Karyological study in the genusTuberaria sect.Scorpioides (Cistaceae): Taxonomic and evolutionary inferences

A polyploid complex ofTuberaria sect.Scorpioides species in S Spain has been studied. We have found the chromosome numbers n = 12 and 18, which probably originated from the extinct base number x = 6 by means of allopolyploidy. Octoploids (n = 24) seem to be the result of different crossings, and fall morphologically withinT. guttata, T. inconspicua, orT. commutata. Backcrosses between octoploids and tetraploids originate new hexaploids (n = 18), which, once stabilized, behave as amphidiploids. Most of these also fall within the traditional concept ofT. guttata, so that the enormous polymorphism of this taxon seems to be justified.     

Floral development and systematics ofCistaceae

The floral development of representatives of six genera ofCistaceae has been studied. Calyx development involves the formation of a ring primordium in several taxa. Androecium development in species with intermediate or higher stamen numbers starts with the formation of a ring meristem on which the stamens are initiated in a centrifugal direction. In many taxa five alternipetalous leading stamen primordia can be observed. In the apetalous (cleistogamous) flowers ofTuberaria inconspicua androecium development appears to be unordered; this is probably due to the lack of petals. InLechea intermedia (also cleistogamous) the corolla is trimerous and three complex stamen primordia are produced, which give rise either to one or three stamens. Relationships withinCistaceae are discussed. Floral development inCistaceae is compared with that in otherMalvanae. Among the eight families ofMalvanae from which information on floral development is availableCochlospermaceae andBixaceae exhibit the greatest similarities toCistaceae. InCistaceae the leading stamen primordia are alternipetalous. InBixa the same condition seems to be present. InMalvales s. str. mostTiliaceae also show earliest stamen initiation in alternipetalous sectors, whereas the stamens of the innermost alternipetalous position are retarded early or even suppressed inSterculiaceae, Bombacaceae, andMalvaceae. WithinMalvales s. str. the diversity of androecial developmental patterns seems to decrease inBombacaceae andMalvaceae due to increasing synorganization in the mature androecium. The derivation of polyandry inMalvanae from diplo- or obdiplostemony is discussed by comparison with the sister clades ofMalvanae as shown in recentrbcL studies (i.e.Sapindales, Rutales, the glucosinolate producing clade, andMyrtales).     

Efficiency of endozoochorous seed dispersal in six dry-fruited species (Cistaceae): from seed ingestion to early seedling establishment

We combined laboratory and nursery experiments to analyse the effectiveness of sheep as endozoochorous seed dispersers of six native shrubby Cistaceae species collected in SE Spain (Helianthemum apenninum (L.) Mill., H. violaceum (Cav.) Pers., Fumana ericoides (Cav.) Grand., F. thymifolia (L.) Spach, Cistus monspeliensis L. and C. laurifolius L.), considering the main stages after seed ingestion, i.e. seed recovery, seed germination, seedling emergence and early seedling establishment. Seed recovery after gut passage was high (around 40%) for all the species, except F. thymifolia (12%). Most seeds (ca. 90%) were recovered within 48 h after ingestion for all the species, although seeds were still recovered up to 96 h after ingestion. Gut passage increased germination up to seven-fold compared to non-ingested seeds. Furthermore, seedling emergence from seeds contained in pellets was overall similar (intact pellets) to or higher (crumbled pellets) than emergence from seeds without dung. Survival of emerged seedlings and mass of seedlings after 20 days were not reduced by dung. Sheep act therefore as effective dispersers of these Cistaceae species by scattering seeds and promoting germination, while faeces do not hamper seedling establishment. We conclude that the interaction between herbivorous ungulates and these dry-fruited species may be considered a mutualism qualitatively similar to the mutualism between frugivorous vertebrates and fleshy-fruited plants.     

Intrapopulation variation in the breeding system ofVillarsia lasiosperma (Menyanthaceae), a distylous species

The restricted perennial diploid herb,Villarsia lasiosperma, of southwestern Western Australia has distylous flowers with dimorphism in style and stamen length, stigma morphology, and pollen size. In order to assess the presence and nature of an incompatibility system in this species, a crossing program was carried out using 17 plants grown from seeds collected in two field populations. Pollen stainabilities of these plants mostly exceeded 95%. Mean seed-set of Longs following intermorph pollinations was c. 24 seeds per pollination and for Shorts was c. 16 seeds per pollination. Approximately three-quarters of the Longs and Shorts produced no seeds after self-pollination; the remainder produced very few seeds following such pollinations. No Shorts produced seeds after intramorph cross-pollinations. However, about half the Longs exhibited various levels of weakened intramorph incompatibility, with mean seed-sets following intramorph cross-pollinations up to half the mean seed-sets following intermorph pollinations. In the behavior of Longs, the incompatibility system ofV. lasiosperma differs from the idealized distylous breeding system, but resembles that of a purported close relative,V. exaltata of eastern and southeastern Australia.     

