The Restoration of Degraded Mountain Woodlands: Effects of Seed Provenance and Microsite Characteristics on Polylepis australis Seedling Survival and Growth in Central Argentina

South American high‐mountain ecosystems are greatly influenced by human disturbance. In the mountains of Córdoba, Argentina, Polylepis australis (Rosaceae) woodlands are currently highly fragmented and subject to extensive burning and livestock grazing, resulting in severe changes of habitat characteristics, which hamper natural regeneration. In order to find out how to achieve successful reforestation, we compared P. australis seedling survival and growth and the development of a shrubby habit for two seed provenances and different planting microsites. Survival of planted seedlings after 5 years was 70%, with most deaths (19%) in the first year and declining mortality with ongoing establishment. Survival did not show any relationship with seed provenance or microsite characteristics. Height growth averaged 34.6 ± 1.2 cm in 5 years. Seedlings produced from seeds collected in a well‐preserved woodland grew taller and showed a higher tendency for development of shrubby habit than those produced from seeds collected in a degraded woodland. Seedlings planted in more degraded microsites with exposed soil or rock due to past grazing pressure grew less and developed a more shrubby habit than those planted in better preserved microsites. Our results show that restoration of degraded areas with P. australis is possible and that there is potential to improve restoration success with a careful selection of seed provenance and planting microsites.     

Laboratory and Field Observations of the Behavior of <Emphasis Type="Italic">Eustenopus villosus</Emphasis> while Feeding and Ovipositing on Yellow Starthistle

The feeding and oviposition behavior of postdiapausal Eustenopus villosus (Boheman) on young and late stage buds, respectively of yellow starthistle, Centaurea solstitialis L., was documented in the laboratory and field. Postdiapausal adult feeding on young buds took over an hour to complete in most cases and was conducted by both sexes. Feeding bouts generally occurred in the sequence of explore, feeding, and budwalk. Oviposition included a feeding phase to prepare an oviposition cavity within the bud; thus, oviposition bouts included some of the same behavioral elements as postdiapausal feeding. The standard sequence of behavioral elements involved with oviposition included exploring, feeding, turning, ovipositing, and budwalking. The feeding element during the oviposition bout often lasted 2 h and was similar in the field and in the lab. Postdiapausal adult feeding on young capitula and stems, and larval feeding on developing ovaries and achenes, makes this weevil especially destructive on a per insect basis.     

A microhistological survey on the trees of a relict subtropical laurel forest from the Macaronesian Islands as a base for assessing vertebrate plant diet

A microhistological collection and its respective key on the leaves and fleshy fruits produced by the mostly endemic trees that integrate the relict laurel forest in the Macaronesian Islands are presented. Epidermal tissues from the adaxial and abaxial surfaces of leaves and fruits of 23 species were extracted by scraping and prepared on individual microscope slides. An optical microscope with a camera lucida fixed at magnifications of ×400 was used to analyse and to draw the morphological traits of epidermal tissues to the same scale. Furthermore, quantitative data for those congeneric species were also obtained by using an image analysis program system. The results indicate that this microhistological method permits the differentiation of practically all species of trees present in the Macaronesian laurel forest. Furthermore, most species belonging to the same taxa (genus or family) show a general common pattern in the morphology of the different epidermal traits. Lastly, despite the effort that constitutes the preparation of plant microhistological collections of a determined ecosystem, it is of basic importance because it makes possible the performance of feeding ecological studies of several herbivorous and frugivorous vertebrate species. These results provide crucial information that elucidates the functioning of the food web and energetic flux dynamics of the Macaronesian laurel forest ecosystem.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 409–426.     

The contribution of the facultative feeding period to echinoid larval development and size at metamorphosis: a comparative approach

