use multi-gene phylogenetics to infer the family-level evolutionary history of Fucaceae (intertidal brown algae of the northern Pacific and Atlantic) in order to investigate recent and unique patterns of radiative speciation in the genus <it>Fucus </it>in the Atlantic, in contrast with the mainly monospecific extant genera.</p> <p>Results</p> <p>We developed a set of markers from 13 protein coding genes based on polymorphic cDNA from EST libraries, which provided novel resolution allowing estimation of ancestral character states and a detailed reconstruction of the recent radiative history. Phylogenetic reconstructions yielded similar topologies and revealed four independent trans-Arctic colonization events by Fucaceae lineages, two of which also involved transitions from hermaphroditism to dioecy associated with Atlantic invasions. More recently, reversion of dioecious ancestral lineages towards hermaphroditism has occurred in the genus <it>Fucus</it>, particularly coinciding with colonization of more extreme habitats. Novel lineages in the genus <it>Fucus </it>were also revealed in association with southern habitats. These most recent speciation events occurred during the Pleistocene glaciations and coincided with a shift towards selfing mating systems, generally southward shifts in distribution, and invasion of novel habitats.</p> <p>Conclusions</p> <p>Diversification of the family occurred in the Late-Mid Miocene, with at least four independent trans-Artic lineage crossings coincident with two reproductive mode transitions. The genus <it>Fucus </it>arose in the Pliocene but radiated within a relatively short time frame about 2.5 million years ago. Current species distributions of <it>Fucus </it>suggest that climatic factors promoted differentiation between the two major clades, while the recent and rapid species radiation in the temperate clade during Pleistocene glacial cycles coincided with several potential speciation drivers.</p

Temporal windows of reproductive opportunity reinforce species barriers in a marine broadcast spawning assemblage

Prezygotic isolating mechanisms act to limit hybridization and maintain the genetic identity of closely-related species. While synchronous intraspecific spawning is a common phenomenon amongst marine organisms and plays an important role in reproductive success, asynchronous spawning between potentially hybridizing lineages may also be important in maintaining species boundaries. We tested this hypothesis by comparing reproductive synchrony over daily to hourly timescales in a sympatric assemblage of intertidal fucoid algae containing selfing hermaphroditic (Fucus spiralis and Fucus guiryi) and dioecious (Fucus vesiculosus and Fucus serratus) species. Our results confirm that gametes are released on semi-lunar cycles in all species. However, sister species with different mating systems showed asynchronous spawning at finer circadian timescales, thus providing evidence for a partial reproductive barrier between hermaphroditic and dioecious species. Finally, our data also emphasize the ecological, developmental, and/or physiological constraints that operate to restrict reproduction to narrow temporal windows of opportunity in the intertidal zone and more generally the role of ecological factors in marine speciation

Polymorphic microsatellite markers in the brown seaweed Fucus vesiculosus

Background: Fucus vesiculosus is a brown seaweed dominant on temperate rocky shores of the northern hemisphere and, is typically distributed in the mid-upper intertidal zone. It is an external fertilizer that reproduces sexually, providing an excellent model to address conflicting theories related to mating systems and sexual selection. Microsatellite markers have been reported for several Fucus species, however the genomic libraries from where these markers have been isolated, have originated from two or more species pooled together (F. vesiculosus and F. serratus in one library; F. vesiculosus, F. serratus and Ascophyllum nodosum in a second library), or when the genomic DNA originated from only one species it was from Fucus spiralis. Although these markers cross-amplify F. vesiculosus individuals, the level of polymorphism has been low for relatedness studies. Findings: The microsatellite markers described here were obtained from an enriched genomic library, followed by 454 pyrosequencing. A total of 9 microsatellite markers were tested across 44 individuals from the North of Portugal. The mean number of alleles across loci was 8.7 and the gene diversity 0.67. Conclusions: The high variability displayed by these microsatellite loci should be useful for paternity analysis, assessing variance of reproductive success and in estimations of genetic variation within and between populations.Fundação para a Ciência e Tecnologi

Lack of fine-scale genetic structure and distant mating in natural populations of Fucus vesiculosus

Fine-scale spatial genetic structure (SGS) within populations reflects the dispersal behaviour of genes and individuals. Here we studied very small-scale SGS and mating patterns in the brown seaweed Fucus vesiculosus, a dioecious marine broadcast spawner with immediate settlement upon gamete release, which is predicted to strongly restrict gene flow. We estimated SGS, inbreeding and kinship for adults and recruits from habitats with contrasting exposures and patchiness (open coast and estuarine ecosystems) using microsatellite loci. Heterozygote deficiency was found for most adult populations but it was even higher for recruits, indicating inbreeding depression. At the fine spatial resolution of this study there was no spatial genetic structuring for 3 of the 5 populations studied across different habitats. Habitat could not explain the unrestricted gene flow in some populations. In the kinship analyses, we identified more putative mothers than fathers, suggesting that male gamete dispersal mediates gene flow at broader distances. However, the vast majority of the parents of the recruits could not be found among the adults sampled nearby, indicating unrestricted gene flow at these small scales. We propose 3 nonexclusive hypotheses for our findings: (1) unrestricted gene flow, (2) inbreeding depression eliminating most inbred individuals resulting from nearby related parents, (3) temporal Wahlund effects, mediated by a hypothetic genetic pool of a bank of microscopic forms persisting from previous generations

