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1. Insect oral secretions are important for the induction of a number of plant responses, but the relative role of mechanical damage in the induction of these responses is often not well understood. Damage from the frugivore Heliothis subflexa, a specialist on Physalis species, causes herbivore-induced fruit abscission. In this field study, we examined the separate and combined effects of mechanical damage and H. subflexa oral secretions on Physalis fruit abscission. 2. To determine the relative role of mechanical and chemical factors, the following treatments were administered to fruit: (1) three levels of mechanical damage, (2) natural herbivore damage by control larvae and by larvae surgically treated to inhibit saliva secretion, and (3) injection of H.subflexa oral secretions and a water control. Abscission of mechanically damaged fruit with and without the addition of oral secretions was also compared. 3. Mechanical damage was sufficient to cause fruit abscission, and the addition of oral secretions to mechanically damaged fruit did not cause an increase in fruit abscission. Normal caterpillars and those treated to inhibit saliva secretion caused similar abscission rates. 4. Though most studies examining the effects of insect oral secretions on induced plant responses find these chemical stimuli to be important or essential, the results of the present study showed that oral secretions are not necessary for fruit abscission. Future work is needed to determine the relative importance of mechanical damage in herbivore-induced plant responses in other systems.

Misidentification of animals is potentially important when naturally existing features (natural tags) are used to identify individual animals in a capture-recapture study. Photographic identification (photoID) typically uses photographic images of animals' naturally existing features as tags (photographic tags) and is subject to two main causes of identification errors: those related to quality of photographs (non-evolving natural tags) and those related to changes in natural marks (evolving natural tags). The conventional methods for analysis of capture-recapture data do not account for identification errors, and to do so requires a detailed understanding of the misidentification mechanism. Focusing on the situation where errors are due to evolving natural tags, we propose a misidentification mechanism and outline a framework for modeling the effect of misidentification in closed population studies. We introduce methods for estimating population size based on this model. Using a simulation study, we show that conventional estimators can seriously overestimate population size when errors due to misidentification are ignored, and that, in comparison, our new estimators have better properties except in cases with low capture probabilities (

Fruit abscission as a response to herbivory is well-documented in many plant species, but its effect on further damage by mobile herbivores that survive fruit abscission is relatively unstudied. Physalis plants (Solanaceae) abscise fruit containing feeding larvae of their main frugivore, Heliothis subflexa Guenee (Lepidoptera: Noctuidae), a specialist moth. We tested the ability of H. subflexa larvae placed under the plant canopy to find and climb onto two architecturally different Physalis species. Physalis pubescens L., a low, shrub-like, spreading plant, abscises its fruit at a higher rate than Physalis angulata L., a tall arborescent plant. As a result, small larvae are more often dropped from P. pubescens . Third and fifth instars located P. pubescens faster and with a higher probability than P. angulata . Although fifth instars outperformed third-instar caterpillars at finding P. angulata , P. pubescens was located equally fast by the two instars. Heliothis subflexa located Physalis plants more successfully and more quickly than a close relative, the generalist Heliothis virescens Fabricius. The higher fruit abscission rates in P. pubescens may be an evolved response to its greater susceptibility to searching caterpillars.

Plant growth regulators are routinely used in cotton (Gossypium hirsutum L.) production to reduce plant height and hasten maturity. The objective of this research was to determine the response of several cotton cultivars to mepiquat pentaborate (MPB) application in environments accumulating different levels of heat units. Four MPB application regimes were imposed on three cultivars in Virginia and South Carolina in 2005 and 2006. Total MPB season rates of 0.0, 54.9, 85.3, or 121.9 g ai ha -1 applied at the five-leaf stage, pin-head square, match-head square, and early bloom were used. The cultivars were: Deltapine (DP) 444 BG/RR, an "early-maturing" cultivar; Fibermax (FM) 960 BR, a "medium-maturing" cultivar; and DP 555 BG/RR, a "late-maturing" cultivar. In South Carolina in 2006, FM 960 BR July plant height was reduced by 25% with MPB application compared to only 12 and 13% for DP 444 BG/RR and DP 555 BG/RR, respectively, although actual plant height reductions were not different among cultivars. Mepiquat pentaborate applications decreased plant height at harvest by 8 to 34%, height-to-node ratio by 10 to 32%, enhanced maturity as measured by nodes above white flower for all cultivars, and decreased lint yield by 3.7 to 8.5% compared to untreated cotton. Higher seasonal totals and earlier initiation of MPB application resulted in the greatest decrease in lint yield.

