群落生態(tài)學(xué)中性理論張大勇 (2)

1、群落生態(tài)學(xué)的中性理論1群落生態(tài)學(xué)的核心問(wèn)題 1、物種豐富度：為什么群落內(nèi)這么多的物種？ 2、物種均勻度：物種多度分布模式 2物種共存機(jī)制傳統(tǒng)的生態(tài)位分化的思想 熱帶雨林的物種多樣性太高，無(wú)法用傳統(tǒng)的生態(tài)位理論來(lái)解釋3不同群落物種相對(duì)多度分布模式(S型曲線(xiàn))。1. 亞馬遜潮濕的熱帶雨林。2.哥斯達(dá)黎加的熱帶干燥落葉林。3.北太平洋旋渦的海洋橈腳類(lèi)浮游生物群落。4.英國(guó)陸地鳥(niǎo)類(lèi)群落。5.巴拿馬熱帶蝙蝠群落 (Hubbell 2001)4群落中性理論的代表人物Graham BellStephen Hubbell5群落中性理論的歷史： Hubbell (1979)Science 203, 129913

2、09.局域群落（集合群落）中的物種多樣性取決于物種滅絕和新物種遷入（形成）之間的動(dòng)態(tài)平衡6The Unified Neutral Theory of Biodiversity and Biogeography. Stephen P. Hubbell, Princeton University Press: 2001. 448 pp.群落中性理論的歷史： Hubbell(2001)局域群落通過(guò)遷移與集合群落相連接7Hubbell的著作引起巨大反響EvolutionTREENatureScience8群落中性理論 2個(gè)基本假設(shè)：1、群落由同一營(yíng)養(yǎng)級(jí)的物種組成，群落的大小不變。2、所有的個(gè)體（不管屬

3、于哪個(gè)物種）在生態(tài)學(xué)上是相同的，或者說(shuō)對(duì)稱(chēng)的：具有相同的出生、死亡、遷移以及新物種形成的概率 預(yù)測(cè)：集合群落在點(diǎn)突變形成新物種（速率v）的模式下其相對(duì)豐富度服從漸近對(duì)數(shù)級(jí)數(shù)分布；而受擴(kuò)散限制的局域群落以及以隨機(jī)分裂為新物種形成模式下的集合群落則服從零和多項(xiàng)式分布 參數(shù)：集合群落（JM, ) 局域群落(J, , m), 2JMv稱(chēng)為 fundamental biodiversity number9中性模型在大小為J的局域群落中，種i增加一個(gè)個(gè)體，種j減少一個(gè)個(gè)體的概率為：相對(duì)物種豐富度不變的概率為 大小為J的局域群落中按多度排序后物種的期望多度為： 10二、Preston（1948）：對(duì)數(shù)正態(tài)分

4、布（lognormal distribution)一、Fisher（1943）：對(duì)數(shù)級(jí)數(shù)分布（logarithmic distribution)J個(gè)個(gè)體的樣本中個(gè)體數(shù)為n的物種數(shù) 物種多度的分布格局中性模型調(diào)和了經(jīng)典的對(duì)數(shù)級(jí)數(shù)和對(duì)數(shù)正態(tài)分布之間的爭(zhēng)論， 即Fisher的對(duì)數(shù)級(jí)數(shù)分布是集合群落的抽樣分布；而Preston的對(duì)數(shù)正態(tài)分布描述的是局域群落的物種相對(duì)多度分布11中性模型與實(shí)測(cè)數(shù)據(jù)擬合非常好中性模型對(duì)沙撈越Lambir山地國(guó)家公園內(nèi)熱帶樹(shù)種群落優(yōu)勢(shì)度-多樣性曲線(xiàn)的擬合。點(diǎn)虛線(xiàn)是= 310且沒(méi)有擴(kuò)散限制（m=1）的集合群落最佳擬合。52公頃樣地的樹(shù)木群落的相對(duì)豐富度數(shù)據(jù)的最佳擬合是 = 3

5、10 和 m = 0.15。粗線(xiàn)是觀測(cè)到的優(yōu)勢(shì)度-多樣性曲線(xiàn)。中性模型對(duì)實(shí)測(cè)數(shù)據(jù)的1197個(gè)種擬合得非常好(r2 = 0.996)（Hubbell 2006） 12中性理論的意義1、包含了傳統(tǒng)生態(tài)位理論所忽略的成分，特別強(qiáng)調(diào)了隨機(jī)性的重要作用2、把發(fā)生在局域尺度上的生態(tài)學(xué)過(guò)程和發(fā)生在區(qū)域尺度上的進(jìn)化和生物地理學(xué)過(guò)程（如物種分化、親緣地理學(xué)）有機(jī)地聯(lián)系在一起3、它至少提供了一個(gè)不同時(shí)空尺度上群落動(dòng)態(tài)的零假設(shè)13 Nature 424:1035-1037；得到了中性模型的解析解群落中性理論的進(jìn)展（forward in time） Volkov et al. (2003)集合群落（服從Fisher-