The rediscovery of Caulerpa prolifera in Ria Formosa, Portugal, 60 years after the previous record

The westernmost occurrence of Caulerpa prolifera on the Atlantic European coast has been accepted in recent decades, to be Huelva province, southern Spain. In April 2011, this species was found in Ria Formosa, southern Portugal, extending its westernmost limit along the Iberian Peninsula coastline. In the course of research into this species it was discovered that this alga had been found in Ria Formosa in the 19th century by the naturalist Welwitsch and subsequently in the 1930s by others but it was never found in the many field studies conducted in Ria Formosa during the past few decades. The species had therefore either become extinct in the area or persisted as a cryptic undetected stage. In order to investigate the source of colonization and to verify the genetic identity, a partial cpDNA region (tufA gene) was sequenced. Comparisons of nucleotide similarity in sequences from the Ria Formosa and from populations of the Atlantic and Mediterranean confirmed the Caulerpa prolifera identification and gave clues about a possible origin of this population as deriving from expansion of a Mediterranean source rather than one from the western Atlantic

Bio-ORACLE v2.0 : extending marine data layers for bioclimatic modelling

Motivation: The availability of user-friendly, high-resolution global environmental datasets is crucial for bioclimatic modelling. For terrestrial environments, WorldClim has served this purpose since 2005, but equivalent marine data only became available in 2012, with pioneer initiatives like Bio-ORACLE providing data layers for several ecologically relevant variables. Currently, the available marine data packages have not yet been updated to the most recent Intergovernmental Panel on Climate Change (IPCC) predictions nor to present times, and are mostly restricted to the top surface layer of the oceans, precluding the modelling of a large fraction of the benthic diversity that inhabits deeper habitats. To address this gap, we present a significant update of Bio-ORACLE for new future climate scenarios, present-day conditions and benthic layers (near sea bottom). The reliability of data layers was assessed using a cross-validation framework against in situ quality-controlled data. This test showed a generally good agreement between our data layers and the global climatic patterns. We also provide a package of functions in the R software environment (sdmpredictors) to facilitate listing, extraction and management of data layers and allow easy integration with the available pipelines for bioclimatic modelling. Main types of variable contained: Surface and benthic layers for water temperature, salinity, nutrients, chlorophyll, sea ice, current velocity, phytoplankton, primary productivity, iron and light at bottom. Spatial location and grain: Global at 5 arcmin (c.0.08 degrees or 9.2 km at the equator). Time period and grain: Present (2000-2014) and future (2040-2050 and 2090-2100) environmental conditions based on monthly averages. Major taxa and level of measurement: Marine biodiversity associated with sea surface and epibenthic habitats. Software format: ASCII and TIFF grid formats for geographical information systems and a package of functions developed for R software

Genetic flow directionality and geographical segregation in a Cymodocea nodosa genetic diversity network

We analyse a large data set of genetic markers obtained from populations of Cymodocea nodosa, a marine plant occurring from the East Mediterranean to the Iberian-African coasts in the Atlantic Ocean. We fully develop and test a recently introduced methodology to infer the directionality of gene flow based on the concept of geographical segregation. Using the Jensen-Shannon divergence, we are able to extract a directed network of gene flow describing the evolutionary patterns of Cymodocea nodosa. In particular we recover the genetic segregation that the marine plant underwent during its evolution. The results are confirmed by natural evidence and are consistent with an independent cross analysis

Shift happens: trailing edge contraction associated with recent warming trends threatens a distinct genetic lineage in the marine macroalga Fucus vesiculosus

Significant effects of recent global climate change have already been observed in a variety of ecosystems, with evidence for shifts in species ranges, but rarely have such consequences been related to the changes in the species genetic pool. The stretch of Atlantic coast between North Africa and North Iberia is ideal for studying the relationship between species distribution and climate change as it includes the distributional limits of a considerable number of both cold- and warm-water species. We compared temporal changes in distribution of the canopy-forming alga Fucus vesiculosus with historical sea surface temperature (SST) patterns to draw links between range shifts and contemporary climate change. Moreover, we genetically characterized with microsatellite markers previously sampled extinct and extant populations in order to estimate resulting cryptic genetic erosion. Results Over the past 30 years, a geographic contraction of the southern range edge of this species has occurred, with a northward latitudinal shift of approximately 1,250 km. Additionally, a more restricted distributional decline was recorded in the Bay of Biscay. Coastal SST warming data over the last three decades revealed a significant increase in temperature along most of the studied coastline, averaging 0.214°C/decade. Importantly, the analysis of existing and extinct population samples clearly distinguished two genetically different groups, a northern and a southern clade. Because of the range contraction, the southern group is currently represented by very few extant populations. This southern edge range shift is thus causing the loss of a distinct component of the species genetic background. Conclusions We reveal a climate-correlated diversity loss below the species level, a process that could render the species more vulnerable to future environmental changes and affect its evolutionary potential. This is a remarkable case of genetic uniqueness of a vanishing cryptic genetic clade (southern clade).Peer Reviewe