Showing papers by "Pablo Vargas published in 2010"
TL;DR: The radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently, however, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.
Abstract: Studies of the North American columbines (Aquilegia, Ranunculaceae) have supported the view that adaptive radiations in animal-pollinated plants proceed through pollinator specialisation and floral differentiation. However, although the diversity of pollinators and floral morphology is much lower in Europe and Asia than in North America, the number of columbine species is similar in the three continents. This supports the hypothesis that habitat and pollinator specialisation have contributed differently to the radiation of columbines in different continents. To establish the basic background to test this hypothesis, we expanded the molecular phylogeny of the genus to include a representative set of species from each continent. Our results suggest that the diversity of the genus is the result of two independent events of radiation, one involving Asiatic and North American species and the other involving Asiatic and European species. The ancestors of both lineages probably occupied the mountains of south-central Siberia. North American and European columbines are monophyletic within their respective lineages. The genus originated between 6.18 and 6.57 million years (Myr) ago, with the main pulses of diversification starting around 3 Myr ago both in Europe (1.25–3.96 Myr ago) and North America (1.42–5.01 Myr ago). The type of habitat occupied shifted more often in the Euroasiatic lineage, while pollination vectors shifted more often in the Asiatic-North American lineage. Moreover, while allopatric speciation predominated in the European lineage, sympatric speciation acted in the North American one. In conclusion, the radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently. However, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.
78 citations
TL;DR: Comparative phylogeography of the Cistus species leads us to interpret a general pattern of active colonization surpassing Mediterranean barriers, and provides molecular evidence for multiple colonization patterns in the course of successful adaptation of Cistsus species to Mediterranean habitats.
Abstract: The lack of a comparative approach makes it impossible to determine the main factors influencing colonization and evolution in plants. Here we conducted the first comparative study of a characteristic Mediterranean lineage (white-flowered Cistus) taking advantage of its well-known phylogenetic relationships. A two-scale approach was applied to address the hypothesis of higher levels of isolation in mountain than in lowland species. First, a time-calibrated phylogeny using plastid sequences of Cistaceae suggested that the origin of Cistus species postdated both the refilling of the Mediterranean Sea (5.59–5.33 Ma) and the onset of the Mediterranean climate (3.2 Ma). Two hundred and sixty-three additional, plastid sequences from 111 populations showed different numbers of haplotypes in C. laurifolius (7), C. monspeliensis (2) and C. salviifolius (7). Although haplotype sharing among disjunct populations was observed in all species, phylogeographic analyses revealed haplotype lineages exclusive to Europe or Africa only in the mountain species (C. laurifolius). Isolation by either geographical distance or sea barriers was not significantly supported for the lowland species (C. monspeliensis; C. ladanifer from a previous study). The same is true for the less habitat-specific species of the lineage (C. salviifolius). Comparative phylogeography of the Cistus species leads us to interpret a general pattern of active colonization surpassing Mediterranean barriers. In contrast, ecological conditions (precipitation, temperature, soils) appear to have determined the distribution of the Cistus species of Mediterranean mountains. This study further provides molecular evidence for multiple colonization patterns in the course of successful adaptation of Cistus species to Mediterranean habitats.
69 citations
TL;DR: This empirical study shows that extensive gene flow, particularly mediated by seeds, can ameliorate population subdivision resulting from extinction–recolonization dynamics and isolation by distance in a wind‐pollinated, zoochorous tree.
