The Miocene floras of Iceland and their significance for late Cainozoic North Atlantic biogeographyDENK, THOMAS; GRÍMSSON, FRIÐGEIR; KVAČEK, ZLATKO
doi: 10.1111/j.1095-8339.2005.00441.xpmid: N/A
AbstractA large number of plant macrofossils from several Middle to Upper Miocene localities from Iceland have been studied. The fossil material includes four ferns and fern allies, seven conifers, and about 40 species of flowering plants. Betula islandica and Salix gruberi are described as new species. Coniferous twigs previously ascribed to the genus Sequoia are shown to belong to Cryptomeria based on macro-morphological and epidermal features. Fossil plants from Iceland are compared with coeval fossil taxa from Europe and North America and with living plants. The main finding is that the Miocene flora of Iceland belongs to a widespread Neogene northern hemispheric floral type including plants whose representatives are restricted to East Asia, North America and to western Eurasia at the present time. Previously inferred conspicuous similarities to North American modern equivalents appear to be misleading. The type of vegetation in four plant-bearing sedimentary formations from the late Mid Miocene to Late Miocene, the 12 Ma Brjánslækur-Seljá Formation, the 10 Ma Tröllatunga-Gautshamar Formation, the 9–8 Ma Skarðsströnd-Mókollsdalur Formation, and the 7–6 Ma Hreðavatn-Stafholt Formation, corresponds to a humid temperate broadleaved (deciduous)–coniferous mixed forest dominated by Betulaceae, Fagaceae and Acer. Changes in species composition in the sedimentary formations reflect a shift from warm temperate (Cfa climate) to cool temperate (Cfb climate) conditions from the late Mid Miocene to the latest Miocene. This shift was connected to repeated phases of extinction and colonization. Specifically, one set of thermophilic taxa including Magnolia, Liriodendron, Sassafras and Comptonia went extinct between 12 and 10 Ma, and appears to have been replaced by another set of thermophilic taxa in the 10 Ma formation (Juglandaceae aff. Pterocarya/Cyclocarya, Rhododendron ponticum type). The 9–8 and 7–6 Ma formations are characterized by taxa that migrated to Iceland from Europe, such as Fagus gussonii, Betula cristata and Pterocarya fraxinifolia type. Although there is convincing evidence that plants colonized Iceland both from North America and Europe until 12 Ma, migration in the younger formations (9–8, 7–6 Ma) is suggested to have occurred mainly from Europe.
A morphological, karyological and chemical study of the Apteranthes (Caralluma) europaea complexMEVE, ULRICH; HENEIDAK, SAMIA
doi: 10.1111/j.1095-8339.2005.00448.xpmid: N/A
AbstractThe Apteranthes europaea complex (Apocynaceae–Asclepiadoideae–Ceropegieae–Stapeliinae) distributed from Morocco/southern Spain along the North African coast of the Mediterranean Sea up to Sinai, Negev and southern Jordan is studied with emphasis on stem and flower morphology by SEM, chromosome sizes and flavonoid compounds. Apteranthes europaea was found to be rich in rather uncommon flavone glycosides. Of these, luteolin 4′-neohesperidoside represents the major flavonoid of all samples; luteolin-3′-O-(6′-O-sinapoylglucoside)-4′-O-neohesperidoside and luteolin-3′-O-(6′-O-feruloylglucoside)-4′-O-neohesperidoside are reported here for the first time. Flavonol glycosides also occur, but in much smaller quantities. The different flower morphs, variation in stem and corolla epidermal structures, slight variations in the length of the 2n = 22 chromosomes and in quantitative flavonoid composition are taxonomically best reflected by subdividing the complex into a western var. europaea (Europe and Africa) and an eastern var. judaica (Sinai, Arabia).
Stem demography and post fire recruitment of Podocarpus drouynianus: a resprouting non-serotinous coniferCHALWELL, S. T. S.; LADD, P. G.
doi: 10.1111/j.1095-8339.2005.00454.xpmid: N/A
AbstractPodocarpus drouynianus is unusual in the Podocarpaceae and conifers in general in being a strongly resprouting species which thrives in a fire-prone environment. The species is a dioecious, multi-stemmed shrub endemic to the eucalypt forests of the south-west of Western Australia. Stems are killed by fire but it is able to regenerate its foliage from a lignotuber. The total bud bank seems to be released by burning and death of the shoots, while pruning without fire releases only a proportion of available buds. Growth rate of resprouts is initially rapid, with stems reaching 25% of their mature length in the first year after fire. However, growth of juvenile plants is very slow. Fire promotes cone production on the new stems about one year after fire. The large seed is recalcitrant but timing of germination coincides with the wettest time of the year in the area where the species grows. Pyrogenic coning avoids loss of seed due to severe fires and is a form of mast reproduction that benefits this species by increasing pollen transfer and producing a mass seed crop to attract the primary vertebrate disperser – the emu. The strong resprouting ability ensures the species is resilient to frequent disturbance and to severe predation of the seed crop. Vertebrate dispersal tends to concentrate seed lots, making them vulnerable to predation if they are deposited in open areas. However, being dispersed by a large vertebrate will ensure long-distance dispersal, often to areas beyond that which was subject to fire. These would include vegetated areas, where the large seeds could lodge in safe sites and produce seedlings that are able to survive under the shade of established plants.
