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Evolutionary History

EVOLUTIONARY HISTORY
The earliest beetle-like insects represented in the fossil record are known from Lower Permian (270 mya) deposits in Moravia, Czech Republic, and the Ural Mountains of Russia. These insects, classified in the family Tshekardocoleidae, order Protocoleoptera, resemble present-day species of the archostematan families Ommatidae and Cupedidae. They differ from true beetles in having 13-segmented antennae, elytra with more fully developed venation and more irregular longitudinal ribbing, and an abdomen and ovipositor extending beyond the apex of the elytra.
The oldest true Coleoptera in the fossil record date back about 230 million years to the Triassic. These fossils exhibit the coleopteran 11-segmented antennae, have more regular longitudinal ribbing on the elytra, and possess internal genitalia. The earliest fossil beetle faunas have been described from Queensland in Australia, South Africa, and central Asia. All four lineages now recognized as suborders appear to have been extant by the end of the Triassic. The presumed basal suborder, Archostemata, was represented by species assignable to the extant families Ommatidae and Cupedidae, plus others belonging to families not lasting past the Mesozoic. The Triassic Adephaga included species sharing enlarged hind coxal plates such as are seen in present-day Haliplidae, as well as species attributed to Carabidae, the ground beetles, and a closely related family, Trachypachidae. Definitive myxophagans are not represented by Triassic fossils, but various lines of evidence suggest that they must have existed then. In these faunas, the currently dominant suborder Polyphaga included representatives of the extant families Staphylinidae and Elateridae. These earliest beetles inhabited a world made up of forked-leaved pteridosperms, lycopods, cycads, gingkos, and early conifers. The large animals of these communities included therapsid reptiles and dinosaurs; however, neither birds nor true mammals had yet evolved.
During the Jurassic (210-145 mya), known family-level beetle diversity increased dramatically. About 35 families and 600 species of beetles are known from this period. Among the Adephaga, first appearances are documented for the whirlygig beetle family Gyrinidae and the predaceous diving beetle family Dytiscidae. In both families, the predaceous habit would be considered to be the ancestral condition. Among Polyphaga, the major families Scarabaeidae, Tenebrionidae, and Curculionidae are first documented. Other earliest occurrences include members of the scavenging water beetles (Hydrophilidae), carrion beetles (Silphidae), jewel beetles (Buprestidae), ovoid bark-gnawing beetles (Trogossitidae), sap beetles (Nitidulidae), tumbling flower beetles (Mordellidae), false blister beetles (Oedemeridae) and three additional families representing the weevil superfamily Curculionoidea (Nemonychidae, Belidae, and Caridae). Of these, Scarabaeidae, Oedemeridae, Mordellidae, and Curculionidae are strictly phytophagous or saprophagous.
The diverse present-day assemblage of Chrysomeloidea also is thought to have appeared in the Jurassic, although definitive fossil evidence is lacking. Chrysomeloids use a broad diversity of plant hosts, ranging from cycads to conifers to angiosperms. Based on a phylo-genetic hypothesis derived from extant species, the basal chrysomel-oid lineages are associated with primitive conifers (Araucaria spp.) and cycads. Curculionoidea, the sister group to chrysomel-oids, also exhibits this ancestral association with conifers and cycads. The larvae of present-day Oedemeridae are borers in conifers. Thus it appears that at least several lineages of phytophagous Coleoptera were in place before the evolutionary advent of the angiosperms.
The Cretaceous witnessed initiation of the most recent round of southern landmass fragmentation, via the opening of the southern Atlantic Ocean and the isolation of New Zealand. South America and Antarctica plus Australia became progressively isolated from Africa, although they maintained contact with one another. Beetle families responded to this pattern of vicariance, with relictual distributions of several extant taxa supporting their origin during this time. Continuing vicariance of the southern portions of Gondwana continued into early Tertiary, with progressive isolation of Australia, and finally the separation of Antarctica and South America at the start of the Oligocene (38 mya). This last event permitted formation of the circum-Antarctic current, helping plunge the world into a latitudi-nally zonated climate similar to that of today.
Preservation of beetles in amber has provided unparalleled levels of information about extinct taxa. The deposits of Baltic amber dated at 35-50 mya, and Dominican amber dated 15-40 mya, open windows onto the transition from the tropical world of the Eocene to the climatically zonated world of today. Most often, amber fossils indicate historically broader distributions for taxa presently known from only one continent. This range contraction, continuing from the Eocene until the present day, suggests one explanation for the current latitudinal pattern of biodiversity. Many of the tropically adapted groups of organisms, of which beetles count significantly, have been progressively excluded from higher latitudes through the advent of cool to cold higher latitude climes, followed by the dramatic climatic perturbations associated with Pleistocene glaciation. G. Russell Coope goes so far as to argue that Pleistocene glaciation halted to speciation of beetles in the temperate zones most influenced by the glaciation. His argument is based on a simple fact: As he and his students studied sub-fossil beetle bits interred in wetland peats throughout various portions
 
Strict-consensus estimate of the phylogeny of Chryso-meloidea and outgroups, with host groups mapped onto the clado-gram. Numbers of synapomorphies/bootstrap values exceeding 50% shown along branches. Colors indicate major host group attributable to common ancestor of each group (green, Coniferae; mustard, Cycadales; red, dicotyledonous angiosperms; blue, monocotyledonous angiosperms; black, do not feed on living plants). Approximate ages of Mesozoic and early Tertiary fossils are only indicated where known, since almost all subfamily groups are present in the mid-Tertiary fossil record. 
of Europe and North America, they found that all species taken from deposits younger than Pliocene could be identified as currently extant. These findings contrast starkly with those from tropical island systems, where speciation may have occurred in far younger areas. In Hawaii, for example, cave-adapted carabid beetles with reduced eyes and elongate legs have evolved from fully eyed, short-legged, epigean ancestors on the younger volcanoes of East Maui and Hawaii Island, which respectively broke the ocean surface no earlier than 750,000 and 430,000 years ago. Numerous Hawaiian beetle radiations in the Carabidae, Anobiidae, Nitidulidae, Cerambycidae, and Curculionidae demonstrate the many rapid and extensive bouts of speciation that occur in newly evolving tropical island communities.
Fossil-based estimates for the origin of Coleoptera and its subgroups provide conservative, minimum ages for these events; however, phylogenetic studies utilizing molecular evolution models and dating methods by Alfried Vogler and his colleagues suggest much earlier dates. According to this work, the origin of true beetles is pushed back to about 285 mya, in the Lower Permian, and the first appearance of all four beetle suborders also is pushed back to the Permian.