Evolutionary assembly of island faunas reverses the classic island–mainland richness difference in Anolis lizards

Aim Islands are widely considered to be species depauperate relative to mainlands but, somewhat paradoxically, are also host to many striking adaptive radiations. Here, focusing on Anolis lizards, we investigate if cladogenetic processes can reconcile these observations by determining if in situ speciation can reduce, or even reverse, the classical island–mainland richness discrepancy. Location Caribbean islands and the Neotropical mainland. Methods We constructed range maps for 203 mainland anoles from museum records and evaluated whether geographical area could account for differences in species richness between island and mainland anole faunas. We compared the island species–area relationship with total mainland anole diversity and with the richness of island‐sized mainland areas. We evaluated the role of climate in the observed differences by using Bayesian model averaging to predict island richness based on the mainland climate–richness relationship. Lastly, we used a published phylogeny and stochastic mapping of ancestral states to determine if speciation rate was greater on islands, after accounting for differences in geographical area. Results Islands dominated by in situ speciation had, on average, significantly more species than similarly sized mainland regions, but islands where in situ speciation has not occurred were species depauperate relative to mainland areas. Results were similar at the scale of the entire mainland, although marginally non‐significant. These findings held even after accounting for climate. Speciation has not been faster on islands; instead, when extinction was assumed to be low, speciation rate varied consistently with geographical area. When extinction was high, there was some evidence that mainland speciation was faster than expected based on area. Main conclusions Our results indicate that evolutionary assembly of island faunas can reverse the general pattern of reduced species richness on islands relative to mainlands.     

Are island and mainland biotas different? Richness and level of generalism in parasitoids of a microlepidopteran in Macaronesia

Island communities are exposed to several evolutionary and ecological processes that lead to changes in their diversity and structure compared to mainland biotas. These phenomena have been observed for various taxa but not for parasitoids, a key group in terms of community diversity and functioning. Here we use the parasitoid communities associated with the moth Acroclita subsequana (Lepidoptera: Tortricidae) in the Macaronesian region, to test whether species richness differs between islands and mainland, and whether island parasitoid faunas are biased towards generalist species. Host larvae were collected on several islands and adjacent mainland, carefully searched for ectoparasitoid larvae and dissected to recover any endoparasitoids. Parasitoids were classified as idiobionts, which usually have a wide host range (i.e. generalists), or koinobionts that are considered specialists. Mainland species richness was lower than expected by chance, with most of the species being koinobionts. On the other hand, island communities showed a greater proportion of idiobiont species. Overall parasitism rates were similar between islands and mainland, but islands had higher rates of parasitism by idiobionts than expected by chance, and mainland areas showed the highest koinobiont parasitism rates. These results suggest that island parasitoid communities are dominated by generalists, in comparison to mainland communities. Several hypotheses may explain this pattern: (1) generalist parasitoids might have better dispersal abilities; (2) they may be less constrained by ‘sequential dependencies’; and (3) island parasitoids probably have fewer competitors and/or predators, thus favouring the establishment of generalists. New studies including multiple hosts, other habitats, and/or more islands are necessary to identify which of these processes shape island parasitoid communities.     

Species–area relationships in the Andaman and Nicobar Islands emerge because rarer species are disproportionately favored on larger islands

The island species–area relationship (ISAR) describes how the number of species increases with increasing size of an island (or island‐like habitat), and is of fundamental importance in island biogeography and conservation. Here, we use a framework based on individual‐based rarefaction to infer whether ISARs result from passive sampling, or whether some processes are acting beyond sampling (e.g., disproportionate effects and/or habitat heterogeneity). Using data on total and relative abundances of four taxa (birds, butterflies, amphibians, and reptiles) from multiple islands in the Andaman and Nicobar archipelago, we examine how different metrics of biodiversity (total species richness, rarefied species richness, and abundance‐weighted effective numbers of species emphasizing common species) vary with island area. Total species richness increased for all taxa, as did rarefied species richness controlling for a given sampling effort. This indicates that the ISAR did not result because of passive sampling, but that instead, some species were disproportionately favored on larger islands. For birds, frogs, and lizards, this disproportionate effect was only associated with species that were rarer in the samples, but for butterflies, both more common and rarer species were affected. Furthermore, for the two taxa for which we had plot‐level data (reptiles and amphibians), within‐island β‐diversity did not increase with island size, suggesting that within‐island compositional effects were unlikely to be driving these ISARs. Overall, our results indicate that the ISARs of these taxa are most likely driven by disproportionate effects, that is, where larger islands are important sources of biodiversity beyond a simple sampling expectation, especially through their influence on rarer species, thus emphasizing their role in the preservation and conservation of species.     

