Big Things Come In Small Packages

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Meet Blossfeldia liliputana, the smallest species of cactus in the world. With a maximum diameter of only 12 mm, this wonderful succulent would be hard to spot tucked in among the nooks and crannies of rock outcrops. Its species name "liliputana" is a reference to the fictional island of Liliput (Gulliver's Travels) whose inhabitants were said to be rather small. If its size alone wasn't interesting in and of itself, the biology of B. liliputana is also downright bizarre.

Blossfeldia liliputana is native to arid regions between southern Bolivia and northern Argentina. It appears to prefer growing wedged between cracks in rock as these are usually the spots where just enough soil builds up to put down its roots. Root formation, however, does not happen for quite some time. Most often new individuals bud off from the parent plant. They emerge not from the base, but rather from apical tissues, yet another unique feature of this cactus. What's more, this cactus produces no spines. Instead, its numerous areoles are covered in a dense layer of trichomes that are felt-like to the touch.

As you can clearly see, this species is small. It only ever becomes conspicuous when it comes time to flower. Imagine a bunch of tiny white to pink cactus flowers poking out of a crevice. It must be a remarkable sight to see in person. Despite their showy appearance, its is believed that most are self-fertilized.

As mentioned, the size of this cactus isn't the only interesting thing about its biology. B. liliputana is categorized as a poikilohydric organism, meaning it doesn't have the ability to regulate its internal water content. Researchers have found that individual plants can lose up to 80% of their weight in water and can maintain that state for as long as two years without any negative effects. As such, colonies of these tiny cacti often appear shrunken or squished. Once the rains arrive, however, it springs back to its original rounded shape with seemingly no issues. Amazingly, a significant amount of water uptake happens via the fuzzy areoles that cover its surface, hence it does not harm the plant to hold off growing roots for quite some time. 

Speaking of water regulation, B. liliputana holds another record for having the lowest density of stomata of any terrestrial autotrophic vascular plant. Stomata are the pores in which plants regulate water and gas exchange so having so few may have something to do with why this species loses and gains water to such a degree that would kill most other vascular plant species.

Another peculiar quality of this cactus are its seeds. Unlike all other cacti whose seeds are hard and relatively smooth, the seeds of B. liliputana are hairy. Attached to each seed is a small fleshy structure called an aril, which aids in seed dispersal. As it turns out, B. liliputana relies on ants as its main seed dispersers. Ants attracted to the fleshy aril drag the seeds back to their nests, remove and eat the aril, and then discard the seed. This is often good news for the cactus because its seeds end up in nutrient-rich ant middens protected from both the elements and seed predators, often in much more suitable conditions for germination.

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Needless to say, B. liliputana is a bit of an oddball as far as cacti are concerned. Its highly derived features coupled with its bizarre biology have made it difficult for taxonomists to elucidate its relationship to the rest of the cactus family. It certainly deserves its own genus, to which it is the only member, however, it has been added to and removed form a handful of cactus subfamilies over the years. The most recent genetic analyses suggests that it is unique enough to warrant its own tribe within Cactaceae - Blossfeldieae.

Photo Credits: [1] [2] [3] [4]

Further Reading: [1] [2] [3]

Daffodil Insights

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Daffodils seem to be everywhere. Their horticultural popularity means that, for many of us, these plants are among the first flowers we see each spring. Daffodils are so commonplace that it's as if they evolved to live in our gardens and nowhere else. Indeed, daffodils have had a long, long history with human civilization, so much so that it is hard to say when our species first started to cohabitate. Our familiarity with these plants belies an intriguing natural history. What follows is a brief overview of the world of daffodils. 

If you are like me, then you may have gone through most of your life not noticing much difference between garden variety daffodils. Though many of us will be familiar with only a handful of daffodil species and cultivars, these introductions barely scratch the surface. One may be surprised to learn that as of 2008, more than 28,000 daffodil varieties have been named and that number continues to grow each and every year. Even outside of the garden, there is some serious debate over the number of daffodil species, much of this having to do with what constitutes a species in this group.

Narcissus poeticus

Narcissus poeticus

As I write this, all daffodils fall under the genus Narcissus. Estimates as to the number of species within Narcissus range from as few as 50 to as many as 80. The genus itself sits within the family Amaryllidaceae and is believed to have originated somewhere between the late Oligocene and early Miocene, some 18 to 30 million years ago. Despite its current global distribution, Narcissus are largely Mediterranean plants, with peak diversity occurring on the Iberian Peninsula. However, thanks to the aforementioned long and complicated history in cultivation, it has become quite difficult to understand the full range of diversity in form and habitat of many species. To understand this, we first need to understand a bit about their reproductive habits.

