Since the dawn of the biological sciences, humankind has struggled to comprehend the relationships among the major groups of “jointed-legged” animals — the arthropods. Now, a team of researchers…has finished a completely new analysis of the evolutionary relationships among the arthropods, answering many questions that defied previous attempts to unravel how these creatures were connected.
Now, for the first time, science has a solid grasp of what those relationships are, and a framework upon which to build. The new study makes a major contribution to our understanding of the nature and origins of the planet’s biodiversity.
There are millions of distinct species of arthropods, including all the insects, crustaceans, millipedes, centipedes, spiders, and a host of other animals, all united by having a hard external shell and jointed legs. They are by far the most numerous, and most diverse, of all creatures on Earth — in terms of the sheer number of species, no other group comes close. They make up perhaps 1.6 million of the estimated 1.8 to 1.9 million described species, dominating the planet in number, biomass, and diversity.
The economic aspects of arthropods are also overwhelming. From seafood industries worth billions of dollars annually to the world’s economy, to the importance of insects as pollinators of ornamental and agriculturally important crops, to the medical role played by arthropods (e.g. as disease vectors and parasites), to biological control of introduced species, to their role in every known food web, to toxicology and biopharmaceuticals, arthropods are by far the planet’s most important group of animals…
One of the most important results of this new study is support for the hypothesis that the insects evolved from a group of crustaceans. So flies, honeybees, ants, and crickets all branched off the arthropod family tree from within the lineage that gave rise to today’s crabs, shrimp, and lobsters. Another important finding is that the “Chelicerata” (a group that includes the spiders, scorpions, ticks, and mites) branched off very early, earlier than the millipedes, centipedes, crustaceans, and insects. That means that the spiders, for example, are more distantly related to the insects than many researchers previously thought.
This team approached the problem of illuminating the arthropod family tree by using genetic data (DNA sequences) obtained from 75 species carefully selected to sample the range of arthropod diversity. Many previous analyses were based on the sequences of a handful of genes. The researchers in this study, knowing the daunting diversity they faced, used DNA sequence information from as many genes as they could. In the end, they were able to apply data from 62 protein-coding genes to the problem, leading to an extremely well-supported analysis.
Key to the research was the assistance provided by the collections of the Natural History Museum of Los Angeles County. Exactly the sort of edifice the typical teabagger would probably consider useless – worth replacing with a monument to Jesse James.
Schoolchildren in the LA area are fortunate they have easy access to center not only for generalized education of the public; but, a facility with collections and staff capable of aiding scientific research.