Climate change and nesting behaviour in vertebrates: a review of the ecological threats and potential for adaptive responses

Nest building is a taxonomically widespread and diverse trait that allows animals to alter local environments to create optimal conditions for offspring development. However, there is growing evidence that climate change is adversely affecting nest‐building in animals directly, for example via sea‐level rises that flood nests, reduced availability of building materials, and suboptimal sex allocation in species exhibiting temperature‐dependent sex determination. Climate change is also affecting nesting species indirectly, via range shifts into suboptimal nesting areas, reduced quality of nest‐building environments, and changes in interactions with nest predators and parasites. The ability of animals to adapt to sustained and rapid environmental change is crucial for the long‐term persistence of many species. Many animals are known to be capable of adjusting nesting behaviour adaptively across environmental gradients and in line with seasonal changes, and this existing plasticity potentially facilitates adaptation to anthropogenic climate change. However, whilst alterations in nesting phenology, site selection and design may facilitate short‐term adaptations, the ability of nest‐building animals to adapt over longer timescales is likely to be influenced by the heritable basis of such behaviour. We urgently need to understand how the behaviour and ecology of nest‐building in animals is affected by climate change, and particularly how altered patterns of nesting behaviour affect individual fitness and population persistence. We begin our review by summarising how predictable variation in environmental conditions influences nest‐building animals, before highlighting the ecological threats facing nest‐building animals experiencing anthropogenic climate change and examining the potential for changes in nest location and/or design to provide adaptive short‐ and long‐term responses to changing environmental conditions. We end by identifying areas that we believe warrant the most urgent attention for further research.     

The design and function of birds' nests

All birds construct nests in which to lay eggs and/or raise offspring. Traditionally, it was thought that natural selection and the requirement to minimize the risk of predation determined the design of completed nests. However, it is becoming increasingly apparent that sexual selection also influences nest design. This is an important development as while species such as bowerbirds build structures that are extended phenotypic signals whose sole purpose is to attract a mate, nests contain eggs and/or offspring, thereby suggesting a direct trade‐off between the conflicting requirements of natural and sexual selection. Nest design also varies adaptively in order to both minimize the detrimental effects of parasites and to create a suitable microclimate for parents and developing offspring in relation to predictable variation in environmental conditions. Our understanding of the design and function of birds' nests has increased considerably in recent years, and the evidence suggests that nests have four nonmutually exclusive functions. Consequently, we conclude that the design of birds' nests is far more sophisticated than previously realized and that nests are multifunctional structures that have important fitness consequences for the builder/s.     

增强UV-B辐射对蚕豆叶片微粒体膜一些性质的影响

温室条件下,用0（Control）、8．65kJm－2d－1（TI）及11．2KJm－2d－1（t2）不同剂量的UV－B辐射处理蚕豆幼苗。Ca2 ．ATPase及Mg2 －ATPase的活性在辐射处理期间下降。在处理21d,T1和T2微粒体膜的MDA含量明显高于对照,同时IUFA急剧下降,且呈明显的剂量效应。14及21d时,膜磷脂的含量也明显下降。脂氧合酶（Lox）活性在第7及14天与对照相比都显著升高,而21d后迅速下降。结果表明,增强UV－B对微粒体膜的伤害可能是一方面导致正常酶合成与分解之间的平衡失调,另一方面导致了膜脂过氧化作用。     

The dissociation of the extracellular hemoglobin of Lumbricus terrestris at acid pH and its reassociation at neutral pH. A new model of its quaternary structure

Lumbricus terrestris HbO2 and HbCO dissociated below pH 5.0; a time-dependent alteration to the met form occurred at pH less than 5 and pH less than 4.5, respectively. The extent of dissociation was unaffected by alkaline earth cations but was decreased by an increase in ionic strength. HbO2 and HbCO exposed to pH 4.0-4.8 were centrifuged to obtain the undissociated pellet (P1) and dissociated supernatant (S1) fractions. S1 was reassociated at pH 7.0 by dialysis against various buffers and then centrifuged to obtain the reassociated pellet (P2) and unreassociated supernatant (S2) fractions. Reassociation was possible only if S1 was dialyzed against water prior to return to neutral pH; otherwise precipitation occurred starting at about pH 5.3. The extent of reassociation varied from about 40 to 80%, was usually higher for HbCO than HbO2, and was unaffected by an increase in ionic strength or by Ca(II). Gel filtration of P2 on Sephacryl S-300 at neutral pH gave one peak IaR, eluting at a slightly greater volume than the native Hb; S1 and S2 gave in addition, three peaks, Ib (200 kDa), II (65 kDa), and III (18 kDa). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that P2 was slightly deficient in subunit M relative to the Hb, that Ib was deficient in subunits D1 and D2 and that II and III consisted of subunits D1 + D2 + T and subunit M, respectively. Scanning transmission electron microscopy of P2 showed that it was smaller than the native hemoglobin: 25 nm in diameter and 16 nm in height, instead of 30 X 20 nm. Comparison of the results of the dissociations of Lumbricus Hb at alkaline pH (Kapp, O. H., Polidori, G., Mainwaring, M., Crewe, A. V., Vinogradov, S. N. (1984) J. Biol. Chem. 259, 628-639) with those obtained in this study suggested that the Hb quaternary structure was not multimeric and that an alternative model had to be considered. In the proposed model it is assumed that subunits D1 and D2 form a scaffolding or "bracelet," decorated with 12 complexes of M and T subunits.     

