Patterns of plastid and nuclear variation among apomictic polyploids of Hieracium: evolutionary processes and taxonomic implications

Background and Aims

Apomictic species (with asexual seed production) make up for 20–50 % of all taxonomically recognized species in northern Europe, but the phylogenetic relationships of apomictic species and the mode of evolution and speciation remain largely unknown and their taxonomy is consequently disputed.

Methods

In the present study, plastid psbD-trnT sequences (349 accessions) and 12 nuclear microsatellite loci (478 accessions) were used to create an overview of the molecular variation in (mainly) northern European members of the most species-rich of all plant genera, Hieracium s.s. The results are discussed and interpreted in the context of morphological and cytological data on the same species.

Key Results and Conclusions

The complete psbD-trnT alignment was 1243 bp and 50 polymorphisms defined 40 haplotypes. All haplotypes found in the sections of the genus distributed in the northern European lowlands fell into one of two main groups, group H and group V, mutually separated by seven or eight polymorphisms. All accessions belonging to H. sects. Foliosa, Hieracioides (viz. H. umbellatum) and Tridentata and all but one accession of triploid species of H. sects. Oradea and Vulgata showed haplotypes of group V. Haplotypes of group H were found in all accessions of H. sects. Bifida and Hieracium and in all tetraploid representatives of H. sects. Oreadea and Vulgata. Additional haplotypes were found in accessions of the genus Pilosella and in southern European and Alpine sections of Hieracium. In contrast, the distribution of individual haplotypes in the two major groups appeared uncorrelated with morphology and current taxonomy, but polymorphisms within species were only rarely encountered. In total, 160 microsatellite alleles were identified. Levels of variation were generally high with only nine pairs of accessions being identical at all loci (in all cases representing accessions of the same species). In the neighbor-joining analysis based on the microsatellite data, accessions of the same species generally clustered together and some smaller groups of species congruent with morphology and/or current taxonomy were recovered but, except for H. sect. Oreadea, most larger groups were not correlated with morphology. Although the plastid DNA sequences show too little variation and the nuclear microsatellites are too variable to resolve relationships successfully among species or to fully understand processes of evolution, it is concluded that both species and sections as defined by morphology are largely congruent with the molecular data, that gene flow between the sections is rare or non-existent and that the tetraploid species may constitute the key to understanding evolution and speciation in this genus.     

Breeding system diversification and evolution in American Poa supersect. Homalopoa (Poaceae: Poeae: Poinae)

Background and Aims Poa subgenus Poa supersect. Homalopoa has diversified extensively in the Americas. Over half of the species in the supersection are diclinous; most of these are from the New World, while a few are from South-East Asia. Diclinism in Homalopoa can be divided into three main types: gynomonoecism, gynodioecism and dioecism. Here the sampling of species of New World Homalopoa is expanded to date its origin and diversification in North and South America and examine the evolution and origin of the breeding system diversity.Methods A total of 124 specimens were included in the matrix, of which 89 are species of Poa supersect. Homalopoa sections Acutifoliae, Anthochloa, Brizoides, Dasypoa, Dioicopoa, Dissanthelium, Homalopoa sensu lato (s.l.), Madropoa and Tovarochloa, and the informal Punapoa group. Bayesian and parsimony analyses were conducted on the data sets based on four markers: the nuclear ribosomal internal tanscribed spacer (ITS) and external transcribed spacer (ETS), and plastid trnT-L and trnL-F. Dating analyses were performed on a reduced Poa matrix and enlarged Poaceae outgroup to utilize fossils as calibration points. A relaxed Bayesian molecular clock method was used.Key Results Hermaphroditism appears to be pleisiomorphic in the monophyletic Poa supersect. Homalopoa, which is suggested to have originated in Eurasia 8·4–4·2 million years ago (Mya). The ancestor of Poa supersect. Homalopoa radiated throughout the New World in the Late Miocene–Early Pliocene, with major lineages originating during the Pliocene to Pleistocene (5–2 Mya). Breeding systems are linked to geographic areas, showing an evolutionary pattern associated with different habitats. At least three major pathways from hermaphroditism to diclinism are inferred in New World Homalopoa: two leading to dioecism, one via gynodioecism in South America and another directly from hermaphroditism in North America, a result that needs to be checked with a broader sampling of diclinous species in North America. A third pathway leads from hermaphroditism to gynomonoecism in Andean species of South America, with strictly pistillate species evolving in the highest altitudes.Conclusions Divergence dating provides a temporal context to the evolution of breeding systems in New World Poa supersect. Homalopoa. The results are consistent with the infrageneric classification in part; monophyletic sections are confirmed, it is proposed to reclassify species of sect. Acutifoliae, Dasypoa and Homalopoa s.l. and it is acknowledged that revision of the infrageneric taxonomy of the gynomonoecious species is needed.     

