Live-bearing plants

there are alternatives to producing seeds

On one of many dribbly days in July, as I wandered along a beach on North Douglas, I noticed a little plant with white flowers. It’s called alpine bistort, but at our latitude it also lives in meadows and roadsides at lower elevations. The top of the flowering spike bore small flowers but on the lower part of the spike, where flowers normally develop, there were–not seed capsules or fruits–but small plants.

Photo by Bob Armstrong

This is an unusual plant because it does not usually produce seeds. Instead, each flower makes a bulb-like structure, and from this grows a tiny little plant. Eventually, the new plantlet falls off and lands on the ground, ready to grow.

Botanists call this habit ‘vivipary’, which means live-bearing or bringing forth live young. The scientific name of the plant (Polygonum viviparum) reflects this habit. The little green plantlet has already started to make its own carbohydrates, so in a sense, it is off to a running start when it lands in a suitable spot nearby. In contrast, a seed might wait until next year, or next decade, before it germinates and produces a seedling.

Calling this habit ‘live-bearing’ does not imply that any seeds produced in the more customary way are dead! Seeds are not dead at all. However, being encased in several layers of tissue gives seeds several options not open to these viviparous plantlets. Seeds can go dormant, in some cases for tens or hundreds of years, awaiting the right conditions for germination. The coverings of a seed may be modified in many ways (wings, sticky coatings, prickly surfaces, edible fruits) that give seeds a variety of ways to be transported to new sites, often at some distance from the parent plant. Thus, seeds can often disperse in time (dormancy) and space, but terrestrial viviparous plantlets often cannot. Moreover, seeds of most plants (but not orchids) contain stored carbohydrates packed into the seed by the mother plant, so they can draw on this stored energy when they germinate and start to grow. Viviparous plantlets do it for themselves.

There aren’t many native viviparous plants in our area. In addition to alpine bistort, we have a couple of grasses that are at least sometimes viviparous and the uncommon snow saxifrage. These species (and some others that live elsewhere) form their plantlets asexually—without pollination and fertilization, so each little plant is like its mother. Asexual vivipary is thought to occur most frequently where suitable terrestrial habitats are very patchy or where favorable seasons for germination and early growth are short.

So these plants have been reported mostly from arctic, alpine, or very arid areas.

Elsewhere in the world, however, some viviparous species produce plantlets by sexual reproduction. The flowers are pollinated and seeds develop, but the embryos begin to grow and, in some cases, plantlets sprout while the seed is still on the mother plant. In these species, there is regular genetic mixing across generations and offspring are not virtually identical to their parents. Many of these species live in warm tropical waters. Perhaps the most famous examples are some mangroves, whose fertilized seeds germinate while still on the parent; the whole young plant then drops off and floats to a new site.

Vivipary has evolved many times in the plant kingdom. Although the conditions that might favor the evolution of vivipary have been discussed by botanists, perhaps the only fairly clear conclusion is that different conditions are probably relevant for different species. As so often happens, there emerges no single, simple explanation.



from skyline to shoreline in Southeast Alaska

Marmots belong to the large group of squirrel-like rodents that occur around the world (except Australia and Antarctica). There are over a dozen species of marmot, all in the northern hemisphere, and Alaska has three of them. The woodchuck is found only in the central Interior of Alaska, the westernmost extension of its wide North American range. The Brooks Range (and northwestern Alaska) has its own marmot species, known as Brower’s marmot, which occurs nowhere else in the world. The third species is the hoary marmot (closely related to Brower’s); it lives across southern Alaska, including Southeast, and on southward through the mountains to Montana and Idaho.

Over much of their range, hoary marmots are residents of rocky alpine areas. Hoary marmots have been studied intensively in Washington, where they are the marmot species found at the highest elevations, above the habitats of other marmots. Here we see them on Gold Ridge and the ridges on Douglas Island, for example. In Juneau and probably elsewhere in Southeast, however, marmots are not limited to alpine areas but can be found at sea level, living just above the high tide line, where they like their favorite rock piles too, but sometimes they create burrows in moraines and sandbanks underneath large trees.

Marmots spend a lot of time in their burrows, so we only see them for a limited part of the year. They hibernate for many months during the winter, going to sleep in fall and staying in their burrows until spring. They retreat to their burrows in hot summer weather too, avoiding hot weather and diving underground to avoid predators. Most hikers are familiar with their whistled alarm call, given in response to perceived threats, be they human or canine or eagle; it’s a signal saying ‘Look out! Be ready to dive for cover!”

