影响食肉目动物能量学的生态因子

在食肉目的62种动物中,体重的变异可以解释基础代谢率86.8%的变化。当栖息基底、食性、生境和纬度等4个因素与体重合起来一起分析,则可以解释基础代谢率98.7%的变化,即这些生态和行为因子可以解释代谢率残差变异的81.1%。身体成分也是影响基础代谢率的另一个因素,可以解释一些大型树栖种类的较低的代谢率。除体重因素外,导致真兽类基础代谢率变异的主要原因是:当生态因素适合时,高水平的能量消耗可以促进动物的高繁殖输出,而动物的某些习性和生存环境则会要求低能量消耗,从而使繁殖率降低。当以科为单元进行分析时,对结果没有影响。生理参数与分类单元之间大多数的相关性反映了生态和行为因素与分类系统之间的一种粗略的相关关系。除非系统学可以反映动物的生态学和行为学,否则系统学不能决定动物适应性特征的状态     

Ecological Adaptations of Mandibular Form in Fissiped Carnivora

Among mammals, Carnivora presents an ideal group for investigating the complex interplay between functional adaptation and phylogenetic history. Here we explore mandibular form and its relationship to ecology and phylogeny using geometric morphometrics applied to mandibles of extant Carnivora. Both mandibular size and shape discriminate carnivoran ecological adaptations (diet, membership to small or large predatory guilds), but the interplay of morphology with phylogenetic history is profound. In general, families do not overlap in mandible shape; however, Viverridae, Herpestidae, Canidae, and Mustelidae exhibit functional and morphological convergence. Mandibular allometric trajectories are distinct among families and ecological categories. Our findings suggest that variability in mandibular form among Carnivora is primarily influenced by major evolutionary changes occurring at the family level and less, but significantly so, by ecological adaptations. Small generalist feeders (insectivores, omnivores) exhibit stronger convergence in mandibular shape than highly specialized predators; bigger taxa, such as bears, evolved unique morphologies constrained by allometric scaling. Thus, the findings of this study serve to demonstrate how ecological factors mold anatomical structures in similar ways to serve similar functions. As such, carnivoran species can be usefully grouped into functional ‘guilds’ in eco-morphological studies irrespective of their phylogenetic history.     

Morphological correlates of tail length in the catarrhine sacrum

Taillessness is a distinctive synapomorphy of the Hominoidea that has implications for interpretation of the locomotor behaviors and phylogenetic affinities of the clade’s earliest members. However, difficulties persist in confidently identifying taillessness in the catarrhine fossil record, stemming largely from our limited knowledge of the anatomical features with which the tail is associated. Here, we compare the morphology of the sacrum, the sole bony link between the tail and the rest of the body, among extant tailless hominoids and a broad sample of extant cercopithecoids known to vary in tail length (i.e., ‘very short’, ‘short’, and ‘long’) in order to identify morphological correlates of tail length. We examine three features of the sacrum, including the shape of the sacrum’s caudal articular surface (CAS), the sacrocaudal articulation (SCA) angle, and the lateral expansion of the last sacral vertebra’s transverse processes. Compared with all other taxa, ‘long’-tailed cercopithecoids have significantly more circularly-shaped CASs, more acute SCA angles, and more laterally expanded transverse processes of the last sacral vertebra. Tailless hominoids have significantly more elliptically-shaped CASs and less laterally expanded transverse processes than all tailed cercopithecoids, but in the latter parameter, they only differ significantly from ‘long’-tailed cercopithecoids. Cercopithecoids with ‘short’ and ‘very short’ tails are intermediate between tailless hominoids and ‘long’-tailed cercopithecoids with respect to CAS shape and lateral expansion of the transverse processes. SCA angle distinguishes clearly among all three cercopithecoid tail length groups. The results of this study provide evidence for significant differences in sacral morphology among extant catarrhines known to differ in tail length, and have implications for making inferences about tail length and function in extinct catarrhines.     

Ecological correlates of seed size in the British flora

1. The association between seed size and habitat shade within the British flora was investigated using a data set of seed masses, life histories and quantitative measures of habitat shade for 504 species; the association between seed size and seed longevity was investigated using a data set of seed masses, life histories and seed longevities for 301 species.
2. The data were analysed using the method of phylogenetically independent contrasts (PICs) calculated using the software package CAIC (Comparative Analysis by Independent Contrasts).
3. Seed mass was found to be positively correlated with habitat shade and negatively correlated with seed longevity, after variation owing to life history had been accounted for.     