Planktotrophic invertebrate larvae have two dissociable stages during development, a facultative feeding period, whose length is determined by the amount of maternal provisioning in the egg, and an obligate feeding period, whose length is determined by the quantity of exogenous energy needed to reach metamorphic competence. Here we set out to experimentally test the impact of feeding during the facultative feeding period at two food concentrations (limiting and nonlimiting) on larval development time and juvenile quality. We used two closely related subtropical sand dollar species that differ in the quantity of maternal investment for these comparisons: Leodia sexiesperforata (large egg, long facultative feeding period) and Mellita tenuis (small egg, short facultative feeding period). We found that feeding during the facultative period accelerates development to metamorphosis only in M. tenuis and only at the high food ration. Feeding during the facultative feeding period had no effect on development time for M. tenuis at a food limiting concentration and for L. sexiesperforata at either food concentration. Furthermore, we found feeding during the facultative period to significantly increase quantity of carbohydrates and lipids at metamorphosis only for M. tenuis in nonlimiting food concentration. Thus, our data reveal a two-fold benefit of the facultative feeding period for a poorly provisioned species under high food conditions but little effect on a well-provisioned species. We discuss our results in reference to McEdward's [McEdward, L.R., 1997. Reproductive strategies of marine benthic invertebrates revisited: facultative feeding by planktotrophic larvae. Am. Nat. 150, 48-72] facultative feeding model.     

Effects of temperature and delayed initial feeding on the survival and growth of Japanese flounder larvae

The effects of the timing of initial feeding (0, 1, 2, 3 and 4 days after yolk exhaustion) and temperature (15, 18 and 21° C) on the point‐of‐no‐return (PNR), survival and growth of laboratory‐reared Japanese flounder Paralichthys olivaceus larvae were studied under controlled conditions. The larvae reached PNR on 7·7, 5·2 and 4·2 days‐post‐hatching (dph) at 15, 18 and 21° C, respectively. At each temperature, larval growth did not differ significantly among the delayed initial feedings 1 day before PNR but decreased significantly in larvae first fed after that. In the treatments where initial feeding was equally delayed, larvae grew significantly faster at 18 and 21° C than at 15° C. The larvae survived apparently better at 15 and 18° C than at 21° C when initial feeding was equally delayed. At each temperature, survival of the larvae first fed before PNR did not differ noticeably, while delayed initial feeding after that apparently reduced their survival. These results indicated that there existed a negatively temperature‐dependent PNR in the Japanese flounder larvae. Survival and growth of the larvae strongly depended on temperature as well as the timing of initial feeding. High temperature accelerated the yolk exhaustion and growth of the larvae and thus reduced their starvation tolerance and survival. To avoid potential starvation mortality and obtain good growth, the Japanese flounder larvae must establish successful initial feeding within 2 days after yolk exhaustion at 15° C and within 1 day at both 18 and 21° C.     

Effect of delayed first feeding on development and feeding ability of Paralabrax maculatofasciatus larvae

The impact of delayed feeding early in development on late feeding ability and development of spotted sand bass Paralabrax maculatofasciatus larvae was examined. Larvae were sampled from hatching until day 19 after delayed feeding for zero (control), 1, 2, or 3 days. Feeding incidence was evaluated as the percentage of larvae with food in the gut and feeding intensity was measured by direct counting of prey after dissection of the gut. Delayed feeding effects due to starvation were observed early in development. By day 5, significant differences ( P  < 0·05) were observed between controls and larvae submitted to degrees of delayed feeding, including total length ( L _T), eye diameter, and the size of the head, liver, gut, muscles and body. Differences were still apparent in L _T, and body, liver and muscle heights at the end of the studied period. Larvae under total starvation did not survive beyond day 5. Initial feeding incidence was 35, 60, 90 and 10% for larvae first fed on day 2, 3, 4 or 5, respectively. Mean ±  s . d . feeding intensity was 3·6 ± 0·8, 2·8 ± 1·3, 5·2 ± 0·3, and 10·2 ± 1·5 rotifers per larva depending on whether larvae were initially fed on day 2, 3, 4 or 5, respectively. The point of no return occurred between 4 and 5 days after hatching.     

Trophic Levels and Functional Feeding Groups of Macroinvertebrates in Neotropical Streams

Feeding strategies are typical traits reflecting the adaptation of species to environmental conditions. This concept is currently developed in some water quality systems (e.g. Index of Trophic completeness) and the structure of functional feeding groups (FFGs) could form part of a unified measure across communities differing in taxonomic composition. However, in South America, information about the FFG classification of invertebrates in streams is almost absent and existing studies using FFG structure follows classification from North America. But even taxonomically related species may have different diets in tropical and temperate areas and therefore, studies about FFG structure in neotropics could be biased. For this reason, we determined diet composition, trophic level and FFGs, using gut contents analysis and mouthpart observations of 49 macroinvertebrate taxa (mostly at genus level) from neotropical streams. We observed that practically all macroinvertebrates fed upon fine detritus which indicates the importance of this food resource in neotropical streams. As the assignment to a single FFG does not accurately reflect the functional profile of taxa, we transcribed the affinity of taxa to each FFG using fuzzy codes. Finally, we published the coding of diet composition and FFG of the taxa examined, which could be used in future community analyses of lotic ecosystems in the Neotropical zone.     