Abstract: Theoretical and empirical studies suggest that geographical isolation and extinction-recolonization dynamics are two factors causing strong genetic structure in metapopulations, but their consequences in species with high dispersal abilities have not been tested at large scales. Here, we investigated the effect of population age structure and isolation by distance in the patterns of genetic diversity in a wind-pollinated, zoochorous tree (Olea europaea subsp. guanchica) sporadically affected by volcanic events across the Canarian archipelago. Genetic variation was assessed at six nuclear microsatellites (nDNA) and six chloroplast fragments (cpDNA) in nine subpopulations sampled on four oceanic islands. Subpopulations occurring on more recent substrates were more differentiated than those on older substrates, but within-subpopulation genetic diversity was not significantly different between age groups for any type of marker. Isolation-by-distance differentiation was observed for nDNA but not for cpDNA, in agreement with other metapopulation studies. Contrary to the general trend for island systems, between-island differentiation was extremely low, and lower than differentiation between subpopulations on the same island. The pollen-to-seed ratio was close to one, two orders of magnitude lower than the average estimated for other wind-pollinated, animal-dispersed plants. Our results showed that population turnover and geographical isolation increased genetic differentiation relative to an island model at equilibrium, but overall genetic structure was unexpectedly weak for a species distributed among islands. This empirical study shows that extensive gene flow, particularly mediated by seeds, can ameliorate population subdivision resulting from extinction-recolonization dynamics and isolation by distance.
62 citations
TL;DR: The results support the vicariance hypothesis for population disjunctions in the Iberian Peninsula, in which an ancestral, widespread species could have undergone differentiation by Quaternary interglacial fragmentation, and indicate a late Pleistocene diversification of R. sect.
Abstract: Reseda sect. Claucoreseda is a monophyletic group composed of five endemic tetraploid species with a disjunct distribution in the high mountains and plateaus of the Iberian Peninsula and Morocco. It was previously suggested that range shifts induced by Quaternary glaciations played an important role in the speciation of the group. We studied the evolution of R. sect. Glaucoreseda in order to infer historical range dynamics and speciation processes, and to understand current distributional patterns. Phylogeographic analyses were performed using nuclear ribosomal ITS and plastid trnL-F and rps16 sequences. Cloning of additive ITS sequences was carried out to elucidate the origin of intra-individual polymorphisms. A dated phylogeny based on ITS and cpDNA (rbcL, matK, trnL-F) sequences was used to estimate divergence times of R. sect. Glaucoreseda. Time estimates using Penalized Likelihood analyses indicate a late Pleistocene diversification of R. sect. Glaucoreseda. Incomplete lineage sorting of ancestral polymorphisms due to recent divergence, rather than rampant hybridisation, is suggested as the main cause of the phylogenetic incongruence detected between nuclear and plastid datasets. Our results support the vicariance hypothesis for population disjunctions in the Iberian Peninsula, in which an ancestral, widespread species could have undergone differentiation by Quaternary interglacial fragmentation. In contrast, long-distance dispersal across the Strait of Gibraltar may have been involved in the colonisation of North African plateaus by R. battandieri.
59 citations
TL;DR: Phylogenetic and network analyses of cpDNA variation revealed the monophyly of the species and an ancestral haplotype contained in populations of the eastern Mediterranean, which accord with the ‘tabula rasa’ hypothesis in which a recent and rapid colonization of northern Europe took place from the western Mediterranean after the Last Glacial Maximum.
Abstract: Coastal plants are ideal models for studying the colonization routes of species because of the simple linear distributions of these species. Carex extensa occurs mainly in salt marshes along the Mediterranean and European coasts. Variation in cpDNA sequences, amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs) of 24 populations were analysed to reconstruct its colonization history. Phylogenetic relationships indicate that C. extensa together with the South American Carex vixdentata and the southern African Carex ecklonii form a monophyletic group of halophilic species. Analyses of divergence times suggest that early lineage diversification may have occurred between the late Miocene and the late Pliocene (Messinian crisis). Phylogenetic and network analyses of cpDNA variation revealed the monophyly of the species and an ancestral haplotype contained in populations of the eastern Mediterranean. The AFLP and SSR analyses support a pattern of variation compatible with these two lineages. These analyses also show higher levels of genetic diversity and differentiation in the eastern population group, which underwent an east-to-west Mediterranean colonization. Quaternary climatic oscillations appear to have been responsible for the split between these two lineages. Secondary contacts may have taken place in areas near the Ligurian Sea in agreement with the gene flow detected in Corsican populations. The AFLP and SSR data accord with the ‘tabula rasa’ hypothesis in which a recent and rapid colonization of northern Europe took place from the western Mediterranean after the Last Glacial Maximum. The unbalanced west-east vs. west-north colonization may be as a result of ‘high density blocking’ effect.
