Saša Stefanović

University of Toronto, Toronto, Ontario, Canada

Are you Saša Stefanović?

Claim your profile

Publications (24)53.2 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens are needed in order for DNA barcodes to serve their intended purpose, where this is possible, and to understand the reasons behind their failure to do so, when this occurs. We evaluated four loci, widely regarded as universal DNA barcodes for plants, for their utility in hawthorn species identification. Three plastid regions, matK, rbcLa, and psbA-trnH and the internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA discriminate only some of the species of Crataegus that can be recognized on the basis of their morphology. In part, this is because in Rosaceae tribe Maleae most individual plastid loci yield relatively little taxonomic resolution, and in part because the effects of allopolyploidization have not been eliminated by concerted evolution of the ITS regions. Although individual plastid markers provided generally poor resolution of taxonomic groups in Crataegus, a few species were notable exceptions. In contrast, analyses of concatenated sequences of the three plastid barcode loci plus 11 additional plastid loci gave a well-resolved maternal phylogeny. In the ITS2 tree, different individuals of some species formed groups with taxonomically unrelated species. This is a sign of lineage sorting due to incomplete concerted evolution in ITS2. Incongruence between the ITS2 and plastid trees is best explained by hybridization between different lineages within the genus. In aggregate, limited between-species variation in plastid loci, hybridization, and a lack of concerted evolution in ITS2 all combine to limit the utility of standard barcoding markers in Crataegus. These results have implications for authentication of hawthorn materials in Natural Health Products. Published by Oxford University Press on behalf of the Annals of Botany Company.
    AoB PLANTS 04/2015; DOI:10.1093/aobpla/plv045 · 1.74 Impact Factor
  • Mihai Costea, Miguel A. García, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract— Cuscuta (dodders, Convolvulaceae) is one of the largest and most economically important lineages of parasitic plants. The genus has a sub-cosmopolitan distribution with more than 75% of the species diversifying in the New World. The last monograph, published by Truman George Yuncker in 1932, provided a solid species-level taxonomic foundation. However, as revealed by recent phylogenetic studies, its infrageneric classification has been in great need of a taxonomic reappraisal, mainly because the morphological characters used in the previous classifications have been greatly affected by convergent evolution. Several recent phylogenetic and character evolution studies with broad sampling, as well as species-level revisions, have illustrated the deficiencies of previous classifications and provided an explicit and robust phylogenetic framework. Here we propose a new phylogenetic classification that places all 194 currently accepted species of Cuscuta into four subgenera and 18 sections. Sections have a strong morphological and biogeographical predictive value and include from one to 31 species. Thirteen section names are new or applied for the first time at the sectional rank: Babylonicae (Yunck.) M. A. García, Subulatae (Engelm.) Costea & Stefanović, Obtusilobae (Engelm.) Costea & Stefanović, Prismaticae (Yunck.) Costea & Stefanović, Ceratophorae (Yunck.) Costea & Stefanović, Umbellatae (Yunck.) Costea & Stefanović, Gracillimae Costea & Stefanović, Californicae (Yunck.) Costea & Stefanović, Indecorae (Yunck.) Costea & Stefanović, Oxycarpae (Engelm. ex Yunck.) Costea & Stefanović, Racemosae (Yunck.) Costea & Stefanović, Partitae Costea & Stefanović, and Denticulatae (Yunck.) Costea & Stefanović. An identification key to sections is included together with an overview of morphology, geographical distribution, taxonomic notes, and lists of included species.
    Systematic Botany 02/2015; 40(1). DOI:10.1600/036364415X686567 · 1.11 Impact Factor
  • M Zarrei, S Stefanović, T A Dickinson
    [Show abstract] [Hide abstract]
    ABSTRACT: The taxonomic complexity of Crataegus (hawthorn; Rosaceae, Maleae), especially in North America, has been attributed by some to hybridization in combination with gametophytic apomixis and polyploidization, whereas others have considered the roles of hybridization and apomixis to be minimal. Study of the chemical composition and therapeutic value of hawthorn extracts requires reproducible differentiation of entities that may be difficult to distinguish by morphology alone. This study sought to address this by using the nuclear ribosomal spacer region ITS2 as a supplementary DNA barcode; however, a lack of success prompted an investigation to discover why this locus gave unsatisfactory results.