Bird assemblages on Amazonian river islands: Patterns of species diversity and composition

The principles of island biogeography are rarely applied to the animal assemblages of Amazonian river islands. Here, we compare bird assemblages of Amazonian river islands with a variety of mainland habitats. We also examine how bird species diversity and composition are related to island physical attributes. Birds were sampled with mist nets and qualitative censuses on 11 river islands and 24 mainland sites on the lower reaches of the Rio Negro in the Brazilian Amazon. Island bird assemblages were characterized by lower species richness and a higher abundance of a few dominant species. Additionally, the species composition of the islands was distinct from that of the mainland, including the nearby floodplain habitats. The number of bird species increased with island size and habitat diversity, and decreased with degree of isolation. In addition, small islands tended to harbor an impoverished subset of the species present on larger ones. Bird species diversity and composition on Amazonian river islands are likely influenced by the ecological succession and historical events affecting island formation. Considering their small total area across the Amazon basin, these insular fluvial communities could be disproportionately threatened by river channel disturbances related to climate change or hydroelectric dam development. Abstract in Portughese is available with online material.     

生境片段化对千岛湖地表甲虫物种多样性的影响

在千岛湖片段化景观中选取20个陆桥岛屿和8个大陆样点,从2012年7月到2014年4月,按季度(春、夏、秋季)6次采用巴氏陷阱法收集地表甲虫,分析其物种多度、组成、多样性和季节动态,以及不同岛屿上的地表甲虫的物种多样性与岛屿面积和隔离度等岛屿空间特征的关系.结果表明: 共收集记录到地表甲虫26科101种3370头.大陆和大岛地表甲虫的物种丰富度有显著差异,且小岛地表甲虫密度显著高于大陆;大陆地表甲虫的物种组成变化较大,而岛屿上分布的地表甲虫的物种组成则变化较小.地表甲虫的物种丰富度与岛屿面积呈显著正相关,密度与隔离度呈显著正相关.夏季岛屿上地表甲虫物种丰富度高于春秋两季,岛屿与大陆样地的Shannon指数、Simpson指数和Pielou均匀度指数均在夏季最高、秋季最低.     

Nestedness in island faunas: novel insights into island biogeography through butterfly community profiles of colonization ability and migration capacity

Aim To relate variation in the migration capacity and colonization ability of island communities to island geography and species island occupancy. Location Islands off mainland Britain and Ireland. Methods Mean migration (transfer) capacity and colonization (establishment) ability (ecological indices), indexed from 12 ecological variables for 56 butterfly species living on 103 islands, were related to species nestedness, island and mainland source geography and indices using linear regression models, RLQ analysis and fourth‐corner analysis. Random creation of faunas from source species, rank correlation and rank regression were used to examine differences between island and source ecological indices, and relationships to island geography. Results Island butterfly faunas are highly nested. The two ecological indices related closely to island occupancy, nestedness rank of species, island richness and geography. The key variables related to migration capacity were island area and isolation; for colonization ability they were area, isolation and longitude. Compared with colonization ability, migration capacity was found to correlate more strongly with island species occupancy and species richness. For island faunas, the means for both ecological indices decreased, and variation increased, with increasing island species richness. Mean colonization ability and migration capacity values were significantly higher for island faunas than for mainland source faunas, but these differences decreased with island latitude. Main conclusions The nested pattern of butterfly species on islands off mainland Britain and Ireland relates strongly to colonization ability but especially to migration capacity. Differences in colonization ability among species are most obvious for large, topographically varied islands. Generalists with abundant multiple resources and greater migration capacity are found on all islands, whereas specialists are restricted to large islands with varied and long‐lived biotopes, and islands close to shore. The inference is that source–sink dynamics dominate butterfly distributions on British and Irish islands; species are capable of dispersing to new areas, but, with the exception of large and northern islands, facilities (resources) for permanent colonization are limited. The pattern of colonization ability and migration capacity is likely to be repeated for mainland areas, where such indices should provide useful independent measures for assessing the conservation status of faunas within spatial units.     