58 citations
TL;DR: Phylogenetic relationships among species are widely congruent with previous plastid reconstructions, which refute the classical taxonomical classification.
55 citations
TL;DR: A scenario of rapid diversification in carnations in which autopolyploidsy and allopolyploidy, in interaction with geography and/or isolation, have played prominent roles is supported, and molecular data indicate that gene flow among different cytotypes is rare or nonexistent.
Abstract: Summary • The micro-evolutionary mechanisms that drive large-scale radiations are not completely understood, partly because of a shortage of population-level studies aimed at identifying putative causes of rapid evolutionary change. The Dianthus broteri complex, representing the largest polyploid series known to date for any species in the genus (2· ,4 · ,6 · and 12· cytotypes), belongs to a lineage that was recently found to have diversified at unusually rapid rates. • We used a combination of genome sequencing (internal transcribed spacer (ITS), plus chloroplast DNA (cpDNA) regions trnH-psbA, psbA-trnK and trnKmatK) and amplified fragment length polymorphism (AFLP) fingerprinting in 25 populations to infer the evolutionary history of extant polyploid races. • The haplotype, ribotype and AFLP reconstructions showed a star-shaped arrangement suggesting a pattern of radiative evolution. The major, widespread haplotype occurred at all ploidy levels, whereas 20 minor haplotypes were restricted to single populations and cytotypes. In addition, AFLP analyses retrieved well-supported cytogeographic groups: six clades were clearly differentiated in terms of ploidy level and geography. Molecular data indicate that gene flow among different cytotypes is rare or nonexistent. • Our study supports a scenario of rapid diversification in carnations in which autopolyploidy and allopolyploidy, in interaction with geography and ⁄ or isolation, have played prominent roles.
50 citations
TL;DR: The role of the three alternative mechanisms mentioned above in the origin and evolution of five bipolar Carex species are evaluated and parallel evolution seems to be the most plausible explanation to understand the particular case of the bipolar species C. microglochin s.l.
47 citations
TL;DR: Quantitative variation supports discrete variation and provides statistical support for the taxa recognized in some recent proposals of Hedera.
Abstract: Premise of the study : The use of continuous morphological characters in taxonomy is traditionally contingent on the existence of discrete diagnostic characters. When plant species are the result of recent divergence and gene fl ow and/or hybridization occur, the use of continuous morphological characters may help in species identifi cation and delimitation. Between nine and 15 species have been recognized in the last treatments of Hedera . The recent divergence of the species and the involvement of allopolyploidization as the main force in this process may have greatly impeded the establishment of clear limits and contributed to multiple taxonomic proposals. Methods : A multivariate statistical decision-making procedure was applied to 56 quantitative morphological characters and 602 specimens to identify and delimit Hedera species under the general lineage concept. Species ’ exclusive genetic ancestry was evaluated with the genealogical sorting index from the Bayesian inference trees of 30 Hedera ITS sequences. Key results : The decision-making procedure allowed recognizing 12 species and two groups (stellate and scale-like trichome groups) in Hedera and provided statistical support for making decisions about long-standing taxonomic controversies. Common ancestry was detected for the populations of three species even in the absence of the species monophyly. Conclusions : Quantitative variation supports discrete variation and provides statistical support for the taxa recognized in some recent proposals of Hedera . The need of explicit analysis of quantitative data are claimed to reduce taxonomic subjectivity and ease decision-making when qualitative data fail.
