Phytotoxic effect of bioactive compounds isolated from Myrcia tomentosa (Myrtaceae) leaves

The aim of this study was to assess the phytotoxic potential of leaves of Myrcia tomentosa, as well as to isolate and identify the main bioactive compounds. The results for the coleoptile and phytotoxicity bioassays indicated the ethyl acetate extract for the phytochemistry study, owing to the high activity and the maintenance of the activity at lower concentrations. This extract was chromatographed and subjected to ¹H NMR and ¹³C NMR. Two major active compounds were isolated from the ethyl acetate extract of leaves of M. tomentosa: avicularin and juglanin. The fractions where these compounds were isolated showed potent inhibition of coleoptile growth. This paper is the first report on the presence of the flavonoids avicularin and juglanin in species of Myrtaceae from Neotropical savanna and provides a basis for future studies on the bioprospecting of M. tomentosa.     

Reproductive ecology of Naididae (Oligochaeta)

Asexual reproduction is employed by species of Naididae during favorable environmental conditions. In species characteristic of aquatic habitats subject to rapid fluctuations in water levels and temperatures most individuals in a population become sexually mature, and there is degeneration of the alimentary tract, a shortened breeding season, and aclitellar formation of cocoons. Cocoon deposition allows a population to survive periods of environmental stress. Sexual reproduction predominates near the edges of ranges where stress conditions are more prevalent. Species that reproduce sexually in spring are intolerant of summer conditions, while those that breed in autumn are intolerant of winter. Species typical of environmentally stable bodies of water usually have a minority of the population mature at any time, an extended breeding season, and the ability to continue feeding while mature; thus, adaptations for survival in unstable habitats are lacking.     

IBA与NAA对桃金娘扦插繁殖的影响

采用二元二次回归通用旋转组合设计,探讨植物生长调节剂IBA、NAA对桃金娘Rhodomyrtus tomentosa扦插生根的影响。结果显示,适宜浓度的IBA和NAA有利于桃金娘的扦插生根,IBA对生根率、根长和根重的影响更为明显。最佳浓度组合为IBA、NAA各100 mg·L~(-1),用该组合处理插条,可有效地提高扦插繁殖的成活率及幼苗质量。     

Anti Propionibacterium acnes activity of rhodomyrtone, an effective compound from Rhodomyrtus tomentosa (Aiton) Hassk. leaves

Propionibacterium acnes have been recognized as one of the main causative agents in pathogenesis of acne. Twenty one isolates of P. acnes isolated from acne lesions were screened for lipase and protease activity which are reported to be associated in acne and inflammation. Interestingly, all P. acnes isolates demonstrated lipase activity. Similarly, 90% of test P. acnes produced protease enzyme. Antibacterial activity of the ethanol extract of Rhodomyrtus tomentosa (Aiton) Hassk. leaves and rhodomyrtone, its principle compound were tested against P. acnes using broth macrodilution method. The MIC(90) values of the ethanol extract and rhodomyrtone were 32 and 0.5 μg/mL, respectively. The numbers of the bacterial cells were reduced at least 99% after treatment with the ethanol extract and rhodomyrtone within 72 and 24 h, respectively. Cytotoxicity test of the extract and rhodomyrtone was performed on human normal fibroblast. The IC(50) values of the ethanol extract and rhodomyrtone were 476 and more than 200 μg/mL, approximately 15 and 400 folds higher than the MIC(90) values indicating that both substances were very low cytotoxic which could be applied as topical therapeutic anti-acne agents.     