Hoary marmots favor habitats such as rocky talus slopes, where they can create burrows that are protected from most predators and from the extremes of weather. They dig several kinds of burrows: some are used as hibernation places, some serve as residences for females with young, some are used as living quarters by juveniles or males, and other, smaller, ones serve as refuges in which to hide from sudden danger. Meadows full of tasty greens are always nearby. Burrowing sites and food availability are two important factors that determine where hoary marmots can live. Suitable habitat is limited and patchily distributed.

Burrows are also very important for winter survival. Deep burrows are sheltered from winter cold, and a thick snow cover also helps marmots survive over the winter while they hibernate. Overwinter survival of pups is also related to nutritional status: those that are born late in spring/summer have a shorter period of time in which to feed, so they enter hibernation with less fat than those born early in the season, and are less likely to survive than pups that fed all summer long.

Hoary marmots mature when they are three years old. Females generally start breeding when they reach maturity, usually bearing offspring in alternate years. Young marmots stay with their mother until they are two years old; then they may disperse to other areas. Females with pups or yearlings have residence burrows that are not shared with other individuals.

Mature males generally hold territories in suitable habitat, sharing that space with females, juveniles, and pups. After maturation, however, some males may spend a year or more as vagrants or as subordinate satellites within an established territory of a dominant male. Satellites may move up to become a territory owner when the previous owner dies.

If the territory of a mature male contains rich foraging grounds and good burrow locations for more than one female and her offspring, two (rarely three) females may settle there. Not content to have one or two females, territorial males sometimes go gallivanting to other territories, looking for casual liaisons (note that this implies the existence of willing females!). Gallivanting appears to be relatively rare, however, so presumably most of the offspring born on a territory are fathered by the resident male.

Are bigamy and monogamy equally successful in leaving offspring for the next generations? One would think that bigamous males (with two females) would father more offspring than monogamous males, in general. However, studies in the Pacific Northwest indicate that monogamous males may last longer as territory owners than bigamous males. Furthermore, females mated to a bigamous male are more likely to skip an extra year between litters. So the lifetime legacies (measured in number of descendants) of bigamous and monogamous males may not differ greatly. For females, however, the lower frequency of reproduction in a bigamous relationship probably means that they have a lower lifetime output of young than females in monogamous relationships, on average.

I would love to see a good study of marmots in Southeast. Do marmots in Southeast fit the examples revealed by studies in the Pacific Northwest? Do alpine and beach marmots differ in their social arrangements, such as the frequency of bigamy, and the effects of mating arrangements on survival and production of young? Does survival of pups or adults differ with elevation? The potential length of the summer feeding period is surely greater at low elevation….unless beach marmots have to spend more burrow time in summer, to escape hot weather (if any). Research funds are sadly scarce these days, so such questions may not be answered in the near future.

Spruce bud blight

an unwelcome new threat to Southeast Alaska forests

There’s a new, probably non-native, invasive species in town, just discovered in late June. It’s a disease-causing fungus (Gemmamyces piceae) that afflicts spruce buds, often killing them altogether but sometimes just causing deformed buds and twigs. Heavily infected trees that lose many buds cannot make new needles that allow the tree to continue growing; old needles drop off naturally after a few years of service. Without new needles, eventually these severely damaged trees are likely to die. Although we know that Sitka spruce is susceptible, we do not yet know if it is prone to such severe, lethal infection. In any case, this is not something we would welcome in our multi-valued spruce forests!

Infestations of this pathogenic fungus were first noticed on the Kenai, in 2013, and later discovered near Anchorage and Fairbanks. Recent surveys have found that this fungus is apparently widespread in Southcentral and Interior Alaska, at least is road-accessible locations. Researchers are now beginning to study genetic variation in the population, which will help determine how long it has been in Alaska, as well as assess its native/nonnative status. Now it is in Juneau, on Sitka spruce trees near the Shrine of St Therese. Recognizing the potential seriousness of the now-localized outbreak, and in hopes of preventing its spread, scientists with Forest Health Protection at the Forestry Science Lab and the staff at the Shrine have worked together to remove and burn all spruce trees that show signs and symptoms of this fungal infection—to ‘nip it in the bud’, so to speak. This site and others will be now monitored by those scientists for indications that the infection has spread.

Researchers suspect that the fungus was introduced to Alaska by arriving on previously infected ornamental spruces that were brought in and planted. The movement of live plant material is a key pathway for the introduction of plant diseases. Colorado blue spruce, for example, is highly susceptible to this pathogenic fungus and is commonly planted as an ornamental in parks and gardens. In Europe, Colorado blue spruce has been widely used in plantations, to ‘replace’ logged-off natural forests, and in the Czech Republic the fungus has killed trees on many thousands of acres of those plantations of introduced spruces. Although the fungus was present in central Europe for some time previously, relatively recent environmental conditions of temperature and humidity probably made possible the destructive outbreak of the disease; the fungus does well in cool conditions.