47 citations
TL;DR: Although the trnL–trnF phylogeny was not fully resolved, the sequence analysis showed a well-supported subgroup of I. filifolia, I. tingitana and I. xiphium, as well as I. boissieri, are very closely related species and share cytogenetic characteristics.
Abstract: The subgenus Xiphium is one of the six infrageneric divisions of the genus Iris. Chromosome numbers of six of the seven Xiphium species are known. Here the aim was to infer genetic and phylogenetic relationships based on chromosome numbers, chromosome markers and plastid sequences. Chromosomal locations of 5S and 45S rDNA loci were determined in 19 populations of the 7 species by fluorescence in situ hybridization (FISH). Additionally, the trnL–trnF plastid spacer was sequenced and a phylogenetic analysis performed. Based on chromosome markers, subgenus Xiphium species were classified into four groups that differed in the number and locations of both types of nrDNA: (1) I. tingitana (2n = 28), I. filifolia (2n = 30, 34) and I. xiphium (2n = 34), (2) I. juncea (2n = 32) and I. boissieri (2n = 36), (3) I. serotina (2n = 34) and (4) I. latifolia (2n = 42). Although the trnL–trnF phylogeny was not fully resolved, the sequence analysis showed a well-supported subgroup of I. filifolia, I. tingitana and I. xiphium, as well as I. juncea. FISH physical maps of the Iris subgenus Xiphium taxa are species dependent. I. filifolia, I. tingitana and I. xiphium are very closely related species and share cytogenetic characteristics. Disploidy appears to have been central in the evolution of this subgenus, given a series of chromosome numbers (2n = 28, 30, 32, 34, 36, 42) and our phylogenetic results. Clear differences were found among European and African populations of I. filifolia. A different taxonomic treatment of I. filifolia is supported for populations on both sides of the Strait of Gibraltar.
44 citations
TL;DR: The lineages of Olea illustrate how low phenotypic differentiation can be also related to a clear molecular differentiation in oceanic island enclaves, probably as a result of oceanic conditions in subtropical environments.
TL;DR: Specialization of the personate flower of Antirrhinum is interpreted for bees with both large bodies and high visitation indices, suggesting that these bee guilds are effective pollinators of the three self-incompatible Antirkhinum species.
Abstract: This paper provides the first results of pollinator fauna associated to the reproductive biology of Antirrhinum charidemi, Antirrhinum graniticum and Antirrhinum braun-blanquetii. Censuses of over 16 hours spanning the flowering phenology of each species were drawn up. As previously hypothesized, the characteristic occluded (personate) corolla of Antirrhinum was exclusively pollinated by bees, but by a higher number (four) of bee families than predicted. Seven bee species (Bombus hortorum, Anthidium manicatum, Chalicodoma lefebvrei, Anthidium sticticum, Anthophora dispar, Xylocopa violacea and Anthidium cingulatum) account for over 90% of flower visits (2098). The flower visitation index varied between species (0.0126−0.0320), reaching relatively medium values compared to Mediterranean plants. In contrast, reproductive success was found to be high when estimated as both fruit (45.4–84.2%) and seed (75.4–98.4%) sets, suggesting that these bee guilds are effective pollinators of the three self-incompatible ...
TL;DR: Analysis of Canarian populations suggests that a geographical rather than ecological differentiation was primarily responsible for early stages of a non-adaptive radiation of the Canarian lineage, and differentiation patterns of mainland populations appear to be more complex.
