Comparative life history of aspidiaceous ferns in northern Japan with reference to fertility during sporophyte development in relation to habitats

The life-cycle characteristics of ferns, in particular reproductive characteristics in relation to alternation of generations, have been studied in populations of 19 species of aspidiaceous ferns native to Hokkaido. The developmental age of the sporophyte was quantitatively expressed by the number of midrib branches of the leaf (NV; number of venation). The maximum developmental age (MNV) of the aspidiaceous ferns in Hokkaido ranged from 49 to 113. The initiation of fertility (IF) in the relative developmental age (RDA), percentages of any NV to the maximum NV of the leaf population) ranged from 15 to 65%. Ferns occurring on rocky cliffs initiated fertility at 15–21%, while ferns occurring on the forest floor initiated fertility at 41–65% in the RDA of a leaf population. Further observations were undertaken on 26 ferns of other families and revealed that there were correlations between habitat and maximum NV, and habitat and IF in the RDA. Ferns occurring on cliffs, on mossy rocks and on tree trunks, had lower maximum NV of the leaf and earlier initiation of fertility in the RDA, than those of ferns occurring on the forest floor, edge of forests and on grassland in Hokkaido. Ferns occurring in the exposed habitat seemed to behave as a r-strategist, while ferns occurring in the forest floor seemed to behave as a K-strategist.     

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.     

Trade-off relationships between some reproductive characteristics in plants with special reference to life history stragegy

Several reproductive triats in plants were studied in more than 200 populations of 61 wild species from diverse ecological conditions. As a result, it was found that there occur three distinct types of plants in the energy allocation patterns to reproductive structures (RA) and the propagule output per plant (P_N), i.e. (1) the number of propagules per plant increases in response to the increase in RA (Type I), (2) the number of propagules decreases in response to the increase in RA (Type II), and (3) the RA remains constant despite the great differences in the propagule number per plant. A conspicuous trade-off relationship was also discovered to occur between the RA to a single propagule (R_A) and the propagule output per plant (P_N), such that log R_A=logC−blot P_N, or R_A=C/P_N ^b =CP_N ^−b , where C is a constant. The three different ranges ofb-values were recognized, i.e.b<1.0,b>1.0, andb=1.0, which correspond to Type I, Type II, and Type III, respectively. Related problems to the concept ofr- andK-strategy are also discussed.     

Quantitative expression of fern leaf development and fertility inPolystichum tripteron (Aspidiaceae)

To elucidate the quantitative and qualitative expression of fern development, various features of leaf-size and morphology were examined on leaves ofPolystichum tripteron (Aspidiaceae) in Japan. Among ten parameters, the number of branches of the leaf midrib (NV) proved to be the most successful for discrimination between fertile and sterile leaf populations. In the phase-change from sterile to fertile leaves, the NV parameter also gave the strongest correlation, increasing with fertility (r = 0.983), and is therefore a useful tool for research into the life history characteristics of ferns.Contribution no. 2751 from the Institute of Low Temperature Science, Hokkaido University.     

The dynamics of leaf extension in plants with diverse altitudinal ranges

Summary Rates of leaf extension have been studied with electronic auxanometers at mid-altitude in the Austrian Alps, where both low and high altitude species co-occur. The results demonstrate a clear differentiation in the temperature responses of extension between these two groups of species. For the low or mid-altitude species of Achillea millefolium, Agrostis stolonifera, Poa alpina and Rumex arifolius, the average rate of leaf extension increases from 0.1 to 0.4 mm h^-1 between 10 and 20° C. For the high-alpine species of Achillea erba-rotta ssp moschata, Poa alpina ssp vivipara and Polygonum viviparum the average rate of leaf extension was considerably lower from 0.016 to 0.064 mm h^-1, between 10 and 20° C.Leaf extension in the lowland species was not observed below an average temperature of about 5° C, whilst no limit was observed for the upland species, down to a temperature of about 0° C.In the cases of the dicotyledons that were studied, leaf plus petiole shrinkage was observed to occur, for as much as 2 to 4 h, during periods of high water vapour pressure deficits. This response was not observed for the monocotyledons.The observations of leaf extension show that daily totals of extension in species from high altitudies will be much less sensitive to day, to day variations in local climate than will the species from low altitudes. The lowland species will have higher rates of extension during clear and warm weather conditions but lower rates in cold, cloudy weather.     