Spores of this fungus disperse to new sites on the wind. But they also can be carried by rain, from infected upper branches to lower ones on the same tree. The existing fungal infections at the Shrine may already have sent spores to new sites, or it may do so in the coming weeks, if undetected infections remain. The spores infect next year’s buds, which are very small now (July); next year, these buds may be black and dead, or still alive but bent and deformed.

Infected buds. Photo by Loretta Winston

What are the signs of infection by this fungus? When the fungus is mature, it develops a black, lumpy, spore-producing body on buds and new growth. One can see symptoms of previous infection on twigs that are two or three years old: they are bent at an angle, very unlike the natural growth pattern.

Characteristic bent twig. Photo by Loretta Winston

Forest Health professionals at the Juneau Forestry Sciences Laboratory (U. S. Forest Service) are asking Juneau folks to be on the lookout for signs and symptoms of infection on our Sitka spruces. If you see them, please report them to Forest Pathologist Robin Mulvey (586-7971, 500-4962; Send a close-up photo to her email if you can, along with precise location information. If you collect the infected twigs for a specimen, be sure to put them in a well-closed plastic bag so no spores can escape!

Addendum (11 December 2017): Genetic studies have more recently shown that the bud blight profiled in this essay probably belongs to another species that is native and relatively harmless.

Good finds in Gustavus

stealthy spiders, ambitious amphibians, strange ferns, and more

A summertime walk through woods and meadows is almost always good—birds are singing, flowers are blooming, and there’s always nice fresh air. But sometimes all the little pleasures form a base on which rest some observations of particular interest. Here are a few good ones from a recent trip to Gustavus.

–Dandelions had mostly gone to seed, so fields that had been golden with flowers were now white with plumes on mature seeds ready to disperse on the wind. But here and there we found a laggard flower, still yellow and conspicuous on the background of white. On one of these late bloomers there was a bumblebee, a strangely immobile bee. Looking more closely, we saw a yellow crab spider with the bee in its clutches. Crab spiders are venomous (to insects), immobilizing their prey and then sucking out the juices. Dinner was in progress and the bee would fly no more. Crab spiders are generally ambush-predators; some of them lurk on flowers in hopes that a tasty insect will alight. The color of the spider often matches the color of the flower on which it awaits a victim.

photo by Kerry Howard

–The ponds at the gravel pits are a great place to see shorebirds, swallows, and kingfishers. There were sticklebacks swimming around and, in June, there were gravid females full of eggs. One pond held many thousands of toad tadpoles, swarming in the shallows where the water temperature was salubrious. They came in a variety of sizes—some at least six times bigger than the smallest. A female toad can lay thousands of eggs; the hordes of tadpoles that we saw undoubtedly had many mothers, which probably laid their eggs at somewhat different times, accounting for the size variation. None of them had begun to transform into toadlets; no little legs were visible. A dense pack of tadpoles clustered around a silvery object, each one trying to grab a mouthful. Looking closely, we discovered that the silvery object was a dead stickleback. Toad tadpoles commonly feed on algae and detritus, but they are also known to scavenge carrion and even the dead bodies of their comrades. Toad (and frog) populations have declined dramatically almost everywhere, and it was heartening to see this large aggregation of juveniles.

–Gustavus is noted for (among other things) its wide sandy beaches. On our way out to one of them, we heard some odd sounds, rather like the hooting of a small owl. As we listened carefully, however, it became apparent that several snipes were performing their aerial territorial display. It’s called ‘winnowing’, and it’s made by the rapid passage of air over the spread-out tail feathers, usually as the bird dives toward the ground from high in the air. Usually the male does this but sometimes females do too. I hadn’t heard this display for a long time and it was a gladsome sound.

–Out on the sandy beaches we found windrows of long, flexible tubes that were the former housing of certain marine worms. The worms were long gone, possibly starved at the end of winter when food is scarce. Then the tides presumably stripped the empty tubes from their attachment points and piled them up on the beach. This observation stimulated a lot of conjecture but no concrete answers.

–On the vegetated sand dunes there were lots of the strange little ferns called moonworts (a.k.a. grape ferns). They don’t look at all like ferns to the layman’s eyes, because the fronds are generally not very lacy or branched. We found many that appeared to be the common moonwort, but there were also a few much more robust individuals that were certainly a different species. On one of the postglacial-uplift meadows we found another kind, one that is now classified in a different genus; the fronds on this one (so-called rattlesnake fern) are somewhat more ‘fern-y’. All three of these are widespread species in North America and even beyond, but they are so odd that it is always fun to find them.

