Integrating morphology and phylogenomics supports a terrestrial origin of insect flight

Posted 2021-02-08 djx571

1、语录

我想象着一种小型水生昆虫，它在被动的空气中学习飞行;当然不是通过研究空气动力学，而是通过反复试验。

I picture a small aquatic insect. . .which would thus learn to fly while passively air-borne; not, of
course, by studying aerodynamics, but by trial and error. —Sir Vincent Wigglesworth

 2、前言

在所有现存的动物群中，昆虫的惊人多样性使解决它们的系统发育关系成为一项艰巨的任务。昆虫的系统发育是各种宏观进化现象的支点，如翅膀飞行的进化、亲代抚育、与植物的共同物种形成以及不同喂养方式的形态特殊化等。

The phylogeny of insects is the fulcrum that underlies various macroevolutionary phenomena,such as the evolution of winged flight,
parental care, cospeciation with plants, and morphological specializations for diverse modes of feeding, to name but a few.

 然而，即使在近20年前分子系统学出现之后(1-4)，由于分子数据集的大小、有效位点的信息量和分类采样的限制，稳定的昆虫系统发育仍然难以捉摸(1-4)。在PNAS中，Wipfler等人(5)携带了一个包含3000多个基因和100多个分类单元的数据集来重新解决多新翅(总)目(Polyneoptera)昆虫的关系,即昆虫的一个分支，包括蟑螂（cockroache）、白蚁（termite）、蟋蟀（cricket）、竹节虫（walking sticks）和螳螂（praying mantises）。利用这个系统发育框架，他们推断出各种形态和生活史特征的祖先状态，并得出了一个意想不到的结论:有翅昆虫的祖先没有水生虫。

However, a stable insect phylogeny has historically remained elusive, even after the advent of molecular systematics nearly two decades ago (1–4),
owing to limitations in molecular dataset size, the informativeness of available loci, and taxonomic sampling. In PNAS, Wipfler et al. (5) bring to bear a
dataset of over 3,000 genes and over 100 taxa to resolve the relationships of Polyneoptera, a subdivision of insects that includes such groups as cockroaches,
termites, crickets, walking sticks, and praying mantises. Using this phylogenetic framework, they inferred the ancestral states of various morphological and life
history traits and came to an unexpected conclusion:The ancestor of winged insects did not have an aquatic nymph (Fig. 1)

 

需要一些背景知识来将这个推论及其含义放到上下文中。有翅亚纲 (Pterygota，the winged insects)和新翅目昆虫（Neoptera ，insects with folding wings）长期以来一直被形态学和分子系统发育分析所接受和支持，同时也被认为是昆虫翅膀飞行的单一起源（以及随后各种衍生血统中一些物种失去飞行能力）。早期基于sangor序列位点的派生子群之间关系的解密码工作遇到了障碍，从一项研究到另一项研究，这些障碍的形式是信息不足的数据分区和明显不稳定的树拓扑。

Some background is required to put this inference
and its implications into context. The monophyly of
Pterygota (the winged insects) and Neoptera (insects with folding wings) have long been accepted and supported by both morphological and molecular
phylogenetic analyses, together with the downstream
implication of a single origin of winged flight in insects
(and subsequent loss of flight in various derived
lineages [(1–4, 6), but see ref. 7]). Early efforts to decipher the relationships of derived subgroups based on Sanger-sequenced loci encountered roadblocks in
the form of insufficiently informative data partitions
and markedly unstable tree topologies from one study
to the next.