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Redwoods, Grasshoppers: New Designs in Well-Studied Species

Photo credit: David Coppedge.

While there’s fascination in finding new species in exotic environments, sometimes the common organisms scientists thought they knew turn out to possess traits that are just as astounding. These examples, one a giant plant and one a small animal, suggest that biologists will never run out of functional designs to discover any time soon. Sometimes they just need to look closer.

Redwood Leaves

The coastal redwoods of Northern California (Sequoia sempervirens) are well-known for their superlatives: tallest trees on earth, among the most massive living things, and ideally suited for survival against pests and fires. Tourists by the millions love hiking the trails through these magnificent specimens. For decades, scientists have studied them from base to crown. Is there anything more to learn? Ask scientists at the University of California, Davis: “Redwoods are among the most well-studied trees on the planet, and yet their mysteries continue to surprise and delight scientists and nature lovers.”

The new surprise is that these trees have two types of leaves — not one, as previously thought — and there is a “division of labor” between them. There’s a good functional reason for this:

Scientists from the University of California, Davis, discovered that redwood trees have two types of leaves, and those leaves have completely different jobs, according to a study in the American Journal of Botany. Together, these functionally distinct leaves allow the world’s tallest trees to thrive in both wet and dry parts of their range in California, without sacrificing water or food. [Emphasis added]

Two Leaf Types 

Look at the photo of the two leaf types below, by Alana Chin at UC Davis, via EurekAlert!

The “peripheral leaf” extends its leaflets outward for capturing light for photosynthesis. The “axial leaf” type wraps its leaflets around the stem for absorbing water. Additionally, it was found that the trees can shift the populations of these leaf types up or down the tree depending on the environment, as if reorganizing their “office space” for best productivity.

The peripheral leaf spends its working hours making the tree’s food — converting sunlight into sugar through photosynthesis. Its colleague, the axial leaf, does almost nothing to help with photosynthesis. Instead its specialty is to absorb water. In fact, the study found that a large redwood can absorb up to 14 gallons of water in just the first hour its leaves are wet.

In the wetter northern parts of the redwoods’ range, the crowns produce more peripheral leaves to gather as much light as they can during inclement weather. Those leaves have a waxy coating that slows water absorption without hindering photosynthesis. In the southern parts of the range, the axial leaves are found higher up in the tree “to take more advantage of fog and rain, which occur less often in the drier environment.” The leaf types, therefore, are distributed throughout the tree for best overall productivity.

De Facto Design Reasoning

Whether or not the biologists accept intelligent design theory, the discoveries were made by de facto design reasoning:

“I’d be surprised if there weren’t a lot of conifers doing this,” said lead author Alana Chin, a Ph.D. student in ecology with the UC Davis Department of Plant Sciences at the time of the study. “Having leaves that aren’t for photosynthesis is in itself surprising. If you’re a tree, you don’t want to have a leaf that’s not photosynthesizing unless there’s a very good reason for it.”

Plants cannot move around to get out of harm’s way. Instead, they internally adjust their cells, tissues and structures to get the most out of their circumstances. These stately trees, reaching high into the sky against the force of gravity, exhibit multiple strategies for best performance no matter where their seeds land. From the cells that use strong building blocks to form woody tissues and bark that can withstand the weight of 100 million leaves and branches, to the vessels that can transport water over 300 feet high, to the protective bark that can shield them from pests and wildfires, these giants rightly inspire our admiration. Here is another surprising functional design that was discovered by looking a little closer.

Grasshopper Teeth

If redwoods are a byword for great stature, grasshoppers represent the opposite. And what insect could be more common or familiar? One would think there’s nothing more to learn about them. Biologists at the University of Leicester, however, just found something “startling”: “What do grasshoppers eat? It’s not just grass! New Leicester research shows similarities with mammal teeth like never before.” Like mammal teeth? No kidding. 

New research led by palaeobiologists at the University of Leicester has identified startling similarities between the mouths of grasshoppers and mammal teeth.

