Costs of sporophyte production in the moss,Dicranum polysetum

We investigated the cost of sporophyte production in the moss Dicranum polysetum both by examining patterns of growth and reproduction in unmanipulated shoots and by experimentally manipulating sexual reproduction.The estimated proportion of total carbon investment allocated to sexual reproduction in sporophyte-producing shoots over the study period was 74.8%. Unmanipulated shoots that aborted all sporophytes had a significantly higher growth in the top shoots than shoots that produced sporophytes. In sporophyte-producing shoots, total apical growth decreased proportionately with the number of sporophytes.Experimental prevention of sporophyte development resulted in significantly higher total apical growth of the gametophytes. Shoots where current perichaetia were lacking when marked had a mass increase in the top shoots similar to manipulated sporophytic shoots whereas sporophytic control shoots grew significantly less than these two categories.The difference between control shoots and manipulated shoots in the mass of vegetative apical growth was mainly because of different length increments whereas mass per unit length was similar between groups. The probability to reproduce sexually in the year after the manipulation, and the biomass allocated to this reproduction, were not affected by the experimental treatment.     

Age and size at maturity in mountain and lowland populations of the expanding moss <Emphasis Type="Italic">Pogonatum dentatum</Emphasis>

The moss Pogonatum dentatum has expanded its distribution in Fennoscandia from mountainous areas into the lowlands. This recent expansion appears to be associated with changes in important life-history parameters in female shoots. We examined shoot age and size at first production of sex organs and mature spores in P. dentatum to investigate this phenomenon. Female shoots produced mature spores for the first time in the lowlands in their second year but in their third year in the mountains. However, sex organs were produced by second year plants in both areas. There was no size difference between the mountain and lowland female shoots at the time of spore production. Among mountain females reproducing for the first time, 41% of the shoots branched, making them potentially ‘iteroparous’. Branching was not observed among lowland females. Male shoots showed no difference in production of sex organs, and were produced by second year shoots in both areas. Female shoots in the lowlands have earlier spore production and exhibit ‘semelparous’ behaviour by not producing branches. This suggests that the lowland phenotypes of P. dentatum are more ‘invasive’ than the mountain phenotypes. Earlier studies showing high rates of diaspore establishment in lowland areas also support this observation.     

Reproductive cycle of Pitcairnia flammea Lindl. (Bromeliaceae/Pitcairnioideae) in an insular Atlantic rainforest area in southeastern Brazil

We studied for 6 years the reproductive cycle of the bromeliad Pitcairnia flammea in the Atlantic Rainforest of Ilha Grande, an island located in the south of Rio de Janeiro state, southeastern Brazil. We marked 150 adult individuals of the species, for which we monthly observed the occurrence of reproductive characteristics. The phenological attributes were related to environmental factors such as photoperiod, rainfall and temperature. Additionally, we estimated a mortality rate that was related to the rainfall in the area. P. flammea possesses a seasonal reproduction pattern, with a relatively fixed and well-defined time span during the winter dry period; flowering precedes fruiting by approx. 1 month. Due to the occurrence of P. flammea preferably on boulders of river channels and banks mortality of the plants is highest when floods from strong rainfall remove the plants mechanically from their growing places.     

Sporophyte and gametophyte generations differ in their thermotolerance response in the moss Microbryum

BACKGROUND AND AIMS: Actively growing post-embryonic sporophytes of desert mosses are restricted to the cooler, wetter months. However, most desert mosses have perennial gametophytes. It is hypothesized that these life history patterns are due in part to a reduced thermotolerance for sporophytes relative to gametophytes. METHODS: Gametophytes with attached embryonic sporophytes of Microbryum starckeanum were exposed whilst desiccated to thermal episodes of 35 degrees C (1 hr), 55 degrees C (1 hr), 75 degrees C (1 hr) and 75 degrees C (3 hr), then moistened and allowed to recover for 35 d in a growth chamber. KEY RESULTS: All of the gametophytes survived the thermal exposures and produced protonemata, with the majority also producing shoot buds. Symptoms of gametophytic stress (leaf burning and discoloration of entire shoots) were present in lower frequencies in the 55 degrees C exposure. Sporophyte resumption of growth and maturation to meiosis were significantly negatively affected by thermal treatment. Not a single sporophyte exposed to the two higher thermal treatments (75 degrees C for 1 h and 75 degrees C for 3 h) survived to meiosis, and those sporophytes exposed to 75 degrees C that survived to the post-embryonic phenophase took significantly longer to reach this phase. Furthermore, among the thermal treatments where some capsules reached maturity (35 degrees C and 55 degrees C), maternal shoots that produced a meiotic capsule took longer to regenerate through protonemata than maternal shoots aborting their sporophyte, suggestive of a resource trade-off between generations. CONCLUSIONS: Either (1) the inherent sporophyte thermotolerance is quite low even in this desert moss, and/or (2) a gametophytic thermal stress response controls sporophyte viability.     