6、a分布）：局域群落：其中14群落中性理論的進(jìn)展（backword in time) Etienne & Olff 2004a,b; Etinne 2005 a,b 在大小為J的群落中，S個(gè)物種的多度分別為n1, n2, nS的概率為m =I/(I+J-1) 15群落中性理論的進(jìn)展 Hubbell (2006，Ecology)以BCI為例，一棵樹(shù)的20個(gè)近鄰中平均有14個(gè)不同的樹(shù)種，而兩個(gè)同一物種的不同個(gè)體的20個(gè)近鄰中平均只有4個(gè)物種相同（Hubbell & Foster 1986a）。在這樣的群落中，有方向的進(jìn)化不大可能會(huì)發(fā)生，使得形成生態(tài)位分化。占總數(shù)3/4的耐蔭樹(shù)種的進(jìn)化歷史中，陰暗的生

7、境比陽(yáng)光充足的生境豐富，因此大多數(shù)物種的生活史向著有利于在陰暗生境生存和生長(zhǎng)進(jìn)化，而不管有多少物種采取了相同的進(jìn)化路線(xiàn)。16Zhang 和Lin (1997) 以及Yu等（1998）先后在中性模型的基礎(chǔ)上假定物種間出生率或死亡率有微小差異。他們發(fā)現(xiàn)物種的共存時(shí)間將急劇下降，群落很快被競(jìng)爭(zhēng)強(qiáng)者（出生率高或死亡率低）所替代。說(shuō)明個(gè)體在生態(tài)學(xué)上對(duì)稱(chēng)的假設(shè)對(duì)于中性理論至關(guān)重要，同時(shí)說(shuō)明中性理論從這個(gè)角度來(lái)說(shuō)是脆弱的中性理論的假設(shè)：理論檢驗(yàn)17中性理論的假設(shè)：BCI野外數(shù)據(jù)檢驗(yàn)一方面，如果群落的多樣性和穩(wěn)定性正相關(guān)，則豐富度高的區(qū)域物種替換率應(yīng)該較低；另一方面，多樣性高的區(qū)域從時(shí)間上來(lái)說(shuō)變化小。但BCI

8、 的數(shù)據(jù)并不支持上述假設(shè)。另外，Hubbell（2006)以BCI為例間接說(shuō)明了物種豐富度和生產(chǎn)力之間不存在正相關(guān)關(guān)系。 在中性群落中，增加多樣性不會(huì)增加群落的穩(wěn)定性或生產(chǎn)力18中性理論的假設(shè)：BCI野外數(shù)據(jù)檢驗(yàn)19 從1990-1995年對(duì)胸經(jīng)在10cm以上的63個(gè)個(gè)體數(shù)大于50的樹(shù)種的調(diào)查結(jié)果表明，樹(shù)種每年的死亡率在0.44%到16.4%之間變化，而替代率在0.34%到12.0%之間變化（Condit et al. 1995, Sheil et al. 2000）。Chave(2004)為檢驗(yàn)有多少物種偏離群落的平均替代率和死亡率計(jì)算了標(biāo)準(zhǔn)差，并對(duì)每個(gè)物種進(jìn)行了t檢驗(yàn)。結(jié)果表明，在63個(gè)種

9、中只有26個(gè)種（占41%）符合中性的假設(shè)。也就是說(shuō)，大多數(shù)的物種是非中性的。中性理論的假設(shè)：BCI野外數(shù)據(jù)檢驗(yàn)20檢驗(yàn)中性理論預(yù)測(cè)（Hubbell 1997)ZSM預(yù)測(cè)能精確擬合實(shí)際數(shù)據(jù)21檢驗(yàn)的中性理論預(yù)測(cè)（McGill 2003)對(duì)數(shù)正態(tài)分布優(yōu)于ZSM分布22檢驗(yàn)中性理論預(yù)測(cè)（Volkov et al. 2003)中性模型的解析解比對(duì)數(shù)正態(tài)分布擬合效果好23Allee效應(yīng)與群落中性理論模型：集合群落Jm =10,000,000 =50局域群落J =10,000種i的單位出生率因子為wi= Ni/(Ni+) 表示Allee效應(yīng)， Ni為局域群落中種i的個(gè)體數(shù)Step 1: 隨機(jī)死亡一個(gè)個(gè)體S

