Latitudinal variation and coevolutionary diversification of sexually dimorphic traits in the false blister beetle Oedemera sexualis

Sexual traits are subject to evolutionary forces that maximize reproductive benefits and minimize survival costs, both of which can depend on environmental conditions. Latitude explains substantial variation in environmental conditions. However, little is known about the relationship between sexual trait variation and latitude, although body size often correlates with latitude. We examined latitudinal variation in male and female sexual traits in 22 populations of the false blister beetle Oedemera sexualis in the Japanese Archipelago. Males possess massive hind legs that function as a female‐grasping apparatus, while females possess slender hind legs that are used to dislodge mounting males. Morphometric analyses revealed that male and female body size (elytron length), length and width of the hind femur and tibia, and allometric slopes of these four hind leg dimensions differed significantly among populations. Of these, three traits showed latitudinal variation, namely, male hind femur was stouter; female hind tibia was slenderer, and female body was smaller at lower latitudes than at higher latitudes. Hind leg sizes and shapes, as measured by principal component analysis of these four hind leg dimensions in each sex, covaried significantly between sexes, suggesting coevolutionary diversification in sexual traits. Covariation between sexes was weaker when variation in these traits with latitude was removed. These results suggest that coevolutionary diversification between male and female sexual traits is mediated by environmental conditions that vary with latitude.     

Disruptive natural selection predicts divergence between the sexes during adaptive radiation

Evolution of sexual dimorphism in ecologically relevant traits, for example, via resource competition between the sexes, is traditionally envisioned to stall the progress of adaptive radiation. An alternative view is that evolution of ecological sexual dimorphism could in fact play an important positive role by facilitating sex‐specific adaptation. How competition‐driven disruptive selection, ecological sexual dimorphism, and speciation interact during real adaptive radiations is thus a critical and open empirical question. Here, we examine the relationships between these three processes in a clade of salamanders that has recently radiated into divergent niches associated with an aquatic life cycle. We find that morphological divergence between the sexes has occurred in a combination of head shape traits that are under disruptive natural selection within breeding ponds, while divergence among species means has occurred independently of this disruptive selection. Further, we find that adaptation to aquatic life is associated with increased sexual dimorphism across taxa, consistent with the hypothesis of clade‐wide character displacement between the sexes. Our results suggest the evolution of ecological sexual dimorphism may play a key role in niche divergence among nascent species and demonstrate that ecological sexual dimorphism and ecological speciation can and do evolve concurrently in the early stages of adaptive radiation.     

The evolution of growth-forms in the Macaronesian genus Aeonium (Crassulaceae) inferred from chloroplast DNA RFLPs and morphology

Phylogenetic relationships among species of Aeonium were studied using morphological characters and chloroplast DNA RFLPs. Cladistic analysis of weighted morphological data indicates that the small, herbaceous and least woody species are basal in the genus. Chloroplast DNA data gave similar results, supporting the separation of the herbaceous or small, woody species from the large, hapaxanth rosettes, rosette trees, and branched subshrubs with yellow, white or red flowers as well as the only (herbaceous) species with axillary inflorescences. The relationships among the species descending from a polytomy that comprises all species of the genus as well as a polytomy which comprises 18 of the 26 species studied, are only very incompletely resolved, except for two monophyletic clades that contain the branched subshrubs with yellow flowers ( A . sect. Aeonium ) and the branched subshrubs and rosette trees with white or red flowers ( A . sect. Leuconium ), respectively. Cladistic analysis of the combined morphological and chloroplast DNA data improved resolution considerably. Four monophyletic clades are distinguished, each of which, except for three species, comprises only one of the five main growth-form types. Although Aeonium is generally regarded as an outstanding example of adaptive radiation, this mode of speciation seems to have been of minor significance in the evolution of the genus, because each growth-form apparently evolved only once. Instead, island speciation in the absence of major ecological shifts, is probably more important in the evolution of the genus.     

