Early Beetles

Permian 300-250mya

Wood Rot Oribatids Springtails Early modern insects

Early Beetles

The Permian period marked an important stage in the early evolution of beetles, with the emergence of primitive forms that laid the foundation for the spectacular diversification that followed in later geological periods. These early beetles, belonging to lineages like Archostemata and early Adephaga, exhibited basic adaptations that allowed them to exploit diverse habitats and ecological niches.

Beetles have wings, but do not fly round all the time remaining near the ground most of the time. They have ‘hard’ (coleo) wings to protect their hind wings for when they do take flight. 'Protocoleoptera' appeared before the Permian period, with much fossil evidence, and laid the groundwork for the diversification of beetles during this Permian and subsequent geological periods.

It is this period that beetles and woody material go back probably to the very beginnings of this group of insects. Based on fossil evidence from Europe and Central Asia, the evolutionary lineages of all of the modern Coleoptera were established in this period. They certainly radiated from the deadwood tree stumps in the earlier period to run round the earth.

The famous population biologist JBS Haldane is reputed to have said that “God had an inordinate fondness for beetles”. There are ten times as many species as there are all mammals.

His 'Primordial Soup' theory

These beetles would have played a major role in carbon recycling. The beetles would work with fungi and bacteria. The beetles relied on aerobic sources of fungi and bacteria to break down the cellulose, and help with the lignin too. The bacteria and protozoa would be working in their guts. That sounds pretty boring, but…

Xylophagous beetle gut bacteria

Lots of people are now looking at the microbial gut communities associated with the various xylophagous beetles as they “offer great potential for different biotechnologies and elaboration of novel pest management strategies…the intestinal bacterial and fungal communities..

They include Acmaeopsseptentrionis, Acanthocinusaedilis, Callidiumcoriaceum, Trichoferus campestris and Chlorophorusherbstii. The intestinal microbial communities of these Cerambycidae species were mostly represented by members of the bacterial phyla Proteobacteria and Actinobacteria and the fungal phylum Ascomycota. These wood eating beetles relied on these – predominantly aerobic bacteria and fungi”. (Mohammed et al 2018)

Protocoleoptera

Then came the beetles. Yeahyeahyeah. Beetles have hard wings and are called coleo (hard) ptera (wing). The earliest known beetles, appear at the beginning of the Permian and included members of Permocupedidae (left) which fed on decaying wood. The most diverse group of insects - beetles – originated by making the most of decaying wood, which would be abundant. The earliest holometabolous insects invaded decaying wood. This became a sort of stepping stone to living plants and soil.

It is easy to see how the first holometabolous insects would came back to earth and lived in decaying wood. The fact that the origin of beetles is in decaying wood would be the most readily available food for their offspring to grow up in. Beetles don’t fly particularly often, as their hard front wings (hence ‘coleoptera meaning hard wings) are probably more about protection than strong sustained flight. That would come later.

Wood boring

“They made distinctive galleries and tunnels in wood, first an entry hole made through bark to access underlying cambial tissue. The second phase is the engraving of an extensive, linear mother gallery and was where mating likely occurred, followed by the female beetle laying eggs singly into small, excavated niches at regular intervals along horizontal mother gallery. The larvae hatch, resulting in a series of parallel subsidiary (larval) tunnels that emerge at right angles from the mother gallery. Each tunnel underwent width expansions corresponding to larval moult growth increments deduced from coprolite size data and avoided breaches into adjacent tunnels" (Feng et al 2017)

The oldest known beetle is Coleopsis, from Germany, around 295 million years ago. Early beetles from the Permian, which are collectively grouped into the "Protocoleoptera" are thought to have been xylophagous (wood eating) and wood boring going on to have high diversity and disparity, which probably played an underappreciated role in the Permian carbon cycle. They did not just eat wood, they lived inside it. Fossil Protocoleoptera are known from the Lower Permian rocks of eastern Europe, dating back about 280 million years. The insects were flattened, probably occupied tight spaces under loose bark, resembled the modern insect order of Megaloptera (alderflies, dobsonflies, and fishflies), and likely included precursors to several modern holometabolous insect orders.

Permian beetles Zhao et al 2021

Beetles moved away from the deadwood stums to roam across soil, and found in open and quite dry terrains.

However, the ‘big’ beetle families, like scarabs, staphylinids, click beetles (Elaterids) and the ground beetles (Carabidae) we know today emerged later. The earliest fossil evidence for them dates back to the later Triassic period..

There are many extant nematodes that live in the tunnels of bark beetles and develop on fungi in the insect galleries. (Poinar Jnr 2015). Presumably they were doing it too in this period but fossils would be hard to find.

Two suborders of beetles were present in the Permian period

Adephaga: This suborder includes many well-known beetles such as ground beetles and whirligig beetles. Fossil evidence suggests that Adephaga were present during the Permian period.

Archostemata: This small suborder contains primitive beetles that are often wood-boring. Fossil records show that Archostemata were present during the Permian period. Ommatidae and Cupedidae are beetles that are considered primitive and have characteristics that suggest an early divergence within the beetle lineage

Adephaga

The Adephaga (from Greek ‘gluttonous’) are a suborder of beetles, and with more than 40,000 recorded species in 10 families, the second-largest of the four beetle suborders. Adephagans diverged from their sister and the most ‘recent common ancestor’ probably early in this period.

Dead Clade Walking

In the EPE "protocoleopteran" creatures became a ‘dead clade walking’. Most lineages became extinct. Beetle diversity did not recover to pre-extinction levels until the Middle Triassic. The end-Permian mass extinction (EPE) led to a severe terrestrial ecosystem collapse. The ecological response of insects—the most diverse group of organisms on Earth—to the EPE remains poorly understood, but the two main sub-Orders of insects emerged just after this period. The Adephaga including carabid ground beetles, are known from the Late Permian, as are members of massive suborder Polyphaga, the most diverse group of modern beetles.

The Permian xylophagous beetles suffered a severe extinction during the EPE largely due to the collapse of forest ecosystems, resulting in an Early Triassic gap of xylophagous beetles. New xylophagous beetles appeared widely in the early Middle Triassic, which is consistent with the restoration of forest ecosystems.

“Our results show that both the taxonomic diversity and morphological disparity dropped dramatically during the Early Triassic…all xylophagous stem-group beetles become extinct near the Permian-Triassic boundary or abruptly decreased in the Early Triassic (a pattern called ‘dead clade walking’), while aquatic… lineages crossed the Permian/Triassic boundary and diversified in the Middle Triassic. Coleoptera recovered…by the rise of new predatory and herbivorous groups, synchronized with the recovery of terrestrial ecosystems. However, the morphological disparity is significantly lower…due to the lack of beetles that possess complex elytra structures” (Zhao et al., 2021)

Dead clade walking means they suffer major drops in their biodiversity at a mass extinction but do not completely disappear from the fossil record. Why these groups were able to survive but not re-diversify remains a relative mystery.

Page updated

Google Sites

Report abuse