S-allele diversity in Sorbus aucuparia and Crataegus monogyna (Rosaceae: Maloideae)

RT-PCR was used to obtain the first estimates from natural populations of allelic diversity at the RNase-based gametophytic self-incompatibility locus in the Rosaceae. A total of 20 alleles were retrieved from 20 Sorbus aucuparia individuals, whereas 17 alleles were found in 13 Crataegus monogyna samples. Estimates of population-level allele numbers fall within the range observed in the Solanaceae, the only other family with RNase-based incompatibility for which estimates are available. The nucleotide diversity of S-allele sequences was found to be much lower in the two Rosaceae species as compared with the Solanaceae. This was not due to a lower sequence divergence among most closely related alleles. Rather, it is the depth of the entire genealogy that differs markedly in the two families, with Rosaceae S-alleles exhibiting more recent apparent coalescence. We also investigated patterns of selection at the molecular level by comparing nucleotide diversity at synonymous and nonsynonymous sites. Stabilizing selection was inferred for the 5' region of the molecule, while evidence of diversifying selection was present elsewhere.     

Inheritance of the chloroplast genome in Sorbus aucuparia L. (Rosaceae)

Chloroplast DNA (cpDNA) inheritance was investigated in Sorbus aucuparia using progenies obtained from six controlled crosses between individuals of known haplotype. Polymerase chain reaction (PCR) amplification, followed by restriction analysis, was used to characterize 248 offspring for either of two polymorphic cpDNA fragments. All offspring exhibited the maternal haplotype, which indicates maternal inheritance of chloroplasts in S. aucuparia. Power analysis of the test showed that the frequency of paternal transmission of chloroplasts, if any, should not exceed 1.84% (with 99% confidence).     

Fifteen new species and varieties ofAlchemilla (Rosaceae)

Nine newAlchemilla species and six new varieties are described in subsect.Euvulgares ser.Subglabrae and subsect.Calicinae. Further, for one species a new name is proposed. The plants published as new mostly come from the higher altitudes of the Slovakian mountains. Problems in the treatment ofA. obtusa Bus.,A. glabra Neyg., andA. incisa Bus. are discussed.     

Population structure at the S-locus of Sorbus aucuparia L. (Rosaceae: Maloideae)

Low sequence divergence within functional alleles is predicted for the self-incompatibility locus because of strong negative frequency-dependent selection. Nevertheless, sequence variation within functional alleles is essential for current models of the evolution of new mating types. We genotyped the stylar self-incompatibility RNase of 20 Sorbus aucuparia from a population in the Pyrenees mountains of France in order to compare alleles found there to those previously sampled in a Belgian population. Both populations returned 20 different alleles from samples of 20 individuals, providing maximum-likelihood estimates of 24.4 (95% CI 20-34) alleles in each. Ten alleles occurred in both samples. The maximum likelihood (ML) estimate of the overlap in the alleles present in both populations was 16, meaning that an estimated eight alleles are private to each population, and a total of 32 alleles occur across the two populations examined. We used Fisher's (1961) missing plot method to estimate that 40 alleles occur in the species. In accord with population genetics theory, we observed at most one synonymous sequence difference between copies of alleles sampled from the different populations and no variation within populations. Phylogenetic analysis shows that nearly every allele in S. aucuparia arose prior to divergence of this species from members of three different genera of the Rosaceae subfamily, Maloideae. Lack of observable sequence variation within alleles, coupled with the slow pace of allelic relative to taxonomic diversification, implies that finding intermediate stages in the process of new allele creation will be difficult in this group.     

Rediscoveries of two species of Rubus (Rosaceae) in China

报道了蔷薇科两种悬钩子属植物在中国的重新发现,分别为美叶悬钩子(Rubus calophyllus C.B.Clark)和拟针刺悬钩子(R.parapungens H.Hara),并提供了简要的描述和标本照片.     

The relative fitness of parental and hybrid Kunzea (Myrtaceae): The interaction of reproductive traits and ecological selection

Up to 22% of plant species are the result of breeding among species-hybridization-directly conflicting with the prediction that hybrids, compared to parental species, are intermediate in character and of low fitness and little consequence. Few studies, however, have compared the fitness of hybrids and parental species under field conditions. This study evaluates components of fitness in the field for naturally occurring hybrids of the shrub Kunzea, relative to the parental speciesKunzea rupestris. Hybrid plants did not differ from the parental species in the level of effective pollination. Thus, we found no support for Grant's model (Evolution: International Journal of Organic Evolution3: 82-97) of reduced fitness of hybrids via reduced pollination level (the intermediate hypothesis). Hybrids displayed variable fitness across the measured fitness components. Seed set levels for hybrids were structured among populations, suggesting genetic structuring for this fitness component at this scale. The response of hybrids to fire (a major selective force in the study system) was partly consistent with a resource trade-off model. Hybrids were large robust plants but most did not resprout after fire. Hence, the fitness of hybrids was complex. We developed a model for relative fitness to estimate fitness for species and hybrids with complex life histories.     

