Contributions to the cytotaxonomy of the Commelinaceae*

Further material of Gibasis geniculata (Jacq.) Rohw. (syn. Tradescantia geniculata Jacq.) and other Gibasis species collected in the field has been studied. The existence of several species in our earlier experimental material is confirmed. These include G. geniculata itself (2n= 32 or 48 small chromosomes), G. oaxacana D. R. Hunt (2n= 16 small chromosomes) and G. schiedeana (Kunth) D. R. Hunt, which has two chromosome forms, 2n= 10 and 2n= 16, both with large chromosomes. These forms are diploid and tetraploid based on x= 5 and x= 4 respectively and show a Robertsonian relationship with each other. The cytology of tetraploid (2n= 20) G. karwinskyana is confirmed and that of a diploid form (2n=10) described. The recently described G. consobrina D. R. Hunt (2n= 20) is shown to be cytologically comparable with G. karwinskyana, but to differ in significant details. Next, the cytology of G. pulchella (Kunth) Rafin., the type species of Gibasis, is described and also that of the allied G. matudae D. R. Hunt. Both G. pulchella (2n= 10, 15) and G. matudae (2n= 10) show interchange heterozygosity, with complete rings of ten chromosomes at meiosis in some plants of G. pulchella. Preliminary comments are made on the cytology of G. aguensis (Standl. & Steyerm.) Rohw. (2n= 10), another ally of G. pulchella, and on the G. linearis group, where the basic number appears to be x= 6 but two karyotype patterns have been found. A discussion of chromosome architecture in Gibasis in relation to the taxonomy of the genus concludes the paper.     

Evaluation of Asteraceae Plants for Control of Meloidogyne incognita

Of the 56 species and 43 genera of Asteraceae tested, 9 were highly resistant or immune to Meloidogyne incognita and did not form root galls. Twenty-six species and six cultivars had 25% or fewer roots galled and were considered moderately resistant to M. incognita. Pre-planting Cosmos bipinnatus (F190), Gaillardia pulchella, Tagetes erecta, Tithonia diversifolia, or Zinnia elegans (F645) reduced root galling and M. incognita J2 in and around Ipomoea reptans. Amendment of soils with roots, stems, or leaves of G. pulchella was effective in controlling M. incognita on I. reptans. Tissue extracts of G. pulchella were lethal to various plant-parasitic nematodes but were innocuous to free-living nematodes. Root exudates of G. pulchella were lethal to J2 of M. incognita and were inhibitory to the hatch of eggs at the concentration of 250 ppm or higher. Gaillardia pulchella could be used to manage M. incognita as a rotation crop, a co-planted crop, or a soil amendment for control of root-knot nematode.     

Karyotypes,heterochromatin distribution and rDNA patterns in South American Grindelia (Asteraceae)

Grindelia is a genus with a complex evolutionary history with reticulate evolution. We studied the karyotype, fluorescent banding, and fluorescence in situ hybridization (FISH) using 18–5.8–26 S and 5 S ribosomal DNA probes to survey karyotypic diversity of South American Grindelia species. Chromosome basic numbers were x = 6 (with several ploidy levels: 2x, 4x, and 6x). All the Grindelia studied conserved the patterns of CG-rich heterochromatin and 18-5.8-26 S rDNA. The third m sat-chromosome pair was homeologous in Grindelia. Chromosome variation, although not always large, accompanied the evolutionary divergence of the taxa studied. The Grindelia studied formed two species groups: (1) G. globularifolia and G. pulchella var. pulchella, (2) G. buphthalmoides, G. cabrerae var. alatocarpa and var. cabrerae, G. chiloensis, G. orientalis, and G. prostrata. These groups do not show any morphological affinities and their phylogenetic relationships are not clearly resolved, suggesting that these groups have recently diverged.     

