The interactive effects of elevated CO<Subscript>2</Subscript>, temperature and initial size on growth and competition between a native C<Subscript>3</Subscript> and an invasive C<Subscript>3</Subscript> grass

A controlled environment experiment was conducted to determine the impact of enhanced carbon dioxide and temperature on competition between the C₃ grasses Austrodanthonia eriantha and Vulpia myuros. Plants were grown in mixtures and monocultures to compare the responses both with and without an interspecific competitor. Temperature and CO₂ were set at current levels (350 ppm CO₂; 20 °C day and 10 °C night temperature), in factorial combination with enhanced levels (700 ppm CO₂; 23 °C day and 13 °C night temperature). To examine the potential impact of initial seedling size on competition under elevated CO₂ and temperature, the two species were combined in mixtures of differing initial sizes. Above-ground growth of all plants was enhanced by increased CO₂ and temperature alone, however the combined temperature and CO₂ treatment showed a sub-additive effect, where growth was less than expected based on the responses to each factor independently. Austrodanthonia in mixture with Vulpia plants of the same initial size experienced a 27 reduction in growth. Austrodanthonia grown in the presence of an initially larger Vulpia plant experienced a 58 reduction in growth. When the Vulpia plant was initially smaller than Austrodanthonia, growth of the Austrodanthonia was reduced by 16%. The growth of Vulpia appeared to be largely unaffected by the presence of Austrodanthonia. Variation in the CO₂ and temperature environment did not affect the pattern of these interspecific interactions, although there was some evidence to suggest that the degree of suppression of Austrodanthonia by Vulpia was less under elevated CO₂. These results do not support the initial advantage hypothesis, as Vulpia was always able to suppress Austrodanthonia, regardless of the initial relative sizes of the competitors. Furthermore, the lack of an effect of changing the CO₂ or temperature environment on the direction of interspecific competition suggests that the competitiveness of the invasive Vulpia will be minimally affected by changes in atmospheric CO₂ concentration or temperature.     

Rapid genetic identification of local provenance seed collection zones for ecological restoration and biodiversity conservation

The ecological restoration of native plant communities requires the collection of large amounts of seed. Use of non-local provenance seed can have detrimental consequences for the success of restoration if there is a home-site advantage, and for nature conservation through the erosion of natural patterns of population genetic structuring and/or genetic swamping (and extirpation) of locally significant genotypes. As part of an ongoing project to genetically delineate local provenance seed collection zones for species within a large urban bushland remnant of high conservation value, we assessed population genetic differentiation in two widespread coastal leguminous species, Acacia rostellifera and A. cochlearis (Fabaceae), commonly used in restoration programmes in SW Australia. Using amplified fragment length polymorphism (AFLP), we found very high levels of genetic differentiation among populations, with an analysis of molecular variance (AMOVA) showing more than 50% of the total genetic variance to be partitioned among populations (Φ_ST=0.58 and 0.51 for A. rostellifera and A. cochlearis, respectively), and marked non-overlap of almost all potential seed source populations from the local population in ordinations. Our results suggest extremely restricted natural dispersal among populations, possibly due to a combination of low seed set, seed dispersal by ants, clonality, a linear distribution of naturally fragmented populations and possibly low outcrossing rates. We suggest a narrow seed collection zone should be applied to these species for the conservation of genetic diversity and natural patterns of population genetic structure, and we highlight the value and importance of provenance evaluation to ecological restoration.     

Dietary hardness, loading behavior, and the evolution of skull form in bats

The morphology and biomechanics of the vertebrate skull reflect the physical properties of diet and behaviors used in food acquisition and processing. We use phyllostomid bats, the most diverse mammalian dietary radiation, to investigate if and how changes in dietary hardness and loading behaviors during feeding shaped the evolution of skull morphology and biomechanics. When selective regimes of food hardness are modeled, we found that species consuming harder foods have evolved skull shapes that allow for more efficient bite force production. These species have shorter skulls and a greater reliance on the temporalis muscle, both of which contribute to a higher mechanical advantage at an intermediate gape angle. The evolution of cranial morphology and biomechanics also appears to be related to loading behaviors. Evolutionary changes in skull shape and the relative role of the temporalis and masseter in generating bite force are correlated with changes in the use of torsional and bending loading behaviors. Functional equivalence appears to have evolved independently among three lineages of species that feed on liquids and are not obviously morphologically similar. These trends in cranial morphology and biomechanics provide insights into behavioral and ecological factors shaping the skull of a trophically diverse clade of mammals.     

The metabolic enzyme phosphoglucose isomerase (Pgi) affects the outcome of intra‐specific competition in a polyembryonic wasp

1. Polyembryonic parasitoid wasps in the family Encyrtidae (Hymenoptera) have evolved a caste system consisting of morphologically and functionally distinct larvae called soldiers and reproductives. 2. Two selective pressures are thought to underlie the evolution of the soldier caste: defence against competitors and resolution of the sex ratio conflict. Previous studies also indicate that soldier development time strongly affects the outcome of intra‐specific competition in the polyembryonic encyrtid Copidosoma floridanum Ashmead. This study builds on prior findings by showing that alleles of the metabolic enzyme phosphoglucose isomerase (Pgi) differentially affect soldier development time and the outcome of competition. 3. Soldier larvae with the Pgi alleles 100 or 120 emerged on average 65 h post‐parasitism, whereas soldier larvae with a third allele, 54, emerged at 67 h. In turn, C. floridanum broods homozygous for the 100 and 120 alleles outcompete broods homozygous for the 54 allele. 4. Pgi allelic diversity may be maintained through a life‐history trade‐off affecting female brood sizes with homozygous broods bearing the developmentally disadvantageous 54 allele producing more adult females than broods bearing alternate common alleles.     

