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     

The environmental determinants of the insular butterfly faunas of the British Isles

A multiple regression analysis was performed upon selected environmental variables for a series of islands in the British Isles, to establish their effects upon the size of the butterfly fauna, measured as he number of species regularly breeding, S_B .
So that the data be normally distributed, the regression analyses were performed upon log₁₀ transformed data only, with the data for outliers, mainland Britain and Ireland, the two largest islands, excluded.
Most highly correlated with the number of butterfly species breeding upon an island is the number breeding within a 25 km radius of the nearest point of the mainland, r ²=0.5941, followed by the correlations with the latitude of the mid-point of the island, r ²=0.5541, the number of plant species comprising the island Hora, r ²=0.5225, and the distance separating the island from the mainland, r ²=0.4514.
A partial correlation analysis confirms the importance of the parameters distance separating the island from the mainland, D ₁, and the size of the faunal source S _F , and rejects the importance of the size of the flora and the latitude of the island. This is further confirmed by the results of a step-wise regression analysis, the two variables D ₁ and S_F accounting for 66% of the variation of the butterfly fauna.
If an alternative measure of isolation, D ₂, which allows for the geographical clumping of islands, is combined with the variable S_F , then 69% of the variation of the butterfly fauna is accounted for.     

Geographical,anthropogenic and climatic determinants of bryophyte species composition and richness in the Shengsi archipelago,East China Sea

Introduction. Few attempts have been made to assess the comparative contributions of different environmental factors on species composition (SC) and richness (SR) of bryophytes on continental islands.

Methods. The bryophyte flora and the impact of seven environmental variables (island area, elevation, isolation, human disturbance, rainfall, vegetation cover, and exposed rock area) on 18 continental islands of the Shengsi archipelago in the East China Sea were investigated. Redundancy Analysis and Canonical Correspondence Analysis were used to determine to what extent the environmental variables could explain variation in species richness and species composition on these islands.

Key results & Conclusions. Island elevation, isolation, area and human disturbance intensity all significantly influenced bryophyte SC at island level, accounting for 12.7%, 9.9%, 8.8% and 7.8% of the total SC variation, respectively. Island area was the most important determinant of bryophyte SR (P?=?0.002), accounting for 58.3% of the total variation (9.7% by area per se and 48.6% confounded with other variables); elevation and human disturbance intensity also significantly influenced species richness, accounting for 10.5% and 6.9% of the total SR variation (conditional effects), respectively. Elevation and area had a positive interaction effect on SR while isolation exerted no significant effects (P?>?0.05). The relationships of bryophyte species number (S) with area (A) follow log₁₀ (S)?=?c?+?z?×?log₁₀ (A), with z values from 0.28 to 0.38. The effects of human disturbance on bryophyte SR followed the Gaussian model, supporting the ‘intermediate disturbance hypothesis’ to some extent.     

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.     

Erosion of community diversity and stability by herbivore removal under warming

Climate change has the potential to influence the persistence of ecological communities by altering their stability properties. One of the major drivers of community stability is species diversity, which is itself expected to be altered by climate change in many systems. The extent to which climatic effects on community stability may be buffered by the influence of species interactions on diversity is, however, poorly understood because of a paucity of studies incorporating interactions between abiotic and biotic factors. Here, I report results of a 10-year field experiment, the past 7 years of which have focused on effects of ongoing warming and herbivore removal on diversity and stability within the plant community, where competitive species interactions are mediated by exploitation through herbivory. Across the entire plant community, stability increased with diversity, but both stability and diversity were reduced by herbivore removal, warming and their interaction. Within the most species-rich functional group in the community, forbs, warming reduced species diversity, and both warming and herbivore removal reduced the strength of the relationship between diversity and stability. Species interactions, such as exploitation, may thus buffer communities against destabilizing influences of climate change, and intact populations of large herbivores, in particular, may prove important in maintaining and promoting plant community diversity and stability in a changing climate.     

