COMPARATIVE ANALYSIS OF GALL MORPHOLOGY IN AUSTRALIAN GALL THRIPS: THE EVOLUTION OF EXTENDED PHENOTYPES

We used a combination of morphometric, phylogenetic, and life-history information to analyze the evolution and possible adaptive significance of gall morphology in a clade of 24 species of gall-inducing thrips (Insecta: Thysanoptera) on Australian Acacia trees. Principal components analysis revealed that galls varied in morphology along two main axes, spherical versus elongate (PC1) and general size (PC2). A high degree of conservation of gall shape on an independently derived phylogeny of the insects and the presence of nine species of Acacia each bearing two or three morphologically disparate gall forms induced by different thrips species indicate that interspecific variation in gall form is determined predominantly by the insects. Character optimization of PC1 on the phylogeny of gall thrips suggested that the ancestral gall form was a simple roll or curl. The diversification of gall form involved four main processes: (1) the convergent evolution of relatively spherical galls in two clades; (2) the evolution of small elongate and hemispherical galls in one clade; (3) the evolution of a lobed interior in a species with a spherical gall and multiple within-gall generations; and (4) the evolution of intraspecific gall polymorphism in a clade of apparent sibling species. Comparative analyses indicated that gall sphericity was associated with the presence of physogastry (foundress hyperfecundity) and that small elongate and hemispherical forms may be associated with the presence of multiple generations in a gall and, perhaps, with the presence of soldier castes. The evolution of a lobed interior in one species, which greatly increases inner surface area, coincided with the evolution of multiple generations. In the clade with intraspecific gall polymorphism in some species, patterns of intraspecific variation mirror patterns of interspecific variation within the clade as a whole. This is the first study to analyze the evolution of gall size and shape in a phylogenetic context and to investigate the life-history correlates of evolutionary changes in gall form. Taken together, our findings indicate that the main selective pressures driving the evolution of gall form in Australian gall thrips on Acacia involve inner surface area to volume relationships, which change in concert with foundress fecundity and the number of within-gall generations.     

Biomarkers of animal health: integrating nutritional ecology,endocrine ecophysiology,ecoimmunology, and geospatial ecology

Diverse biomarkers including stable isotope, hormonal, and ecoimmunological assays are powerful tools to assess animal condition. However, an integrative approach is necessary to provide the context essential to understanding how biomarkers reveal animal health in varied ecological conditions. A barrier to such integration is a general lack of awareness of how shared extraction methods from across fields can provide material from the same animal tissues for diverse biomarker assays. In addition, the use of shared methods for extracting differing tissue fractions can also provide biomarkers for how animal health varies across time. Specifically, no study has explicitly illustrated the depth and breadth of spacial and temporal information that can be derived from coupled biomarker assessments on two easily collected tissues: blood and feathers or hair. This study used integrated measures of glucocorticoids, stable isotopes, and parasite loads in the feathers and blood of fall‐migrating Northern saw‐whet owls (Aegolius acadicus) to illustrate the wealth of knowledge about animal health and ecology across both time and space. In feathers, we assayed deuterium (δD) isotope and corticosterone (CORT) profiles, while in blood we measured CORT and blood parasite levels. We found that while earlier migrating owls had elevated CORT levels relative to later migrating birds, there was also a disassociation between plasma and feather CORT, and blood parasite loads. These results demonstrate how these tissues integrate time periods from weeks to seasons and reflect energetic demands during differing life stages. Taken together, these findings illustrate the potential for integrating diverse biomarkers to assess interactions between environmental factors and animal health across varied time periods without the necessity of continually recapturing and tracking individuals. Combining biomarkers from diverse research fields into an integrated framework hold great promise for advancing our understanding of environmental effects on animal health.     

Rapid and unexpected effects of piscivore introduction on trophic position and diet of perch (Perca flavescens) in lakes recovering from acidification and metal contamination

1. Yellow perch (Perca flavescens) are often the only surviving fish species in acidified lakes. We studied four lakes along a gradient of recovery from acidification and that had different food web complexities. All had abundant yellow perch, two had low piscivore abundance, one had a well‐established piscivore population and one was manipulated by introducing piscivorous smallmouth bass (Micropterus dolomieu). We hypothesised that there would be strong effects on perch abundance, behaviour and diet induced by the presence of piscivores. 2. In the manipulated lake, the bass reduced yellow perch abundance by 75% over a 2‐year period. Concomitantly, perch use of the pelagic habitat fell from 48 to 40%. 3. In contrast to findings from less disturbed systems, yellow perch in the littoral zone of the manipulated lake did not strongly shift from zooplankton to benthic food sources after the arrival of piscivores. Diet analysis using stable carbon isotopes revealed a strong continued reliance on zooplankton in all lakes, independent of the degree of piscivory. The failure to switch to benthos in the refuge area of the littoral zone is most likely related to the depauperate benthos communities in these formerly acidified lakes. 4. Yellow perch in lakes recovering from acidification face a considerable ecological challenge as the necessary switch to benthic diet is hindered by a low abundance of benthos. The arrival of piscivores in these recovering lakes imposes further restrictions on perch access to food items. We infer that future recovery of perch populations (and higher trophic levels) will have to be preceded by the re‐establishment of diverse benthic macroinvertebrate communities in these lakes.     

Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.