Effective number of pollen parents in clonal seed orchards

Summary A method for quantifying mating behavior in clonal seed orchards of forest tree species is presented. It involves the estimation of effective numbers of pollen parents from seed samples collected from individual ramets in such orchards. These effective numbers are variance effective numbers for populations of male gametes that are successful in uniting with ovules to produce viable seed. Three such effective numbers are defined for clonal seed orchards:N _p (a) for male gamete populations for ramets within clones,N _p (b) for male gamete populations for clones, andN _p (c) for male gamete populations for entire orchards. Estimators for these effective numbers and for standardized variances of allele frequencies in the male gametic populations are presented. Expressions are also given for the confidence intervals for each of the three effective numbers. Estimates of these parameters and the corresponding confidence intervals for two seed orchards are presented and interpreted.     

Unexpected hybridization reveals the utility of genetics in native plant restoration

Native plant materials (NPMs) are increasingly utilized during the restoration of disturbed plant communities. Here, we analyze next‐generation genetic sequencing data for Hilaria jamesii, a dominant graminoid across drylands of the southwestern United States, and document that the species' only commercially‐available NPM, “Viva,” is a hybrid between H. jamesii and its sister species, Hilaria mutica. In fact, hybrids between these species are common where they geographically overlap. Furthermore, we show that the “Viva” hybrid has successfully been moved beyond the hybrid zone and into the core range of H. jamesii. The potential ramifications of introducing novel genetic material into H. jamesii are discussed, as well as the utility of genetic analyses to protect species' natural patterns of genetic diversity and help managers make informed decisions regarding the development and deployment of NPMs.     

CHROMOSOME NUMBERS IN SOUTH AMERICAN HAPLOPAPPUS CASS. (COMPOSITAE)

Chromosome counts are reported for 33 species from all four sections of the genus Haplopappus in South America. These include first reports for 28 species and two putative hybrids. All chromosome numbers reported herein are 2n = 5_II, with the exception of H. prunelloides with 2_n = 6_II. Unlike the North American species, the morphological diversity of South American taxa is not concomitant with chromosomal variation.     

Chromosome numbers and reproduction inRubus subgen.Malachobatus

A review of current knowledge of chromosome numbers and modes of reproduction in the genusRubus L. is presented. Chromosome numbers from some species of subg.Malachobatus Focke together with results of crossing experiments are reported for the first time.     

The historical context of contemporary climatic adaptation: a case study in the climatically dynamic and environmentally complex southwestern United States

The process of adaptation can be highly dependent upon historical and contemporary factors, especially in environmentally and topographically complex regions affected by Pleistocene glaciations. Here, we investigate Hilaria jamesii (Poaceae), a dryland C₄ graminoid, to test how patterns of adaptive genetic variation are linked to its glacial and post-glacial history. We show that the species persisted in a single, southern refugium during the last glacial period and subsequently migrated throughout its current distribution concurrent with post-glacial warming. The species’ putative adaptive genetic variation correlates with climatic gradients (e.g. monsoon precipitation and mean diurnal temperature range) that covary with the species’ probable route of demographic expansion. The short timescale and multiple climatic dimensions of adaptation imply that natural selection acted primarily upon standing genetic variation. These findings suggest that restoration and conservation practices should prioritize the maintenance of standing genetic variation to ensure that species have the capacity to respond to future environmental changes.     