The breeding system ofEmblingia (Emblingiaceae)

Emblingia is a short lived fire weed with a highly autogamous breeding system.     

A new taxon in the genusMoehringia (Caryophyllaceae)

The new taxonMoehringia intricata subsp.giennensis, from the calcareous mountains of the south-eastern Iberian Peninsula is described. A comparative morphological study with regard to the most closely related taxa, contributes information of leaf anatomy, seed and pollen morphology, ecology and distribution.     

Flower and fruit development in the Macaronesian endemicCeballosia fruticosa (syn.Messerschmidia fruticosa,Boraginaceae, Heliotropioideae)

The ontogeny of the flower and the fruit of the Macaronesian endemicCeballosia were investigated morphologically and anatomically by SEM and LM. The fruit does not break into four mericarps, but splits into two two-seeded carpids. Exo- and mesocarp wither after fruit-ripening and the endocarp constitutes the remaining outer wall. Within the stony endocarp tubular parenchymatic isles develop which are linked with the mesocarp. Subsequent disintegration pretends additional locules in the mature fruit. Similar pericarp formations are also found in someHeliotropium species but result from a different ontogeny. Therefore, although a close relationship ofCeballosia toHeliotropium is obvious, the taxon should be treated as a separate genus.Carpological investigations in theHeliotropioideae (Boraginaceae) 2. For part 1 seeHilger (1987).     

Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

Allozyme and life history variation in five northwardly colonizing North American weed species

The relationships of allozyme and life history variation in a particularly narrow ecological setting are studied. Levels of genetic variation are compared in five introduced, predominantly selfing weedy species that are undergoing rapid range expansion northward in eastern N. America, mostly in monocultures of soybean and maize. In all of these species, a low level of allozyme variation contrasts sharply with the substantial inter- and intrapopulational variation in morphological and phenological life history features. Evolutionary and historical factors, determining variability of the species examined are reviewed, including founder effects, breeding system, environmental homogeneity, polyploidy, domestication, and crop-weed interactions.     

Use of monocharacteristic growth forms and phenological phases to describe and differentiate plant communities in Mediterranean-type ecosystems

The ecomorphological and phenological study was carried out within aMediterranean vegetation context, in Quercus suberforests,which have been substituted by shrublands of Cistus sppwithin two Natural Parks in the south of the Iberian Peninsula. Theecomorphological characters that show meaningful differences between both typesof vegetation are: location of renewal buds, spinescence, stratification,maximum height of the vegetation, organs periodically shed, leaf consistency,leaf tomentosity, leaf size, and life duration of leaves, plant duration,vegetative regeneration after fire, main vegetative growth season, mainflowering season and fruit type. The phenological phases also help to discernbetween forest and shrubland, specially flower bud formation, fruiting, seeddispersal, and the existence of brachyblast vegetative growth and brachyblastleaf shedding. We propose three new indexes based on phenological phases:active period of the species (APS), active period of thecommunity (APC) and reproductive/vegetative activity of thespecies (RVA). The results of their application, in combination with theecomorphological characters, have proved promising in describing vegetation andin clearly differentiating communities. The results also show the existence ofdifferent ecomorphological groups of plants at community level, with consequentecological, historical, phytocoenological and adaptive implications     

Chromosome numbers in AustralianEuphrasia (Scrophulariaceae)

Chromosome numbers for six Australian taxa ofEuphrasia have been determined. Improved staining techniques have shown that numbers for four of the taxa published previously by the first author were incorrect. The investigated taxa show high ploidy levels with an apparent base number of x = 11, the same as for the genus outside Australia.Dedicated to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday.     

New and noteworthyHabenaria spp. (Orchidaceae) from New Guinea and adjacent islands

5 new taxa ofHabenaria, namelyH. bougainvillae, H. elongataR. Br. var.leptophylla, H. ensigera, H. rechingeri andH. trichoglossa, are described and illustrated, with reference to affinities to related Australian and Indo-malayan species. The occurrence in New Guinea of severalHabenaria spp. typical for a savanna-like vegetation, led to look more thoroughly at these taxa:H. elongataR. Br. andH. ochroleucaR. Br., considered so far to be endemic in Northern Australia, andH. khasianaHook. f., hitherto only known from southeastern Asia.Studies in the subtribeHabenariinaeBentham (Orchidaceae), 2.—Part 1: Candollea34, 357 (1979).Dedicated to Hofrat Prof. DrKarl Heinz Rechinger on the occasion of his 80th birthday. — On April 30, in the year 1927, the author and his brotherOtto Renz metKarl Heinz Rechinger on a small steam-boat in a stormy Aegaen Sea, travelling from Piraeus to the Northern Sporades Islands:Karl Heinz with destination to Chelidromia, the author andO. Renz to Skopelos. By this lucky chance a lasting friendship began.     

