The lace web spiders (Araneae,Phyxelididae) of Madagascar: phylogeny,biogeography and taxonomy

We briefly review the potential history of Madagascar as either a Darwinian or a Wallacean island, summarize the phylogenetic evidence regarding the biogeography of Madagascar spiders, examine the dispersal history of the Madagascar Phyxelididae, and monograph the family in Madagascar. Molecular phylogenetic analyses for 32 Malagasy phyxelidid exemplars, nine confamilial outgroup taxa, and seven other more distant outgroups are performed for three nuclear markers and one mitochondrial genetic marker (28S, 18S, H3 and COI) utilizing Bayesian, maximum‐likelihood and parsimony methods. These analyses suggest that there are 14 species of Phyxelididae that may be recognized from Madagascar, that these may be divided into three genera, and that the Malagasy phyxelidids form a monophyletic group, probably resulting from a single invasion of the island by an ancestor from Africa. Two new genera, ten new species, and two new combinations are proposed: Manampoka atsimo gen. nov., sp. nov. ; Rahavavy gen. nov. , including R. ida sp. nov. and R. fanivelona (Griswold, 1990) comb. nov. and R. malagasyana (Griswold, 1990) comb. nov. ; and Ambohima andrefana sp. nov. , A. antsinanana sp. nov. , A. avaratra sp. nov. , A. maizina sp. nov. , A. ranohira sp. nov. , A. vato sp. nov. , A. zandry sp. nov. and A. zoky sp. nov. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 728–810.     

Genomic specification and epigenetic regulation of eukaryotic DNA replication origins

Identification of DNA replication origins (ORIs) at a genome-wide level in eukaryotes has proved to be difficult due to the high degree of degeneracy of their sequences. Recent structural and functional approaches, however, have circumvented this limitation and have provided reliable predictions of their genomic distribution in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, and they have also significantly increased the number of characterized ORIs in animals. This article reviews recent evidence on how ORIs are specified and maintained in these systems and on their regulation and sensitivity to epigenetic signals. It also discusses the possible additional involvement of ORIs in processes other than DNA replication.     

Evolution and adaptations of Galapagos sea-birds

With two endemic genera, 26% endemism at the specific, and 58% endemism at the subspecific level, the Galapagos sea-bird fauna is more highly endemic than that of any other archipelago. Of the four most distinct, hence probably oldest, endemics, three are probably of north Pacific origin and the fourth may be. The next most distinct group is of Humboldt Current origin, and the remainder, which are very little differentiated, are of Pacific or Caribbean origin. Special adaptations to Galapagos conditions include the loss of flight by a cormorant and the evolution of nocturnal habits by a gull, the latter probably as a result of kleptoparasitism or nest-predation by frigatebirds. As a group the Galapagos sea-birds show varied adaptive responses to the relatively ascasonal and highly unpredictable marine environment. Opportunistic and non-annual breeding regimes predominate. Unlike the Galapagos land-birds, the study of Galapagos sea-birds has thrown light not on speciation processes but on the consequences of natural selection acting on breeding ecology and associated behaviour.     

Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic Canarina canariensis (Campanulaceae)

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within‐island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo‐islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra‐island levels of genetic diversity larger than those between‐islands. We argue that volcanic eruptions and landslides after the merging of the palaeo‐islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo‐islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.     

Below-ground carbon and nitrogen accumulation in perennial grasses: A comparison of caespitose and rhizomatous growth forms

An experiment was conducted to compare below-ground soil organic carbon and total nitrogen accumulation between caespitose and rhizomatous perennial grasses in long-term (<25 yrs) grazed and ungrazed sites in semi-arid and mesic communities in the North American Great Plains. Development of greater nutrient pools beneath than between clones occurred at minimal clone basal areas (<60 cm²) for both caespitose species. Caespitose grasses accumulated substantially greater pools of carbon (20–200 fold) and nitrogen (50–500 fold) in soils to a depth of 10 cm beneath clones than rhizomatous grasses accumulated in rhizomes in both communities. Carbon and nitrogen pools in soils beneath caespitose clones exceeded combined (soil + rhizome) pools for rhizomatous grasses for a majority of the clone basal areas (>90 cm²) in the mesic community. In contrast, both pool sizes were smaller beneath the caespitose grass at all clone basal areas than the combined pools for the rhizomatous grass in the semi-arid community. The occurrence of larger soil nutrient pools beneath the rhizomatous species in the semi-arid community was largely a consequence of niche separation for microsites characterized by soils with higher nutrient concentrations, rather than plant-induced increases in nutrient concentrations. Although nutrient islands do not occur beneath rhizomatous grasses, their distribution in the semi-arid community was restricted to microsites characterized by soils with higher SOC and N concentrations. A greater efficiency of nutrient accumulation per unit rhizome mass and the maintenance of rhizome nutrient pools of similar magnitude to those of the rhizomatous grass in the mesic community may also contribute to the distribution of rhizomatous grasses in semi-arid communities. The existence of nutrient islands beneath a wide range of clone sizes in both mesic and semi-arid communities provides circumstantial evidence to suggest that nutrient islands beneath caespitose grasses may contribute to clone fitness in this growth form.     