The biogeography of Gunnera L.: vicariance and dispersal

Aim The genus Gunnera is distributed in South America, Africa and the Australasian region, a few species reaching Hawaii and southern Mexico in the North. A cladogram was used to (1) discuss the biogeography of Gunnera and (2) subsequently compare this biogeographical pattern with the geological history of continents and the patterns reported for other Southern Hemisphere organisms. Location Africa, northern South America, southern South America, Tasmania, New Zealand, New Guinea/Malaya, Hawaii, North America, Antarctica. Methods A phylogenetic analysis of twenty‐six species of Gunnera combining morphological characters and new as well as published sequences of the ITS region, rbcL and the rps16 intron, was used to interpret the biogeographical patterns in Gunnera. Vicariance was applied in the first place and dispersal was only assumed as a second best explanation. Results The Uruguayan/Brazilian Gunnera herteri Osten (subgenus Ostenigunnera Mattfeld) is sister to the rest of the genus, followed sequentially upwards by the African G. perpensa L. (subgenus Gunnera), in turn sister to all other, American and Australasian, species. These are divided into two clades, one containing American/Hawaiian species, the other containing all Australasian species. Within the Australasian clade, G. macrophylla Blume (subgenus Pseudogunnera Schindler), occurring in New Guinea and Malaya, is sister to a clade including the species from New Zealand and Tasmania (subgenus Milligania Schindler). The southern South American subgenus Misandra Schindler is sister to a clade containing the remaining American, as well as the Hawaiian species (subgenus Panke Schindler). Within subgenus Panke, G. mexicana Brandegee, the only North American species in the genus, is sister to a clade wherein the Hawaiian species are basal to all south and central American taxa. Main conclusions According to the cladogram, South America appears in two places, suggesting an historical explanation for northern South America to be separate from southern South America. Following a well‐known biogeographical pattern of vicariance, Africa is the sister area to the combined southern South America/Australasian clade. Within the Australasian clade, New Zealand is more closely related to New Guinea/Malaya than to southern South America, a pattern found in other plant cladograms, contradictory to some of the patterns supported by animal clades and by the geological hypothesis, respectively. The position of the Tasmanian G. cordifolia, nested within the New Zealand clade indicates dispersal of this species to Tasmania. The position of G. mexicana, the only North American species, as sister to the remaining species of subgenus Panke together with the subsequent sister relation between Hawaii and southern South America, may reflect a North American origin of Panke and a recolonization of South America from the north. This is in agreement with the early North American fossil record of Gunnera and the apparent young age of the South American clade.     

Comparison of the Z and W sex chromosomal architectures in elegant crested tinamou (<Emphasis Type="Italic">Eudromia elegans</Emphasis>) and ostrich (<Emphasis Type="Italic">Struthio camelus</Emphasis>) and the process of sex chromosome differentiation in palaeognathous birds

To clarify the process of avian sex chromosome differentiation in palaeognathous birds, we performed molecular and cytogenetic characterization of W chromosome-specific repetitive DNA sequences for elegant crested tinamou (Eudromia elegans, Tinamiformes) and constructed comparative cytogenetic maps of the Z and W chromosomes with nine chicken Z-linked gene homologues for E. elegans and ostrich (Struthio camelus, Struthioniformes). A novel family of W-specific repetitive sequences isolated from E. elegans was found to be composed of guanine- and cytosine-rich 293-bp elements that were tandemly arrayed in the genome as satellite DNA. No nucleotide sequence homologies were found for the Struthioniformes and neognathous birds. The comparative cytogenetic maps of the Z and W chromosomes of E. elegans and S. camelus revealed that there are partial deletions in the proximal regions of the W chromosomes in the two species, and the W chromosome is more differentiated in E. elegans than in S. camelus. These results suggest that a deletion firstly occurred in the proximal region close to the centromere of the acrocentric proto-W chromosome and advanced toward the distal region. In E. elegans, the W-specific repeated sequence elements were amplified site-specifically after deletion of a large part of the W chromosome occurred.     

The invasive worm Hydroides elegans (Polychaeta – Serpulidae) in southeastern Brazil and its potential to dominate hard substrata

The serpulid Hydroides elegans is recognized as an invasive species in many harbour areas of the world, growing mainly on man-made structures such as pier pilings, where native diversity is low. In addition, because they build large aggregations of calcareous tubes, this increases the maintenance and fuel costs of vessels. While H. elegans is well known for the North Atlantic, Europe, Caribbean and Pacific Ocean, detailed information of the species for the South Atlantic is missing. In the last decade, owners of boats moored at the Clube Naval Charitas (CNC), in the Guanabara Bay, southeastern Brazil noticed an increase in the occurrence of an encrusting organism that we identified as H. elegans. In this study we characterize H. elegans specimens from CNC and Itaguaí Harbor, both in southeastern Brazil, and discuss its distribution in the world. In addition, we deployed PVC panels at two different depths to quantify how H. elegans affects community assembling over two months. We observed that H. elegans could dominate hard substrata in the intertidal zone, occupying more than 50% of the available substrata. Considering the damage caused by H. elegans elsewhere and the ability of the species to monopolize space in the intertidal zone demonstrated here, accurate taxonomic information is essential for future monitoring and management of the species in Brazil and the South Atlantic.     