Phylogeny of the cycads based on multiple single-copy nuclear genes: congruence of concatenated parsimony,likelihood and species tree inference methods

Background and aims

Despite a recent new classification, a stable phylogeny for the cycads has been elusive, particularly regarding resolution of Bowenia, Stangeria and Dioon. In this study, five single-copy nuclear genes (SCNGs) are applied to the phylogeny of the order Cycadales. The specific aim is to evaluate several gene tree–species tree reconciliation approaches for developing an accurate phylogeny of the order, to contrast them with concatenated parsimony analysis and to resolve the erstwhile problematic phylogenetic position of these three genera.

Methods

DNA sequences of five SCNGs were obtained for 20 cycad species representing all ten genera of Cycadales. These were analysed with parsimony, maximum likelihood (ML) and three Bayesian methods of gene tree–species tree reconciliation, using Cycas as the outgroup. A calibrated date estimation was developed with Bayesian methods, and biogeographic analysis was also conducted.

Key Results

Concatenated parsimony, ML and three species tree inference methods resolve exactly the same tree topology with high support at most nodes. Dioon and Bowenia are the first and second branches of Cycadales after Cycas, respectively, followed by an encephalartoid clade (Macrozamia–Lepidozamia–Encephalartos), which is sister to a zamioid clade, of which Ceratozamia is the first branch, and in which Stangeria is sister to Microcycas and Zamia.

Conclusions

A single, well-supported phylogenetic hypothesis of the generic relationships of the Cycadales is presented. However, massive extinction events inferred from the fossil record that eliminated broader ancestral distributions within Zamiaceae compromise accurate optimization of ancestral biogeographical areas for that hypothesis. While major lineages of Cycadales are ancient, crown ages of all modern genera are no older than 12 million years, supporting a recent hypothesis of mostly Miocene radiations. This phylogeny can contribute to an accurate infrafamilial classification of Zamiaceae.     

A molecular survey concerning the origin of Cyperus esculentus (Cyperaceae,Poales): two sides of the same coin (weed vs. crop)

Background and Aims Cyperus esculentus is widespread in tropical and temperate zones and is also present in cooler regions. It is used as a crop plant, but it also occurs in the wild and as a weed. As a consequence of its ecological plasticity, C. esculentus has remarkable variability, with several morphotypes. Four wild-type varieties are presently recognized, in addition to the cultivated form. This study investigates the phylogenetic position and biogeography of C. esculentus with the objective of contributing new data to increase the understanding of its evolutionary history.Methods Genealogical relationships among genotypes were inferred by using plastid DNA haplotype and nuclear ribosomal (nr) DNA ribotype sequences for 70 specimens either collected in the field or obtained from herbaria. Statistical dispersal–vicariance (S-DIVA) and Bayesian binary method (BBM) analyses were used to reconstruct the possible ancestral ranges of C. esculentus. In order to determine the age of C. esculentus, a time-measured phylogenetic analysis was performed.Key Results Considerable variation between the chosen nuclear and plastid markers was detected (27 ribotypes vs. six haplotypes). No geographical structure was displayed among the haplotypes, but information on the dispersal pattern may be deduced. Two types of ribotypes were detected in nrDNA, with an evident geographical segregation into an Old World group and a polymorphic New World group. Both S-DIVA and BBM analyses suggested a biogeographical history in which dispersal from the African region has been crucial in shaping the current distribution pattern of C. esculentus. The most recent common ancestor between C. esculentus races has an age of 5.1 million years (95 % highest posterior density 2.5–10.2).Conclusions The molecular analysis provides novel insights into the evolutionary history of C. esculentus. The results have various taxonomic and phylogenetic implications, including a hypothesis on the origin and phylogeography of this species, which probably originated in the late Cenozoic in Africa, and reached the Americas repeatedly, independently of Columbian exchanges.     

