ECOLOGICAL ASPECTS OF ADAPTIVE RADIATION IN BIRDS

1. Relatively few birds feed heavily upon green-plant materials, though a number may take substantial numbers of buds. Birds appear not to possess adequate gut biota to break down cellulose efficiently, and even it they did, this system would not be compatible with efficient flight, on account of the long processing times required. 2. Birds have stronger adaptations toward feeding upon seeds and make a particularly heavy impact upon seeds in trees and on those in widely scattered or unpredictable crops. 3. Several families, mostly of tropical distribution, feed primarily upon fruit. Again, they are most successful in exploiting resources reached only with difficulty by other groups. A similar pattern holds for nectar stores. In the case of fruit and nectar, evolutionary complications result because the plants compete for seed dispersers and pollinators. 4. Most primarily herbivorous species feed their young partially or totally upon insects or other animal foods. Only a few species are able to fledge upon an entirely herbivorous diet, and those that do so often have extremely long fledging periods, which subject their young to high rates of predation unless the parents nest in places inaccessible to predators. 5. In general, herbivorous birds make a heavy impact relative to other animals only when they exploit resources that the other groups have difficulty in obtaining (hard to reach, or widely scattered in space and/or time). 6. Insects are exploited by more families of birds than any other food category. Birds are of greatest relative importance in capturing insects on the wing and in arboreal locations. Other terrestrial invertebrates are probably taken by techniques similar to those used for insects. 7. A variety of species take invertebrate prey along the water's edge or in shallow water. 8. Almost without exception, vertebrate prey is of small size, in part a function of the size of birds. Occasionally predation upon small terrestrial vertebrates may be relatively heavy, generally in outbreak situations. 9. Several families feed exclusively upon fish, crustacea, squid, and other aquatic prey. Some indirect evidence suggests that exploitation of these resources may sometimes be heavy, though there is little evidence that these groups often make an appreciable impact upon this food source. 10. Birds appear to be among the most important scavengers of animal remains. 11. Like the herbivorous birds, carnivorous birds appear to exert their greatest impact upon resources that are hard to reach or are widely scattered in space and/or time. 12. One-third of the avian families feed regularly on a variety of resources, as recognized in Table I. Most of these families specialize upon resources located in certain areas (ground, water's edge, trees, etc.). Only 13% of these families regularly use such a wide range of foods that they transcend both of these considerations (food type, segment of the habitat). In very few cases (5 %) does this designation result from some species of a family specializing upon one category of food and others using a different category. 13. There have been few large (> 20 kg), primarily herbivorous birds, though there have been several large omnivorous species. Large carnivorous species have been even rarer. All of these large species have been flightless, and in most cases they have occurred when or where large mammals were scarce or absent. 14. Birds have made extremely limited use of subterranean areas, caves, or deep water, and adaptations facilitating other types of life appear to be virtually incompatible with success in these situations. All these areas are characterized by a rapidly decreasing food gradient. 15. Bats exploit certain, but not all, of the food resources regularly exploited by birds. The resources not used by bats that are exploited by birds are those that are available over a full 24 h period; thus, bats' nocturnal habits do not provide them with an advantage in exploiting them. 16. Insects also use some of the resources exploited by birds. With few exceptions, insects are smaller than birds or bats. Considerable indirect evidence is consistent with the argument that the segregation in time, resource type, and size of flying animals is at least in part caused by competition. 17. While selection for anti-predatory mechanisms can be surmised, the reciprocal density relationships frequently noticed between birds and other organisms suggest that they arise from competition, rather than predation. 18. Most information suggests that interactions between birds and other animals of the same trophic level are usually, though not invariably, over food. 19. The types of relationship existing between birds and other organisms described above are repeated in a variety of other animal groups, though they clearly are not ubiquitous in the animal kingdom.     

FUNCTIONAL AND EVOLUTIONARY ASPECTS OF THE POSTCRANIAL ANATOMY OF DICYNODONTS (SYNAPSIDA, THERAPSIDA)

Abstract:  Restoration of the major skeletal muscles and functional morphological analysis of the postcranium were carried out on two Triassic dicynodont genera, Wadiasaurus and Lystrosaurus . A phylogenetic analysis of 12 selected Permian and Triassic dicynodont taxa was conducted and the postcranial character states were then mapped onto the most parsimonious tree. The analysis revealed changes in pectoral girdle and forelimb morphology, which included reduction of the coracoid plate, increasing robustness of the deltopectoral crest, change in humeral orientation from lateral to caudolateral, increasing prominence of the humeral head, and increasing robustness of the radius. Such changes can be associated with a functional tendency to reduce the lateral component of the propulsive force while still in an abducted mode. On the other hand, changes associated with the pelvic girdle included expansion of the preacetabular iliac process, reduction of the postacetabular iliac process, craniocaudal expansion of the iliac blade, change in the shape of the pubis from flat and plate-like to small and rod-like with a cranial process, and change in acetabular orientation from lateral to caudolateral. The femoral head, starting from a cranioproximal position, progressively became dorsally pronounced and offset from the body. Other features/changes associated with the femur included increasing robustness of the trochanter major, and increasing flattening of the femoral midshaft. Changes in the axial skeleton included increasing stiffening of the trunk to reduce lateral undulations, increasing dorsoventral flexion, and increasing sacral vertebral count, which can be correlated with the preacetabular iliac expansion. These findings suggest that the dicynodont postcranial skeleton evolved towards more upright hindlimb morphology with the body held well off the ground.     

