Introduction

Evolutionary relatedness among various groups of organisms helps to explain community interactions in an ecosystem. There are three mechanisms that are often invoked to understand the structure of diversity within ecological communities; neutrality, competitive exclusion and abiotic filtering. In their study, Swenson et al., 2007 studied evidence for phylogenetic conservatism and spatial scale relatedness in tropical rainforest by analyzing smaller spatial scales across multiple different tropical forest communities, and eventually provided first analysis for combined influence of size and spatial scales on phylogenetic relatedness across multiple different tropical forest communities. According to Swenson et al., measures of phylogenetic dispersion of co-occurring species seem to provide reliable insights into the relative influence of biotic, abiotic and stochastic processes in structuring ecological functions. Hence, the tropical plant community structures and diversity and at which scales their processes occur is better understood. For instance, five traits (seed size, wood density, specific leaf area and leaf nitrogen and phosphorus content) in tropical trees generally considered to be important in determining tree life histories showed significant phylogenetic conservatism.

 

Discussion

Phylogenetic niche conservatism results when closely related species are more ecologically similar than expected suggesting that some process is constraining divergence among closely related species (Losos, 2008). In this process species evolve traits that are adapted to survival in a desired niche. One of the hypotheses used to explain incidence of high species richness in the tropics is the geographical area hypothesis which argues that the tropics are the largest biomes and that more area allows species to have more ranges and hence more populations. It is generally accepted that larger areas experience lower extinction rates and that larger areas are more likely to undergo allopatric speciation, which would increase rate of speciation. Larger areas therefore will result in phylogenetic divergence if this hypothesis is followed. This is because larger areas offer opportunity to species to occupy other environments other than competing for resources in a smaller environment.

 

Ecologists are however increasingly investigating the phylogenetic structure of communities to examine whether co-occurring species are more or less closely related to each other relative to species in a regional source pool (Webb et al., in press). Species that are phylgenetically closer exert stiffer competitive pressure on each other. In evolution, different species often develop functional traits to occupy a desired environment. This is referred to as trait convergence. It is a way of reducing competition or occupying a more resourceful environment. A specific niche will therefore have species that possess similar traits that enable them to survive in it. This also means that species that remain in the historical niche will maintain or develop traits that will enable them survive in that niche. Because of trait convergence, different unrelated species will occupy a niche or environment but ecological divergence of closely related species may yield similar results.

 

Many scientists have studied phylogenetic overdispersion in co-occurring species (i.e. co-occurring species being less phylogenetically related than expected by chance) and have attributed this phenomenon to competitive exclusion of closely related sympatric species, with the assumption that closely related species are ecologically similar (Losos, 2008). Another explanation could be that closely related species are ecologically divergent and that environmental filtering (in which only ecologically divergent species can exist in a site (Webb et al., 2002) is the reason distantly related, but ecologically similar species will occupy the same community (Kraft et al., 2007).

 

Phylogenetic conservatism

Phylogenetic niche conservatism can be viewed as a situation where organisms fail to adapt to conditions outside their ancestral niche. In a normal evolutionary trend, increased genetic diversity makes a population more adaptable, increasing the chance of niche expansion into previously unfavorable habitats. Genetic diversity might however also begin the process that results eventually into niche conservatism where the organism is highly specialized. Whereas it is common in matters of ecological theory to assume that species are genetically and phenotypically homogenous, evolutionary biologists assume that variation arises at every step along the way from reproduction through development. Swenson et al. in their study found that phylogenetic niche conservatism is likely widespread, indicating closely related species are more functionally similar.

 

Conclusion

Swenson et al. state that relative role of phylogenetic relatedness of species within different size classes and cohorts in structuring tropical tree communities have remained completely unexplored. Study of ancestry especially by identifying fossils (through morphological studies) is a big gamble. Morphological studies are known to be quite unreliable and unrelated species that occupy similar environments can resemble one another. Losos, 2008 (Ecology letters) observes that interpretation of patterns of phylogenetic composition of communities is not possible without actual ecological data for the constituent species. And this casts a cloud over phylogenetic studies, as Prof. Chuck Cannon, (AFEC-X lecture, 2009) observed “evolution is not optimal.”

 

 

References

Advance Field Ecology and Conservation Course (AFEC_X), 30^th July 2009, Lecture on Phylogenetics by Prof. Chuck Cannon.

 

Loso, Jonathan B., (2008) Phylogenetic niche conservation, phylogenetic signal and the relationship between phylogenetic relatedness and ecological similarity among species. Ecology letters. 11:995-1007

 

Swenson, N. G., Enquist, B. J., Thompson J. and Zimmerman, J. K. (2007). The in fluence of spatial and size scale on phylkogenetic relatedness in tropical forest communities, Ecology, 88, 1770-1780.

 

Webb, C. O., Ackerly, D. D., McPeek, M. A. and Donoghue, M. J. (2002). Phylogenetics and community ecology. Ann. Rev. Eco. Syst, 33, 475-505.