Rhodomyrtone: A new candidate as natural antibacterial drug from Rhodomyrtus tomentosa

Rhodomyrtone [6,8-dihydroxy-2,2,4,4-tetramethyl-7-(3-methyl-1-oxobutyl)-9-(2-methylpropyl)-4,9-dihydro-1H-xanthene-1,3(2H)-di-one] from Rhodomyrtus tomentosa (Aiton) Hassk. displayed significant antibacterial activities against Gram-positive bacteria including Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Streptococcus gordonii, Streptococcus mutans, Streptococcus pneumoniae, Streptococcus pyogenes, and Streptococcus salivarius. Especially noteworthy was the activity against MRSA with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) ranging from 0.39 to 0.78 μg/ml. As shown for S. pyogenes, no surviving cells were detected within 5 and 6 h after treatment with the compound at 8MBC and 4MBC concentrations, respectively. Rhodomyrtone displays no bacteriolytic activity, as determined by measurement of the optical density at 620 nm. A rhodomyrtone killing test with S. mutans using phase contrast microscopy showed that this compound caused a few morphological changes as the treated cells were slightly changed in color and bigger than the control when they were killed. Taken together, the results support the view that rhodomyrtone has a strong bactericidal activity on Gram-positive bacteria, including major pathogens.     

Reproductive ecology of the basal angiosperm Trithuria submersa (Hydatellaceae)

Background and Aims

Trithuria, the sole genus in the family Hydatellaceae, is an important group for understanding early angiosperm evolution because of its sister relationship to the ancient lineage, Nymphaeales (water lilies). Although also aquatic, Trithuria differs from water lilies in that all species are extremely small, and most have an annual life form and grow in seasonal wetlands. Very little is known about their reproductive ecology. This paper reports on reproductive timing, mode of pollination and characteristics of the breeding system of Trithuria submersa in Western Australia.

Methods

Mass collections of open-pollinated plants from different ecological settings were used to characterize the reproductive developmental sequence and natural pollen reception. Hand-pollination, caging and emasculation experiments were used to measure outcross + geitonogamous pollen reception versus autonomous self-pollination in two populations over two field seasons.

Key Results

Natural outcross or geitonogamous pollination was by wind, not by water or insects, but pollen reception was extremely low. Pollen production was very low and pollen release was non-synchronous within populations. The pollen to ovule (P/O) ratio was 23·9, compared with 1569·1 in dioecious Trithuria austinensis. Stigmas became receptive before male phase and remained so until anthers dehisced and autonomous self-pollination occurred. Natural pollen loads are composed primarily of self pollen. Self- and open-pollinated plants had equivalent seed set (both >70 %). Self-pollinated plants produced seed within 17 d.

Conclusions

Autonomous self-pollination and self-fertilization are predominant in T. submersa. The low P/O ratio is not an artefact of small plant size and is inconsistent with long-term pollination by wind. It indicates that T. submersa has evolved a primarily autogamous breeding system. Selfing, along with the effect of small plant size on the speed of reproduction, has enabled T. submersa to colonize marginal ephemeral wetlands in the face of unpredictable pollination.     

Reproductive ecology of the three Nordic Pinguicula species (Lentibulariaceae)

Reproductive ecology (pollination biology, breeding systems, and reproductive effort and success) of the three Nordic species of Pinguicula, P. alpina, P. villosa , and P. vulgaris (Lentibulariaceae), was investigated in a subarctic-subalpine area at Abisko, N Swedish Lapland. Additional studies were carried out at Latnjajaure Field Station, a subarctic-alpine tundra site in the Abisko mountains ( P. alpina, P. vulgaris ), and in W Greenland ( P. vulgaris ). At Abisko the species are sympatric and large populations of all three were found within a 50 × 50 m area. The three species are reproduc-tively isolated by internal barriers by occupying different ploidy levels. Pinguicula alpina and P. vulgaris thrive in base-rich habitats, whereas P. villosa is restricted to nutrient-poor Sphagnum bogs, but habitat separation alone is probably not sufficient to prevent illegitimate pollen flow among the species. However, results showed that there are large and consistent differences in pollination biology, flowering phenology, and breeding systems, and these factors interact to create a highly efficient reproductive isolation at all levels, pre-zygotic as well as post-zygotic. Pinguicula alpina is an early-flowering outbreeder, P. vulgaris is an opportunistic late-flowering inbreeder, and P. villosa is quite intermediate between the two extremes. The phenology-based life history strategies of the Pinguicula species were in accordance with a general model developed for arctic flowering plants, predicting maximized fitness through pollen or seed in early- and late-flowering species, respectively.     