The relevance of life-history traits in the establishment of the invader <Emphasis Type="Italic">Eudiaptomus gracilis</Emphasis> and the extinction of <Emphasis Type="Italic">Eudiaptomus padanus</Emphasis> in Lake Candia (Northern Italy): evidence for competitive exclusion?

The niches invaded by exotic species are generally not entirely vacant, and one possible factor affecting the success of the invader to establish a permanent large population may be the ability of the former to outcompete native species. Eudiaptomus gracilis, which was not present in Italy before the 1980s, is becoming established in an increasing number of Northern Italian lakes, ultimately replacing the endemic E. padanus. Coexistence of the two species in Lake Candia lasted only 7 months, suggesting that species replacement was determined either by environmental changes or by strong competition. To assess whether the potential for interspecific competition existed and to identify species' traits which could explain the competitive superiority of E. gracilis, we examined field seasonal patterns, reproductive parameters and body size of the two species. E. padanus abundance was probably reduced by predation and parasitism, which favoured the displacement of the species shortly after invasion by E. gracilis. The temporarily underexploited niche provided an opportunity for the successful establishment of the invader. The reproductive patterns of the two species were found to be similar in most of their features, with the exception of a markedly larger clutch size and a smaller egg volume in the resident species. By contrast, the invader showed a higher adult:egg ratio and a lower death rate. Thus, despite the greater fecundity of E. padanus, the competitive success of the invader might be attributable to interspecific differences in developmental rates and/or juvenile mortality.     

Functional diversity and traits assembly patterns of lichens as indicators of successional stages in a tropical rainforest

Understanding community assembly patterns with regard to functional traits, which may be common to different species, allows us to compare ecological communities in a wider range of environmental and phytogeographic conditions. Moreover, a functional approach may facilitate the comprehension of the relation between biotic changes and ecosystem functions in complex systems such as tropical forests. Considering the lack of information in relation to the influence of environmental conditions on lichen functional traits, on lichen functional patterns in tropical forests and the potential usage of this approach in bioindication studies, this paper aims at (i) determining the functional structure of the lichen communities along the forest succession gradient, (ii) assessing the relation of lichen functional traits to this gradient and (iii) verifying the potential of using lichen functional traits as indicators of successional stages in tropical rainforests. Lichens were sampled in 24 sampling units of three successional stages (6–10; 12–20; and 40–60 years of recovering). The results corroborated our main hypothesis that the functional structure of the lichen communities responds to structural changes along a forest regeneration gradient. Growth forms (foliose, fruticose and crustose) as well as some reproductive trait states (lirella, isidia and perithecia) were the most suitable lichen traits to be used as indicators of forest succession in the southern edge of the Atlantic Rainforest. Lirella, fruticose and foliose were more related to earlier successional stages; isidia was more related to intermediate stages, while perithecia and crustose were more related to older stages. These results reinforce the ability of lichens to be used as bioindicators of forest conditions.     

Genetic correlations between production and semen traits in pig

Genetic correlations between production traits (average daily gain from birth till the end of the field test and ultrasonically predicted lean meat content at the end of the field test) and semen traits (semen volume, sperm concentration, motility, percentage of abnormal spermatozoa, total number of spermatozoa and number of functional spermatozoa) were estimated from a large dataset (44 500 observations for production traits and more than 150 000 ejaculates from 2077 boars). The boars belonged to the breeds Duroc, Piétrain and Large White or were crossbreds between them. All estimated genetic correlations were low (maximal absolute value 0.13). Therefore, selection on production traits is expected to have only low effects on semen traits.     