    Annals of Botany 07/2014; 114(2). DOI:10.1093/aob/mcu116 · 3.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: AimAsexual organisms frequently have larger ranges than their sexual progenitors, a phenomenon referred to as geographical parthenogenesis (GP). In plants, GP is associated not only with asexuality (apomixis), but also with polyploidization and hybridity (allopolyploidy). Dispersal is thought to play a role in range-size differences in other taxa, but has not been directly related to GP. Here, we compare resource allocation to dispersal-related traits in sexual diploids, asexual autopolyploids and asexual allopolyploids, and relate these differences to patterns of GP.LocationThe Pacific Northwest, North America.Methods We created distribution maps for all cytotypes known in Crataegus series Douglasianae using herbarium records. To quantify dispersal ability, we collected fruit samples from sexual diploids, apomictic allopolyploids and apomictic autopolyploids across their ranges, and used the masses of each fruit component as a proportion of the total fruit mass to gauge relative investment in dispersal and competitive ability.ResultsThe largest ranges belong to apomictic allopolyploids, whereas apomictic autotriploids and sexual diploids have the smallest ranges. Compared to sexual diploids and apomictic autotriploids, the allotetraploids exhibit a more dispersal-orientated strategy, with proportionally heavier pyrenes and more fruit pulp, but proportionally lighter seeds. Allotriploid taxa, which arose via back-crosses between sexual diploids and asexual allotetraploids, exhibit an intermediate range size as well as intermediate investment in dispersal.Main conclusionsIn Crataegus series Douglasianae, GP is associated only with allopolyploids, highlighting the potential role of hybridization in range expansion. The data suggest that allopolyploids are associated with increased resource allocation to dispersal-related traits, whereas sexual diploid C. suksdorfii and asexual autotriploid C. gaylussacia exhibit a more competition-orientated strategy. These findings are consistent with the hypothesis that hybridization contributes to patterns of GP in asexual allopolyploids, potentially by increasing their dispersal ability.
    Journal of Biogeography 04/2014; 41(8). DOI:10.1111/jbi.12316 · 4.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The parasitic genus Cuscuta, containing some 200 species circumscribed traditionally in three subgenera, is nearly cosmopolitan, occurring in a wide range of habitats and hosts. Previous molecular studies, on subgenera Grammica and Cuscuta, delimited major clades within these groups. However, the sequences used were unalignable among subgenera, preventing the phylogenetic comparison across the genus. We conducted a broad phylogenetic study using rbcL and nrLSU sequences covering the morphological, physiological, and geographical diversity of Cuscuta. We used parsimony methods to reconstruct ancestral states for taxonomically important characters. Biogeographical inferences were obtained using statistical and Bayesian approaches. Four well-supported major clades are resolved. Two of them correspond to subgenera Monogynella and Grammica. Subgenus Cuscuta is paraphyletic, with section Pachystigma sister to subgenus Grammica. Previously described cases of strongly supported discordance between plastid and nuclear phylogenies, interpreted as reticulation events, are confirmed here and three new cases are detected. Dehiscent fruits and globose stigmas are inferred as ancestral character states, whereas the ancestral style number is ambiguous. Biogeographical reconstructions suggest an Old World origin for the genus and subsequent spread to the Americas as a consequence of one long-distance dispersal. Hybridization may play an important yet underestimated role in the evolution of Cuscuta. Our results disagree with scenarios of evolution (polarity) previously proposed for several taxonomically important morphological characters, and with their usage and significance. While several cases of long-distance dispersal are inferred, vicariance or dispersal to adjacent areas emerges as the dominant biogeographical pattern.
    American Journal of Botany 03/2014; 101(4). DOI:10.3732/ajb.1300449 · 2.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract— Members of the small genus Conopholis are perennial holoparasites. They are found growing in eastern and southwestern North America and in Central America, where they attach to the roots of their oak hosts. Two species were recognized in the last taxonomic revision of the group based on geographic range and differences in floral, capsule, and bract morphology. Due to the overlapping nature of the characters used to distinguish between taxa, no single morphological feature can be relied on to differentiate between the species. A recent molecular phylogenetic study of the genus recovered three well-supported lineages, none of which corresponds entirely to the current subdivision of the genus into two species. We undertook a fine-scale morphometric study of the genus, emphasizing calyx and bract morphology. Unweighted pair-group method using arithmetic averages and principal coordinate analyses corroborate molecular data and strongly support the distinction of three separate lineages within Conopholis. A taxonomic re-alignment is proposed for the genus including three species, C. americana, C. panamensis, and C. alpina, each with various degrees of overlap with previously described taxa.
