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91.
In recent years, altered forest conditions, climate change, and the increasing numbers of homes built in fire prone areas
has meant that wildfires are affecting more people. An important part of minimizing the potential negative impacts of wildfire
is engaging homeowners in mitigating the fire hazard on their land. It is therefore important to understand what makes homeowners
more or less willing to take action. The research presented here comes from a study that interviewed a total of 198 homeowners
in six communities in the western United States about the activities they had undertaken to mitigate their fire risk, the
factors that contributed to their decisions, and their future intentions. The current paper reports on findings from the first
half of the longitudinal study, after 3 years we will return to interview the current homeowner on the same properties to
assess maintenance actions and facilitating and limiting factors. Overall we found a body of individuals who understand the
fire risk, are taking numerous mitigation actions, and think that these actions have reduced their risk. These homeowners
typically did not expect the government to do it for them: they wanted information about what to do and, in some cases, assistance
with the work, but saw taking care of their property primarily as their responsibility. Responses also show that key information
sources and motivating factors vary by location and that it is not inherently necessary to have relationships between community
members to create defensible space. 相似文献
92.
Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama's appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument. 相似文献
93.
Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through group defenses. The decreased tendency to aggregate in the last larval instar may therefore be linked to decreasing predation risk. 相似文献
94.
Proline is a proteinogenic amino acid in which the side chain forms a ring, the pyrrolidine ring. This is a five-membered ring made up of four carbons and one nitrogen. Here, we study the evolutionary significance of this ring size. It is shown that the size of the pyrrolidine ring has the advantage of being nearly planar and strain-free, based on a general mathematical assertion saying that the angular sum of a polygon is maximum if it is planar and convex. We also provide a sketch of the proof to this assertion. The optimality of the ring size of proline can be derived from a triangle inequality for angles. Quasi-planarity is physiologically significant because it allows an easier and evolutionarily old type of fit into binding grooves of proteins with which proline-rich proteins interact. Finally, we present a comparison with other planar, nearly planar and non-planar biomolecules such as neurotransmitters, hormones and toxins, involving, for example, aromatic rings, cyclopentanone and 1,3-dioxole. 相似文献
95.
Featured Collection Introduction: Connectivity of Streams and Wetlands to Downstream Waters
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Laurie C. Alexander Ken M. Fritz Kate A. Schofield Bradley C. Autrey Julie E. DeMeester Heather E. Golden David C. Goodrich William G. Kepner Hadas R. Kiperwas Charles R. Lane Stephen D. LeDuc Scott G. Leibowitz Michael G. McManus Amina I. Pollard Caroline E. Ridley Melanie K. Vanderhoof Parker J. Wigington Jr. 《Journal of the American Water Resources Association》2018,54(2):287-297
Connectivity is a fundamental but highly dynamic property of watersheds. Variability in the types and degrees of aquatic ecosystem connectivity presents challenges for researchers and managers seeking to accurately quantify its effects on critical hydrologic, biogeochemical, and biological processes. However, protecting natural gradients of connectivity is key to protecting the range of ecosystem services that aquatic ecosystems provide. In this featured collection, we review the available evidence on connections and functions by which streams and wetlands affect the integrity of downstream waters such as large rivers, lakes, reservoirs, and estuaries. The reviews in this collection focus on the types of waters whose protections under the U.S. Clean Water Act have been called into question by U.S. Supreme Court cases. We synthesize 40+ years of research on longitudinal, lateral, and vertical fluxes of energy, material, and biota between aquatic ecosystems included within the Act's frame of reference. Many questions about the roles of streams and wetlands in sustaining downstream water integrity can be answered from currently available literature, and emerging research is rapidly closing data gaps with exciting new insights into aquatic connectivity and function at local, watershed, and regional scales. Synthesis of foundational and emerging research is needed to support science‐based efforts to provide safe, reliable sources of fresh water for present and future generations. 相似文献
96.
The organic sector is in an ongoing, but somewhat ambiguous, process of differentiation. Continuing growth has also entailed intensified competition and the emergence of conventional structures within the sector. Producers are under pressure to adapt their terms of production to these developments, bearing the risk that the original values and principles of organic farming may become irrelevant. To confront these tendencies and maintain their position on the market, organic producers and processors have launched a number of organic–fair initiatives. As some consumers attach importance to ethical aspects of consumption, these actors sense market opportunities in such quality differentiation. This article presents results of a study on current organic–fair criteria, as formulated by such initiatives. All of them define standards of distributive, procedural and informational fairness, with fair prices for producers and processors and long-term agreements being core standards. We show that distributive and procedural fairness are closely linked. Although organic–fair initiatives and their main protagonists focus on external fairness, such as fair prices for farmers, thus far internal concerns, such as minimum wages or employee involvement, are of less importance. The initiatives exemplify the differentiation of quality-oriented organic food producers in highly competitive markets. They have the potential to revitalise the original values of the sector and contribute significantly to ethical standardization therein. In order to make a substantial contribution to future development of the sector, a critical examination of aspects of internal fairness as well as the formulation of appropriate standards in this field is recommended. 相似文献
97.
