Life and Death

I found abundant signs of life and death in a recent walk through the woods

jumping spider with midge

Jumping spider eating a midge

Zelus sp.

Assassin bugs stalking

Zelus sp.

fly carpenter ant

Carpenter ants dragging a still living fly back to their colony

green bottle fly

Blow fly waiting for something to die

racoon nest

Squeaks from a hollow tree trunk

baby raccoon with mom

Raccoon cubs squabbling and breastfeedingskunk cabbageAnd skunk cabbage emerging after a long winter

Spanish Moss – Delightful Dangling Denizens of the South

Expansive live oaks dripping with spanish moss–a quintessential scene of the southeastern United States.

Spanish moss (Tillandsia usneoides)

Contrary to the common name they are not actually a moss, rather a flowering plants in the Bromeliad family. They can reproduce from seed or by chunks moved by wind or birds, who use them for nest building. Their arboreal tangles provide important habitat for a wide diversity of arthropods including a highly specialized jumping spider which appears to only live in spanish moss.

Spanish moss (Tillandsia usneoides)

Spanish moss (Tillandsia usneoides) live a pretty strange life style, for a plant. As “air plants” they spend their whole lives draped over tree branches far from anything resembling soil. So despite inhabiting only wet semi-tropical regions they are at serious risk of desiccation. To combat this they have a specialized water efficient form of photosynthesis called CAM Photosynthesis. This is the same trick that cacti use to conserve water. Up in the trees spanish moss must also find nutrients. Instead of having roots their long slender leaves are covered in scaly hairs that can absorb nutrients and water. Nutrients comes through rainwater and dust and also from the trees they inhabit. They are not stealers like parasitic mistletoe, rather, they soak up what washes out of tree bark and leaves. This source of nutrients is important enough that trees which leach few nutrients do not provide suitable habitat for spanish moss.

Spanish moss (Tillandsia usneoides)

Spanish moss is also quite useful to humans. Up until the advent of synthetic fibers spanish moss was harvested from the ground after storms or directly from trees, then heaped into piles to decompose for a few weeks leaving just the dark elastic cords that make up the plants’ center. These were dried and cleaned, then used to stuff mattresses, car seats, or spun into rope, just to name a few uses. Spanish moss is also potentially useful as a simple way to monitor air pollution. Because they absorb particulates from the air which then accumulate in their tissues, measuring levels of toxic substances like Mercury in spanish moss may provide an accurate measure of air pollution in the area.

The South provides many natural history gems, but the ones hanging from the trees are among my favorites.

Photos taken on Sapelo Island, Georgia

Spring Is a Time of Firsts

The first unwavering stare from a reptile

Common garter snake (Thamnophis sirtalis)

The first butterfly

Comma (Polygonia c-album)

The first disappearing act

Comma (Polygonia c-album)

Comma (Polygonia c-album)

The first leaves reaching for the sun

Mayapple (Podophyllum peltatum)

And the first flowers calling out

Spring beauty (Claytonia virginica)


Species:

Common garter snake (Thamnophis sirtalis)

Comma (Polygonia c-album)

Mayapple (Podophyllum peltatum)

Spring beauty (Claytonia virginica)

All photos taken 25 April 2015 in the broadleaf forests of Nancy Moore Park in East Lansing, Michigan.

Weekend Arachnids

I found some nifty arachnids this weekend in East Lansing. First are a couple of fishing spiders:

fishing spider

fishing spider

These are two different individuals, not sure if they are the same species. Now an adorable jumping spider:

jumping spider

jumping spider

Finally, a velvet mite scampering around on a rotten log:

velvet mite

Signs of Spring

I went for a walk in the woods at Lake Lansing Park North

Life is just starting to return from the long winter

forest pond The salamanders are not around yet but I reckon they will be soon

20150321-17Fungi are always there, digesting and consuming

caterpillar eggs Malacosoma americanaAs soon as the weather warms these eastern tent caterpillars (Malacosoma americana) will emerge to devour the leaves of this unfortunate cherry tree

mossThe mosses are growing skyward before the trees produce their leaves and shade them out

skunk cabbage (Symplocarpus foetidus)Intrepid skunk cabbage (Symplocarpus foetidus) make their own heat!
tree reflection pond leavesFrom some perspectives the trees already have leaves

They will soon

I’m excited

Beautiful Buds!

