Plant species diversity in abandoned coppice forests in a temperate deciduous forest area of central Japan

We investigated plant species diversity as it related to stand structure and landscape parameters in abandoned coppice forests in a temperate, deciduous forest area of central Japan, where Fagus crenata was originally dominant. The species occurring in the study plots were classified into habitat types based on a statistical analysis of their occurrence bias in particular habitats (e.g., primary forest, coniferous plantation) in the landscape studied. The relationships between stand structure, which reflected the gradient of management, and forest floor plant species diversity (H and J) and richness (number of species per unit area) were not significant. However, these factors did influence the forest floor plant composition of the different types of habitat. According to the multiple regression analysis, species diversity and the richness of forest floor plants was affected by landscape parameters rather than by stand structure. For trees, species richness was mainly affected by the relative dominance of F. crenata, which is one of the stand structure parameters that decreases with intensive management. This is probably because many of the tree species that are characteristic of coppice forests increase after F. crenata have been eliminated by management; these species are not dominant in the original forest, where they are suppressed by F. crenata, the shade-tolerant dominant species. The species diversity (H and J) of trees was positively correlated with some landscape parameters, including the road density around the study plot, which may be associated with the intensity of management activity. The number of disturbance-tolerant species increased with increasing road density. Stand structure mainly affected disturbance-intolerant forest floor plant species and disturbance-tolerant tree species. Thus, the species diversity responses differed between forest floor plants and trees. The impact of forest management on species diversity was more prominent for forest floor plants.     

Tree species diversity of tropical forest vegetation in Xishuangbanna, SW China

Tree species diversity of four tropical forest vegetation types was investigated in Xishuangbanna, southwestern China. These are: tropical seasonal rain forest, tropical montane rain forest, evergreen broad-leaved forest and monsoon forest over limestone. A total of 17 samples were taken and four species diversity indices were calculated: Shannon-Wiener's H, the complement of Simpson's index, d, Fisher's and evenness index E. The results reveal the long-tailed rank/abundance diagrams of these forests. However, this feature is greatly reduced in the samples of monsoon forest over limestone. Tropical seasonal rain forest shows the highest tree species diversity of all four vegetation types. Owing to the variation of microenvironment, diversity values within the same vegetation type vary between the samples from different patches. The tree species diversity of single-dominant rain forest is not significantly lower than that of mixed rain forest, because the dominant species of some single-dominant rain forests are principally in the emergent layer. This is composed of sparse and huge trees of one species and, consequently, creates a unique canopy architecture and more heterogeneous microenvironments for the more diversified species composition under the emergent layer. The occurrence of tree species with small population sizes, particularly of species represented by only one individual, is highly correlated with the tree species diversity of the local forest vegetation. They are crucial elements in the richness of local biodiversity.     

Plant diversity in Lythrum,Phragmites, and Typhamarshes,Massachusetts, U.S.A.

Concern about colonization of marshesby plant species such as Phragmites australisand Lythrum salicariahas highlighted the needfor management strategies. However, there is a lack ofinformation in the literature on which to base thesedecisions. This study compares the alpha diversity ofmarshes to assess the impact of invasion by Phragmitesand Lythrum. Species occurrence andstem density were measured in marshes dominated by Phragmites, Lythrum, Typhaspp., or otherherbaceous perennials in the Charles River watershedin eastern Massachusetts, USA, and species richness,Shannon's H, Simpson's reciprocal (1/D), and Pielou'sJ were compared among six community types. The threediversity indices had significantly higher values forTypha-Lythrummarshes than for any of the othermarsh types (Tukey test, p< 0.05), with mean values(± s.d.) of H = 2.00 ± 0.74, 1/D = 3.51± 1.68 and J = 0.69 ± 0.1. Marshes dominatedby Phragmiteshad the lowest diversity, with H= 0 and D = 1, i.e. they were monospecific. Typhadominated marshes had the second lowest values,with H = 0.17 ± 0.05, 1/D = 1.05 ± 0.01, andJ = 0.11 ± 0.03. These results support the ideathat a reduction in diversity can be expected inmarshes colonized by Phragmites. However, thehigh diversity found in the Typha-Lythrummarshes contradicts the expectation of lower diversityafter invasion by Lythrum. This information mayalter marsh management decisions.     