穿透雨减少和氮添加对毛竹叶片和细根化学计量学的影响

全球气候变化导致的干旱和人类活动引起的大气氮沉降升高,将会直接影响森林生态系统的结构与功能。叶片和细根作为植物最重要的资源获取功能器官,其化学计量学特征可指示其资源利用、生存适应策略。在当前气候变化背景下,了解植物的化学计量特征和适应特征将有助于预测未来森林生态系统功能的变化。通过为期1年的双因素交互实验,探讨了穿透雨减少和氮添加影响下,我国亚热带重要森林类型毛竹林的叶片及细根碳（C）、氮（N）、磷（P）元素化学计量比的响应特征,对于认识毛竹林生态系统对全球变化的适应和养分利用策略具有重要意义。研究表明：（1）穿透雨减少处理显著降低叶片N、P含量,显著增加细根N含量,对叶片C含量和细根C、P含量无显著影响;氮添加处理显著增加土壤N含量和叶片N含量,对叶片C、P含量及细根C、N、P含量无显著影响。（2）穿透雨减少、氮添加处理及两者交互作用对土壤C：N：P均无显著影响。（3）穿透雨减少处理显著增加叶片C：N、C：P和N：P;氮添加处理显著降低叶片C：N,对叶片C：P、N：P无显著影响;穿透雨减少、氮添加交互作用显著降低叶片C：N和C：P,对叶片N：P无显著影响。（4）穿透雨减少处理显著降低细根C：N,对细根C：P及N：P无显著影响;氮添加处理及穿透雨减少、氮添加交互作用对细根C：N：P无影响。综上短期处理的研究结果,穿透雨减少处理产生的水分胁迫对毛竹产生了关键限制作用,毛竹采取了降低叶片N和P含量、增加细根N含量,提高叶片的N和P利用效率、保持细根稳定的P利用效率的策略。氮添加未能缓解穿透雨减少对毛竹产生的干旱胁迫,毛竹通过改变地上部分叶片和地下部分细根之间的N素分配格局和N、P利用效率以应对水分胁迫。氮添加处理下叶片N含量显著增加,C：N显著降低,而细根C、N、P含量及化学计量比没有显著变化。由此可知毛竹地上部分叶片和地下部分细根对穿透雨减少、氮添加及两者交互作用表现出不同的响应策略。本研究可为全球变化背景下毛竹人工林可持续经营提供理论依据。     

中国沿海地区海洋渔业产业生态系统适应性循环过程及驱动机制

以中国沿海地区海洋渔业产业生态系统为研究对象,采用适应性循环理论将中国海洋渔业产业生态系统划分三个适应性循环圈,一个贫穷陷阱及构成适应性循环圈所需的若干个适应性循环,揭示中国海洋渔业产业生态系统适应性循环问题。结果表明：（1）1949年以来中国海洋渔业产业生态系统依次经历了第一个适应性循环的前环中环阶段（1949-1965年）、贫穷陷阱（1966-1976年）、第二个完整的适应性循环（1977-1985年）以及第三个适应性循环的前环阶段（1986年至今）;（2）海洋渔业产业、海洋渔业生态环境、海洋渔业社会环境是触发整个系统由开发到保护到释放再到更新转变的关键要素;（3）市场需求、政策制度响应和资源限制分别是推动中国海洋渔业产业生态系统适应性循环的外部扰沌力和内部驱动力。     

Nucleotide diversity of 11S seed storage protein gene and its implications for ecological adaptation of Oryza nivara

The mechanism by which a new species arises and adapts to its environment is a fundamental question in evolutionary biology.Seed characteristics such as seed size and nutrient composition are important fitness-related traits and have been shown to vary greatly among populations and species.However,the significance of variation in seed traits in plant adaptation and speciation remains unclear.We carried out a population genetic study on nucleotide variation of one 11S seed storage protein gene(Pss) of Oryza rufipogon Griff,and O.nivara Sharma Shastry,two closely related wild rice species.By comparatively examining the genetic variation pattern of the regulatory and coding regions of Pss and fragments of six reference loci across different chromosomes,we found significantly lower polymorphisms at coding regions of the gene(PssI) in O.nivara relative to O.rufipogon.Neutrality tests indicated that the reduction of polymorphisms at PssI in O.nivara was caused by positive selection rather than population demography,implying a role of selection on the 11S seed protein gene.Further phylogenetic and principal component analyses also support the hypotheses that the origin of O.nivara was associated with the adaptive divergence on the coding region of Pss.It is most likely that higher reproductive effort would be favored when O.nivara arose from O.rufipogon populations and adapted to the environment change.     