Comparative life histories in the genera Calanus and Neocalanus in high latitudes of the northern hemisphere

At least nine species of Calanidae occupy the area of interest, four in the Atlantic and five in the Pacific. All store wax esters and probably can undergo diapause. Latitudinally overlapping or onshore — offshore associations of two or more species occur in both oceans. Interzonals, with reduced mouth parts in the adult female, are endemic to the Pacific subarctic gyre where their life cycles are completed in one year. Presumably its nearly closed circulation and environmental stability have favored the evolution of endemic species well adapted to those conditions. Lack of ice- and/or salinity-induced stability also limits blooms there. The sub-arctic Atlantic contains several smaller oceanographic features, open to both arctic and Atlantic influences and populated by species of different origins, arctic species can behave as interzonals but may also require two or more years to complete their life cycles. Females may need to feed one year to reproduce the next and therefore they retain functional mouthparts. In some places in the North Atlantic, blooms may start in the sub-ice zone and seed the remaining euphotic zone. There the earliest stages of some the Calanus species can develop close to the ice, using primarily ice algae as food, while the remaining stages are adapted to utilize brief periods of intense primary production in the water column. Salinity-induced stability and shallow water favor blooms in the boundary waters of both oceans, which may be of greater importance in the Atlantic because of the proportionally greater area of continental shelf there. In both oceans the smaller species of Calanidae can produce up to three generations per year.     

Demography and life history of free-rangingPropithecus diadema edwardsi in ranomafana national park,madagascar

I conducted the first long- term study of the life history patterns of Propithecus diadema edwardsi—Milne- Edward’s sifaka— in the rain forests of southeastern Madagascar, beginning in 1986. I report behavioral observations on a total of 33 individuals from three groups over a 9- year span. We captured,marked, and released 21 individuals. Individual group size ranged from three to nine sifakas. Two breeding females lived in groups I and II until 1993. A newly formed group (III) had one breeding female. Age at first reproduction is 4 years for females and 5 years for males. Gestation length is 179 days (n =2). Most births occurred in June (n = 17), but infants were also born in May (n = 2) and July (n =2). Nine of 21 (43%) infants born died before the age of 1 year, and 15 (67%) died before the age of reproduction. One female bred in her natal group after the death of the resident male and the immigration of an adult male. Another two females disappeared at 4 and 5 years of age;they could have emigrated or died. All 5- to- 6- year- old males (n = 4) have emigrated from their natal groups to adjacent groups. Two have committed infanticide. Five or more individuals were killed by Cryptoprocta ferox.Despite high mortality and offspring dispersal, the number of individuals in the two main groups remained nearly the same over the 9- year study.     

Life history characteristics and distribution of Bythotrephes longimanus Leydig (Crustacea,Onychopoda) in the Biesbosch reservoirs

The diel and horizontal distributions of Bythotrephes longimanus Leydig, Leptodora kindti (Focke) and Anomopoda (cladocerans), as well as several life history parameters of each developmental stage of B. longimanus were studied in the non-stratified Biesbosch reservoirs. Anomopoda avoided the surface layer during the day only in the pelagic zone. In the surface layer near the shore, however, they were very abundant. Because densities in the pelagic zone during the day were very low, and high during the night, the population undoubtedly moved from the littoral zone or from the sediments to the pelagic. Accumulation of zooplankton at the littoral site is either the result of random dispersal or wind-induced movements. Bythotrephes' diel distribution pattern is possibly related to that of their prey, the anomopods. Leptodora mostly exhibited a normal diel vertical migration with a small amplitude. Wind most likely influenced the horizontal distribution of the zooplankton. Bythotrephes body length increased with higher temperatures, whereas spine length was constant throughout the year. Bythotrephes can already be fertile in the first developmental stage, indicating that a rapid adaptation to a favourable environment is possible. The number of parthenogenetically produced eggs per ovigerous female was higher at the start of the growing season and constant throughout the rest of the year. Relatively few resting eggs and males were found in autumn.     

