北美蝴蝶物种多样性的统计研究

今天在学校听了来自 UC Irvine 的 [Bradford A. Hawkins 教授](http://www.faculty.uci.edu/profile.cfm?faculty_id=4562)的一个讲座。 据说Hawkins 是生物地理学和宏观生态学方面的大牛，可惜听讲前自己没有做足功课，虽然讲座是近期少见的信息量大、富启发意义的题目，却没有听得太明白。 好在回来搜论文找到了 Hawkins 等即将发表的关于同一个研究的[论文](http://dx.doi.org/10.1111/j.1365-2699.2009.02119.x)。

Hawkins 等人使用了墨西哥以北的北美地区夏季和冬季的蝴蝶物种丰度资料，将蝴蝶亚科按照分布范围分成热带和非热带两部分进行讨论。从物种丰度在纬度方向上的梯度看，热带类型的蝴蝶物种明显地表现出夏季向北迁徙或者 recolonize 的趋势；而非热带类型的蝴蝶则很少表现出有长距离的迁移。而以亚科在包括弄蝶总科 Hesperioidea 和凤蝶总科 Papilionoidea 的整个谱系树上的遗传距离（Mean Root Distance, MRD）来看，北美地区靠近热带的南部物种间的距离较短。 如果蝴蝶起源于热带的假设成立，这说明非热带物种多是适应了较寒冷气候的进化支。

根据对 8 个可能因素的回归分析，热带物种的丰度跟温度正相关，与热带地区的距离成负相关。非热带物种丰度与温度的关系更复杂一些。虽然夏季温度还是与物种丰度正相关，冬季温度较高的地区物种丰度却不一定更高。作者提出的解释是对于适应了较寒冷环境的蝴蝶物种，冬季温度有一个最适范围，高于这个范围的温度可能会扰乱休眠期的蝴蝶的生理活动，导致其数量减少甚至局部灭绝。一些对北半球气候变化造成的物种向北迁移的现象可以作为这个观点的一个注脚。

作者在文末指出形成北美蝴蝶多样性梯度的根本原因在于蝴蝶的热带起源和第三纪中期以来的长期气候变化模式。Hawkins 今天在讲座中进一步指出在欧洲、澳大利亚、智利、南非等地区也都发现了类似的梯度分布，可见他的观点具有相当强的解释力。这一研究不仅能用来解释北美现有的蝴蝶多样性梯度，也有可能被用来进一步研究蝴蝶各亚科和物种的进化和迁徙模式。这种研究方法理论上说也应该可以应用于其它起源于热带的物种，但对于蝶科的生活史、习性和物种分布的完整研究是做出这样研究的前提条件，不知道在无脊椎动物中还有哪些物种有这样完整的研究记录。

这一研究也揭示了气候变化引起的冬季温度变化将会给非热带蝴蝶物种带来的问题。从北美地区来看，热带物种可能不会仅仅因为温度上升就迁往更朝北的地区，但非热带物种聚集的地带可能会向北移动，欧洲也是如此，甚至有可能在热带和非热带物种区之间形成一个空白地带，也许会对这些地区的农业和林业产生影响。

Hawkins, B., & DeVries, P. (2009). Tropical niche conservatism and the species richness gradient of North American butterflies Journal of Biogeography DOI: 10.1111/j.1365-2699.2009.02119.x

Co-op says No to bee-killing pesticides

Guardian Environment [reports](http://www.guardian.co.uk/environment/2009/jan/28/bees-coop-pesticide): One of the big UK supermarket chains, [Co-op](http://www.co-operative.coop/), has announced in its 10-point [Plan Bee](http://www.co-operative.coop/ethicsinaction/takeaction/planbee/what-The-Co-operative-is-doing-for-bees/) that it will ban the use of 8 neonicotinoid-based pesticides on own-brand fresh products. The pesticides banned are: Acetamiprid (啶虫脒), Clothianidin (噻虫胺或可尼丁), Dinotefuran (呋虫胺或丁诺特呋喃), Fipronil (氟虫腈), Imidacloprid (吡虫啉), Nitenpyram (烯啶虫胺), Thiacloprid (噻虫啉) and Thiamethoxam (噻虫嗪或阿克泰).

It is worthy pointing out that neonicotinoid-based pesticides are considered an ideal replacement of high-toxicity pesticides and are widely used in China and many developing countries, although its harm to beehives have been noticed in China as well. It is not clear now what measures China has taken to prevent or mitigate the impact of these pesticides on its bee populations.

Sustainable energy project cause worries

Image via Wikipedia

A project aiming at utilising tidal power has caused various environmental groups to [express their worries](http://www.guardian.co.uk/environment/2009/jan/26/severn-barrage-tidal) that one of the shortlisted proposal may cause significant environment damage.

The proposal of question involves building a 10-mile barrage at [Severn Estuary](http://en.wikipedia.org/wiki/Severn_Estuary). It is a worry shared by many environmentalists that such a project may ``add to local flooding, reduce fish stocks, damage bird life and destroy the Severn bore, as well as ruin mudflats across an area of more than 77 square miles''. The environmental groups prefers a new technology called tidal lagoon, whose benefit is still not verified, and is believed to be more expensive and generate less energy. Two lagoon proposals made the shortlist.

