加拉帕戈斯群岛同域达尔文雀种群的进化动态

本文主要论述物种形成的三个阶段 :建群、线形分异和生殖隔离。首先介绍一项通过时间产生分异的调查 ,然后检测种群间基因交流的障碍 ,最后描述一个自然事件从而分析建群过程。本项工作是在加拉帕戈斯群岛中的达芬梅杰岛上长期研究达尔文雀进化工作的一部分 ,研究组成员由格兰特、笔者和其他同事组成。岛上发生适应辐射的时间并不长 ,现存的 1 4种达尔文雀由 2 0 0或 3 0 0万年前的一个祖先分化而成。极端的年间气候波动改变了达尔文雀的生态条件和食物供给。达尔文雀种群受到这些变化的影响 ,通过重复的进化反应 ,发生了自然选择。通过 3 0年的积累 ,中地雀 (Ｇｅｏｓｐｉｚａｆｏｒｔｉｓ)和仙人掌地雀 (Ｇ .ｓｃａｎｄｅｎｓ)种群的体型大小和喙部形状发生了显著的变化。达尔文雀的鸣叫是在幼鸟时期通过学习而形成的 ,类似于印痕过程 ,鸣叫对保持种间的生殖隔离起着一定的作用。但是在一些特殊的生态条件下 ,生殖隔离可以被由于错误印痕所形成的鸣叫而冲破 ,导致种间杂交和基因渗入 ,当然 ,这种情况非常罕见。自然选择可以使基因流从一个物种流动到另一个物种从而增加变异。 1 983年 ,大地雀 (Ｇ .ｍａｇｎｉｒｏｓｔｒｉｓ)在达芬梅杰岛上建群。最初岛上只有拥有共同亲鸟的 2只雄鸟和 1只雌鸟通过不     

Isolation and characterization of microsatellite markers from the panic moth,Saucrobotys futilalis L. (Lepidoptera: Pyralidae: Pyraustinae)

The panic moth is a widely distributed North American pyralid moth with gregarious, nest‐building larvae. Primers for 12 polymorphic microsatellite loci were developed to assay relatedness in nest groups and population structure in the eastern half of the moth's range. Primers were tested on 42 individuals (one from each of 42 nests) collected in the states of New York, Virginia and Georgia. All loci were polymorphic and exhibited varying degrees of allelic variation (4–24 alleles). These primers will enable further research into the social structure of these gregarious caterpillars.     

Mark—Recapture Accurately Estimates Census for Tuatara,a Burrowing Reptile

Abstract: Estimates of population size are necessary for effective management of threatened and endangered species, but accurate estimation is often difficult when species are cryptic. We evaluated effectiveness of mark–recapture techniques using the Lincoln–Peterson estimator for predicting true census size of a population of tuatara (Sphenodon punctatus), a burrowing reptile that is a conservation priority in New Zealand. We found that Lincoln–Peterson estimates (NŇ = 85) were accurate for predicting the census size (N = 87) after only a 3-day mark–recapture survey. We recommend this method as a cost-effective way to accurately estimate population size for isolated, inaccessible tuatara populations, because it requires limited personnel, expertise, and time, and has low environmental impact on fragile sites.     

The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands

Using microsatellite DNA variation, morphological measurements and sonagrams made from tape-recordings in the field, we examine die allopatric differentiation of six populations of the sharp-beaked ground finch, Geospiza difficilis , in the Galapagos archipelago. We ask how and why die populations became differentiated, and consider what die differences imply about speciation. An important factor is time; G. difficilis is one of the phylogenetically oldest species. Populations became differentiated by adapting in beak morphology to different food supplies. Since beak size and shape also function in conspecific mate recognition and choice, die potential for reproductive isolation from sister and parental taxa arose as a correlated effect of natural selection on resource-exploiting traits. This conforms to a standard explanation for the origin of pre-mating isolation as a byproduct of adaptive changes in allopatry without being adaptive itself. However, diis explanation is incomplete. Vocal characteristics also differentiated, partly as a result of natural and sexual selection independent of beak size change in environments with different sound transmitting properties. An additional element of chance is indicated by a comparison of closely-related populations on two islands, Wolf and Darwin, that are geographically close, and topographically and floristically similar. The populations have markedly different vocalizations. Morphological characters, vocalizations and genetic traits do not vary concordandy among die six populations. One population (Genovesa) is genetically more similar to other congeneric species. Phenotypic similarities with G. difficilis are the result of a uniquely long retention of shared ancestral traits. Arguments under the phylogenetic species concept justify recognizing this population as a separate species, Geospiza acutirostris. Under the biological species concept it should remain as currentiy classified, G. difficilis.     