Pathogen richness and abundance predict patterns of adaptive major histocompatibility complex variation in insular amphibians

The identification of the factors responsible for genetic variation and differentiation at adaptive loci can provide important insights into the evolutionary process and is crucial for the effective management of threatened species. We studied the impact of environmental viral richness and abundance on functional diversity and differentiation of the MHC class Ia locus in populations of the black‐spotted pond frog (Pelophylax nigromaculatus), an IUCN‐listed species, on 24 land‐bridge islands of the Zhoushan Archipelago and three nearby mainland sites. We found a high proportion of private MHC alleles in mainland and insular populations, corresponding to 32 distinct functional supertypes, and strong positive selection on MHC antigen‐binding sites in all populations. Viral pathogen diversity and abundance were reduced at island sites relative to the mainland, and islands housed distinctive viral communities. Standardized MHC diversity at island sites exceeded that found at neutral microsatellites, and the representation of key functional supertypes was positively correlated with the abundance of specific viruses in the environment (Frog virus 3 and Ambystoma tigrinum virus). These results indicate that pathogen‐driven diversifying selection can play an important role in maintaining functionally important MHC variation following island isolation, highlighting the importance of considering functionally important genetic variation and host–pathogen associations in conservation planning and management.     

Ant communities on small tropical islands: effects of island size and isolation are obscured by habitat disturbance and ‘tramp’ ant species

Aim Comparisons among islands offer an opportunity to study the effects of biotic and abiotic factors on small, replicated biological communities. Smaller population sizes on islands accelerate some ecological processes, which may decrease the time needed for perturbations to affect community composition. We surveyed ants on 18 small tropical islands to determine the effects of island size, isolation from the mainland, and habitat disturbance on ant community composition. Location Thousand Islands Archipelago (Indonesian name: Kepulauan Seribu) off Jakarta, West Java, Indonesia. Methods Ants were sampled from the soil surface, leaf litter and vegetation in all habitat types on each island. Island size, isolation from the mainland, and land‐use patterns were quantified using GIS software. The presence of settlements and of boat docks were used as indicators of anthropogenic disturbance. The richness of ant communities and non‐tramp ant species on each island were analysed in relation to the islands’ physical characteristics and indicators of human disturbance. Results Forty‐eight ant species from 5 subfamilies and 28 genera were recorded from the archipelago, and approximately 20% of the ant species were well‐known human‐commensal ‘tramp’ species. Islands with boat docks or human settlements had significantly more tramp species than did islands lacking these indicators of anthropogenic disturbance, and the diversity of non‐tramp species decreased with habitat disturbance. Main conclusions Human disturbance on islands in the Thousand Islands Archipelago promotes the introduction and/or establishment of tramp species. Tramp species affect the composition of insular ant communities, and expected biogeographical patterns of ant richness are masked. The island with the greatest estimated species richness and the greatest number of unique ant species, Rambut Island, is a forested bird sanctuary, highlighting the importance of protected areas in preserving the diversity of species‐rich invertebrate faunas.     

Abundance-age-area relationships in an insular plant community

Two processes are thought to generate positive relationships between species richness and island area. The areaper se hypothesis states that larger islands maintain larger populations, which are less susceptible to extinction. The habitat hypothesis states that larger islands contain more habitats, and therefore a greater number of habitat specialists. However, the importance of each mechanism is debated. I tested the areaper se and habitat hypotheses by comparing relationships between plant abundance, age and island area in five shrub species on islands off the coast of British Columbia, Canada. Results showed that two shrub species increased in both abundance and age with island area. The remaining three species showed no differences in abundance and age with island area. Conifer abundances increased with island area, which generated differences in habitat availability. Smaller islands were dominated by open habitat, while larger islands contained both open and forested habitats. Changes in habitat availability with island area could explain patterns in plant abundance and age. The two species that increased in abundance with island area were commonly found in conifer forest on the mainland, and their distributions were consistent with the distribution forest habitat. Positive relationships between plant age and island area in these two species may result from lower survivorship in the open habitat, which dominated small islands. The three species that showed no relationship between abundance and island area are commonly found in open habitat on the mainland, and their island distributions paralleled the availability of open habitat on islands. Similar plant ages on different sized islands may result from their occurrence in open habitat on both large and small islands. Overall results support the habitat hypothesis and indicate that species distributions result from the interaction between habitat affinities and changes in habitat availability with island area.     