Reproductive biology and ecology of female polar bears (Ursus maritimus)

Data on age-specific natality rates, litter size, interbirth interval, age of first reproduction, reproductive senescence, age of weaning and cub survival were determined for a free-ranging population of polar bears inhabiting Hudson Bay, Canada, near the southern limit of the species range. Serum progesterone levels were also determined for females at different stages of their reproductive cycle to provide corroborative support for the reproductive parameters described. Animals were live captured using immobilizing drugs and each animal uniquely marked for future identification. First parturition occurred at four or five years of age and the age-specific natality rate increased with age until approximately 20 years, after which it dropped markedly. At least 40% of adult females displayed two-year interbirth intervals and 55% of cubs in their second year were independent of their mother. Mean size of cub litters in spring was 1.9 and 13% of litters had three or more cubs. The natality rate for 5–20-year-old females was estimated as 0.9, higher than that reported for any more northerly polar bear populations where two-year interbirth intervals are rare, fewer than 5% of yearling cubs are weaned and triplet litters occur with less than 1% frequency. Cub mortality was initially high and declined with age. Although cubs in western Hudson Bay were weaned at a younger age and a lighter weight than their counterparts in more northern populations, cub mortality rates were similar. The reason for the marked differences in reproductive parameters in the western Hudson Bay population is not known. We speculate that sea-ice conditions may be sufficiently different to allow weaned bears at a lighter body weight to hunt seals more successfully there than further north.     

Myrcianthes (Myrtaceae) in Chile

The new combinationMyrcianthes coquimbensis is proposed, based onMyrtus coquimbensis. The species is described and its relationships and nomenclatural history are discussed.     

Reproductive ecology of the striped bitterling Acheilognathus cyanostigma (Cyprinidae: Acheilognathinae)

The reproductive ecology of the striped bitterling Acheilognathus cyanostigma was investigated in a small pond in Mie Prefecture, central Honshu, Japan. A. cyanostigma was the only species of bitterling in the study pond, where only a single species of mussel Anodonta woodiana was present. Spawning of A. cyanostigma was recorded between early April and early July, peaking between late April and mid-June in 2003. Ovipositor length during the spawning period ranged from 19.2 to 42.8 mm, and was positively correlated with female body length, but did not show significant seasonal variation. The eggs are elliptical with a volume of approximately 1.5 mm³. Egg size correlates positively with female body size, and both egg shape and volume changed significantly with season. The embryos were located on host mussel gills approximately 30 mm from the exhalant siphon and were found more frequently on the inner rather than the outer mussel gills. The possible ecological significance of these observations is discussed in the context of the adaptations of A. cyanostigma for utilizing mussels for oviposition.     

Reproductive ecology of predaceous Heteroptera

Reproductive ecology entails relating the physiology and behavior of an organism to its environment and the community in which it lives. Terrestrial predatory Heteroptera (including Anthocoridae, Geocoridae, Miridae, Nabidae, Pentatomidae, Phymatidae, and Reduviidae) display a wide range of reproductive ecologies. But in spite of this variability, a review of the literature reveals certain underlying trends that are useful in understanding how generalist predators function within their environments. First, the reproductive ecology of predatory bugs is inherently coupled to the physiology of the female and her eggs. Second, three population parameters are directly tied to reproduction (maturation rates, realized fecundity, and reproductive diapause) have great bearing on the rate of population increase and reproductive success of a predatory bug, but these three parameters fluctuate widely within and among species. The variables that affect these processes include the physiological status of the mother (mating status, age and size, and nutritional status), the abiotic environment in which she and her eggs live (temperature, photoperiod, water availability), and natural enemies that attack eggs and reproductive females. A final trend observed in the literature involves the hierarchy of events that must occur before a female finds a suitable oviposition site. Females all must locate preferred habitats, plants/substrates, and microsites in which to insert or deposit an egg, but they use a variety of tactics and cues in order to accomplish this, depending on their life history traits. Examining the factors that constrain and promote the reproductive potential of predatory Heteroptera will make biological control programs that center on them more reliable and sustainable.     