Prediction of pathogenicity islands in Enterohemorrhagic Escherichia coli O157:H7 using genomic barcodes

The genome of lethal animal pathogenic bacterium Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is characterized by the presence of multiple pathogenicity islands (PAIs). Computational methods have been developed to identify PAIs based on the distinguishing G + C levels in some PAI versus non-PAI regions. We observed that PAIs can have a very similar G + C level to that of the host chromosome, which may have led to false negative predictions using these methods. We have applied a novel method of genomic barcodes to identify PAIs. Using this technique, we have successfully identified both known and novel PAIs in the genomes of three strains of EHEC O157:H7.     

The age and origin of the Pacific islands: a geological overview

The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were initially one plate, produced to the east of the original spreading centre before becoming split into three. The islands of the Pacific have originated as: linear chains of volcanic islands on the above plates either by mantle plume or propagating fracture origin, atolls, uplifted coralline reefs, fragments of continental crust, obducted portions of adjoining lithospheric plates and islands resulting from subduction along convergent plate margins. Out of the 11 linear volcanic chains identified, each is briefly described and its history summarized. The geology of 10 exemplar archipelagos (Japan, Izu-Bonin, Palau, Solomons, Fiji, New Caledonia, New Zealand, Society, Galápagos and Hawaii) is then discussed in detail.     

Dynamic analysis of a genomic island in Magnetospirillum sp. strain AMB-1 reveals how magnetosome synthesis developed

The entire structure of a 98 kb genomic region that abounds in genes related to magnetosome synthesis was first described in the Magnetospirillum sp. strain AMB-1. The deletion of this 98 kb genomic region and the circular form after excision from the chromosome was detected by PCR amplification. This strongly suggests that the region has undergone a lateral gene transfer. The region has the characteristics of a genomic island: low GC content, location between two repetitive sequences, and the presence of an integrase in the flanking region of the first repetitive sequence. This 98 kb genomic region has the potential for transfer by the integrase activity. Comparative genome analysis revealed other regions with a high concentration of orthologs in magnetic bacteria besides the 98 kb region, and magnetosome synthesis seemed to need not only the exogenous 98 kb region, but also other orthologs and individually originating genes.     

Island population,land area,and climate: A case study of the Marshall Islands

A major difficulty in the study of the relationship between human population size and the environment has been placing the problem in a testable framework. Using data from the Marshall Islands, this article tests the proposition that population size and density are highly correlated with environmental variables, including rainfall and land area, through a complex series of socially mediated regulatory mechanisms. This analysis thus supports the population-resources disequilibrium theory of culture change.Deceased.     

When North and South don’t mix: genetic connectivity of a recently endangered oceanic cycad,Cycas micronesica,in Guam using EST‐microsatellites

Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST‐microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self‐recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam’s genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed‐bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST‐locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species’ vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general.     

Family values

Evolutionary Genetics (2nd edn) by J. Maynard Smith, Oxford University Press, 1998. £50.00 hbk, £19.95 pbk (368 pages) ISBN 0 19 850232 X/0 19 850231 1Selection in Natural Populations by J.B. Mitton, Oxford University Press, 1998. £50.00 hbk (252 pages) ISBN 0 19 506352 XProgress and Prospects in Evolutionary Biology edited by J.R. Powell, Oxford University Press, 1997. £49.50 hbk (576 pages) ISBN 0 19 507691 5Evolution on Islands edited by P.R. Grant, Oxford University Press, 1997. £24.99 pbk (348 pages) ISBN 0 19 850 1714     