Drivers of diversity in Macaronesian spiders and the role of species extinctions

Aim To identify the biogeographical factors underlying spider species richness in the Macaronesian region and assess the importance of species extinctions in shaping the current diversity. Location The European archipelagos of Macaronesia with an emphasis on the Azores and Canary Islands. Methods Seven variables were tested as predictors of single‐island endemics (SIE), archipelago endemics and indigenous spider species richness in the Azores, Canary Islands and Macaronesia as a whole: island area; geological age; maximum elevation; distance from mainland; distance from the closest island; distance from an older island; and natural forest area remaining per island – a measure of deforestation (the latter only in the Azores). Different mathematical formulations of the general dynamic model of oceanic island biogeography (GDM) were also tested. Results Island area and the proportion of remaining natural forest were the best predictors of species richness in the Azores. In the Canary Islands, area alone did not explain the richness of spiders. However, a hump‐shaped relationship between richness and time was apparent in these islands. The island richness in Macaronesia was correlated with island area, geological age, maximum elevation and distance to mainland. Main conclusions In Macaronesia as a whole, area, island age, the large distance that separates the Azores from the mainland, and the recent disappearance of native habitats with subsequent unrecorded extinctions seem to be the most probable explanations for the current observed richness. In the Canary Islands, the GDM model is strongly supported by many genera that radiated early, reached a peak at intermediate island ages, and have gone extinct on older, eroded islands. In the Azores, the unrecorded extinctions of many species in the oldest, most disturbed islands seem to be one of the main drivers of the current richness patterns. Spiders, the most important terrestrial predators on these islands, may be acting as early indicators for the future disappearance of other insular taxa.     

Biogeography and the structure of coral reef fish communities on isolated islands

Aim To determine the applicability of biogeographical and ecological theory to marine species at two remote island locations. This study examines how biogeography, isolation and species geographic range size influence patterns of species richness, endemism, species composition and the abundance of coral reef fishes. Location Christmas Island and the Cocos (Keeling) Islands in the tropical eastern Indian Ocean. Methods Published species lists and underwater visual surveys were used to determine species richness, endemism, species composition and abundance of reef fishes at the islands. These data were statistically compared with patterns of species composition and abundance from the neighbouring ‘mainland’ Indonesian region. Results The two isolated reef fish communities were species‐poor and contained a distinct taxonomic composition with an overrepresentation of species with high dispersal potential. Despite low species richness, we found no evidence of density compensation, with population densities on the islands similar to those of species‐rich mainland assemblages. The mix of Indian and Pacific Ocean species and the proportional representations of the various regional faunas in the assemblages were not influenced by the relative proximity of the islands to different biogeographical provinces. Moreover, species at the edge of their range did not have a lower abundance than species at the centre of their range, and endemic species had substantially higher abundances than widespread species. At both locations, endemism was low (less than 1.2% of the community); this may be because the locations are not sufficiently isolated or old enough to promote the evolution of endemic species. Main conclusions The patterns observed generally conform to terrestrial biogeographical theory, suggesting that similar processes may be influencing species richness and community composition in reef fish communities at these remote islands. However, species abundances differed from typical terrestrial patterns, and this may be because of the life history of reef fishes and the processes maintaining isolated populations.     