海南岛热带低地雨林群落水平植物功能性状与环境因子相关性随演替阶段的变化

以功能性状为基础的方法可以用来探讨植物群落中功能性状如何响应环境并揭示植物生态策略的潜在驱动力,但有关功能性状与环境因子之间的关系随植物群落演替变化的研究仍然匮乏.作者以海南岛热带低地雨林刀耕火种弃耕后处于不同演替阶段的次生林(包括弃耕后恢复15年、30年及60年的次生林)和老龄林为对象,通过群落学调查和对木本植物的功能性状及样地环境因子的测定,分析了群落水平植物功能性状与环境因子关系随演替阶段的变化规律.结果表明,随着演替的进行,林冠开阔度、土壤养分、比叶面积、叶片氮含量、叶片磷含量和叶片总有机碳含量逐渐降低,叶片干物质含量、木材密度、潜在最大高度逐渐升高,而土壤水分和叶片钾含量变化不大.多元逐步回归分析表明,影响群落水平植物功能性状的主要环境因子随演替阶段而发生显著的变化,在15年、30年和60年的次生林及老龄林中,对群落水平植物功能性状影响最大的环境因子依次为土壤有机质和pH值、林冠开阔度和土壤总磷含量、土壤总钾和有效磷含量,以及土壤有机质含量和磷含量.同一功能性状在不同演替阶段受到不同环境因子的控制,同时各功能性状又能够对不同演替阶段所处的特殊环境产生一定的适应性.     

Light requirements of Australian tropical vs. cool-temperate rainforest tree species show different relationships with seedling growth and functional traits

Background and Aims

A trade-off between shade tolerance and growth in high light is thought to underlie the temporal dynamics of humid forests. On the other hand, it has been suggested that tree species sorting on temperature gradients involves a trade-off between growth rate and cold resistance. Little is known about how these two major trade-offs interact.

Methods

Seedlings of Australian tropical and cool-temperate rainforest trees were grown in glasshouse environments to compare growth versus shade-tolerance trade-offs in these two assemblages. Biomass distribution, photosynthetic capacity and vessel diameters were measured in order to examine the functional correlates of species differences in light requirements and growth rate. Species light requirements were assessed by field estimation of the light compensation point for stem growth.

Results

Light-demanding and shade-tolerant tropical species differed markedly in relative growth rates (RGR), but this trend was less evident among temperate species. This pattern was paralleled by biomass distribution data: specific leaf area (SLA) and leaf area ratio (LAR) of tropical species were significantly positively correlated with compensation points, but not those of cool-temperate species. The relatively slow growth and small SLA and LAR of Tasmanian light-demanders were associated with narrow vessels and low potential sapwood conductivity.

Conclusions

The conservative xylem traits, small LAR and modest RGR of Tasmanian light-demanders are consistent with selection for resistance to freeze–thaw embolism, at the expense of growth rate. Whereas competition for light favours rapid growth in light-demanding trees native to environments with warm, frost-free growing seasons, frost resistance may be an equally important determinant of the fitness of light-demanders in cool-temperate rainforest, as seedlings establishing in large openings are exposed to sub-zero temperatures that can occur throughout most of the year.     

Coordination between leaf and root traits in Mediterranean coastal dune plants

• Plant trait-based functional spectra are crucial to assess ecosystem functions and services. Whilst most research has focused on aboveground vegetative traits (leaf economic spectrum, LES), contrasting evidence on any coordination between the LES and root economic spectrum (RES) has been reported. Studying spectra variation along environmental gradients and accounting for species' phylogenetic relatedness may help to elucidate the strength of coordination between above- and belowground trait variation.
• We focused on leaf and root traits of 39 species sampled in three distinct habitats (front, back and slack) along a shoreline–inland gradient on coastal dunes. We tested, within a phylogenetic comparative framework, for the presence of the LES and RES, for any coordination between these spectra, and explored their relation to variation in ecological strategies along this gradient.
• In each habitat, three-quarters of trait variation is captured in two-dimensional spectra, with species' phylogenetic relatedness moderately influencing coordination and trade-off between traits. Along the shoreline–inland gradient, aboveground traits support the LES in all habitats. Belowground traits are consistent with the RES in the back-habitat only, where the environmental constraints are weaker, and a coordination between leaf and root traits was also found, supporting the whole-plant spectrum (PES).
• This study confirms the complexity when seeking any correlation between the LES and RES in ecosystems characterized by multiple environmental pressures, such as those investigated here. Changes in traits adopted to resist environmental constraints are similar among species, independent of their evolutionary relatedness, thus explaining the low phylogenetic contribution in support of our results.

     

Suites of root traits differ between annual and perennial species growing in the field

Here, we tested whether root traits associated with resource acquisition and conservation differed between life histories (annuals, perennials) and families (Fabaceae, Asteraceae and Poaceae). Root topology, morphology, chemistry and mycorrhizal colonization were measured on whole root systems of 18 field-grown herbaceous species grown and harvested in central Argentina. Annuals differed from perennials in several root traits important in resource uptake and conservation. They exhibited higher specific root length (SRL), root nitrogen concentration (RNC) and mycorrhizal colonization but had lower root tissue density (RTD) than perennials. They did not differ in topology or construction cost. These differences were consistent among families. Families differed only in a few root traits known to be strongly associated with certain lineages such as topology and nitrogen concentration. There was a strong parallel between root traits and analogous leaf traits described in the literature for annuals and perennials. Our results suggest the existence at the root level of an acquisitive vs conservative syndrome consistent among families similar to that previously reported for above-ground traits.     