Islands and evolution: theory and opinion in Darwin's earlier years

Islands were not of special interest to evolutionists before Darwin. It was he who first appreciated their importance for demonstrating evolution in miniature. They were not of special interest because: (a) their peculiar products seemed no more peculiar than those of continents; (b) there was no special category of oceanic islands, but a continuum from such groups as the Canaries, Madeiras and Galápagos through New Zealand and Madagascar to Australia, Britain, and true continents; and (c) the concept of adaptive radiation, if known at all, was applied only to the higher levels of classification, and then very feebly.
When Darwin was young, classification at the lower levels hardly recognized convergence, and at the higher levels was subject to great changes, while only slowly separating out the major groups. In consequence, many of the facts of geographical distribution were misinterpreted, and numerous theories of the origination of species, groups, and biogeographical provinces were still plausible. It was largely the need for a historical, not ecological, explanation of the distribution of some mammals and plants, plus what he saw for himself in the Galápagos Islands, that convinced Darwin that evolution had occurred. His was a remarkable achievement in recognizing through all this 'noise' the meaning of adaptive radiation.     

Bacterial Genomic Islands: Organization,Function, and Evolutionary Role

Data on the structural organization and evolutionary role of specific bacterial DNA regions known as genomic islands are reviewed. Emphasis is placed on the most extensively studied genomic islands, pathogenicity islands (PAIs), which are present in the chromosome of Gram-negative and Gram-positive pathogenic bacteria and absent from related nonpathogenic strains. PAIs are long DNA regions that harbor virulence genes and often differ in GC content from the remainder of the bacterial genome. Many PAI occur in the tRNA gene loci, which provide a convenient target for foreign gene insertion. Some PAI are highly homologous to each other and contain sequences similar to ISs, phage att sites, and plasmid ori sites, along with functional or defective integrase and transposase genes, suggesting horizontal transfer of PAI among bacteria.     

The wild goats Capra aegagrus Erxleben, 1777 of the Mediterranean Sea and the Eastern Atlantic Ocean islands

• 1 Populations of wild goats that can be referred to as phenotypes of the pasang, or Bezoar goat, or wild goat Capra aegagrus Erxleben, 1777, still occur on several of the Mediterranean and Eastern Atlantic islands. Other populations became extinct not many decades ago.
• 2 Fossil evidence for the natural spread of the wild goat to any of these islands has not been found. Originating in the Near East, the region of its natural range and its earliest domestication, the species was introduced by humans onto the Mediterranean islands starting as early as the Pre‐Pottery Neolithic.
• 3 The islands of the Eastern Atlantic were colonized artificially by animals of ‘pre‐Hispanic’ origin. The principal phenotypes expressed by all these populations of goats can be matched with the characteristics of both C. a. aegagrus Erxleben, 1777 (aegagrus phenotype) and C. a. dorcas Reichenow, 1888 (dorcas phenotype).
• 4 Most of these animals currently survive on the islands without being fed by humans, and should be protected.

     

庙岛群岛北五岛景观格局特征及其生态效应

海岛由于自然特征的空间差异、人类活动的日益增强以及生态系统的脆弱性,其景观格局空间分异性明显且生态效应趋于复杂。以庙岛群岛北五岛为研究区,基于现场调查和3S技术,从景观尺度、海岛尺度和区块尺度分析海岛景观格局空间特征,进而探讨景观格局与净初级生产力(NPP)、植物多样性和土壤性质的关系。结果显示:(1)不同尺度景观格局均表现出了空间差异。景观尺度上,针叶林、阔叶林和草地3类植被景观面积最大,斑块密度、边缘密度和平均形状指数总体较高,建筑用地也具有较大规模,其斑块密度较高,平均形状指数处于最低值,裸地也具有一定规模,其各项景观指标处于中间位置;海岛尺度上,随着海岛面积、人口和GDP的增加,斑块密度和人为干扰指数均明显增大;区块尺度上,斑块密度、边缘密度和平均形状指数与海拔呈显著正相关,人为干扰指数与海拔和坡度均呈显著负相关。海岛面积、地形和人类活动分别是北五岛景观格局的基本因子、重要限制因子和直接驱动因子。(2)海岛景观格局的生态效应与尺度密切相关。景观尺度上,各项生态效应指标在不同景观类型上均具有显著差异,海岛尺度上的生态效应指标对景观格局的响应不甚灵敏;区块尺度上,生态效应指标与景观格局指数表现出了显著的简单相关性和偏相关性,但二者结果具有差异。NPP和土壤水分主要受到景观类型和植被生长状况的影响,多样性和土壤养分同时受到景观类型和景观格局破碎度、边缘效应的影响,人为活动强度的增大地带来了各项生态效应指标的降低。控制建设规模、优化景观布局与改进开发利用方式是维系海岛生态系统稳定性的重要措施。     

The extent of extinctions of mammals on islands

Many of the world's oceanic and oceanic-like islands possessed endemic mammal faunas before they were colonized by humans. These faunas, unbalanced and impoverished compared to continental faunas, usually lacked large mammalian carnivores. In virtually all cases, the arrival of humans and their domesticants and commensals on these islands is related to the extirpation of large numbers of endemic insular mammals. These extinction events affected at least 27% of autochthonous mammal species on the world's oceanic and oceanic-like islands. This percentage rises the 35% when volant mammals are excluded. This reduction in the natural biodiversity brought about the disappearance of several unique biological types that apparently never existed on the continents.     