Ecological versus phylogenetic determinants of helminth parasite community richness

Summary We examine patterns of community richness among intestinal parasitic helminth communities in fishes, herptiles, birds and mammals with respect to the comparative number of component species in a host population. We show that terrestrial hosts have, on average, fewer component species than aquatic hosts. We also show that the mean number of component species in aquatic hosts increases from fishes through herptiles to birds before declining slightly in mammals. For terrestrial hosts, the mean number of component species increases from herptiles, through birds, reaching a maximum in mammals. We conclude that: (i) habitat of the host is more important in determining community richness than is host phylogeny; (ii) the phenomenon of host capture may be largely responsible for increased species richness in some host groups; (iii) aquatic birds harbour the richest intestinal helminth communities; and (iv) as we interpret them, our data refute the time hypothesis, which would predict that fishes as the oldest lifestyle should have the richest helminth communities.Order of authorship determined by random draw and does not imply seniority.     

Global diversity of island floras from a macroecological perspective

Islands harbour a significant portion of all plant species worldwide. Their biota are often characterized by narrow distributions and are particularly susceptible to biological invasions and climate change. To date, the global richness pattern of islands is only poorly documented and factors causing differences in species numbers remain controversial. Here, we present the first global analysis of 488 island and 970 mainland floras. We test the relationship between island characteristics (area, isolation, topography, climate and geology) and species richness using traditional and spatial models. Area is the strongest determinant of island species numbers ( R ² = 0.66) but a weaker predictor for mainlands ( R ² = 0.25). Multivariate analyses reveal that all investigated variables significantly contribute to insular species richness with area being the strongest followed by isolation, temperature and precipitation with about equally strong effects. Elevation and island geology show relatively weak yet significant effects. Together these variables account for 85% of the global variation in species richness.     

The species diversity, distributionand conservation of Namibian mammals

Namibia's extant mammal fauna of 250 species represents about 75% of the southern African region's species richness, 83% of generic richness and 98% of familial richness. Fourteen species are presently recognized as endemic (75% or more of the global population occurring within Namibian borders). These endemics occur in the Namib Desert, pro-Namib transition zone and adjoining escarpment, and are primarily rupicolous. The Namibian endemic mammal fauna is characterized by the monotypic Petromuridae, and the rodent genera Gerbillurus and Petromyscus. The distribution of smaller species has probably not changed significantly over the past 200 years, but species such as lion and plain zebra have undergone range reductions of 95% or more, and five species are listed as recently extinct. Approximately 50% of all Namibian mammal species are provisionally listed as 'secure'. However, due to patchy data, 94 species (38%) are classified as under possible or probable threat. Nineteen species (8%) are classified as under definite threat. Over 13% of Namibia is set aside by the state for conservation purposes. Ninety-five percent of mammal species occur in at least one park, over 80% occur in three or more parks, and 59 species (28%) occur in ten or more parks, although for most species nothing is known of their population viability there. Major threats to mammals in Namibia are invasive aliens, including the risk of genetic pollution, and habitat alteration, especially wetland degradation.     

Evaluation of community indices in seasonal assemblages of butterflies (Lepidoptera) at different frequency of transect count

Community indices were evaluated at different frequency of transect counts of butterflies by randomization. Randomized samples were obtained by re-arranging 1, 3, 6, 12 and 18 counts from 18 counts at a study site (Hiraoka), and 1, 2, 3, 5 and 15 from 15 at another site (Narukawa), in 1994. Morisita's new estimate of species richness, QM gave a good estimate when the number of counts was five or more. QM estimated from the sum of both assemblages (58 species) was 70.7, while 73 species were recorded at least once from 1990 to 1994. The Octave method always resulted in an underestimation. Diversity indices, Shannon's H, Simpson's D and , Hurlbert's E(Sn), Itow's b, and Morisita's H gave good estimates when the number of counts was five or more. Temporariness of univoltine species in flight period made a bias in the estimates. We concluded that the count is needed at least six times (once a month) and the estimates were improved by separating the multivoltine species from the univoltine species. Intensive counting during the flight period of the univoltine species was recommended.     