Field observed relationships between biodiversity and ecosystem functioning during secondary succession in a tropical lowland rainforest

The relationship between biodiversity and ecosystem functioning (BEF) is one of the most concerned topics in ecology. However, most of the studies have been conducted in controlled experiments in grasslands, few observational field studies have been carried out in forests. In this paper, we report variations of species diversity, functional diversity and aboveground biomass (AGB) for woody plants (trees and shrubs) along a chronosequence of four successional stages (18-year-old fallow, 30-year-old fallow, 60-year-old fallow, and old-growth forest) in a tropical lowland rainforest recovered after shifting cultivation on Hainan Island, China. Fifty randomly selected sample plots of 20 m × 20 m were investigated in each of the four successional stages. Four functional traits (specific leaf area, wood density, maximum species height and leaf dry matter content) were measured for each woody plants species and the relationships between species/functional diversity and AGB during secondary succession were explored. The results showed that both plant diversity and AGB recovered gradually with the secondary succession. AGB was positively correlated with both species and functional diversity in each stage of succession. Consistent with many controlled experimental results in grasslands, our observational field study confirms that ecosystem functioning is closely related to biodiversity during secondary succession in species rich tropical forests.     

Adaptive genetic differentiation in life-history traits between populations of <Emphasis Type="Italic">Mimulus guttatus</Emphasis> with annual and perennial life-cycles

The optimal allocation to sexual and vegetative reproduction as well as the optimal values of other life-history characteristics such as phenology, growth and mating system are likely to depend on the life-cycle of the organism. I tested whether plants of Mimulus guttatus originating from temporarily wet populations where the species has an enforced annual life-cycle have higher allocation to sexual reproduction, lower allocation to vegetative reproduction, more rapid phenology, faster growth, and floral traits associated with a self-fertilizing mating system than plants from permanently wet populations where the species has a perennial life-cycle. I grew a total of 1377 plants originating from three populations with an annual life-cycle and 11 populations with a perennial life-cycle in a greenhouse under permanently and temporarily wet conditions. Plants of M. guttatus in permanently wet conditions had significantly more vegetative reproduction and tended to have a faster growth than plants in the temporarily wet conditions, indicating plasticity in these life-history traits. Plants from populations with an annual life-cycle invested significantly more in sexual reproduction and significantly less in vegetative reproduction than the ones from populations with a perennial life-cycle. Moreover, this study showed that plants originating from populations with an annual life-cycle have a significantly faster development and floral traits associated with autonomous self-fertilization. In conclusion, this study suggests that there has been adaptive evolution of life history traits of M. guttatus in response to natural watering conditions that determine the life span of the species.     

Effects of inbreeding on life history and thermal performance in the tropical butterfly Bicyclus anynana

Human-induced loss and fragmentation of natural habitats reduces population size and thereby presumably genetic diversity through inbreeding or genetic drift. Additionally, many species are confronted with increased temperature stress due to climate change, with reduced genetic diversity potentially interfering with a species’ ability to cope with such conditions. While in general the detrimental impact of inbreeding has often been documented, its consequences for the ability to cope with temperature stress are still poorly understood. Against this background we here investigate the effects of inbreeding on egg hatching success, development and temperature stress tolerance in the tropical butterfly Bicyclus anynana. Specifically we test for an increased sensitivity to environmental stress in inbred individuals. Our results revealed that even comparatively low levels of inbreeding yield negative consequences for reproduction and development under beneficial conditions. Inbreeding also reduced cold tolerance in adult butterflies, while heat tolerance remained unaffected. We therefore conclude that acute stress tolerance may not be generally impaired by inbreeding.     