Taxonomy of phyllophoroid algae: the implications of life history

The Phyllophoraceae Rabenhorst (Gigartinales) is a family that shows a great diversity of life history patterns. The three largest phyllophoroid genera, Ahnfeltia, Gymnogongrus and Phyllophora, all commercial sources of phycocolloids, show the greatest range of life history. Information from life history studies has been of significance to classification of the Phyllophoraceae at the family, generic and specific levels. In the tetrasporophyte of Ahnfeltia plicata, previously known as Porphyrodiscus simulans, tetrasporangia are zonate and borne terminally in small superficial sori in contrast to the chains of cruciate tetrasporangia characteristic of the Phyllophoraceae. A study of reproduction and life history in the type species, A. plicata, from the Atlantic concluded that the unique carposporophyte development, in conjunction with the most primitive pit-plug structure known in the Florideophycidae, justified the proposal of a new family Ahnfeltiaceae Maggs et Pueschel in the Ahnfeltiales Maggs et Pueschel. Most Pacific species of Ahnfeltia are instead phyllophoracean and closely related to Gymnogongrus. Gymnogongrus griffithsiae, the type species, forms tetrasporoblasts whereas the majority form internal cystocarps and have heteromorphic life histories. Proposals to divide the genus by life history type require further detailed morphological and ontogenetic studies of G. griffithsiae. Phyllophora species exhibit at least three different types of life history, tetrasporoblastic, isomorphic and heteromorphic, and this genus could likewise be split along these lines. At the specific level, intraspecific life history variability appears to be related to morphological variation in some species of Gymnogongrus.     

Life history characteristics ofPolystichum tripteron with special reference to its leaf venation

An intra-species comparison of the life history of various populations ofPolystichum tripteron was undertaken in Hokkaido and Honshu in Japan with respect to some leaf-size characters and fertility during sporophyte development. The developmental process of sporophytes was quantitatively estimated by counting the number of venation (NV: number of midrib branches of the leaf). The mean NV of the fertile leaves decreased slightly with increasing altitude on Mt. Teine near Sapporo and with increasing latitudes from Honshu to Hokkaido. The blade length was longer at any NV in Hokkaido populations than in those of southern Honshu. Longer blade (BL) and pinna length (PL) and lesser number of pinnules of the lowest pinna (NPLP) versus NV were observed in leaf populations from Hokkaido than in those from southern Honshu. The maximum values of lowest pinna length (LPL), NV, number of costa branches (NVLP) and number of pinnule (NPLP) were larger in southern Honshu than in Hokkaido. In the course of leaf-shape formation represented by the ratio of PL to BL versus NV, the Kyoto population seemed to be more differentiated into long-lanceolate fronds than did the Hokkaido population. Initiation of fertility in the sporophyte development and the maximum NV seemed to decrease with increasing altitudes and latitudes in Japan. Contribution No. 2885 from the Institute of Low Temperature Science, Hokkaido University.     

The dynamics of leaf extension in plants with diverse altitudinal ranges

Summary The dynamics of leaf extension in five species of Poa were studied with electronic auxanometers (LVDTs) along an elevational gradient from 600 to 3200 m in the Austrian Alps. Extension rates peak at midday at all elevations and rates at 20°C are almost twice as high at low elevation as compared with those from the highest sites. The low temperature threshold for leaf extension drops by 7 K over this range of elevation, with plants from the highest sites showing some extension around freezing point. Thus, there is a substantial adaptive adjustment in response of leaf extension to declining mean temperatures with increasing altitude, which is not paralleled by known altitudinal trends of photosynthetic responses in herbaceous plants.     

