Phylogenetic implications of endosperm cell wall morphology in Douglasia, Androsace, and Vitaliana (Primulaceae)

We investigated differences in endosperm cell wall thickening in three genera of Primulaceae; seven species of Douglasia , 28 species of Androsace representing the four sections of the genus, and the single species of the genus Vitaliana . Endosperm cell walls have irregular wall thickenings and narrow constrictions and characterize all Douglasia species and Vitaliana , whereas evenly thickened cell walls without constrictions were found in the endosperm of Androsace and Primulu . The endosperm character supports the monophyly of Douglasia and Vitaliana , and we discuss the phylogenetic implications of this conclusion.     

Phylogenetic implications of endosperm cell wall morphology in Douglasia, Androsace, and Vitaliana (Primulaceae)

We investigated differences in endosperm cell wall thickening in three genera of Primulaceae; seven species of Douglasia , 28 species of Androsace representing the four sections of the genus, and the single species of the genus Vitaliana . Endosperm cell walls have irregular wall thickenings and narrow constrictions and characterize all Douglasia species and Vitaliana , whereas evenly thickened cell walls without constrictions were found in the endosperm of Androsace and Primula . The endosperm character supports the monophyly of Douglasia and Vitaliana , and we discuss the phylogenetic implications of this conclusion.     

Radiation of southern African daisies: biogeographic inferences for subtribe Arctotidinae (Asteraceae, Arctotideae)

The majority of the approximately 80-90 species in subtribe Arctotidinae occur in southern Africa with the centre of diversity in the winter-rainfall region. Three species are restricted to afromontane eastern Africa and three species are endemic to Australia. To investigate biogeographic and phylogenetic relationships within Arctotidinae, sequence data from four cpDNA regions (psbA-trnH, trnT-trnL and trnL-trnF spacers and trnL intron) and the ITS nrDNA region for 59 Arctotidinae species were analyzed with parsimony and Bayesian-inference approaches. Eight well-supported major lineages were resolved. The earliest-diverging extant lineages are afromontane or inhabit mesic habitats, whereas almost all sampled taxa from the winter-rainfall and semi-arid areas have diverged more recently. Molecular dating estimated that the major clades diverged during the Miocene and Pliocene, which is coincident with the trend of increasing rainfall seasonality, aridification and vegetation changes in southwestern Africa. Trans-oceanic dispersal to Australia was estimated to have occurred during the Pliocene.     

Chloroplast DNA phylogeny and biogeography of Lepidium (Brassicaceae)

Two intergenic spacers, trnT-trnL and trnL-trnF, and the trnL intron of cpDNA were sequenced to study phylogenetic relationships and biogeography of 73 Lepidium taxa. Insertions/deletions of ≥3 bp (base pairs) provided reliable phylogenetic information whereas indels ≤2 bp, probably originating from slipped-strand mispairing, are prone to parallelism in the context of our phylogenetic framework. For the first time, an hypothesis of the genus Lepidium is proposed based on molecular phylogeny, in contrast to previous classification schemes into sections and greges (the latter category represents groups of related species within a given geographic region), which are based mainly on fruit characters. Only a few of the taxa as delimited in the traditional systems represent monophyletic lineages. The proposed phylogeny would suggest three main lineages, corresponding to (1) sections Lepia and Cardaria, (2) grex Monoplocoidea from Australia, and (3) remaining taxa, representing the bulk of Lepidium species with more or less resolved sublineages that sometimes represent geographical correspondence. The fossil data, easily dispersible mucilaginous seeds, widespread autogamous breeding systems, and low levels of sequence divergence between species from different continents or islands suggest a rapid radiation of Lepidium by long-distance dispersal in the Pliocene/Pleistocene. As a consequence of climatic changes in this geological epoch, arid/semiarid areas were established, providing favorable conditions for the radiation of Lepidium by which the genus attained its worldwide distribution.     