Two newly recognized species of Hemidactylus (Squamata,Gekkonidae) from the Arabian Peninsula?and Sinai,Egypt

A recent molecular phylogeny of the Arid clade of the genus Hemidactylus revealed that the recently described H. saba and two unnamed Hemidactylus species from Sinai, Saudi Arabia and Yemen form a well-supported monophyletic group within the Arabian radiation of the genus. The name ‘Hemidactylus saba species group’ is suggested for this clade. According to the results of morphological comparisons and the molecular analyses using two mitochondrial (12S and cytb) and four nuclear (cmos, mc1r, rag1, rag2) genes, the name Hemidactylus granosus Heyden, 1827 is resurrected from the synonymy of H. turcicus for the Sinai and Saudi Arabian species. The third species of this group from Yemen is described formally as a new species H. ulii sp. n. The phylogenetic relationships of the members of ‘Hemidactylus saba species group’ are evaluated and the distribution and ecology of individual species are discussed.     

New Guinea highland origin of a widespread arthropod supertramp

The biologically and geologically extremely diverse archipelagos of Wallacea, Australasia and Oceania have long stimulated ecologists and evolutionary biologists. Yet, few molecular phylogenetic analyses of the terrestrial fauna have been carried out to understand the evolutionary patterns. We use dense taxon and character sampling of more than 7000 bp DNA sequence data for a group of diving beetles ranging from the Holarctic throughout Asia to as far east as French Polynesia. We here show that an ecologically diverse, common and widespread (Portugal to New Zealand) arthropod supertramp species originated in the highlands of New Guinea, ca 6.0–2.7 Myr ago. The approximately 25 closely related species are narrow endemics in Australasia/Oceania. The ancestor of this clade colonized that region from Eurasia ca 9–7 Myr ago. Our finding contradicts the widely held view of local endemism as an evolutionary dead end, as we find multiple peripatric speciation events within the Pleistocene and complex colonization patterns between the Oriental and Australian zoogeographic regions, including the recolonization of Eurasia, jumping across Wallace''s line and colonization of continental Australia out of New Guinea. Our study strongly highlights the importance of dispersal over water gaps in shaping biogeographic patterns.     

Efficacy of leaves extract of Calotropis procera Ait. (Asclepiadaceae) in controlling Anopheles arabiensis and Culex quinquefasciatus mosquitoes

The present study aimed to investigate, the larvicidal, adult emergence inhibition and oviposition deterrent activity of aqueous leaves extract of Calotropis procera against Anopheles arabiensis and Culex quinquefasciatus as natural mosquito larvicide. The larvicidal activity was monitored against 2nd, 3rd and 4th instar larvae of each mosquito species 24 h post-treatment. Adult emergence inhibition activity was tested by exposing 3rd instar larvae of each mosquito species to different concentrations of extracts (200, 400, 600, 800 and 1000 ppm for An. arabiensis and 100, 200, 300, 400, 500 and 600 ppm for Cx. quinquefasciatus). Probit analysis was used to analyze data from bioassay experiments. The oviposition deterrent activity was tested by using three different concentrations of extracts (1000, 500 and 200 for An. arabiensis, and 1000, 500 and 100 for Cx. quinquefasciatus) that caused high, moderate and low larval mortality in the larvicidal experiment against 3rd instar larvae. It was found that, LC50–LC90 values calculated were 273.53–783.43, 366.44–1018.59 and 454.99–1224.62 ppm for 2nd, 3rd and 4th larval instars, respectively, of An. arabiensis and 187.93–433.51, 218.27–538.27 and 264.85–769.13 ppm for 2nd, 3rd and 4th larval instars, respectively, of Cx. quinquefasciatus. Fifty percent of adult emergence inhibition (EI50) was shown at 277.90 and 183.65 ppm for An. arabiensis and Cx. quinquefasciatus, respectively. The pupal stage was not affected till a concentration of 5000 ppm. The extract showed oviposition deterrence and effective repellence against both mosquito species at different concentrations, with the observation on that maximal eggs were laid in low concentration of extract. These results suggest that the leaves extract of C. procera possess remarkable larvicidal, adult emergence inhibitor, repellent and oviposition deterrent effect against both An. arabiensis and Cx. quinquefasciatus, and might be used as natural biocides for mosquito control.     

