Animal community structure as a function of stream size

The species-area relationship of the island biogeography theory was calculated for macroinvertebrates in 22 coastal, adjacent streams. A z-value of 0.19 was obtained. The low z-value was probably a consequence of the short distances between streams as well as high dispersal rates. In addition, a cluster analysis based on the dissimilarity of species assemblages showed that stream size was of prime importance in categorizing the streams. To a smaller extent water quality affected the community structure in the streams.     

Remarkable new evidence for island radiation in birds

If island biogeography has a sweet spot, it's where islands generate their own species diversity rather than merely taking on mainland immigrants. In birds and other highly dispersive taxa, however, this 'zone of radiation', may be vanishingly small. Darwin's finches and Hawaiian Honeycreepers are among only a handful of examples of island radiation in birds (Price 2008), suggesting that winged powers of dispersal make sufficient isolation from mainland colonists unlikely, while also hindering speciation within and among isolated islands. Nevertheless, two studies in this issue of Molecular Ecology join a string of other recent analyses suggesting that island radiation in birds remains under-appreciated (see also Moyle et al. 2009; Kisel & Barraclough 2010; Rosindell & Phillimore 2011). Melo et al. (2011) use a phylogenetic analysis of white-eyes on islands in the Gulf of Guinea to identify two previously overlooked island radiations, and reveal replicated adaptive divergence on islands where species occur in pairs. Sly et al. (2011), meanwhile, consider possible explanations for speciation and geographic differentiation within a large island, and find the same type of oceanic barriers that are critical to bird speciation across archipelagos may also contribute to divergence that appears to have occurred within a single island.     

Determinants of alpha and beta vascular plant diversity in Mediterranean island systems: the Ionian islands,Greece

The Ionian archipelago is the second largest Greek archipelago after the Aegean, but the factors driving plant species diversity in the Ionian islands are still barely known. We used stepwise multiple regressions to investigate the factors affecting plant species diversity in 17 Ionian islands. Generalized dissimilarity modelling was applied to examine variation in the magnitude and rate of species turnover along environmental gradients, as well as to assess the relative importance of geographical and climatic factors in explaining species turnover. The values of the residuals from the ISAR log₁₀‐transfomed models of native and endemic taxa were used as a measure of island floristic diversity. Area was confirmed to be the most powerful single explanatory predictor of all diversity metrics. Mean annual precipitation and temperature, as well as shortest distance to the nearest island are also significant predictors of vascular plant diversity. The island of Kalamos constitutes an important plant diversity hotspot in the Ionian archipelago. The recent formation of the islands, the close proximity to the mainland source and the relatively low dispersal filtering of the Ionian archipelago has resulted in islands with a flora principally comprising common species and a low proportion of endemics. Small islands keep a key role in conservation of plant priority sites.     

On the semiotic dimension of ecological theory: The case of island biogeography

The Macarthur-Wilson equilibrium theory of island biogeography has had a contradictory role in ecology. As a lasting contribution, the theory has created a new way of viewing insular environments as dynamical systems. On the other hand, many of the applications of the theory have reduced to mere unimaginative curve-fitting. I analyze this paradox in semiotic terms: the theory was mainly equated with the simple species-area relationship which became a signifier of interesting island ecology. The theory is, however, better viewed as a theoretical framework that suggests specific hypotheses on the ecology of colonization of insular environments. This paradox is inherent in the use of simplifying analytic models. Analytic models are necessary and fruitful in the work of ecologists, but they ought to be supplemented with a broader, pluralistic appreciation of the role of theories in general.     

Birds and biogeography of Mount Mecula in Mozambique’s Niassa National Reserve

The montane forests of northern Mozambique’s isolated massifs are inhabited by numerous range-restricted and threatened bird species, but until recently were extremely little-known. We report on a first avifaunal survey of the isolated montane habitats of Mt Mecula (1 442 m), Niassa National Reserve, notable as the only currently protected montane area in northern Mozambique. Mount Mecula’s moist forest is small (approximately 136 ha in total) and patchy, and although known botanically to have some montane affinities, was found to support an avifauna more typical of riparian forests of medium to low altitude. The only montane forest species recorded was Lemon Dove Aplopelia larvata. Other montane elements included Vincent’s Bunting Emberiza (capensis) vincenti, one of six species recorded new to the Niassa National Reserve list. Overall, it appears that despite its intermediate location, Mt Mecula does not represent a biogeographical ‘stepping stone’ for montane forest bird species. This probably owes to its remoteness from the Eastern Arc Mountains of Tanzania to the north and the massifs of other parts of northern Mozambique, to the south and west.     