Geographic variation in South American populations of Myotis nigricans () (Chiroptera, Vespertilionidae), with the description of two new species

The genus Myotis (Vespertilionidae, Myotinae) comprises a diverse group of small to large-sized vespertilionid bats that present a worldwide distribution. Twelve South American species are currently recognized. In this paper we evaluate the morphological and morphometric variation observed in South American populations of the most widespread species, Myotis nigricans. Against this background, two forms can be morphologically distinguished from M. nigricans and other known South American species. We describe these new species, documenting their diagnostic external and cranial characters by comparing them to other sympatric and cryptic species of South American Myotis. In addition, we provide an emended diagnosis of Myotis nigricans.     

Diverse stages of sex-chromosome differentiation in tinamid birds: evidence from crossover analysis in <Emphasis Type="Italic">Eudromia elegans</Emphasis> and <Emphasis Type="Italic">Crypturellus tataupa</Emphasis>

All extant birds share the same sex-chromosome system: ZZ males and ZW females with striking differences in the stages of sex-chromosome differentiation between the primitive palaeognathus ratites and the large majority of avian species grouped within neognaths. Evolutionarily close to ratites is the neotropical order Tinamiformes that has been scarcely explored regarding their ZW pair morphology and constitution. Tinamous, when compared to ratites, constitute a large group among Palaeognathae, therefore, exploring the extent of homology between the Z and W chromosomes in this group might reveal key features on the evolution of the avian sex chromosomes. We mapped MLH1 foci that are crossover markers on pachytene bivalents to determine the size and localization of the homologous region shared by the Z and W chromosomes in two tinamous: Eudromia elegans and Crypturellus tataupa. We found that the homologous (pseudoautosomal) region differ significantly in size between these two species. They both have a single recombination event on the long arm of the acrocentric Z and W chromosomes. However, in E. elegans the pseudoautosomal region occupies one-fourth of the W chromosome, while in C. tataupa it is restricted to the tip of the long arm of the W. The W chromosomes in these two species differ in their heterochromatin content: in E. elegans it shows a terminal euchromatic segment and in C. tataupa is completely heterochromatic. These results show that tinamous have ZW pairs with more diversified stages of differentiation compared to ratites. Finally, the idea that the avian proto-sex chromosomes started to diverge from the end of the long arm towards the centromere of an acrocentric pair is discussed.     

THE ROLE OF INTROGRESSIVE HYBRIDIZATION IN THE EVOLUTION OF THE GILA ROBUSTA COMPLEX (TELEOSTEI: CYPRINIDAE)

Abstract The extent and impact of introgressive hybridization was examined in the Gila robusta complex of cyprinid fishes using mitochondrial DNA (mtDNA) sequence variation. Lower Colorado River basin populations of G. robusta, G. elegans, and G. cypha exhibited distinct mtDNAs, with only limited introgression of G. elegans into G. cypha. The impact of hybridization was significant in upper Colorado River basin populations; most upper basin fishes sampled exhibited only G. cypha mtDNA haplotypes, with some individuals exhibiting mtDNA from G. elegans. The complete absence of G. robusta mtDNA, even in populations of morphologically pure G. robusta, indicates extensive introgression that predates human influence. Analysis of the geographic distribution of variation identified two distinctive G. elegans lineages; however, the small number of individuals and localities sampled precluded a comprehensive analysis. Analysis of haplotype and population networks for G. cypha mtDNAs from 15 localities revealed low divergence among haplotypes; however, significant frequency differences among populations within and among drainages were found, largely attributable to samples in the Little Colorado River region. This structure was not associated with G. cypha and G. robusta, as morphotypes from the same location are more similar than conspecific forms in other locations. This indicates that morphological and mtDNA variation are affected by different evolutionary forces in Colorado River Gila and illustrates how both hybridization and local adaptation can play important roles in evolution.     