Influence of resource abundance on the structure of the insect community attracted to fermented tree sap

There has been little or no documentation of the insect community attracted to fermented tree sap, despite our familiarity with it. This study describes the influence of resource abundance (exudate quantity) on species richness, insect abundance, and diversity at the patch level in order to elucidate the mechanisms responsible for community structure. Resource abundance was positively correlated with species richness and insect abundance, negatively correlated with the equitability index (J), and not significantly correlated with diversity (Simpsons index of diversity; 1/D). Both correlation analyses and canonical correspondence analysis based on taxonomic categories indicated that responses to resource abundance were much greater in parasitoid wasps (Ichneumonoidea), drosophilid flies (Drosophilidae), and rove beetles (Staphylinidae). Field experiments showed that patches with more of the resource had greater species richness and greater hornet abundance. These results indicate that resource abundance is an important factor that affects community structure at the patch level, although it does not influence diversity directly, due to differences in the response to a resource across subgroups; drosophilid flies, the most abundant group that was heavily dependent on tree sap, make an especially large contribution to the change in J. Various factors influence the variation in the response to resource abundance, including population size, feeding habits, and resource utilization patterns (i.e. whether the species uses patches as habitat).     

Stand structure and woody species diversity in relation to stand stratification in a subtropical evergreen broadleaf forest, Okinawa Island

Stand structure and woody species diversity in a subtropical evergreen broadleaf forest grown in a silicate habitat, Okinawa Island, have been investigated on the basis of stand stratification. The forest stand consisted of four layers. The floristic composition of the top and the lower three layers was only slightly similar, although approximately one-third of the species were common to them. Mean tree weight decreased from the top toward the bottom layer whereas tree density increased from the top downward. This trend resembled the mean weight–density trajectory of self-thinning plant populations. The relationship between mean tree height and tree density for the upper two layers supported Yamakuras quasi –1/2 power law of tree height. The values of the Shannon–Wiener index, H, and the equitability index, J, tended to increase from the top layer downward except for the bottom layer. The values of H and J were, respectively, 4.83 bit and 0.82 for trees taller than 0.10 m. The lower layers contained many species of smaller height. High species diversity of the forest depended on small trees in the lower layers. Conservation of small trees in the lower layers, especially the bottom layer, is indispensable for sound maintenance of Okinawan evergreen broadleaf forests.     

Landscape patterns and plant species diversity of forest reserves in the Kanto region, Japan

Plant species richness of twenty old-growth forest reserves in the cool-temperate zone in the Kanto region, Japan were investigated to detect the effect of forest fragmentation. The species richness of trees and forest floor plants were analyzed by multiple regression models relating to nine variables on the characteristics of landscape, local habitat and forest stand. The total species diversity did not have a significant correlation with any variables of landscape patterns. In this study, single large reserve in the SLOSS discussion did not seem very effective to preserve more species. However, forest reserves in large patches tend to have relatively infrequent species. Large patches of natural forests were regarded as one of the important factors to preserve infrequent species.     

A phytosociological analysis of woody species in forest communities of a part of Kumaun Himalaya

This paper reports on a detailed phytosociological analysis of forests in the NW catchment of the Gola River in Kumaun Himalaya, 29°19–29°27N and 79°32–79°42E. Fourteen sites and 56 stands at elevations ranging from 1200 to 2523 m and covering the following five forest types were investigated: Pinus roxburghii, mixed, Quercus leucotrichophora, Q. lanuginosa, and Q. floribunda. The basal cover of the forests differed according to slope position and aspect. The three oak forests had more basal cover than the other two, and Q. lanuginosa had the most. The performance of individual tree and shrub species and the number of saplings and seedlings differed according to slope position and aspect. The mixed forest had the greatest tree diversity, and among the others diversity increased with increasing basal cover. The diversity of trees, saplings, and herb layer was greatest on aspects with intermediate temperature and moisture conditions; whereas that of shrubs and seedlings increased towards the cooler (and wetter) and warmer (and drier) exposures. There was a positive relation between the diversity of shrubs plus seedlings and trees plus saplings in P. roxburghii and mixed forests; whereas this relationship was inverse in the three oak forests. In general, the dominance-diversity curves for the tree layer followed a geometric series conforming to the niche pre-emption situation in communities of low diversity. Among the forests, the regeneration was best in Q. lanuginosa and worst in Q. leucotrichophora.Nomenclature follows: Osmaston (1926).Finacial support from the Council of Scientific and Industrial Research, New Delhi and the Indian Space Research Organisation, Banglore is gratefully acknowledged.     

