Community phylogenetic analysis is an effective approach to understanding the process of community formation. The phylogenetic tree of the species pool is reconstructed in the first step, and the ...phylogenetic tree obtained in the second step is used to analyze phylogenetic diversity. Sythetic trees have often been used in the construction of phylogenentic trees; however, in tropical rainforests with many closely related species, synthetic trees contain many unresolved nodes, which may affect the results of phylogenetic structure analysis. Here, we constructed a phylogenetic tree using DNA barcode sequences (rbcL, matK, trnH‐psbA) for 737 tree species from the rainforests of Borneo, which have a high‐species diversity and many closely related species. The phylogenetic tree had fewer polytomies and more branch length variations than the Phylocom synthetic trees. Comparison of community phylogenetic analyses indicated that values of the standardized effect size of mean pairwise distance (SES–MPD) were highly correlated between Phylocom and DNA barcode trees, but less so for the standardized effect size of mean nearest taxon distance (SES–MNTD), suggesting that caution is needed when using synthetic trees for communities containing many congeneric species, especially when using SES–MNTD. Simulation analysis suggested that spatial dependence on phylogenetic diversity is related to the phylogenetic signal of the species' habitat niche and the spatial structure of habitat, indicating the importance of detailed phylogeny in understanding community assembly processes.
We determined DNA barcode sequences of 737 tree species in the Borneo rainforest, which has a high species diversity with many closely related species. Comparative analysis of community phylogeny suggested that caution should be exercised in the use of synthetic phylogenetic trees constructed with Phylocom and other tools for highly diverse forests. Simulation analysis was also conducted to demonstrate the significance of DNA barcode phylogeny in the study of community assembly processes.
The effects of El Niño-induced droughts on dipterocarp forests must be quantified to evaluate the implications of future global climatic changes for the tropical forests of Southeast Asia. We studied ...the mortality of trees ≥ 1 cm in diameter in a lowland dipterocarp forest in Borneo before, during, and after the 1997/1998 El Niño drought. The annual mortality rates were 1.30, 1.75, and 1.66 percent/yr for the pre-drought, drought, and post-drought periods, respectively. The effect of drought was tree size-dependent being greater for larger trees. Modified logistic regression analysis revealed a significant interaction effect between species' habitat association and edaphic condition on mortality rates in all periods. For species associated with wet habitat, drought effect was greater in dry conditions than in wet conditions, in both the drought and post-drought periods. The mortality rates of dry-habitat species were less affected by the drought both in dry and wet conditions. A similar pattern was also found in common Dipterocarpaceae species; mortality rates increased more in species associated with wet-habitat in the drought and post-drought periods. Species and families with higher mortality in the pre-drought period tended to experience greater mortality increases during the drought and post-drought periods. These results suggest that changes in drought regimes alter the species composition and spatial distribution of dipterocarp forests.
Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. ...One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (≥ 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.
Habitat difference is an important mechanism for maintenance of tree diversity in tropical forests. The first step in studies of habitat difference is to statistically analyze whether the spatial ...distributions of tree populations are skewed to species-specific habitats; this is called a habitat association test. We propose a novel habitat association test on the basis of the probability of tree occurrence along a continuous habitat variable. The test uses torus shift simulations to obtain a statistical significance level. We applied this test to 55 common dipterocarp species in a 52-ha plot of a Bornean forest to assess habitat associations along an elevation gradient. The results were compared to those of three existing habitat association tests using the same torus shift simulations. The results were considerably different from one another. In particular, the results of two existing tests using discrete habitat variables varied with differences in habitat definitions, specifically, differences in elevation break points, and the number of habitat classes. Thus, definitions of habitats must be taken into account when habitat association tests with discrete habitat variables are used. Analyses of artificial populations independent of habitat showed that all of the tests used were robust with respect to spatial autocorrelation in tree distributions, although one existing test had a higher risk of Type I errors, probably due to the use of multiple tests of significance. Power analysis of artificial populations in which distributions were skewed to certain elevations showed that the novel test had comparable statistical power to the most powerful existing test. Statistical power was affected not by the total number of a given tree but by the number of clumps in a plot, suggesting that >5 clumps were required for a reliable result.
Fine-scale spatial genetic structure is increasingly recognized as an important factor in the studies of tropical forest trees as it influences genetic diversity of local populations. The biologic ...mechanisms that generate fine-scale spatial genetic structure are not fully understood. We studied fine-scale spatial genetic structure in ten coexisting dipterocarp tree species in a Bornean rain forest using microsatellite markers. Six of the ten species showed statistically significant fine-scale spatial genetic structure. Fine-scale spatial genetic structure was stronger at smaller spatial scales (≤ 100 m) than at larger spatial scales (> 100 m) for each species. Multiple regression analysis suggested that seed dispersal distance was important at the smaller spatial scale. At the larger scale (> 100 m) and over the entire sample range (0—1000 m), pollinators and spatial distribution of adult trees were more important determinants of fine-scale spatial genetic structure. Fine-scale spatial genetic structure was stronger in species pollinated by less mobile small beetles than in species pollinated by the more mobile giant honeybee (Apis dorsata). It was also stronger in species where adult tree distributions were more clumped. The hypothesized mechanisms underlying the negative correlation between clump size and fine-scale spatial genetic structure were a large overlap among seed shadows and genetic drift within clumped species.