A unified model of island biogeography sheds light on the zone of radiation

Islands acquire species through immigration and speciation. Models of island biogeography should capture both processes; however quantitative island biogeography theory has either neglected speciation or treated it unrealistically. We introduce a model where the dominance of immigration on small and near islands gives way to an increasing role for speciation as island area and isolation increase. We examine the contribution of immigration and speciation to the avifauna of 35 archipelagoes and find, consistent with our model, that the zone of radiation comprises two regions: endemic species diverged from mainland sister-species at intermediate isolation and from insular sister-species at higher levels of isolation. Our model also predicts species-area curves in accord with existing research and makes new predictions about species ages and abundances. We argue that a paucity of data and theory on species abundances on isolated islands highlights the need for island biogeography to be reconnected with mainstream ecology.     

Biodiversity growth on the volcanic ocean islands and the roles of in situ cladogenesis and immigration: case with the reptiles

Models for biodiversity growth on the remote oceanic islands assume that in situ cladogenesis is a major contributor. To test this, we compiled occurrence data for 194 terrestrial reptile species on 53 volcanically‐constructed middle‐ to low‐latitude landmasses worldwide. Despite 273 native island‐species records, there are only 8–12 cases of the phenomenon, including just two radiations. Diversification frequencies are largely uncorrelated with island area, age, maximum altitude, and isolation. Furthermore, there is no indication that the presence of non‐sister congeners on an island stymies the process. Diversity on individual oceanic islands therefore results primarily from immigration and anageneis, but this is not a simple matter. Clusters that are difficult to reach (far or challenging to get to) or thrive upon (e.g. Canaries, Galápagos) have relatively few clades (3–8), some of which have many species (6–14), and all host at least one endemic genus. In these settings, diversity grows mainly by intra‐archipelago transfer followed by within‐island anagenetic speciation. In contrast, those island groups that are easier to disperse to (characterized by short distances and conducive transit conditions) and harbour more benign habitats (e.g. Comoros, Lesser Antilles) have been settled by many ancestor‐colonizers (≥ 14), but each clade has few derived species (≤ 4). These archipelagoes lack especially distinctive lineages. Models explaining the assembly and growth of terrestrial biotic suites on the volcanic ocean islands thus need to accommodate these new insights.     

温带次生林的岛屿化对鸟类物种多样性及密度的影响

由于自然事件的影响和人类活动的干扰,越来越多的大片森林破碎成彼此孤立、面积不一的森林岛屿,这种变化无疑会对某些动物的分布模式及行为特征产生影响。于2000和2001年的春夏季,在吉林省左家自然保护区及土门岭地区,采用点样法对18块森林岛屿(面积范围:4.3–76.9hm2)中的鸟类物种多样性及密度进行了调查。主要目的是检测森林岛屿的面积效应是否对鸟类物种多样性及密度产生影响,同时分析经典的岛屿生物地理理论是否可以解释破碎化后的森林岛屿面积与物种的关系。结果表明,鸟类物种多样性在年间没有显著变化,但鸟类的密度在不同年间变化较大。不同面积森林岛屿中的鸟类物种多样性有所差异,所包含的鸟类物种数从12种到43种不等。尽管有些面积较大的斑块所包含的物种数较少,但鸟类物种数的总体趋势是随着斑块面积的增大而增多。不同鸟类对森林岛屿面积的反应并不相同,灰椋鸟(Sturnuscineraceus)、红尾伯劳(Laniuscristatus)、灰头鹀(Embrizaspodocephala)等在面积较小的斑块中密度较大,而山鹡鸰(Dendronanthusindicus)、树鹨(Anthushodg-soni)、灰背鸫(Turdushortulorum)等几乎不分布于小面积斑块之中。森林岛屿中鸟类物种随着面积变化的变异方式符合经典的岛屿生物地理理论的基本模式,但Z值和C值差异较大     

Is a new paradigm emerging for oceanic island biogeography?

Following several decades during which two dissimilar and incompatible models (equilibrium and vicariance) dominated island biogeography, recent publications have documented patterns that point the way towards a new paradigm that includes elements of both models, as well as some novel aspects. Many of these seminal contributions have been made possible by the recent development of robust, temporally calibrated phylogenies used in concert with increasingly precise and reliable geological reconstructions of oceanic regions. Although a new general model of oceanic island biogeography has not yet been proposed, in this brief overview I present six hypotheses that summarize aspects of the emerging paradigm. These hypotheses deal with: the frequency of dispersal over oceanic water barriers by terrestrial organisms; the existence of substantial variation in the amount of dispersal (and gene flow) within a given set of related species within a given archipelago; the frequency, extent and impact on species richness of diversification within archipelagos; the frequent correlation of island age and the age of the species that live on the island; the long-term persistence of species on oceanic islands; and the occasional recolonization of continents by species from clades that diversified on islands. Identifying, testing, and seeking means of synthesizing these and other emerging hypotheses may allow a new conceptual paradigm to emerge.     

