中等大小的种子具有最高的扩散适合度

        种子大小会影响啮齿动物对种子的取食及扩散,而动物对种子的选择则可能会影响种子大小的进化。传统的观点认为对于依赖啮齿动物传播的种子,大种子具有更高的扩散适合度。然而,这一观点主要是居于扩散前期阶段啮齿动物对种子大小的选择而得出的结论,因为大种子更可能被搬运及分散贮藏。居于扩散后期阶段的研究则认为小种子具有更高的扩散适合度,因为种子被贮藏后大种子更可能被挖掘及取食,小种子更可能存活而建成幼苗。在扩散阶段啮齿动物对种子大小的选择如何影响种子的扩散适合度一直存在较大分歧。

        中国科学院西双版纳热带植物园动物行为与环境变化研究组曹林等科研人员,在西双版纳地区(21°55′N, 101°16′E)研究了啮齿动物对雨林中的优势植物假海桐(Pittosporopsis kerrii)种子大小的选择,经过5年的研究,共追踪了8460粒种子的命运,发现在扩散不同阶段啮齿动物对种子大小的选择不同,甚至相反。研究发现,在扩散前期大种子更可能被搬运,因此在扩散前期阶段大种子具有较高的扩散适合度;然而,当种子被贮藏后大种子更容易被挖掘及取食,因此在扩散后期阶段小种子具有较高的扩散适合度。结合前期阶段和后期阶段的结果,发现中等大小的种子具有最高的扩散适合度。在扩散阶段,种子的存活曲线与种子大小的频率分布相似,因此在扩散阶段啮齿动物对种子大小的选择可能影响了假海桐种子大小的进化。

        该研究以 Differential foraging preferences on seed size by rodents result in higher dispersal success of medium-sized seeds 为题发表于Ecology。该研究得到了中国国家自然科学基金(3093001631301891)、国家重大基础研究项目(973项目,2007CB109102)和中国科学院西双版纳热带植物园热带雨林生态系统研究与管理开放实验室的资助。 



雏鸟排粪和亲鸟喂食之间的关系:野外观察与实验证据

  版纳植物园动物行为与环境变化研究组的权锐昌研究员等,在西双版纳地区(21°55′N, 101°16′E)研究了几种常见雀形目鸟类雏鸟的排粪与亲鸟的粪便处理行为,探讨鸟类是如何及时清理粪便、保持巢内卫生。野外调查了8个鸟种共159个巢,在育雏阶段随机进行了779次观察,没有发现巢内留有粪便。应用视频拍摄技术,野外记录了5个红耳鹎Pycnonotus jocosus)鸟巢的育雏过程,455小时的视频观察发现:几乎所有排粪都紧随在喂食之后,同一窝中的其它没有被喂食的个体从未发生排粪行为。从野外带回有雏鸟的6个红耳鹎(Pycnonotus jocosus)鸟巢进行喂食与排粪相互关系的控制实验,发现即使喂食时间间隔延长到60min120min,雏鸟依然只在喂食时才会排粪,并且单次所排的粪便重量随喂食时间间隔增加而增大。研究表明:(1)雏鸟排粪受亲鸟喂食行为的调控;(2)雏鸟较大的排粪时间弹性能有效保证其排粪发生在亲鸟喂食时,从而方便亲鸟及时处理,保证鸟巢的卫生状况。 

      该研究以The relationship between defecation and feeding in nestling birds: observational and experimental evidence 为题发表于Frontiers in zoology。该研究得到了中国国家自然科学基金(31370452)和中国科学院项目基金(KSCX2-EW-Q-17)的支持。



