Nonrandom, Size- and Timing-Biased Breeding in a Hatchery Population of Steelhead Trout

Abstract:  Hatcheries have been built and operated to buffer salmon and trout populations from overfishing and to compensate for habitat lost or degraded by human activities. These facilities are now so prevalent that in some cases hatchery-produced salmon outnumber salmon produced in the wild. By default, this makes them an important component in the current ecology and evolution of salmonids. Hatcheries differ from natural environments in many ways, and among the most fundamental is the necessity that humans select fish for breeding instead of allowing natural processes of mate choice and competition. We examined the mating system for steelhead trout ( Oncorhynchus mykiss ) at Forks Creek Hatchery in southwest Washington and investigated factors affecting selection of individual steelhead for spawning by the hatchery staff. Despite efforts by the staff to not spawn selectively, data on steelhead spawned over 7 years revealed selection for large adult body size and early reproductive timing and a tendency for size-assortative mating (i.e., large with large). Selection on size was related to selection on reproductive timing because early returning fish tended to be larger than those returning later. To improve the fitness of both hatchery fish destined to spawn in the wild and hatchery fish designated to be spawned in the hatchery, a better understanding of factors associated with the range of reproductive success and mate-choice mechanisms in the wild is vital. This knowledge may then be applied to artificial propagation programs designed for conservation or enhancement.     

城市污水处理厂好氧颗粒污泥的特性

对城市污水处理厂曝气池中筛选出的好氧颗粒污泥进行了分析.结果表明,这些颗粒污泥的直径主要在0.2～0.8 mm范围;平均圆度为1.29;沉淀速率约在10～42 m h-1之间;比耗氧速率(SOUR)为14.2～18.9 mg g-1h-1,小于活性污泥;挥发性物质占总固体的量与活性污泥基本相似.这些颗粒污泥占污泥总量的0.1%～0.5%.颗粒污泥的激光共聚焦扫描显微镜(CLSM)图像显示:颗粒污泥内部几乎都由胞外聚合物(EPS)组成;细菌主要分布在颗粒污泥表面至100μm厚度区域,少部分分布在100～400μm厚度区域.     

Modeling the Effects of Anthropogenic Habitat Change on Savanna Snake Invasions into African Rainforest

Abstract:  We used a species-distribution modeling approach, ground-based climate data sets, and newly available remote-sensing data on vegetation from the MODIS and Quick Scatterometer sensors to investigate the combined effects of human-caused habitat alterations and climate on potential invasions of rainforest by 3 savanna snake species in Cameroon, Central Africa: the night adder (Causus maculatus) , olympic lined snake (Dromophis lineatus) , and African house snake (Lamprophis fuliginosus) . Models with contemporary climate variables and localities from native savanna habitats showed that the current climate in undisturbed rainforest was unsuitable for any of the snake species due to high precipitation. Limited availability of thermally suitable nest sites and mismatches between important life-history events and prey availability are a likely explanation for the predicted exclusion from undisturbed rainforest. Models with only MODIS-derived vegetation variables and savanna localities predicted invasion in disturbed areas within the rainforest zone, which suggests that human removal of forest cover creates suitable microhabitats that facilitate invasions into rainforest. Models with a combination of contemporary climate, MODIS- and Quick Scatterometer-derived vegetation variables, and forest and savanna localities predicted extensive invasion into rainforest caused by rainforest loss. In contrast, a projection of the present-day species-climate envelope on future climate suggested a reduction in invasion potential within the rainforest zone as a consequence of predicted increases in precipitation. These results emphasize that the combined responses of deforestation and climate change will likely be complex in tropical rainforest systems.     

Interacting Effects of Phenotypic Plasticity and Evolution on Population Persistence in a Changing Climate

Abstract: Climate change affects individual organisms by altering development, physiology, behavior, and fitness, and populations by altering genetic and phenotypic composition, vital rates, and dynamics. We sought to clarify how selection, phenotypic plasticity, and demography are linked in the context of climate change. On the basis of theory and results of recent empirical studies of plants and animals, we believe the ecological and evolutionary issues relevant to population persistence as climate changes are the rate, type, magnitude, and spatial pattern of climate‐induced abiotic and biotic change; generation time and life history of the organism; extent and type of phenotypic plasticity; amount and distribution of adaptive genetic variation across space and time; dispersal potential; and size and connectivity of subpopulations. An understanding of limits to plasticity and evolutionary potential across traits, populations, and species and feedbacks between adaptive and demographic responses is lacking. Integrated knowledge of coupled ecological and evolutionary mechanisms will increase understanding of the resilience and probabilities of persistence of populations and species.     

Avoiding Pitfalls of Using Species Distribution Models in Conservation Planning

Abstract:   Museum records have great potential to provide valuable insights into the vulnerability, historic distribution, and conservation of species, especially when coupled with species-distribution models used to predict species' ranges. Yet, the increasing dependence on species-distribution models in identifying conservation priorities calls for a more critical evaluation of model robustness. We used 11 bird species of conservation concern in Brazil's highly fragmented Atlantic Forest and data on environmental conditions in the region to predict species distributions. These predictions were repeated for five different model types for each of the 11 bird species. We then combined these species distributions for each model separately and applied a reserve-selection algorithm to identify priority sites. We compared the potential outcomes from the reserve selection among the models. Although similarity in identification of conservation reserve networks occurred among models, models differed markedly in geographic scope and flexibility of reserve networks. It is essential for planners to evaluate the conservation implications of false-positive and false-negative errors for their specific management scenario before beginning the modeling process. Reserve networks selected by models that minimized false-positive errors provided a better match with priority areas identified by specialists. Thus, we urge caution in the use of models that overestimate species' occurrences because they may misdirect conservation action. Our approach further demonstrates the great potential value of museum records to biodiversity studies and the utility of species-distribution models to conservation decision-making. Our results also demonstrate, however, that these models must be applied critically and cautiously.     

Paying the Extinction Debt in Southern Wisconsin Forest Understories

Abstract: The lack of long‐term baseline data restricts the ability to measure changes in biological diversity directly and to determine its cause. This hampers conservation efforts and limits testing of basic tenets of ecology and conservation biology. We used a historical baseline survey to track shifts in the abundance and distribution of 296 native understory species across 82 sites over 55 years in the fragmented forests of southern Wisconsin. We resurveyed stands first surveyed in the early 1950s to evaluate the influence of patch size and surrounding land cover on shifts in native plant richness and heterogeneity and to evaluate changes in the relative importance of local site conditions versus the surrounding landscape context as drivers of community composition and structure. Larger forests and those with more surrounding forest cover lost fewer species, were more likely to recruit new species, and had lower rates of homogenization than smaller forests in more fragmented landscapes. Nearby urbanization further reduced both alpha and beta understory diversity. Similarly, understory composition depended strongly on local site conditions in the original survey but only weakly reflected the surrounding landscape composition. By 2005, however, the relative importance of these factors had reversed such that the surrounding landscape structure is now a much better predictor of understory composition than are local site conditions. Collectively, these results strongly support the idea that larger intact habitat patches and landscapes better sustain native species diversity and demonstrate that humans play an increasingly important role in driving patterns of native species diversity and community composition.