Notes on Mexican grasses IX. Miscellaneous chromosome numbers—3

Chromosome numbers are reported for 105 collections which represent 59 species belonging to 35 genera. For two of these genera:Blepharoneuron andTriniochloa no documented chromosome counts have been published to date. Records for the following species:Aristida arizonica, A. pansa, A. schiedeana, Blepharoneuron tricholepis, Deschampsia pringlei, Eragrostis palmeri,Leptochloa viscida, Munroa squarrosa, Panicum vaseyanum, Setaria grisebachii, andTriniochloa stipoides are the first for these taxa. Counts of 2n = 28 forAgrostis perennans, 2n = 20 forAegopogon cenchroides, 2n = 20 forBuchloË dactyloides, 2n = 54 forDigitaria filiformis, 2n = 60 and 2n = ca. 74 forEragrostis intermedia, 2n = 32 forErioneuron grandiflorum andE. pilosum, 2n = 44 forHilaria cenchroides, 2n = 38 and 2n = ca. 180 forHilaria mutica, 2n = 40 forPereilema crinitum, 2n = 28 forScleropogon brevifolius, 2n = ca. 108 forSetaria leucopila, and 2n = 36 forOplismenus burmannii are different from any published report for these species. Cytological information on Mexican material of the following ten species:Agrostis perennans, Aristida hamulosa,Bouteloua aristidoides, Eragrostis cilianensis, Sporobolus nealleyi, Tridens muticus,Digitaria filiformis, Hackelochloa granularis, Oplismenus burmannii, andPennisetum ciliare is here presented for the first time.     

Cytological variation and evolution withinPelargonium sectionHoarea (Geraniaceae)

Chromosome numbers of 65 species of sect.Hoarea have been determined. These show three basic chromosome numbers, x = 11, 10 and 9. Only a few species are tetraploid. In five species both diploid and tetraploid cytotypes are reported. Several cases of deviations in chromosome numbers and cytological abnormalities were found, most of these being related to the presence of B chromosomes that occur in eight species. Evidence is presented to suggest that the basic chromosome numbers of x = 10 and x = 9 are derived from x = 11 by centric fusion. Although variation in basic chromosome number withinPelargonium has been the subject of detailed study, this is the first time that evidence has been found for a mechanism of change in basic number, that of centric fusion by Robertsonian translocation. For the species of sect.Hoarea with x = 9, where the evidence for Robertsonian translocation is greatest, this process has probably taken place quite recently. In contrast to results from other sections of the genusPelargonium, the three different basic numbers of sect.Hoarea do not contradict its delimitation as a natural taxon.     

A cytotaxonomic analysis of Chinese Polygonatum (Asparagaceae) species

Chromosome numbers and karyotype data of 19 Chinese Polygonatum species generated from 51 populations are presented in this paper. Karyograms of P. cirrhifoliodes, P. gracile, P. hookeri, P. jinzhaiense and P. nodosum are reported for the first time. The chromosome numbers 2n = 28 for P. hookeri and 2n = 60 for P. zanlanscianense are reported for the first time. Satellite chromosomes in the analyzed Polygonatum species can be classified into nine types with respect to the position of secondary constrictions. The occurrence of these types correlates with the infrageneric classification. Karyotypes are bimodal in most Polygonatum species. Polyploidy is common in Polygonatum, and polyploid taxa exhibit higher karyotype asymmetry.     

CHROMOSOME NUMBERS IN THE COMPOSITAE: COLOMBIAN SPECIES

Chromosome numbers are presented for 76 species belonging to 35 genera of Compositae from Colombia. Thirty-nine species and three genera, Espeletia (x = 19), Steiractinia (x = 14), and Vasquezia (x = 19), are reported for the first time. New base numbers or chromosome series are recorded in Baccharis (B. nitida, n = 25), Calea (C. caracasana, n = 24), and Liabum (L. mega-cephalum, n = 10).     

Crossing relationships and chromosome numbers of Nordic populations of Draba (Brassicaceae), with emphasis on the D. alpina complex