Reticulate evolution in North American black-fruited hawthorns (Crataegus section Douglasia; Rosaceae): evidence from nuclear ITS2 and plastid sequences

Background and Aims

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.

Methods

ITS2 was extensively cloned so as to document inter- and intraindividual variation in this locus, using hawthorns of western North America where the genus Crataegus is represented by only two widely divergent groups, the red-fruited section Coccineae and the black-fruited section Douglasia. Additional sequence data from selected loci on the plastid genome were obtained to enhance further the interpretation of the ITS2 results.

Key Results

In the ITS2 gene tree, ribotypes from western North American hawthorns are found in two clades. Ribotypes from diploid members of section Douglasia occur in one clade (with representatives of the east-Asian section Sanguineae). The other clade comprises those from diploid and polyploid members of section Coccineae. Both clades contribute ribotypes to polyploid Douglasia. Data from four plastid-derived intergenic spacers demonstrate the maternal parentage of these allopolyploids.

Conclusions

Repeated hybridization between species of section Douglasia and western North American members of section Coccineae involving the fertilization of unreduced female gametes explains the observed distribution of ribotypes and accounts for the phenetic intermediacy of many members of section Douglasia.     

A new species of Diartiger Sharp (Staphylinidae,Pselaphinae, Clavigeritae) from the Fengyangshan – Baishanzu Nature Reserve,East China

A new clavigerine pselaphine, Diartiger zhejiangensis Yin & Li, sp. n., from the Fengyangshan – Baishanzu Nature Reserve, southern Zhejiang, is described, illustrated, and compared with congeners. The species is hosted by ants in the genus Lasius. The key to Diartiger species from China is modified to accommodate the new species.     

Nodule morphology,symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the southern African crotalarioid clade Lotononis s.l.

Background and Aims

The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.s.). Listia species are symbiotically specific and form lupinoid nodules with rhizobial species of Methylobacterium and Microvirga. This work investigated whether these symbiotic traits were confined to Listia by determining the ability of rhizobial strains isolated from species of Lotononis s.l. to nodulate Listia, Leobordea and Lotononis s.s. hosts and by examining the morphology and structure of the resulting nodules.

Methods

Rhizobia were characterized by sequencing their 16S rRNA and nodA genes. Nodulation and N₂ fixation on eight taxonomically diverse Lotononis s.l. species were determined in glasshouse trials. Nodules of all hosts, and the process of infection and nodule initiation in Listia angolensis and Listia bainesii, were examined by light microscopy.

Key Results

Rhizobia associated with Lotononis s.l. were phylogenetically diverse. Leobordea and Lotononis s.s. isolates were most closely related to Bradyrhizobium spp., Ensifer meliloti, Mesorhizobium tianshanense and Methylobacterium nodulans. Listia angolensis formed effective nodules only with species of Microvirga. Listia bainesii nodulated only with pigmented Methylobacterium. Five lineages of nodA were found. Listia angolensis and L. bainesii formed lupinoid nodules, whereas nodules of Leobordea and Lotononis s.s. species were indeterminate. All effective nodules contained uniformly infected central tissue. Listia angolensis and L. bainesii nodule initials occurred on the border of the hypocotyl and along the tap root, and nodule primordia developed in the outer cortical layer. Neither root hair curling nor infection threads were seen.

Conclusions

Two specificity groups occur within Lotononis s.l.: Listia species are symbiotically specific, while species of Leobordea and Lotononis s.s. are generally promiscuous and interact with rhizobia of diverse chromosomal and symbiotic lineages. The seasonally waterlogged habitat of Listia species may favour the development of symbiotic specificity.     

