Effects of experimental warming on survival,phenology, and morphology of an aquatic insect (Odonata)

1. Organisms can respond to changing climatic conditions in multiple ways including changes in phenology, body size or morphology, and range shifts. Understanding how developmental temperatures affect insect life‐history timing and morphology is crucial because body size and morphology affect multiple aspects of life history, including dispersal ability, whereas phenology can shape population performance and community interactions. 2. It was experimentally assessed how developmental temperatures experienced by aquatic larvae affected survival, phenology, and adult morphology of dragonflies [Pachydiplax longipennis (Burmeister)]. Larvae were reared under three environmental temperatures: ambient, +2.5, and +5 °C, corresponding to temperature projections for our study area 50 and 100 years in the future, respectively. Experimental temperature treatments tracked naturally‐occurring variation. 3. Clear effects of temperature were found in the rearing environment on survival and phenology: dragonflies reared at the highest temperatures had the lowest survival rates and emerged from the larval stage approximately 3 weeks earlier than animals reared at ambient temperatures. There was no effect of rearing temperature on overall body size. Although neither the relative wing nor thorax size was affected by warming, a non‐significant trend towards an interaction between sex and warming in relative thorax size suggests that males may be more sensitive to warming than females, a pattern that should be investigated further. 4. Warming strongly affected survival in the larval stage and the phenology of adult emergence. Understanding how warming in the developmental environment affects later life‐history stages is critical to interpreting the consequences of warming for organismal performance.     

Infiltration of a facultative ant–plant mutualism by the introduced Argentine ant: effects on mutualist diversity and mutualism benefits

1. Ant–plant mutualisms have been the focus of considerable empirical research, but few studies have investigated how introduced ants affect these interactions. Using 2 years of survey data, this study examines how the introduced Argentine ant [Linepithema humile (Mayr)] differs from native ants with respect to its ability to protect the extrafloral nectary‐bearing coast barrel cactus (Ferocactus viridescens) in Southern California. 2. Eighteen native ant species visited cacti in uninvaded areas, but cacti in invaded areas were primarily visited by the Argentine ant. The main herbivore of the coast barrel cactus present at the study sites is a leaf‐footed bug (Narnia wilsoni). 3. Herbivore presence (the fraction of surveys in which leaf‐footed bugs were present on individual cacti) was negatively related to ant presence (the fraction of surveys in which ants were present on individual cacti). Compared with cacti in uninvaded areas, those in invaded areas were less likely to have herbivores and when they did had them less often. 4. Seed mass was negatively related to herbivore presence, and this relationship did not differ for cacti in invaded areas versus those in uninvaded areas. 5. Although the Argentine ant might provide superior protection from herbivores, invasion‐induced reductions in ant mutualist diversity could potentially compromise plant reproduction. The cumulative number of ant species on individual cacti over time was lower in invaded areas and was associated with a shortened seasonal duration of ant protection and reduced seed mass. These results support the hypothesis that multiple partners may enhance mutualism benefits.     

A Comparison of the Accuracy, Variability and Speed of Five Different Methods for Estimating Leaf Area

Three analogue- and two microprocessor-based methods for estimatingleaf area were compared for accuracy, variability and speed,on 200 leaf templates of known area and contrasting shape (bipinnatifid,ensiform, elliptic and triangular). The data were analyzed intwo blocks for each shape;     

The feeding behaviour, activity and trappability of wild female Glossina pallidipe in relation to their pregnancy cycle

Female Glossina pallidipes Austen trapped with baited NG2B traps were subjected both to detailed ovarian dissection and to nutritional analysis. Using a calibration curve derived from dissected wild-caught, laboratory-held flies, the field females were assigned by discriminant analysis to each day of the pregnancy cycle. Field females were most available to NG2B traps while carrying the first instar larva. The nutritional characteristics of trapped field females over the pregnancy cycle lead to the following main conclusions. (i) Fat levels increase most rapidly during the egg in utero stage, while CRDW increases significantly only during the larval stages, culminating in a 4 mg increase during the last day of the third larval instar. (ii) The haematin content of the flies indicates that females feed at approximately 3-day intervals and may feed on any day of the pregnancy cycle. (iii) The estimated time of feeding during the day corresponds with the observed time of peak activity, both of which are earlier in the day later in the pregnancy cycle. (iv) The rate of fat usage reveals significantly greater flight activity on day 5 of the cycle than on other days, agreeing with the high trappability on this day, and overall females appear to use fat at twice the rate of males. Reproductive data provide a much more accurate picture of the relative sampling efficiency than do nutritional data, although the latter reveal the general trends correctly.     

