Friday 3 October 2014

Another Of Those 'Absent' Transitional Forms!

Protoclaviger trichodens in Cambay amber
Parker and Grimaldi, Specialized Myrmecophily at the Ecological Dawn of Modern Ants, Current Biology (2014)
Specialized Myrmecophily at the Ecological Dawn of Modern Ants

A very nice example of one of those transitional forms from the fossil record - the very thing that, despite their abundance as I pointed out recently, creationist frauds keep assuring their victims have never been found - was published yesterday in Current Biology by paleoentomologist David Grimaldi of the American Museum of Natural History and entomologist Joseph Parker of Columbia University.

This one is a myrmecophile (literally, ant-loving) beetle (Protoclaviger trichodens) from about 52 million years ago found in Cambay amber from Indian. The myrmecophile beetles are an interesting group of parasitic beetles which have developed ways to overcome the considerable defences of an ant colony and now not only live alongside the ants where they eat ant eggs and lavae but are actively cared for by the ants and even fed and carried into the brood chambers by them. A rather nasty example, judging by human standards of morality, of a parasite taking chemical control of its host and subverting it for the needs of the parasite.

Modern ants with parasitic myrmecophile beetles.
Parker and Grimaldi, Specialized Myrmecophily at the Ecological Dawn of Modern Ants, Current Biology (2014)
One of their evolved adaptations is to exude 'appeasement compounds' from hair-like structures on their abdomens which not only switch off any aggressive instincts in the ants but cause them to treat the beetles as one of their own. A second adaptation is to have thickened exoskeletons and reduced segmentation enabling them to withstand some of the rough handling they get as the ants carry them around.

The third adaptation is reduced and modified mouthparts in the adults enabling them to be fed by the ants. Their mouthparts are little more than a syphon for sucking liquid food out of the ant's own mouth.

However, in the 52 million year-old specimen from the Cambay biota, the beetle, which in all other respects is typically parasitic myrmecophile, the mouthparts are unadapted, showing that they were still used for eating the typical prey of the rove beetles of which the myrmecophiles are a sub-group. This date is coincident with the rise of ants within the social insects of the hymenopteran order and shows that rove beetles were already adopting a parasitic lifestyle which may even have pre-dated the evolution of ants.

The specimen of P. trichodens is clearly from an early stage in this evolution and is transitional between self-sufficient predatory rove beetle and a dependant parasite. It is also from an early stage in the evolutionary radiation of ants. It was previously assumed that the myrmecophile beetles evolved after the ants had diversified but this finding suggests they co-evolved alongside them, into at least 369 different species.

© 2014 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
  • The oldest known myrmecophile is reported from Early Eocene Cambay amber from India
  • Protoclaviger is a stem group of myrmecophilous clavigerite rove beetles
  • Its transitional form captures the evolution of extreme morphological specialization
  • Molecular dating reveals Clavigeritae radiated with the Cenozoic rise of modern ants

Myrmecophiles—species that depend on ant societies—include some of the most morphologically and behaviorally specialized animals known. Remarkable adaptive characters enable these creatures to bypass fortress-like security, integrate into colony life, and exploit abundant resources and protection inside ant nests. Such innovations must result from intimate coevolution with hosts, but a scarcity of definitive fossil myrmecophiles obscures when and how this lifestyle arose. Here, we report the earliest known morphologically specialized and apparently obligate myrmecophile, in Early Eocene (∼52 million years old) Cambay amber from India. Protoclaviger trichodens gen. et sp. nov. is a stem-group member of Clavigeritae, a speciose supertribe of pselaphine rove beetles (Coleoptera: Staphylinidae) heavily modified for myrmecophily via reduced mouthparts for trophallaxis with worker ants, brush-like trichomes that exude appeasement compounds, and fusions of many body and antennal segments. Protoclaviger captures a transitional stage in the evolutionary development of this novel body plan, most evident in its still-distinct abdominal tergites. The Cambay paleobiota marks one of the first occurrences in the fossil record of a significant presence of modern ants. Protoclaviger reveals that sophisticated social parasites were nest intruders throughout, and probably before, the ascent of ants to ecological dominance, with ancient groups such as Clavigeritae primed to radiate as their hosts became increasingly ubiquitous.

© 2014 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.

Normally, parasites are bad enough for creationist frauds, who, for reasons which are probably understandable given the parasitic nature of creation pseudoscience, seem to have an aversion to discussing how they fit into their notional model of design by an intelligent, omnibenevolent designer, but here we have a double whammy - not only a parasite but one showing clear transitional features on the road which turned out to be to a parasitic form.

So, creationists, given your notional model of intelligent design by an omnibenevolent creator who made everything as is just for humans about 6000 years ago and so there are no transitional fossils showing evidence for evolution, how about explaining how you fit a 52 million year-old beetle, which is clearly in evolutionary transition into a fully parasitic lifestyle at the start of the major evolutionary radiation of the ants?

Any takers, or would you rather continue ignoring any evidence which you can't fit into your infantile magic model of the Universe?

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