SOIL MICROBIAL AND FUNGAL DIVERSITY AMONG LAND USE HISTORIES IN XISHUANGBANNA TROPICAL BOTANICAL GARDENS(XTBG)- Peter Alele, Deng Wen, Liu Shengjie, Zhang Ming-gang

Hypothesis

l      Natural forests exhibit highest microbial and fungal diversity

l      Change of landuse of natural forests reduce soil biodiversity

Objectives

l      To determine the species richness and diversity of different bacteria and fungi in two landuse types in XTBG.

l      Use of metagenomics and enzymatic activity to study soil bacterial and fungal activity

Method

A survey of 2 different landuse histories: rubber plantation and pomelo plantation will be conducted. 3 plots of 40mX40m will be selected and established in each landuse type. 4 circular sub- plots will be established within each plot with their centers 10 meters from each side of the larger square plot (of 40mX40m). Each circular sub-plot will have a radius of 5m. Within each sub-plot, top soil and leaf-litter samples will be collected with each plot treated as a treatment block. DNA will then be extracted from the soil samples and techniques in genomics will be used to study microbial activity.

Fungal activity will be studied by examination of indicators of activity of enzymes peroxidase and phenol oxidase. These are enzymes that break down lignin and help decompose woody tissue. The primer will look for laccase gene that code for these enzymes. Presence of these enzymes indicates more fungal activity and higher rates of decomposition.

Discussions

Rubber plantations and pomelo plantations represent two types of land use that have distinct effects on soil characteristics and soil microbiology. A strong decline in soil carbon (C) occurs after repeated tillage (Schimel et al., 1985; Elliott, 1986; Burke et al., 1989; Woods, 1989; Conant et al., 2001),and this occurs in both landuse systems;  while grasslands tend to support increased soil C and microbial biomass with greater spatial heterogeneity within the soil profile than in cultivated soils (Woods, 1989; Kandeler and Murer, 1993; Caldero´n et al., 2000). Agricultural practices such as residue incorporation, cropping sequence, irrigation, and tillage alter soil microbial biomass (Anderson and Gray, 1990; Sparling et al., 1994; Franzluebbers et al., 1995) and soil microbial community composition (Bossio et al., 1998; Lundquist et al., 1999; Caldero´n et al., 2000). In some cases, cultivation history has long-term effects on microbial community structure in abandoned agricultural fields (Buckley and Schmidt, 2001), and gradients in soil fertility in either grasslands (Donnison et al., 2000; Grayston et al., 2001) or cultivated sites (Yao et al., 2000) have been shown to influence microbial community composition.

In this study, microbial diversity will be studied in soils and comparisons made between a rubber plantation and pomelo plantation. This will give us an insight into the impact of these two landuse systems on microbial diversity and fungal activity which are both strong indicators of soil health.

Workplan

Activity	Time schedule	Comments
Proposal development	4days
Presentation of proposal	July 20th
Review of proposal	July 22nd
Data collection	2days	Soil & litter samples
Data analysis	2 weeks	Includes lab work & sample analysis
Reporting and review	August 4th
Presentation	August 6th

Today the sun was bright in Xishuangbanna. We scaled heights, not on Airbuses or mountains but on tree tops.  Walking the narrow canopy passages 40 meters above the ground nearly gave me things i don’t usually have.

I wondered what the warning signs really meant. The pregnant women(or men!), mentally ill, those with high blood pressure and excessive consumers of alcohol were advised to stay away, but up there you feel like you are all of these things. As the narrow trails kept dancing to my heartbeat, i couldn’t help wondering, what if? what if? Did anybody notice how loosely knotted the ropes were? Well i now know how the Orang utans, and the other lovely cousins of mine feel high up there. How else wood i EVER have reached 40meters up a tree except as a dead soul watching over the living (Am told when you die you keep floating above the trees trying to protect your loved ones below!!)

Anyway, today i was offered another wonderful opportunity to appreciate the fact that I am a citizen of this earth and not of Mars, Neptune or any moon. This earth is beautiful and I think any clear headed person should know that this beauty is a gift to us and that we should use it wisely. If we appreciate how lucky we are to be seeing such wonders, as a tropical rain forest certainly is, then we should shoulder the responsibility of sustaining it and making sure it lasts forever.

My love to all earth citizens!!! Remember your responsibility!!!

SOIL MICROBIAL AND FUNGAL DIVERSITY AMONG LAND USE HISTORIES IN XISHUANGBANNA TROPICAL BOTANICAL GARDENS(XTBG)- Peter Alele, Deng Wen, Liu Shengjie, Zhang Ming-gang

1.1 Introduction

Since 1950, China has implemented numerous, and sometimes conflicting, policies affecting the ownership of land for both agriculture and forests (Xu and others 1999). The total area of rubber plantation in Xishuangbanna increased significantly from 6130 ha in 1963 to 136,782 ha in 1998 (Jiang 2003). Rubber has been planted after cutting natural forests. Soil microbial and fungal activity is an important indicator of soil conditions.

In all ecosystems, soil microbes play important roles in decomposition of organic matter, nutrient cycling, and plant nutrient availability (Paul and Clark, 1989). The activity and biomass of microbes respond to soil management, organic matter, and the abiotic environment, and are influenced by plant litter and rhizosphere effects (Zaady et al., 1996; Hooper and Vitousek, 1998; Jones, 1998; Caldero´n et al., 2000; Chen and Stark, 2000).