Effects of fire and selective logging on the tree species composition of lowland dipterocarp forest in East Kalimantan, Indonesia

Tree species composition (diameter at breast height (dbh) 10 cm) was studied in primary, selectively logged and heavily burnt forests in East Kalimantan, Indonesia. The number of trees, tree species, and the Fishers's- diversity index were determined for the first 15 years (burnt forest) and 25 years (selectively logged forest) after disturbance. Additionally the population structure of six common and typical Macaranga pioneer tree species was compared through time between selectively logged, burnt and primary forest. Both selectively logged and burnt forest showed a significant reduction in number of trees and tree species per surface area directly after disturbance. Fire especially affected dominant tree species, while for selective logging the opposite was observed. In selectively logged forest the number of trees, tree species and the Fishers's- index reached pre-disturbance levels within c. 15 years. For burnt forest, only the number of trees recovered to pre-disturbance levels. The number of tree species stayed constant after disturbance, while the Fishers's- index decreased. The six studied Macaranga pioneer tree species seedlings were present in all forest types. Their density seems to be unrelated to light levels in the forest understorey but strongly related to the number of mature parent trees. Their sapling densities were strongly related to light levels in the forest understorey. The studied Macaranga species formed an important part of both under- and over-storey in burnt forest 15 years after disturbance, while they were almost absent in the understorey and only moderately common in the overstorey of selectively logged forest.     

Glycerol-, inositol-, and reducing end hexose-containing oligosaccharides in human urine

Ten previously unreported oligosaccharides have been purified from the urines of human subjects using a combination of gel filtration, ion exchange, and thin-layer chromatographies. Their structures were determined by direct probe mass spectrometry, methylation analysis, and proton NMR spectroscopy of the permethylated oligosaccharide alditols.On the basis of composition, the oligosaccharides could be divided into three groups. Five oligosaccharides containing glycerol were characterized as glucosyl1-1glycerol; glucosyl1-1glycerol; galactosyl1-1glycerol; glucosyl-1-1(fucosyl-1-2)glycerol and/or fucosyl-1-1(glucosyl-1-2)glycerol; and glucosyl-1-1(galactosyl-1-2)glycerol or galactosyl-1-1(glucosyl-1-2)glycerol. Four inositol-containing oligosaccharides were characterized as galactosyl1 (fucosyl1)inositol,N-acetylgalactosaminyl1 (fucosyl1)inositol, fucosyl1-2galactosyl1 (N-acetylgalactosaminyl1)inositol and fucosyl1-2galactosyl1-4-N-acetylglucosaminyl1(N-acetylgalactosaminyl1)inositol. Finally, galactosyl1-3(fucosyl1-2)galactosyl1-6galactosyl1-4(fucosyl1-3)glucose, an oligosaccharide with glucose at its reducing end, was tentatively identified. The significance and possible origins of the carbohydrate structures are discussed.     

Gap-phase regeneration in a tropical montane forest: the effects of gap structure and bamboo species

To study the influence of gap structure and bamboo species on the regrowth of montane Atlantic forest, colonization by plants was characterized in 30 treefall gaps (30.3–500.5 m²). The study was conducted at Santa Virgínia (45°30 W, 23°17 S), a 4970-ha reserve of Atlantic montane forest in southeastern Brazil. Area covered by bamboos ranged from 0% to 100% of gap area. Average height of surrounding canopies ranged from 12 to 30 m. As gap are covered by bamboo and average height of surrounding canopies increased, both density and richness of pioneer woody species decreased. Density and richness of shade-tolerant species were negatively influenced by gap area. Low-light-demanding species of Miconia, Leandra and Rapanea accounted for the majority of both pioneer species and individuals sampled, whereas high-light demanding pioneers of Cecropia, Alchornea and Tibouchina were poorly represented. We suggest that in the Atlantic montane forest bamboo species compete for gaps, excluding other light-demanding pioneers. This results in an overall reduction of pioneer species richness in the Atlantic forest.     

