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2 Polish Journal of Ecology

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Species-area relationships of different plant functional groups in tropical monsoon rainforests (Hainan Island, China)

Liu W.-D., Zang R.-G., Ding Y., Zhang W.-Y.

Polish Journal of Ecology

2013

Vol. 61, nr 1

3--11

The positive relationship between the number of species in an area and the size of the habitat studied (species-area relationship, SAR) is the foundation of ecological theory and the most studied issues in ecology. However, very few studies have addressed SARs and their relationships to functional group richness and the extent of habitat area studied. We analyzed SARs in different functional groups focusing on two types of tropical monsoon rainforests on Hainan Island, China. The number of trees, shrubs, lianas, all species, deciduous species, evergreen species, thorn species, non-thorn species, simple-leaved species, and compound-leaved species were strongly related to the size of the area studied in the two tropical monsoon rainforest communities. And the size of the area studied explained over 94% of the total variations in the number of families and other groups studied. No significant differences were found for the slope of the species-area curve (Z) of different functional groups in two tropical monsoon rainforest communities except for shrubs that were taller in the Terminalia hainanensis community (TC) than in Liquidambar formosana community (LC). In the comparison of different functional groups divided by the same principle in the same tropical monsoon rainforest, no significant difference was found for the value of Z for different functional groups except that Z for lianas were higher than for shrubs in LC. However, the Z of lianas was higher than that of trees and shrubs, and evergreen species and species without thorns had higher Z values than deciduous species and species with thorns. No significant differences were found between simple-leaved species and compound-leaved species in TC. The results indicated the SARs of different plant functional groups can be well-described by the power function, although their slopes differed significantly.

Dispersal - limited biodiversity of tropical insular streams

Covich Alan P.

Polish Journal of Ecology

2006

Vol. 54, nr 4

523-547

Numerous species are adapted for colonization of insular fresh waters by using different mechanisms of active and passive dispersal, especially among oceanic islands at low latitudes. Over time, similar animal communities have assembled in many tropical streams and rivers on isolated islands. These freshwater communities are characterized by a relatively low number of species of fishes, decapods, gastropods and insects that typically have complex life cycles including passive, long-distance dispersal. These species often disperse during marine phases with drifting larvae or by rafting and aerial transport of resistant, dormant stages. Active dispersal is sometimes effective for relatively short-distance movements from one island.s streams to another island's nearby drainage basin within an archipelago (a "stepping-stones" dispersal pattern). Identifying distinct differences among aquatic communities on "true oceanic" islands of different ages and geologic histories requires a longterm biogeographic perspective including the degree of spatial isolation of populations and differences in rates of speciation. Consequently, the total biodiversity of insular streams is a complex combination of dispersal from multiple sources of species from continents and other islands, as well as evolution of new endemics. Recolonization of streams following natural disturbances and the impacts of introduced species result in dynamic changes in species accumulation and turnover in these insular freshwater ecosystems. Analysis of dispersal to islands provides general perspectives on managing fragmented habitats, especially the effects of invasive species that also shed light on factors affecting the equilibrium composition of animal communities in island-like ecosystems on continents.