Despite voices against the barrage proposal, it is believed that the 8 giga-watt project accounting for 5% of UK's electricity need is quite attractive to the decision makers and may well be carried out. The issue is further complicated by accusations that the cost of lagoon solutions was overestimated in the assessment.

Documents about the feasibility studies of the project can be found at the [project's government website](http://severntidalpowerconsultation.decc.gov.uk/). Today also marks the beginning of the first public consultation on the project. You can ``have your say'' after register on the website.

是否应该“为了多样性而多样性”

BBC 在今天的 Green Room 专栏中谈到了[农作物改良导致品种减少](http://news.bbc.co.uk/go/rss/-/1/hi/sci/tech/7753267.stm)的问题。由于不断增长的粮食压力，以及种植改良品种带来的经济利益，许多作物品种正在消失。作者 Jeff Bentley 的主要观点是，面对气候变化，我们需要保留作物的多样性，或许那些耐热、耐旱的作物品种是人类适应这种变化的关键。

在同一个页面上，BBC 也列出了一些读者的评论，其中一条反对意见非常有趣：

> This seems like an overblown issue. For one, if some of these crop varieties, such as O. glaberrima, are superior for a certain climate, would they not naturally outlast their alternatives in such regions anyway? It won't be mankind's cultivation that continues their existence. Furthermore, mankind has been genetically engineering crop species through artificial selection since agriculture has existed? If there is a lack of diversity, it is because mankind has settled on a very productive variety of crop, that makes the others simply not worth cultivating. I was expecting a far more compelling argument for crop diversity, like natural resistance to certain diseases (banana blight, etc.), not just diversity for diversity sake.
> _Chris C, Salt Lake City, USA_

Image via Wikipedia

这里有一个假设，就是对某种气候适应较好的物种必然会全面地淘汰那些并非为这种气候而进化或人工选择的物种。如果这个假设成立的话，物种入侵也就不会是一个如此紧迫的问题了。农业生产中原生的亚种被取代，并不是因为它们对环境的适应性比引进的亚种差（事实可能恰恰相反），而是因为它们带来的经济回报没有引进种高。而对于任何系统，过度的同质化必然带来适应能力的降低。今天大片种植同一品种的田地没有问题，并不代表将来在改变的环境条件下它们仍然没有问题。而如果原生亚种和引进亚种都不能适应变化的环境，我们最好还保留有来自其它地区的物种或亚种，能够起到替代的作用。在这个问题上任由市场做出选择，不是促进竞争和发展的方法，而是会导致农业走向垄断和衰落。从这个意义上说，为了多样性而保护多样性是必要的，我们永远不能预知，也许今天某个被遗忘的亚种，明天就是人类的救星。

幸运的是，商业动机也可以成为保护这些亚种的动力。有些马铃薯亚种已经堂而皇之地在超市里包装上市了。但是更多的作物没有这么幸运，还需要人们在它们彻底消失以前发现它们的价值。

(照片来自 Wikipedia, 由 [Gerry Manacsa](http://en.wikipedia.org/wiki/User:Gmanacsa) 拍摄，按创作共用 [Attribution-Share Alike 2.0](http://creativecommons.org/licenses/by-sa/2.0/) 许可发布。Photo by [Gerry Manacsa](http://en.wikipedia.org/wiki/User:Gmanacsa), under the CC license [by-sa 2.0](http://creativecommons.org/licenses/by-sa/2.0/))

Prioritising conservation objectives

An article in press in a recent issue of TREE proposed that triage approach should be explicitly employed in decision-making about the allocation of limited resources in conservation efforts.

Prioritising conservation objectives, in my opinion, is really not new.  All decision makers have to balance limited funding and other resources among a few (sometimes contradicting) conservation goals.  However, the author of the article argues, triage has been regarded as defeatism thinking and may lead to abandoning conservation efforts that is meaningful and has a high probability of success.  Due to the unpopular image of triage, decision makers often have to avoid mentioning triage in conservation planning explicitly.  Doing so leads to irrational policies and decisions hijacked by evaluations other than those that based on ecological and economical principles.

The author proposes that the triage process should be mentioned explicitly in planning and follow certain rules in consideration so as to achieve rational triage and optimised outcome.  The four principles should be considered are: values, biodiversity benefit, probability of success, and cost.  The latter two are not difficult to understand.  However the evaluation of values and biodiversity benefit may involve some complexities and very lively debate.

The objective function that the author proposed is the product of the first three factors divided by cost.  The resources are allocated to project that yields highest outcome in this equation.  Such an approach is straightforward.  Nevertheless, the questions that how to estimate the value of a particular species or ecosystem and how they affect local and global biodiversity have no definitive answers.  Theories such as the driver-passenger analogy may help but cannot address all the complexities in ecosystems.  Species-by-species conservation may overlook species and ecological functions that deemed not important or economically worthy of conserving.  Even the loss of a few seeming unimportant species with overlapping ecological functions in the long run may cause sudden collapse of the system by decreasing system resilience.

Thus it is necessary to examine the value of species and their biodiversity benefits from multiple perspectives.  The real benefit of making triage decision-making explicit, in my opinion, is to allow multiple stakeholder groups as well as researchers with different conservation goals to evaluate the conservation options and achieve more informed decisions.  The positive role triage approach plays therefore depends on how open and constructive the decision-making process is.