Scaling of species diversity and body mass in mammals: Cope’s rule and the evolutionary cost of large size

Abstract

Equations are constructed describing the inverse correlation of species diversity and body mass in extant and Cenozoic mammals. Cope’s rule, the tendency for many mammal clades to increase in body size through time, through phyletic change in single lineages or turnover within species groups, is interpreted as a probability function reducing diversity potential as a tradeoff for ecological/evolutionary gains. The inverse rule predicts that large species in clades will be less diverse than smaller species and, unless origination rates remain high among smaller clade members, clades conforming to Cope’s rule will decline in diversity, moving towards extinction. This proposition is evaluated in the Cenozoic histories of five North American mammal clades; cotton rats, felids, canids, hyaenodontids, and equids. Diversity potential of different size classes within the 3.75 million year phyletic history of the muskrat, Ondatra zibethicus, is also examined. A corollary prediction of the inverse rule, that large species should have longer durations (species lifespans) than small species, is unresolved. Successful clades maintain small size or a significant number of smaller species relative to clade average size. The potential loss of unique extant large mammal species justifies the conservation effort to protect them. The similarity of scaling exponents of species diversity to mass around a slope of -1.0 suggests that species diversity is correlated with home range size, the latter related to the probability of population fragmentation.     

Long-term Perspectives on Lagged Ecosystem Responses to Climate Change: Permafrost in Boreal Peatlands and the Grassland/Woodland Boundary

Changes in climate could have far-reaching consequences for ecosystems sensitive to changes in temperature and precipitation, such as boreal permafrost peatlands and grassland/woodland boundaries. The long-term data from our studies in these ecosystems suggest that transient responses of permafrost and vegetation to climate change may be difficult to predict due to lags and positive feedbacks related to vegetation and disturbance. Boreal permafrost peatlands comprise an ecosystem with strong local controls on microclimate that influence the formation and thaw of permafrost. These local controls may preserve permafrost during the transient stages of climate warming, producing lagged responses. The prairie–forest border region of the northern Great Plains has experienced frequent change and has complex dynamics involving transitions in the grassland composition of prairie and in the degree of woodiness in bordering forests. Fire frequency interacts with fuel loading and tree recruitment in ways that affect the timing and direction of change. Lags and thresholds could lead to sudden large responses to future climate change that are not readily apparent from current vegetation. The creation of adequate models to characterize transient ecosystem changes will require an understanding of the linkages among processes operating at the scale of 10s of meters and over long time periods. Received 14 December 1999; accepted 7 July 2000.     

大兴安岭地区森林雷击火与闪电的关系

林火是森林生态系统的重要影响因子.随着全球气候变暖,林火,特别是雷击火有增多的趋势.本文对我国东北大兴安岭地区1966-2007年的林火数据及相应的闪电和气象资料进行分析.结果表明:1966-2007年,该地区雷击火的次数及其过火面积都呈显著增加趋势.影响雷击火的气象条件与研究时间尺度有关,年尺度的雷击火与降水显著相关,相关系数达-0.489;月尺度的雷击火则与气温显著相关,相关系数为0.18.雷击火与闪电的关系也与时间尺度有关,年尺度的雷击火与闪电关系不明显,受降水影响较大;月尺度的雷击火与闪电具有较好的相关性,且受降水的影响;日尺度的雷击火在降水量＞5 mm时与闪电关系不明显,但当降水量＜5 mm时,雷击火与闪电次数呈正相关.据此,发展了基于闪电定位仪数据的火险指数算法以及大兴安岭地区的森林雷击火预报模型.经2005-2007年雷击火验证,该模型的预报准确率＞80％.     

Diverse Brain Myeloid Expression Profiles Reveal Distinct Microglial Activation States and Aspects of Alzheimer’s Disease Not Evident in Mouse Models

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6,6’-Dihydroxythiobinupharidine as a poison of human type II topoisomerases

A number of natural products with medicinal properties increase DNA cleavage mediated by type II topoisomerases. In an effort to identify additional natural compounds that affect the activity of human type II topoisomerases, a blind screen of a library of 341 Mediterranean plant extracts was conducted. Extracts from Nuphar lutea, the yellow water lily, were identified in this screen. N. lutea has been used in traditional medicine by a variety of indigenous populations. The active compound in N. lutea, 6,6’-dihydroxythiobinupharidine, was found to enhance DNA cleavage mediated by human topoisomerase IIα and IIβ ∼8-fold and ∼3-fold, respectively. Mechanistic studies with topoisomerase IIα indicate that 6,6’-dihydroxythiobinupharidine is a “covalent poison” that acts by adducting the enzyme outside of the DNA cleavage-ligation active site and requires the N-terminal domain of the protein for its activity. Results suggest that some of the medicinal properties of N. lutea may result from the interactions between 6,6’-dihydroxythiobinupharidine and the human type II enzymes.     

Inner structural organization of the mandibular corpus in the late Early Pleistocene human specimens Tighenif 1 and Tighenif 2

The present study investigates the inner structural organization of the two mandible specimens Tighenif 1 and Tighenif 2 from the late early Pleistocene site of Tighenif, Algeria. Using (micro)tomographic scans, we built a new protocol to investigate the cortical bone topography at the post-canine level. We selected two cross-sectional slices placed between the P3/P4 and M1/M2 on the right and left sides and assessed the cortical bone thickness topography (CBT) on each slice. Our analyses demonstrate that the mandibles from Tighenif exhibit higher CBT and a different topographic distribution pattern at the molar level than in modern humans, resulting in a proportionally more robust inner structure, while a similar signal is observed between the fossil and extant specimens at the premolar level. Further studies need to be done in order to determine if this feature is related to functional constraints during mastication or paramasticatory activities; or if it is related to any independent evolutionary process.     