Strong nucleosomes reside in meiotic centromeres of C. elegans

Recently discovered strong nucleosomes (SNs) are characterized by strongly periodical DNA sequence, with visible rather than hidden sequence periodicity. In a quest for possible functions of the SNs, it has been found that the SNs concentrate within centromere regions of A. thaliana chromosomes . They, however, have been detected in Caenorhabditis elegans as well, although the holocentric chromosomes of this species do not have centromeres. Scrutinizing the SNs of C. elegans and their distributions along the DNA sequences of the chromosomes, we have discovered that the SNs are located mainly at the ends of the chromosomes of C. elegans. This suggests that, perhaps, the ends of the chromosomes fulfill some function(s) of centromeres in this species, as also indicated by the cytogenetic studies on meiotic chromosomes in spermatocytes of C. elegans, where the end-to-end association is observed. The centromeric involvement of the SNs, also found in A. thaliana, opens new horizons for the chromosome and centromere structure studies.     

Karyotype evolution in South American species of Hypochaeris (Asteraceae, Lactuceae)

The genus Hypochaeris (Asteraceae, Lactuceae) contains ten species in Europe, three in Asia, and approximately 50 in South America. Previous cytotaxonomic studies have shown two groups of taxa: (1) European species with different basic chromosome numbers and differentiated karyotypes, and (2) South American species with x=4 and uniform asymmetric and bimodal karyotypes. Karyotypic data are synthesized for South American species of Hypochaeris with new information for six Chilean species: H. acaulis, H. apargioides, H. palustris, H. spathulata, H. tenuifolia and H. thrincioides. Four main groups can be distinguished based on presence and localization of secondary constrictions – SCs (bearing Nucleolar Organizer Regions – NORs) on chromosomes 2 and 3, and 18S–25S and 5S rDNA loci number, localization, and activity. We propose karyotypic evolution of South American Hypochaeris (x=4) from H. maculata-like (x=5) European ancestors. The original South American karyotype would have possessed two SCs, one on the long arm of chromosome 2, and the other on the short arm of chromosome 3 (in terminal position). Further evolution would have involved inversion within the short arm of chromosome 3 and inactivation/loss of the SC on chromosome 2.     

BIOSYSTEMATICS OF THE BOTHRIOCHLOA BARBINODIS COMPLEX (GRAMINEAE)

The New World species of Bothriochloa O. Kuntze are polyploids with 2n = 60, 120, 180 and 220 chromosomes and they reproduce sexually. Plants with 2n = 180 chromosomes constitute the extremely variable B. barbinodis (Lag.) Herter, which is subdivided into var. barbinodis, var. palmeri (Hack.) de Wet comb. nov., and var. schlumbergeri (Fourn.) de Wet comb. nov. The single collection with 2n = 220 chromosomes belongs with var. schlumbergeri. Plants resembling B. barbinodis in inflorescence structure but having well-developed pedicellate spikelets and 2n = 120 chromosomes are included in B. campii (Swallen) de Wet comb. nov. South American collections of B. springfieldii (Gould) Parodi differ from North American collections in having 2n = 60 rather than 120 chromosomes and in having larger inflorescences as does B. barbinodis. Variety australis de Wet. var. nov. is described to include them.     

Chromosomal characterization of two species of genus <Emphasis Type="Italic">Steatogenys</Emphasis> (Gymnotiformes: Rhamphichthyoidea: Steatogenini) from the Amazon basin: sex chromosomes and correlations with Gymnotiformes phylogeny