    Systematic Botany 09/2013; 38(3):795-804. DOI:10.1600/036364413X670403 · 1.11 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The Campanula pyramidalis complex is a group of closely related taxa with a distribution across the Balkans, from the Gulf of Trieste in the north to the Peloponnese Peninsula in the south, with small disjunct parts of the range in the south Apennines. Although 21 taxa were described within this complex, only three, C. pyramidalis, C. versicolor, and C. secundiflora, have been generally accepted in recent synoptical taxonomic treatments. Our molecular phylogenetic analyses based on sequences of three non-coding chloroplast regions (psbA-trnH, psbZ-trnfM, trnG-trnS) as well as of nuclear ribosomal internal transcribed spacers (nrITS), lend strong support to the recognition of several lineages which only partially correspond to generally accepted taxonomic concepts. Molecular data presented in this study showed that C. pyramidalis is a polyphyletic assemblage that segregates into three distinct lineages, one of which is described here as a new species, C. austroadriatica sp. nov. The lectotype of C. pyramidalis, redefined in a strict sense, is designated. Neither C. versicolor nor C. secundiflora were found to be strictly monophyletic, but their monophyly could not be rejected. Morphological and biogeographical implications are discussed.
    Taxon 06/2013; 62(3):505-524. DOI:10.12705/623.1 · 3.05 Impact Factor
  • E.Y.Y. Lo, S. Stefanović, T.A. Dickinson
    [Show abstract] [Hide abstract]
    ABSTRACT: We have demonstrated geographical parthenogenesis in Crataegus series Douglasianae, an agamic complex comprising exclusively tetraploid Crataegus douglasii sensu lato and the morphologically distinct Crataegus suksdorfii complex that comprises diploids and polyploids. Here we characterize ploidy level and breeding system by detailed flow cytometric measurements of the 2C nuclear DNA content of leaf, embryo, and endosperm tissues from 282 black-fruited hawthorns (Crataegus series Douglasianae) representing 33 localities in the Pacific Northwest, one in the Cypress Hills, and three more in the upper Great Lakes basin. We use existing climate and molecular data to place our flow cytometry results in an environmental and evolutionary context. Crataegus douglasii occupies more widely distributed sites that experience more extreme temperature and moisture regimes than do the sites occupied by diploid C. suksdorfii.
    Botany 12/2012; 91(2):107-116. DOI:10.1139/cjb-2012-0073 · 1.04 Impact Factor
  • Source
    Thomas Braukmann, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: Unlike parasitic plants, which are linked to their hosts directly through haustoria, mycoheterotrophic (MHT) plants derive all or part of their water and nutrients from autothrophs via fungal mycorrhizal intermediaries. Ericaceae, the heather family, are a large and diverse group of plants known to form elaborate symbiotic relationships with mycorrhizal fungi. Using PHYA sequence data, we first investigated relationships among mycoheterotrophic Ericaceae and their close autotrophic relatives. Phylogenetic results suggest a minimum of two independent origins of MHT within this family. Additionally, a comparative investigation of plastid genomes (plastomes) grounded within this phylogenetic framework was conducted using a slot-blot Southern hybridization approach. This survey encompassed numerous lineages of Ericaceae with different life histories and trophic levels, including multiple representatives from mixotrophic Pyroleae and fully heterotrophic Monotropeae and Pterosporeae. Fifty-four probes derived from all categories of protein coding genes typically found within the plastomes of flowering plants were used. Our results indicate that the holo-mycoheterotrophic Ericaceae exhibit extensive loss of genes relating to photosynthetic function and expression of the plastome but retain genes with possible functions outside photosynthesis. Mixotrophic taxa tend to retain most genes relating to photosynthetic functions but are varied regarding the plastid ndh gene content. This investigation extends previous inferences that the loss of the NDH complex occurs prior to becoming holo-heterotrophic and it shows that the pattern of gene losses among mycoheterotrophic Ericaceae is similar to that of haustorial parasites. Additionally, we identify the most desirable candidate species for entire plastome sequencing.