A review of the life history,reproduction and phenology of Gracilaria

The basic life history of the red alga Gracilaria is of the three-phase Polysiphonia type but a number of species show deviations. Plants can bear both gametangia and tetrasporangia, either on separate parts of the thallus or on the same. Explanations include the in situ germination of tetraspores (allowing gametophytic thalli to be epiphytic on tetrasporophytes), the coalescence of spores or developing discs (resulting in chimaeras), mitotic recombination during cell division in the mature diploid thallus (resulting in patches of diploid male and female cells on the tetrasporophyte), a mutation eliminating the repression of female expression allowing haploid male plants to be bisexual and initial failure of cell walls to form during the development of tetraspores. Polyploids can be produced from plants with diploid gametangia. The sexes and phases are usually morphologically identical but gametophytes or their parts may be smaller. The growth rates of the sexes may differ and diploid juveniles may survive better than haploid. Neither polyploidy nor hybridization results in superior growth. The sex ratio is probably 1:1 but females may appear to be more abundant. Diploid and haploid phases are usually either about equal or diploids predominate, often depending on the type of substratum. At high latitudes reproduction peaks in late summer whereas in the tropics it may be high all year. In temperate regions growth rate is fastest and biomass highest in late summer; in the tropics peak biomass is mainly in the winter. Spermatia are effective for only a few h. Spores vary in size around 25 m, diploid ones usually being larger. Cystocarps or tetrasporangia in the field may not currently be releasing spores. In the laboratory spore release shows a diurnal rhythm, peaking during the night or day according to the species. All the above attributes are potentially important in planning and executing Gracilaria cultivation.     

Differential reattachment capacity of isomorphic life history phases of Gelidium sesquipedale

Vegetative reproduction is an important phenomenon in the propagation of Gelidium species, having significant implications for its ecology and commercial cultivation. This work is an experimental study of one of five sequential processes included in the vegetative propagation of Gelidium sesquipedale: the reattachment of rhizoidal filaments differentiated from apical fragments.Two different factors: light (25 µmol m^–2 s^–1 and long-day conditions, and 50 µmol m^–2 s^–1 and short-day conditions) and life history phases (female gametophytes and tetrasporophytes) were combined in a 2 × 2 factorial experiment. Reattachment of apical portions was induced in the laboratory under spray cultivation conditions and occurs mainly at the first stage of development when in contact with the substratum. Light conditions in these experiments (photoperiod + instantaneous photon flux densities) had no effect on the percentage of reattached neofilaments per fragment. Significant differences between percentages corresponding to both phases suggest, however, a probable competitive advantage of sporophytic fronds.     

Abundance and life history ofNeomysis intermedia Czerniawsky in Lake Kasumigaura

Weekly observations ofNeomysis intermedia in Lake Kasumigaura showed two major peaks in abundance during spring and autumn (more than 10⁴ individuals m^–2) and minimum levels in summer and winter (less than 10³ individuals m^–2). Their increase in abundance followed a high egg ratio, suggesting that the increase in abundance was caused by a high reproductive rate. Major contributors to mysid population decreases include fish predation and commercial fisheries, and possible horizontal migration of the mysids. N. intermedia showed two types of life history in the lake. One type (overwintering generation) has a life span of about 6–7 months and produces about 27 eggs per brood. Another, appearing from spring to autumn, matures in 3–6 weeks at a smaller size, and produces 12 eggs per brood. The reproductive season ofN. intermedia was continuous from March through November.     

The life history parameters of Diaphanosoma excisum (Cladocera), grown in different culturing media

Life history parameters of Diaphanosoma excisum (SARS) were derived from culture tube experiments with media comprising mohua oil cake, mustard oil cake, cow dung and rice bran. Body length, longevity, fecundity and progeny production were highest in rice bran medium. First reproduction time (A) in different media ranged from 2 to 6 days, while the reproduction peak (T) varied from 4 to 13 days. The total offspring per female (S) was directly dependent upon the mean number of eggs per female per life span. The intrinsic (r) and finite rate (e^r) of natural increase were larger for rice bran than for other media.     

