New endemic species of Aneilema and Commelina (Commelinaceae) from Somalia

Three new, endemic species of Commelinaceae from central and southern Somalia are described. Aneilema trispermum is unique in the genus in having capsules with three one-seeded locules. The annual, buff-orange-flowered Commelina arenicola differs from the annual C. subulata Roth and related perennials in having a capsule with an indehiscent dorsal locule. Commelina frutescens has a unique shrubby habit.     

Cytogenetic and molecular characterization of morphologically variable Sisyrinchium micranthum (Iridaceae) in southern Brazil

Sisyrinchium micranthum is native to southern Brazil and shows a wide range of morphological variation in this region. This study was performed to compare individuals of this species in terms of traits such as morphology, chromosome number, meiotic behaviour, pollen viability and genetic diversity using inter simple sequence repeat markers. First, general morphological aspects were evaluated and plants were classified into three morphological categories (CI, CII and CIII) to analyse the cytogenetic and genetic data. Three chromosome numbers corresponding to three ploidies were found: 2n = 2x = 16, 2n = 4x = 32 and 2n = 6x = 48. All morphological types showed regular meiotic behaviour and high meiotic index values and pollen viability. CII is the most frequent in southern Brazil. The most common haploid chromosome number, n = 8, has not been reported previously in this species. The percentage of polymorphic loci ranged from 6.45 to 61.29% for each accession. Molecular and cytogenetic analyses indicate that some S. micranthum accessions may have more than one ploidy. This study represents the first effort to characterize this taxonomically complex species based on cytogenetic and genetic aspects. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 350–364.     

Chromosomes of four species in three genera of Commelinaceae from China and their systematic implications

Chromosomes of four species in three genera of Commelinaceae from China were examined. Spatholirion longifolium had 2 n  = 20. This small genus is considered to be of a possible polyploid origin based on x  = 5, a basic number shared by its closest ally, the monospecific genus Streptolirion , with its only species having 2 n  = 10. The two genera were found to be very different from each other in their karyotypic constitution. The differences in both chromosome number (2 n  = 20 vs. 10) and karyotypic constitution support their separation as two independent genera. The remaining three species, Amischotolype hispida , Porandra ramosa and P. scandens , all had 2 n  = 36. In view of the occasional occurrence of 2 n  = 18 in the African Coleotrype , a genus very close to Amischotolype and Porandra in gross morphology, these three species are all very probably polyploid based on x  = 9. The high degree of karyotypic similarity of the three genera also strongly indicates their close affinity and supports their placement in the subtribe Coleotrypinae. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 399–403.     

Chromosome counts and genome size of Leontopodium species (Asteraceae: Gnaphalieae) from south‐western China

Chromosome counts and genome sizes are reported from six species of Leontopodium: five from the centre of diversity in south‐western China, and L. japonicum from cultivation. Previously published chromosome counts for the genus are also compiled. Genome size (1C) in diploids ranges from 0.93 pg (L. dedeckensii) to 1.14 pg (L. cf. stracheyi) and 1.93 pg for tetraploid L. sinense. Leontopodium artemisiifolium had one pair of heteromorphic chromosomes. Leontopodium japonicum accessions showed variation in ploidy levels. Polyploidy, including autopolyploidy, is frequent in the genus. Variation is seen in basic chromosome number, including between species in the centre of diversity of the genus, where x = 12 or 13, but also within species among previously published counts. This variation does not correspond to currently inferred infrageneric groupings, and indicates both the importance of large‐scale chromosome evolution and the need for more in‐depth taxonomic work in a genus that shows little DNA sequence variation. © 2013 The Linnean Society of London     

The cytology of the genus Alopecurus (Gramineae)

For a study of hybridization in Alopecurus , chromosome numbers, karyotypes, meiotic chromosome behaviour and breeding systems have been investigated in six species. In addition to confirming many previous chromosome numbers, new triploid and tetraploid counts have been found in A. bulbosus , which have not previously been reported. The karyotypes of all species have a very similar morphology but there are differences in chromosome size which can be related to differences in nuclear DNA content. At meiosis the diploid species form bivalents, but one population of A. aequalis contains plants that regularly form a single quadrivalent which would appear to be interchange heterozygotes. The meiotic behaviour of the tetraploids suggests that A. pratensis is an allotetraploid and A. geniculatus an autotetraploid. All species appear to be allogamous, although some, such as A. myosuroides are obligate outbreeders resulting from the presence of a self-incompatibility system, outbreeding is promoted in others by differences in the time of maturity of stigmas and anthers.     

Chromosomes and polyploidy in Lenophyllum (Crassulaceae)

Gametic chromosome numbers of 22, 32, 33, and 44 in five species of Lenophyllum suggest that they may be polyploids on a basic 11, but this number has not been found. Three species have 8-12 distinctively large chromosomes that do not pair with each other in their hybrids and probably belong to the same genome. In hybrids of many polyploid Mexican Crassulaceae preferential pairing occurs between corresponding chromosomes of their multiple genomes, which indicates that they are autopolyploids. However, little or no preferential pairing occurs between chromosomes of Lenophyllum in its hybrids, and its species appear to be allopolyploids. The putative parents are unknown.     