千岛湖岛屿特征与节肢动物多样性的关系

采用栅格采样法,于2006年4、5、8和10月对千岛湖库区50个不同大小岛屿中节肢动物的种类与数量进行了调查,分析了岛屿面积、海拔、形状和距离等因素对岛屿节肢动物物种丰富度的影响.结果表明:岛屿上节肢动物总物种丰富度、高扩散力物种丰富度和低扩散力物种丰富度均随岛屿面积的增大而增加,且岛屿面积与物种丰富度之间的关系符合经典岛屿生物地理学模型;节肢动物物种丰富度受岛屿面积、海拔和形状的综合影响,距离对岛屿上物种的丰富度没有显著影响;总的物种丰富度与岛屿形状指数和海拔呈显著正相关,岛屿面积和海拔与高扩散力物种的物种丰富度显著相关,而低扩散力物种与岛屿各地理因素之间的相关性均不显著.     

Haplotype diversity of the nematode Pristionchus pacificus on Réunion in the Indian Ocean suggests multiple independent invasions

Pristionchus pacificus has been established as a nematode model system in evolutionary developmental biology and evolutionary ecology. Field studies in North and South America, Asia, Africa and Europe indicated that nematodes of the genus Pristionchus live in association with scarab beetles. Here, we describe the first account of soil‐ and beetle‐associated nematodes on an island setting by investigating the island of Réunion in the Indian Ocean. Réunion has high numbers of endemic insects and is one among several attractive islands for biodiversity studies. Being of volcanic origin, Réunion is 2–3 million years old, making it the youngest of the Mascareigne islands. We show that beetle‐ and soil‐derived nematodes on Réunion are nearly exclusively hermaphroditic, suggesting that selfing is favoured over gonochorism (outcrossing) during island colonization. Among members of four nematode genera observed on Réunion, Pristionchus pacificus was the most prevalent species. A total of 76 isolates, in association with five different scarab beetles, has been obtained for this cosmopolitan nematode. A detailed mitochondrial haplotype analysis indicates that the Réunion isolates of P. pacificus cover all four worldwide clades of the species. This extraordinary haplotype diversity suggests multiple independent invasions, most likely in association with different scarab beetles. Together, we establish Réunion as a case study for nematode island biogeography, in which the analysis of nematode population genetics and population dynamics can provide insight into evolutionary and ecological processes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 170–179.     

Tropical fruitflies (Diptera: Tephritidae) of the Krakatau Archipelago in 1990 and comments on faunistic changes since 1982

Three of the Krakatau islands, in Sunda Strait, some 40 km from both Java and Sumatra, are believed to have been totally devastated by the famous cataclysmic eruption of 1883. The fourth, Anak Krakatau, is an emergent volcanic island which rose from Krakatau's submerged 1883 caldera in 1930, suffered a self-devastating eruption in 1952/3 and several severely damaging ones since then. In 1990 the tephritid fauna was monitored on all the islands with Steiner traps. Nine species were found, five of which appeared to have been found by Yukawa in 1982 (Yukawa 1984) using similar methods and lures, when he noted a total of six species. As in 1982, the fauna in 1990 was characterized by the numerical dominance ofBactrocera albistrigata (de Meijere) although this appeared to be less marked than in 1982 andBactrocera papayae Drew & Hancock appeared to have increased in relative numbers. The distribution of three species over the islands of the archipelago had increased and four species not found in 1982 were present. Rakata, Krakatau's remnant and by far the largest and highest island, carried seven species (six in 1982), Sertung three (two in 1982), Panjang four (one in 1982) and Anak Krakatau four (one in 1982). Capture rates were lower than in 1982 but still higher than those obtained on the Javan mainland in 1982. There was a marked difference between the tephritid faunas of Anak Krakatau's two forelands, which were at different stages of biotic succession.     

First upper molar and mandible shape of wood mice (Apodemus sylvaticus) from northern Germany: ageing, habitat and insularity

The patterns of shape variation of the first upper molar and mandible have been investigated within and among wood mice (Apodemus sylvaticus) populations from northern Germany. Some factors such as sex and age of the animals could be a source of within-group morphological variability interfering with among-groups patterns of differentiation. The relative importance of both sources of shape variation was investigated, in order to evaluate the robustness of patterns of fine-scale geographic differentiation. The increasing age of the animals, estimated by wear stages of the upper tooth row, caused significant variations in size and shape of the molars due to progressive abrasion of the cusps. It also involved shape changes of the mandible due to bone remodelling. However, these intrapopulational effects are of limited importance compared to geographic differentiation.Gene flow among populations should be favoured across mainland populations but lowered between mainland and islands, and to a lesser extent among close islands. Shape differences in molars are in agreement with this expected pattern of gene flow. Patterns of mandible differentiation rather match local variations in habitats. At this fine geographic scale, molar shape would vary according to the amount of genetic exchange among populations whereas mandible shape might be under local selective and/or functional constraints.

