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| Rice University bioscientists found that love vines attach themselves to galls, extracting energy from the nurseries at the expense of the young wasps inside. Biologists found dead, mummified wasps in almost half of the attacked galls they opened. Photo: Mattheau Comerford/Rice University |
Today we have more examples of the incompetence and sheer malevolence (if we assume intent) in biological design. This time the examples are from the world of parasites, especially the parasites that produce the many different galls found on oak trees.
The first is from the USA, involving just one of the estimated 13,000 different species of parasitic wasps that cause gall formation in plants, Belonocnema treatae. B. treatea is native to Texas and Florida. But there is a twist. This was discovered by etymologists from Rice University.
Like many other gall-forming wasps it has two generations: one sexually-reproducing with both male and female wasps; the other asexual with just parthenogenetic females, which produce the next sexual generation. The sexually-reproducing females lay eggs in the leaves of oak trees and the developing grub causes a round gall to form on the underside of the leaf.
How the gall is formed is not fully known but is believed to be caused by toxins or proteins (and possibly even a virus) which causes the oak cells to grow into a gall around the developing grub, providing both protection and nutrients. Asexual females emerge from these galls and their generation of grubs develop underground in galls on the oak trees' roots. Incidentally, this is a good example of how exactly the same DNA can produce entirely different structures under different environmental conditions.
What the Rice University group has discovered is that the leaf-gall phase of this species is also subject to parasitism, not by another wasp (which is common enough in gall wasps) but by another plant - the parasitic 'love vine', Cassytha filiformis. C. filiformis produces thin filaments that twine round plants and attach themselves via 'haustoria' to the host plant through which they extract nutrients.
Scott Egan and his colleagues at Rice University discovered that C. filiformis attaches itself to the B. treatea leaf gall and not only draws nutrients from them but also appears to kill the mature wasps inside and draw moisture from them too. They found that almost half the parasitised galls had dead and desiccated mature wasps in them while only about 2% of the non-parasitised galls contained dead wasps.
Moreover, the parasitised galls were slightly larger than average, suggesting the either the plant seeks out the larger galls - which seem unlikely - or they induce additional growth.
So we have not only the hugely complex life-cycle of this gall wasp which, as with other gall wasps, has both sexually-reproducing and asexually-reproducing generations, we have a putative designer who saw in his earlier design - oak trees - an opportunity to harm them so his 'new design', the gall-wasp, could live on something. Then, having gone to those lengths, it decided to sacrifice these gall wasps for which it had gone to all that trouble, so another of its creations - a parasitic plant - could get nutrients.
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| Knopper gall caused by A. quercuscalicis. Photo: Rosa Rubicondior | Knopper gall cut open to show A. quercuscalicis grub. Photo: Rosa Rubicondior |
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| Knopper gall showing the open pore on a 'ripe' gall. Photo: Rosa Rubicondior | On the same tree, galls of the common spangled gall wasp, Neuroterus quercusbaccarum, and (far left) galls of the related silk button gall wasp, N. numismalis. Photo: Rosa Rubicondior |
This is the knopper gall wasp, Andricus quercuscalicis. This invasive species from southern Europe only came into the UK in the 1950s and had a population explosion in 1979 that raised fears of a threat to our native, and iconic, oaks. This threat has not transpired, but in some years infestations can be so heavy that a key food supply of pigeons, jays and squirrels is made scarce.
Like the species above, A. quercuscalicis has alternate sexual and asexual generations, each producing different galls on different parts of the oak but this time, two different species of oak are involved. The sexual phase develops in small, conical galls on the male catkins of the Turkey oak, Quercus cerris; the asexual generation forms in these large spikey structures that develop from the growing acorns and their cups.
The knopper galls are sticky to touch, the sticky substance seeming to ooze from a small pore in the end which later opens to allow the mature wasp to exit the crypt. Unlike the sticky honeydew secreted by aphids which is collected by ants and which can quickly cause a tree and the grass underneath it to be covered in a sooty mould which grows on it, the sticky substance secreted by the knopper gall did not seem to be attracting ants nor growing mould. It could be that it acts as a deterrent or disinfectant of some sort.
Also on the leaves of same tree, but, like the knopper galls, absent from an adjacent Sessile oak, Quercus petraea, are the galls of yet two more gall wasps, common spangled gall wasp, Neuroterus quercusbaccarum, and the silk button gall wasp, N. numismalis. Like all the other gall wasps mentioned, these have sexual and parthenogenetic generations each of which produces characteristic galls. The former produces spherical current-like galls on the male catkins in spring; the latter parthenogenetic generation produces small, oval galls on catkins and leaf margins.
So, in these gall wasps we have the same ludicrously complex life cycles and the same 'strategy' of treating one 'creation' simply as a resource for another, and all for no apparent purpose but to produce thousands of different species of gall wasp that appear to do nothing but produce more gall wasps.
As though having alternating sexual and asexual populations, each with its own reproductive mechanism from the same genome, each species has to produce two different variations, one for each generation, of the chemical controls that cause the oaks to produce just the right gall at the right time from just the right tissues. Clearly, because these galls vary so radically, these must be subtly different to cause the same DNA to produce different galls.
It's not even obvious what this hugely complex system is for. Is the whole thing with the love vine just to produce a parasitic plant? Did this gall wasp's ancestors commit some original sin, or was that committed by the ancestors of oak trees, maybe? Why is this supposed intelligent (sic) designer apparently obsessed with producing gall wasps? Admittedly nothing on the scale of some 500,000 or more different beetles, but 13,000 different gall wasps, sometimes varying only in microscopic detail, seems just a tad obsessive.
Despite all these unanswered and seemingly unanswerable questions, creationists hold that this being the work of an omnipotent, omniscient and omnibenevolent magician is a far more logical explanation than it being the process of an undirected, amoral and utilitarian evolutionary process over many millions of years.
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