Population genetic structure in migratory sandhill cranes and the role of Pleistocene glaciations

Previous studies of migratory sandhill cranes (Grus canadensis) have made significant progress explaining evolution of this group at the species scale, but have been unsuccessful in explaining the geographically partitioned variation in morphology seen on the population scale. The objectives of this study were to assess the population structure and gene flow patterns among migratory sandhill cranes using microsatellite DNA genotypes and mitochondrial DNA haplotypes of a large sample of individuals across three populations. In particular, we were interested in evaluating the roles of Pleistocene glaciation events and postglaciation gene flow in shaping the present-day population structure. Our results indicate substantial gene flow across regions of the Midcontinental population that are geographically adjacent, suggesting that gene flow for most of the region follows an isolation-by-distance model. Male-mediated gene flow and strong female philopatry may explain the differing patterns of nuclear and mitochondrial variation. Taken in context with precise geographical information on breeding locations, the morphologic and microsatellite DNA variation shows a gradation from the Arctic-nesting subspecies G. c. canadensis to the nonArctic subspecies G. c. tabida. Analogous to other Arctic-nesting birds, it is probable that the population structure seen in Midcontinental sandhill cranes reflects the result of postglacial secondary contact. Our data suggest that subspecies of migratory sandhills experience significant gene flow and therefore do not represent distinct and independent genetic entities.     

两种鹤科动物MHC-Ⅰ基因高变区的对比分析

主要组织相容性复合体（MHC）是脊椎动物基因组中高度多态的基因家族,其编码产物在脊椎动物免疫系统中起着重要作用。受湿地生境污染和破坏等因素的影响,全球现存鹤科（Gruidae）动物大都已处于受胁状态。为了解鹤科动物MHC-I基因序列信息,本研究设计通用引物对灰鹤（Grus grus）和肉垂鹤（Bugeranus carunculatus）MHC-I基因进行分离。结果从1只灰鹤和1只肉垂鹤血液基因组中分别分离到2条和3条长约1 500 bp的序列片段,这暗示鹤科动物至少存在两个MHC-I基因座位。分离到的核苷酸序列均可翻译成正常的氨基酸,表明它们具有一定的生物学功能。MHC-I抗原结合区的核苷酸和氨基酸变异率,灰鹤分别为5.0%和9.6%,肉垂鹤为9.1%和14.6%。两种鹤抗原肽结合位点的非同义替代率与同义替代率的比值分别为7.348 8和2.145 2,表明其受到强烈的正选择作用。贝叶斯系统发生树显示,鹤科动物MHC-I基因并未按物种聚类,暗示MHC-I基因跨物种多态性的存在。本研究获得的MHC-I基因通用引物及序列信息,可为今后濒危鹤科动物的保护遗传学研究奠定基础。     

Migrate small,sound big: functional constraints on body size promote tracheal elongation in cranes

Organismal traits often represent the outcome of opposing selection pressures. Although social or sexual selection can cause the evolution of traits that constrain function or survival (e.g. ornamental feathers), it is unclear how the strength and direction of selection respond to ecological shifts that increase the severity of the constraint. For example, reduced body size might evolve by natural selection to enhance flight performance in migratory birds, but social or sexual selection favouring large body size may provide a countervailing force. Tracheal elongation is a potential outcome of these opposing pressures because it allows birds to convey an auditory signal of exaggerated body size. We predicted that the evolution of migration in cranes has coincided with a reduction in body size and a concomitant intensification of social or sexual selection for apparent large body size via tracheal elongation. We used a phylogenetic comparative approach to examine the relationships among migration distance, body mass and trachea length in cranes. As predicted, we found that migration distance correlated negatively with body size and positively with proportional trachea length. This result was consistent with our hypothesis that evolutionary reductions in body size led to intensified selection for trachea length. The most likely ultimate causes of intensified positive selection on trachea length are the direct benefits of conveying a large body size in intraspecific contests for mates and territories. We conclude that the strength of social or sexual selection on crane body size is linked to the degree of functional constraint.     

