Concerning hobbits and NZ grass grub

Lord of the Rings book   I’ve suggested before that The Lord of the Rings by JRR Tolkien is a great way to prepare a young person for a career in biogeography. I would go further and suggest that The Lord of the Rings is a great way to prepare someone for ecology and evolution full stop. I have read the book seven times since my uncle gave me a battered copy in 1979 when I was 12. Growing up in New Zealand meant that the images that I constructed of the LotR landscapes were remarkably similar to that of the movies (although my Shire looked more like the larger rolling hills of South Otago than those of the northern Waikato). I have just read the book again and find it just as enthralling as previously. I also find that as I age, I find different characters and sections of the books more or less compelling than in the past. For example, although younger Adrian enjoyed the travels of Sam and Frodo after the breaking or the fellowship, I used to think it was a little slow. Now I find that I enjoy this part of the books more that the daring-do of what happens to Pippin, Aragorn, Gimli and the rest of the gang. My previous read through was in 2007 and I have since lived through a natural disaster  (the Canterbury quakes). Maybe I sympathise more with the personal change and growth that Sam, in particular, goes through in response to the stress and tragedy of his journey. Last time I read the LotR with a biogeographer’s eye, noticing the deep history, the landscapes and distributions. This time I read the LotR with more awareness of the ecology, noticing the interactions, the descriptions of habitats, the effects of change, even the climate change effects! One of the things that struck me is that the concept of environment and experience interacting with inherited traits to determine the expression of everything from the plants of the Morgul Vale to how the hobbits put right the Shire when they return. Merry, Pippin, Sam and Frodo are able to rally the Shire on their return to expel Saruman and his occupying forces not because they are genetically superior to other hobbits but because of the experiences that they have been through that have changed their behaviour compared to the rest of the Shire hobbits.

deer heights 11
“One does not simply walk into Mordor”. Unless you are in New Zealand, and then you can even take your kids.

Take this passage from when Sam and Frodo finally enter Mordor. “And here things still grew, harsh, twisted, bitter, struggling for life. In the glens of the Morgai on the other side of the valley low scrubby trees lurked and clung, coarse grey grass-tussocks fought with the stones, and withered mosses crawled on them; and everywhere great writhing, tangled brambles sprawled. Some had long stabbing thorns, some hooked barbs that rent like knives. The sullen shrivelled leaves of a past year hung on them, grating and rattling in the sad airs, but their maggot-ridden buds were only just opening. Flies, dun or grey, or black, marked like orcs with a red eye-shaped blotch, buzzed and stung; and above the briar-thickets clouds of hungry midges danced and reeled.” This reads like a slightly grimmer version of Darwin’s ‘tangled bank’ paragraph from the Origin and similarly it conveys how life adapts to any situation.

A large part of what ecologists and evolutionary biologists do is to look at how populations adapt to changes in the environment. The plants of Mordor have adapted to living in an environment that was once benign to the harshness created by the proximity of a large active volcano and a dark lord. New Zealand, despite what you might see in the LotR movies, is for the most part highly changed from what it once was, although only parts are Mordor-like. Since humans have arrived much of the country has been converted from native vegetation to exotic pasture on which we graze our sheep and dairy cows. The stories of invasive species establishing in New Zealand are numerous, most sharing a similarly grim ending, usually at the cost of native species and the local environment. One story with a twist is that of the native scarab beetle species, Costelytra zealandica, which has colonized the introduced pastures, causing so much grief that it has earned itself the name New Zealand grass grab and a reputation as a pest species. The larvae of Costelytra zealandica feed on the roots of white clover and ryegrass and is the subject of considerable control efforts. Costelytra zealandica is also found on native vegetation which it often shares with a close relative Costelytra brunneum. Costelytra brunneum, however, is seldom found on introduced pasture species. What makes such a difference between close relatives and when do these preferences form?

Some of the variation in Costelytra zealandica

Marie-Caroline Lefort from the Bio-Protection Centre at Lincoln University, along with several colleagues from Lincoln, Plant and Food and Unitec, set out to find the answers to these questions. In a paper published in PeerJ they report the results from a series of experiments. Marie-Caroline (or MC) collected Costelytra zealandica larvae from both native and introduced vegetation, as well as larvae from Costelytra brunneum from native vegetation, and brought them back to the lab. In the first experiment larvae were placed in the centre of a chamber with three exits. The three exits led to either white clover (an introduced host plant), silver tussock (native host plant) or no plant (control) and the choice that the larvae made when exiting the chamber was recorded. In the second experiment the larvae were fed either white clover or silver tussock roots and their weight gain and survival rates over six weeks was recorded. In the choice experiment, larvae from Costelytra zealandica and Costelytra brunneum raised on native plants showed no preference for the types of plants they would move towards. Costelytra zealandica raised on white clover displayed a clear preference for moving towards the clover.  In the feeding experiments the larvae from both species raised on native plants showed no difference in survival or weight gain regardless of which roots they were fed. However, Costelytra zealandica raised on clover were 6 times more likely to survive when fed clover roots compared to tussock roots and gained twice as much weight. These results clearly suggest that there are large intra-species differences in Costelytra zealandica and that the early childhood environment that the larva lives in makes a huge difference to how the larva will develop later in life. This flexibility has allowed Costelytra zealandica to expand its host range, increase its evolutionary fitness, and boost its population numbers. Costelytra brunneum on the other hand does not look to have this same flexibility and is mainly restricted to the declining areas of native vegetation. So our invasive native species looks to be a great example of how phenotypic plasticity, allowing childhood experiences to fix how adults will look and behave, can lead to massive advantages. If Sauron had added this variation to his orcs he would have easily conquered Middle Earth. I must keep that in mind next time I read the Lord of the Rings.


Leave a Reply