Micromorphological and phytochemical characters ofTeucrium marum andT. subspinosum (Labiatae) from Sardinia and Balearic Islands

Micromorphology and distribution of trichomes in different plant parts ofTeucrium marum andTeucrium subspinosum from Sardinia and the Balearic Islands are described. The composition of volatile compounds in the same plants has also been studied. The occurrence in Sardinia of two differentT. marum entities is evidenced. One of them, growing in the NW. part of the island, is very similar toT. marum from Minorca.T. subspinosum from Sardinia and Majorca differ for the presence in the last one of short capitate hairs and for a higher ratio of dolichodial/teucrein. While the degree of variability of all the characters is very high, there is a good homogeneity between all the taxa, due to the presence of monoterpene cyclopentanoids not found until now in other species.     

Structure and function in asclepiad pollination

Aspects of floral biology in relation to floral structures are investigated in seven species ofAsclepiadaceae. Pollinaria removal and insertion by the insect pollinator is aided by various structural devices such as hairs or corona elements guiding the proboscis towards the entrance of the anther slit. The nectary is situated directly below this opening, thus increasing the probability of the proboscis being introduced into the anther slit during retraction. The anther slit itself often displays structural differentiation in adaptation to the guiding of the proboscis and the insertion of a pollinium in cross pollination. These mechanisms are highly elaborated so that they work as well in closed flower types, in which the pollinator does not enter the flower directly, but only introduces its proboscis (Sisyranthus, Microloma). A special feature of pollinaria removal is the variety of ways of fixing the corpusculum against the force of the proboscis when it is drawn into the cleft. — The stigma of all species exceptSecamone is located on the lower surface of the stigma head where it is appressed to the filament tube. In some cases a direct contact of the inserted pollinium with the stigmatic surface does not seem to be necessary for pollen tube germination, probably moistening by nectar suffices in these flowers. WithTylophora spec., a case of in situ pollen tube germination has been studied. — Concerning the path of the pollen tubes, two different strategies are followed.Secamone andTylophora develop a structurally defined compitum, while the other five species have strictly divided stylar canals. In these higher evolved species, the pollen tubes of one inserted pollinium are all directed into one ovary only, thus enabling the plant to allocate its resources to one carpel only in the frequent case of fertilization by one pollinium.

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Zusammenfassung An sieben Asclepiadaceen-Arten wird der Zusammenhang von Blütenstrukturen mit dem Bestäubungsprozeß untersucht. Die Analyse erfaßt die Bandbreite von einfacher organisierten (Secamone) bis zu hochdifferenziertenAsclepiadaceae, wobei neben dem offenen Blütentyp auch zwei Formen von geschlossenen Blüten (Sisyranthus, Microloma) untersucht werden. Die Blüten weisen unterschiedlich stark elaborierte Strukturen auf, die als Führungshilfen für den Insektenrüssel dienen. Neben der eigentlichen Leitschiene, die teilweise einen hohen Grad an innerer Differenzierung besitzt, sind vor allem Haare und Coronastrukturen an der primären Führung des Bestäuberrüssels beteiligt. Die interstaminale Lage der Nektarien sowie ihr Hinaufreichen bis zur Leitschiene sichert ebenfalls das Zurückziehen des Rüssels durch die Leitschiene. Die Einführung des Rüssels in den Spalt des Klemmkörpers erfordert einen relativ festen Sitz des Corpusculums, der in den hier untersuchten Arten auf drei verschiedenen Wegen erreicht wird: Anheftung an den Antherenrändern, basales Ankleben am Griffelkopf und Fixierung durch einen distalen Vorsprung des Griffelkopfes. MitTylophora spec. wird ein Fall vorgestellt, bei dem Fremdbestäubung wie auch Auskeimen der Pollenschläuche in situ und damit vermutlich Autogamie zugleich vorkommen. — Die übertragenen Pollinien werden gewöhnlich in die Narbenkammer eingezogen, dort keimen die Pollenschläuche aus und dringen an der Unterseite des Narbenkopfes in diesen ein. BeiSecamone erfolgt der Eintritt der Pollenschläuche an der Flanke des Griffelkopfes, beiMicroloma ist eine exakte Positionierung des Polliniums unnötig, auch vor der Leitschiene abgelegte Pollinien keimen und senden ihre Pollenschläuche durch die innere Leitschiene zum Griffelkopf. BeiSecamone undTylophora ist ein gemeinsamer Anfang der Griffelkanäle (Compitum) im Griffelkopf vorhanden, die Pollenschläuche werden hier auf beide Ovarien verteilt, auch wenn sie nur von einem einzigen eingeführten Pollinium stammen. Bei den übrigen fünf Arten sind beide Griffelkanäle isoliert voneinander, eine direkte Zuweisung der Pollenschläuche eines Polliniums zu nur einem Ovar ist hier die Regel. Damit verfolgen diese höher evolviertenAsclepiadaceae eher die Strategie der resource allocation, indem sie bei der vorherrschenden Belegung mit nur einem Pollinium durch die strukturell gelenkte Zuweisung der Pollenschläuche auch nur ein Fruchtblatt zur Reife bringen müssen.