Abstract: Diversification rates of insular oceanic lineages have been historically considered to be higher than those of mainland counterparts. In order to test this hypothesis in a group of Canarian endemics (Cistus), we estimated phylogeny and conducted both network analyses of haplotypes and molecular clock estimates using plastid DNA sequences of the trnStrnG and the trnKmatK. Net differentiation rates in the Canarian purple-flowered lineage parallel those of the mainland (Mediterranean) purple-flowered sister group, as revealed by a similar number of species (five vs. three), haplotypes (seven vs. eight) and haplotype clades (four vs. four). Splitting dates in the Canarian (0.337 0.14/0.287 0.16 Ma) and Mediterranean (0.667 0.18/0.387 0.19 Ma) lineages reveal concordance in tempo of diversification. All these results are interpreted as evidence of two synchronous evolutionary histories given that Cistus ancestors had to cope with factors promoting differentiation in two hotspots of plant diversity: the Macaronesian and Mediterranean floristic regions. Analysis of Canarian populations suggests that a geographical rather than ecological differentiation was primarily responsible for early stages of a non- adaptive radiation of the Canarian lineage. Differentiation patterns of mainland populations appear to be more complex. & 2009 R ¨ ubel Foundation, ETH Z ¨
TL;DR: It is argued that ecogeographical factors, in addition to some phylogeographical and phylogenetic signals, are involved in the multiplication of carpels during the development of the ovary wall in C. ladanifer populations.
Abstract: Variation is the raw material for evolution. Differences among populations in the expression of traits related to plant fitness may result from natural selection, phenotypic plasticity (in response to local conditions), and developmental instability (manifested as high intra-individual variation in repeated patterns or characters). Cistus ladanifer is a highly polymorphic plant distributed in the Mediterranean and the only species in the family (Cistaceae, 180 species) with a variable number of valves per fruit. We herein analysed the variation in the number of valves (5–12) and seeds (318–1185) per fruit in 36 populations (607 individuals, 1821 fruits) at different levels: temporal, geographical, ecogeographical, taxonomic, and phylogeographical. In addition, we tested whether an increased number of fruit valves influences predispersal seed predation. Large variation in the number of valves and seeds per fruit among populations, individuals, and years was reported. The number of ovules and seeds per valve increased with a higher number of fruit valves. Geographical and taxonomic variables did not significantly explained this fruit variation. On the contrary, we found a negative relationship between the number of fruit valves and altitude and a positive relationship with precipitation. We argue that ecogeographical factors, in addition to some phylogeographical and phylogenetic signals, are involved in the multiplication of carpels during the development of the ovary wall. This, coupled with the results of the evolutionary history of Cistus in previous studies, indicates active evolutionary processes in C. ladanifer populations.
TL;DR: The evaluation of species monophyly alongside the contribution of other life history traits in the historical interpretation of the level and partitioning of genetic diversity, and its use in recommendations for species conservation programs is drawn.
Abstract: Molecular markers are routinely used to assess levels of diversity within and among populations, particularly with regard to species of conservation concern. However, when interpreting the level and partitioning of diversity observed, an implicit assumption is often made that the populations of the species in question form a monophyletic group. We tested this assumption in three endemics of Antirrhinum (A. charidemi, A. subbaeticum, and A. valentinum) using 79 nuclear [internal transcribed spacer (ITS)] and 85 plastid (psbA-trnH, trnT-trnL, trnK-matK, trnS-trnG) sequences representing multiple accessions of each of 24 Antirrhinum species (single accession of A. cirrhigerum). These species share six life history traits implicated in levels of genetic diversity, and have been the subject of previous population genetic studies. Populations of all three species formed monophyletic groups on ITS analysis. In contrast, none of the three species formed monophyletic groups on plastid sequence analysis: populations of A. charidemi fall in a monophyletic group including one accession of A. mollissimum, populations of A. subbaeticum form a polyphyletic group with plastid sequences shared with A. pulverulentum, and populations of A. valentinum are unresolved within a clade containing six other species. Lack of monophyly using plastid sequences is interpreted as a combination of shared ancestral polymorphism and hybridization in a reticulate evolutionary history of these species. Monophyly in the ITS tree may reflect a more recent sequence homogenization. We draw attention to the evaluation of species monophyly alongside the contribution of other life history traits in the historical interpretation of the level and partitioning of genetic diversity, and its use in recommendations for species conservation programs.