破碎化景观中狩猎与森林丧失对鸟类局部灭绝的影响

    狩猎强度通常会随着森林破碎化的加剧而增加,狩猎强度和森林破碎化程度都会导致物种灭绝,但是对它们的独立影响却少有探究。 

  版纳植物园动物行为与环境变化研究组硕士研究生Sreekar Rachakonda在综合保护中心Richard Corlett 研究员、权锐昌研究员等指导下,对狩猎与破碎化对鸟类的独立影响进行研究,并找出哪些特征会使某些鸟类物种在这两项压力下更加脆弱。研究的区域位于中国西双版纳州勐仑镇周边半径10公里的范围内,这个区域内的森林因人工橡胶林这种单一作物而变得高度片段化。作者编制了1954-1983年森林减少之前的鸟类记录数据,并将这些数据与2011-2014年间鸟类记录数据进行比较。作者使用乡村与矩阵校正的种面积模型(SAMs)来估量勐仑森林鸟类灭绝的观测斜率,并将该斜率与在狩猎效应不存在的情况下森林鸟类灭绝斜率做比较。同时统计了6种鸟类的生态性状, 以此找出解释鸟类灭绝可能性的最佳性状。

  本研究发现,34%的鸟类在研究区域内已经绝迹,而且乡村与矩阵校正的森林鸟类SAMs的估量斜率比无狩猎的期待值0.35分别高出1.41.7倍。研究还发现鸟类的灭绝可能性与它们的体型显著相关,而那些被认为对森林片段化非常敏感的林下食虫鸟类与食果鸟类对狩猎的敏感度却比较低。已有证据显示该研究地区在过去和现在均有狩猎活动存在,除此之外似乎缺乏其他的可能原因,研究认为狩猎增加了约1.31.6倍的森林鸟类灭绝率。本文认为在热带森林片段化景观中,狩猎效应实际上增加了物种的灭绝率,因此仅仅采取森林采伐(即扩展保护区域网络)的保护措施是不充分的。 

    相关研究结果以The use of species–area relationships to partition the effects of hunting and deforestation on bird extirpations in a fragmented landscape为题发表在国际期刊Diversity and Distributions上。 

    西双版纳勐仑1976年(上)和2010(下)景观图。 圆形部分是调查区域的历史和现状,黑色代表森林,白色代表橡胶林和人类活动区域。圆半径为10 Km 

 

The use of species–area relationships to partition the effects of hunting and deforestation on bird extirpations in a fragmented landscape

Aim Forest fragmentation is often accompanied by an increase in hunting intensity. Both factors are known drivers of species extirpations, but understanding of their independent effects is poor. Our goal was to partition the effects of hunting and fragmentation on bird species extirpations and to identify bird traits that make species more vulnerable to these two stressors.

Location Menglun, Yunnan, SW China

Methods We studied the landscape within 10 km radius of Menglun town, where forests have become highly fragmented by monoculture rubber plantations. We compiled data on birds recorded between 1954 and 1983 before forest loss and compared it with a checklist prepared between 2011 and 2014. We used countryside and matrix-calibrated species–area models (SAMs) to estimate the observed slope of forest bird extirpations in Menglun and compared it with the slope expected in the absence of hunting. We also investigated six ecological traits to determine those that best explained bird extirpation probability (EP).

Results We found that 34% of the bird fauna had been extirpated from the study landscape, and the estimated slopes of countryside and matrix-calibrated SAMs for forest birds were around 1.4 and 1.7 times higher, respectively, than the 0.35 expected without hunting. Bird EP was strongly associated with size, and understorey insectivores that are known to be susceptible to fragmentation were less susceptible to hunting than frugivores. Given evidence of past and present hunting activity in the area, and the lack of support for alternative explanations, we suggest that hunting increased forest bird extirpations by around 1.3- to 1.6-fold.

Conclusions This study highlights the importance of using species–area relationships to separate area effects from the impacts of hunting. Our results suggest that hunting substantially increases species extirpations in tropical fragmented landscapes and conservation interventions that only target deforestation will therefore be inadequate.