Hesperentomon yangi sp. n. from Jiangsu Province,Eastern China,with analyses of DNA barcodes (Protura,Acerentomata, Hesperentomidae)

Hesperentomon yangi sp. n. is described from eastern China. Its DNA barcodes are sequenced and compared to the similar species of the genus. Hesperentomon yangi sp. n. is characterized by 12 posterior setae on tergites II–VI, 8 posterior setae on sternites IV–VI (seta Pc absent), absence of seta sd4 on head, absence of seta P2a on tergite VII, 6 and 8 anterior setae on mesosternum and metasternum respectively, and few teeth on comb. It differs from Hesperentomon xiningense Bu & Yin, 2007 and Hesperentomon nanshanensis Bu & Yin, 2007 in the chaetotaxy of mesosternum and metanotum, maxillary gland, length and shape of some sensilla on foretarsus, as well as the body porotaxy. The genetic divergences of DNA barcodes sequences between Hesperentomon yangi sp. n., Hesperentomon xiningense and Hesperentomon nanshanensis are 24.1% on average, which is distinctly higher than the divergences between individuals of the new species (0.5%). Molecular data provide a solid evidence of the new species identified by the morphological characters.     

Thermus parvatiensis RLT sp. nov., Isolated from a Hot Water Spring,Located Atop the Himalayan Ranges at Manikaran,India

A Gram negative, yellow pigmented, rod shaped bacterium designated as RL^T was isolated from a hot water spring (90–98 °C) located at Manikaran in Northern India. The isolate grows at 60–80 °C (optimum, 70 °C) and at pH 7.0–9.0 (optimum pH 7.2). Phylogenetic analysis of 16S rRNA gene sequences and levels of DNA–DNA relatedness together indicate that the new isolate represents a novel species of the genus Thermus with closest affinity to Thermus thermophilus HB8^T (99.5 %) followed by Thermus arciformis (96.4 %). A comparative analysis of partial sequences of housekeeping genes (HKG) further revealed that strain RL^T is a novel species belonging to the genus Thermus. The melting G+C content of strain RL^T was calculated as 68.7 mol%. The DNA–DNA relatedness value of strain RL^T with its nearest neighbours (>97 %) was found to be less than 70 % indicating that strain RL^T represents a novel species of the genus Thermus. MK-8 was the predominant respiratory quinone. The presence of characteristic phospholipid and glycolipid further confirmed that strain RL^T belongs to the genus Thermus. The predominant fatty acids of strain RL^T were iso-C_17:0 (23.67 %) and iso-C_15:0 (24.50 %). The results obtained after DNA–DNA hybridization, biochemical and physiological tests clearly distinguished strain RL^T from its closely related species. Thus, strain RL^T represents a novel species of the genus Thermus for which the name Thermus parvatiensis is proposed (=DSM 21745^T= MTCC 8932^T).

Electronic supplementary material

The online version of this article (doi:10.1007/s12088-015-0538-4) contains supplementary material, which is available to authorized users.     

Heterodera achilleae n. sp. (Nematoda: Heteroderidae) from Yarrow in Yugoslavia

Heterodera achilleae n. sp., a member of the H. rostochiensis group, is described and illustrated from roots of yarrow, Achillea millefolium L. in Sarajevo, Yugoslavia. This new, round-cyst species differs from closely related species especially as follows: (1) from H. leptonepia, by having stouter larvae (a = 21), with longer styler (25 μ), and with outlet of dorsal esophageal gland averaging 5.7 μ from base o f styler; (2) from H. millefolii, in having excretory pore at base of neck and small, straight vulval slit of 5 μ; (3) from H. rostochiensis, in having a B/A ratio (Granek''s ratio) of 1.6 ; (4) from H. tabacum, by longer female stylet, two annules on female head, and males with outlet of dorsal esophageal gland further back (5.7 μ). In addition, H. achilleae n. sp. differs from the latter three species in having prominent longitudinal striae on the anterior half, or more, of cysts and females.     