Predator-induced phenotypic plasticity in Daphnia pulex: uncoupling morphological defenses and life history shifts

Chemical cues from a predator Chaoborus sp. induce morphological defense (neck spine) and life history shifts (later reproduction, decreased fecundity but larger juvenile size) in the waterflea Daphnia pulex. These shifts have been interpreted either as costs of defense or as separate adaptation. In order to investigate if the life history shifts can be separated from the morphological defense, Daphnia pulex individuals were exposed to chemical cues from Chaoborus at different stages of life for variable periods. The daphnids that were exposed to Chaoborus started their reproduction later than the controls, although the differences were not statistically significant. Neck spine was induced only if daphnids were exposed to Chaoborus in an early stage of their life. Numbers of eggs produced were not affected by the different treatments, but egg mortality was higher in mothers exposed to Chaoborus. With these treatments it was possible to see neck spine induction without measurable life history changes or costs. On the other hand, irrespective of neck spine presence, the Chaoborus chemical(s) had an effect on Daphnia pulex mothers.Publication no 2159. Netherlands Institute of Ecology, Centre for LimnologyPublication no 2159. Netherlands Institute of Ecology, Centre for Limnology     

Interannual growth response of Norway spruce to climate along an altitudinal gradient in the Tatra Mountains, Poland

Ring-width chronologies of Picea abies (L.) Karst. from ten sites in the Tatra Mountains, Poland, were developed to explore growth/climate responses in stands along an altitudinal gradient ranging from 839 to 1468 m a.s.l. There were positive relationships between current-year radial growth and mean monthly temperatures in March, April, June and July, but with increasing elevation, the strength of this correlation declined for March–April and increased for June–July temperatures. The mean monthly temperature in October of the previous year positively influenced radial growth of trees at all sites. Lower mean temperatures in January negatively affected growth of trees at the high-elevation sites. Trees at the low-elevation sites responded positively to a warm early spring, whereas trees at the high-elevation sites showed positive growth responses to higher summer temperatures. Growth of trees at the high-elevation sites was better explained by the temperature regime than was growth at the lower-elevation sites. Therefore, it is likely that these sites may be particularly sensitive to potential effects of temperature change.     

Trophic links,nutrient fluxes,and natural history in the Allium ursinum food web,with particular reference to life history traits of two hoverfly herbivores (Diptera: Syrphidae)

The food web centering on Allium ursinum (Liliaceae) in a beech forest (Germany) is described, and temporal variation of active trophic links is related to species' life cycles. The most important insect herbivores are Cheilosia fasciata (a larval leaf miner) and Portevinia maculata (a larva bulb miner) (Diptera: Syrphidae). Energy, carbon and nitrogen flow in the food chain (Allium-Cheilosia-Phygadeuon ursini) are investigated and analysed with respect to differences in resource allocation by the leaf miner and its hymenoptereous parasitoid. In C. fasciata nitrogen is likely to be the limiting resource, while growth in Phygadeuon ursini appears energy-limited. Larval feeding habits of C. fasciata and Portevinia maculata determined the timing of the species' life cycles and, as a consequence, appeared to preclude the existence of a pupal parasitoid in Portevinia maculata. Further details of life history traits are demonstrated and discussed.     

Specificity of predator-induced neck spine and alteration in life history traits in Daphnia pulex

It has been proposed that the predator-induced defensive neck spine in Daphnia pulex has a demographic cost. Our results show that this cost is not merely an allocation cost related to the formation and maintenance of the neck spine. In a life table experiment, we tested whether spine induction and life history traits in D. pulex are affected by different invertebrate predators: first and third instar Chaoborus, fourth instar Mochlonyx and two size classes of Notonecta and Dytiscus larvae. D. pulex showed sensitivity to the different predators. Predator-exposure affected one or more of the following life history traits of D. pulex: the timing of first reproduction, clutch size, and growth. In some cases, exposure to predators altered life history traits when neck spine induction did not occur. These shifts in life history traits occurring in the absence of spine induction may be caused by behavioral or physiological changes triggered by the predators.     

Some observations on the distribution and life history of Caenis robusta Eaton (Ephemeroptera) in Cheshire and North Shropshire,England

Caenis robusta Etn. was found in only 8 of 107 water bodies sampled. All the habitats from which it was recorded contained plant debris; the waters were still or slow-flowing and had conductivities ranging from 120–687 µmhos cm^–1 at 25°C.In North Shropshire, England, C. robusta had one generation per year. Newly hatched nymphs were abundant in August and growth occurred rapidly until September. No growth took place from October until March but was again rapid from April until June. Emergence took place at dusk in late June and July.