Maria Byrne Natalie A. Soars Melanie A. Ho Eunice Wong David McElroy Paulina Selvakumaraswamy Symon A. Dworjanyn Andrew R. Davis 《Marine Biology》2010,157(9):2061-2069
Climate change driven ocean acidification and hypercapnia may have a negative impact on fertilization in marine organisms
because of the narcotic effect these stressors exert on sperm. In contrast, warmer, less viscous water may have a positive
influence on sperm swimming speed and so ocean warming may enhance fertilization. To address questions on future vulnerabilities
we examined the interactive effects of near-future ocean warming and ocean acidification/hypercapnia on fertilization in intertidal
and shallow subtidal echinoids (Heliocidaris erythrogramma, H. tuberculata, Tripneustes gratilla, Centrostephanus rodgersii), an asteroid (Patiriella regularis) and an abalone (Haliotis coccoradiata). Batches of eggs from multiple females were fertilized by sperm from multiple males in all combinations of three temperature
and three
\textpH/P\textCO2 {\text{pH}}/P_{{{\text{CO}}_{2} }} treatments. Experiments were placed in the setting of projected near-future conditions for southeast Australia, an ocean
change hot spot. There was no significant effect of warming and acidification on the percentage of fertilization. These results
indicate that fertilization in these species is robust to temperature and
\textpH/P\textCO2 {\text{pH}}/P_{{{\text{CO}}_{2} }} fluctuation. This may reflect adaptation to the marked fluctuation in temperature and pH that characterises their shallow
water coastal habitats. Efforts to identify potential impacts of ocean change to the life histories of coastal marine invertebrates
are best to focus on more vulnerable embryonic and larval stages because of their long time in the water column where seawater
chemistry and temperature have a major impact on development. 相似文献
98.
Petra Quillfeldt Christian C. Voigt Juan F. Masello 《Behavioral ecology and sociobiology》2010,64(7):1157-1164
Pelagic seabird populations can use several discrete wintering areas, but it is unknown if individuals use the same wintering
area year after year. This would have consequences for their population genetic structure and conservation. We here study
the faithfulness of individuals to a moulting area within and among years in a small pelagic seabird, the Thin-billed prion,
which moult their primary feathers during the early part of the non-breeding period. According to stable carbon isotope ratios
(δ13C) of these feathers, 90% of Thin-billed prions moult in Antarctic and 10% in South American waters. Repeated samples from
individuals in 2 or 3 years indicated that several birds changed between Antarctic and South American moulting areas or vice
versa. However, individuals moulting in an area in one year were more likely to do so again. Four out of five adults maintained
highly conserved δ13C over the extended moulting period. One bird, however, had systematic changes in δ13C indicating latitudinal movements between the two areas during moult. Thus, the present data show that this seabird species
has a highly flexible migratory strategy, not only at the population level, but also at the individual level, enabling these
seabirds to exploit a highly unpredictable environment. 相似文献
99.
Melanie B. Ruhiman Wade L. Nutter 《Journal of the American Water Resources Association》1999,35(2):277-290
ABSTRACT: Historic changes in stream channel morphology were investigated in the Georgia Piedmont to better understand the hydrologic processes and functioning of the region's riverine systems. USGS gaging station data and channel geomorphology data were collected from thirty study sites in the Upper Oconee River Basin for flood frequency analysis. Historic and modern (i.e., present-day) channel capacity discharge (i.e., overbank flow) was calculated using Manning's equation and historic channel cross-section records. The recurrence interval for overbank flow was estimated for each site from flood frequency data. Results indicate that channel expansion has occurred throughout the basin, especially in upper reaches. Recurrence intervals for modern overbank events were variable and generally high ranging from < 2 to > 500 years for first to third order streams. They were less variable and lower for fourth and fifth order streams, ranging from < 2 to 3 years. Potential depositional thresholds were identified that exemplify the complex response of sediment distribution patterns throughout the basin. Results indicate overbank flows occur less frequently now than they once did due to historic accelerated sedimentation and subsequent channel expansion. One application of these findings is that these basin processes are likely applicable across the region and may impact the hydrologic functioning of associated Piedmont riverine wetlands that depend on flooding regimes. 相似文献
100.