Habitat fragmentation: island v landscape perspectives on bird conservation

Fragments of habitat are often viewed as islands and are managed as such; however, habitat fragmentation includes a wide range of spatial patterns of environments that may occur on many spatial scales. Fragments exist in a complex landscape mosaic, and dynamics within a fragment are affected by external factors that vary as the mosaic structure changes. The simple analogy of fragments to islands, therefore, is unsatisfactory. Understanding how birds respond to these complexities of fragmentation requires mechanistic studies focused on habitat selection and movement behaviour. Conservation efforts must be based on viewing fragmentation as a range of conditions that occurs in a landscape mosaic, and management should be directed toward the mosaics rather than focusing solely on reserves.     

Use of Lethal Control to Reduce Habituation to Blank Rounds by Scavenging Birds

Abstract Scavenging bird deterrence frequently fails due to habituation. We demonstrated such habituation by gulls and corvids to blank rounds used in a dawn-to-dusk regime at a landfill site in southern England. We then combined blank rounds with live rounds and shot birds whenever they attempted to land. Gull numbers declined significantly despite only 1.9% of the population being shot. Corvid numbers returned to precontrol levels despite 52.7% of the population being shot. We suggest that shooting reduces gull habituation to blank rounds but is ineffective at reducing habituation by corvids.     

Decoupled evolution of display morphology and display behaviour in phrynosomatid lizards

A widespread trend in animals is the evolution of morphological ornaments and behaviours that are involved in aggressive and courtship displays. These display traits are important from the standpoint of communication, sexual selection, and speciation. Previous authors have suggested that the evolution of display morphology and display behaviour should be closely linked. In this study, I tested for this association with behavioural and morphological data for 59 taxa of phrynosomatid lizards using phylogenetic comparative methods (Mad-dison's concentrated changes test and Felsenstein's independent contrasts). The results showed little significant association between features of display morphology and behaviour, suggesting that the evolution of these traits is not tightly coupled. This decoupling is particularly evident in the genus Sceloporus , in which several species have lost the display coloration but retain unmodified display behaviour. The results also suggest that display morphology is more evolutionarily labile than display behaviour in this group.     

Modelling Stem Height and Diameter Growth in Plants

A model of stem height and diameter growth in plants is developed.This is formulated and implemented within the framework of anexisting tree plantation growth model: the ITE Edinburgh ForestModel. It is proposed that the height:diameter growth rate ratiois a function of a within-plant allocation ratio determinedby the transport-resistance model of partitioning, multipliedby a foliage turgor pressure modifier. First it is demonstratedthat the method leads to a stable long-term growth trajectory.Diurnal and seasonal dynamics are also examined. Predicted timecourses over 20 years of stem mass, stem height, height:diameterratio, and height:diameter growth rate ratio are presented forsix treatments: control, high nitrogen, increased atmosphericcarbon dioxide concentration, increased planting density, increasedtemperature and decreased rainfall. High nitrogen and increasedtemperature give initially higher stem height:diameter ratios,whereas high CO₂gives an initially lower stem height:diameterratio. However, the responses are complex, reflecting interactionsbetween factors which often have opposing influences on height:diameterratios, for example: stem density, competition for light andfor nitrogen; carbon dioxide and decreased water stress; rainfall,leaching and nitrogen nutrition. The approach relates stem heightand diameter growth variables via internal plant variables toenvironmental and management variables. Potentially, a coherentview of many observations which are sometimes in apparent conflictis provided. These aspects of plant growth can be consideredmore mechanistically than has hitherto been the case, providingan alternative to the empirical or teleonomic methods whichhave usually been employed.Copyright 1999 Annals of Botany Company Plant, stem, height, diameter, growth, model, forest, plantation, trees.