1.2 Background of study

Xishuangbanna is a biologically diverse region that covers only 0.2% of the land area of China yet contains 25% of all plant species in the entire country (Guan 1998). Over the last decades, forest cover has decreased dramatically from 63% to 34% (Yan and Chen 1992).Changes in land use and land cover are among the most important human alterations affecting the surface of the earth (Lambin and others 2001). Land-use and land-cover changes directly impact biological diversity (Sala and others 2000).

1.3 Hypothesis

l      Natural forests exhibit highest rates of microbial and fungal activity

l      Change of landuse of natural forests reduce soil biodiversity

1.4 Objectives of study

l      To determine the species richness and diversity of different bacteria and fungi in two landuse types in XTBG.

l      Use of metagenomics and enzymatic activity to study soil bacterial and fungal activity

2.0 Materials and methods

2.1 Materials

l      Tape measure

l      Ropes

l      100cm auger

l      Buckets

l      Relascope

l      Compass

l      PVC pipes

l      Plastic bags

2.2 Site description and selection

Xishuangbanna, located in southeast China province, bordering Laos and Myanmar, is a transition zone between the tropics and subtropics。Southern Yunnan has a typical monsoon climate. Mean annual temperature is 21.7°C at 550m and 15.1°C at 1979m above sea level. Annual r/fall is between 1193mm – 2491mm. More than 80% of the R/fall falls during the rainy season from May to October.

2.3 Soil sampling and analysis

A survey of 2 different landuse histories: rubber plantation and pomelo plantation will be conducted. 3 plots of 40mX40m will be selected and established in each landuse type. 4 circular sub- plots will be established within each plot with their centers 10 meters from each side of the larger square plot (of 40mX40m). Each circular sub-plot will have a radius of 5m. Within each sub-plot, top soil and leaf-litter samples will be collected with each plot treated as a treatment block. DNA will then be extracted from the soil samples and techniques in genomics will be used to study microbial activity.

Fungal activity will be studied by examination of indicators of activity of enzymes peroxidase and phenol oxidase. These are enzymes that break down lignin and help decompose woody tissue. The primer will look for laccase gene that codes for these enzymes. Presence of these enzymes indicate more fungal activity and higher rates of decomposition.

3.1 Discussions

Rubber plantations and pomelo plantations represent two types of land use that have distinct effects on soil characteristics and soil microbiology. A strong decline in soil carbon (C) occurs after repeated tillage (Schimel et al., 1985; Elliott, 1986; Burke et al., 1989; Woods, 1989; Conant et al., 2001),and this occurs in both landuse systems;  while grasslands tend to support increased soil C and microbial biomass with greater spatial heterogeneity within the soil profile than in cultivated soils (Woods, 1989; Kandeler and Murer, 1993; Caldero´n et al., 2000). Agricultural practices such as residue incorporation, cropping sequence, irrigation, and tillage alter soil microbial biomass (Anderson and Gray, 1990; Sparling et al., 1994; Franzluebbers et al., 1995) and soil microbial community composition (Bossio et al., 1998; Lundquist et al., 1999; Caldero´n et al., 2000). In some cases, cultivation history has long-term effects on microbial community structure in abandoned agricultural fields (Buckley and Schmidt, 2001), and gradients in soil fertility in either grasslands (Donnison et al., 2000; Grayston et al., 2001) or cultivated sites (Yao et al., 2000) have been shown to influence microbial community composition.

In this study, microbial diversity will be studied in soils from a rubber plantation and pomelo plantation. This will give us an insight into the impact of these two landuse systems on microbial diversity and fungal activity which are both strong indicators of soil health.

3.2Limitations

This is a study that employs techniques in isolation of DNA, use of PCR(polumerase chain reaction and DNA sequencing. Advanced lab techniques require long periods of time and rare equipment some of which may be available in Kunming. As a result, this research may take longer than expected and results may not be totally available before the end of the course.

3.3Outputs

• This study offeres an opportunity to provide insight into the consequences of landuse changes in the Xishuangbanna area.
• The study will help guide future decision making and help in choosing what landuse systems are more beneficial to the integrity of the soils and other associated natural resources

Workplan

Activity	Time schedule	Comments
Proposal development	4days
Presentation of proposal	July 20th
Review of proposal	July 22nd
Data collection	2days
Reporting and review	August 4th
Presentation	August 6th

References

Jiang, Q. N. 2003.  Actualities of Yunnan natural rubber industry, Yunnan Tropical Sciences and Technology 25:34–38.

Paul, E.A., Clark, F.E., 1989. Soil microbiology and biochemistry. Academic, San Diego, CA (273pp).

Schimel, D.S., Coleman, D.C., Horton, K.A., 1985. Soil organic matter dynamics in paired rangeland and cropland toposequences in North

Xu, J., J. Fox, L. Xing, N. Podger, S. Leisz, and A. Xihui. 1999.Effects of swidden cultivation, population growth, and state policies on land cover in Yunnan, China. Mountain Research and Development 19:123–132.