Growth strategies of main trees and forest architecture of aFagus-Magnolia forest in Florida, USA

Growth strategies of six species of trees are compared and used to analyze forest architecture. They included the overstory speciesFagus grandifolia, Magnolia grandiflora, Pinus glabra andLiquidambar styraciflua, and the understory speciesOstrya virginiana andIlex opaca. The six species were abundant in Woodyard Hammock, an old-growth forest in northern Florida, USA. Height, stem diameter, crown projection and radial growth were measured in trees between 5 and 35 m tall. Three different, but non-exclusive, growth strategies were identified for the tree species: survival (Fagus grandifolia, Magnolia grandiflora, Ilex opaca), occupy open space (Fagus grandifolia, Ostrya virginiana, Ilex opaca), and reach above competitors (Liquidambar styraciflua, Pinus glabra). In two transects (0.42 ha) and one quadrat (1 ha), heights of dominant trees were used to distinguish different phases of forest development, which were mapped. In the quadrat, juvenile canopy trees in the undergrowth were mapped. The combination of presence of different developmental phases, presence of juveniles in the undergrowth, growth strategies of main tree species, and disturbance regime was used to assess forest development in the near future.Fagus grandifolia is predicted to become the main dominant species, but the frequent hurricanes open the forest canopy and provide opportunities for understory species (Ostrya virginiana andIlex opaca), and light-demanding overstory species (Liquidambar styraciflua andPinus glabra).     

Species diversities analyzed by density and cover in an early volcanic succession

To evaluate alpha diversities, various variables such as density, cover, volume, and weight have been used. However, density is often a distinct variable from the remaining three. To clarify differences in diversity measured by those two kinds of variables, the data collected in fourteen 2×5 m permanently-marked plots on Mount Usu, Japan, which erupted during 1977 and 1978 in growing seasons from 1983 to 1989 was analyzed, using Shannon's species diversity (H) that is represented as a result of combination of species richness and evenness (J). H and J were evaluated by density (density H and J) and cover (cover H and J). Cover H and J were significantly lower than density H and J, indicating that cover H has different characteristics from density H. Those differences are due to differences in evenness, because species richness is the same. The rank orders of species density are different from those of cover. The predominance of a few perennial herbs greatly decreases cover evenness, while seedling establishment success influences density evenness. Therefore, I propose that, during the early stages of succession on harsh environments such as volcanoes, density diversity represents seedling establishment success rate while cover diversity expresses vegetative reproduction success rate.     

Effects of flower and seed predators and pollinators on fruit production in two sequentially flowering congeners

We examined spatial and temporal variability of understory herbaceousvegetation on opposing north- and south-facing slopes in an eastern deciduousold-growth forest in southeastern Ohio, USA. Secondly, we explored theinfluenceof sampling scale and analytical technique on our assessment of diversitypatterns. The influence of aspect and seasonality were examined at varyingsampling scales using observed richness, evenness, andH diversity measures, non-parametric richnessestimators, species-area curves, and SHE analysis. Herb layer composition,abundance, and diversity were strongly influenced by location (north slope vs.south slope), seasonal sampling period (April, June, August), and plot size(micro (2 m²)- vs. meso (70m²)-scale samples). Although north and south plots werecompositionally distinct, they followed similar courses of change through thegrowing season. Richness, evenness, and H diversitywere generally greater on the south plot whereas herbaceous abundance wasgreater on the north plot. Species composition and diversity showed markedphenological (temporal) changes, and comparison of diversity measures at micro-and meso-scales produced markedly different results. Minimum sample areas of150–200 m² were needed to evaluate micro-scalerichness in these species rich communities, suggesting that forest understoriesmay be frequently undersampled in ecological studies. Comparison of observedandestimated meso-scale richness also suggested underestimation of richness in thenorth plot, particularly earlier in the growing season. Thus, sample size,area,and time of sampling appear critical to assessment of diversity in spatiallyandtemporally variable communities such as herbaceous forest understories.     