Dung beetle assemblages on tropical land‐bridge islands: small island effect and vulnerable species

Aim Using dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) in a tropical land‐bridge island system, we test for the small island effect (SIE) in the species–area relationship and evaluate its effects on species richness and community composition. We also examine the determinants of species richness across island size and investigate the traits of dung beetle species in relation to their local extinction vulnerability following forest fragmentation. Location Lake Kenyir, a hydroelectric reservoir in north‐eastern Peninsular Malaysia. Methods We sampled dung beetles using human dung baited pitfall traps on 24 land‐bridge islands and three mainland sites. We used regression tree analyses to test for the SIE, as well as species traits related to local rarity, as an indication of extinction vulnerability. We employed generalized linear models (GLMs) to examine determinants for species richness at different scales and compared the results with those from conventional linear and breakpoint regressions. Community analyses included non‐metric multidimensional scaling, partial Mantel tests, nestedness analysis and abundance spectra. Results Regression tree analysis revealed an area threshold at 35.8 ha indicating an SIE. Tree basal area was the most important predictor of species richness on small islands (<35.8 ha). Results from GLMs supported these findings, with isolation and edge index also being important for small islands. The SIE also manifested in patterns of dung beetle community composition where communities on small islands (<35.8 ha) departed from those on the mainland and larger islands, and were highly variable with no significant nestedness, probably as a result of unexpected species occurrences on several small islands. The communities exhibited a low degree of spatial autocorrelation, suggesting that dispersal limitation plays a part in structuring dung beetle assemblages. Species with lower baseline density and an inability to forage on the forest edge were found to be rarer among sites and hence more prone to local extinction. Main conclusions We highlight the stochastic nature of dung beetle community composition on small islands and argue that this results in reduced ecosystem functionality. A better understanding of the minimum fragment size required for retaining functional ecological communities will be important for effective conservation management and the maintenance of tropical forest ecosystem stability.     

Mammals of Australian islands: factors influencing species richness

Distribution patterns of indigenous non-volant terrestrial mammals on 257 Australian islands were examined in relation to environmental parameters and the effects of human-induced disturbance during prehistoric and historic times on island species numbers. Species occurrence for individual species, for taxonomic and trophic groups, and for all species together was related to environmental parameters using regression analysis and the extreme-value function model. Patterns of occurrence were examined separately within three major biogeographic regions derived by pattern analysis. The number of species known to have occurred on these islands during historic times was adequately predicted from area alone. No statistically significant improvement in predicted species number was gained by including island elevation, mean annual rainfall, isolation from the mainland or the number of potentially competing species present on the island. Similarly, no single factor other than area was found to influence consistently the presence of individual species. We conclude that the occurrence of indigenous non-volant terrestrial mammal species on these islands indicates a relictual rather than equilibrial fauna. Visitation by Aboriginal people during prehistoric times did not significantly increase mammal extinctions on islands. Examination of patterns of species richness for a given area on a regional basis showed that islands in and around Bass Strait and Tasmania (Bass Region) were the most species-rich, islands off the northern coasts were slightly less rich, and islands off the south western coasts had fewest species. This is in contrast to the usual latitudinal gradient in species richness patterns. However, islands off the northern and eastern coasts had an overall greater number of different species. When considered in relation to the number of different species of mammals occurring within each region, islands of a given size in Bass Region typically bore a higher proportion of this species pool than other regions. The Bass Region was found to be particularly rich in macropoid herbivores and dasyurid carnivores and insectivores. Analyses indicated that there is a very strong relationship between the presence of exotics as a whole and the local extinction of native mammals. Many mammal species formerly widespread on the Australian mainland are now restricted totally to islands (nine species) or are threatened with extinction on the mainland and have island populations of conservation significance (ten species). In all, thirty-five islands protect eighteen taxa of Australian threatened mammals. The land-use and management of these islands is of considerable importance to nature conservation. The introduction of exotic mammals to these islands should be prevented; any introductions that occur should be eradicated immediately.     

Biogeographical determinants for total and endemic species richness in a continental archipelago

We examined the relationship between plant species richness and biogeographical variables (island area, island maximum elevation, distance from nearest inhabited island, distance from nearest mainland) using a data set comprising 201 islands of the Aegean archipelago. We found that endemic species richness was strongly correlated to total species richness. Single-island endemic species richness was most strongly correlated to island maximum elevation, and then to island area, with an apparent small island effect for islands smaller than 47 km². Total species richness was most strongly correlated to island area (with no apparent small island effect), and less strongly correlated to island maximum elevation. Distance from the mainland or other inhabited islands displayed limited predictive value in our data set. The slope of the relationship between species richness and geographical factors (island area, elevation, distance from island/mainland) was steeper for endemic species richness than for total richness. Finally, the different scales of endemicity (single-island endemics, island group endemics and Aegean regional endemics) displayed similar qualitative trends and only differed quantitatively. Thus, we conclude that different biogeographical factors act as drivers for total species richness than for endemic species richness.     