Relative roles of Neogene vicariance and Quaternary climate change on the historical diversification of bunchgrass lizards (Sceloporus scalaris group) in Mexico

Neogene vicariance during the Miocene and Pliocene and Quaternary climate change have synergistically driven diversification in Mexican highland taxa. We investigated the impacts of these processes on genetic diversification in the widely distributed bunchgrass lizards in the Sceloporus scalaris group. We searched for correlations between timing in diversification and timing of (1) a period of marked volcanism across the Trans-Mexican Volcanic Belt in central Mexico 3-7.5 million years ago (Ma) and (2) a transition to larger glacial-interglacial cycles during the mid-Pleistocene. From our phylogenetic analyses of mitochondrial DNA we identified two major clades that contained 13 strongly supported lineages. One clade contained lineages from the two northern sierras of Mexico, and the other clade included lineages associated with the Trans-Mexican Volcanic Belt and Central Mexican Plateau. Results provided support for Neogene divergences within the S. scalaris group in response to uplift of the Trans-Mexican Volcanic Belt, a pattern observed in several co-distributed taxa, and suggested that Quaternary climate change likely had little effect on diversification between lineages. Uplift of the Trans-Mexican Volcanic Belt during specific time periods appears to have strongly impacted diversification in Mexican highland taxa.     

From annuals to perennials: phylogeny of subtribe Castillejinae (Orobanchaceae)

Variation in life history strategies is a fundamental question in evolutionary biology, and the cooccurrence of annual and perennial habits in Castilleja and Castillejinae provides the opportunity to study the evolution of plant life history in a phylogenetic context. Molecular phylogenetic analysis of two chloroplast (rps16 and trnL/F) and two nuclear ribosomal (internal and external transcribed spacers) DNA regions support the monophyly of subtribe Castillejinae (Orobanchaceae). A well-supported phylogeny of the six genera (Castilleja [～180 spp.], Clevelandia [1 sp.], Cordylanthus [18 spp.], Ophiocephalus [1 sp.], Orthocarpus [9 spp.], and Triphysaria [5 spp.]) comprising the subtribe is presented, and morphological synapomorphies are identified for the major lineages recovered. Orthocarpus and Triphysaria are both monophyletic; Cordylanthus is biphyletic. Clevelandia and Ophiocephalus are derived from within Castilleja. The perennial Castilleja clade (～160 spp.) is derived from a grade of annual taxa including Castilleja sect. Oncorhynchus (16 spp.), Cordylanthus, Orthocarpus, and Triphysaria. This suggests that the perennial habit evolved a single time from an annual ancestral lineage that persisted throughout the diversification of Castillejinae, contrary to classical interpretations of life history evolution in plants. Given the prevalence of polyploidy among perennial Castilleja species, perenniality may have played an important role in the origin and establishment of polyploidy in Castilleja.     

Revisiting of Carex sect. Confertiflorae s.l. (Cyperaceae): New data from molecular and morphological evidence and first insights on Carex biogeography in East Asia

Carex sect. Confertiflorae s.l. is a medium-sized species group (ca. 40 species) with its center of diversity in E Asia (China and Japan). According to morphological traits, the section has been proposed to split into two sections (sects. Confertiflorae sensu Ohwi and Molliculae Ohwi) up to five different ones (sects. Confertiflorae s.s., Molliculae, Dispalatae Ohwi, Ischnostachyae Ohwi, and Alliiformes Akiyama). Recent phylogenetic reconstructions showed Confertiflorae s.l. not to be monophyletic, as species traditionally considered part of it were found to belong to other clades, whereas species traditionally ascribed to other sections were nested within it. In this study, we investigated the phylogenetic structure, morphological affinities, and biogeographic history of sect. Confertiflorae s.l. We employed a taxon-based approach to explore the morphological affinities of the species considered in sect. Confertiflorae and compared the micromorphology of the nutlets of almost all the taxa using SEM. We included 40 samples representing 31 species/subspecies of sect. Confertiflorae s.l. and used two nuclear (ETS and ITS) and three plastid (trnL-F, matK, and rpl32-trnL ^UAG) molecular markers to reconstruct the phylogeny of the group. The phylogenetic analyses confirmed the polyphyly of sect. Confertiflorae s.l., whose representatives were found within five distinct clades. From these, two clades, sect. Confertiflorae and sect. Molliculae, were found to be closely related and contained the majority of the species. The composition of the two clades agreed with the morphological structure of the group, and we confirmed an exclusive combination of features (namely color of basal sheaths, presence of bract sheath, peduncle of lowest spike, inflorescence sex distribution, shape of pistillate glume apex, and color and veins of utricle, among others) characterizing each of the two clades. The origin of the two clades was found to be in the early Pliocene; however, the majority of the diversification events within each clade took place during the Pleistocene. This illustrates that although Asia has been regarded as having little potential ecological space for Carex to diversify due to its climate stability, groups of sedges sub-endemic from that area may have a fairly recent origin related to glaciations. We proposed the rearrangement of sect. Confertiflorae as previously conceived as three independent sections: the monotypic Alliiformes, sect. Molliculae, and sect. Paludosae.     