Reproductive assurance and the evolutionary ecology of self-pollination in Clarkia xantiana (Onagraceae)

The reproductive assurance hypothesis posits that selection favors self-pollination in flowering plants where mates and/or pollinators are scarce. A corollary is that self-pollinating populations are expected to be superior colonizers of mate- and pollinator-scarce environments. The California annual Clarkia xantiana includes outcrossing populations (ssp. xantiana) and autogamously self-pollinating populations (ssp. parviflora). Outcrossing is ancestral, and the subspecies have parapatric distributions with a narrow contact zone. We tested aspects of the reproductive assurance hypothesis by examining geographic and subspecies variation in the densities of mates and pollinators (native bees) and the density dependence of pollinator visitation and pollen receipt. Plant and flower densities, pollinator density, and pollinator visitation rates were lowest in the region of exclusively self-pollinating populations. Pollinator assemblages there lacked Clarkia-associated pollinator taxa that were common elsewhere. Self-pollinating populations in the contact zone generally had densities and visitation rates intermediate between allopatric self-pollinating populations and outcrossing populations. Visitation rate and pollen receipt increased significantly with plant density. These findings suggest that selection for reproductive assurance influenced the origin of self-pollination and/or that reproductive assurance influenced the geographic distribution of self-pollination. Geographic variation in pollinator assemblages may have generated variation in the value of reproductive assurance.     

Reproductive ecology of Cneorum tricoccon L. (Gneoraceae) in the Balearic Islands

This paper examines some aspects of the reproductive biology of Cneorum tricoccon L. (Cneoraceae), a Mediterranean relict shrub which evolved under tropical conditions during the Tertiary. The breeding system, the flowering and fruiting phenology, and the variability in fecundity within and among populations of this plant were examined in the Balearic Islands. The plant is andromonoecious, and pollen from male flowers appeared to be more fertile than pollen from hermaphrodite flowers. There was no limitation of pollen, and xenogamous crosses produced more fruit than geitonogamous ones. The efficiency of male flowers suggests that their use increases plant fitness, thus maintaining such a breeding system. Flowering time is unusual compared with other species in the habitat; there is synchrony among individuals, and flowers are produced almost continuously from November through June. Floral sex ratio (number of hermaphrodite flowers: total number of flowers) varied greatly both through the flowering season and between years and was not consistent through time, suggesting that sex expression may be determined more by factors such as resource status of the plant than by genetic factors. Fully developed fruits are observed from December to July. Fecundity varied among individuals depending upon plant size and was consistent during the three years of the study (1992–1994). Fruit crop also differed strongly among sites. The greatest, most vigorous and thus most fecund plants are found in some populations of Mallorca island, especially at high altitudes. In other Balearic islands with low altitudes (<200 m), such as Cabrera, individuals are always short, less leafy and less fecund.     

Reproductive ecology of Cneorum tricoccon L. (Cneoraceae) in the Balearic Islands

This paper examines some aspects of the reproductive biology of Cneorum tricoccon L. (Cneoraceae), a Mediterranean relict shrub which evolved under tropical conditions during the Tertiary. The breeding system, the flowering and fruiting phenology, and the variability in fecundity within and among populations of this plant were examined in the Balearic Islands. The plant is andromonoecious, and pollen from male flowers appeared to be more fertile than pollen from hermaphrodite flowers. There was no limitation of pollen, and xenogamous crosses produced more fruit than geitonogamous ones. The efficiency of male flowers suggests that their use increases plant fitness, thus maintaining such a breeding system. Flowering time is unusual compared with other species in the habitat; there is synchrony among individuals, and flowers are produced almost continuously from November through June. Floral sex ratio (number of hermaphrodite flowers: total number of flowers) varied greatly both through the flowering season and between years and was not consistent through time, suggesting that sex expression may be determined more by factors such as resource status of the plant than by genetic factors. Fully developed fruits are observed from December to July. Fecundity varied among individuals depending upon plant size and was consistent during the three years of the study (1992–1994). Fruit crop also differed strongly among sites. The greatest, most vigorous and thus most fecund plants are found in some populations of Mallorca island, especially at high altitudes. In other Balearic islands with low altitudes (<200 m), such as Cabrera, individuals are always short, less leafy and less fecund.     