    Plant Molecular Biology 03/2012; 79(1-2):5-20. DOI:10.1007/s11103-012-9884-3 · 4.07 Impact Factor
  • Mihai Costea, Ignacio García Ruiz, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: The Cuscuta chapalana complex (Convolvulaceae) is a recently circumscribed clade within the subgenus Grammica that includes several little-known species from Mexico and Central and northern South America characterized by the presence of peculiar subapical multicelullar appendages on the corolla and often on the calyx lobes. Basic morphology, scanning electron microscopy, and DNA sequence data from the plastid trnL–F region and the 26S rDNA and internal transcribed spacer nuclear regions were used to investigate the phylogenetic relationships within the group and to test the species limits. Multicellular appendages are horn-like or tubular in shape and bear one or more stomata at their tips; hence the vernacular name “horned” dodders. Eight lineages were reconstructed; two of them, both from Mexico, were described as new species: Cuscuta bonafortunae Costea & I. García, sp. nov., and Cuscuta carnosa Costea & Stefanović, sp. nov. Cuscuta pringlei is redefined as a variety of Cuscuta strobilacea. A taxonomic treatment with an identification key, descriptions, and illustrations is provided.
    Botany 11/2011; 89(10):715-730. DOI:10.1139/b11-049 · 1.04 Impact Factor
  • Mihai Costea, Ian Spence, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: Cuscuta chinensis species complex is a small clade from subgenus Grammica (Cuscuta, Convolvulaceae). Many species of this clade exhibit crest- or dome-like multicellular appendages with stomata on the midvein/carena of calyx lobes. Basic morphology, scanning electron microscopy, and DNA sequence data from the plastid trnL-F region and the nuclear internal transcribed spacer (ITS) were used to investigate the phylogenetic relationships within the group and test the species limits. Based on their morphological and molecular similarly, C. chinensis and C. applanata represent one single species, and the latter was retained as a variety of the former. While the clade is centered in the southern USA and Mexico, C. chinensis var. chinensis has a disjunct distribution in Australia and Asia, which is likely the result of relatively recent long-distance dispersal. Cuscuta alata from Mexico, previously considered synonymous to C. applanata, was found to be a distinct species based on both molecular and morphological evidence. Cuscuta potosina var. potosina and var. globifera segregate into two different subclades of the C. chinensis species complex. Because these two taxa are also different morphologically, var. globifera is described as a new species, C. azteca. Cuscuta campestris, an almost cosmopolitan weed species from another clade (“Clade B”; “C. pentagona complex”), is commonly misidentified in Asia as C. chinensis, which raises questions about the identity of the Cuscuta plants used in widely commercialized medicinal herbal mixtures. A taxonomic treatment with an identification key, descriptions, and illustrations is provided.
    Organisms Diversity & Evolution 11/2011; 11(5). DOI:10.1007/s13127-011-0061-3 · 3.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Horizontal gene transfer (HGT) is relatively common in plant mitochondrial genomes but the mechanisms, extent and consequences of transfer remain largely unknown. Previous results indicate that parasitic plants are often involved as either transfer donors or recipients, suggesting that direct contact between parasite and host facilitates genetic transfer among plants. In order to uncover the mechanistic details of plant-to-plant HGT, the extent and evolutionary fate of transfer was investigated between two groups: the parasitic genus Cuscuta and a small clade of Plantago species. A broad polymerase chain reaction (PCR) survey of mitochondrial genes revealed that at least three genes (atp1, atp6 and matR) were recently transferred from Cuscuta to Plantago. Quantitative PCR assays show that these three genes have a mitochondrial location in the one species line of Plantago examined. Patterns of sequence evolution suggest that these foreign genes degraded into pseudogenes shortly after transfer and reverse transcription (RT)-PCR analyses demonstrate that none are detectably transcribed. Three cases of gene conversion were detected between native and foreign copies of the atp1 gene. The identical phylogenetic distribution of the three foreign genes within Plantago and the retention of cytidines at ancestral positions of RNA editing indicate that these genes were probably acquired via a single, DNA-mediated transfer event. However, samplings