Phylogenetic analysis of Helianthus (Asteraceae) based on chloroplast DNA restriction site data

 Chloroplast DNA (cpDNA) restriction site data were used to analyze phylogenetic relationships within Helianthus. Data from new samples were consistent with previous results and showed the genus to be a well-defined (11 site changes) lineage within subtribe Helianthinae. The affinities of 2 species, Viguiera similis and V. phenax (V. ludens) that have sometimes been included in Helianthus were shown to lie outside the genus. The two species of Phoebanthus, however, formed a phylogenetic ingroup to the perennial Helianthus. Within the genus, cpDNA data indicated that there are four distinct phylogenetic lineages. Two of the lineages each contained a single, annual species (H. agrestis and H. porteri, respectively). The remaining annual species collectively formed a third lineage (sect. Helianthus). The fourth lineage contained all of the perennial species, including those of Phoebanthus. Within the perennial lineage, there was little variation in restriction site characters. The 3 species of series Pumili formed a paraphyletic group at the base of the perennial lineage, and the 3 species of series Ciliares formed a group that was supported by a single restriction site character. Received: 2 September 1996 / Accepted: 25 October 1996     

Evolutionary drivers of phylogeographical diversity in the highlands of Mexico: a case study of the Crotalus triseriatus species group of montane rattlesnakes

Aim To assess the genealogical relationships of widespread montane rattlesnakes in the Crotalus triseriatus species group and to clarify the role of Late Neogene mountain building and Pleistocene pine–oak forest fragmentation in driving the diversification of Mexican highland taxa. Location Highlands of mainland Mexico and the south‐western United States (Texas, New Mexico, and Arizona). Methods A synthesis of inferences was used to address several associated questions about the biogeography of the Mexican highlands and the evolutionary drivers of phylogeographical diversity in co‐distributed taxa. We combined extensive range‐wide sampling (130 individuals representing five putative species) and mixed‐model phylogenetic analyses of 2408 base pairs of mitochondrial DNA to estimate genealogical relationships and divergence times within the C. triseriatus species group. We then assessed the tempo of diversification using a maximum likelihood framework based on the birth–death process. Estimated times of divergences provided a probabilistic temporal component and questioned whether diversification rates have remained constant or varied over time. Finally, we looked for phylogeographical patterns in other co‐distributed taxa. Results We identified eight major lineages within the C. triseriatus group, and inferred strong correspondence between maternal and geographic history within most lineages. At least one cryptic species was detected. Relationships among lineages were generally congruent with previous molecular studies, with differences largely attributable to our expanded taxonomic and geographic sampling. Estimated divergences between most major lineages occurred in the Late Miocene and Pliocene. Phylogeographical structure within each lineage appeared to have been generated primarily during the Pleistocene. Although the scale of genetic diversity recognized affected estimated rates of diversification, rates appeared to have been constant through time. Main conclusions The biogeographical history of the C. triseriatus group implies a dynamic history for the highlands of Mexico. The Neogene formation of the Transvolcanic Belt appears responsible for structuring geographic diversity among major lineages. Pleistocene glacial–interglacial climatic cycles and resultant expansions and contractions of the Mexican pine–oak forest appear to have driven widespread divergences within lineages. Climatic change, paired with the complex topography of Mexico, probably produced a myriad of species‐specific responses in co‐distributed Mexican highland taxa. The high degree of genetic differentiation recovered in our study and others suggests that the Mexican highlands may contain considerably more diversity than currently recognized.     

