Diversity-area Relationship Research Articles

Phylogenetic and functional diversity area relationships in two temperate forests

Phylogenetic diversity (PD, the diversity of lineages) and functional diversity (FD, the diversity of functional traits or groups in a biological community) reflect important yet poorly understood attributes of species assemblages. Until recently, few studies have examined the spatial variation of PD and FD in natural communities. Yet the relationships between PD and FD and area (termed PDAR and FDAR), like the analogous species–area relationship (SAR), have received less attention and may provide insights into the mechanisms that shape the composition and dynamics of ecological communities. In this study, we used four spatial point process models to evaluate the likely roles of the random placement of species, habitat filtering, dispersal limitation, and the combined effects of habitat filtering and dispersal limitation in producing observed PDARs and FDARs in two large, fully mapped temperate forest research plots in northeast China and in north‐central USA. We found that the dispersal limitation hypothesis provided a good approximation of the accumulation of PD and FD with increasing area, as it did for the species area curves. PDAR and FDAR patterns were highly correlated with the SAR. We interpret this as evidence that species interactions, which are often influenced by phylogenetic and functional similarity, may be relatively unimportant in structuring temperate forest tree assemblages at this scale. However, the scale‐dependent departures of the PDAR and FDAR that emerged for the dispersal limitation hypothesis agree with operation of competitive exclusion at small scales and habitat filtering at larger scales. Our analysis illustrates how emergent community patterns in fully mapped temperate forest plots can be influenced by multiple underlying processes at different spatial scales.

The effect of spatially correlated environments on genetic diversity–area relationships

Understanding the spatial patterns of genetic diversity and what causes them is an important outstanding question in ecology. Here we investigate the roles of spatial heterogeneity and system area in generating genome diversity, and study its dependence with sampled area. We study an individual-based model that incorporates natural selection on the habitat type and compare the effects of asexual and sexual reproductions. A key ingredient of the model is the possibility to tune the level of spatial heterogeneity among the habitats. Our results corroborate either the bi-phasic or tri-phasic scenarios, one phase corresponding to a power law regime, for the diversity–area relationship in both sexual and asexual populations, being the shape of the curve influenced by mutation rates and spatial correlation. These observations are verified for distinct sets of parameter values.

Niches, body sizes, and the disassembly of mammal communities on the Sunda Shelf islands

The rising sea level at the end of the Pleistocene that created the islands of the Sunda Shelf in Indonesia and Malaysia provides a natural experiment in community disassembly and offers insights into the effects of body size and niches on abundance, distribution, and diversity. Since isolation, terrestrial mammal communities of these islands have been reduced by extinction, with virtually no offsetting colonization. We document three empirical patterns of disassembly, all of which are significantly different from null models of random assembly: (i) a diversity-area relationship: the number of taxa is strongly and positively correlated with island area; (ii) nested subset composition: species that occur on small islands tend to be subsets of more diverse communities inhabiting larger islands; and (iii) body size distributions: species of intermediate body sizes occur on the greatest number of islands, and smaller islands have smaller ranges of body sizes, caused by the absence of species of both very large and extremely small size. These patterns reveal the role of body size and other niche characteristics, such as habitat requirements and trophic status, in the differential susceptibility of taxa to extinction.

Species diversity and endemism of five major Malesian islands: diversity–area relationships

AbstractAim A comparison of biodiversity patterns within Malesia in relation to surface area.Location Analysis of the patterns in species richness and endemism of vascular plants in the five major Malesian islands, i.e. Java, Sulawesi, Sumatra, Borneo and New Guinea.Methods Available data on species richness and species ranges in correlation with the surface area of the respective islands were examined in this work. Estimations of total species numbers for these islands are presented based on extrapolation of all available published Flora Malesiana information and recent checklists, all in all comprising 12,000 different species. The regression analysis of overall species richness and endemism were studied for all species together as well as for different plant families to compare the fit with the Arrhenius species–area model.Results The five islands form a series of independent areas of increasing size suited for an analysis of the species–area relationships at the regional scale. All species taken together and those of families with even distribution throughout Malesia show significant species–area relationships. Non‐significant relationships were detected in families with western or eastern‐centred Malesian distribution patterns. Relationships between number of endemic species and surface area are significant for all species and for the majority of the families with significant species–area relationships.Main conclusions Species–area relationships of families appear to be dependent on species number. Families with high numbers of species usually have a significant species–area relationship whereas small families have not. For the families that display an eastern or western Malesian centred pattern, a historical biogeographical explanation should be invoked. Island surface area appears to be a predictor for island percent endemism in Malesian vascular plants. None of the islands appears to be a hotspot of endemism nor of species diversity, as no significant departure from the Arrhenius model was noted for any of them.

Pedodiversity-area relationships for islands

Our objectives were examine whether the pedotaxa-abundance distributions conform to abundance distribution models and how pedorichness-area data fit diversity-area models considered by ecologists. The study area selected was the Aegean Islands. Standard statistical methods were used to gauge the abundance distribution models (Smirnov–Kolmogorov test of goodness of fit) and pedorichness-area models (linear regression, log–log or semi-log). The Smirnov–Kolmogorov test of goodness of fit indicated that the logseries and the broken stick distribution models should be rejected, whereas the geometric and lognormal models were not rejected ( P<5%) Pedorichness-area relationships conform to a power law whose exponent is close to 0.25, as ecological literature predicts. No significant difference was observed between the abundance distribution models and the diversity-area relationships followed by biodiversity and pedodiversity data in similar situations.

Subsidized Island Biogeography Hypothesis: another new twist on an old theory

We present a new hypothesis for predicting and describing patterns of species diversity on small islands and habitat fragments. We have modified the traditional island biogeography equilibrium theory to incorporate the influence of spatial subsidies from the surrounding matrix, which vary among islands and habitat fragments, on species diversities. The modification indicates three possible directions for the effects of spatial subsidies on diversity, which depend on where the focal community falls on the hypothesized unimodal curve of the productivity–diversity relationship. The idea is novel because no recent syntheses of productivity–diversity–area relationships examine the role of allochthonous resources on recipient communities’ diversity patterns.

Scaling down: On the Challenge of Estimating Abundance from Occurrence Patterns

Scaling down: On the Challenge of Estimating Abundance from Occurrence Patterns

Studying canopy arthropods in New Caledonia: how to obtain a representative sample

Canopy arthropods were sampled by insecticide fogging to study their community structure in two New Caledonian primary rain forests. The representativeness of these samples was analysed by two different methods: the diversity-area relationship and the relationship between the distribution of the taxa and the sample size, using Pielou's method. The results showed that the higher the degree of aggregation, the higher must be the minimum sample size to ensure a stable distribution. In the same way, the higher the diversity index, the higher must be the sample size to ensure a representative sample of the community. In this study, 40 sample units of 1 m2 were used, although, samples of 9 to 25 m2 seem to be sufficient according to the distribution of the taxa sampled. Five to 30 m2 should be sufficient to ensure representative samples of the whole community for estimating diversity.

Pedodiversity: concepts and measures

Indices and models of diversity have proved to be valuable in ecology. They may be used to explore, quantify and compare the complexity of soil patterns in different areas and environments. The different ways of measuring diversity may be grouped into three classes: indices of richness, abundance distribution models, and indices based on proportional abundance of objects. Four scales of diversity can be distinguished: point scaling diversity (polypedon), a scaling diversity (soil association), y scaling diversity (landscape or drainage basin) and e scaling diversity (geographical soil region). Differentiation diversity is a measure of how different a range of soilscapes are in terms of the variety. Diversity-area relationships are then analyzed. Examples of how to apply these indices for analysing soil patterns and their results are shown. From these results it is inferred that diversity indices in the analysis of soil patterns would be similar to those for biodiversity in ecology. This suggests that there are common processes of organization of biotic and abiotic ecological structures.

Parallel trends in the species diversity of west indian birds and bats.

In this paper I compare several biogeographic patterns of West Indian resident land birds and bats, including species-area and trophic diversity-area relationships, the number of islands inhabited per species and levels of endemism, trophic structure as compared with tropical mainland areas, and the degree of faunal simlarity between islands of similar sizes but different locations. In most respects, the bat and bird patterns are strikingly similar. Groups of birds that are conspicuously missing from the Antilles because of the absence of appropriate resources also have missing chiropteran counterparts. Plant-visiting bats and birds are better-represented in terms of relative number of species and, in birds, in biomass, on the Lesser Antilles than on the mainland (e.g. Panama). Small Antillean islands tend to share more species of birds and bats than do larger islands. Stochastic (sensu Simberloff 1978), deterministic, and interactive (e.g. competitive and trophic interactions) factors appear to underly these biogeographic trends. No evidence exists to suggest that Caribbean bats and birds have negatively affected each other's diversity.