Acoustic adaptations of periodical cicadas (Hemiptera: Magicicada)

We studied the trade-off between traits that function in mate attraction and those that function in enemy avoidance by contrasting features of acoustic communication in cicadas differentially at risk to predators in the same environment. Two genera of North American cicadas were studied: Magicicada and Tibicen. Magicicada species of periodical cicadas, with 17-year life cycles, seek mates in dense aggregations of calling males that are made possible by the relative ineffectiveness of predators to control their numbers. During the breeding season, Magicicada are so abundant that they satiate their predators. From their relative freedom from predation, it is to be expected that traits for attracting mates are emphasized in Magicicada compared with the more solitary genus Tibicen , which reproduce at much lower densities. Males of solitary species are expected to sing more loudly and at low pitch because both features enhance long-distance transmission. These two features were confirmed by measurement. Magicicada septendecim appears to be the most divergent species, evolutionarily, in terms of an unusually sharply tuned sound resonating system, low resonant frequency, and quietness of its song that cannot be entirely explained by body size. These characteristics represent adaptations to the problem of communicating unambiguously to females at close range in a loud and heterogeneous sound environment. Sensitivity to predators, parasitoids, and congeneric species may also have shaped the evolution of their communication systems.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 15–24.     

Opportunistic predation and offspring sex ratios of cicada-killer wasps (Sphecius speciosus Drury)

Abstract.  1. The way in which hunting of prey affects the sex ratio of the predator's offspring is not well understood. Female cicada-killer wasps are convenient for study because they specialise in capturing cicadas to provision their offspring. Cicada prey are nearly twice as heavy as the wasps that carry them, hence some degree of prey selectivity by the wasps is to be expected. It has been suggested that wasps bias their offspring towards females by foraging selectively for female prey, whereas there is some evidence that sex ratios are actually male-biased. This study was designed to establish the connection between foraging and offspring sex ratio.
2. Three, non-exclusive, hypotheses of selective predation were tested. The frequency of predation on different classes of prey in conjunction with their availability was estimated by intercepting the wasps on their way to their nests and by sampling cicadas in the environment. The hypothesis of selective predation was not supported; predation appears to be opportunistic and non-selective. Cicada prey weight was not a simple linear function of wasp weight, although the smallest wasps were constrained to carry small prey.
3. Wasp offspring (larvae) were excavated from subterranean nests and found to be male-biased (3 : 1 or 4 : 1) in 2 years. The observed ratios are close to expectation from Fisher's equal-investment model, taking account of sexual size dimorphism, and are evidently unrelated to the sex of the prey. A simple binomial probability rule of sex allocation provides a behavioural mechanism for producing the observed sex ratio of offspring.     

Change in habitat resources and structure near urban edges and its influence on the squirrel glider (Petaurus norfolcensis) in southeast Queensland,Australia

Urban landscapes often expose wildlife populations to enhanced edge effects where the biotic and abiotic attributes of native ecosystems have been significantly altered. While some species may respond favourably to edges, there are likely to be varying negative consequences for many forest‐dependent species. In particular, marsupial gliders are influenced by changes in forest composition and structure near edges due to highly specific feeding and nesting requirements, and a high reliance on tree cover to traverse a landscape. We addressed this problem using the squirrel glider (Petaurus norfolcensis) in the fragmented urban landscape of southeast Queensland, Australia. Analysis of variance was applied to determine differences in habitat resources and structure in relation to glider presence and trap success rates in forest fragment interiors compared with road (minor & major) and residential edge habitats. We postulate that an increased presence of squirrel gliders in sites adjacent to minor road and residential edges may be due to the availability of additional resources and/or varying dispersal opportunities. Conversely, forest fragment interiors contain a higher abundance of nest hollows and large trees, together with a greater floristic species richness providing more reliable seasonal foraging sources, which may explain the greater trap success rates of squirrel gliders in these sites. We conclude that while forest fragment interiors provide habitat suitable for year‐round use by greater numbers of squirrel gliders, the conservation value of some edge habitats that provide additional resources and dispersal opportunities should not be underestimated for forest‐dependent mammals; however, each edge type must be assessed individually.     

Preliminary Studies on the Optimum Shape of Dental Bridges

Several pre-existing anterior and posterior dental bridge models using Finite elements and the new ceramic material In-Ceram have been developed. The mechanical behaviour of these models has been compared with optimised profiles obtained from a newly developed evolutionary algorithm known as Evolutionary Structural Optimisation (ESO).

The results show that the mechanical behaviour of the bridges was mainly restricted by the properties of the porcelain veneer and the design of the bridges themselves. For the case of the anterior bridge, it was found that there existed a specific thickness of veneer that minimised the maximum principal stress. This was related to peak stresses that occurred at the bridge surface. Peak stresses also occurred in the material interface between the In-Ceram and the veneer. These extreme stresses were attributed to the notch size and shape. For the case of the posterior bridge, it was concluded that the shape of the bottom of the Pontic tooth is crucial in reducing the magnitude of the maximum principal tensile stress. The ESO process produced bridge designs which have uniformly stressed bridge surfaces, and which also have significantly lower maximum principal tensile stresses compared to the pre-existing designs (up to 44%).