of multiple individuals from two of the three species in the recipient Plantago clade revealed complex and perplexing phylogenetic discrepancies and patterns of sequence divergence for all three of the foreign genes. This study reports the best evidence to date that multiple mitochondrial genes can be transferred via a single HGT event and that transfer occurred via a strictly DNA-level intermediate. The discovery of gene conversion between co-resident foreign and native mitochondrial copies suggests that transferred genes may be evolutionarily important in generating mitochondrial genetic diversity. Finally, the complex relationships within each lineage of transferred genes imply a surprisingly complicated history of these genes in Plantago subsequent to their acquisition via HGT and this history probably involves some combination of additional transfers (including intracellular transfer), gene duplication, differential loss and mutation-rate variation. Unravelling this history will probably require sequencing multiple mitochondrial and nuclear genomes from Plantago. See Commentary:
    BMC Biology 12/2010; 8:150. DOI:10.1186/1741-7007-8-150 · 7.43 Impact Factor
  • Source
    Eugenia Y Y Lo, Saša Stefanović, Timothy A Dickinson
    [Show abstract] [Hide abstract]
    ABSTRACT: Polyploidy plays a prominent role in the speciation process in plants. Many species are known to be part of agamic complexes comprising sexual diploids and more or less exclusively asexual polyploids. However, polyploid formation has been studied in very few cases, primarily because of the challenges in examining these cases phylogenetically. In this study, we demonstrate the use of a variety of phylogenetic approaches to unravel origins and infer reticulation history in a diploid-polyploid complex of black-fruited Crataegus. The tree approaches are shown to be useful in testing alternative hypotheses and in revealing genealogies of nuclear genes, particularly in polyploid organisms that may contain multiple copies. Compared to trees, network approaches provide a better indication of reticulate relationships among recently diverged taxa. Taken together, our data point to both the autopolyploid and allopolyploid origins of triploids in natural populations of Crataegus suksdorfii, whereas tetraploids are formed via a triploid bridge, involving the backcross of allotriploid offspring with their diploid C. suksdorfii parent, followed by gene introgression from sympatric C. douglasii. Our findings provide empirical evidence for different pathways of polyploid formation that are all likely to occur within natural populations and the allopatric establishment of neopolyploids subsequent to their formation.
    Evolution 12/2010; 64(12):3593-608. DOI:10.1111/j.1558-5646.2010.01063.x · 4.66 Impact Factor
  • Mihai Costea, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: The Cuscuta umbellata complex is one of the 15 major clades recently circumscribed in C. subg.Grammica. Most of its members occur in North America and the Caribbean (C. desmouliniana, C. lacerata, C. leptantha, C. liliputana, C. odontolepis, C. polyanthemos, C. tuberculata, C. umbellata), but three species (C. acuta, C. membranacea, C. umbellata) grow in South America, and one (C. hyalina) is found as a native species in India, Pakistan and Eastern to South Africa. Basic morphology, scanning electron microscopy and sequence data from the nuclear internal transcribed spacer (ITS) and the plastid trnL-F region were used to reconstruct the phylogeny, gain a better understanding of the evolutionary history, and determine species boundaries. Our results show that in its currently accepted delimitation C. umbellata is polyphyletic. Discordances between phylogenies derived from plastid and nuclear data strongly suggest that at least four independent hybridization events have occurred in the evolution of this species group, rendering relationships among its members more complex than previously thought. One of these reticulation events involves C. umbellata var. reflexa, a taxon that has been considered synonymous to C. umbellata var. umbellata in the last decades. This hybrid is morphologically intermediate but distinct from its putative parents, C. odontolepis or C. acuta on the maternal side, and C. umbellata (var. umbellata) on the paternal side, which supports its treatment as a new species, C. legitima. Cuscuta umbellata is further redefined to exclude C. umbellata var. dubia, which is merged into C. desmouliniana. A new classification is provided, together with an identification key, descriptions, illustrations, and geographical distributions for the twelve species of the clade.
