Seed Quantity or Quality?—Reproductive Responses of Females of Two Dioecious Woody Species to Long-Term Fertilisation

Although seed quality and quantity, as well as reproductive performance are important life history stages of plants, little is known about the reproductive responses of trees to environmental changes such as increased anthropogenic deposition of nitrogen (N) and phosphorus (P). Dioecious plants are good models with which to test the environmental impact on female or male reproductive responses individually. We analysed effects of different long-term nutritional availability on the reproductive performance of two dioecious species (Taxus baccata L. and Juniperus communis L.) characterised by different life histories. By using pot experiments with vegetatively propagated plants grown in different fertilisation conditions, we observed an increase in plant growth and strobili production but a decrease in seed efficiency. Seeds produced by fertilised plants had greater seed mass. Fertiliser addition did not change C or N content nor the C/N ratio of T. baccata seeds, but increased N content and the N/P ratio; however, it did lower the C/N ratio in J. communis. Fertilisation did not change the metabolite profile in T. baccata but 18 metabolites were changed in J. communis. The study revealed new links between species life history, environmental changes, and reproduction. The findings imply that future environmental conditions may alter both seed productivity, and quality, as well as plant reproductive behaviour

Preference and Performance of the Pine-Tree Lappet Dendrolimus pini on Various Pine Species

Global commercial and recreational transport may lead to the unintentional invasion of insect species, which in turn may pose a threat to native organisms. In this study, we aimed to assess whether the economically important pest of Pinus sylvestris L., moth Dendrolimus pini L. (DP), is able to feed on nine other pine species, and how this will affect its survival, performance, growth, and development. We carried out food choice tests and a no-choice laboratory feeding experiment. We found that this insect mostly preferred its prime host, but also Pinus cembra L., Pinus contorta Douglas ex Loudon, Pinus nigra J.F.Arnold, and Pinus ponderosa Douglas ex C.Lawson. The performance test revealed a host-specific response of DP to the host plant. This response was manifested in a large variation in body mass as well as in a decrease or increase in life-history traits, such as fecundity, and wing morphology parameters. However, the larvae’s choice of particular hosts corresponded to the results of the performance test. Larvae more willingly selected food allowing better results in their performance. Larvae achieved better values of growth and development when fed on European and North American pine species or on species with two- and three-needle fascicles. In addition, attractants and repellents in needles of different pine species were chemically analyzed. Variations in the secondary metabolite composition as well as the specific leaf area of different pine species effectively explained the results found in the insects, but the content of sugars and nitrogen remains to be elucidated. We speculate that DP poses a serious threat to large areas of pine forests, if transferred, as it can survive and develop on many economically important tree species in North America and Europe

Decomposition of Herbivore-Damaged Leaves of Understory Species Growing in Oak and Pine Stands

Leaves are the largest component of forest litter. Their decomposition rate depends mainly on plant species, leaf chemical composition, microorganism biodiversity, and habitat conditions. It is known that herbivory by insects can modify the chemical composition of leaves, such as through induction. The aim of this study was to determine whether the rate of leaf decomposition is related to the susceptibility of the plant species to insect feeding and how leaf damage affects this rate. For our research, we chose six species differing in leaf resistance to insect damage: Cornus sanguinea, Frangula alnus, and Sambucus nigra (herbivore resistant), and Corylus avellana, P. padus, and Prunus serotina (herbivore susceptible). The decomposition of these plant leaves was examined in two monoculture forest stands, deciduous (Quercus robur) and coniferous (Pinus sylvestris). Litter decay rate k and change of litter mass, content of defensive metabolites (total phenols (TPh) and condensed tannins), and substances beneficial for organisms decomposing litter (nitrogen (N) and nonstructural carbohydrates (TNC)) were determined. Contrary to our expectations, leaf litter of herbivore-resistant species decomposed faster than that of herbivore-susceptible species, and damaged leaves decayed faster than undamaged leaves. We found that faster decaying leaf litter had a lower content of defensive compounds and a higher content of TNC and N, regardless of the plant species or leaf damage. Leaf litter decomposition caused a large and rapid decrease in the content of defensive compounds and TNC, and an increase in N. In all species, the tannin content was lower in damaged than in undamaged leaves. This pattern was also observed for TPh, except in S. nigra. We interpret this as the main reason for faster decay of damaged leaves. Moreover, the loss of leaf mass was greater under oak than pine stands, indicating that the microorganisms in deciduous stands are more effective at decomposing litter, regardless of leaf damage

Sex ratio of current-year (A) and 1-year-old (B) <i>Altica brevicollis coryletorum</i> beetles on shrubs growing in full light and shaded conditions over time. Numbers 1–7 (for current-year) and 1–10 (for 1-year-old) indicate successive dates of insect collection (see Materials and Methods).