Cytotaxonomy of Commelinaceae: chromosome numbers of some African and Asiatic species

Chromosome counts are reported for 32 taxa (31 species and 1 subspecies) belonging to 10 genera of Commelinaceae from seven African and Asiatic countries. Counts for 13 species and 1 subspecies are recorded for the first time. Published chromosome numbers for Anhicopsis and Polyspatha are confirmed. It is suggested that Pdisota, Pollia and Stanfieldidla each has a single basic number (x = 20, 16 and 11, respectively). The known cytological diversity in Floscopa is extended. The third continental African species of Coleolrype is found to have the same chromosome number (2n = 36) as the other two. The preponderance of the basic number x = 15 in Commelina is supported. The uncommon basic number x = 13 is reported in four taxa of Cyanotis together with karyotypic differences. The basic number x = 6 is found in a second species of Murdannia . Karyotypic data in addition to chromosome numbers are presented for 24 of the 32 taxa investigated. Karyotypes are found to be useful in assessing relationships in the family, and evolutionary trends in the karyotype are noted.     

Colored floral organs influence pollinator behavior and pollen transfer in Commelina communis (Commelinaceae)

Visual floral guides such as colored anthers, lines, dots, and UV-absorption patterns on petals are commonly observed in insect-pollinated angiosperms. Floral guides that are known to enhance foraging efficiency of visitors on flowers thus promote return visits (foraging facilitation hypothesis, which predicts that visitors will discriminate against flowers with inferior floral guides). In this study, we experimentally examined the hypothesis that floral guides also prevent pollen-theft behavior by floral visitors (theft prevention hypothesis), which has rarely been tested. Nectarless flowers of Commelina communis have three types of brightly colored floral organs: large blue petals, rewarding yellow anthers, and nonrewarding yellow anthers. Colored floral organs were removed artificially from plants in two natural populations of C. communis. Removal of the nonrewarding yellow anthers diminished hoverings in front of flowers and tended to reduce the number of total floral visitor landings, supporting the foraging facilitation hypothesis. Additionally, removal of the rewarding yellow anther decreased the frequency of legitimate landings on flowers and the legitimate landing-to-total landing ratio, which is consistent with the theft prevention hypothesis. The nonrewarding anthers and the rewarding yellow anthers were shown to play an important role in increasing visitor landings and orienting floral visitors toward a landing point appropriate for pollination, respectively. We also showed that the absence of yellow anthers decreased both pollen dispatch from brown anthers and receipt by stigmas in C. communis. These findings support both the foraging facilitation hypothesis and the theft prevention hypothesis.     

Cytomorphological study of Scutellaria platystegia (Lamiaceae) in Iran

Chromosome number, meiotic behaviour and morphological characters related to habit were studied in 10 populations of Scutellaria platystegia Juz. from S. sect. Lupulinaria native to Iran. All populations are diploid and has the chromosome number 2n = 2x = 22, which is consistent with the proposed base number of x = 11. This taxon displayed regular bivalent pairing and chromosome segregation at meiosis. However, some meiotic abnormalities observed included various degrees of fragmented chromosomes, laggards and bridges in anaphase I to telophase II, precocious division of centromeres in metaphase I or II, asynchronous nucleus and cytomixis. We evaluated and determined the population limits within S. platystegia, employing multivariant statistics. We found a striking association between meiotic behaviour and gross morphology. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cytogenetic studies on Brazilian Xyris species (Xyridaceae)

Cytological features are presented for the first time for 12 species and one natural hybrid from 16 Brazilian populations of the genus Xyris , including members of two sections ( Xyris and Nematopus ). The results are compared with a review of all available chromosome numbers previously reported for the genus. All analysed species show semi-reticulate interphase nuclei and prophase to prometaphase chromosomes with heterogeneous condensing behaviour. Chromosome numbers varied between 2 n = 26 and 2 n ≈ 108. In Brazil especially, the karyological differentiation of Xyris seems to be generally characterized by dysploid and polyploid increase of the chromosome number, possibly after interspecific hybridization. This is the first cytological study including species of the section Nematopus and the first karyological investigation including South American species of the genus Xyris . © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 138 , 245–252.     

Autosomal polyploidy and male meiotic pattern in the bug family Nabidae (Heteroptera)