Reproductive ecology of five sympatric Agave Littaea (Agavaceae) species in central Mexico

We studied a community of Agave species that coexist in the Metztitlán Canyon in Central Mexico. During 2001, 2002, and 2003, we analyzed floral traits and rosette allometry in five species belonging to the subgenus Littaea: A. celsii albicans, A. xylonacantha, A. difformis, A. striata, and Agave sp.; and observed floral visitors for each species. We report the first evidence of bat visitation in the subgenus Littaea and find that bats (Leptonycteris curasoae, Choeronycteris mexicana, and Glossophaga sp.) are the primary pollinators in four species. Honeybees, hummingbirds, bumblebees and hawkmoths were also common visitors. We propose that the presence of diurnal pollinators may increase the reproductive success of the plant when offering pollinator services additional to the coadapted pollinator. We also found evidence of selection pressures toward semelparity because pollinators are selecting for taller inflorescences in three of the five species. There is phenological complementarity in this community because the flowering periods of the five species span the entire year, although there are some periods when pairs of species overlap. Additionally, we found evidence for character displacement in rosette sizes and separation of spatial and temporal resource use in pollinator composition among species.     

Reproductive ecology of Brazilian freshwater fishes

We used metadata on nine reproductive traits of 67 species of Brazilian iteroparous, oviparous, teleost freshwater fishes to test phenotypes associations to discriminate species that only spawn in large rivers (lotic fishes) from those capable to spawn in lentic habitats (lentic fishes). We tested the hypothesis that lotic fishes present spawning migration, shorter spawning season, single spawning, no parental care, free eggs, higher relative fecundity, faster embryogenesis, and larger size, while lentic fishes present no spawning migration, longer spawning season, multiple spawning, parental care, adhesive eggs, lower relative fecundity, slower embryogenesis, and smaller size. Our analyses supported the hypothesis but not all phenotypic associations satisfied it, specifically with regard to lentic fishes or to pairs of phenotypes typical of lentic fishes. We also concluded that spawning in large rivers is a better predictor of bionomic characters than spawning in lentic habitats, and lotic fishes are specialists compared to lentic fishes.     

Reproductive ecology of Caribbean reef corals

The last decade has seen a resurgence of interest in the processes of sexual reproduction by scleractinian reef corals. Earlier investigations had focused fortuitously on brooding (planulating) species, which resulted in the general misconception that brooding was the main form of larval development of reef corals. More recent work on Indo-Pacific species has shown broadcast spawning and short annual reproductive periods to predominate. This report presents the reproductive patterns of eleven Caribbean coral species and attempts to explain the adaptive features and selective pressures that have led to the evolution of the four reproductive patterns described to date: (a) hermaphroditic broadcasters; (b) gonochoric broadcasters; (c) hermaphroditic broadcasters; (b) gonochoric brooders. Both (a) and (b) correlate with large colony size and short annual spawning periods; and (c) and (d) correlate with small colony size, multiple planulating cycles per year, and occupation of unstable habitats. Selection for outcrossing between long-lived individuals is proposed as the reason for gonochorism and for synchronous spawning of hermaphroditic broadcasters, and also for the large amount of sperm produced by hermaphroditic brooders. Selection for high rates of local recruitment is proposed as the force behind the evolution of brooding by species inhabiting unstable habitats and suffering high rates of adult mortality.