The use of deoxyribonucleic acid–cellulose chromatography and isoelectric focusing for the characterization and partial purification of steroid–receptor complexes

1. Two characteristic properties of the specific high-affinity steroid-binding proteins or receptors, their ability to bind to DNA-cellulose and their relatively acidic isoelectric point, have been exploited as a means of purification. These two fundamental properties distinguish the receptors from the steroid-binding proteins in serum and the non-specific low-affinity steroid-binding proteins in hormone-responsive cells. 2. A significant degree of purification of both cytoplasmic and nuclear steroid-receptor complexes can be achieved with practical facility by these procedures. The purity of the receptor complexes is sufficient to enable studies on their possible control of metabolic processes to be investigated in the future. 3. After extensive purification the physicochemical properties of the cytoplasmic androgen-receptor complex, such as sedimentation coefficient, were unchanged. Further, the purified complex fully retained at least one of its fundamental physiological properties, namely the ability to transfer 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) into chromatin in vitro. 4. The methods may also be employed for studying the changes in the structure and properties of the receptor complexes that are an essential prerequisite for the transfer of cytoplasmic receptor complexes into nuclear chromatin. The temperature-dependence of the binding of androgen-receptor complexes into chromatin is essentially due to a major change in cytoplasmic receptor complex before its attachment to nuclear chromatin. 5. The resolution of these analytical procedures was sufficient to enable a critical comparison of the receptor proteins from different male accessory glands to be undertaken. From these studies, no substantial evidence in support of the tissue specificity of androgen receptors could be established; rather the receptors from different androgen-dependent glands were remarkably similar in physicochemical properties. 6. Although the methods were initially developed for the partial purification of androgen-receptor complexes, they are equally suitable for the prompt and extensive purification of oestrogen-receptor and progesterone-receptor complexes.     

The control of the form and function of the ribosomes in androgen-dependent tissues by testosterone

1. The ribosome content of the rat ventral prostate gland is controlled by the concentrations of circulating androgens and the polyribosomal complement of the total population of ribosomes is acutely dependent on androgenic stimulation. After the administration of testosterone to castrated rats in vivo, there is a pronounced increase in the amounts of heavy (150-240S) polyribosomes. 2. These results are consistent with a pronounced increase in the mRNA and rRNA content of the prostate gland after the administration of testosterone in vivo. 3. From studies conducted both in vitro, the heavy prostate polyribosomes formed after androgenic stimulation are particularly active in protein synthesis. 4. The androgen-stimulated increase in the formation of prostate polyribosomes has a mandatory requirement for sustained RNA and protein synthesis. 5. Since the androgen-mediated increase in prostate polyribosomes may also be suppressed by the concomitant administration of certain anti-androgenic steroids in vivo, the response in polyribosome formation is probably initiated by the binding of a metabolite of testosterone, 5alpha-dihydrotestosterone, in the prostate gland. 6. The relevance of these findings to the pronounced increase in protein synthesis in androgen-dependent tissues after hormonal stimulation is discussed.     

Further studies on the stimulation of protein synthesis in androgen-dependent tissues by testosterone

1. By using centrifugation through a discontinuous sucrose gradient, four microsomal fractions are obtained from the prostate gland. 2. Administration of androgens to castrated rats stimulates protein synthesis in all fractions, particularly in the heavy rough fraction. 3. Androgens also increase the content of protein, RNA and phospholipid in the heavy rough fraction. 4. Time-course experiments in vivo show that androgens induce a rapid increase in the synthesis of ribosomal precursor RNA preceding the synthesis of new microsomal fraction and the increase in protein synthesis.