Putting ourselves in a striped snake's shoes: thermal sensitivity of locomotor performance in a melanistic/striped colour-dimorphic snake

Intermorph differences of thermoregulatory abilities in colour-polymorphic (dimorphic) species have been demonstrated in many ectotherms. Usually, these studies reported slower body warming in pale-coloured morphs than in dark-coloured morphs. Under this circumstance, one way in which pale-coloured individuals can manage their slower body warming is to perform better at lower temperatures than dark-coloured individuals. If this is the case, the former need not necessarily raise their body temperature to the same level as the latter. Based on this scenario, intermorph differences in thermal sensitivity of performance were examined using the melanistic/striped colour-dimorphic snake Elaphe quadrivirgata as a model species. As an indication of performance capability, the crawling speed was measured at several temperatures. Although striped individuals exhibited slower body warming than melanistic individuals under experimental conditions, the former did not exhibit faster crawling speed than the latter at lower temperatures. Shape and position of the performance curve were almost identical between melanistic and striped individuals, indicating a highly static nature in thermal sensitivity of crawling. Coupled with the results of field studies, it is suggested that striped individuals manage their slower body warming by efforts of behavioural thermoregulation. The possible significance of ecological performance in the wild was discussed.     

The determination of larval phase coloration in the African armyworm, Spodoptera exempta and its consequences for thermoregulation and protection from UV light

Spodoptera exempta exhibits a density-dependent phase polyphenism in which caterpillars reared in isolation (phase solitaria) tend to be green/brown and cryptic while those reared in groups (phase gregaria) are black and highly visible. Differences in coloration between solitaria and gregaria phase larvae become apparent in the third instar and are pronounced by the final instar. Larval rearing densities as low as two larvae per 250 ml container are sufficient to induce gregaria coloration in 61% of the insects and at higher densities this is the only coloration expressed. Larvae transferred from isolated to crowded conditions or vice versa tend to retain or adopt gregaria phase coloration which suggests that this is highly advantageous. Black coloration is also induced in single larvae reared with other species of caterpillar (S. littoralis). Isolated larvae reared at low temperature tend to become melanic while crowded larvae reared at high temperature tend to be less melanised although they do not adopt the solitaria phase coloration. These results suggest that phase coloration is determined by non species-specific inter-larval contact, although it can be modulated by temperature. Under laboratory conditions, gregaria phase larvae heat up faster than solitaria; this is partially a consequence of their black coloration but their smaller size is a more important factor. The cuticles of the gregaria larvae absorb significantly more ultraviolet radiation than those of solitaria but this does not confer any protection when larvae are irradiated at 254 nm.     

Variation and seasonal changes in hoverfly species: interactions between temperature, age and genotype

Eristalis tenax L. and E. intricarius L. are two hoverflies which vary considerably in colour pattern. Whilst much of the phenotypic variation in both species is due to genetic variation at major gene loci, there are interactions with pupal temperature and with age of adult. Low pupal temperatures produce, on average, darker abdominal patterns in E. tenax , although the effect is hard to pick out in natural populations. Changes of pattern with age convert a bimodal autumn population to a unimodal post-hibernation population in the following spring. Hair colour is also made darker by cold treatment. Pupal treatments have a strong effect on hair colouration in E. intricarius. High temperatures inhibit the production of black hairs on the thorax, but not all the genotypes are equally sensitive to temperature. Seasonal fluctuations in colour pattern frequencies are detectable in E. intricarius. In three Eristalis species that have been studied so far, the interactions between genotype, age and temperature operate in quite different ways. The temperature responses may be relevant to theories of thermal melanism, although the colour pattern polymorphisms are, more obviously, examples of Batesian mimicry.     

On the selective forces acting in the industrial melanism of Biston and Oligia moths (Lepidoptera: Geometridae and Noctuidae)

Melanic and typical morphs of Biston betularius (L.), Oligia latruncula (D. & S.) and 0. strigilis (L.) made choices between vertical trunks and horizontal branches, sprayed with white and black paints, in a transparent plastic cylinder in natural illumination. The moths settled in exposed positions. In neither Biston nor Oligia did the choice for white/black backgrounds differ between the morphs. Biston moths settle on narrow branches (not on twigs) with the body at right angles to the longitudinal axis of the branch. The Oligias showed an asymmetrical light reaction: one eye is kept in shadow so that they settle as a continuation of an irregularity of the surface, often of a lichen.
In nature, Biston betularius probably rests high up in the canopies, on the under surfaces of horizontal branches. The visual selection acting on the morphs is expected to be less intensive than that measured on tree trunks. The mark-release-recapture results of Kettlewell (1955a, 1956) do not show any qualitative change during the self-determination of the moths but the material is too limited for firm conclusions.
Newly-hatched Biston males take off straight from the trunk where they have expanded their wings but the females may climb higher in the tree. A hypothesis is presented to explain the black-and-white coloration of f. carbonaria : the short-winged moths climbing up the trunks might deter bird predation.     

