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101.
In order to transmit aerodynamic forces to the rest of the body, tail feathers need to be stiff to resist lift forces with minimum deformation. Because delta-wing theory predicts that such feathers do not produce lift forces beyond the point of the maximum continuum width of the tail, species with pintails should not require stiff central rectrices distal to that point. We tested this prediction by comparing the relative thickness of the central rectrix rachis in taxa with pintails and triangular tails. Fourteen pairs of closely related species or species groups belonging to the families Phaethontidae, Phalacrocoracidae, Anatidae, Stercorariidae, Psittacidae, Trochilidae, Alcedinidae, Momotidae, Meropidae, Bucerotidae, Tyrannidae, Pipridae and Nectariniidae were compared. Twelve of the phylogenetically independent comparisons showed that the taxa with triangular tails have higher relative rachis thickness (RRT) than their pintailed relatives just behind the point of the maximum continuum width of the tail. In contrast, two taxa with pintails showed proportionately higher RRT than their triangular-tailed relatives. Triangular tails showed an approximately linear relationship between RRT and relative rachis length, which contrasts with a proportionately greater increase in RRT from distal to proximal parts of the feather in 12 pintailed taxa. These results show that in most of the pintailed taxa studied the distal part of the central rectrix rachis has not been selected to resist lift forces and may be adaptively reduced to attenuate the costs of a hypertrophied ornament. However, the presence of distally reinforced rachices in Eumomota superciliosa and Colonia colonus suggests that a different explanation may be required to account for the design of pintail structure in other taxa.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 477–485.  相似文献   
102.
DURING our work on Chemotaxis of leucocytes, we have consistently noted that coagulation of normal blood from various species leads to the generation or liberation of leuco-tactic factors. Chromatographic purification of normal rabbit sera has led to the isolation of a low molecular weight neutrophil specific factor and a high molecular weight macrophage specific factor1. The origin and mechanism of formation of these serum leucotactic agents remained unclear. In view of the known accumulation of leucocytes, especially neutrophils, around thrombi and the occurrence of coagulation in immunologically and nonimmunologically induced inflammatory processes, we have investigated the link between coagulation and Chemotaxis.  相似文献   
103.
The braconid subfamily Doryctinae (Hymenoptera) is a cosmopolitan, species‐rich group of parasitoid wasps whose known species richness and morphological diversity is mainly concentrated in the Neotropical region. Among the doryctine taxa that are endemic to this region, there is a group of six genera (the Pedinotus genus group) that are mainly characterized by having lateral, posteriorly converging or subparallel grooves on the second metasomal tergite (including Gymnobracon Szépligeti, Hybodoryctes Szépligeti, Lamquetia Braet et van Achterberg, Osmophila Szépligeti, Pedinotus Szépligeti and Trigonophasmus Enderlein). Most of these genera were described more than a century ago, and thus their limits and diagnostic morphological features are not well defined. We present an analysis of the phylogenetic relationships among various representative species of five of the six genera belonging to the Pedinotus genus group based on one mitochondrial (cytochrome oxidase I) and two nuclear (28S, Wingless) gene markers. We also estimated the timing of origin and diversification within the group and investigated the external morphology of the genera involved in order to determine reliable identification characters. The group as a whole, whilst being recovered as monophyletic with the inclusion of Acanthorhogas Szépligeti, was not statistically supported. However, the respective monophyly of all of the morphologically supported genera are confirmed, as are the intergeneric relationships (Gymnobracon, Trigonophasmus) ((Acanthorhogas, Osmophila) (Lamquetia, Pedinotus)). We propose that the pattern of sublateral grooves or depressions appears to be a useful systematic character for recognition of an endemic Neotropical radiation that could have originated c. 41–27 Ma. We redescribe six of the seven genera that we recognize for the Pedinotus genus group and provide a key to enable their identification.  相似文献   
104.
1. Ants using trails to forage have to select between two alternative routes at bifurcations, using two, potentially conflicting, sources of information to make their decision: individual experience to return to a previous successful foraging site (i.e. fidelity) and ant traffic. In the field, we investigated which of these two types of information individuals of the leaf‐cutting ant Acromyrmex lobicornis Emery use to decide which foraging route to take. 2. We measured the proportion of foraging ants returning to each trail of bifurcations the following day, and for 4–7 consecutive days. We then experimentally increased ant traffic on one trail of the bifurcation by adding additional food sources to examine the effect of increased ant traffic on the decision that ants make. 3. Binomial tests showed that for 62% of the trails, ant fidelity was relatively more important than ant traffic in deciding which bifurcation to follow, suggesting the importance of previous experience. 4. When information conflict was generated by experimentally increasing ant traffic along the trail with less foraging activity, most ants relied on ant traffic to decide. However, in 33% of these bifurcations, ants were still faithful to their trail. Thus, there is some degree of flexibility in the decisions that A. lobicornis make to access food resources. 5. This flexible fidelity results in individual variation in the response of workers to different levels of ant traffic, and allows the colony to simultaneously exploit both established and recently discovered food patches, aiding efficient food gathering.  相似文献   
105.