Phylogeny of Stephanomeria and related genera (compositae-lactuceae) based on analysis of 18S-26S nuclear rDNA ITS and ETS sequences

A phylogenetic analysis of DNA sequences from the internal transcribed spacer (ITS), the external transcribed spacer (ETS), and the 5.8S regions of 18S-26S nuclear rDNA from all diploid species of Stephanomeria and related genera shows that Stephanomeria does not include either Munzothamnus blairii (previously S. blairii) or Pleiacanthus spinosus (previously S. spinosa). Without these two taxa, Stephanomeria is a well-supported (100% bootstrap), monophyletic group of ten perennial and six annual species. Munzothamnus blairii and Pleiacanthus spinosus, both now considered members of monotypic genera, had been placed in Stephanomeria primarily because they have the same chromosome number as Stephanomeria and similar pollen surface features, but many disparities were ignored in previous classifications. Within Stephanomeria, an unsuspected sister relationship was detected between the montane S. lactucina and coastal S. cichoriacea. A second clade contained all the annual taxa and five of the perennial species. Among the annuals, strong bootstrap support was obtained for the previously recognized relationships between S. diegensis and S. exigua (98%) and between S. malheurensis and its progenitor, S. exigua subsp. coronaria (96%). Among the five perennial species that constitute a clade with the annuals, the recently described S. fluminea was shown to be sister to S. runcinata, and both of them were closely allied to S. tenuifolia and S. thurberi. The clade including the annuals (and five of the perennial species) was subtended by perennial lineages and pairwise divergence values among the annual taxa were much lower than among the perennial taxa as a group (though not too different than among the perennials in the same clade). The annuals probably originated recently within the genus.     

PSEUDOFILAMENTOUS GREEN ALGAE FORM INDEPENDENT CHLOROPHYTE AND STREPTOPHYTE LINEAGES

The pseudofilamentous condition in green algae has been characterized as the formation of a linear array of autospores. Although it is likely that this characterization will be found to be an over-simplification, it serves as a logical starting point for a study of diversity among pseudofilamentous taxa. Therefore, given that molecular phylogenetic analyses have revealed that coccoid, autospore-formers are found in a number of independent green algal lineages, it is reasonable to expect that pseudofilamentous taxa are likely to be found in a number of distinct lineages. In order to test this hypothesis, data from the nuclear-encoded 18S r   RNA gene were collected from several pseudofilamentous, green algal genera ( Geminella , Gloeotila , Hazenia , Interfilum , Microspora , and Sphaeroplea ) and incorporated into an 18S rRNA database of chlorobiont taxa. Results from phylogenetic analyses of these data support (1) an alliance of Interfilum , two Geminella isolates, and Klebsormidium within the streptophyte lineage, (2) an alliance of two Geminella isolates and Microspora as a sister group to the ulvophycean/chlorophycean/trebouxiophycean clade or as a sister group to trebouxiophycean taxa, (3) an alliance of Hazenia with ulotrichalean taxa, (4) of Gloeotila with trebouxiophycean taxa and (5) an alliance of Sphaeroplea with chlorophycean taxa. These data confirm that the filamentous condition has evolved in a number of independent lineages. Moreover, these data further illustrate that the extent of molecular variability within the green algae is far from fully appreciated.     

Intercontinental disjunctions between eastern Asia and western North America in vascular plants highlight the biogeographic importance of the Bering land bridge from late Cretaceous to Neogene

This review shows a close biogeographic connection between eastern Asia and western North America from the late Cretaceous to the late Neogene in major lineages of vascular plants (flowering plants, gymnosperms, ferns and lycophytes). Of the eastern Asian–North American disjuncts, conifers exhibit a high proportion of disjuncts between eastern Asia and western North America. Several lineages of ferns also show a recent disjunct pattern in the two areas. In flowering plants, the pattern is commonly shown in temperate elements between northeastern Asia and northwestern North America, as well as elements of the relict boreotropical and Neogene mesophytic and coniferous floras. The many cases of intercontinental biogeographic disjunctions between eastern Asia and western North America in plants supported by recent phylogenetic analyses highlight the importance of the Bering land bridge and/or the plant migrations across the Beringian region from the late Cretaceous to the late Neogene, especially during the Miocene. The Beringian region has permitted the filtering and migration of certain plant taxa since the Pliocene after the opening of the Bering Strait, as many conspecific taxa or closely related species occur on both sides of Beringia.     