泰山南北坡植物物种多样性垂直梯度格局的比较

以泰山南北坡14块样方的调查资料为基础,分析了泰山植物物种多样性沿海拔梯度的分布格局。结果表明:在相同海拔范围内,南坡物种丰富度大于北坡,泰山物种丰富度随海拔的升高而减少。整个群落及不同层次的物种多样性沿海拔梯度在泰山南北坡呈现不同的分布格局。在人为干扰程度低的情况下,北坡的群落物种丰富度在各个层次均较高,而多样性指数在各个层次不一样,北坡乔木层的多样性指数较南坡低,但灌木层和草本层则是北坡明显大于南坡。整体上,物种多样性指数与海拔的相关性,北坡要比南坡好。     

Selective bird predation on the peppered moth: the last experiment of Michael Majerus

Colour variation in the peppered moth Biston betularia was long accepted to be under strong natural selection. Melanics were believed to be fitter than pale morphs because of lower predation at daytime resting sites on dark, sooty bark. Melanics became common during the industrial revolution, but since 1970 there has been a rapid reversal, assumed to have been caused by predators selecting against melanics resting on today's less sooty bark. Recently, these classical explanations of melanism were attacked, and there has been general scepticism about birds as selective agents. Experiments and observations were accordingly carried out by Michael Majerus to address perceived weaknesses of earlier work. Unfortunately, he did not live to publish the results, which are analysed and presented here by the authors. Majerus released 4864 moths in his six-year experiment, the largest ever attempted for any similar study. There was strong differential bird predation against melanic peppered moths. Daily selection against melanics (s ≈ 0.1) was sufficient in magnitude and direction to explain the recent rapid decline of melanism in post-industrial Britain. These data provide the most direct evidence yet to implicate camouflage and bird predation as the overriding explanation for the rise and fall of melanism in moths.     

A bird’s eye view of the peppered moth

Industrial melanism in Biston betularia is one of the best known examples of the role of natural selection in evolution and has received considerable scrutiny for many years. The rise in frequency of the dark form of the moth (carbonaria) and a decrease in the pale form (typica) was the result of differential predation by birds, the melanic form being more cyptic than typica in industrial areas where the tree bark was darkened by air pollution. One important aspect of early work evaluating the relative crypsis of the forms of B. betularia on tree trunks with different lichen flora was the reliance on human observers. Humans, however, do not have the same visual capabilities as birds. Birds have well‐developed ultraviolet (UV) vision, an important component of their colour processing system that affects many aspects of behaviour, including prey detection. We examined the UV characteristics of the two forms of B. betularia and a number of foliose and crustose lichens. In human visible light the speckled form typica appeared cyptic when seen against a background of foliose lichen, whereas the dark form carbonaria was conspicuous. Under UV light the situation was reversed. The foliose lichens absorbed UV and appeared dark as did carbonaria. Typica, however, reflected UV and was conspicuous. Against crustose lichens, typica was less visible than carbonaria in both visible and UV light. These findings are considered in relation to the distribution and recolonization of trees by lichens and the resting behaviour of B. betularia.     

长白山红松臭冷杉光谱反射随海拔的变化

为了研究红松、臭冷杉光谱反射率随海拔梯度的变化,本研究使用光谱仪测量了长白山两种主要的针叶树种红松、臭冷杉不同海拔针叶的光谱反射率,分别对比了两个树种不同海拔间光谱反射率、光谱指数的差异,这些特征可以反映植物叶片色素组成和色素含量等信息。结果表明：两种针叶树在不同海拔的光谱反射率变化明显,光谱指数也有显著差异,证明相关生理状况发生明显变化。对比各海拔光谱反射率发现,1279m处红松、臭冷杉针叶的色素总含量较高,叶绿素指数反映出748m处红松、臭冷杉针叶叶绿素含量显著高于1040m和1279m处,Car：Chl指数的差异说明红松、臭冷杉均在748处受到较弱的胁迫,臭冷杉在1040m受到较强的胁迫,对比各波段反射率随海拔的变化,发现红松、臭冷杉针叶色素含量都随海拔变化有明显的变化,而且臭冷杉的叶片水分含量、叶片结构也可能容易受到海拔影响。