10、tep 2: 以概率m來(lái)自于集合群落的一個(gè)個(gè)體占領(lǐng)空斑 ，否則新補(bǔ)充的個(gè)體為局域群落原有個(gè)體的后代，它屬于種i的概率為Allee效應(yīng)對(duì)物種豐富度和物種-相對(duì)多度分布格局的影響2425Allee效應(yīng)與群落中性理論Step 1: kill an individual. Select a cell randomly and let the cell become empty. Decrease the abundance of the corresponding species by one.Step 2: Recruit an individual. Count the number of ind

11、ividuals of each species within the dispersal distance of the empty cell; denote them as n1 and n2 for species 1 and species 2 respectively. The probability that an individual of species 1 is recruited is w1n1/(w1n1+w2n2), where wi= Ni/(Ni+); Ni is the total number of individuals of species i in the

12、 system and denotes the intensity of the Allee effect. Here we assume mating takes place on a global scale. The probability that species 2 occupies the empty cell is w2n2/(w1n1+w2n2).Repeat step 1 and step 2 for D times, and then increase the absolute time by one.The above process is repeated until

13、extinction or complete dominance is reached. Then record the time to fixation. Do the above algorithm 200 times and a MTF will be given as the average.Allee效應(yīng)對(duì)物種共存時(shí)間的影響2627近中性模型出生率差異對(duì)物種共存時(shí)間的影響Step 1: kill an individual. Choose a cell randomly and kill the individual on the cell, and then decrease th

14、e abundance of the corresponding species by one. Step 2: Establish an individual. Count the number of individuals of each species within a radius r of the empty cell; denote them as n1 and n2 for species 1 and species 2 respectively. The probability that an individual of species 1 is recruited is n1

15、*w/(n1*w+n2), where w denotes the per capita fecundity factor of species 1 relative to species 2. The fecundity rate will be the same when w equals 1, which is the case of neutral community drift model. The probability that species 2 occupies the empty cell is s2 /(s1*w+s2).Repeat step 1 and step 2

16、for D times, and then increase the absolute time by one.The above process is repeated until extinction or complete dominance is reached. Then record the time to fixation. Do the above algorithm 100 times and a MTF will be given as the average. 模型：28Fig.1 The influences of interspecific differences i

17、n fecundity and dispersal pattern on the time to fixation (MTF). MTF decreases dramatically as w and community size increase. 29Fig.2 The influences of community size, dispersal distance and the interspecific differences in fecundity on the MTF. The MTF increases proportionally as the community size

18、 increases, and dramatic increases in MTF with community size only occur in the neutral drift case. Increases in MTF due to dispersal limitation are moderate. 30模型：集合群落Jm =1,000,000 =50種i的出生率因子為biN(1, 2 ) 分別取0，0.001，0.005，0.01種間差異對(duì)物種豐富度和物種-相對(duì)多度分布格局的影響集合群落概率：近中性模型31Fig.3 Metacommunity equilibrium ran

19、k-abundance curves and equilibrium species-abundance distributions of the neutral drift model with and without differences in species fecundity. Parameter values: Jm=1,000,000, =50. 32Fig.4. The relationship between species relative fecundity factor and species rank in abundance as fecundity differe

20、nce is introduced into the neutral model of metacommunity. 33模型：Step 1: 隨機(jī)死亡一個(gè)個(gè)體Step 2: 以概率m來(lái)自于集合群落的一個(gè)個(gè)體占領(lǐng)空斑 ，否則新補(bǔ)充的個(gè)體為局域群落原有個(gè)體的后代，它屬于種i的概率為近中性模型出生率差異對(duì)物種豐富度和物種-相對(duì)多度分布格局的影響一局域群落局域群落J =10,000 種i的出生率因子為biN(1, 2 ) 分別取0，0.001，0.005，0.01，遷移率m=0.001, 0.01, 0.1, 0.534Local community equilibrium rank-abundan

21、ce curves of the neutral drift model with and without differences in species fecundity and with different dispersal rates. Other parameter values: J=1,000, =50. 35Local community equilibrium species-abundance distributions for the neutral drift model with and without the differences in fecundity and with different dispersal rates. Oth