Fitness traits and underlying genetic variation related to host plant specialization in the aphid Sitobion avenae

Sitobion avenae （E） is an important cereal pest worldwide that can survive on various plants in the Poaceae, but divergent selection on different host plants shouldpromote the evolution of specialized genotypes or host races. In order to evaluate their resource use strategies, clones of S. avenae were collected from oat and barley. Host-transfer experiments for these clones were conducted in the laboratory to compare their fitness traits. Our results demonstrated that barley clones had significantly lower fecundityand tended to have longer developmental times when transferred from barley to oat. However, oat clones developed faster after they were transferred to barley. Clones fromoat and barley had diverged to a certain extent in terms of fecundity and developmental time of the nymphs. The separation of barley clones and oat clones of S. avenae was alsoevident in a principal component analysis. Barley clones tended to have higher broad-sense heritabilities for fitness traits than oat clones, indicating the genetic basis of differentiationbetween them. Barley clones showed significantly higher extent of specialization compared to oat clones from two measures of specialization （i.e., Xsp and Ysp）. Therefore, barleyclones were specialized to a certain extent, but oat clones appeared to be generalized. The fitness of S. avenae clones tended to increase with higher extent of specialization. Theevolution toward ecological specialization in S. avenae clones, as well as the underlying genetic basis, was discussed.

Evolution and future of urban ecological science:ecology in,of,and for the city

The contrast between ecology in cities and ecology of cities has emphasized the increasing scope of urban ecosystem research.Ecology in focuses on terrestrial and aquatic patches within cities,suburbs,and exurbs as analogs of non-urban habitats.Urban fabric outside analog patches is considered to be inhospi-table matrix.Ecology of the city differs from ecology in by treating entire urban mosaics as social-ecolog-ical systems.Ecology of urban ecosystems incorporates biological,social,and built components.Originally posed as a metaphor to visualize disciplinary evolution,this paper suggests that the contrast has conceptual,empirical,and methodological contents.That is,the contrast constitutes a disciplinary or“local”paradigm shift.The paradigm change between ecology in and ecology of represents increased complexity,moving from focus on biotic communities to holistic social-ecological systems.A third paradigm,ecology for the city,has emerged due to concern for urban sustainability.While ecology for includes the knowledge generated by both ecology in and ecology of,it considers researchers as a part of the system,and acknowledges that they may help envision and advance the social goals of urban sustainability.Using urban heterogeneity as a key urban feature,the three paradigms are shown to contrast in five important ways:disciplinary focus,the relevant theory of spatial heterogeneity,the technology for representing spatial structure,the resulting classification of urban mosaics,and the nature of application to sustainability.Ecology for the city encourages ecologists to engage with other specialists and urban dwellers to shape a more sustainable urban future.

The effect of host plants on genotype variability in fitness and honeydew composition of Aphis fabae

Aphid species can be polyphagous, feeding on multiple host plants across genera. As host plant species can have large variation in their phloem composition, this can affect aphid fitness and honeydew composition. Previous research showed significant intraspecific genotype variation in the composition of the honeydew carbohydrates of the black bean aphid Aphis fabae, with the ant attractant trisaccharide melezitose showing especially large variation across different genotypes. In this study, we test if variation in melezitose and carbohydrate composition of aphid honeydew could be linked to the adap- tation of specific aphid genotypes to particular host plants. To this end, 4 high and 5 low melezitose secreting genotypes of the black bean aphid Aphisfabae were reared on 4 com- mon host plants： broad bean, goosefoot, beet, and poppy. The carbohydrate composition, and in particular melezitose secretion, showed important aphid genotype and host plant in- teractions, with some genotypes being high melezitose secreting on 1 host plant but not on another. However, the interaction effects were not paralleled in the fitness measurements, even though there were significant differences in the average fitness across the different host plants. On the whole, this study demonstrates that aphid honeydew composition is influenced by complex herbivore-plant interactions. We discuss the relevance of these findings in the context of ant-aphid mutualisms and adaptive specialization in aphids.

Is intraspecific variation in diet and morphology related to environmental gradients?Exploring Liem’s paradox in a cichlid fish

Interspecific studies have demonstrated that trophic morphology and ecology are not always tightly matched:a phenomenon rarely reported at the intraspecific level.In the present study,we explored relationships among diet,morphology and the environment in a widespread cichlid fish,Astatoreochromis alluaudi(Pellegrin 1904),from 6 sites in southern Uganda to test for evidence of eco-morphological matching at the interdemic level.Previous studies of Astatoreochromis alluaudi have demonstrated developmental plasticity in trophic morphology in response to diet:a mollusk diet produces specimens with large pharyngeal jaws and muscles,whereas a soft-food diet produces smaller pharyngeal jaws and corresponding changes in musculature.Sites were chosen to maximize variability in environmental variables that might directly or indirectly affect trophic morphology.We found significant differences in pharyngeal jaw and muscle morphology among populations.Similarly,we found differences in diets among sites:mollusks were found in the stomachs of fish from only 2 populations sampled,despite the presence of mollusks in 5 of the 6 sites.Although trophic morphology did match the observed diet in 2 sites,diet did not correlate with either morphology or environmental variables across sites,nor were environmental variables correlated with morphological variation among sites.These results suggest that mismatch can occur among different populations of a single species for reasons such as seasonality in resources,developmental plasticity and/or complex indirect interactions.Intraspecific mechanisms should be further studied in order to better understand the complex relationships between morphological specialization and ecological generalization.

Linking science and decision making to promote an ecology for the city:practices and opportunities

To promote urban sustainability and resilience,there is an increasing demand for actionable science that links science and decision making based on social-ecological knowledge.Approaches,frameworks,and practices for such actionable science are needed and have only begun to emerge.We propose that approaches based on the co-design and co-production of knowledge can play an essential role to meet this demand.Although the antecedents for approaches to the co-design and co-production of knowledge are decades old,the integration of science and practice to advance urban sustainability and resilience that we present is different in several ways.These differences include the disciplines needed,diversity and number of actors involved,and the technological infrastructures that facilitate local-to global connections.In this article,we discuss how the new requirements and possibilities for co-design,co-production,and practical use of social-ecological research can be used as an ecology for the city to promote urban sustainability and resilience.While new technologies are part of the solution,traditional approaches also remain important.Using our urban experiences with long-term,place-based research from several U.S.Long-Term Ecological Research sites and U.S.Department of Agriculture,Forest Service Urban Field Stations,we describe a dynamic framework for linking research with decisions.We posit that this framework,coupled with a user-defined,theory-based approach to science,is instrumental to advance both practice and science.Ultimately,cities are ideal places for integrating basic science and decision making,facilitating flows of information through networks,and developing sustainable and resilient solutions and futures.