The Amazing Radiation of Hawaii's Lobeliads

Hawai'i is home to so many interesting species of plants, many of which are found nowhere else in the world. One group, however, stands out among the rest in that it represents the largest plant radiation not just in Hawai'i but on any island archipelago in the world!

I am of course talking about the Hawaiian lobelioids. We are familiar with species found on North America, which include the lovely cardinal flower (Lobelia cardinalis) and the great blue lobelia (Lobelia siphilitica), but the 6 genera that comprise the Hawaiian radiation are something quite different altogether.

Numbering roughly 125 species in total (and many extinct species as well), it was long thought that they were the result of at least 3 separate invasions. Thanks to recent DNA analysis, it is now believed that all 6 genera are the result of one single invasion by a lobelia-like ancestor. This may seem ridiculous but, when you consider the fact that this invasion happened back when Gardner Pinnacles and French Frigate Shoals were actual islands and none of the extant islands were even in existence, then you can kind of grasp the time scales involved that produced such a drastic and varied radiation.

Sadly, like countless Hawaiian endemics, the invasion of the human species has spelled disaster. Hawaiian endemics are declining at an alarming rate. Introduced pigs and rats eat seeds, devour seedlings, and even go as far as to chew right through the stems of adult plants. To make matters worse, many species evolved to a specific suite of pollinators. Take the genus Clermontia for example. The flowers of these species are evolved for pollination by the island's endemic honey creepers. Due to avian malaria and other human impacts, many honey creepers are endangered and some have already gone extinct. Without their pollinators, many of these lobelioids are doomed to slow extinction if they haven't disappeared already. For some, what few populations remain are now fenced off and have to be hand pollinated. As I have said all too often, the future of this great radiation of plants is uncertain.

Photo Credits: Oakapples (http://bit.ly/OjOqhU), Forest and Kim Starr (http://bit.ly/1miCAA5), Dave Janas

Further Reading:

http://bit.ly/2aIviF5

http://bit.ly/2bh9Dpv

http://bit.ly/2b4i5dV

Buffalonut - A Parasitic Shrub From Appalachia

I have a hard time with shrubby species. They just don't stand out to me like herbaceous plants or giant trees. As such, my identification skills for this group of medium-sized woody plants are subpar. However, every once in a while I find something that I can't let go. Usually its a species with a trait that really stands out. This is how I came to know buffalo nut (Pyrularia pubera). Its unique inflorescence was like nothing I had ever encountered before. 

There is good reason for my unfamiliarity with this species. It is largely restricted to the core of the Appalachian Mountains, although there are records of it growing on Long Island as well. Regardless, it is not a species I grew up around. The first time I saw its flowers I was stumped. I simply couldn't place it. Luckily its unique appearance made it easy to track down. I was happy with buffalo nut for the time being but I was surprised yet again when I sat down for a chat with someone who knows woody species much better than I do. 

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As it turns out, buffalo nut belongs to the sandalwood family, Santalaceae. This makes it a distant cousin of the mistletoes. Like most members of this family, buffalo nut lives a parasitic lifestyle. Although it is fully capable of photosynthesis and "normal" root behavior, under natural conditions, it parasitizes the roots of other tree species. It doesn't really seem to have a preference either. Over 60 different species hailing from 31 different families have been recorded as hosts. 

When a buffalo nut seed germinates, it starts by throwing down a taproot. Once the taproot reaches a certain depth, lateral roots are sent out in search of a host. These roots "sniff out" the roots of other species by honing in on root exudates. When a suitable root is found, the buffalo nut root will tap into its host using specialized cells called haustoria. Once connected, it begins stealing water and nutrients. Buffalo nut roots have been known to travel distances of 40 feet in search of a host, which is pretty incredible if you ask me. 

It is easy to look down on parasites. Heck, they are largely maligned as free loaders. This could not be farther from the truth. Parasites are a healthy component of every ecosystem on the planet. They are a yet another player in a system that is constantly changing. What's more, the presence of parasites can actually increase biodiversity in a system by keeping certain species from becoming too dominant. Buffalo nut should not be persecuted. Instead it should be celebrated. It is yet another species that makes the Appalachian Mountain flora so unique. 


Further Reading: [1] [2]

Blowout Penstemon

While living and working in Wyoming, I had the chance to meet so many amazing plant species. Many of these were quite unique to the high desert environments where we were assigned. Countless hours were spent searching large swaths of land rarely visited by humans. One species of plant managed to elude me during my time in that beautiful part of the country. The plant is incredibly rare and thus a focus of federal protection and restoration efforts. 

Based on first impressions, blowout penstemon (Penstemon haydenii) may look like any other penstemon. The similarities stop there and indeed, this is one of the most unique species of penstemon I have ever heard of. Originally it was only known from a few locations in the Sand Hills of Nebraska. Recently, a few populations were discovered in Wyoming but it is by no means common. 

As its common name suggests, P. haydenii is a specialist of blowouts. These depressions in the sand are caused by blustering winds that carve out and remove all vegetation. Most plants cannot survive in these conditions. There is very little water, the sands are constantly shifting, and as the wind kicks up sand at high speeds, the abrasive force can actually cut down frail vegetation. This is where P. haydenii excels. 

It has a thick, waxy cuticle covering its stem and leaves that protect it from this sandblasting effect as well as drought. The seeds of these species are dispersed by wind and have extreme longevity in the soil. They can remain dormant for decades until the right conditions are present for them to germinate. P. haydenii seeds need at least 2 weeks of steady moisture and lots of abrasion from sand in order to break dormancy. Research has shown that these conditions are only ever present one out of every 8 to 10 years. As a result, P. haydenii has a debilitatingly small recruitment window. 

This rarity has placed it on the endangered species list. Ironically, the very regulations that were put into place to control range degradation by cattle ranchers may have caused serious declines in this species. It was once common practice to over-graze the land where P. haydenii is found and as a result, vegetation became sparse. This increased the likelihood of blowout formation, which favored P. haydenii. Fire suppression is another threat. Regular fires help kill back vegetation that would otherwise outcompete P. haydenii

With droughts on the increase and human activities expanding into areas where the few remaining populations of P. haydenii occur, the future of this strange little endemic is uncertain. There has been a lot of effort to save and restore this species numbers but it is by no means the end of the story. Only time will tell...

Photo Credit: Vernon Jenewein Vljenewein

Further Reading:
http://plants.usda.gov/core/profile?symbol=peha12

http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=Q2EX