Maybe the Old Testament prophet Joel was prescient when he described locusts as having “teeth [like] lion’s teeth.” 

There are around 11,000 known species of grasshopper. It likely comes as a surprise that not all grasshoppers eat grass. In fact, they play a range of important roles in grasslands and other ecosystems — some are even carnivorous.

Fortunately, there are no man-eating grasshoppers roaming our lawns like lions on the prowl. The team explains their reason for a closer look at grasshopper teeth:

Understanding the relationship between form, function and diet in feeding structures is critical to constraining the roles of organisms in their ecosystem and adaptive responses to food resources. Yet, analysis of this relationship in invertebrates has been hampered by a reliance on descriptive and qualitative characterisation of the shapes of feeding structures. This has led to a lack of robust statistical analyses and overreliance on analogy and plausibilityespecially for extinct taxa and animals that are hard to observe feeding.

Using non-destructive methods of imaging, the team got closer, more precise measurements of the tooth shapes of 45 extant species of grasshoppers found in museum cases. To their surprise, the same models that biologists use to infer the diets of extinct mammals from their teeth can be used to infer the diets of Orthopterans, the order of insects that includes grasshoppers, locusts, and crickets. The open-access paper by Stockey et al. in Methods in Ecology and Evolution states:

We find that topographic metrics applied to Orthoptera successfully recover the same relationship between dietary intractability and dental tool morphology as they do in mammals, and that combination of individual metrics in multivariate analysis most strongly captures this relationship. Furthermore, multivariate topographic metrics calibrated to the food consumed by mammals accurately predict dietary differences between orthopterans (82% taxa correctly assigned).

look at the tooth shapes of grasshoppers confirms a variety of outlines suited to each species’ diet: whether serrated with “complex undulating landscapes” for cutting plant material or carved with “steeper slopes and sharper cliff edges” for eating worms and other insects.

Form and Function

But how can the relationship between form and function be so similar between mammals and grasshoppers when they have no evolutionary relationship? They don’t say, although they find it “pretty amazing.”

Surprisingly, comparing the mandible landscapes of grasshoppers with mammal’s teeth allows grasshopper diet to be predicted with 82% accuracy — pretty amazing when you consider that the mouthparts of mammals and grasshoppers have evolved independently for 400 million years, and were not present in their common ancestor.”

Indeed. It’s not to be expected given evolutionary premises that similar forms would “span broad phylogenetic distances.”

Our analyses confirm that the relationship between topographic metric values and diet in orthopterans is predominantly a measure of ecological similarity rather than a reflection of closeness of evolutionary relationships. The similarity of multivariate metrics between orthopterans and mammals with similar diets discussed below demonstrates this further.

Multivariate analysis provides powerful confirmation that the relationship between form and function in feeding structures holds true across phylogenetic distance: non-homologous feeding structures in distantly related taxa are comparable.

Not Much Help from Darwinism

It doesn’t appear that Darwinism provided much help in understanding this lesson in form following function. The team didn’t even begin to speculate on how these functional designs could have arisen independently. Their last paragraph states:

Our results indicate a high degree of comparability of dental tools and dietary intractability in animals separated by vast phylogenetic distances. Further validation of the relationship between dental topographic metrics and diet would be worthwhile, adding dietary specifics for non-gnathostome groups in particular. But it is clear that multivariate dental topographic analysis can be applied with confidence to a wide range of feeding structures with tooth-like functions, enabling quantitative analysis and statistical hypothesis testing of the relationships between form, function and diet across much of bilaterian phylogeny and through half a billion years of evolution.

That narrative gloss reveals more about the credulity underlying a blind commitment to Darwinism than about the actual usefulness of Darwin’s theory to yield understanding. Intelligent design theory has a ready hypothesis for expecting form to follow function: any successful organism will possess the toolkit needed for its success. ID encourages scientists to look more closely and learn. When they do, as these two examples illustrate, new wondrous functional designs are likely to appear.