The ground beetle fauna of ancient and recent woodlands in the lowlands of north-west Germany (Coleoptera, Carabidae)

In north-west Germany the ground beetle fauna was investigated using pitfall traps at 79 sampling sites in ancient woodlands and recent woodlands (with and without direct contact to old stands). Two woodland types were considered: The Quercion robori-petraea-woodlands (oak-beech-type) on mainly sandy soils and the Stellario-Carpinetum-woodlands (hornbeam-type) on mainly loamy soils. The number of recorded ground beetle species inhabiting exclusively or predominantly woodlands in the investigation area is significantly higher in ancient stands of both woodland types than in recent ones. No statistically substantiated relation between habitat size (both about 1800 and in 1990) and the number of characteristic woodland ground beetle species could be ascertained. Carabus glabratus and Abax parallelus show a distinct focus in ancient woodlands. Significantly more records of Carabus violaceus and Abax parallelepipedus are known from ancient woodlands than from recent ones. Twelve of the 16 ground beetle species, for which no difference in the colonisation of ancient and recent woodlands was ascertained, are macropterous. Half of the eight brachypterous woodland species is exclusively or predominantly found in ancient woodlands, suggesting that power of dispersal is an important factor which determines the species number in woodland fragments of different age.     

The effects of disturbance events on phytoplankton community structure in a small temperate reservoir

1 The effects of disturbances, in the form of storm events, on phytoplankton community structure were examined over the course of four years in Eau Galle Reservoir, Wisconsin, USA.
2 Disturbances consistently brought about significant, but highly transient, increases in apparent phytoplankton species richness. It is likely that these resulted from temporary increases in the biomass of previously undetected rare species.
3 Substantial shifts in community dominance were confined to large, early season events, and were seldom long-lived. Later 'climax' communities were highly resistant to any changes in dominance, even when increases in species richness occurred.
4 Regardless of when they occurred, disturbances tended to favour species from a narrow range of the successional sequence.     

Niche and metabolic principles explain patterns of diversity and distribution: theory and a case study with soil bacterial communities

The causes of biodiversity patterns are controversial and elusive due to complex environmental variation, covarying changes in communities, and lack of baseline and null theories to differentiate straightforward causes from more complex mechanisms. To address these limitations, we developed general diversity theory integrating metabolic principles with niche-based community assembly. We evaluated this theory by investigating patterns in the diversity and distribution of soil bacteria taxa across four orders of magnitude variation in spatial scale on an Antarctic mountainside in low complexity, highly oligotrophic soils. Our theory predicts that lower temperatures should reduce taxon niche widths along environmental gradients due to decreasing growth rates, and the changing niche widths should lead to contrasting α- and β-diversity patterns. In accord with the predictions, α-diversity, niche widths and occupancies decreased while β-diversity increased with increasing elevation and decreasing temperature. The theory also successfully predicts a hump-shaped relationship between α-diversity and pH and a negative relationship between α-diversity and salinity. Thus, a few simple principles explained systematic microbial diversity variation along multiple gradients. Such general theory can be used to disentangle baseline effects from more complex effects of temperature and other variables on biodiversity patterns in a variety of ecosystems and organisms.     

Flora diversity of farm forestry plantations in southeast Queensland

Summary Plant species composition in plantation monoculture of the native Gympie Messmate (Eucalyptus cloeziana F. Muell.) was assessed and compared with native eucalypt forest and cleared grazing land in southeast Queensland, Australia. A total of 18 sites (11 in the plantations, four in native eucalypt forests and three on cleared grazing land) were surveyed. The four plantation age classes during the 18‐month survey period were 0.3–1.8 (very young), 2.1–3.8 (young), 15–16.5 (mid‐aged) and 38–40.5 (old) years of age. Significantly more native plant species were recorded in the plantations, regardless of their age, than on cleared grazing land. The number of native plant species in the old plantations was not significantly different from the native eucalypt forests. Native tree and shrub species richness increased significantly with plantation age. Two species (Ricinocarpos speciosus Muell. Arg. and Xanthostemon oppositifolius F. M. Bailey) listed as Vulnerable and one species (Alyxia magnifolia F. M. Bailey) listed as Rare were recorded in the old plantations. Two Rare species (A. magnifolia and Acianthus amplexicaulis (F. M. Bailey) Rolfe) were recorded in the native eucalypt forests. Exotic plant species, consisting mainly of herbs, grasses and shrubs in the plantations, were significantly more abundant in the very young and young plantations. However, the number of exotic species decreased significantly with increasing age of the plantations. The results suggest that even small‐scale plantation can increase landscape heterogeneity and help protect biodiversity.