Much of the evolution of Narcissus seems to center around floral morphology and geographic isolation. More specifically, the length of the floral tube or "corona" and the position of the sexual organs within, dictates just who can effectively pollinate these plants. The corona itself is not made up of petals or sepals but instead, its tube-like appearance is due to a fusion of the stamens into the famous trumpet-like tube we know and love.

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Variation in corona shape and size has led to the evolution of three major pollination strategies within this genus. The first form is the daffodil form, whose stigma is situated at the mouth of the corolla, well beyond the 6 anthers. This form is largely pollinated by larger bees. The second form is the paperwhite form, whose stigma is situated more closely to or completely below the anthers at the mouth of the corona. This form is largely pollinated by various Lepidoptera as well as long tongued bees and flies. The third form is the triandrus form, which exhibits three distinct variations on stigma and anther length, all of which are situated deep within the long, narrow corona. The pendant presentation of the flowers in this group is thought to restrict various butterflies and moths from entering the flower in favor of bees.

Narcissus tazetta

Narcissus tazetta

The variations on these themes has led to much reproductive isolation among various Narcissus populations. Plants that enable one type of pollinator usually do so at the exclusion of others. Reproductive isolation plus geographic isolation brought on by differences in soil types, habitat types, and altitudinal preferences is thought to have led to a rapid radiation of these plants across the Mediterranean. All of this has gotten extremely complicated ever since humans first took a fancy to these bulbs.

Narcissus cyclamineus

Narcissus cyclamineus

Reproductive isolation is not perfect in these plants and natural hybrid zones do exist where the ranges of two species overlap. However, hybridization is made much easier with the helping hand of humans. Whether via landscape disturbance or direct intervention, human activity has caused an uptick in Narcissus hybridization. For centuries, we have been mixing these plants and moving them around with little to no record as to where they originated. What's more, populations frequently thought of as native are actually nothing more than naturalized individuals from ancient, long-forgotten introductions. For instance, Narcissus populations in places like China, Japan, and even Great Britain originated in this manner.

All of this mixing, matching, and hybridizing lends to some serious difficulty in delineating species boundaries. It would totally be within the bounds of reason to ask if some of the what we think of as species represent true species or simply geographic varieties on the path to further speciation. This, however, is largely speculative and will require much deeper dives into Narcissus phylogenetics.

Narcissus triandrus

Narcissus triandrus

Despite all of the confusion surrounding accurate Narcissus taxonomy, there are in fact plenty of true species worth getting to know. These range in form and habit far more than one would expect from horticulture. There are large Narcissus and small Narcissus. There are Narcissus with yellow flowers and Narcissus with white flowers. Some species produce upright flowers and some produce pendant flowers. There are even a handful of fall-blooming Narcissus. The variety of this genus is staggering if you are not prepared for it.

Narcissus viridiflorus  - a green, fall-blooming daffodil

Narcissus viridiflorus - a green, fall-blooming daffodil

After pollination, the various Narcissus employ a seed dispersal strategy that doesn't get talked about enough in reference to this group. Attached to each hard, black seed are fatty structures known as eliasomes. Eliasomes attract ants. Like many spring flowering plant species around the globe, Narcissus utilize ants as seed dispersers. Ants pick up the seeds and bring them back to their nests. They go about removing the eliasomes and then discard the seed. The seed, safely tucked away in a nutrient-rich ant midden, has a much higher chance of germination and survival than if things were left up to simple chance. It remains to be seen whether or not Narcissus obtain similar seed dispersal benefits from ants outside of their native range. Certainly Narcissus populations persist and naturalize readily, however, I am not aware if ants have any part in the matter.

The endangered  Narcissus alcaracensis .

The endangered Narcissus alcaracensis.

Despite their popularity in the garden, many Narcissus are having a hard go of it in the wild. Habitat destruction, climate change, and rampant collecting of wild bulbs are having serious impacts on Narcissus numbers. The IUCN considered at least 5 species to be endangered and a handful of some of the smaller species already thought to be extinct in the wild. In response to some of these issues, protected areas have been established that encompass at least some of the healthy populations that remain for some of these species.

If you are anything like me, you have ignored Narcissus for far too long. Sure, they aren't native to the continent on which I live, and sure, they are one of the most commonly used plants in a garden setting, but every species has a story to tell. I hope that, armed with this new knowledge, you at least take a second look at the Narcissus popping up around your neighborhood. More importantly, I hope this introduction makes you appreciate their wild origins and the fact that we still have much to learn about these plants. I have barely scratched the surface of this genus and there is more more information out there worth perusing. Finally, I hope we can do better for the wild progenitors of our favorite garden plants. They need all the help they can get and unless we start speaking up and working to preserve wild spaces, all that will remain are what we have in our gardens and that is not a future I want to be a part of.