Oleate content is important for the nutritional value and oxidative stability of soybean [Glycine max (L.) Merr.] seed oil. Response to selection for higher oleate content depends on its heritability in breeding populations, and correlated responses of other fatty acid and agronomic traits to selection for oleate content depend on their genetic correlations with oleate. The objective of this study was to estimate the heritability of oleate content and to determine the correlation of oleate with other fatty acid and agronomic traits in three soybean populations segregating for major and minor oleate genes grown in multiple environments. One of the populations consisted of 721 lines, providing excellent precision for estimation of the genetic parameters. The results of this study indicated that heritability for oleate content was suffi ciently high that early generation selection can be effective when practiced on unreplicated lines grown at a single environment. Signifi cant negative correlations were observed between oleate and linoleate, oleate and linolenate, as well as oleate and palmitate in all three populations. Signifi cant positive correlations were detected between palmitate and stearate in one population segregating for oleate genes and fap nc and fap1 alleles, which reduce palmitate content. In the same population we also observed a signifi cant negative correlation between yield and oleate content, and positive correlations between yield and linoleate, and linolenate and palmitate contents.

Current methods for estimation of age- and year-specific instantaneous mortality rates based on multiyear, multiple-age tagging studies assume that it is feasible to tag fish in a wide range of ages. For some species, however, only the youngest one or two age-classes are readily available for tagging. Given the practical advantages of tagging young fish only, an important question is whether such studies would provide the information needed for estimation of age-dependent mortality rates. We investigated three designs: tagging only the youngest available age-class, tagging the two youngest age-classes, and tagging the first five age-classes. We carried out simulation studies to assess estimator performance under these three designs, in each case assuming the same total number of tagged fish. Data were generated assuming fishing mortality rates to be age and year dependent and natural mortality rates to be constant or with limited age dependence. Estimator performance is best when fish are tagged ...

Catch-and-release fisheries have become very important in the management of overexploited recreational fish stocks. Tag return studies, where the tag is removed regardless of fish disposition, have been used to assess the effectiveness of restoration efforts for these fisheries. We extend the instantaneous rate formulation of tag return models to allow for catch and release as well as harvest. The key point of our methods is that, given an estimate of the tag reporting rate, the fishing mortality rate (F) is separated into two components: the mortality on harvested fish and the “mortality” on tags (because the tags are removed) of fish released alive. The total fishing mortality rate for untagged fish is the sum of the Fs due to harvest and hooking mortality suffered by fish released alive. Natural mortality rates can also be estimated. Both age-independent models and age-dependent models are constructed, and the age-dependent models are illustrated by application to data from a study of striped ...

Heterosis is considered to be of little importance in soybean (Glycine max L. Merr.) because the crop is produced as "pure-line" cultivars or blends of inbred lines. The F 1 generations Holladay/ Hutcheson (Cross 1) and Brim/Boggs (Cross 2) were generated by hand pollinations. Inbred generations were generated by bulk selfing. The F 1 , F 2 , F 3 , F 4 , and F 5 generations were yield-tested in replicated bordered single row plots in multiple years and locations. The average yield of Cross 1 F 1 was 16% greater than that of the highest-yielding parent and the average yield of the Cross 2 F 1 was 5% greater than the highest-yielding parent. Cross 1 showed significant inbreeding depression when regressed on percentage inbreeding which is clear evidence of dominance for yield. Possible genetic bases for heterosis in soybean include gene complementation or interaction of duplicate favorable loci in repulsion, linked dominant alleles that are inherited as a unit, a greater number of dominant alleles in the F 1 than either parent separately, multiple dosage-dependant regulatory loci, and/or overdominance. The existence of heterosis should be evidence that superior gene combinations are possible. The magnitude of yield heterosis may be a useful criterion for selection among biparental crosses.