Karyotypes of 18 species of Nabidae (Heteroptera), belonging to the genera Nabis (11), Himacerus (3), Hoplistoscelis (1), and Pagasa (1) were studied. The data on Nabis meridionalis Kerzhner 1963, N. tesquorum (Kerzhner 1968), N. ussuriensis (Kerzhner 1962), N. pallidus Fieber 1861, N. sareptanus Dohrn 1862, Hoplistoscelis sordidus (Reuter 1872), and Pagasa fusca (Stein 1857) were obtained for the first time in this study. Karyotypes of Nabis punctatus A. Costa 1847, N. ferus (Linnaeus 1758), N. pseudoferus Remane 1949, N. rugosus (Linnaeus 1758), N. stenoferus Hsiao 1964, N. limbatus Dahlbom 1851, N. reuteri Jakovlev 1876, N. flavomarginatus Scholtz 1847, Himacerus apterus (Fabricius 1798), H. mirmicoides (O. Costa 1834), and H. maracandicus (Reuter 1890) were re-examined. A karyotype of 2n = 18 (16 + XY), which seems to be the most characteristic of Nabidae as a whole, was found in 12 species. Nabis pallidus and N. sareptanus showed a precise numerical doubling of the autosomal complement compared with the modal karyotype, 2n = 34 (32 + XY). Autosomal polyploidy is discussed as a possible evolutionary mechanism for these species. Meiosis in males of the above species was studied in detail. Male meiosis in Nabidae was shown to follow a highly peculiar scenario differing in many aspects from that known in the majority of the Heteroptera taxa.     

国产蜘蛛抱蛋属的细胞分类学研究I.四个广西特有种的核型

研究了广西特有的４种蜘蛛抱蛋属植物的核型,结果如下：巨型蜘蛛抱蛋,２ｎ＝３８＝２４ｍ（２ｓａｔ）＋２ｓｍ＋１２ｓｔ;长药蜘蛛抱蛋,２ｎ＝３６＝１８ｍ＋２ｓｍ（２ｓａｔ）＋１６ｓｔ;广西蜘蛛抱蛋,２ｎ＝３６＝１８ｍ＋４ｓｍ（２ｓａｔ）＋１４ｓｔ,隆安蜘蛛抱蛋,２ｎ＝３８＝２０ｍ＋６ｓｍ（２ｓａｔ）＋１２ｓｔ。以上核型都属２Ｃ,具有明显的二型性．     

Genome size stability across Eurasian Chenopodium species (Amaranthaceae)

Tremendous interspecific genome size variation is a well known phenomenon, whereas genome size within a species is supposed to be exceptionally stable and thus useful as a taxonomic trait. Using DAPI flow cytometry, we tested the stability of genome size in various representatives of Chenopodium s.s. (Amaranthaceae) across a broad geographical range (from Portugal to eastern Russia) in Eurasia. We sampled 1977 Chenopodium individuals of four different ploidies (di‐, tetra‐, hexa‐ and decaploids) from 347 populations. Intraspecific relative genome size variation was low, ranging from 2.0% in C. probstii to 7.7% in C. album, even in the species with broad distributions. We distinguished 12 homogeneous relative genome size groups among the 17 Chenopodium spp. tested. Genome size is useful for distinguishing certain morphologically similar groups of species such as C. suecicum/C. album, C. vulvaria/C. pamiricum–C. iljinii/C. sosnowskyi/C. karoi. Due to its genome size stability, the cosmopolitan species C. album can be used as an alternative internal standard in flow‐cytometric analyses with the additional advantages of annual life cycle, self‐compatibility and common occurrence all over the world. Finally, we did not detect any sign of hybridization between Chenopodium spp. of different ploidies.     

The chromosomes of Cepaea vindobonensis (Pulmonata: Helicidae) and the relationship between this species and the rest of the genus

The karyotype of Cepaea vindobonensis (Pfeiffer) (2 n = 50) is defined and compared with those of C. sylvatica (Draparnaud), C. nemoralis (L.) and C. hortensis (Müller). Cepaea vindobonesis shares its chromosome number with C. sylvatica. The genus Cepaea thus consists of two pairs of species, one with 2 n = 50 the other with 2 n = 44. The karyotype of C. vindobonensis is distinct from that of C. sylvatica as it lacks any discontinuity in its range of chromosome length and has all three of its longest chromosome pairs nearly identical. The two 2 n = 50 species both have an unusual meiotic bivalent showing a 'satellite-type' structure. It is apparent that the 2 n = 50 species are more closely related to each other than to the 2 n = 44 species. No precise definition of the evolutionary history can be given but a working hypothesis is suggested.     

Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae)

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.     

Karyotype analysis of the southernmost South American species of Stemodia (Scrophulariaceae)

Abstract

The aim of the present study was to examine the somatic chromosomes of seven species of Stemodia (Scrophulariaceae). The karyotypes of Stemodia ericifolia (2n = 22 = 20m + 2 sm), S. hassleriana (2n = 22 = 20m + 2sm), S. hyptoides (2n = 22 = 20m + 2sm), S. hyptoides (2n = 44 = 40m + 4sm), S. lobelioides (2n = 44 = 40m + 4sm) and S. stricta (2n = 22 = 20m + 2sm) were analyzed for the first time. All the species studied showed a predominance of metacentric chromosomes and a lower proportion of submetacentric pairs. The chromosomes in all the species were found to be small with a mean chromosome length of 1.42 μm, varying from 0.77 μm in S. hyptoides (2n = 66) to 2.10 μm in S. lanceolata. The differences in the asymmetry of the karyotypes were small, for which it is possible to assume that the great diversification of the genus has been accompanied by very small changes in the structure of the chromosomes.