by Brian Thomas, M.S.
Gall mites are too small to see without aid, but scientists found two of them after scanning 70,000 amber droplets from Triassic beds in Italy. How much have mites evolved in the supposed 230 million years since they were entombed in amber?
Today’s 3,500 species of gall mites live on very specific plant species, and most of them subsist on angiosperms. The majority live on the outer surfaces of their host plant, but some induce plant tissue to form swollen galls in which they live and after which they are named.1
Did gall mites exist in ancient times in their present forms? If these tiny creatures evolved from some other arthropod, then fossils ought to show a continuum of transformation from that arthropod ancestor to today’s gall mites. But when scientists recently described some of the earliest gall mites from their amber-trapped and finely detailed fossils, they were surprised to find just the opposite—ancient gall mites look like modern ones.
David Grimaldi is senior author of a report in the Proceedings of the National Academy of Sciences that describes the new fossil mites.2 His group described a few minor differences between them and today’s known species. But Grimaldi said that overall, “they’re dead ringers for (modern) gall mites.”3 The technical report said basically the same thing, where the authors wrote, “there is no question as their eriophyoid lineage [gall mite] placement.”2
The researchers also described fossil traces of the plants that secreted the resin that hardened into the amber that trapped the gall mites. Although varieties of the same plant live today, this particular fossil variety is probably extinct. So, perhaps these fossil mite varieties went extinct along with the extinction of their host plant variety. And extinctions do not show evolution….
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