<p>One-way ANOVA was used to determine the effect of term (length of the sampling period) on current-year beetles (full light, <i>R</i>² = 0.2106, <i>P</i> = 0.4918; shade, <i>R</i>² = 0.0754, <i>P</i> = 0.9374) and 1-year-old beetles (full light, <i>R</i>² = 0.5475, <i>P</i> = 0.0018; shade, <i>R</i>² = 0.2715, <i>P</i> = 0.3076).</p

Body mass of current-year (A) and 1-year-old (B) <i>Altica brevicollis coryletorum</i> beetles on shrubs growing in full light and shaded conditions over time. Numbers 1–7 (for current-year beetles) and 1–10 (for 1-year-old beetles) indicate successive dates of insect collection (see Materials and Methods).

<p>One-way ANOVA was used to determine the effect of term (length of the sampling period) on current-year beetles (full light, <i>R</i>² = 0.0515, <i>P</i> < 0.0001; shade, <i>R</i>² = 0.0576, <i>P</i> = 0.0002) and on 1-year-old beetles (full light, <i>R</i>² = 0.1742, <i>P</i> < 0.0001; shade, <i>R</i>² = 0.0616, <i>P</i> < 0.0001).</p

Summary of ANOVA on the effects of time of occurrence (age: current-year vs 1-year-old), light conditions (high light vs shade), sex (female vs male), term (length of the sampling period, see Materials and Methods) and their interactions on the body mass of adult <i>Altica brevicollis coryletorum</i> beetles.

<p>The factor “term” was nested in the factor “age” (term[age]). <i>P</i> values <0.05 are in bold.</p

Correction: Sex Ratio and Body Mass of Adult Herbivorous Beetles Depend on Time of Occurrence and Light Conditions

<p>Correction: Sex Ratio and Body Mass of Adult Herbivorous Beetles Depend on Time of Occurrence and Light Conditions</p

Body mass and sex ratio of current-year (A) and 1-year-old (B) <i>Altica brevicollis coryletorum</i> beetles over time. Numbers 1–7 and 1–10 indicate successive dates of insect collection (see Materials and Methods).

<p>One-way ANOVA was used to determine the effect of term on females (current-year, <i>R</i>² = 0.0824, <i>P</i> < 0.0001; 1-year-old, <i>R</i>² = 0.2530, <i>P</i> < 0.0001), males (current-year, <i>R</i>² = 0.0726, <i>P</i> < 0.0001; 1-year-old, <i>R</i>² = 0.1393, <i>P</i> < 0.0001), and the sex ratio (current-year, <i>R</i>² = 0.1028, <i>P</i> = 0.4779; 1-year-old, <i>R</i>² = 0.1545, <i>P</i> = 0.1955).</p

Body mass and sex ratio of current-year (A) and 1-year-old (B) <i>Gonioctena quinquepunctata</i> beetles over time. Numbers 1–6 and 1–8 indicate successive dates of insect collection (see Materials and Methods).

<p>One-way ANOVA was used to determine the effect of term (length of the sampling period) on the body mass of females (current-year, <i>R</i>² = 0.1177, <i>P</i> < 0.0001; 1-year-old, <i>R</i>² = 0.0895, <i>P</i> < 0.0001), males (current-year, <i>R</i>² = 0.2902, <i>P</i> < 0.0001; 1-year-old, <i>R</i>² = 0.1882, P < 0.0001), and the sex ratio (current-year, <i>R</i>² = 0.1284, <i>P</i> = 0.0986; 1-year-old, <i>R</i>² = 0.7117, <i>P</i> < 0.0001).</p

Summary of ANOVA on the effects of time of occurrence (age: current-year vs 1-year-old), cherry species (<i>Prunus padus vs P</i>. <i>serotina</i>), light conditions (high light vs shade), term (length of the sampling period, see Materials and Methods) and their interactions on the F/M sex ratio of adult <i>Gonioctena quinquepunctata</i> beetles.

<p>The factor “term” was nested in the factor “age” (term[age]). <i>P</i> values <0.05 are in bold.</p