Photosynthetic characteristics of invasive and noninvasive species of Rubus (Rosaceae)

The prolific amount of growth and reproduction in invasive plants may be achieved by greater net photosynthesis and/or resource-use efficiency. I tested the hypotheses that leaf-level photosynthetic capacity and resource-use efficiency were greater in two invasive species of Rubus as compared with two noninvasive species that have overlapping distributions in the Pacific Northwest. The invasive species had significantly higher photosynthetic capacity and maintained net photosynthesis (A) over a longer period of the year than the noninvasive species. The construction cost (CC) of leaf tissue per unit leaf mass was comparable among the four species, but the invasive species allocated less nitrogen (N) per unit leaf mass. On a leaf area basis, both leaf CC and N were higher for the invasive species. The specific leaf area (SLA) was also lower in the invasive species, indicating less photosynthetic area per gram leaf tissue. The invasive species achieved high A at lower resource investments than the noninvasive species, including having higher maximum photosynthetic rate (A(max)) per unit dark respiration (R(d)), greater A(max) per unit leaf N (photosynthetic nitrogen-use efficiency), and greater water-use efficiency as measured by instantaneous rates of A per unit transpiration (A/E) and by integrated A/E inferred from stable carbon isotope ratios (δ(13)C). Using discriminant analysis, these photosynthetic characteristics were found to be powerful in distinguishing between the invasive and noninvasive Rubus. A(max) and A/E were identified as the most useful variables for distinguishing between the species, and therefore, may be important factors contributing to the success of these invasive species.     

Leaf biomechanics, morphology, and anatomy of the deciduous mesophyte Prunus serrulata (Rosaceae) and the evergreen sclerophyllous shrub Heteromeles arbutifolia (Rosaceae)

Leaf tensile properties were compared between the mesic deciduous tree Prunus serrulata (var. "Kwanzan") and the xeric and sclerophyllous chaparral evergreen shrub Heteromeles arbutifolia (M. Roem). All values for biomechanical parameters for H. arbutifolia were significantly greater than those of P. serrulata. The fracture planes also differed between the two species with P. serrulata fracturing along the secondary veins, while H. arbutifolia most often fractured across the leaf irrespective of the vein or mesophyll position, thus yielding qualitative differences in the stress-strain curves of the two species. Anatomically, P. serrulata exhibits features typical for a deciduous mesophytic leaf such as a thin cuticle, a single layer of palisade mesophyll, isodiametric spongy mesophyll, and extensive reticulation of the laminar veins. Heteromeles arbutifolia leaves, however, are typically two- to three-fold thicker with a 35% higher dry mass/fresh mass ratio. The vascular tissue is restricted to the interface of the palisade and spongy mesophyll near the center of the leaf. Both epidermal layers have a thick cuticle. The palisade mesophyll is tightly packed and two to three layers thick. The spongy mesophyll cells are ameboid in shape and tightly interlinked both to other spongy cells as well as to the overlying palisade layer. We conclude that the qualitative and quantitative biomechanical differences between the leaves of these two species are likely due to a complex interaction of internal architectural arrangement and the physical/chemical differences in the properties of their respective cell walls. These studies illustrate the importance that morphological and anatomical correlates play with mechanical behavior in plant material and ultimately reflect adaptations present in the leaves of chaparral shrubs that are conducive to surviving in arid environments.     

Characteristics of floral nectaries and nectar in two species of Crataegus (Rosaceae)

 The structure of floral nectaries of Crataegus coccinea and C. crus-galli was examined using light and scanning electron microscopy. The radial length of the floral nectary, measured from longitudinal sections of flowers, was 30% larger in C. crus-galli than in C. coccinea. For both Crataegus species the glandular tissue thickness was similar – approx. 400 μm. Also, the number of stomata per mm² of nectary surface in C. crus-galli was much higher (by 43%) than for C. coccinea. Stomata were situated in deep hollows. For both taxa the period of nectar secretion was 4 days. The mean quantity of total sugar in nectar per 10 flowers of C. crus-galli and C. coccinea was 3.87 mg and 0.33 mg, respectively. Received August 28, 2002; accepted December 17, 2002 Published online: June 2, 2003     

Reproductive biology of twoPrunus species (Rosaceae) in the Northwest Iberian Peninsula

We studied the reproductive biology ofPrunus spinosa andPrunus mahaleb (Prunoideae, Rosaceae) in the northwest Iberian Peninsula. The two species flowered at the same time (peaking on March 9 and 11, respectively in 1990) but differ significantly in their fruit maturation times. Nectar volume peaked in the early morning in both species, and was ten times greater inP. spinosa than inP. mahaleb. Neither species shows apomixis, nor does fruit-set occur if pollinators are excluded. In both species self-pollination resulted in fewer fruits than open pollination. The principal pollinators belong to theApidae family (79% and 63% of visits toP. spinosa andP. mahaleb, respectively). Results are compared with those for other rosaceous plants with fleshy fruits.     

A variable minisatellite sequence in the chloroplast genome of Sorbus L. (Rosaceae: Maloideae).