    Taxon 11/2010; 59(6):1783-1800. DOI:10.2307/41059873 · 3.05 Impact Factor
  • Source
    Mark Welsh, Saša Stefanović, Mihai Costea
    [Show abstract] [Hide abstract]
    ABSTRACT: The pollen morphology of 148 taxa (135 species and 13 varieties) of the parasitic plant genus Cuscuta (dodders, Convolvulaceae) was examined using scanning electron microscopy. Six quantitative characters were coded using the gap-weighting method and optimized onto a consensus tree constructed from three large-scale molecular phylogenies of the genus based on nuclear internal transcribed spacer (ITS) and plastid trn-LF sequences. The results indicate that 3-zonocolpate pollen is ancestral, while grains with more colpi (up to eight) have evolved only in two major lineages of Cuscuta (subg. Monogynella and cladeO of subg. Grammica). Complex morphological intergradations occur between species when their tectum is described using the traditional qualitative types—imperforate, perforate, and microreticulate. This continuous variation is better expressed quantitatively as “percent perforation,” namely the proportion of perforated area (puncta or lumina) from the total tectum surface. Tectum imperforatum is likely the ancestral condition, while pollen grains with increasingly larger perforation areas have evolved multiple times. The reticulated tectum, unknown in other Convolvulaceae, has evolved in Cuscuta only in two lineages (subg. Monogynella, and cladeO of subg. Grammica). Overall, the morphology of pollen supports Cuscuta as a sister to either the “bifid-style” Convolvulaceae clade (Dicranostyloideae) or to one of the members of this clade. Pollen characters alone are insufficient to reconstruct phylogenetic relationships; however, palynological information is useful for the species-level taxonomy of Cuscuta. KeywordsConvolvulaceae- Cuscuta -Dodders-Evolution-Phylogeny-Pollen morphology-Scanning electron microscopy-Taxonomy
    Plant Systematics and Evolution 03/2010; 285(1):83-101. DOI:10.1007/s00606-009-0259-4 · 1.15 Impact Factor
  • Mihai Costea, Michael A.R. Wright, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: The salt marsh dodders, Cuscuta salina, have been historically delimited as a morphologically variable assemblage of inbreeding forms that parasitize hosts growing in alkaline or saline habitats from western North America. This morphological diversity has been traditionally classified into three varieties: salina, major, and papillata. A morphometric analysis of floral characters and a molecular study using both plastid and nuclear DNA sequences strongly support the segregation of a new species, Cuscuta pacifica Costea and M. A. R. Wright, from C. salina. The new species corresponds to a lineage that includes varieties major and papillata, whereas C. salina is limited essentially to its type variety. Cuscuta pacifica and C. salina are sister species that have only a small area of parapatry in lower California, where they are ecologically and reproductively separated. Cuscuta salina occurs mostly in inland vernal pools and salt flats of Arizona, California, Nevada, Utah, Baja California, and Sonora, and grows primarily on Frankenia andb Suaeda. Cuscuta pacifica can be found in salt marshes from the south-central Pacific coast of California north into British Columbia, parasitic especially on Salicornia and Jaumea carnosa. Cuscuta salina var. papillata (Yunck.) Costea and M. A. R. Wright, parasitic on hosts that grow in coastal interdunes, falls within the range of variation of C. pacifica, where it is transferred.
    Systematic Botany 09/2009; 34(4):787-795. DOI:10.1600/036364409790139583 · 1.11 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The genus Edraianthus A.DC. has a center of distribution in the Balkans and it is one of the most prominent groups of endemic plants in this region. During our recent fieldtrip to Mt. Lovćen (Montenegro), putative hybrid individuals were encountered, morphologically intermediate between two sympatric taxa, E. tenuifolius (E. sect. Edraianthus) and E. wettsteinii subsp. lovcenicus (E. sect. Uniflori). Multivariate morphometric and molecular analyses were carried out to investigate the occurrence of hybridization between these two species. As a result, a new nothospecies is described here, Edraianthus×lakusicii V. Stevanović & D. Lakušić, a natural hybrid between E. tenuifolius and E. wettsteinii subsp. lovcenicus. At present, this hybrid is known only from the single locality of Mt. Lovćen. Its population size is estimated to be <50 mature individuals and the estimated “area of occupancy” is smaller than 1km2.