101 populations of Nordic Draba were investigated for chromosome numbers and crossing relationships. The populations were referred to 16 currently recognized species of Sect. Draba, Sect. Chrysodraba (including the D. alpina complex with D. alpina, D. oxycarpa, and D. corymbosa), and Sect. Drabella. The chromosome data suggest that all populations and species are homoploid. Three species are diploid, and 13 species are polyploids ranging from tetraploid to 16-ploid. Draba alpina is decaploid, D. oxycarpa is octoploid, and D. corymbosa is 16-ploid. The chromosome numbers of D. micropetala (n = 16,4x) and D. adamsii (n = 24,2n = 48, 6x) of Sect. Chrysodraba and D. cinerea (n = 24, 6x) of Sect. Draba were determined for the first time based on Nordic material. The relationships inferred from the crossing data largely agree with those inferred from previously published molecular data, but correspond poorly to relationships inferred from morphology. Inter-populational F₁ hybrids in D. fladnizensis were entirely sterile, suggesting that this predominantly inbreeding diploid species comprises at least two sibling species, possibly isolated by genic barriers. Sterile to semifertile F₁ hybrids with intermediate chromosome numbers were obtained in 19 interspecific combinations. F₂ hybrids were obtained in seven of these combinations. Both Sect. Chrysodraba and the D. alpina complex are probably polyphyletic. The crossing data suggest that the morphologically very similar polyploids D. alpina (10x) and D. oxycarpa (8x) do not have any diploid progenitors in common, and that Sect. Draba forms an intricate allopolyploid complex that also includes D. alpina and D. corymbosa of Sect. Chrysodraba. Draba corymbosa (16x) is probably an intersectional, polyphyletic alloploid derived from D. alpina (10x) and various hexaploids of Sect. Draba. Crossing data also suggest that D. norvegica (6x) is one of the progenitors of the Nordic endemic D. cacuminum (8x). The phenotypic expression of genes encoding taxonomically important indument characters did not follow consistent patterns in interspecific hybrids. This result may explain the discrepancy between genetic and taxonomic relationships in Nordic Draba, and supports the use of wide taxonomic concepts in this highly reticulate genus.     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

CHROMOSOMES AND SYSTEMATICS OF ASPLENIUM SECT. HYMENASPLENIUM (ASPLENIACEAE)

Gametic and somatic chromosome numbers of eight Asian species belonging to Asplenium sect. Hymenasplenium were determined. Seven species were observed to have chromosome numbers based on x = 39, and one on x = 38. These chromosome numbers are exceptional in Asplenium which is well known to have chromosomes of n = 36 or multiples thereof. Decisions on the taxonomic status of the species of section Hymenasplenium were facilitated by cytological observations. Systematic recognition of this section is also supported by the peculiarity in the chromosome numbers, and evidence for the addition to the section of several other species is presented.     

Effect of steam sterilization of soil on two desert plant species

Summary Franseria dumosa Gray and Hilaria rigida (Thurb.) Benth. ex Scribn. seedlings were grown in a glasshouse in potted soil which was collected from the Mojave Desert near Mercury, Nevada. The soil represented areas under living shrubs and also areas between shrubs. Soil was either steam sterilized or not steam sterilized. The sterilization resulted in greatly decreased yields of plants possibly because of induced P deficiency. It was suggested that symbiotic mycorrhizae necessary for P absorption for the species involved might have been eliminated by the sterilization. The effect did not hold for a noncalcareous soil well supplied with available P. Soil sterilization increased both Mn and Zn in plants. There was an interaction in that plants did not grow well in soil from under shrubs regardless of steaming indicating possible allelopathic effects. re]19720711     

CHROMOSOME NUMBERS IN PERITYLE AND RELATED GENERA (PERITYLANAE-COMPOSITAE)

Chromosome numbers are presented for 28 species of the genus Perityle, one putative inter-sectional hybrid, two species of Amauria, one species of Eutetras, and one species of Pericome. For Perityle, initial counts are recorded for 12 species of sect. Laphamia (n = 16, 17, 18, 36, ca. 102) and 11 species of sect. Perityle (n = 11, 12, 13, 16, 17, 18, 19, 34, 51). Chromosome numbers for the two species of Amauria (n = 18) are first reports for the genus. Including the current information, chromosome numbers have been recorded for 37 of the approximately 50 species recognized for Perityle. At least 24 taxa have numbers of n = 17, suggesting a base chromosome number of x = 17 for Perityle.     