西双版纳地区兽类多样性监测

本研究组自2012年以来与西双版纳各个保护区开展合作,在保护区内架设红外照相机监测兽类动态,以期了解人类干扰及生境破碎化对热带生态系统的影响。

野外工作照 

       

拍摄到的动物 

           



食果鸟对果实颜色的取食顺序

自然界最常见的果实颜色是红色和黑色。尽管影响果实颜色形成的因素很多,红色和黑色常被认为与食果鸟的取食选择有关,然而这一假说仍存争议。热带亚洲有全球最丰富的食果鸟,是验证这一假说的理想区域,相关研究却很少。 

    版纳植物园动物行为与环境变化研究组的科研人员通过使用红、黑、黄、蓝、绿五种颜色的人工果实和相同颜色的自然果实,对野外捕获(有经验)的四种主要以果实为食的鸟类(红耳鹎、白喉红臀鹎、黑冠黄鹎、蓝喉拟啄木鸟)和人工饲养长大(无经验)的同种食果鸟进行取食选择实验,验证取食选择与果实颜色的相互关系。结果表明这些食果鸟对颜色有明显的取食偏好:试验中所有的食果鸟都喜好红色的人工果实;野外捕获的有经验食果鸟喜好红色和黑色自然果实;人工饲养的无经验同种食果鸟喜好黑色自然果实,之后才是红色;所有的鸟类都不喜好自然或者人工绿色果实。同时,该研究还表明该地区食果鸟的颜色选择较稳定——种内、种间差异小。基于食果鸟稳定的取食选择及其对果实颜色的选择程度与该地区自然界果实颜色的组成相似,研究认为食果鸟的取食偏好是或许是该地区果实颜色进化的驱动因素之一。 

    相关研究以Bird fruit preferences match the frequency of fruit colours in tropical Asia为题发表在Scientific Reports。研究结果被一些国外媒体报道,如Nature publish group Asia Scientist Magazinehttp://www.nature.com/srep/2014/140717/srep05627/full/srep05627.html 

 

Bird fruit preferences match the frequency of fruit colours in tropical Asia

While many factors explain the colour of fleshy fruits, it is thought that black and red fruits are common in part because frugivorous birds prefer these colours. We examined this still controversial hypothesis at a tropical Asian field site, using artificial fruits, fresh fruits, four wild-caught resident frugivorous bird species, and hand-raised nave birds from three of the same species. We demonstrate that all birds favored red artificial fruits more than yellow, blue, black and green, although the artificial black colour was found subsequently to be similar to the artificial blue colour in its spectral reflectance. Wild-caught birds preferred both black and red fleshy natural fruits, whereas hand-raised nave birds preferred black to red natural fleshy fruits and to those of other colours. All birds avoided artificial and naturally ripe green fruits. The inter-individual variation in colour choice was low and the preferences were constant over time, supporting the hypothesis that bird colour preferences are a contributing factor driving fruit colour evolution in tropical Asia.



中国西南极小雨林斑块中的鸟类多样性及其保护

生境丧失是生物多样性保护面临的最大困难,尤其是生物多样性丰富的热带地区。热带亚洲因为现存原始生境较少,却仍面临较高的森林退化率而备受关注。种植园(橡胶园,棕榈园等)替代低海拔森林是如今热带亚洲森林持续较少的主要因素之一。种植园在发展过程中产生了大量的被分割和包围的原始森林斑块,这些斑块大多分布在地势陡峭的沟边,因为难以开发而得以保存。同时这些斑块还受周边人类活动影响,其森林结构也发生了较大的改变。作为伴随人类生产活动而出现的生境类型,分布很广,但其对生物多样性的保护价值仍不清楚。 

版纳植物园动物行为与环境变化研究组的研究人员在西双版纳选择了15个被橡胶林完全分割的森林斑块进行鸟类多样性调查,结果表明:1)斑块中鸟类组成不稳定,受季节影响大,斑块面积和形状是影响鸟类多样性的主要因素;2)被橡胶林分割的单一森林斑块难以维持该区丰富的鸟类资源,但相邻的众多斑块具有互补性,整合在一起可以存活较多的鸟类物种;3)一些体型较大的鸟类,食果鸟类,以及地面食虫鸟类群等对森林片段化更为敏感。最后,基于该研究结果讨论并建议如何改善橡胶种植区生物多样性保护现状。 

