On July 3rd, 2016 we learned about

The rise and fall of evolution’s first shot at butterflies

Apparently the evolutionary formula for butterflies is one part flying insect plus one part nectar-containing plant structure. That plant should ideally reproduce sexually, hiding pollen alongside any tasty nectar. It might take a few million years and might not include that fun caterpillar routine, but this appears to be all the environmental pressures necessary to produce an insect with a nectar-sucking proboscis, a narrow body and wide, scaled wings, complete with eye-spots. Basically, a butterfly! …that’s really a lacewing.

These faux-butterflies, known as kalligrammatid lacewings, date back to the Jurassic period, flying alongside dinosaurs like Stegosaurus and Brachiosaurus 125 million years ago. Earlier species more closely resembled modern lacewings, with more almond-shaped, transparent wings and split mouth parts intended for biting and chewing. Over time, they kalligrammatids evolved to look much more like a modern member of Lepidoptera, with wider wings decorated with colored scales and pigmented eye-spots, as well as fused mouth parts that acted like a proboscis. They even evolved pumping mechanisms and specialized lengths and widths to their probosci, allowing different species to focus on different sources of nectar. While these insects were functionally very similar to a modern Monarch or swallowtail, they were missing a key component of a butterfly’s life: flowers.

Feeding without flowers

Flowers didn’t exist in the Jurassic when kalligrammatids first started specializing in eye-catching nectar collecting. Instead, they likely found their food in cycads, Caytonialeans or Bennettitaleans. These woody plants with fern-like leaves all produced seeds in protective cones, and would have required some kind of pollen transfer for fertilization. Their pollen was produced deep in these cones inside “pollination droplets,” which is the nectar that would motivate kalligrammatids to pay a visit and further the plants’ reproductive cycles, similar to how bees and butterflies work with flowers today.

Foiled by flowers

The fossil record shows this ecosystem working well for around 40 million years, before being disrupted not by modern butterflies, but modern flowers. The flowers started taking over the niche previously occupied by Bennittitaleans plants, which then took the kalligrammatids lacewings with them, since the lacewings were such specialized feeders at that point. Modern butterflies in Lepidoptera then evolved to be the mutualistic feeders for flowers in what could be considered an extreme case of convergent evolution. Modern butterflies are actually the second iteration of insects evolving to serve the reproductive needs of nectar-producing plants.

Source: Butterflies in the Time of Dinosaurs, With Nary a Flower in Sight by Jennifer Frazer, The Artful Amoeba

On February 3rd, 2016 we learned about

Tegu lizards mysteriously manipulate their metabolism

Reptiles, like lizards, are ectotherms. They’re cold-blooded, which usually means they’re as warm or cold as the environment around them. Depending on when you’re looking, that is. While tegu generally follow the cold-blooded concept of being warm in sun and cool in the shade, scientists recently discovered that in the privacy of their burrows, for a few months a year, the lizards seem to forget this fundamental concept of reptile physiology and start pretending to be warm-blooded instead, warming themselves up at the start of their day.

Warm and cozy

The Argentine black and white tegu (Salvator merianae) use burrows as a way to retain heat overnight, avoiding dropping to the surface temperatures of the South American night. They then go further than this from September to December, somehow raising their body temperature by as much as 10° Celsius. They didn’t seem to be shivering, which is a trick employed by female pythons to warm their eggs, and were thought to maybe be using a hormone to increase the metabolic rate of their liver or heart. Whatever the trigger, it somehow stood up to isolation from both sunlight and food stimuli. Researchers were actually so surprised by this endothermic (internally heated) activity that they actually extended the study to three years of observations to ensure they hadn’t somehow mismeasured what was happening.

Aside from pinning down exactly how the tegu are warming themselves is the equally important question of why. Generating your own heat requires a lot more energy then passively absorbing it from the environment, which is no small trade-off to make. It’s actually been a question about the origins of warm-blooded animals like birds and mammals, since the earliest endothermic animals likely had to burn extra calories before it was terribly efficient for them to do so. Fortunately, the short duration of the tegu’s boosted temperatures may provide a clue about those ancient circumstances.

Reason in the season

September through December are the tegu’s mating season, and having a boosted metabolism during that time may be worth the extra calories. The energy would might help speed up reproduction. Furthermore, the pumped metabolism might also allow the animals to be more active with their young, a bit like all the coffee I drink when I’m playing with my kids in the morning. Some researchers feel that this cannot explain the full range of complex changes needed for the advent of warm-blooded creatures, but it’s one of the few transitional models we can observe today.

Source: First warm-blooded lizards switch on mystery heat source at will by Aisling Irwin, New Scientist