Molecular phylogenetics and ecological diversification of the transisthmian fish genus Centropomus (Perciformes: Centropomidae).

Phylogenetic relationships among the 12 recognized fish species in the New World genus Centropomus (Pisces, Centropomidae) were analyzed using allozyme electrophoresis and 618 bp of the mitochondrial DNA 16S ribosomal RNA (rRNA) gene. Molecular phylogenetic trees were generally consistent with previously published partial hypotheses based on morphological evidence. However, previously undefined sister group relationships between major species groups were resolved using molecular data, and phylogenetic hypotheses for Centropomus based on 16S rRNA sequences were better supported than were allozyme-based hypotheses. The high level of congruence among the trees inferred from the nuclear and mitochondrial characters provided a firm phylogenetic basis for analysis of ecological diversification and molecular evolution in the genus. Compared to basal Centropomus species, members of the most nested species group were significantly larger in body size and occupied a marine niche only peripherally utilized by their congeners. We also observed substitution rate heterogeneity among 16S rRNA lineages; in contrast to expectations based on "metabolic rate" and "generation interval" models, relative substitution rates were faster than expected for the group of large-bodied snooks. Using the Pliocene rise of the Central American isthmian marine barrier to calibrate rates of 16S ribosomal gene evolution in Centropomus, we found that the rates for the genus were similar to those reported for higher vertebrates. Analysis of the three sets of transisthmian geminate taxa in Centropomus indicated that two of the pairs were probably formed during the Pliocene rise of the isthmus while the third pair diverged several million years earlier.     

Structure,molecular evolution,and phylogenetic utility of the 5(') region of the external transcribed spacer of 18S-26S rDNA in Lessingia (Compositae,Astereae)

The 18S-26S nuclear rDNA external transcribed spacer (ETS) has recently gained attention as a region that is valuable in phylogenetic analyses of angiosperms primarily because it can supplement nucleotide variation from the widely used and generally shorter internal transcribed spacers (ITS-1 and ITS-2) and thereby improve phylogenetic resolution and clade support in rDNA trees. Subrepeated ETS sequences (often occurring in the 5(') region) can, however, create a challenge for systematists interested in using ETS sequence data for phylogeny reconstruction. We sequenced the 5(')ETS for members of Lessingia (Compositae, Astereae) and close relatives (26 taxa total) to characterize the subrepeat variation across a group of closely related plant lineages and to gain improved understanding of the structure, molecular evolution, and phylogenetic utility of the region. The 5(')ETS region of Lessingia and relatives varied in length from approximately 245 to 1009 bp due to the presence of a variable number of subrepeats (one to eight). We assessed homology of the subrepeats using phylogenetic analysis and concluded that only two of the subrepeats and a portion of a third ( approximately 282 bp in total) were orthologous across Lessingia and could be aligned with confidence and included in further analyses. When the partial 5(')ETS data were combined with 3(')ETS and ITS data in phylogenetic analyses, no additional resolution of relationships among taxa was obtained beyond that found from analysis of 3(')ETS + ITS sequences. Inferred patterns of concerted evolution indicate that homogenization is occurring at a faster rate in the 3(')ETS and ITS regions than in the 5(')ETS region. Additionally, homogenization appears to be acting within but not among subrepeats of the same rDNA array. We conclude that challenges in assessing subrepeat orthology across taxa greatly limit the utility of the 5(')ETS region for phylogenetic analyses among species of Lessingia.     