The chloroplast genome is now known to be more variable than was once thought. Reports of RFLP (restriction fragment length polymorphism) and sequence variation, as well as variation in chloroplast microsatellites, are common. Here, data are presented on the variability of a minisatellite sequence in the chloroplast genome of Sorbus species. RFLP analysis of a PCR product comprising the region between the trnM and rbcL genes of nine Sorbus species identified seven size variants. Sequencing revealed the observed size polymorphism to be due to differences in the number of copies of an imperfect 9-bp motif. A more intensive survey of the variability of the minisatellite was undertaken in populations of Sorbus aucuparia. The potential uses of such regions in chloroplast DNA are discussed and a possible mechanism for the evolution of the minisatellite is presented.     

Fruit production in Sorbus aucuparia L. (Rosaceae) and pre-dispersal seed predation by the apple fruit moth (Argyresthia conjugella Zell.)

Variation in fruit production and pre-dispersal seed predation by Argyresthia conjugella was studied in␣four populations of Sorbus aucuparia in northern Sweden.␣The number of infructescences, fruits per infructescence, consumed seeds and developed unattacked seeds per fruit were scored in marked trees from 1984 to 1990. The results showed that the number of fruits produced in each population determined the number of seed predators occurring in the host population, as the yearly number of seed predators was significantly and positively correlated with yearly number of fruits, in all but one population. The seed predators showed a delay in response to variation in number of fruits produced. This lag in response resulted in a large proportion of fruits being attacked and seeds consumed in a bad fruiting year that followed a good fruiting year, and vice versa. The proportion of fruits attacked and seeds consumed was largest in the population showing the greatest between-year variation in fruit production and lowest in the population showing the lowest between-year variation in fruit production. Furthermore, the individuals within the former population were synchronised, while they were not in the latter population. These results contradict one of the possible explanations of mast-seeding, where large synchronised between-year variation is supposed to reduce pre-dispersal seed predation. Instead, differences in attraction of the seed predator to differences in fruit crop size could explain the observed difference in seed predation between the two populations with opposite fruiting patterns. Within each population, irrespective of year, the proportion of fruits attacked and seeds consumed was independent of a tree's fruiting display. Therefore, trees with high fruit production, despite harbouring the largest number of seed predators, produced the largest number of developed seeds in absolute numbers, compared to trees that produced few fruits. Received: 25 February 1996 / Accepted: 30 November 1996     

A new species of Ivesia (Rosaceae) from Lassen County,California

A new species,Ivesia paniculata, is described, illustrated and contrasted with its closest relatives. A key to the California five-stamenedIvesia is presented.     

Rubus vestervicensis (Rosaceae) — its hybrid origin revealed by DNA fingerprinting

Kraft, T., Nybom, H. & Werlemark, G. 199.5. Rubus vestervicensis (Rosaceae) — its hybrid origin revealed by DNA fingerprinting. — Nord. 3. Bot. 1.5: 237–242. Copenhagen. ISSN 0107-055X.
The large number of species in Rubus subgenus Rubus are thought to have arisen, at least in part, through hybridiation between facultatively apomictic species. R. vestervicensis is known only from a small island off the Swedish east coast. It has been suggested that it is a hybrid between R. grabowskii and R. pedemontanus . We have compared these species with DNA fingerprinting and our results support the hybridization hypothesis. All bands found in the fingerprint of R. grabowskii and about half of the bands found in R. pedemontanus were present in R. vestervicensis , suggesting that the latter species was derived from fertilization of an unreduced R. grabowskii egg cell with R. pedemontanus pollen.     

Leaf habit does not predict leaf functional traits in cerrado woody species

Plant species with a high leaf life span (LLS) commonly have a low specific leaf area (SLA), leaf nitrogen per unit mass (N), and phosphorous concentration (P), whereas species with low LLS have a high SLA, N and P. However, LLS tends to be longer in species growing in low-nutrient soils and, therefore, differences in LLS and other leaf traits may not be consistent with a plant classification according to leaf habit. Here we investigated whether leaf habit is consistent with leaf economic spectrum trade-offs in cerrado (a Neotropical savanna) woody species. We analyzed the SLA, N and P of 125 woody species with a distinct leaf habit (deciduous, semideciduous, brevideciduous or evergreen). We also gathered data on the LLS (33 species), maximum net photosynthesis per leaf area (A_area, 56 species) and per leaf mass (A_mass, 31 species), comprising the most extensive database analyzed so far for the cerrado. Differences among leaf habit groups were tested using generalized linear mixed models and ANOVA. We did not find differences in SLA and N among species with a distinct leaf habit, but deciduous species had a higher leaf P concentration than evergreens. Species did not differ in LLS and A_mass, but A_area varied among groups. Semideciduous species had higher A_area values than deciduous and brevideciduous species, but all other groups had similar A_area values. Because of the small difference in the LLS, SLA, leaf N, leaf P and maximum net photosynthesis, we argue that deciduous, brevideciduous, semideciduous and evergreen species may not constitute different functional groups in cerrado woody species.