Zusammenfassung

Die Form von erstem oberen Molar und Unterkiefer der Waldmaus (Apodemus sylvaticus) in Norddeutschland: Alter, Habitat und InseleffektDie Formvariabilität des Molars (M1/) und des Unterkiefers von norddeutschen Waldmäusen (Apodemus sylvaticus) wurde untersucht. Dabei wurde sowohl die Variabilität zwischen verschiedenen Populationen als auch die Variabilität innerhalb einer Population studiert. So können Geschlecht und Alter beispielsweise die Formvariabilität innerhalb einer Population verursachen. Deshalb wurde die Bedeutung dieser Faktoren mit der Variabilität zwischen geographisch unterschiedlichen Populationen verglichen. Geschlechtsdimorphismus wurde nicht beobachtet. Ein zunehmendes Alter verursacht eine Variation der Größe und der Form des Molars infolge fortschreitender Abnutzung. Der Unterkiefer ändert sich auch durch spätes Wachstum und Umgestaltung des Knochens. Jedoch sind diese Effekte von beschränkter Bedeutung verglichen mit der Variabilität von Ort zu Ort.Der Genfluß zwischen Festland-Populationen sollte begünstigt sein verglichen mit dem Genfluß zwischen nordfriesischen Inseln und zwischen Inseln und Festland. Sylt nimmt dabei eine Zwischenstellung ein, weil diese Insel durch einen Damm mit dem Festland verbunden ist. Die Differenzierung des Molars stimmt mit diesem erwarteten Muster überein. Die Differenzierung der Form des Unterkiefers entspricht eher den unterschiedlichen Habitaten zwischen Holstein, Nordfriesland, und den nordfriesischen Inseln. Trotz des kleinen geographischen Rahmens dieser Untersuchung lassen sich folgende Ergebnisse ableiten: Die Molaren scheinen sich mit dem Genfluß zwischen verschiedenen Populationen zu ändern während sich der Unterkiefer durch selektive und/oder funktionelle Besonderheiten zu ändern scheint.     

岛屿生物地理学理论：模型与应用

前言岛屿有许多显著特征,如地理隔离,生物类群简单。这些特点为重复性研究和统计学分析奠定了基础,从而有利于许多深入而细致的生物学研究。因此,岛屿为发展和检验自然选择、物种形成及演化,以及生物地理学和生态学诸领域的理论和假设,提供了重要的自然实验室。岛屿生物地理学理论(MacArthurwilson学说)即为岛屿生物学研究中所产生的著名理论之一。该理论发展之     

Plant diversity in Oceanic archipelagos: realistic patterns emulated by an agent‐based computer simulation

Although islands as natural laboratories have held the attention of scientists for centuries, they continue to offer new study questions, especially in the context of the current biodiversity crisis. To date, habitat diversity on islands and spatial configuration of archipelagos have received less attention than classical island area and isolation. Moreover, in the field where experiments are impossible, correlative methods have dominated, despite the call for more mechanistic approaches. We developed an agent‐based computer simulation to study the effect of habitat diversity and archipelago configuration on plant species richness and composition in five archipelagos worldwide (Hawaii, Galapagos, Canary Islands, Cape Verde and Azores) and compared simulated diversity patterns to the empirical data. Habitat diversity proved to be an important factor to achieve realistic simulation results in all five archipelagos, whereas spatial structure of archipelagos was important in more elongated archipelagos. In most cases, simulation results correlate stronger with spermatophyte than with pteridophyte data, which we suggest can be attributed to the different dispersal and evolution rates of the two species groups. Correlation strength between simulated and observed diversity also varied among archipelagos, suggesting that geological and biogeographic histories of archipelagos have affected the species richness and composition on the islands. Our study demonstrates that a relatively simple computer simulation involving just a few essential processes can largely emulate patterns of archipelagic species richness and composition and serve as a powerful additional method to complement empirical approaches.     

Island ecology and contingent theory: the role of spatial scale and taxonomic bias

Scale, the scale dependency of patterns and processes, and the ways that organisms scale their responses to these patterns and processes are central to island and landscape ecology. Here, we take a database of studies in island ecology and investigate how studies have changed over a 40-year period with respect to spatial scale and organisms studied. We demonstrate that there have been changes in the spatial scale of islands studied and that there is taxonomic bias in favour of vertebrates in island ecological studies when compared to scientific publications as a whole. We discuss how such taxonomic bias may have arisen and discuss the implications for ecology and biogeography.