Merged mechanisms for hydride transfer from 1,4-dihydronicotinamides

Recent work on the reduction of heteroaromatic cations by 1,4-dihydronicotinamides and related reducing agents is reviewed. Extensive correlations are presented between the second-order rate constants (k₂) for these reactions and the second-order rate constants (k_OH) and equilibrium constants (pK_R⁺) for hydroxide ion attack on these cations. Close correlations of log k₂ with the electron affinities and one-electron reduction potentials of these cations are also presented. These relationships are considered in the context of a direct hydride transfer from donor to acceptor and also in terms of SET mechanisms which are also commonly discussed for such reactions. It is shown that the interpretation of these formal hydride transfer reactions in terms of an imbalanced development of electronic charge and C---H bond fission within the transition state species leads to a rational merging of the single-step hydride transfer mechanism and the SET mechanisms. The structures of the transition state species are expected to be highly variable and quite dependent upon the nature of the hydride donor and acceptor species, with considerable contribution from charge-transfer interactions. Such imbalanced transition state species are analyzed in terms of two different types of reaction coordinate diagrams and also in terms of the valence bond configuration mixing theory.     

Chromosome numbers of miscellaneous Malagasy Acanthaceae

Meiotic chromosome numbers are reported for 12 species in eight genera of Acanthaceae from Madagascar. Chromosome numbers of 11 species are reported for the first time. Counts inMendoncia (n=19) andNeuracanthus (n=20) are the first for these genera. A new chromosome number (n=30) is reported inJusticia. Systematic implications of the chromosome counts are addressed and basic chromosome numbers for these eight genera of Malagasy Acanthaceae are discussed.     

CHROMOSOME NUMBERS AND THEIR SYSTEMATIC IMPLICATIONS IN HAWAIIAN LOBELIOIDEAE (CAMPANULACEAE)

Chromosome numbers are reported for 20 collections of Hawaiian Lobelioideae (Campanulaceae), representing six genera, 13 species, and two interspecific hybrids. All are n = 14. Chromosome numbers are reported for the first time for eight species of Clermontia, Cyanea, Delissea, Lobelia, and Trematolobelia; the report for Delissea is the first for that genus. Additional determinations confirmed previously reported numbers in five other species of Brighamia, Clermontia, and Cyanea. Chromosome numbers are now known for all seven genera and 20 of the 110 species. All accepted counts are n = 14. It is suggested that all Hawaiian Lobelioideae share this number and are paleotetraploid. There is no evidence that the prolific speciation evident among these plants was accompanied by euploid or aneuploid change in chromosome number. The Hawaiian Lobelioideae, particularly the monophyletic lineage of 91 baccate species, offer further support for the generalization that change in chromosome number is an uncommon mode of speciation in insular floras.     

Karyotype relationships among four South American species of Urvillea (Sapindaceae: Paullinieae)

A cytogenetic study was conducted on four species of the genus Urvillea (Sapindaceae, Paullinieae): U. chacoensis Hunz., U. filipes Radlk. and U. ulmacea Kunth of the Urvillea section and U. laevis Radlk. of the Stenelytron section. The chromosome numbers in U. chacoensis (2n = 22) and U. laevis (2n = 24) were confirmed, and new chromosome numbers are reported for U. filipes with 2n = 22 and U. ulmacea with 2n = 88. Additionally, data on interphase nuclear structure, chromosome banding patterns (C-Giemsa and C-CMA₃/DAPI) and FISH with rDNA probes are also presented. The distribution of AT- and GC-rich regions and the physical mapping of ribosomal genes (45S and 5S rDNA sites) were established for the first time in these Urvillea species. Sections of Urvillea are cytogenetically differentiated according to basic chromosome number, where x = 11 in the section Urvillea and x = 12 in the section Stenelytron. This first section displayed an important karyotypic feature, the occurrence of large AT- and GC-rich bands at terminal chromosomal regions. The Urvillea section showed polyploidy and its species were differentiated by their banding patterns. Urvillea chacoensis showed several terminal AT-rich bands, while terminal AT- and GC-rich bands were both found in U. ulmacea. However, the section Stenelytron did not exhibit this banding pattern. The 45S rDNA sites appeared always associated with GC-rich regions and they were numerically variable among species, being located or not the same chromosome 5S rDNA sites. Variation in the repetitive DNA distribution and their role in karyotype differentiation among these Urvillea species are discussed.