    Plant Systematics and Evolution 09/2009; 280(1):77-88. DOI:10.1007/s00606-009-0168-6 · 1.15 Impact Factor
  • Source
    Mihai Costea, Saša Stefanović
    [Show abstract] [Hide abstract]
    ABSTRACT: Multiple DNA sequences from plastid (trnL-F region and rbcL) as well as nuclear (ITS and 26S rDNA) genomes were used to infer the phylogeny of the Cuscuta californica complex. This group is currently circumscribed to include nine species distributed mostly in western North America. Four well-supported lineages have been revealed within this complex. The first lineage includes the controversial C. californica s. l., an assemblage of taxa characterized by their lack of infrastaminal scales; the second lineage consists of a single species, C. subinclusa, with short fimbriate scales. The third lineage groups C. howelliana, C. salina, and C. suksdorfii, with scales that exhibit a reduction trend, while the forth includes C. decipiens and a new species from New Mexico and trans-Pecos Texas, C. draconella, both with well-developed infrastaminal scales. Stereo, compound, and scanning electron microscopy were used to investigate the new species and compare it with C. decipiens, its closest relative, as well as to update the taxonomic treatment of C. californica s. l. Cuscuta decipiens, in its original delimitation, is polyphyletic and was thus recircumscribed. In contrast to previous taxonomic treatments of C. californica s. l., phylogenetic relationships in conjunction with morphological data support the delimitation of three species: C. brachycalyx, C. californica, and C. occidentalis.
    Systematic Botany 06/2009; 34(3):570-579. DOI:10.1600/036364409789271317 · 1.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Because recent molecular studies, based on multiple data sets from all three plant genomes, have indicated mutually congruent, well-resolved, and well-supported relationships within Convolvulaceae (the morning-glory family), a formal reclassification of this family is presented here. Convolvulaceae, a large family of worldwide distribution, exhibiting a rich diversity of morphological characteristics and ecological habitats, are now circumscribed within twelve tribes. A key to these tribes of Convolvulaceae is offered. The group of spiny-pollen bearing Convolvulaceae (forming “Echinoconiae”) and tribe Cuscuteae are retained essentially in their traditional sense, Cresseae are circumscribed with only minor modifications, Convolvuleae and Erycibeae are recognized in a restricted sense, while Dichondreae and Maripeae are expanded. Also, to produce a tribal taxonomy that better reflects phylogenetic relationships, the concept of Poraneae is abandoned as artificial, three new tribes are recognized (Aniseieae, Cardiochlamyeae, and Jacquemontieae), and a new tribal status is proposed for the Malagasy endemic Humbertia (Humbertieae). “Merremieae” are tentatively retained even though the monophyly of this tribe is not certain. In addition to the formal classification, we provide clade name definitions for the family as well as for most of the clades recognized presently as tribes. Also, five well-supported clades that are not assigned formal ranks are recognized and their names defined. The reevaluation of traditional taxonomic characters reveals that many homoplasious characters were emphasized in previous classifications, resulting in formal recognition of non-monophyletic groups. Putative morphological synapomorphies for many clades discovered through molecular cladistic analyses are discussed. However, the morphology of several clades that are well-supported by DNA evidence remains poorly understood, creating further challenges for future studies in Convolvulaceae.
    Systematic Botany 01/2009; DOI:10.1043/02-45.1 · 1.11 Impact Factor
  • Source
    Saša Stefanović, Dmitar Lakušić
    [Show abstract] [Hide abstract]
    ABSTRACT: AbstrACt The phylogentic position of the Campanula trichocalycina-pichleri complex, a group consisting of two species distributed respectively in the Apeninenes and the Balkans, represents a long-standing taxonomic problem resulting from a conflict among limited number of morphological characters. Traditionally, this complex was treated either as a separate genus, Podanthum, or as part of Campanula or Asyneuma. However, these competing taxonomic hypotheses have never been tested using explicite phylogenetic approaches. We present here the results of molecular phylogenetic analyses based on non-coding chloroplast sequences (trnL-F). Molecular evidence indicates that Campanula trichocalycina and C. pichleri form a strongly supported lineage, positioned as sister-group to Asyneuma s.str. Consequently, we treate this complex as congeneric with Asyneuma. We also discuss relative importance of floral morphology versus fruit dehiscence for circumscription of Asyneuma and Campanula as well as proposed taxonomic status of Asyneuma comosiforme, a species recently discovered not to be closely related to other members of Asyneuma and segregated from this genus.

Publication Stats

240 Citations
53.20 Total Impact Points


  • 2008–2015
    • University of Toronto
      • • Department of Ecology and Evolutionary Biology
      • • Department of Biology at Mississauga
      Toronto, Ontario, Canada
  • 2010
    • Indiana University Bloomington
      • Department of Biology
      Bloomington, Indiana, United States
  • 2009
    • University of Washington Seattle
      Seattle, Washington, United States