Abstract
Although the insect wing is a textbook example of morphological novelty, the origin of insect wings remains a mystery and is regarded as a chief conundrum in biology. Centuries of debates have culminated into two prominent hypotheses: the tergal origin hypothesis and the pleural origin hypothesis. However, between these two hypotheses, there is little consensus in regard to the origin tissue of the wing as well as the evolutionary route from the origin tissue to the functional flight device. Recent evolutionary developmental (evo-devo) studies have shed new light on the origin of insect wings. A key concept in these studies is “serial homology”. In this review, we discuss how the wing serial homologs identified in recent evo-devo studies have provided a new angle through which this century-old conundrum can be explored. We also review what we have learned so far from wing serial homologs and discuss what we can do to go beyond simply identifying wing serial homologs and delve further into the developmental and genetic mechanisms that have facilitated the evolution of insect wings.
Highlights
The acquisition of wings is considered a major driving force for the success of insects, yet the evolutionary origin of this important novel structure remains one of the biggest conundrums in biology
Over a century of investigations into this question have resulted in two prominent hypotheses on the evolutionary origin of insect wings: the tergal hypothesis and the pleural hypothesis
The tergal origin hypothesis proposes that wings originated from expansions of the dorsal body wall, whereas the pleural origin hypothesis essentially proposes that wings evolved from pleural tissues and their associated branches[1,2]
Summary
The acquisition of wings is considered a major driving force for the success of insects, yet the evolutionary origin of this important novel structure remains one of the biggest conundrums in biology. Another intriguing approach is to induce a “wing serial homologs-to-wing” transformation series Analyzing these transformed tissues (their morphology, development, and gene expression) may help us reconstruct an evolutionary transition series from the origin tissue to the functional wing. Similar dorsal migration of wing primordia from the lateral region has been described in the embryos of some hemimetabolous insects, such as the cockroach, Periplaneta americana[2,56] Some of these situations may partially recapitulate phylogeny; studying the development of wings and wing serial homologs in these species will be helpful to gain more information in regard to the evolutionary transitional state(s) from the origin tissue to the wing. Carinated margin: A lateral expansion of dorsal body wall (tergum) in the first thoracic segment in beetles This structure and several pleural plates have been identified as wing serial homologs[33]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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