Gymnotiformes are an important component of the Neotropical ichthyofauna and they are known for their ability to generate and detect electrical discharges. Phylogenetic relationships of Gymnotiformes are still not well understood. However, the monophyly of the superfamily Rhamphichthyoidea is well accepted, despite the position of tribe Steatogenini (Steatogenys, Hypopygus and Stegostenopos) within this superfamily is unclear. The genus Steatogenys includes three species that, together with Hypopygus and Stegostenopos, form tribe Steatogenini. Cytogenetic information is currently only available for Hypopygus lepturus. Here, we describe the karyotypes of Steatogenys elegans from four localities and S. duidae from two localities. S. elegans was found to have 2n = 50, ZZ/ZW (12m-sm/38st-a), while S. duidae had 2n = 50 (50m-sm). In S. elegans, constitutive heterochromatin (CH) was observed in the centromeric regions of all chromosomes, in the interstitial region of 1q, and in two blocks of Wq. In S. duidae, CH was observed in the centromeric and pericentromeric regions of all chromosomes, and in the interstitial regions of 2q, 3q, 5q, and 7q. Nucleolar organizer regions (NORs) were identified in the distal regions of one chromosome pair in each species. The CMA₃ fluorochrome (specific to G-C rich regions) coincided with the NORs in both species, and with the HC of S. elegans except on chromosome pair 5 and the W. The DAPI fluorochrome (specific to A-T rich regions) coincided with the CH of both species, and was very intense for chromosome pair 5 and the W of S. elegans. Our observations suggest that the ZZ/ZW system observed in S. elegans likely evolved through CH addition followed by a paracentric inversion. The chromosomal data described herein are consistent with the phylogenetic hypothesis that tribe Steatogenini should be positioned within family Ramphychthyidae.     

Biology, host specificity and risk assessment ofGargaphia decoris, the first agent to bereleased in South Africa for the biological control ofthe invasive tree Solanum mauritianum

The South American tree Solanummauritianum is a major environmental weed in thehigh-rainfall regions of South Africa and has beentargeted for biological control since 1984. Althoughhost ranges of imported agents determined duringquarantine tests have resulted in the rejection ofeight of the 11 candidate agents tested so far, theleaf-sucking lace bug Gargaphia decoris,imported from Argentina in 1995, displayed anacceptably narrow host range in captivity. No-choicetests showed that G. decoris is confined to Solanum species and cannot survive on solanaceouscrops outside that genus. Although these tests alsoindicated that G. decoris colonies could surviveand reproduce on cultivated eggplant (aubergine) andat least five native South African Solanumspecies, all but one native species proved to beinferior hosts in terms of adult survival andoviposition potential. During paired choice andmultichoice tests in small and larger cagesrespectively, G. decoris displayed very strongfeeding and oviposition preferences for S. mauritianum. Analyses of the risk of attack onnon-target Solanum plants revealed that, withone possible exception, none were likely to suffermore than incidental damage in the field. Host recordsfrom South America have also indicated that G. decoris has not been recorded on any Solanumspecies other than S. mauritianum, providingfurther evidence of its host specificity. The resultsof this study were accepted by the regulatoryauthorities and in February 1999, G. decorisbecame the first agent to be released in South Africafor the biological control of S. mauritianum.     

PHYLOGENETIC ANALYSIS OF EUDORINA SPECIES (VOLVOCACEAE,CHLOROPHYTA) BASED ON rbcL GENE SEQUENCES1

Species and varieties in the genus Eudorina Ehrenberg (Volvocaceae, Chlorophyta) were evaluated on the basis of phylogenetic analyses of the large subunit ofribulose-1,5-bis-phosphate carboxylase/oxygenase (rbcL) gene sequences from 14 strains of four Eudorina species, as well as from nine species of Pleodorina and Volvox. The sequence data suggested that 10 of the 14 Eudorina strains form three separate and robust monophyletic groups within the nonmonophyletic genus Eudorina. The first group comprises all three strains of E. unicocca G. M. Smith; the second group consists of one of the E. elegans Ehrenberg var. elegans strains, the E. cylindrica Korshikov strain, and both E. illinoisensis (Kofoid) Pascher strains; and the third group consists of two monoecious varieties of E. elegans [two strains of E. elegans var. synoica Goldstein and one strain of E. elegans var. carteri (G. M. Smith) Goldstein]. In addition, E. illinoisensis represents a poly- or paraphyletic species within the second group. The remaining four strains, all of which are assigned to E. elegans var. elegans, are nonmonophyletic. Although their position in the phylogenetic trees is more or less ambiguous, they are ancestral to other taxa in the large anisogamous/oogamous monophyletic group including Eudorina, Pleodorina, and Volvox (except for sect. Volvox). Thus, the four Eudorina groups resolved in the present molecular phylogeny do not correspond with the species concepts of Eudorina based on vegetative morphology, but they do reflect the results of the previous intercrossing experiments and modes of monoecious and dioecious sexual reproduction.     