Occurrence and evolutionary significance of two sulfate assimilation pathways in the rhodospirillaceae

The ability to use adenosine 5-phosphosulfate (APS) or 3-phosphoadenosine 5-phosphosulfate (PAPS) as the substrate for the initial reductive step in sulfate assimilation has been tested in most of the known Rhodospirillaceae species and in some chemotrophic bacteria. Improved and optimized methods for the synthesis and purification of the sulfonucleotides APS and PAPS are described. The production of acid volatile radioactivity from ³⁵S-APS and ³⁵S-PAPS was measured under various conditions in the presence and absence of non-labeled sulfate. Specific differences in the ability to reduce APS or PAPS were observed among the Rhodospirillaceae species and also the chemotrophic bacteria. APS was found to be the substrate of the thiolsulfotransferase in Rps. acidophila, Rps. globiformis, Rm. vannielii, Rc. purpureus, R. tenue, Rps. gelatinosa, in Alcaligenes eutrophus and Pseudomonas aeruginosa. PAPS was the substrate in Rps. capsulata, Rps. sphaeroides, Rps. sulfidophila, Rps. palustris, Rps. viridis, R. rubrum, R. fulvum, in Paracoccus denitrificans and in several Enterobacteriaceae. The presence of different enzymatic systems for sulfate reduction in the Rhodospirillaceae family is compared with their taxonomical grouping and their possible phylogenetic relatedness.Nonstandard Abbreviations APS adenosine 5-phosphosulfate - PAPS 3-phosphate adenosine 5-phosphosulfate - DTE dithioerythrol - Rc. Rhodocyclus - R. Rhodospirillum - Rm. Rhodomicrobium - Rps. Rhodopseudomonas     

Colonization of gaps produced by death of bamboo clumps in a semideciduous mesophytic forest in south-eastern Brazil

The study was carried out in 16 gaps produced by bamboo clump death (Merostachys riedeliana Rupr. ex Doell) in a semideciduous mesophytic forest in the Santa Genebra County Reserve (22°4945 S and 47°0633 W), Campinas, SP, south-eastern Brazil. All shrub and tree individuals in the gap with height 0.50 m were sampled. The floristic similarity among the colonizing vegetation in these gaps and in gaps produced by treefall was assessed by the Jaccard similarity index and cluster analysis. The colonization process of these gaps was found to be similar to that in gaps formed by treefall, but this colonization only began after the bamboo clump death. The gap area varied from 35 m² to 454 m², but small gaps predominated. In the set of gaps, 3677 individuals were sampled belonging to 40 families, 83 genera and 114 species. The families with the greatest species richness in the gaps were Myrtaceae (10), Euphorbiaceae (9) and Solanaceae and Rubiaceae (8 each). The species with the greatest number of individuals in the gaps were the pioneers Celis tala Gillies ex Planchon and Croton priscus Muell. Arg. and the shade-tolerant shrubs Actinostemon klotschii (Muell. Arg.) Pax, Polygala klotzschii Chod., Psychotria hastisepala Muell. Arg. and Galipea multiflora Engl. Late secondary species predominated because of the greater number of small gaps. The gaps formed by bamboo clump death contributed to the successional and structural organization of the forest, creating suitable environments for colonization by shrub and tree species of the different successional groups.     

Seed flavonoids of thePodalyrieae andLiparieae (Fabaceae)

A study of the phenolic compounds of the closely related papilionoid tribes,Podalyrieae andLiparieae, proved that the flavonoid patterns of hydrolysed seed extracts are remarkably conservative. Butin (7, 3, 4-trihydroxyflavanone), 3-hydroxydaidzein (7, 3, 4-trihydroxyisoflavone), vicenin-2 (6, 8-di--D-glucopyranosyl-5, 7, 4-trihydroxyflavone) and orobol (5, 7, 3, 4-tetrahydroxyisoflavone) were isolated and identified as the major flavonoids. The seeds ofAmphithalea, Coelidium, Liparia, Xiphotheca, Calpurnia, Stirtonanthus andPodalyria accumulated three isoflavone O-glycosides that yielded 3-hydroxydaidzein on hydrolysis. In contrast,Virgilia contained a unique combination of vicenin-2 and orobol. Vicenin-2 was also present inCalpurnia as a major compound, butStirtonanthus insignis was the only other species studied that contained orobol (in trace amounts only). Butein, a chalcone, was reported byHarborne from the seed ofCyclopia subternata. This compound's flavanone analog, butin, was the principal component inCyclopia. A cladistic analysis, using flavonoid, alkaloid and morphological data, showed that the seed flavonoids of thePodalyrieae andLiparieae behave rather poorly as cladistic characters. They are, however, of considerable taxonomic value at the tribal level favouring the opinion that the two tribes should be combined. The apparent absence of flavonoids in the seed ofHypocalyptus supports the suggestion that it should be excluded from theLiparieae. Flavonoids also show that theArgyrolobium-group is very different from the tribeCrotalarieae and support the recent transfer of this group to the tribeGenisteae.     

