Perkovsky E.E.1, Vasilenko D.V.2 2020. Evolution of tropical termites in early Paleogene with description of a new species of Stylotermitidae (Isoptera) from Rovno amber (late Eocene of Ukraine) // Invertebrate Zoology. Vol.17. No.3: 231–246 [in English].
1 I.I. Schmalhausen Institute of Zoology, Bogdan Chmielnitski Str., 15, Kiev, 01601 Ukraine. E-mail: firstname.lastname@example.org
2 A.A. Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya Str. 123, Moscow, 117868 Russia. E-mail: email@example.com
ABSTRACT. The first Rovno amber stylotermitid Parastylotermes nathani Perkovsky sp.n. is described. It is the fourth amber stylotermitid and the second Priabonian one. Two non-Priabonian amber stylotermitids are known from the tropical Ypresian Cambay amber. In Cambay amber stylotermitids compose half of the species, and all termites with trimerous tarsi extraordinary 75% of Cambay termites. Another peculiarity of the Cambay amber isopteran community is the small body size: Cambay termites are 2.3–2.6 times smaller than Aptian Crato and Cenomanian Burmese termites and two times smaller than Ypresian Oise amber termites. The dominance of small termites with trimerous tarsi in Cambay amber is likely because of a change in the nature of predation pressure in the tropics during the earliest Cenozoic. The only known Cretaceous arboreal birds belonged to Enantiornithes (opposite birds). These opposite birds are known to have low cranial kinetism and thus would have difficulty catching small insects. At the K-Pg boundary, the extinction of Enantiornithes occurred. Concurrent with this event there was a rapid radiation of crown birds and their expansion in the low latitudes, increasing pressure from predation. The smallest (2 mm) isopteran, Nanotermes (earliest termitid), was found in Cambay amber. The strong miniaturization of the earliest termitids would be instrumental in the loss of obligate intestinal protozoa symbionts. These protists were too big become fully established in the narrow gut of small third instar of the earliest termitids. The loss of dependence on protists resulted in the loss of most larval instars in termitids and irreversible separation of neuter and sexual lines, paving the way to their ecological dominance in the tropics.
KEY WORDS. Parastylotermes nathani sp.n., Nanotermes, Enantiornithes, miniaturization, Termitidae, loss of the obligate symbiosis with intestinal protozoa, ecological domination.