The evolution of sexual and parthenogenetic Warramaba: a window onto Plio–Pleistocene diversification processes in an arid biome

Environmental changes over the Plio‐Pleistocene have been key drivers of speciation patterns and genetic diversification in high‐latitude and mesic environments, yet comparatively little is known about the evolutionary history of species in arid environments. We applied phylogenetic and phylogeographic analyses to understand the evolutionary history of Warramaba grasshoppers from the Australian arid zone, a group including sexual and parthenogenetic lineages. Sequence data (mitochondrial COI) showed that the four major sexual lineages within Warramaba most likely diverged in the Pliocene, around 2–7 million years ago. All sexual lineages exhibited considerable phylogenetic structure. Detailed analyses of the hybrid parthenogenetic species W. virgo and its sexual progenitors showed a pattern of high phylogenetic diversity and phylogeographic structure in northern lineages, and low diversity and evidence for recent expansion in southern lineages. Northern sexual lineages persisted in localized refugia over the Pleistocene, with sustained barriers promoting divergence over this period. Southern parts of the present range became periodically unsuitable during the Pleistocene, and it is into this region that parthenogenetic lineages have expanded. Our results strongly parallel those for sexual and parthenogenetic lineages of the gecko Heteronotia from the same region, indicating a highly general effect of Plio‐Pleistocene environmental change on diversification processes in arid Australia.     

Steady Plio-Pleistocene diversification and a 2-million-year sympatry threshold in a New Zealand cicada radiation

Estimation of diversification rates in evolutionary radiations requires a complete accounting of cryptic species diversity. The rapidly evolving songs of acoustically signaling insects make them good model organisms for such studies. This paper examines the timing of diversification of a large (30 taxon) group of New Zealand cicadas (genus Kikihia Dugdale). We use Bayesian relaxed-clock methods and phylogenetic trees based on nuclear and mitochondrial DNA data, and we apply alternative combinations of evolutionary rate priors and geological calibrations. The extant Kikihia taxa began to diversify near the Miocene/Pliocene boundary around the time of increased mountain-building, and both the mitochondrial and nuclear-gene trees confirm early splits of lineages currently represented by lowland forest-dwelling taxa. Most lineages originated in the Pleistocene, and sustained diversification occurred rapidly at over 0.5 lineages/my, a rate comparable to that of the Hawaiian silverswords. Diversification rate tests suggest an increase in the early to mid-Pliocene, followed by constant diversification from the Late Pliocene onward. No descendants of the many Pleistocene-age splits have evolved the ability to coexist in sympatry, and, where they do come into contact, hybrid zones have been documented based on acoustic and DNA evidence. In contrast, lineages separated in time by approximately 2Myr often overlap in distribution with no evidence of hybridization. This suggests that at least 2Myr has been required to achieve the level of divergence required for reproductive isolation.     

Genetic variability and mycohost association of Ampelomyces quisqualis isolates inferred from phylogenetic analyses of ITS rDNA and actin gene sequences

Ampelomyces quisqualis complex is well known as the most common and widespread hyperparasite of the family Erysiphaceae, the cause of powdery mildew diseases. As commercial biopesticide products it is widely used to control the disease in field and plastic houses. Although genetic diversity within Ampelomyces isolates has been previously recognized, a single name A. quisqualis is still applied to all pycnidial intracellular hyperparasites of powdery mildew fungi. In this study, the phylogenetic relationships among Ampelomyces isolates originating from various powdery mildew fungi in Korea were inferred from Bayesian and maximum parsimony analyses of the sequences of ITS rDNA region and actin gene. In the phylogenetic trees, the Ampelomyces isolates could be divided into four distinct groups with high sequence divergences in both regions. The largest group, Clade 1, mostly accommodated Ampelomyces isolates originating from the mycohost Podosphaera spp. (sect. Sphaerotheca). Clade 2 comprised isolates from several genera of powdery mildews, Golovinomyces, Erysiphe (sect. Erysiphe), Arthrocladiella, and Phyllactinia, and was further divided into two subclades. An isolate obtained from Podosphaera (sect. Sphaerotheca) pannosa was clustered into Clade 3, with those from powdery mildews infecting rosaceous hosts. The mycohosts of Ampelomyces isolates in Clade 4 mostly consisted of species of Erysiphe (sect. Erysiphe, sect. Microsphaera, and sect. Uncinula). The present phylogenetic study demonstrates that Ampelomyces hyperparasite is indeed an assemblage of several distinct lineages rather than a sole species. Although the correlation between Ampelomyces isolates and their mycohosts is not obviously clear, the isolates show not only some degree of host specialization but also adaptation to their mycohosts during the evolution of the hyperparasite.     