中国中生代鸟类的体重估计及其演化趋势

体重是一项重要的生物学指标,生物的体重受到发育、繁殖和进化等诸多因素的影响。对于灭绝生物体重的估计有助于进一步恢复它们的各种生物学信息。本研究采用统计学的方法,对422件现生鸟类(分属于21目229种)的体重和18项骨骼量度指标分别进行一元回归分析,结果显示判定系数的分布范围在0.5～0.91之间,多数指标的判定系数均集中在0.8～0.9之间。采用另外64件测量有体重数据和骨骼量度的鸟样本对回归方程的估算准确率进行检验,发现前肢中肱骨长度和尺骨宽度以及后肢中胫跗骨宽度3项指标的估算准确率高于其他指标。分析结果还表明前肢两项指标对于估算鸣禽、猛禽和攀禽类等树栖鸟类的体重准确率较后肢显著;后肢指标对于估算陆禽类等地栖鸟类体重的准确率高于前肢指标。这一结果反映出与体重相关程度较高的骨骼量度指标在不同习性的鸟类当中存在着一定的差异。对于化石鸟类的体重估计,采用估算准确率较高并且便于测量的肱骨长度和胫跗骨宽度两项回归方程加以计算。通过对中国中生代鸟类的体重进行估算,结果显示中生代鸟类在系统发育过程中,反鸟类经历了体重逐渐减轻的过程,而今鸟类的体重开始不断增大并且出现显著的分异。     

THE UTILIZATION OF GUM TREES BY BIRDS IN AFRICA

The changes brought about by the introduction of Eucalyptus into Africa on the ecology of birds are outlined, in so far as its contribution as a habitat, as a food-source, and for other uses is concerned. Species known to breed in gums are listed, together with notes on habitat preference, and its limitations in comparison with the indigenous resources are discussed.     

MASS ESTIMATE AND EVOLUTIONARY TREND IN CHINESE MESOZOIC FOSSIL BIRDS

体重是一项重要的生物学指标,生物的体重受到发育、繁殖和进化等诸多因素的影响.对于灭绝生物体重的估计有助于进一步恢复它们的各种生物学信息.本研究采用统计学的方法,对422件现生鸟类(分属于21目229种)的体重和18项骨骼量度指标分别进行一元回归分析,结果显示判定系数的分布范围在0.5 ～0.91之间,多数指标的判定系数均集中在0.8 ～0.9之间.采用另外64件测量有体重数据和骨骼量度的鸟样本对回归方程的估算准确率进行检验,发现前肢中肱骨长度和尺骨宽度以及后肢中胫跗骨宽度3项指标的估算准确率高于其他指标.分析结果还表明前肢两项指标对于估算鸣禽、猛禽和攀禽类等树栖鸟类的体重准确率较后肢显著;后肢指标对于估算陆禽类等地栖鸟类体重的准确率高于前肢指标.这一结果反映出与体重相关程度较高的骨骼量度指标在不同习性的鸟类当中存在着一定的差异.对于化石鸟类的体重估计,采用估算准确率较高并且便于测量的肱骨长度和胫跗骨宽度两项回归方程加以计算.通过对中国中生代鸟类的体重进行估算,结果显示中生代鸟类在系统发育过程中,反鸟类经历了体重逐渐减轻的过程,而今鸟类的体重开始不断增大并且出现显著的分异.     

ASSESSMENT OF EVOLUTIONARY AFFINITIES IN GOSSYPIUM BY PROTEIN ELECTROPHORESIS

Protein band patterns from 25 species of Gossypium were obtained by electrophoresis of crude seed extracts on polyacrylamide gel. Band homologies between species were verified by electrophoresis of a mixture of their extracts. The patterns were found to be largely consistent with the conventional classification of the diploids into 6 genomic groups, A–F. However, G. triphyllum and G. bickii showed unique patterns differing respectively from those of the B and C groups, and G. australe showed closer affinity with the Arabian E- than with the Australian C-genome species. Affinities among the D-genome species were different from those implied by their former grouping into taxonomic sections but remarkably similar to those indicated in the most recent taxonomic revision of the genus. They were classifiable into two subgroups, β and ɛ. The clustering pattern of the diploids based on correlation coefficients calculated from densitometer curves of the electrophoretic spectra suggested that the genomic groups were derived from an African progenitor type, and that the American β and ɛ subgroups, most closely related to the African B- and the Arabian E-genome groups respectively, evolved under comparative mutual isolation, possibly separated by the Tertiary Amazonas basin.