Winter is kind of sad, all my favorite photography subjects are either dead or dormant. But today it warmed up a bit and there was blue sky out so I found some beautiful subjects that are at their best in the winter, plants’ leaf buds! They are delightfully variable in shape and color among species, and many have quite a lot of character. Be sure to check leaf buds out next time you feel there is not much interesting out in nature to look at. 20150221-8cornus bud20150221-10Zanthoxylum americanum Common Prickly Ash20150221-1220150221-13

Spines, Photosynthetic Tricks, and Other Marvels of Cacti Evolution

Cacti (family Cactaceae) are the strange and beautiful plants best known for inhabiting deserts and being a pain in your butt, hand, leg, or whatever body part that happens to brush up against them. These traits are the result of a fascinating evolutionary story that played out in the American deserts, at least initially.

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So, cacti don’t have leaves, right? Well, kind of, but those spiky bits are technically modified leaves. That is why they are, in botanical lingo, spines. (Sharp plant parts derived from the epidermis are called prickles and modified branches or stems are called thorns). At some point early in the evolution of cacti their leaves evolved to be smaller and smaller and eventually into hardened points that did not photosynthesize. Cacti also evolved green stems which took over the photosynthetic tasks.

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So why would cacti evolve these two unusual features of green stems and non-photosynthetic stabby leaves? Well, these combination of traits are adaptations to dry and resource-poor environments. Big and flat leaves have lots of surface area which is typically a good thing from a plant’s perspective as it captures lots of sunlight for photosynthesis. But many plants have more sunlight than they can handle and more photosynthetic area means more water loss. All photosynthesis requires gas exchange, carbon dioxide in and oxygen and water vapor out. So for plants in water-limited and very sunny environments, like deserts, adaptations that limit photosynthetic area (and thus limit water-losing gas exchange) are likely to be advantageous and selected for.

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So as adaptation to very dry desert environments cacti evolved photosynthetic stems which presumably lessen water loss during photosynthesis. Great. But there are more photosynthetic tricks in cacti that you can’t see. Early cacti evolved an additional solution to the photosynthesis-water-loss problem, a whole new physiological mechanisms for photosynthesis called CAM photosynthesis. There are a lot of differences between CAM photosynthesis and what most other plants use, but the most important part is that cacti, and other CAM plants, can leave their stomata (the little pores that allow gas exchange) closed during the heat of the day and instead do all their gas exchange at night when it is cooler and more humid. This little trick greatly reduced water loss and gives CAM photosynthesis plants an advantage in very dry environments.

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So why the spines? Why not just lose the leaves all together? The short answer is that spines are a defense against herbivores. Herbivory, or the consumption of plant matter, can be really bad news for a plant: get a bunch of your photosynthetic tissue eaten, have to grow it back, not enough resources left to produce seeds and reproduce, less offspring, lower fitness. Plants that get less damage from herbivores might have higher fitness so evolution should favor plants with traits that reduce herbivory. This is particularly true in environments where resources are scarce, like deserts, where regrowing tissue lost to herbivory is very difficult (this is called the Resource Availability Hypothesis). Thus, plants in low resource environments, like cacti in deserts, invest very heavily in defenses, like big gnarly spines.

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The >1500 cactus species all live in the Americas (well except one in Africa, probably dispersed there by birds) and mostly in arid environments. However, there are also many cacti that live in the tropical rainforests of Central and South America. At first this doesn’t make sense why a arid-adapted group would have a center of diversity in some of the world’s wettest habitats, until you look at the micro-habitats they live in, namely, up in the forest canopy. Rainforest cacti are almost all ephiphytes, meaning they grow on other plants, normally the branches of large trees. From plants’ perspective these environments are actually very dry, it is hot, there is no soil to hold water, and airflow from all directions desiccates. So the elegant adaptation that cacti evolved in the deserts gave them an advantage as tropical ephiphytes and when they arrived in these new habitats they thrived and diversified.

20131219-31Around 30 million years cacti emerged and in the last 10 million years spread across North and South America. This is amazingly fast for the evolution and spread of a plant lineage across such a large geographic area with a huge range of ecological conditions. This incredible success was likely due to the evolution of the morphological, physiological, and defensive traits that make cacti so unique and fascinating. Understanding their evolution requires thinking about the environmental and ecological conditions that cacti live and thrive in, and also remembering that those spines are not just a pain in your butt but also a pain in the butt (or mouth!) of anything that wants to eat them.

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(All photos from the Sonoran Desert in Arizona)