Casual observations had shown that, in laboratory cultures, populations of Ceriodaphnia quadrangula (O. F. Muller) rarely persisted for more than a month at most. It is shown here that populations of C. quadrangula can be maintained in static water on a diet of mixed algae (mainly Scenedesmus quadricauda (Turp.) Brev., but if the water is disturbed by a slow current of ascending air bubbles, the numbers of C. quadrangula decline. Death is not, however, immediate, and at high densities populations may persist in disturbed water for several weeks before numbers start to decline. Numbers of C. quadrangula did not decline in disturbed water when the food was changed from the alga Scenedesmus to the animal Artemia salina (L.). Individuals of C. quadrangula in the presence of decomposing naupliar larvae of A. salina grew as well in disturbed as in static water and in static water their numbers increased at a greater rate on this animal diet than on an algal diet of Scenedesmus. When the bacterial populations associated with Scenedesmus were greatly reduced, there was no increase in the numbers of C. quandrangula. Microbes associated with Scenedesmus, and not the alga per se, seem to be used as food by C. quandrangula.  相似文献   
106.
Recent assessments by the International Union for Conservation of Nature (IUCN) indicate the existence of about 612 recognized primate species and subspecies (IUCN RedList, 2012), but close to 50% of these taxa are at risk of extinction as a result of human action. In this article, I call attention to underlying regional and global socioeconomic contexts of primate conservation. Using information from FAO and UN databases and other sources, I examine, for the Neotropics, sub‐Saharan Africa, and Southeast Asia, trends in forest loss and human demographics and social condition, discuss the impact of global market pressures upon primate habitats, and examine land‐use patterns that may favor primate conservation. Between 1990 and 2010, an estimated 149 million ha of forest were lost in the three regions and additional losses are expected in the future. Global human population will increase from 7 billion in 2012 to 9 billion in 2050. Currently, 2 billion people live in the three primate range regions under high levels of poverty. Large‐scale deforestation is related to global market demands, especially from developed and developing nations, for food (e.g., cattle), domestic animal feed (e.g., soybeans), biofuel‐based crops (e.g., oil palm), and industrial round wood. The growth of protected areas in the three regions has been steady for several decades, but it is not enough to ensure long‐term conservation of many primate taxa. Other conservations tools involving sustainable land use and biodiversity conservation corridors are required at the landscape level. The above assessment can easily be applied at the local level by primatologists, giving more precision to conservation initiatives. Am. J. Primatol. 75:30‐45, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
107.
Agroecosystems cover more than one quarter of the global land area (ca. 50 million km2) as highly simplified (e.g. pasturelands) or more complex systems (e.g. polycultures and agroforestry systems) with the capacity to support higher biodiversity. Increasingly more information has been published about primates in agroecosystems but a general synthesis of the diversity of agroecosystems that primates use or which primate taxa are able to persist in these anthropogenic components of the landscapes is still lacking. Because of the continued extensive transformation of primate habitat into human‐modified landscapes, it is important to explore the extent to which agroecosystems are used by primates. In this article, we reviewed published information on the use of agroecosystems by primates in habitat countries and also discuss the potential costs and benefits to human and nonhuman primates of primate use of agroecosystems. The review showed that 57 primate taxa from four regions: Mesoamerica, South America, Sub‐Saharan Africa (including Madagascar), and South East Asia, used 38 types of agroecosystems as temporary or permanent habitats. Fifty‐one percent of the taxa recorded in agroecosystems were classified as least concern in the IUCN Red List, but the rest were classified as endangered (20%), vulnerable (18%), near threatened (9%), or critically endangered (2%). The large proportion of threatened primates in agroecosystems suggests that agroecosystems may play an important role in landscape approaches to primate conservation. We conclude by discussing the value of agroecosystems for primate conservation at a broad scale and highlight priorities for future research. Am. J. Primatol. 74:696‐711, 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
108.
109.
A combined morphological, molecular and biological study shows that the weevil species presently named Mecinus janthinus is actually composed of two different cryptic species: M. janthinus Germar, 1821 and M. janthiniformis To?evski & Caldara sp.n. These species are morphologically distinguishable from each other by a few very subtle morphological characters. On the contrary, they are more readily distinguishable by both molecular and biological characters. A molecular assessment based on the mitochondrial DNA cytochrome oxidase subunit II gene revealed fixed differences between the two species with p‐distances between samples of both species ranging from 1.3 to 2.4%. In addition to this, the larvae of the two species are found to develop on different species within the genus Linaria (Plantaginaceae): M. janthinus is associated with yellow toadflax (L. vulgaris) and M. janthiniformis with broomleaf toadflax (L. genistifolia) and Dalmatian toadflax (L. dalmatica). Molecular and host use records further suggest the occurrence of a third species associated with L. vulgaris within M. janthinus, sampled from north Switzerland, central Hungary and east Serbia. The significance of these new findings is of particular importance because species of the M. janthinus group are used, or are potential candidates, for the biological control of invasive toadflaxes in North America.  相似文献   
110.
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