Ecological correlates of extra-group paternity in mammals

Extra-group paternity (EGP) can form an important part of the mating system in birds and mammals. However, our present understanding of its extent and ecology comes primarily from birds. Here, we use data from 26 species and phylogenetic comparative methods to explore interspecific variation in EGP in mammals and test prominent ecological hypotheses for this variation. We found extensive EGP (46% of species showed more than 20% EGP), indicating that EGP is likely to play an important role in the mating system and the dynamics of sexual selection in mammals. Variation in EGP was most closely correlated with the length of the mating season. As the length of the mating season increased, EGP declined, suggesting that it is increasingly difficult for males to monopolize their social mates when mating seasons are short and overlap among females in oestrus is likely to be high. EGP was secondarily correlated with the number of females in a breeding group, consistent with the idea that as female clustering increases, males are less able to monopolize individual females. Finally, EGP was not related to social mating system, suggesting that the opportunities for the extra-group fertilizations and the payoffs involved do not consistently vary with social mating system.     

Tooth size and arcadal length correlates in man

Intra-arcadal mesiodistal and buccolingual tooth size correlations were evaluated in a sample of 125 caucasoids with ideal occlusion. Dental dimensions were corrected for arcade mength (as a measure of jaw size) by a series of regression analyses of each mesiodistal dimension on the sum of the mesiodistal dimensions within each arcade. Regression coefficients of tooth dimension on arcade length were calculated to gain an insight into the dimensional sensitivity of individual teeth to arcade length variation. The data presented here suggest a strong association between arcadal length (jaw size) dependence, and the dimensional stability of individual teeth. When corrected for arcade length, a definite pattern of tooth size correlation emerges: postcanine maxillary and mandibular teeth are negatively correlated to the anterior teeth and are positively correlated to one another. The hypothesis is developed that anterior and postcanine teeth should be viewed as two separate and negatively size-correlated units, beyond the boundaries of the four morphological tooth classes. Recognition of this basic dichotomous size arrangement within each jaw allows for a reassessment of some of the problems associated with hominid dental evolution.     

Ecological correlates of anuran exercise physiology

Summary Studies of exercise physiology of anuran amphibians have led to the suggestion that there is a dichotomy between species that depend upon movement to escape from predators and species that utilize static defenses. This generalization has been based upon a limited taxonomic survey and it contrasts with morphological, ecological, and behavioral studies that have revealed diverse and complex interrelationships among these features of anuran biology. We tested the hypothesis of a dichotomy of physiological types among anurans by measuring aerobic and anaerobic metabolism during maximum exercise for 17 species representing seven families and a variety of ecological types and locomotor modes. All degrees of dependence upon aerobic and anaerobic power input were found among the 17 species and the variation did not follow phylogenetic divisions. No single, simple prediction of the predominant source of power utilized for activity by the anurans we studied is possible. Predator avoidance behavior was not significantly correlated with the metabolic pattern. Predatory mode (active versus passive searchers) and mode of locomotion (non-jumpers versus jumpers) were correlated with dependence upon aerobic energy production and with each other. Reproductive behavior is probably another associated factor. The diversity of modes of power input among anurans is great and is intimately linked with numerous features of a species' biology. Single-factor explanations of this physiological characteristic are not appropriate.     

Ecological correlates of infraorbital foramen area in primates

The infraorbital foramen (IOF) transmits the infraorbital nerve (ION) to specialized sensory cells (mechanoreceptors) in the maxillary region. The size of the IOF has been used in numerous paleoecological interpretations of the fossil record. However, these interpretations have been applied without an explicit analysis of the relationship between ecological variables and the IOF. ION and IOF cross‐sectional area show a strong positive correlation. As a result, IOF area can be a proxy for ION area, and it is hypothesized that IOF area may be a good measure for maxillary somatosensory acuity. Differences in diet, substrate preference, and/or activity pattern have been shown to correlate with differences in maxillary somatosensory acuity among mammals. This study examines how IOF area covaries with different ecological variables. IOF area was measured for 89 primate species. Ecological profiles were also created for each species and used to evaluate interspecific variation in relative IOF area within each ecological category. The results show a significant relationship between relative IOF area and diet, but not substrate preference or activity pattern. Frugivores have significantly larger relative IOFs than either folivores or insectivores, but the relative IOFs of folivores and insectivores do not differ significantly from one another. These results partially support the hypothesis that maxillary mechanoreception is a critical sensory cue for primates within a feeding context. Results for this study suggest the IOF can be used as an informative character in some paleoecological interpretations of the primate fossil record. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Ecological correlates of feather mite prevalence in passerines

