The Biologist Is In: September 2018

Monday, September 24, 2018

Botanizing in Hawaii: Hawaiian Pepper

Closeup of a pepper plant branch. Several leaves hang down, with a few small elongated peppers and small whitish flowers raised above the leaves.

One of the plants I really wanted to find on my trip to Hawaii is known as the Hawaiian Pepper. This semi-wild pepper plant is generally referred to as a type of Capsicum frutescens, though you will often find references to it as different varieties of C. annuum. The ancestors of these chiles were first introduced to the islands around 1815, but they have since been integrated into the local culture and are often described as native. The small size and non-aggressive growth of the plants has allowed them to integrate into the island ecosystem without being too disruptive. Like other wild peppers around the world, birds also help distribute the seeds.

You can order seeds for it (I have no affiliation with the linked company, but found them via a quick search.), but I wanted to find the species growing wild on the islands.

Wider view of a whole pepper plant, with dried grass and shredded wood mulch around the plant.

The plants I found were... not exactly growing wild. As I walked along part of the resort where we were attending a conference, I glanced through a gap in some hedges and saw the characteristic look of chile plants. When I walked around behind the hedges, I found what looked like a little guerrilla garden someone had setup outside the watered and maintained landscaping of the resort. There were several Hawaiian Pepper plants of about the same age/size spaced about the area. I suspect someone who works on the resort planted them and would go by every now and again to tend to them.

I collected a few dried pods that had dropped to the ground around the plants. I didn't grow any this year, but I did send some seeds to a collaborator out in California. (They're on twitter as @ChaoticGenetics. Go check them out!) Last I heard the plants were growing well.

References

Monday, September 17, 2018

Botanizing in Hawaii: Railroad Vine

Green vines stretched out across the pale sand. There are a few pink flowers along the vines at left.

This is a plant that I knew from my childhood visits to the south Texas shore. Railroad Vine (Ipomoea pes-caprae) is a cousin of the common Morning Glory vine that is specialized to live on beach-side sand dunes. Its seeds are salt-water tolerant and are distributed widely by ocean currents. It grows on tropical and sub-tropical beaches worldwide. On Hawai'i, we only found it growing in one location. Most of the beaches we visited were too rocky for it to prosper.

Closeup of a pink flower with leaves around it.

Closeup of a single leaf. The leafe looks something like a round paper plate folded in half, with a stem at one end.

The flowers seemed to wilt under the intense sunlight. If we had found them earlier in the day, they probably would have looked more like my childhood memories of them.

The leaves are thick and smooth, with a major crease down the middle. My recollection is that the common name, "Railroad Vine" has to do with the plant's habit of growing long strait vines along the sand, with evenly spaced leaves.

References:

Monday, September 10, 2018

Botanizing in Hawaii: Solanum linnaeanum

Closeup of flower, leaves, and stem of plant. Flower is pink with four fused petals, forming a square, and has yellow anhers gathered in the center. The leaves are heavily lobed, with long sharp spines protruding from the underside. The stem too is covered in dramatic spines.

Hawaii has a long history of biological invasions. Plants and animals from all over the world have arrived and thrived there under the tropical sun. This can make it somewhat difficult to identify a random plant, because it could literally come from almost anywhere on the planet.

On one of my hikes, I found several plants I immediately recognized a member of the family Solanacea. This is the same family that includes tomatoes, peppers, and eggplants. I was pretty sure it was even a member of the genus Solanum, one of the several species sometimes referred to as "spiny eggplants".

Closeup of a few leaves and two small round fruit. One fruit is entirely brown. The other fruit is pale green with darker green stripes. The leaves are heavily lobed and covered in spines.

I collected a few fruit, intending to secure some seeds for planting back home in Minnesota. A couple days later, while sorting through my collection at a motel, I finally identified the plant as Solanum linnaeanum. Among its various common names are: "Poison Apple", "Devil's Apple", and "Apple of Sodom". They're native to parts of southern Africa, but have naturalized in Hawaii and various other places around the world.

The plant and its fruit are chock-full of toxins. Enough so that very few animals are willing to eat it. At about this point I decided not to take seeds home for garden trials. I do have a few seeds in my collection that come from highly toxic, or otherwise dangerous, plants. I wasn't entirely certain how much difficulty I would have with trying to leave Hawaii with collected seeds. If some official asked me what they were and why I had them, they might not appreciate my responses. So, to limit that risk, I dumped the S. linnaeanum seeds in the garbage.

(Several days later when I left the state, I learned I would have had no trouble at all. Dried seeds in vials didn't concern the USDA officials at the airport at all. Bringing seeds into Hawaii gets their attention, not taking seeds away from Hawaii. Next time I'll be a bit more bold.)

Interestingly, it appears this species can cross with domesticated eggplant (S. melongena). Doganlar et al. studied an F2 population derived from a cross of the two species in order to map the genomic positions of genes for traits important in domestication. Unfortunately, their paper doesn't have any photos of what the F2 plants looked like. Even with the risk of dragging the toxic traits from S. linnaeanum into the progeny, this would be a fun cross to recreate and explore. The wild species probably has numerous disease/insect resistance traits that would be useful in a garden eggplant, so there is probably value to the experiment beyond simple personal amusement. There's a few online vendors offering seed for this species, so I won't have to make another trip to Hawai'i to start on this project.

References:

Monday, September 3, 2018

Goats of Hawai'i

Group of five goats at the side of a curved road. Three goats are brown and two are black. Behind the goats are piles of dark brown lava stone and scattered clumps of dried grasses.

I visited Hawai'i last year for a horticulture conference. Well, my spouse was attending the conference. I was just going along for vacation. I spent a lot of time driving and hiking during the days when the conference was in session.

Much of the north-west side of the island where the conference was being held is dry-land, with exposed rock from several different ages of lava flows. I came across the bleached bones of pigs and other large animals among the lava, but rarely saw any sizable living creatures.

One day I was driving out to a nearby park to do some hiking and I saw a group of goats crossing the road. I lucked out and was able to capture a few photos like the one above. What immediately struck me about the goats was that they were colored just like many of the aged lava stones I had been seeing the previous few days. They didn't have any of the white markings so common on goats I've seen almost every where else.

It made me think the goats might have been under a pretty severe hunting pressure and that their colors represented adaptive camouflage, protecting them somewhat from visually-hunting humans. If the goats had been resting among the rocks as I drove by, I likely would have thought they too were just rocks.

Goat hunting on the Big Island is allowed year-round in some places, with defined seasons in other areas. There have been intense and largely successful goat eradication efforts in the larger fence-enclosed parks on the island. This represents a fairly high level of hunting pressure, which would definitely be expected to select for traits that help the animals avoid predation.

Unfortunately, I have been able to find no research on the topic of the evolution of wild goats of Hawai'i due to human hunting. This might be a nice topic for a PhD for some motivated student living on the island. Let me know if you come up with anything.

References: