Why are there so few C2 grasses?

绝大多数植物物种利用C3光合作用。然而，一种被称为C4的光合作用的涡轮增压形式在近70个谱系中独立进化，并被我们最具生产力的食物和生物能源作物所使用。C4光合作用从祖先的C3类型通过一系列对叶片生物化学和解剖学的修改反复进化，这不可避免地在C3和C4状态之间产生进化中间体。这些C3-C4中间体使用一种称为C2光合作用的罕见生理学。C4光合作用在禾本科植物中独立进化了20多次，产生了大量的C4禾本科植物物种（约4500种）。尽管如此，只有不到10种C2草被确定。如果C2光合作用是C4创新的重要中间步骤，那么为什么C2草如此之少？也许C2草实际上很常见，但迄今为止很少有人被发现。或者，过去丰富的C2草可能已经灭绝。另一种可能性是，C4光合作用的出现可能绕过C2中间状态在一些谱系和进化通过不同的，目前未知的，进化路径。这个学生将试图找出为什么有这么少的C2草通过调查草光合多样性在生态和地理环境，以了解C4光合作用如何出现在草。要做到这一点，学生将在植物表型，野外工作，植物遗传学和公共收藏品的使用进行培训，同时在阿根廷进行野外工作，并在班戈尔大学和基尤植物标本馆进行定制培训

The vast majority of plant species use C3 photosynthesis. However, a turbo-charged form of photosynthesis called C4 evolved independently in nearly 70 lineages and is used by our most productive food and bioenergy crops. C4 photosynthesis evolved repeatedly from the ancestral C3 type via a series of modifications to leaf biochemistry and anatomy, which inevitably created evolutionary intermediates between C3 and C4 states. These C3-C4 intermediates use a rare physiology called C2 photosynthesis. C4 photosynthesis evolved independently over 20 times in the grasses, yielding a remarkable number of C4 grass species (~4500). Despite this, fewer than 10 C2 grass species have been identified. If C2 photosynthesis is an important intermediary step in C4 innovation, then why are there so few C2 grasses?Perhaps C2 grasses are actually common, but few have been identified to date. Alternatively, abundant C2 grasses of the past may have since become extinct. Another possibility is that the emergence of C4 photosynthesis may circumvent the C2 intermediate state in some lineages and evolve via different, currently unknown, evolutionary paths.This studentship will seek to identify why there are so few C2 grasses by investigating grass photosynthetic diversity within an ecological and phylogeographical context to understand how C4 photosynthesis emerged in the grasses. To do this, the student will train in plant phenotyping, fieldwork, phylogenetics, and use of public collections while undertaking fieldwork in Argentina and customized training at the University of Bangor and Kew Herbarium