Welcome back everyone! Sorry for the long delay in writing an entry, but life and everything that comes with it just got a bit busy. First off, I hope everyone is doing well so far this year. With the high number of thunderstorms, flood and tornado warnings, and hail events we can only hope that nobody was seriously injured. However, the benefit of all of this crazy weather is that our garden is doing well. The plants are thriving as well as the pollinators that love to come visit our little sanctuary. So, let’s talk about pollinators and their importance, but in a way that you may not have considered. Energy transfer.
When I went up to the garden for the holiday weekend last month, I noticed something that seemed quite peculiar. Although I did not see any caterpillars I saw over 10 butterfly species. Even in my photos I didn’t spot one as by catch in the frame. Due to this I began to ponder about what could be the reason for this. It hit me that just the weekend before I was leading bird walks for World Migratory Bird Day at a local nature center. Now, if you don’t know much about the migration let me explain. Roughly from the middle of February to the middle of May is when billions of birds from Central and South America will make their way to their nesting grounds in North America. Due to the great expense of energy that long distance flight has on a bird I began to think about how much energy gets used on such a trek. So, let’s get into this concept a bit and discover how important pollinators truly are to the transfer of energy upwards.
Plants begin to grow in late winter or early spring as a response to three environmental signals. A minimum number of cold days, increasing warmth, and more hours of light. This boost in sunlight allows for photosynthesis to take place which leads to growth of foliage. Since photosynthetic life can capture sunlight, this happens to be the first transfer of energy from the sun to planet earth. I won’t go through in-depth chemistry here, but the reaction is highlighted in figure 1. As the plant collects CO2 from the atmosphere and H2O from the roots, the light energy is converted to glucose for the cell and oxygen for the atmosphere. Now we have a bit of a problem though. How are birds supposed to get this energy during their migration when they don’t eat leafy greens?
By eating pollinators of course. That foliage and growth represents stored energy in an inaccessible form, but also an increase in niches both above and within the soil. Luckily, the pollinators are happy to fill the new spaces. These may be under a leaf, inside of a stalk, and even among the roots for species that have part of their life cycle underground. So, as last year broods emerge from a state of diapause, they grow into adults and begin to propagate the next generation. This is where the really interesting things begin.
Although we may not think about it much, where eggs are laid has a really big impact on the success rate of a clutch as well as how quickly it hatches. If we look at figure 2, we can see a clump of eggs on the bottom of a leaf. In order to understand why this is a good location, we need to go back to that photosynthesis reaction. Notice that the carbon dioxide is needed for the reaction to move forward, but how do plants get that? On the epidermis of the leaf there are small pores called stomata. During sunlight hours they open up and the atmospheric gas is able to get inside. What is interesting about this is that water will begin to come out of these openings by evaporation. This is why leaves in the afternoon can look wilted due to the water loss. What this does for the eggs though is helps to regulate the temperature in their microclimate. This is great for ensuring that the eggs do not burn up under the Texas sun. Once they hatch, the buffet soon begins for the larvae and all the animals that eat them.
Much like the sunlight energy had to be converted into a form which is readily available, the plant material has to be digested and transformed so it can be utilized by the next consumers in the energy web. However, there are a couple of things that differ in this energy transfer. The first is that the leaf material must be mechanically chewed up. Even though some larvae can devour entire plants, none of them do this by eating a leaf in one bite. The second is that the gut biota of the larvae must help with the chemical transition. So, what exactly do I mean by this? Let’s once again consider the photosynthesis equation. Notice how the equation contains 1C, 2 H2O, and 1 02 but they are arranged differently depending on which side of the equation they are on. This is the transformation.
In order for this transformation to occur, animals must rely on a series of organisms which inhabit their guts. These can include bacteria, protists, archaea, and even some fungi. Their specific biota will be determined by the niche that they have in the environment, and what they are eating. So, what exactly are they doing to help with this energy transfer? Quite a few things actually. They help with the digestion of the food, provide essential nutrients for host metabolism, prevent pathogen invasion, degrade phytotoxins and natural pesticides, and can even produce antibiotics. Due to this, the larvae are able to grow, stay healthy, and store energy for moving up the web.
So, what has been eating some of the pollinators that we have seen in the garden this year? Let’s start with some of the critters in the garden that are known predators. First up is a true bug in the order Hemiptera known as the Plains Bee Assassin (figure 4). This bug is quite an interesting character. They are known to eat bees and ants utilizing their rostrum to pierce
the exoskeleton and pump the prey full of saliva. The saliva helps to digest the innards, which allows them to suck out a nutrient rich liquid. For the prey of this insect this is a lethal problem, but they can be less than fun for humans too. I would advise against holding this bug unless you have a Petri dish for it to hang out in. They are known to have a painful “bite” and are not afraid to use it.
Up next, we have the American Nursery Web Spider (figure 5). These get their name from the web that the females build for their young brood to hatch and complete their first molt in. The female in the photo has the egg sac on her underside. This specimen was found in one of the cannas’ leaves. I thought it was just a web with nothing in it, but as soon as I lifted the leaf to take a look the female showed herself quite quickly. Therefore, I just took a photo and moved on. Something interesting about this spider is that it is an active hunter and does not utilize a web as we see in many other species. Instead, she utilizes ambush tactics to overwhelm her prey.
Another predator that I want to take a look at is actually a vertebrate. Commonly known as the five-lined skink, this lizard is one of the most common lizards in the eastern U.S. and is a
welcome sight at the garden. Until this May I had not seen one after all my hours of searching, but was pleasantly surprised to find this guy among the leaf litter and mulch. I have personally snagged a few in the wild and believe me when I say that the adults can bite harder than you think. This is necessary for their varied diet of arthropods and even some small vertebrates.
Up next are photos of some adult pollinators that I have found in the garden from late April to late May. Unfortunately, I could not include every butterfly that I saw, but there is a good number of them to view. Hope you enjoy.
The last photo I want to show is that of a Scissor-tailed Flycatcher. These amazing birds are in the family Tyrannidae aka the tyrant flycatchers. They get this name from their reputations to go drive away larger birds in their territory. To me, seeing these birds means that winter is definitely over and spring has really arrived. I usually notice them returning from their wintering grounds around late March. They are medium range migrants with wintering ground as far south as Panama. They are primarily insectivores and catch much of their prey on the wing.
I want to close out this entry and say that I hope this has given you an idea of how important energy transfer is to a functioning ecosystem. Without the pollinators at our garden, we would not be able to enjoy the biodiversity both within the garden and the area surrounding it.
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