Two common and problematic leucochrysine species – Leucochrysa (Leucochrysa) varia (Schneider) and L. (L.) pretiosa (Banks) (Neuroptera,Chrysopidae): redescriptions and synonymies

We dedicate this article to the memory of Sergio de Freitas, FCAV-UNESP, Jaboticabal, São Paulo, Brazil (deceased, 2012). He was an active and enthusiastic Neuropterist and the cherished mentor and friend of Francisco Sosa.Leucochrysa McLachlan is the largest genus in the Chrysopidae, yet it has received relatively little taxonomic attention. We treat two problematic and common Leucochrysa species – Leucochrysa (Leucochrysa) varia (Schneider, 1851) and Leucochrysa (Leucochrysa) pretiosa (Banks, 1910). Both are highly variable in coloration and were described before the systematic importance of chrysopid genitalia was recognized. Recent studies show that these species occur within a large complex of cryptic species and that they have accumulated a number of taxonomic problems. We identify new synonymies for each of the species–for Leucochrysa (Leucochrysa) varia: Leucochrysa (Leucochrysa) ampla (Walker, 1853), Leucochrysa internata (Walker, 1853), and Leucochrysa (Leucochrysa) walkerina Navás, 1913; for Leucochrysa (Leucochrysa) pretiosa: Leucochrysa (Leucochrysa) erminea Banks, 1946. The synonymy of Leucochrysa delicata Navás, 1925 with Leucochrysa (Leucochrysa) pretiosa is stabilized by the designation of a neotype. The following species, which were previously synonymized with Leucochrysa (Leucochrysa) varia or Leucochrysa (Leucochrysa) pretiosa, are reinstated as valid: Leucochrysa (Leucochrysa) phaeocephala Navás, 1929, Leucochrysa (Leucochrysa) angrandi (Navás, 1911), and Leucochrysa (Leucochrysa) variata (Navás, 1913). To help stabilize Leucochrysa taxonomy, lectotypes are designated for Allochrysa pretiosa and Allochrysa variata. Finally, Leucochrysa vegana Navás, 1917 is considered a nomen dubium.     

Population genetic evidence for speciation pattern and gene flow between Picea wilsonii,P. morrisonicola and P. neoveitchii

Background and Aims

Genetic drift due to geographical isolation, gene flow and mutation rates together make it difficult to determine the evolutionary relationships of present-day species. In this study, population genetic data were used to model and decipher interspecific relationships, speciation patterns and gene flow between three species of spruce with similar morphology, Picea wilsonii, P. neoveitchii and P. morrisonicola. Picea wilsonii and P. neoveitchii occur from central to north-west China, where they have overlapping distributions. Picea morrisonicola, however, is restricted solely to the island of Taiwan and is isolated from the other two species by a long distance.

Methods

Sequence variations were examined in 18 DNA fragments for 22 populations, including three fragments from the chloroplast (cp) genome, two from the mitochondrial (mt) genome and 13 from the nuclear genome.

Key Results

In both the cpDNA and the mtDNA, P. morrisonicola accumulated more species-specific mutations than the other two species. However, most nuclear haplotypes of P. morrisonicola were shared by P. wilsonii, or derived from the dominant haplotypes found in that species. Modelling of population genetic data supported the hypothesis that P. morrisonicola derived from P. wilsonii within the more recent past, most probably indicating progenitor–derivative speciation with a distinct bottleneck, although further gene flow from the progenitor to the derivative continued. In addition, the occurrence was detected of an obvious mtDNA introgression from P. neoveitchii to P. wilsonii despite their early divergence.

Conclusions

The extent of mutation, introgression and lineage sorting taking place during interspecific divergence and demographic changes in the three species had varied greatly between the three genomes. The findings highlight the complex evolutionary histories of these three Asian spruce species.     

Comparison of germination responses of Anigozanthos flavidus (Haemodoraceae), Gyrostemon racemiger and Gyrostemon ramulosus (Gyrostemonaceae) to smoke-water and the smoke-derived compounds karrikinolide (KAR1) and glyceronitrile

Background and Aims

A major germination-promoting chemical in smoke-water is 3-methyl-2H-furo[2,3-c]pyran-2-one (karrikinolide, KAR₁). However, not all species that germinate in response to smoke-water are responsive to KAR₁, such as Tersonia cyathiflora (Gyrostemonaceae). In this study, a test was made of whether two Gyrostemon species (Gyrostemonaceae) that have previously been shown to respond to smoke-water, respond to KAR₁. If not, then the smoke-derived chemical that stimulates germination of these species is currently unknown. Recently, glyceronitrile was isolated from smoke-water and promoted the germination of certain Anigozanthos species (Haemodoraceae). Whether this chemical promotes Gyrostemon racemiger germination is also examined. Furthermore, an investigation was carried out into whether these species germinate in response to smoke-water derived from burning cellulose alone.