Association between PrP genotypes and performance traits in a Welsh Mountain flock

The UK national scrapie plan (NSP) for sheep is based on selection for the resistant ARR/ARR genotype and elimination of susceptible types of the ovine prion protein (PrP) gene. The aim of this study was to estimate the possible association of the PrP genotype and performance traits by using data from the CAMDA Welsh Mountain flock. Four alleles (ARH, ARQ, ARR and VRQ) and 10 genotypes covering all five NSP risk groups were present in the CAMDA flock. Overall, the most common allele was ARR (35.2%), and VRQ was the least common (5.4%). The commonest genotypes were ARR/ARQ (23.7%) and ARR/AHQ (23.1%). The most resistant genotype, ARR/ARR, and the most susceptible genotype, VRQ/VRQ, were found in 10.2% and 0.3%, respectively, of the population tested. The associations of PrP genotypes with weight and ultrasonically scanned traits were investigated in three analyses, the first using genotypes, the second using risk categories and the third using number of alleles. These associations were evaluated by univariate analysis of each trait using an animal model with maternal effects where appropriate, and PrP was included as a fixed effect. Selection for scrapie resistance will not adversely affect progress in the traits considered and is consistent with improvements in muscle depth.     

同期生长在种源地与异地同质园刨花楠叶性状分析

为辨别环境变化与遗传因素对植物叶片主要功能性状的影响,以同期生长在4种源地母树林下及异地同质园的1.5年生刨花楠苗木为研究对象,对其叶片表型及养分性状进行对比分析。结果显示：(1)刨花楠叶面积、叶厚、叶干物质含量等叶片表型性状受遗传与环境因素共同影响;叶片碳(C)含量受遗传因素调控,环境对其影响较小;叶片氮、磷(N、P)含量主要受环境因素影响;(2)不同种源刨花楠比叶面积、叶厚、叶干物质含量、叶形指数等性状变异系数较大(8.85%—37.03%),其中江西遂川种源变异系数相对较大,而湖南茶陵种源则相对较小,各种源都倾向于通过调节比叶面积、叶厚、叶片氮磷含量等性状以适应生境变化;(3)种源地与同质园刨花楠的比叶面积虽均与叶厚呈显著负相关,但同质园刨花楠比叶面积与叶形指数呈显著正相关,与叶片氮含量无明显相关,而种源地刨花楠比叶面积则与叶形指数无明显相关,与叶片氮含量则呈显著负相关;(4)不同种源苗木叶性状指标在种源地与同质园间存在不同的协调与权衡,体现了植物在不同生境下的适应策略。其中湖南茶陵种源在两种生境下都具有更保守的资源获取策略,而江西安福种源对环境变化则更为敏感,资源获取策略更为灵...     

Reproductive isolation and the nest sites of Lake Malawi chambo, Oveochvomis (Nyasalapia) spp.

The nest sites of chambo, Oreochromis (Nyusalupia) spp. were surveyed in the vicinity of Cape Maclear, Lake Malawi. O. karongae (Trewavas) nested at depths of 0.5 to 28 m, while O. lidole bred at depths greater than 17 m. Nesting areas overlapped between these two species. O. lidole (Trewavas) nests were generally larger than those of O. karongae . Both species bred from September to March. Contrary to previous suggestions, the two chambo species were not reproductively isolated by breeding depth, season, or beach type.     

基于土地利用变化的热带植物群落功能性状与土壤质量的关系

为了明确热带天然林转变为橡胶林和槟榔后土壤质量变化,揭示土地利用变化下植物群落功能性状对土壤质量影响。在海南中部山区,以原始林(PF)、次生林(SF)、槟榔(Areca catechu)林(AP)、纯橡胶(Hevea brasiliensis)林(RP)和橡胶益智(Alpinia oxyphylla)林(RAP)为对象,探索天然林退化后土壤性质和质量变化,分析了植物群落功能性状(凋落物量、郁闭度、根长密度、细根密度和比根长)对土壤质量影响。结果表明:1)与原始林相比,其他土地利用类型凋落物量、根长密度、细根密度、土壤总孔隙度、最大持水量、土壤有机碳和总氮显著降低,土壤容重显著增加。人工林土壤碱解氮明显降低,但总磷、总钾和缓效钾明显升高(P0.05)。2)与原始林相比,次生林、槟榔林、纯橡胶林和橡胶益智林土壤质量指数分别降低63.4%、85.8%、81.2%和84.1%,随原始林、次生林和人工林梯度土地利用强度的增加,土壤质量显著降低(P0.05),但人工林间土壤质量无显著差异。3)凋落物量、郁闭度、根长密度和细根密度均与土壤质量指数显著正相关(P0.05),细根密度对土壤质量的直接影响效应最大,凋落物间接影响效应最大。天然林转变为橡胶和槟榔林显著改变土壤性质和质量,群落性状细根密度和凋落物可较好解释土壤质量变化,强化人工林林下植被和凋落物管理有利于土壤质量改善。