Temporal and Spatial Distribution Patterns of Larval Trichoptera in Madeiran Streams

Temporal and spatial distribution patterns of lotic larval trichopteran assemblages in relation to environmental variables were investigated in Madeiran streams using multivariate analyses. TWINSPAN classification detected distinct faunal assemblages related to spatial factors between non-polluted high altitude sites and lower lying enriched sites where tolerant taxa were predominant but showed strong seasonal shifts in species composition and abundance. The 15 TWINSPAN end groups were grouped into five arbitrary clusters based upon the seasonal and spatial changes in the trichopteran assemblages detected by the analysis. Significant differences between environmental variables (distance from source, altitude, temperature, conductivity, alkalinity and nitrate) and the trichopteran assemblages (using trichopteran based metrics) of these clusters were confirmed by the Kruskal-Wallis test (H) and Dunn’s test. Chemical classification of samples within the clusters revealed a strong association between trichopteran assemblages and water quality. Canonical Correspondence Analysis and Monte Carlo global permutation tests also identified significant associations between the larval assemblages and physicochemical variables such as temperature and conductivity along a strong physical gradient (altitude, slope) and nitrate along a weaker seasonal gradient. Analysis of functional feeding group distribution patterns clearly showed that mid to high altitude indigenous woodland sites were trophically diverse whilst the lower reaches of the islands streams are trophically impoverished with strong seasonal shifts between two feeding groups of enrichment tolerant taxa. Trichopteran shredders are exclusive to indigenous woodland sites, indicating a limited distribution associated with land use, allochthonous input and habitat destruction. The results indicate that several ‘environmental filters’ operate at different levels upon the islands trichopteran fauna, producing temporally and spatially distinct ‘subsets’ of species best able to exploit conditions and resources at a given site or time, confounding the direct comparison of these insular systems with the findings of the River Continuum Concept, traditionally associated with unaffected continental lotic systems.     

Modelling Effects of Temperature and Feeding Level on the Life Cycle of the Midge Chironomus Riparius: An Energy-Based Modelling Approach

Survival, growth, emergence and reproduction were monitored during the life cycle of Chironomus riparius in the laboratory at five temperatures from 15 to 27 °C and two feeding diets (ad libitum and limiting). Data were analysed using an energy-based model. Survival was not affected. In ad libitum conditions, growth rate increased linearly with temperature as a consequence of quicker food ingestion. Our model parameterised using the data in ad libitum conditions could account for the data obtained in food limited conditions. Reproduction was not influenced by temperature because the decrease of the duration of the period of energetic investment into reproduction compensated for the increase of the feeding rate when temperature increased. Based on these results, we then built a model describing life cycles in the field which may contribute to the field assessment of the consequences of global warming or pollution.     

连翘花的结构与繁育系统研究

通过定株观察、解剖和人工套袋交叉授粉试验对连翘花的生长发育和繁殖系统进行研究.结果表明:(1)连翘具有2种避免自交的方式,雌雄异位和雌雄异熟.其雌雄异位表现为长雄蕊短雌蕊花型和短雄蕊长雌蕊花型;雌雄异熟表现为长雄蕊短雌蕊花型为雄蕊先于雌蕊成熟,短雄蕊长雌蕊花型表现为雌蕊先于雄蕊成熟.(2)连翘花P/O值测定和户外套袋交叉授粉试验显示,P/O值为2 000±300;不同类型花的异花授粉结果率在50.64%~80.32%,其中短型花的花粉授到长型花柱头的结果率最高,达80.32%,而长型花和短型花的同型花授粉结果率分别为2.92%和34.15%,表明连翘的异花授粉结果率高于自花授粉,以异交为主,其繁育系统属兼性异交.研究结果认为,连翘雌雄异位和雌雄异熟是其自然结果率低下的主要原因,为进一步探讨连翘在木犀科中的系统进化提供了生殖生态学的依据.