Methods Gyrostemon racemiger

and G. ramulosus seeds were buried after collection and retrieved in autumn the following year when dormancy was alleviated and seeds had become responsive to smoke-water. Anigozanthos flavidus seeds were after-ripened at 35 °C to alleviate dormancy. Gyrostemon and Anigozanthos seeds were then tested with ‘Seed Starter’ smoke-water, KAR₁, glyceronitrile and cellulose-derived smoke-water.

Key Results

Although Gyrostemon racemiger, G. ramulosus and A. flavidus were all stimulated to germinate by ‘Seed Starter’ smoke-water, none of these species responded to KAR₁. Gyrostemon racemiger germination was not promoted by glyceronitrile. This is in contrast to A. flavidus, where glyceronitrile, at concentrations of 1–500 µm, promoted germination, although seedling growth was inhibited at ≥400 µm. Maximum A. flavidus germination occurred at glyceronitrile concentrations of 25–300 µm. Some Gyrostemon germination was promoted by cellulose-derived smoke-water.

Conclusions

KAR₁ and glyceronitrile, chemicals in smoke-water that are known to stimulate germination in other species, did not promote the germination of G. racemiger. This suggests that other chemical(s) which promote germination are present in smoke, and may be derived from burning cellulose alone.     

Comparisons of Mitochondrial DNA from the Sibling Species Heterodera glycines and H. schachtii

Restriction fragment patterns of mitochondrial DNA from sibling species of cyst nematodes Heterodera glycines and H. schachtii were examined. Fourteen restriction endonucleases recognizing four, five, and six base-pair sequences yielded a total of 90 scorable fragments of which 10% were shared by both species. Mitochondrial genome sizes for H. glycines and H. schachtii were estimated to be 22.5-23.5 kb and 23.0 kb, respectively. A single wild type mitochondrial genome was identified in all populations of H. glycines examined, although other mitochondrial genomes were present in some populations. The H. schachtii genome exhibited 57 scorable fragments, compared with 33 identified in the H. glycines wild type genome. The estimated nucleotide sequence divergence between the two species was p = 0.145. This estimate suggests these species diverged from a common ancestor 7.3-14.8 million years ago.     

Interactive effects of elevated CO2 and precipitation change on leaf nitrogen of dominant Stipa L. species

Nitrogen (N) serves as an important mineral element affecting plant productivity and nutritional quality. However, few studies have addressed the interactive effects of elevated CO₂ and precipitation change on leaf N of dominant grassland genera such as Stipa L. This has restricted our understanding of the responses of grassland to climate change. We simulated the interactive effects of elevated CO₂ concentration and varied precipitation on leaf N concentration (N_mass) of four Stipa species (Stipa baicalensis, Stipa bungeana, Stipa grandis, and Stipa breviflora; the most dominant species in arid and semiarid grassland) using open-top chambers (OTCs). The relationship between the N_mass of these four Stipa species and precipitation well fits a logarithmic function. The sensitivity of these four species to precipitation change was ranked as follows: S. bungeana > S. breviflora > S. baicalensis > S. grandis. The N_mass of S. bungeana was the most sensitive to precipitation change, while S. grandis was the least sensitive among these Stipa species. Elevated CO₂ exacerbated the effect of precipitation on N_mass. N_mass decreased under elevated CO₂ due to growth dilution and a direct negative effect on N assimilation. Elevated CO₂ reduced N_mass only in a certain precipitation range for S. baicalensis (163–343 mm), S. bungeana (164–355 mm), S. grandis (148–286 mm), and S. breviflora (130–316 mm); severe drought or excessive rainfall would be expected to result in a reduced impact of elevated CO₂. Elevated CO₂ affected the N_mass of S. grandis only in a narrow precipitation range. The effect of elevated CO₂ reached a maximum when the amount of precipitation was 253, 260, 217, and 222 mm for S. baicalensis, S. bungeana, S. grandis, and S. breviflora, respectively. The N_mass of S. grandis was the least sensitive to elevated CO₂. The N_mass of S. breviflora was more sensitive to elevated CO₂ under a drought condition compared with the other Stipa species.