Predicting local–regional richness relationships using island biogeography models

Local species richness frequently is linearly related to the richness of the regional species pool from which the local community was presumably assembled. What, if anything, does this pattern imply about the relative importance of species interactions and dispersal as determinants of local species richness? Two recent papers by Hugueny and Cornell and He et al. propose that the classical island biogeography model of MacArthur and Wilson can help answer this question, by serving as a null model of the relationship between local (island) and regional (mainland) species richness in the absence of local species interactions. The two models make very different predictions, despite being derived from apparently‐similar assumptions. Here we reinterpret these two models and show that their contrasting predictions can be regarded as arising from different, implicit assumptions about how species abundances vary with species richness on the mainland. We derive a more general island biogeography model of local–regional richness relationships that explicitly incorporates mainland species abundance and subsumes the two previous models as limiting cases. The new model predicts that the local–regional richness relationship can range from nearly linear to strongly curvilinear, depending on how species abundances on the mainland vary with mainland richness, as well as on rates of immigration to and extinction from islands. Local species interactions are not necessary for producing curvilinear local–regional richness relationships. We discuss the implications of our new model for the interpretation of local–regional richness relationships.     

Terrestrial bird community patterns on the coralline islands of the Dahlak Archipelago, Red Sea, Eritrea

Aim This study aims to explain the patterns of species richness and nestedness of a terrestrial bird community in a poorly studied region. Location Twenty‐six islands in the Dahlak Archipelago, Southern Red Sea, Eritrea. Methods The islands and five mainland areas were censused in summer 1999 and winter 2001. To study the importance of island size, isolation from the mainland and inter‐island distance, I used constrained null models for the nestedness temperature calculator and a cluster analysis. Results Species richness depended on island area and isolation from the mainland. Nestedness was detected, even when passive sampling was accounted for. The nested rank of islands was correlated with area and species richness, but not with isolation. Idiosyncrasies appeared among species‐poor and species‐rich islands, and among common and rare species. Cluster analysis showed differences among species‐rich islands, close similarity among species‐poor and idiosyncratic islands, and that the compositional similarity among islands decreased with increasing inter‐island distance. Thus, faunas of species‐poor, smaller islands were more likely to be subsets of faunas of species‐rich, larger islands if the distance between the islands was short. Main conclusions Species richness and nestedness were related to island area, and nestedness also to inter‐island distances but not to isolation from the mainland. Thus, nestedness and species richness are not affected in the same way by area and distance. Moreover, idiosyncrasies may have been the outcome of species distributions among islands being influenced also by non‐nested distributions of habitats, inter–specific interactions, and differences in species distributions across the mainland. Idiosyncrasies in nested patterns may be as important as the nested pattern itself for conservation – and conservation strategies based on nestedness and strong area effects (e.g. protection of only larger islands) may fail to preserve idiosyncratic species/habitats.     

Mediterranean island biogeography: Analysis of fern species distribution in the system of islets around Sicily

Abstract

The aim of this article was to test the way in which geographical factors influence island floras in the Mediterranean basin, using ferns as target organisms, and the islands surrounding Sicily as location. A matrix with presence/absence data concerning fern taxa in the 16 islands studied was compiled. Cluster analysis, principal co-ordinates analysis (PCoA), principal components analysis (PCA) and a Bayesian analysis were performed. For each island, the total number of fern taxa was regressed against three factors: island area, island elevation and isolation. All the analyses pointed to affinities between islands according to their different geological composition, independently from their geographic position. A clear positive island species/area relationship (ISAR) was shown only for the volcanic islands. The island species/(area×elevation) relationship (ISAER), on the contrary, was unsatisfactory. The main features of interest are the following: (1) the clear division of the islands into two groups, volcanic vs. sedimentary; (2) the floristic richness of the volcanic compared to sedimentary islands and (3) the uniqueness of the pteridophyte flora of Pantelleria. This seems to demonstrate that the lower number of taxa in the islands farthest away from the “mainland” (Sicily, Tunisia) is not due to isolation, but due to another factor, probably habitat availability.     