    该研究成果以 Bird conservation in extremely small tropical rainforest patches in southwest China 为题发表在Biological Conservation   

研究地点和森林斑块示意 

Bird conservation in extremely small tropical rainforest patches in southwest China

Tropical forests support high levels of avian diversity but these areas have been impacted by extensive deforestation. The lowland tropical rainforest of Xishuangbanna in southwest China is one such impacted hotspot. In this region, rubber (Hevea brasiliensis) plantations have replaced most of the original forest,

but numerous small fragments of forest remain. To assess the value of these fragments to avian diversity, we classified the fifteen selected remnant forest patches into three size categories, <1 ha, 1–3 ha, and 3–6 ha, and conducted avifauna surveys. We found that 97 bird species inhabit the fragments and that bird diversity increases with patch area. The resident species composition similarity index was low among forest patches, both within and across size categories, and also low between the wet and dry seasons. Ground insectivores, frugivores and large bird species were the most vulnerable to habitat fragmentation. Our study encouragingly shows that fragments can play an important role in bird conservation in regions that now lack large tracts of natural forest; however, current patches are too small to support stable annual populations of some species, while others are more tolerant of fragmentation. We discuss these findings and provide conservation strategies to improve bird conservation within rubber plantations in southern China.



啮齿类动物埋藏种子是一多步骤决策过程

啮齿类动物的搬运与埋藏植物种子是自然界中的一个重要的生态过程。对很多植物来说,通过啮齿类动物的搬运与埋藏是植物实现种子散布的主要形式;而对啮齿类动物本身而言,也直接关乎它在未来抵御食物短缺的能力。已有的研究通常把啮齿类动物的搬运与埋藏植物种子作为一单一的过程,而啮齿类动物是如何决策实现这一复杂的过程并不知晓。动植物关系组王博博士、陈进研究员等通过一精巧的实验和模型拟合,表明啮齿类动物的搬运埋藏植物种子是一多步骤决策过程,不同的种子性状对各个步骤有着不同的影响,研究结果以Dissecting the decision making process of scatter-hoarding rodents为题在线发表于国际期刊Oikos 

    作者首先分析啮齿类动物埋藏种子的过程可能在四个环节需要决策:1)动物遇到植物种子,是忽略还是利用; 2)对于利用的种子,是就地取食还是搬运;3)对搬运的种子,要搬运多远;4)搬运后是取食还是埋藏。作者利用人工种子研究系统,探讨不同种子性状(种子大小、营养和单宁含量)对啮齿类动物埋藏过程四个步骤的影响。同时,作者引进三种可能的模型:线性模型、折线模型和抛物线模型,用三种模型检验上述三个性状对不同步骤的适合度。研究结果表明,啮齿类动物埋藏种子行为确实是一个分层决策的过程,不同种子性状对各步骤的影响不同;种子大小对上述四个步骤均有影响,而种子营养和单宁含量主要影响第一第三步骤。研究结果有助于人们更好理解啮齿类动物埋藏种子这一重要的生态过程 

决策过程

Dissecting the decision making process of scatter-hoarding rodents

Many animals scatter-hoard seeds to ensure an even supply of food throughout the year and this behavior requires similar foraging decisions. Seed-traits have been shown to affect the final foraging decision but little is known about the decision process itself. Here, we first defined four sequential steps comprising the decision process of scatter-hoarding rodents: 1) upon encountering a seed, should it be ignored or manipulated; 2) if manipulated, should it be eaten in situ or removed elsewhere; 3) upon removal, how far away should it be carried; and finally 4) whether to eat or cache the removed seed. Using experimental seeds with controlled differences in size, tannin and nutrient content, we evaluated how different traits influence each step in this decision process. We found that different traits had distinct effects on each step. Seed size affected all four steps, while nutrient and tannin content primarily affected the first and third steps. By dissecting foraging behavior in relation to experimentally controlled seed-traits, we have created an effective framework within which to understand the unique relationship between scatter-hoarding rodents that both predate and disperse plant seeds.



 

 

 

 

 

 

 

 

 

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