Phylogeny of holoparasitic Orobanche (Orobanchaceae) inferred from nuclear ITS sequences

Orobanche is the largest genus among the holoparasitic members of Orobanchaceae. We present the first molecular phylogenetic analysis (using nuclear ITS sequences) that includes members of all sections of Orobanche, Gymnocaulis, Myzorrhiza, Trionychon, and Orobanche. Orobanche is not monophyletic, but falls into two lineages: (1) the Orobanche group comprises Orobanche sect. Orobanche and the small Near Asian genus Diphelypaea and is characterized by a chromosome base number of x=19 and (2) the Phelipanche group contains Orobanche sects. Gymnocaulis, Myzorrhiza, and Trionychon and possesses a chromosome base number of x=12. The relationships between these two groups and to other genera such as Boschniakia or Cistanche remain unresolved. Within the Orobanche group, Orobanche macrolepis and Orobanche anatolica (including Orobanche colorata) constitute two phylogenetically distinct lineages. Intrasectional structurings proposed by some authors for O. sect. Orobanche are not confirmed by the molecular data. In most cases, intraspecific sequence divergence between accessions, if present, is negligible and not correlated with morphological or ecological traits. In a few cases, however, there is evidence for the presence of cryptic taxa.     

A world-wide perspective on crucifer speciation and evolution: phylogenetics,biogeography and trait evolution in tribe Arabideae

Background and Aims

Tribe Arabideae are the most species-rich monophyletic lineage in Brassicaceae. More than 500 species are distributed in the majority of mountain and alpine regions worldwide. This study provides the first comprehensive phylogenetic analysis for the species assemblage and tests for association of trait and characters, providing the first explanations for the enormous species radiation since the mid Miocene.

Methods

Phylogenetic analyses of DNA sequence variation of nuclear encoded loci and plastid DNA are used to unravel a reliable phylogenetic tree. Trait and ancestral area reconstructions were performed and lineage-specific diversification rates were calculated to explain various radiations in the last 15 Myr in space and time.

Key Results

A well-resolved phylogenetic tree demonstrates the paraphyly of the genus Arabis and a new systematic concept is established. Initially, multiple radiations involved a split between lowland annuals and mountain/alpine perennial sister species. Subsequently, increased speciation rates occur in the perennial lineages. The centre of origin of tribe Arabideae is most likely the Irano-Turanian region from which the various clades colonized the temperate mountain and alpine regions of the world.

Conclusions

Mid Miocene early diversification started with increased speciation rates due to the emergence of various annual lineages. Subsequent radiations were mostly driven by diversification within perennial species during the Pliocene, but increased speciation rates also occurred during that epoch. Taxonomic concepts in Arabis are still in need of a major taxonomic revision to define monophyletic groups.     

Correlated evolution of life history and host range in the nonphotosynthetic parasitic flowering plants Orobanche and Phelipanche (Orobanchaceae)

Most members of the nonphotosynthetic parasitic genera Orobanche and Phelipanche (Orobanchaceae) have narrow host ranges, and, as they grow on perennial hosts, are (at least potentially) perennial themselves. A few species, however, have wide host ranges and grow on annual hosts, and are thus (at least facultatively) annuals themselves. Among the latter are the weedy species, which include economically important pest taxa such as Orobanche crenata or Phelipanche aegyptiaca. Using a phylogenetically based maximum likelihood approach, which takes phylogenetic and branch length uncertainty into account, we can show that the life trait host range and life history evolve in a correlated fashion. This supports the hypothesis that parasite specialization is associated with predictable resources (i.e. long-lived hosts) and generalism with unpredictable ones (i.e. short-lived hosts), a pattern often found in animal parasites. The mechanisms and temporal sequence of the life trait changes and their interrelations remain speculative.