Telomere length reveals cumulative individual and transgenerational inbreeding effects in a passerine bird

Inbreeding results in more homozygous offspring that should suffer reduced fitness, but it can be difficult to quantify these costs for several reasons. First, inbreeding depression may vary with ecological or physiological stress and only be detectable over long time periods. Second, parental homozygosity may indirectly affect offspring fitness, thus confounding analyses that consider offspring homozygosity alone. Finally, measurement of inbreeding coefficients, survival and reproductive success may often be too crude to detect inbreeding costs in wild populations. Telomere length provides a more precise measure of somatic costs, predicts survival in many species and should reflect differences in somatic condition that result from varying ability to cope with environmental stressors. We studied relative telomere length in a wild population of Seychelles warblers (Acrocephalus sechellensis) to assess the lifelong relationship between individual homozygosity, which reflects genome‐wide inbreeding in this species, and telomere length. In juveniles, individual homozygosity was negatively associated with telomere length in poor seasons. In adults, individual homozygosity was consistently negatively related to telomere length, suggesting the accumulation of inbreeding depression during life. Maternal homozygosity also negatively predicted offspring telomere length. Our results show that somatic inbreeding costs are environmentally dependent at certain life stages but may accumulate throughout life.     

The evolution of the major histocompatibility complex in upstream versus downstream river populations of the longnose dace

Populations in upstream versus downstream river locations can be exposed to vastly different environmental and ecological conditions and can thus harbor different genetic resources due to selection and neutral processes. An interesting question is how upstream–downstream directionality in rivers affects the evolution of immune response genes. We used next‐generation amplicon sequencing to identify eight alleles of the major histocompatibility complex (MHC) class II β exon 2 in the cyprinid longnose dace (Rhinichthys cataractae) from three rivers in Alberta, upstream and downstream of municipal and agricultural areas along contaminant gradients. We used these data to test for directional and balancing selection on the MHC. We also genotyped microsatellite loci to examine neutral population processes in this system. We found evidence for balancing selection on the MHC in the form of increased nonsynonymous variation relative to neutral expectations, and selection occurred at more amino acid residues upstream than downstream in two rivers. We found this pattern despite no population structure or isolation by distance, based on microsatellite data, at these sites. Overall, our results suggest that MHC evolution is driven by upstream–downstream directionality in fish inhabiting this system.     

红眼突变灰飞虱的生物学特性和交配优势

灰飞虱Laodelphax striatellus是我国重要水稻害虫之一, 表型变异可能影响灰飞虱的配偶选择性和种群特性。本实验采用生命表构建法研究了红眼突变灰飞虱的繁殖力、 内禀增长率等种群生命参数, 然后以1红眼雌虫、 1红眼雄虫和1纯合黑眼雄虫（♀rr×♂rr♂BB）或1红眼雄虫、 1红眼雌虫和1纯合黑眼雌虫（♀rr♀BB×♂rr）配对模式以及不同比例红眼成虫群体配对模式研究红眼突变对灰飞虱交配竞争力的影响。结果表明红眼突变灰飞虱除若虫死亡率（17.1%）显著高于正常个体（10.3%） (P<0.05)外, 其他生物学指标如繁殖力、 卵孵化历期、 若虫发育历期、 成虫寿命、 内禀增长率等与正常个体无显著差异。但红眼突变对灰飞虱配偶选择性有一定的影响。♀rr×♂rr♂BB和♀rr♀BB×♂rr组合F1代红眼和黑眼分离比例卡方试验值为18.15和14.99, 大于理论值。当红眼与黑眼个体以2︰8比例配对时, 红眼灰飞虱雄虫存在交配优势, 其后代红眼个体数大于期望值。这些结果为进一步研究灰飞虱红眼突变机理和利用红眼基因标记研究灰飞虱遗传分化奠定了基础     

Cyclic temperatures influence growth efficiency and biochemical body composition of vertically migrating fish

1. Diel vertical migrations (DVM) are frequently observed in pelagic fish and zooplankton populations. In addition to predator avoidance and foraging opportunity, bioenergetics optimisation has been hypothesised to cause the selective advantage of migrating fish. However, experimental confirmation of growth advantages of fish held at naturally observed cyclic temperatures, and food densities are surprisingly rare. 2. We compared growth rates, growth efficiencies and energy budgets of vendace (Coregonus albula, Salmoniformes) fed daily rations of 10% body mass and held at low (4.5 °C), high (8 °C) and cyclic (switch between 4.5 and 8 °C) temperatures over a period of 6 weeks. Biochemical body composition was evaluated by bioimpedance analyses and direct determination of water, lipid and protein content in a subset of fish. 3. Growth rate and food conversion efficiency were similar in fish held at high and cyclic temperatures, but higher than those found at low temperatures. Body condition of fish at cyclic temperatures was maximised, but these fish also had the highest water content. The proportion of lipids and proteins was slightly depleted in fish held at cyclic and low temperatures relative to the high temperature treatment. Accordingly, growth and biochemical composition of fish responded specifically to cyclic temperatures and were not simply intermediate between those found at low and high temperatures. 4. We could not confirm a bioenergetics advantage of fish switching between high and low temperatures. However, there were no substantial extra metabolic costs through exposure to cyclic temperatures, and hence, fish performing DVM may benefit from predation avoidance without compromising their metabolic balance and hence growth rates. These results suggest that the evolution of DVM is a multi‐faceted process with no single ultimate explanation.