Karyotype differentiation between Koelreuteria bipinnata and K. elegans ssp. formosana (Sapindaceae) based on chromosome banding patternsURDAMPILLETA, JUAN D.; FERRUCCI, MARÍA S.; VANZELA, ANDRÉ L. L.
doi: 10.1111/j.1095-8339.2005.00440.xpmid: N/A
AbstractKoelreuteria Laxm., a genus in the tribe Koelreuterieae (Sapindaceae), includes three tree species that are widely recognized as having horticultural merit. The two more closely related species, K. bipinnata Franch. and K. elegans (Seem.) A. C. Sm., are easily distinguished from K. paniculata Laxm. by their bipinnate leaves. In this study, both species were investigated cytogenetically and their karyotypes and heterochromatic patterns were compared. Koelreuteria bipinnata and K. elegans ssp. formosana (Hayata) F. G. Mey. both have 2n = 32 but their karyotypes present slight morphological differences when observed using conventional staining. Chromosome banding patterns are reported for the first time for this genus. Both species exhibit terminal heterochromatic blocks, as revealed by C-Giemsa and C-CMA3, but the band size varies between the species. Koelreuteria bipinnata has larger heterochromatic blocks and more GC-rich segments, while in K. elegans ssp. formosana these bands are smaller. The relationship between the karyotype features in these closely related species is discussed.
Reduction of chromosome number in Eleocharis subarticulata (Cyperaceae) by multiple translocationsDA SILVA, CARLOS R. M.; GONZÁLEZ-ELIZONDO, M. SOCORRO; VANZELA, ANDRÉ L. L.
doi: 10.1111/j.1095-8339.2005.00449.xpmid: N/A
AbstractEleocharis subarticulata is recorded as the third species of Cyperaceae with a reduced chromosome number (n = 3), following reports on Rhynchospora tenuis (n = 2) and Fimbristylis umbellaris (n = 3). For Eleocharis, the numbers recorded to date vary from 2n = 10 to 2n = c. 196, with x = 5 as the possible basic number. The karyotype of E. subarticulata was studied using conventional staining (mitosis and meiosis), C-CMA3/DAPI banding, and FISH with 45S rDNA and telomere probes. The chromosomes showed no primary constrictions, as expected in the holocentric chromosomes of Cyperaceae. The meiotic behaviour was abnormal, with a single multivalent ring of six chromosomes at metaphase I, resulting from multiple translocations. At anaphase I six chromatids migrated to each pole, evidencing the inverted meiosis, and these groups were also visible at metaphase II. The C-CMA3/DAPI banding technique showed only four terminal GC-rich blocks. FISH with 45S rDNA probes revealed four terminal signals, probably associated with GC-rich blocks. The telomeric probe located terminal signals in all the chromosomes, besides a hybridization site in the middle of the large pair. The occurrence of ectopic telomeric sites has not been described previously for plants with holokinetic karyotypes and with reduced chromosome numbers. These data reinforce the hypothesis of the reduction in chromosome number by multiple translocations.
Floral anatomy of Thomandersia (Lamiales), with particular reference to the nature of the retinaculum and extranuptial nectariesWORTLEY, ALEXANDRA H.; SCOTLAND, ROBERT W.; RUDALL, PAULA J.
doi: 10.1111/j.1095-8339.2005.00507.xpmid: N/A
AbstractThomandersia is an isolated genus that is currently unplaced in Lamiales. In the past it has been classified in Acanthaceae or Pedaliaceae, on the basis of intuitive assessments of a limited number of morphological characters. Recent molecular sequenced-based phylogenies have suggested a relationship to Bignoniaceae, Schlegeliaceae or Verbenaceae. Here we present new observations of the floral anatomy of Thomandersia, with particular emphasis on the structure of the retinaculum, a character shared with Acanthaceae, and calyx nectaries, which may be shared with other families in Lamiales. The morphological and anatomical characters of Thomandersia are discussed in the context of recent phylogenetic hypotheses for Lamiales, with the aim of identifying potential primary and secondary homologies between Thomandersia and related families in Lamiales. We find that Thomandersia shares a range of characters with each of the families to which it might be sister-group, and that some of these primary homologies must therefore be homoplastic. In particular, if the topology based on molecular sequence data is correct, the retinacula of Thomandersia and Acanthaceae are homoplastic and represent an example of parallel morphological evolution.