Genotype‐environment interactions rule the response of a widespread butterfly to temperature variation

Understanding how organisms adapt to complex environments is a central goal of evolutionary biology and ecology. This issue is of special interest in the current era of rapidly changing climatic conditions. Here, we investigate clinal variation and plastic responses in life history, morphology and physiology in the butterfly Pieris napi along a pan‐European gradient by exposing butterflies raised in captivity to different temperatures. We found clinal variation in body size, growth rates and concomitant development time, wing aspect ratio, wing melanization and heat tolerance. Individuals from warmer environments were more heat‐tolerant and had less melanised wings and a shorter development, but still they were larger than individuals from cooler environments. These findings suggest selection for rapid growth in the warmth and for wing melanization in the cold, and thus fine‐tuned genetic adaptation to local climates. Irrespective of the origin of butterflies, the effects of higher developmental temperature were largely as expected, speeding up development; reducing body size, potential metabolic activity and wing melanization; while increasing heat tolerance. At least in part, these patterns likely reflect adaptive phenotypic plasticity. In summary, our study revealed pronounced plastic and genetic responses, which may indicate high adaptive capacities in our study organism. Whether this may help such species, though, to deal with current climate change needs further investigation, as clinal patterns have typically evolved over long periods.     

An adaptive independence test for microbiome community data

Advances in sequencing technologies and bioinformatics tools have vastly improved our ability to collect and analyze data from complex microbial communities. A major goal of microbiome studies is to correlate the overall microbiome composition with clinical or environmental variables. La Rosa et al. recently proposed a parametric test for comparing microbiome populations between two or more groups of subjects. However, this method is not applicable for testing the association between the community composition and a continuous variable. Although multivariate nonparametric methods based on permutations are widely used in ecology studies, they lack interpretability and can be inefficient for analyzing microbiome data. We consider the problem of testing for independence between the microbial community composition and a continuous or many-valued variable. By partitioning the range of the variable into a few slices, we formulate the problem as a problem of comparing multiple groups of microbiome samples, with each group indexed by a slice. To model multivariate and over-dispersed count data, we use the Dirichlet-multinomial distribution. We propose an adaptive likelihood-ratio test by learning a good partition or slicing scheme from the data. A dynamic programming algorithm is developed for numerical optimization. We demonstrate the superiority of the proposed test by numerically comparing it with that of La Rosa et al. and other popular approaches on the same topic including PERMANOVA, the distance covariance test, and the microbiome regression-based kernel association test. We further apply it to test the association of gut microbiome with age in three geographically distinct populations and show how the learned partition facilitates differential abundance analysis.     

Adaptation in Tunably Rugged Fitness Landscapes: The Rough Mount Fuji Model

Much of the current theory of adaptation is based on Gillespie’s mutational landscape model (MLM), which assumes that the fitness values of genotypes linked by single mutational steps are independent random variables. On the other hand, a growing body of empirical evidence shows that real fitness landscapes, while possessing a considerable amount of ruggedness, are smoother than predicted by the MLM. In the present article we propose and analyze a simple fitness landscape model with tunable ruggedness based on the rough Mount Fuji (RMF) model originally introduced by Aita et al. in the context of protein evolution. We provide a comprehensive collection of results pertaining to the topographical structure of RMF landscapes, including explicit formulas for the expected number of local fitness maxima, the location of the global peak, and the fitness correlation function. The statistics of single and multiple adaptive steps on the RMF landscape are explored mainly through simulations, and the results are compared to the known behavior in the MLM model. Finally, we show that the RMF model can explain the large number of second-step mutations observed on a highly fit first-step background in a recent evolution experiment with a microvirid bacteriophage.