太白山针叶林的Fuzzy分类研究

应用模糊聚类分析法和模糊图论分析对太白山针叶林进行了数量分类比较研究。将２６个样地分为两大类共７个群落类型。研究结果表明,两种方法在植物群落分类研究中,不但是可行的,而且所分类的实际结果是等价的,与实际观测情况也是吻合的。其中的图论法直接依据模糊相似系数得到树状图,简便易行,显示出更大的适用性。     

Phylogeny of the Procyonidae (Mammalia: Carnivora): molecules, morphology and the Great American Interchange

The Procyonidae (Mammalia: Carnivora) have played a central role in resolving the controversial systematics of the giant and red pandas, but phylogenetic relationships of species within the family itself have received much less attention. Cladistic analyses of morphological characters conducted during the last two decades have resulted in topologies that group ecologically and morphologically similar taxa together. Specifically, the highly arboreal and frugivorous kinkajou (Potos flavus) and olingos (Bassaricyon) define one clade, whereas the more terrestrial and omnivorous coatis (Nasua), raccoons (Procyon), and ringtails (Bassariscus) define another clade, with the similar-sized Nasua and Procyon joined as sister taxa in this latter group. These relationships, however, have not been tested with molecular sequence data. We examined procyonid phylogenetics based on combined data from nine nuclear and two mitochondrial gene segments totaling 6534bp. We were able to fully resolve relationships within the family with strongly supported and congruent results from maximum parsimony, maximum likelihood, minimum evolution, and Bayesian analyses. We identified three distinct lineages within the family: a (Nasua, Bassaricyon) clade, a (Bassariscus, Procyon) clade, and a Potos lineage, the last of which is sister to the other two clades. These findings, which are in strong disagreement with prior fossil and morphology-based assessments of procyonid relationships, reemphasize the morphological and ecological flexibility of these taxa. In particular, morphological similarities between unrelated genera possibly reflect convergence associated with similar lifestyles and diets rather than ancestry. Furthermore, incongruence between the molecular supermatrix and a morphological character matrix comprised mostly of dental characters [Baskin, J.A., 2004. Bassariscus and Probassariscus (Mammalia, Carnivora, Procyonidae) from the early Barstovian (Middle Miocene). J. Vert. Paleo. 24, 709-720] may be due to non-independence among atomized dental characters that does not take into account the high developmental genetic correlation of these characters. Finally, molecular divergence dating analyses using a relaxed molecular clock approach suggest that intergeneric and intrageneric splits in the Procyonidae mostly occurred in the Miocene. The inferred divergence times for intrageneric splits for several genera whose ranges are bisected by the Panamanian Isthmus is significant because they suggest diversification well precedes the Great American Interchange, which has long been considered a primary underlying mechanism for procyonid evolution.     

Synthesis,molecular docking,acetylcholinesterase and butyrylcholinesterase inhibitory potential of thiazole analogs as new inhibitors for Alzheimer disease

A series of thirty (30) thiazole analogs were prepared, characterized by ¹H NMR, ¹³C NMR and EI-MS and evaluated for Acetylcholinesterase and butyrylcholinesterase inhibitory potential. All analogs exhibited varied butyrylcholinesterase inhibitory activity with IC₅₀ value ranging between 1.59 ± 0.01 and 389.25 ± 1.75 μM when compared with the standard eserine (IC₅₀, 0.85 ± 0.0001 μM). Analogs 15, 7, 12, 9, 14, 1, 30 with IC₅₀ values 1.59 ± 0.01, 1.77 ± 0.01, 6.21 ± 0.01, 7.56 ± 0.01, 8.46 ± 0.01, 14.81 ± 0.32 and 16.54 ± 0.21 μM respectively showed excellent inhibitory potential. Seven analogs 15, 20, 19, 24, 28, 30 and 25 exhibited good acetylcholinesterase inhibitory potential with IC50 values 21.3 ± 0.50, 35.3 ± 0.64, 36.6 ± 0.70, 44.81 ± 0.81, 46.36 ± 0.84, 48.2 ± 0.06 and 48.72 ± 0.91 μM respectively. All other analogs also exhibited well to moderate enzyme inhibition. The binding mode of these compounds was confirmed through molecular docking.     

Thyreophoran vertebrae from the Callovian (Middle Jurassic) of the Vaches Noires cliffs (Normandy,France), with remarks on the dinosaur assemblage from the Vaches Noires

Two associated incomplete thyreophoran dorsal vertebrae from the Callovian Marnes de Dives Formation of the Vaches Noires cliffs, on the Normandy coast, are referred to an indeterminate stegosaur that appears to be different from Lexovisaurus, previously reported from the Callovian of western France. These vertebrae are the first evidence of thyreophorans from the Vaches Noires and complement the dinosaur assemblage from this locality, which hitherto consisted of several theropod taxa and an indeterminate sauropod. The dinosaur record from the Vaches Noires is heavily dominated by theropods and this imbalance is difficult to explain. A possible explanation may be that the dinosaur sample from the Vaches Noires is too small to be statistically significant and representative of the original faunal assemblage from which it is derived.