The relationship between host ecology and feather mite prevalence was analysed in birds. Feather mites are small arthropods (fam. Pterolichoidea and Analgoidea) commonly found on birds, although the nature of their interactions with the host (commensalism, mutualism or parasitism), still remains unclear. Host body mass and migratory behaviour were unrelated to feather mite prevalence. Contrary to expectation, there was no differences in mite prevalence between colonial and solitary-breeding species. However, winter sociality was associated with increased prevalence, suggesting that winter and breeding sociality affected the distribution patterns of feather mites in different ways. Plumage dichromatism was negatively correlated with feather mite prevalence, a result that is opposite to that predicted by the Hamilton and Zuk hypothesis for the evolution of host secondary sexual characteristics in relation to parasitism.     

Ecological correlates of extinction risk in Chinese birds

China is one of the countries with the richest bird biodiversity in the world. Among the 1372 Chinese birds, 146 species are considered threatened and three species are regionally extinct according to the officially released China Biodiversity Red List in 2015. Here, we conducted the first extensive analysis to systematically investigate the patterns and processes of extinction and threat in Chinese birds. We addressed the following four questions. First, is extinction risk randomly distributed among avian families in Chinese birds? Second, which families contain more threatened species than would be expected by chance? Third, which species traits are important in determining the extinction risk in Chinese birds using a multivariate phylogenetic comparative approach? Finally, is the form of the relationship between traits additive or nonadditive (synergistic)? We found that the extinction risk of Chinese birds was not randomly distributed among taxonomic families. The families that contained significantly more threatened species than expected were the hornbills, cranes, pittas, pheasants and hawks and eagles. We obtained eleven species traits that are commonly hypothesized to influence extinction risk from the literature: body size, clutch size, trophic level, mobility, habitat specificity, geographical range size, nest type, nest site, flocking tendency, migrant status and hunting vulnerability. After phylogenetic correction, model selection based on Akaike's information criterion identified the synergistic interaction between body size and hunting vulnerability as the single best correlate of extinction risk in Chinese birds. Our results suggest that, in order to be effective, priority management efforts should be given both to certain extinction‐prone families, particularly the hornbills, pelicans, cranes, pittas, pheasants and hawks and eagles, and to bird species with large body size and high hunting vulnerability.     

Ecological correlates of species differences in the Lake Tanganyika crab radiation

The endemic crabs of Lake Tanganyika include a phenotypically diverse clade that exhibits recent divergence and low phylogenetic species resolution. There are indications that ecological niche segregation has played a prominent role in the divergence of this clade. We used habitat surveys, gut content analyses and stable isotope analyses to test the extent to which morphological species are ecologically different. Our data show some interspecific segregation in depth, substrate type and mean stable isotope signatures. At the same time, a considerable level of ecological niche overlap is evident among species of Platythelphusa that coexist in rocky littoral habitats. We consider these results in the framework of adaptive radiation theory, and we discuss general ramifications for the maintenance of species diversity in Lake Tanganyika.     

Ecological correlates and determinants in the geographical variation of deer morphology

Previous studies on patterns in ungulate size variations have emphasized the effect of a particular environmental factor such as Bergmann's rule and the island rule. However, although multiple environmental factors may influence the body size, these studies focused on a single factor, and various measurements that may be influenced by different environmental factors (at least partly) were used as indices of body size. In this study, we used several skull and limb measurements to examine size variations among island populations of sika deer (Cervus nippon) in southern Japan considering the effects of multiple environmental factors. We found that all measurements differed markedly between populations. We focused on the skull and limb condylobasal length (CBL) and metacarpal length because they had the most important variations among the populations and the largest sample sizes. The common environmental factors influencing CBL and metacarpal length were island area and precipitation. Since these environmental factors reflect the availability of food resources, the causal factor of body size variation may be food resources. Interpopulation variation in metacarpal length was greater than that of CBL, indicating that metacarpal length may be affected by additional factors besides the common factors shared with CBL. Specific environmental factors influencing relative (CBL adjusted) metacarpal length were precipitation and slope. A common direct cause of those environmental factors was discussed in relation to topography. Analyses of phenotypic variation using multiple measurements with multiple environmental factors are useful to gain insight into underlying causes and can lead to identification of a measurement-specific variation with a specific driving force.     