海岛陆地生态系统固碳估算方法

陆地生态系统在调节全球碳平衡和减缓全球气候变化中起着重要作用。海岛作为一种特殊的生态系统,生物群落和环境与大陆基本相似。虽然海岛生态结构相对简单,物种的丰富程度比大陆低,但对全球碳循环也有一定的影响。在海岛陆地生态系统中,森林和灌草的种属相对较少,且不同纬度的海岛森林植被种属差异明显,可采用典型样地清查和生物量模型估算相结合的方法估算乔木层和灌草层的碳储量。采用模型估算固碳潜力时,根据海岛生态环境的特殊性,综合考虑岛陆面积、季节、风向、坡度、坡向、海拔、平均温度、降雨量、土壤理化性质等参数对其碳储量估算的影响。海岛植被生物多样性影响其土壤碳储存的生态服务功能,利用多元统计分析方法,建立岛陆植物物种丰度与土壤碳储量的空间回归模型,明确植物多样性的改变对岛陆土壤固碳能力的影响。此外,从土壤固碳的角度而言,海岛土壤-植物-微生物间相互作用是其重要的研究方向。利用现代分子生物学技术,研究海岛陆地生态系统的土壤-植物-微生物相互作用关系,有利于海岛土壤固碳潜力估算精度的提高。     

Area effect of distribution of Silphids (Coleoptera,Silphidae) on Korean islands

We investigated the spatial patterns in the distribution of carrion beetles on 26 islands to test the area and distance effects on species diversity. The relationships between species richness and assemblage and island area, distance from the mainland, and shortest distance from the largest island within 2?km were analyzed using linear regression, Canonical Correspondence Analysis (CCA) and Multi-Response Permutation Procedures (MRPP). We hypothesized that both area and distance from the mainland played a significant role in species richness, while geographic location in the sea influenced aggregation of carrion beetles on islands. Area was the only factor influencing species richness of carrion beetles on islands. Moreover, distance from the mainland and close islands did not significantly influence to carrion beetles. In addition, geographic location in the same Sea did not influence beetle assemblages. Taken together, the results of this study indicated that carrion beetles on Korean islands were largely affected by island size and that dispersal was stochastic.     

Patterns of invertebrate density and taxonomic richness across gradients of area,isolation, and vegetation diversity in a lake‐island system

Over the past half century, ecologists have tried to unravel the factors that drive species richness patterns in ecological communities. One influential theory is island biogeography theory (IBT), which predicts that island or habitat area and isolation are drivers of species richness. However, relatively few studies testing IBT have considered invertebrate or belowground communities, and it is unclear as to whether the predictions made by IBT hold for these communities. Other theories predict that habitat characteristics such as vegetation diversity may be important drivers of invertebrate species richness. To investigate patterns of invertebrate density and species richness across gradients of area, isolation, and vegetation diversity, we used a system of 30 lake islands in the boreal zone of northern Sweden. We assessed density and taxonomic richness of ground‐dwelling spiders, web‐building spiders, beetles, collembolans, mites, and nematodes, for all islands during two consecutive summers. For all invertebrate groups, both density and taxonomic richness were either neutrally or negatively related to island size, and either neutrally or positively related to island isolation. Meanwhile the density and taxonomic richness for several groups was positively related to vegetation diversity (i.e. habitat heterogeneity). In multiple regression analyses, island size was often the single best predictor for both invertebrate density and taxonomic richness, but in some cases island size and isolation in combination explained more variation than each factor considered singly. Contrary to IBT predictions, invertebrate density and richness was never positively related to island size or negatively related to island isolation. Instead, our results suggest that plant diversity (and thus habitat heterogeneity) was the main driver of the patterns that we found, although other factors could have some influence. We conclude that several factors, but not necessarily those predicted as important by IBT, are important in determining invertebrate abundance and species richness in island systems.