The evolution and ontogeny of the dentition of Myotragus balearicus Bate, 1909 (Artiodactyla, Caprinae): evidence from new fossil data

Myotragus balearicus Bate 1909 is an artiodactyl Caprinae endemic to the Balearic Islands (Spain), which became extinct more than 4000 years ago. It is characterized by a series of very unusual apomorphies acquired throughout its insular evolution, one of which is the presence of a single evergrowing incisor (with an open root) in each dentary. This incisor has been classically considered as I₁. The study of recendy discovered fossils of this species, which have been collected from the excavation of Holocene cave sediments in Cova Estreta (Pollenca, Mallorca) and in Cova des Moro (Manacor, Mallorca), together with the reexamination of materials belonging both to this species and to its ancestors, allowed us to study the ontogeny and evolution of the Myotragus dentition. The replacement of premolars differs only slighdy from the pattern recorded in ofiier bovids. Nevertheless, there are significant differences with other bovids regarding the incisiform series. Myotragus balearicus lacks secondary incisors. Through a neotenic process, which started during the Upper Pliocene, M. balearicus acquired a monophyodontic incisiform dentition, reducing the number of incisiforms to only one, identified as dl₂. The richness of the finds allows us to describe the different steps in this evolution. The only incisiform that appears to have been lost is dl_;l. The identification of the evergrowing incisor of M. balearicus as dl₂ reinforces its convergence with rodents postulated by Bate and there is discussion regarding homologies of incisors of rodents and lagomorphs.     

Shifts in litterfall and dominant nitrogen sources after expansion of shrub thickets

Woody encroachment into herbaceous ecosystems is emerging as an important ecological response to global change. A primary concern is alterations in C and N cycling and associated variations across a variety of ecosystems. We quantified seasonal variation in litterfall and litter N concentration in Morella cerifera shrub thickets to assess changes in litterfall and associated N input after shrub expansion on an Atlantic coast barrier island. We also used the natural abundance of ¹⁵N to estimate the proportion of litterfall N originating from symbiotic N fixation. Litterfall for shrub thickets ranged from 8,991 ± 247 to 3,810 ± 399 kg ha⁻¹ year⁻¹ and generally declined with increasing thicket age. Litterfall in three of the four thickets exceeded previous estimates of aboveground annual net primary production in adjacent grasslands by 300–400%. Leaf N concentration was also higher after shrub expansion and, coupled with low N resorption efficiency and high litterfall, resulted in a return of as much as 169 kg N ha⁻¹ year⁻¹ to the soil. We estimated that ∼70% of N returned to the soil was from symbiotic N fixation resulting in an ecosystem input of between 37 and 118 kg ha⁻¹ year⁻¹ of atmospheric N depending on site. Considering the extensive cover of shrub thickets on Virginia barrier islands, N fixation by shrubs is likely the largest single source of N to the system. The shift from grassland to shrub thicket on barrier islands results in a substantial increase in litterfall and foliar N concentration that will likely have a major impact on the size and cycling of ecosystem C and N pools. Increasing C and N availability in these nutrient-poor soils is likely to permanently reduce cover of native grasses and alter community structure by favoring species with greater N requirements.     

Legal Issues Related to Sovereignty over Dokdo and Its Maritime Boundary

This article examines the historical events relevant to the claims of sovereignty by Japan and Korea over Dokdo, the legal doctrines that have been applied by international tribunals to other disputes over remote and uninhabited territories, and the principles governing maritime boundary delimitation that are relevant to the ocean space around Dokdo. The applicable decisions of the International Court of Justice and other tribunals are examined in detail. Among the topics addressed are the methods of acquiring sovereignty over territory, the relevance of contiguity to such claims, the requirements of effective protests, and the activities and omissions that constitute acquiescence. Attention is also given to the status of this matter as a “dispute” and how closure might be brought to it.