Mandibular shape correlates of tooth fracture in extant Carnivora: implications to inferring feeding behaviour of Pleistocene predators

Percentages of tooth fracture and mandible shape are robust predictors of feeding habits in Carnivora. If these parameters co‐vary above the species level, more robust palaeobiological inferences could be made on fossil species. A test of association is presented between mandible shape and tooth fracture in a subset of extant carnivorans together with large Pleistocene fossil predators from Rancho La Brea (Canis dirus, Panthera atrox, and Smilodon fatalis). Partial least square (PLS) and comparative methods are employed to validate co‐variation of these two parameters in extant carnivorans. Association between mandible shape and percentage of tooth fracture is strongly supported, even if both blocks of data exhibit a phylogenetic signal to a different degree. Dietary adaptations drive shape/fracture co‐variation in extant species, although no significant differences occur in the PLS scores between carnivores and bone/hard food consumers. The fossil species project into PLS morphospace as outliers. Their position suggests a unique feeding behaviour. The increase in the size of prey, together with consumption of skin and hair from carcasses in a cold environment, might have generated unusual tooth breakage patterns in large predators from Rancho La Brea. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 70–80.     

Ecological correlates of seed persistence in soil in the north-west European flora

1 Using the data in a recently published seed bank database for north-west Europe, we describe how a species' seed bank behaviour can be characterized by a single 'longevity index', and investigate how representative the information in the database is of the north-west European flora. We also test the hypotheses that seeds of short-lived species are more persistent than those of long-lived species, and long-lived seeds are characteristic of species living in disturbed habitats.
2 The data are not representative of the north-west European flora as a whole; they are a fair reflection of a research effort that has been largely directed towards grassland and arable weeds. Data for rare species, non-agricultural habitats in general and wetlands, rocky habitats and native woodland in particular, are scarce or absent.
3 Annuals and biennials almost always have more persistent seeds than related perennials, and this difference is most striking when, as in Anagallis arvensis and Aphanes arvensis , the short-lived species have moved well away from the 'core' habitat of the family. Confamilial monocarps and polycarps do not differ consistently in seed mass.
4 Gradients of habitat disturbance are accompanied by predictable changes in seed persistence, which are themselves often (but not always) accompanied by parallel shifts in seed size. These results suggest that increasing habitat disturbance (i.e. increasing density-independent mortality) always selects for increased seed persistence, confirming both theory and previous analyses. However, increased seed persistence is not always associated with reduced seed size. This is because persistence depends not only on seed size, but on other traits, many of them physiological. In many habitats the probability of seed burial is strongly linked to seed size and shape, but in arable habitats cultural practices have broken this link.     

Pathogenic polyglutamine expansion length correlates with polarity of the flanking sequences

Background

Polyglutamine (polyQ) repeat expansion within coding sequence of a soluble protein is responsible for eight autosomal-dominant genetic neurodegenerative disorders. These disorders affect cerebellum, striatum, basal ganglia and other brain regions. The pathogenic polyQ-expansion threshold in these proteins varies from 32Q to 54Q. Understanding the reasons for variability in pathogenic polyQ threshold may provide insights into pathogenic mechanisms responsible for development of these disorders.

Findings

Here we established a quantitative correlation between the polarity of the flanking sequences and pathogenic polyQ-expansion threshold in this protein family. We introduced an “edge polarity index” (^EPI) to quantify polarity effects of the flanking regions and established a strong correlation between ^EPI index and critical polyQ expansion length in this protein family. Based on this analysis we subdivided polyQ-expanded proteins into 2 groups – with strong and weak dependence of polyQ threshold on ^EPI index. The main difference between members of the first and the second group is a polarity profile of these proteins outside of polyQ and flanking regions. PolyQ proteins are known substrates for proteasome and most likely mechanistic explanation for the observed correlation is that proteasome may have an impaired ability to process continuous non-polar regions of proteins.

Conclusions

The proposed hypothesis provides a quantitative explanation for variability in pathogenic threshold among polyQ-expansion disorders, which we established to correlate with polarity of flanking regions. To explain these results we propose that proteasome is not efficient in processing continuous non-polar regions of proteins, resulting in release of undigested and partially digested fragments. If supported experimentally, our hypothesis may have wide implications for further understanding the pathogensis of polyglutamine expansion disorders.