Origin of Symphyotrichum anticostense (Asteraceae: Astereae), an endemic, high polyploid species of the Gulf of St. Lawrence region, based on morphological and nrDNA evidence

Symphyotrichum anticostense (Fernald) G.L.Nesom (Asteraceae: Astereae), a rare endemic of the Gulf of St. Lawrence region is a high allopolyploid (2n=10x=80). It has been hypothesized to be derived from the hybrid between tetraploid (2n=4x=32) individuals of S. boreale (Torr. & A.Gray) Löve & Löve and the hexaploid (2n=6x=48) S. novi-belgii (L.) G.L.Nesom. We investigated this hypothesis using morphological and molecular ITS-sequence data, and we tried to determine the potentially geographic origins of the taxon. Univariate morphological analyses show that 67.5% of the S. anticostense characters are parent-like, 43.5% from S. novi-belgii and 13% from S. boreale, the remainder not differing statistically from either parent; 23.5% are intermediate; and 9% transgressive. Multivariate analyses show that S. anticostense is intermediate between its putative parents. The molecular results support the morphological data, but due to the insufficient resolution among ribotypes on the tree, a more rapidly evolving marker will be needed to ascertain more reliably the origin of S. anticostense. Besides the hypothesis of genetic drift and allele fixation following long-distance dispersals, at least three independent geographic origins may be suggested for S. anticostense; Anticosti Island, Lake St. John, and Gaspé Peninsula-New Brunswick-Maine.

Mitosis and Interphase of the Highly Polyploid Palm Voanioalagerardii (2n = 606 ± 3)

The endemic, highly polyploid, monotypic Madagascan palm genus Voanioala (2n ≈ 606) was studied with regard to mitotic stages and interphase. Features of the cell cycle, morphology and sizes of metaphase chromosomes, fluorochrome banding patterns, and silver staining of NORs of such an extremely high polyploid organism are reported for the first time. On a whole, karyokinesis appears to be stable and efficient. A comparison with closely related palm taxa reveals that V. gerardii is 38-ploid, and comparison with the closely related genera Butia, Cocos (coconut) and Jubaea shows that Voanioala has lost ∼35% of its DNA amount subsequent to polyploidization and has suppressed between 74 and 88% of the original nucleolar organizers. About 10 active NORs are present in the nuclei. An auto- or allopolyploid origin of Voanioala is discussed with respect to currently available nuclear gene data. The biogeographic relations to Jubaeopsis, a closely related, monotypic, apparently likewise relict palm genus from eastern mainland South Africa are discussed. From a cytogenetic point of view, a common polyploid ancestor of both genera is most likely, but the available molecular phylogenetic data are not univocal.

Senecio L. (Asteraceae) in Australia: Rcombination systems of a polyploid series

Recombination systems of 32 species of Senecio are discussed in terms of chromosome number, chiasma frequency and position, breeding system and generation length. Darlington's recombination index cannot be applied to Senecio as several ploidy levels are represented. Increases in basic chromosome numbers promote recombination but increases by polyploidy buffer intermediate genotypes and retard evolutionary changes when selection is for homozygous or extreme phenotypes. High polyploid species of Senecio may therefore have recombination systems as restrictive as those produced by aneuploid reduction. When viewed in this manner, the majority of native species examined have recombination systems that contain a balance of restrictive and expansive factors regulating recombination.

CYTOLOGICAL STUDIES IN KRIGIA (ASTERACEAE)

The genus Krigia Schreb. consists of nine species representing diploid and polyploid taxa. Karyotype morphology and meiotic pairing of chromosomes for five species are described. Krigia cespitosa (2n = 8) and K. biflora (2n = 10) are diploids. Krigia montana with 2n = 20 is a tetraploid. Diploid and tetraploid forms of K. virginica with 2n = 10 and 20 were also studied. Krigia dandelion 2n = 60 is a high polyploid species.

Chromosome Studies of Brazilian Ferns

Chromosome numbers, habitat and general geographic distributions are reported for a sample of ferns from the vicinity of Manaus. These numbers are compared with those reported for species in other regions. The report of n=ca. 154 for Schizaea incurvata is the first record of the genus in the American tropics and the others are first counts of these species in continental South America. In Lindsaea n=42 and n=ca. 84, are somewhat lower and appear to represent a line distinct from the species of the paleotropics with n=47. In Trichomanes n=32, 64 and 128 appear to be levels of polyploidy based on X=8, while n = 72 is possibly based on X=9 and suggest possible diverse lines in the genus. Pityrogramma calomelanos with n=116 is considered as an octoploid based on X=29. Our sample covering about ten percent of the pteridophytes in the area we collected, yielded numbers ranging between n=32 and n=154, and generally appears to represent high polyploid levels.