Photo Credits: [1] [2] [3] [4] [5] [6] [7]

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9]

 

Bird's Foot Violet

As a life long denizen of deciduous forests, prairies and savannas present an entirely new set of stimuli. A recent excursion into an expansive oak savanna found me overwhelmed by the beauty of such places. Being mid October, the color pallet of the landscape ranged from myriad shades of reds, browns, yellows, and oranges. I was walking through a particularly sandy patch of soil when something caught my eye. A little flash of lavender shone through the amber grasses. To my astonishment I had found a plant that has managed to elude me for many years. 

What I had found was a bird's-foot violet (Viola pedata). Its deeply divided leaves, which faintly resemble a bird's foot, are unmistakable. What was even more fantastic was that this particular plant was in full bloom. I looked around and found only a small handful of other plants. This one was the only one in bloom. Though not unheard of for this time of year, I couldn't help but revel in the serendipity of the moment. 

Like all members of the genus Viola, bird's-foot violet is a photoperiodic plant. By this I mean that all aspects of its growth are sensitive to the relative amount of sunlight in any given day. Violets are generally spring time plants, however, the shortening days and cooler temperatures of fall aren't that different from spring. As such, this lovely little plant was perhaps a bit confused by the cool October weather. I didn't see any pollinators out and about but that doesn't mean that a hardy bumblebee wouldn't be lucky to stumble into its blooms. 

Back in my home state of New York, this particular species of violet is truly a rare find. The kind of habitats which it frequents have been largely destroyed. It is a xeric species that doesn't appreciate water hanging around for very long. Finding it growing in mostly sand was not surprising to say the least. Like most other violets, its seeds come complete with their own fleshy protuberance called an elaiosome. The purpose of these fatty attachments are to attract foraging ants in the genus Aphenogaster. The ants find the elaiosomes to their liking and take them back to their nest. Once the elaiosome is eaten, the seed is discarded into a refuse chamber inside the nest. There it finds a favorable microsite for germination full of nutrient-rich ant compost.

Further Reading:
http://www.jstor.org/stable/3668940?seq=1#page_scan_tab_contents

http://www.illinoiswildflowers.info/prairie/plantx/bird_violet.htm

Echoes of a Glacial Past

Climate change is often talked about in the context of direct effects on species. However, as John Muir so eloquently put it, "When we try to pick out anything by itself, we find it hitched to everything else in the Universe." In essence, nothing is ever black and white and a recent publication by Dr. Robert Warren and Dr. Mark Bradford illustrates this fact quite well.

Ants and plants have some very intricate interactions. A multitude of plant species rely on ants as their seed dispersers. Many of these plant species are spring ephemerals that take advantage of the fact that there is little else for ants to eat in the early spring by attaching fatty capsules to their seeds that are very attractive to foraging ant species. There are two big players in the foraging ant communities of eastern North America, the warm adapted Aphaenogaster rudis and the cold adapted Aphaenogaster picea. The cold adapted A. picea emerges from winter dormancy early in the spring while the warm adapted species emerges from dormancy much later in the spring. In the southern portions of their range, A. rudis outcompetes A. picea.

What is the big deal? Well, the researchers looked at two plant species that rely on these ants for seed dispersal, Hepatica nobilis and Hexastylis arifolia. Hepatica nobilis sets seed early in the spring, relying on ant species like A. picea to disperse its seed whereas Hexastylis arifolia sets seed late in spring, which is prime time for A. rudis. They noticed that, in the southern portions of their range where A. picea had been displaced, Hepatica has a very clumped and patchy growth habit where farther north it did not. Hexastylis on the other hand seemed to have a more normal growth pattern in the south.

By performing some transplanting and examining foraging and seed dispersal, they found that the absence of A. picea in the south spelled ecological disaster for Hepatica. It continues to set seed but because A. rudis emerges long after seed set, it is not filling the gap left by the missing A. picea. Hexastylis, which only grows in the south and sets seed much later, does just fine with the warm adapted A. rudis. Farther north where A. picea still rules, Hepatica has no trouble with seed dispersal but Hexastylis drops out of the ecosystem entirely. In essence, because of warming climate trends since the end of the Pleistocene, Hepatica is falling out of sync with its mutualistic ant partner in the southern portions of its range and, in time, may become extirpated.

Further Reading:
http://bit.ly/1J4VnN7