We used a decadal data set, with weekly to biweekly sampling in April‐October and monthly sampling in November‐ March, to characterize climatic (hurricane-level storms, a sustained 3-yr drought) and anthropogenic influences on N and P concentrations and loadings to a large eutrophic, poorly flushed estuary, the Neuse Estuary of the Albemarle‐Pamlico Estuarine System. Mass volume transport data were obtained with cross-estuary transect flow measurements taken near the entrance to the estuary. Although trends were minimally influenced by hurricanes, analyses were significantly affected by the sustained drought near the end of the study. As examples, decreasing trends in total N (TN), total P (TP), and bottom-water dissolved oxygen concentrations, and in TN loadings were significant considering all data, but these trends were not significant when the sustained drought was excluded from analysis. In addition, the trend in TN loading was especially sensitive to the initial sampling period. NH concentrations dramatically increased (overall by ;500%) as a 1 4 persistent trend regardless of attempts to control for climatic events. An increasing trend in NH also was documented 1 4 in an adjacent, rapidly flushed Coastal Plain estuary, the Cape Fear. The NH data suggest a regional-scale effect of high 1 4 inputs from inadequately controlled, increasing nonpoint sources. The fragility of TN loading trends, the striking increase in NH concentrations, and the lack of management emphasis on controlling nonpoint sources such as ‘‘new’’ industri1 4 alized swine production collectively do not support recent reports of achievement of a 30% reduction in TN loading to the Neuse. Nonpoint sources remain a critical target for reduction to alleviate the negative effects of cultural eutrophication in this system, as in many estuaries throughout the world.

Deadwood is an important legacy structure in managed forests, providing continuity in shelter and resource availability for many organisms and acting as a vehicle by which nutrients can be passed from one stand to the next following a harvest. Despite existing at the interface between below- and above-ground systems, however, much remains unknown about the role woody debris plays in linking these zones. Moreover, it remains untested whether the accelerative effects of wood-feeding insects on wood decomposition influence tree growth or nutritional status in forests. In this study, we added different quantities of pine logs to the bases of saplings in two-year-old loblolly pine (Pinus taeda L.) plantations in Mississippi, USA. We included a treatment in which subterranean termites (Blattodea: Rhinotermitidae: Reticulitermes) were excluded from logs to determine how these insects affect the release of nutrients from wood and, in turn, tree growth. After 51 months of decomposition, we quantified below-ground effects by measuring microbial biomass, plant-available forms of N, and ectomycorrhizal diversity associated with fine tree roots. Meanwhile, above-ground measurements focused on the elemental concentrations in decomposing wood either protected or unprotected from termites and tree metrics related to growth and nutrient status. We found additions of wood to significantly increase nitrate and potential net nitrification relative to reference treatments but detected no significant effects on tree growth, needle nitrogen concentrations, or ectomycorrhizal diversity. Soil nitrate and potential net nitrification were higher under protected vs. unprotected logs, and plant-available forms of N were mostly more abundant short distances away from both protected and unprotected logs than directly under them. The wood of logs protected from termites had significantly lower concentrations of most elements compared to that of unprotected logs, largely due to the large amounts of soil imported into unprotected logs by termites. Termite exclusion had no measurable effect on tree growth, nutritional status, or ectomycorrhizal diversity, however. Our findings indicate that deadwood and termites both contribute to the spatial heterogeneity of soil properties but may have limited short-term local effects on tree growth. Longer-term studies and studies on less fertile sites are needed. USDA Forest Service, Southern Research Station We thank Misty Booth (Mississippi State University) for granting permission to conduct this study on the John W. Starr Memorial Forest and Craig Bell and Shawn Cooper (USDA Forest Service) for help cutting the logs used in this experiment. We also thank Yigen Chen (University of California, Davis) for helpful statistical advice and Mac Callaham and Bayan Sheko (USDA Forest Service) for early discussions about soil sampling, and an anonymous reviewer for comments that improved the manuscript. This study was funded by the USDA Forest Service, Southern Research Station.

In large yield trials, variation in soil fertility (or, more generally, yield potential) can result in substantial heterogeneity within blocks and, thus, poor precision in treatment estimates. Precision may be improved using statistical analyses in which this spatial variation is accounted for in estimation of treatment or entry means. Three such types of spatial analysis are trend analysis, the Papadakis method, and analyses based on correlated errors models (which account for spatial variation throngh correlations between yields of neighboring plots). We reviewed the theory and empirical performance of these spatial analyses and compared them with the classical analyses [...]

In the southeastern USA, harvest of pine straw sometimes involves mechanical raking of natural Pinus palustris (longleaf pine) communities. Little is known about the effects of raking nor how these effects may vary in time and space. In a two yr experiment, we examined the effects of mechanized raking on Pinus palustris dominated communities (scrub oak, dry savanna, and mesic savanna) by monitoring vegetation at seven spatial scales (0.01-100 m2). We measured floristic similarity and the proportion of species initially present that were gained (i.e. new species) or lost during four sampling periods. Relationships between spatial scale and these community attributes were analyzed using a repeated measures approach and functional response curves. Spatial scale clearly affected observed rates of species loss and floristic similarity; losses declined and floristic similarity increased as scale increased. We relate these patterns to expanding population sizes with scale and our inability to detect spe...