–The pilings of the public dock usually offer something even to a casual observer. Enormous white anemones, far larger than any we usually see in the rocky intertidal zone, wave their tentacles if the tide is in. Sea stars cling to the vertical surfaces too, but the largest ones have trouble hanging on when the tide goes out and leaves them above the waterline. Colorful sponges and tunicates add to the array. Sometimes there’s a giant whelk laying a coil of egg cases. Small fish sometimes gather under the docks and are visible between the pilings. And while one inspects the fauna on the dock, barn swallows are swooping overhead, gathering flies and mosquitoes for their chicks.

–We searched for lady’s slipper orchids (of which more, later). One clump of flowering stems still included a stalk with last year’s seed capsule, well dried. Someone opened the capsule to see if any seeds were left and found, instead, a tiny spider guarding her minute ball of orange eggs. We were sorry to have destroyed her safe-house!

–Sweetgrass grows in many Gustavian meadows and some of us stopped to braid some stems. Braided sweetgrass is used, especially by Native Americans, to construct baskets and decorative items, and we had to try just a simple braid. As we concentrated on our task, we heard thundering hoofbeats, getting rapidly closer. Turning around, we saw a fast-trotting female moose, followed by a young calf. They were so intent on getting away from whatever startled them that they ignored us and passed by, barely thirty feet away, and off they went, full tilt.

Drama on the home pond

aerial attacks on fuzzy chicks

A great ruckus arose on my pond, one afternoon in early June, while I was leisurely scribbling, comfortable in my big easy chair: agitated high-decibel quacking of mallard. Of course, I leaped out of my chair to see what was happening, just in time to see an eagle swoop up from the pond into a spruce tree, dropping a couple of feathers as it landed.

Quickly, I checked the surface of the pond—a female mallard had been bringing her brood of ten tiny ducklings (not much bigger than my fist) to the pond to forage. There was a special place on the far side of the pond, right next to a tuft of weeds, where she would call them to come and rest under her wings. Having watched this family for a few days, of course they were ‘my’ ducks and I didn’t want them to become an eagle snack.

I immediately counted the little ones—no easy task, because they were scooting all over the pond, in and out of cover. But finally, all were accounted for. Mama mallard went on quacking, about one quack per second, for the next two hours. Upon consideration, I guessed that the eagle’s failed attempt had been on the female herself; a duckling would hardly have made one mouthful.

That eagle sat in the tree for over an hour, all of its attention clearly focused very intently on the duck family. It was not distracted by a bunch of juncos flitting about in the tree or around the seed feeder, or by me going out on the deck. A hummingbird close by its head warranted only a sidelong glance. Twice in that long span of time, the eagle thrust forward its head and started to lift its wings, as if to launch a new attack. But then it settled down again, one foot tucked up under its feathery skirts.

Meanwhile, the little ducklings often ventured out from the shelter of overhanging alders to forage. They were adept at diving and scuttled over the pond surface in all directions. Mama duck managed to call them back periodically, only to have them scoot out again. But she herself seldom went far from those protective alder branches.

After more than an hour, the eagle did some intensive preening and took off, but the female duck went on quacking, loudly and constantly. All the ducklings scattered over the pond, foraging actively, while mama continued to fuss. About thirty-five minutes later, back came the eagle and made another pass. Failed again and went to perch in the spruce tree. This time, however, it was very inattentive, fidgeting and looking all around, and it flew away after about five minutes. Needless to say, during all this activity, I got no writing done at all.

The departure of the eagle was a relief for both me and the female duck, although she went on protesting for another hour. The little ones were, naturally, oblivious of the threat, responding only to the need for food and (sometimes) the instructions of their mother.

Several days later, all the little ducklings were still accounted for. They were bigger now, maybe almost twice as big as before. Mama duck had more trouble fitting them all under her wings when they rested. In addition, on the pond was a solo female, who probably lost her eggs to a predator, but who was assiduously attended by a male that was still nattily dressed in breeding plumage. So perhaps she will have another chance to rear a brood.

This was the first time I’d ever seen an eagle at my pond, in all the twenty-five or more years of watching. There has been the occasional pygmy owl, and several goshawks. All the ‘gos’ were in brown plumage, i.e. not that of an adult male. Some of their attacks were successful. Of course, I have to wonder what predatory events I might have missed, while otherwise occupied.

Another day, another place: the day after the eagle threat, Parks and Rec hikers went to Cowee Meadows. We always go there in June (some of us go twice) to revel in the wildflower show. This is the fantastic meadow where we have, several times, recorded over seventy (!) species of flower in bloom in June. This time, we didn’t count them. Nevertheless, we enjoyed a good showing of lupine and buttercups; shooting stars were still splendid and the wild irises were just starting to open. More will come, later.

Some welcome news is that the state park crews have been working on the muddy, root-y parts of the trail, making it easier and safer for walking. They were at work on this day and we all said a big thank you. Yay, State Parks!