The resource allocation for vegetative growth and female reproduction in three tree species of subgenus Cyclobalanopsis (Quercus, Fagaceae), i.e., Q. salicina, Q. sessilifolia, and Q. acuta, were ...examined on a per-individual basis in two consecutive reproductive seasons, in order to test whether these trees fit the predictions of the masting hypotheses about resource matching versus resource switching. Since the three Quercus species have a biennial fruiting habit, it takes 3 years for the observation of two reproductive events. Female flower and acorn production per tree were investigated by using a seed-trap method and a numerical analysis of seed dispersal. The net production of each individual was estimated as the sum of the annual increase in the dry mass of vegetative organs and reproductive investment per tree. In the data analyses, the three species were pooled, since all 12 sample trees of the subgenus apparently showed masting in the same year, with no exceptions. Female flower and acorn production per individual tree changed considerably between years. The net production per tree increased with tree size, but did not differ between years. Therefore, the reproductive allocation (proportion of a plant's annual assimilated resources which are used for reproduction) differed dramatically between years. On the other hand, within a year, the reproductive allocation increased with increasing net production per tree. These results suggest that the switching of resource allocation between years within an individual are occurring in subgenus Cyclobalanopsis species, and the intensity of the switching increases with increasing tree size.
Mass Fruiting in Borneo: A Missed Opportunity KETTLE, CHRIS J.; GHAZOUL, JABOURY; ASHTON, PETER S. ...
Science (American Association for the Advancement of Science),
10/2010, Letnik:
330, Številka:
6004
Journal Article
Tropical tree wood density is often related to other species-specific functional traits, e.g. size, growth rate and mortality. We would therefore expect significant associations within tropical ...forests between the spatial distributions of stand-level wood density and micro-environments when interspecific variation in wood density is larger than intraspecific variation and when habitat-based species assembly is important in the forest. In this study, we used wood cores collected from 515 trees of 72 species in a 15-ha plot in northern Thailand to analyse intra- and interspecific variation in wood density and the spatial association of stand-level wood density. Intraspecific variation was lower than interspecific variation (20% vs. 80% of the total variation), indicating that species-specific differences in wood density, rather than phenotypic plasticity, are the major source of variation in wood density at the study site. Wood density of individual species was significantly negatively related to maximum diameter, growth rate of sapling diameter and mortality of saplings. Stand-level mean wood density was significantly negatively related to elevation, slope convexity, sapling growth rate and sapling mortality, and positively related to slope inclination. East-facing slopes had significantly lower stand-level mean wood densities than west-facing slopes. We hypothesized that ridges and east-facing slopes in the study forest experience strong and frequent wind disturbance, and that this severe impact may lead to faster stand turnover, creating conditions that favour fast-growing species with low wood density.
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Questions: 1. Are trees in a Bornean tropical rain forest associated with a particular habitat? 2. Does the strength of habitat association with the species‐specific optimal habitat increase with ...tree size?
Location: A 52‐ha plot in a mixed dipterocarp forest in a heterogeneous landscape at the Lambir Hills National Park, Sarawak, East Malaysia.
Methods: Ten species from the Sterculiaceae were chosen as representative of all species in the plot, on the assumption that competition among closely related species is more stringent than that among more distantly related taxa. Their habitat associations were tested using data from a 52‐ha plot by a torus‐translation test.
Results: The torus‐translation test showed that eight out of the ten species examined had significant association with at least one habitat. We could not find negative species‐habitat associations for rare species, probably due to their small sample sizes. Among four species small trees were less strongly associated with habitat than large trees, implying competitive exclusion of trees in suboptimal habitats. The other four species showed the opposite pattern, possibly owing to the smaller sample size of large trees. A habitat had a maximum of three species with which it was significantly positively associated.
Conclusions: For a species to survive in population equilibrium in a landscape, habitats in which ‘source’ subpopulations can be sustained without subsidy from adjacent habitats are essential. Competition is most severe among related species whose source subpopulations share the same habitat. On the evidence of source subpopulations identified by positive species‐habitat association, species‐habitat association reduces the number of confamilial competitors. Our results therefore indicate that edaphic niche specialization contributes to coexistence of species of Sterculiaceae in the plot, consistent with the expectations of equilibrium hypotheses.
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