A tale of North and South America: time and mode of dispersal of the amphitropical genus Munroa (Poaceae,Chloridoideae)

Plant disjunctions have provided some of the most intriguing distribution patterns historically addressed by biogeographers. We evaluated the three hypotheses that have been postulated to explain these patterns [vicariance, stepping‐stone dispersal and long‐distance dispersal (LDD)] using Munroa, an American genus of grasses with six species and a disjunct distribution between the desert regions of North and South America. The ages of clades, cytology, ancestral characters and areas of distribution were investigated in order to establish relationships among species, to determine the time of divergence of the genus and its main lineages, and to understand further the biogeographical and evolutionary history of this genus. Bayesian inference recovered the North American M. pulchella as sister species to the rest. Molecular dating and ancestral area analyses suggest that Munroa originated in North America in the late Miocene–Pliocene (7.2 Mya; 8.2–6.5 Mya). Based on these results, we postulate that two dispersal events modelled the current distribution patterns of Munroa: the first from North to South America (7.2 Mya; 8.2–6.5 Mya) and the second (1.8 Mya; 2–0.8 Mya) from South to North America. Arid conditions of the late Miocene–Pliocene in the Neogene and Quaternary climatic oscillations in North America and South America were probably advantageous for the establishment of populations of Munroa. We did not find any relationship between ploidy and dispersal events, and our ancestral character analyses suggest that shifts associated with dispersal and seedling establishment, such as habit, reproductive system, disarticulation of rachilla, and shape and texture of the glume, have been important in these species reaching new areas. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 110–125.     

Chromosome Divergences Among American Marsupials and the Australian Affinities of the American Dromiciops

To investigate the phylogenetic relationships of living marsupials, morphometric and G-banded chromosome analyses were made in the Chilean species Dromiciops gliroides (Microbiotheria) and Thylamys elegans (Didelphimorphia). Chromosome arm lengths and patterns of G-bands were compared in at least eight bone marrow metaphase spreads in six and nine specimens, respectively. They were contrasted with those published for another 11 American and Australian genera. Three of six autosomal pairs (A1, A3, and C2) were uniquely shared by Dromiciops and some Australian species, being different in shape and G-banded patterns from those with similar total sizes in Thylamys and other South American didelphoid karyotypes. Such chromosomal correspondences suggest the past occurrence of at least three pericentric inversions. A table of character states constructed from chromosomal G-band comparisons is presented, showing that cytogenetic data agree with Szalay's (1982) hypothesis on the affinities of the South American Dromiciops with Australian marsupials.     

A Sarcocystid Misidentified as Hepatozoon didelphydis: Molecular Data from a Parasitic Infection in the Blood of the Southern Mouse Opossum (Thylamys elegans) from Chile

ABSTRACT. The blood of 21 adult South American mouse opossums (Thylamys elegans) captured from April through August of 2005 in central Chile was examined for parasites. Light microscopic analysis of blood smears initially suggested that a highly pleomorphic Hepatozoon species typical of American opossums was infecting erythrocytes. Unexpectedly, amplification by PCR and sequencing of a DNA fragment of the small subunit rDNA combined with phylogenetic analyses indicated that the parasite is not a member of the suborder Adeleorina, which includes the Haemogregarina and Hepatozoon species, but that it is a clearly distinct member of the suborder Eimeriorina, which includes the cyst‐forming family Sarcocystidae. Therefore, a reclassification of this unusual intraerythrocytic apicomplexan will require additional life cycle, microscopic, and molecular analyses.     

Marker chromosomes commonly observed in the genus Glycine

Summary Soybean [Glycine max (L.) Merr.] chromosomes were analyzed using the chromosome image analyzing system, CHIAS, and seven groups, including subgroups, were identified based on morphological characteristics. Two pairs of chromosomes were conspicuous in their morphological traits. One pair of chromosomes, which had the largest arm ratio among all the chromosomes, was commonly observed in the species in all three subgenera of the genus Glycine. These chromosomes also displayed a unique pattern after N-banding and were detected as marker chromosomes. G. soja, which is considered to be the ancestor of G. max, has two types of marker chromosomes. The lines that carry the same type as G. max may be the ancestors of G. max among the lines of G. soja. The morphological differences of the marker chromosomes within the species in the subgenus Soja are discussed in relation to the domestication process of soybean.