     

Spatial variation of seedling distribution in an east Mediterranean pine woodland at the beginning of post-fire succession

Most of the area in pine woodlands is occupied by perennial seeders that regenerate from seeds in the first winter after the fire and by annuals. Control of the germination in the regenerating vegetation after wildfire is therefore a primary ecological component of the post-fire succession in this ecosystem. The aim of the study presented here was to determine the distribution of Pinus, Cistus and other plants seeds around burned Pinus halepensis trees, and to measure the conditions related to seed germination in the upper soil layers in the same locations. The study was carried out in a 50-year old planted Pinus halepensis woodland that was burned down by a wildfire in July 1995. The variation of seedbank density was determined by collecting samples under the canopies of burned trees and in a nearby open area. Pine seedbank density decreased and that of Cistus and annuals increased with increasing distance from the burned trunks. Most pine seeds were present in the ash layer while those of the other plants were in the soil. In situ germination experiments showed that seedling density decreased with distance from the burned trunks while the proportion of pines in the seedling population increased. This was a result of seedbank variation and germination inhibition by the high pH conditions caused by the ash. The establishment of sparse pine seedling under the dead tree canopies insured their rapid development without interference by other plants and played a key role in the regeneration and stability of the pine woodland community. The concomitant mass germination of the perennial seeders in the rest of the area prevented invasion by annuals.     

Developing a breeding strategy to exploit quantitative variation in symbiotic nitrogen fixation

Summary This paper examines evidence which quantifies the relative importance of legume and Rhizobium genotypes as determinants of phenotypic variation in symbiotic nitrogen fixation. It demonstrates potentially large and unpredictable effects of the Rhizobium genotype. The likely importance of such effects on crop yield is considered. The information is then used to assess ways in which legume breeding programmes may be altered to encompass the effects of genetic variation in Rhizobium.     

Globba unifolia andG. corneri stat. et nom. nov. (Zingiberaceae; Peninsular Malaysia)

Based on personal collections ofGlobba unifoliaRidl. andG. unifolia var.sessilifloraHoltt., the latter is recognized as a distinct species. As the nameG. sessiliflora is already occupied, the nomen novumG. corneri is proposed in honour of Prof. DrE. J. H. Corner, who was the first collector of the plant.Dedicated to Prof. DrE. J. H. Corner (Cambridge) on the occasion of his 85th birthday on January 12th, 1991.     

Environmental variation for outcrossing rate in rapeseed (Brassica napus)

Summary Rapeseed (Brassica napus) is a predominantly selfpollinated crop with about one-third outcrossing. The outcrossing rate may be influenced by environmental factors, and hence changes in the heterozygosity level of a variety may occur during multiplication. In an investigation on environmental variation in outcrossing, we estimated the outcrossing rate in the Swedish spring rapeseed cv Topas by isozyme analysis and found that outcrossing varied from 12% to 47% over five locations in Sweden, Denmark and Germany. Among flowers at different positions on the same plant, average outcrossing varied from 11% at the top to 39% at the bottom of the plant. In conclusion, environmental factors can greatly influence the outcrossing rate in rapeseed, and an investigation therefore merit further studies.     

A phenetic study ofFritillaria (Liliaceae) in Greece

40 population samples of 17 GreekFritillaria species were examined morphologically using 22 attributes carefully selected, with a high discriminating ability. Principal component analysis with a nearest neighbour directed network and cluster analysis were used to evaluate the phenetic similarities among the species. The evidence presented here suggests: (1) A close relationship betweenF. erhartii andF. obliqua and their possible origin fromF. bithynica. (2) A strong alliance betweenF. rixii, F. euboeica, F. carica, andF. drenovskii (groupF. sibthorpiana). (3) A link between theF. epirotica andF. graeca group and some affinities betweenF. pontica, F. gussichiae, andF. graeca. Finally it is proposed thatF. tuntasia be reduced to subspecific status asF. obliqua subsp.tuntasia. This study forms a part of a doctoral dissertation thesis submitted to the Department of Biology of the University of Thessaloniki.