Characterisation of 14 blue crane <Emphasis Type="Italic">Grus paradisea</Emphasis> (Gruidae,AVES) microsatellite loci for use in detecting illegal trade

Forty-two unique microsatellite loci were isolated from an unenriched and a tetranucleotide-enriched blue crane (Grus paradisea) genomic library. Fourteen polymorphic loci were characterised in 20 unrelated wild blue crane individuals from the Karoo region, South Africa, and displayed 4–27 alleles with observed heterozygosities ranging between 0.50 and 0.95. All 14 loci were also polymorphic in the grey-crowned crane (Balearica regulorum) and the wattled crane (Grus carunculatus). These markers are aimed at assisting the identification of illegal trade in the blue crane but have wider population and conservation applications for most, if not all, crane species.     

Genome sizes of cranes (Aves: Gruiformes)

The DNA content of blood cell nuclei of 15 species of cranes was determined by Feulgen-DNA cytophotometry. Genome sizes agree with values reported elsewhere for several crane species analyzed by flow cytometry. Males have more DNA per cell than females in several species. A karyotype where 2n = 80 is reported for a male greater sandhill crane.     

世界鹤类系统检索

本文把全世界的15种鹤,加以全面的系统检索。对鹤类不仅从其外观形态特征,而且从比较解剖及声调等,进行检索。这样做,认为还是首次的。     

鹤科鸟类鸣声特征的演化

本文在分析鹤科(Gruidae)鸟类鸣声特征的基础上,结合其分子系统树,重建了鸣声特征的演化,并检验了体重与鸣声特征及鸣声特征之间在演化上的相关性。同时比较了体重与鸣声特征在物种间的关系。演化支上各物种体重的变化与鸣声时长特征的变化存在显著的关联(对数线性模型,似然比=9.69,P=0.002;Cohen′s d=1.48):体重的增加伴随着鸣声时长的增加。鸣声特征之间在演化上没有显著的关联(对数线性模型,似然比≤0.15,P≥0.701;Cohen′s d≤0.17)。在物种间鸣声时长与体重存在显著的正相关(Pearson相关分析,r=0.54,P=0.048;Cohen′s d=1.27);鸣声的主频特征与体重存在显著的负相关(Pearson相关分析,r=﹣0.56,P=0.036;Cohen′s d=1.37)。本文以鹤科鸟类鸣声为例,分析了非鸣禽鸟类鸣声特征的演化,及影响鸣声特征的因素。     

Microsatellite loci characterized in three African crane species (Gruidae, Aves)

Forty-three microsatellite loci originally isolated in Grus americana and G. japonensis were tested for polymorphism in the blue crane (G. paradisea). Amplified products were sequenced in the blue crane to aid in the design of blue crane-specific primers. When characterized in 20 unrelated blue crane individuals from South Africa, 14 loci were polymorphic, with each locus displaying between 2 and 7 alleles. Eight polymorphic loci were characterized in the grey-crowned crane (Balearica regulorum) and ten in the wattled crane (G. carunculatus).     

The distinction between the extinct Pleistocene European Crane,Grus primigenia,and the extant Asian Sarus Crane,G. antigone

In contradiction with the conclusions of some previousworkers, the extant Sarus Crane, Grus antigone (L.), and the extinct large Crane, Grus primigeniaMilne-Edwards, from the Pleistocene of Europe, cannot be considered as conspecific. In fact, the tibiotarsal epicondyles, particularly the medial epicondyle, the distal end of the humerus, its ventral epicondyle and the adjoining process, are comparatively smaller in Grus primigenia. These findings indicate differences in locomotion.     

Ontogeny of calls of a nonpasserine species: the grey crowned crane Balearica regulorum gibbericeps

This study presents the results of preliminary studies on the ontogeny of two of the three calls of chicks of the grey crowned crane Balearica regulorum gibbericeps. The observed patterns are consistent with those presented in other studies of nonpasserine bird species in that the frequency range decreased in both investigated calls. The duration, however, showed fluctuations in the contact call and no consistent pattern. In the begging call of captive chicks the duration increased as is found in other nonpasserine bird species.