Tree diversity change in remaining primary mixed-broadleaved Korean pine forest under climate change and human activities

Studying biodiversity change in existing typical ecosystems of the world under possible global climate change and local human activities is important for diversity conservation. An adapted forest dynamics model is used to simulate tree diversity change of the remaining primary mixed-broadleaved Korean pine forest (RPMKPF) in northeast China under global climate change and local human activities for the next 50 years. Human activities include logging, which removes all big trees (DBH > 50 cm), removing all individuals of each single species and all species of each functional type (shade tolerant, shade intolerant and medium type tree species). As results for RPMKPF, the index of tree diversity decreases under climate change, but it increases significantly under a combination of climate change and logging. Removing all individuals of each single species significantly affects the tree diversity of the ecosystem. After the removal of shade tolerant species, both and _c indices of tree diversity experience a significant change. The index decreases significantly under climate change when shade intolerant or medium type tree species are removed, but the _c index does not change significantly. The results of this study have implications for tree diversity management in RPMKPF under climate change and human activities.     

Relationships betweenin vitro andin vivo biotransformation of drugs in humans and animals: pharmaco-toxicological consequences

Given the crucial role played by hepatocytes in the detoxification/toxification processes of drugs, these cells have been increasingly used during the last decade in various pharmaco-toxicological areas. The majority of these studies have, however, dealt with animal cells, although examples of failures in the extrapolation of the data to man are frequent. This drawback, together with the ethical considerations in performingin vivo experiments, makes the application of the human hepatocyte model critical in the preclinical evaluation of new compounds. However, before making extensive use of these promising tools for prospective pharmaceutical research, one must ensure that they can generate data that correlate well with those obtainedin vivo. This is only possible through extensive studies on drugs showing a variety of phase I and phase II metabolic pathways in hepatocytes from different species, including man, and comparison within vivo data. Providing this validation step is undertaken, the use of such systems in drug research and development may greatly enhance the rational design of safe and effective drugs, allowing savings in time, cost and test materials as well as minimizing the use of animals.Abbreviations AMT 3-amino-3-deoxythymidine - AZT 3-azido-3-deoxythymidine - GAMT 5-glucuronyl-3-amino-3-deoxythymidine - GAZT 3-azido-3-deoxy-5-O--d-glucopyranuronosylthymidine - HIV human immunodeficiency virus - MAO monoamine oxidase     

Human impact on the forest vegetation in the western part of the Pannonic Plain (Yugoslavia)

A comparative phytosociological study was made out on two types of forest on the southern slopes of Moslavaka gora in the western part of the Pannonic Plain, Yugoslavia: acidophilic oak forest of Festuco-Quercetum petraeae Hruka 1975 and areas where Robinia pseudoacacia has been introduced by man. After cutting, the oakforest reestablishes spontaneously. Reafforestation with Robinia leads to changes irreversible in species composition and vegetational structure and prevents reestablishment of oak forest. The introduction of this allochthonous species prevents the primary wood from being restored. Forestry planting projects with a view to reducing the Robinia have so far proved ineffective.     

Presence of plastid and absence of mitochondrial DNA in male reproductive cells as evidence for cytoplasmic inheritance in Turnera ulmifolia and Zantedeschia aethiopica

Summary. Epifluorescence microscopy of mature pollen grains of Turnera ulmifolia and Zantedeschia aethiopica stained with 4,6-diamidino-2-phenylindole demonstrated the presence of fluorescent cytoplasmic DNA aggregates in the male reproductive cells of both species. Double staining of the cells with 4,6-diamidino-2-phenylindole and 3,3-dihexyloxacarbocyanine iodide in Technovit resin sections showed that the mitochondria of these cells did not correspond to the fluorescent cytoplasmic DNA aggregates. Electron microscopy studies revealed both plastids and mitochondria in the cells of these species. In addition, immunoelectron microscopy using an anti-DNA monoclonal antibody showed clear labeling of plastids but not mitochondria. These data provide cytological evidence for biparental plastid inheritance and maternal mitochondrial inheritance in these species.Correspondence and reprints: College of Life Sciences, Peking University, Beijing 100871, Peoples Republic of China.