Life in the Scrub

Click map above for enlarged image

I spent the first half of 2012 wandering Florida's Lake Wales Ridge, an elevated, sandy spine that runs for 115 miles through the center of the state. A million years ago when peninsular Florida was largely underwater, higher elevations on the Ridge resulted in a series of islands which, now landlocked, are home to a diverse and largely endemic flora and fauna. The fine beach and dune sands laid during the Pliocene underlie a number of distinctive upland habitats on the Ridge and give a desert-like appearance to parts of this strange ecoregion, whose initial harshness belies the beauty and wonder it contains. Exploring the ridge one will cross between these habitats quickly, walking through a field of Hypericum edisonianum in a dry seasonal pond, then fighting your way through a stand of saw palmetto in the mesic flatwoods, and if you brave the near-impenetrable oak thickets of scrubby flatwoods you just might emerge in the delightfully navigable rosemary scrub. Florida scrub is characterized by a paucity of large trees and a dominant shrub layer, with very hot temperatures, quick-draining sandy soils and low nutrient levels creating very trying conditions for any plant and animal life. But it is precisely because of these harsh living conditions that the scrub's flora and fauna have adapted in such fascinating ways.

Hypericum edisonianum, of the Saint John's Wort family, brings large patches of 

brilliant yellow to seasonal ponds at Archbold 

The Florida Scrub Jay (Aphelocoma coerulescens) atop Cari's head is the most famous scrub species, and not only because they're so gregarious. These birds are some of the few known cooperative breeders, with offspring remaining with their parents for several years to assist in raising siblings, watching for predators and defending territories. What makes Archbold jays so amazing is that the ABS Bird Lab has kept track of this population since 1969, and have data on every individual for the past 10 generations! Having such a complete dataset is enough to make any ecologist drool.

 These baby gators were hard to spot!

The Florida scrub is one of the most endangered ecosystems in the country, with urban development and agriculture encroaching on all sides. One of the largest undeveloped tracts on the Lake Wales Ridge is Archbold Biological Station (ABS), a 5,200-acre preserve which retains a variety of Ridge habitats in pristine condition. But ABS is much more than a preserve -- for over 70 years the station has been at the forefront of ecological research, most renowned for their long-term studies in population ecology, conservation biology and pyrogenic system dynamics. Seven research laboratories conduct a number of projects each year (with some data sets extending more than 30 years!) and are headed by top scientists in the field. One of the most phenomenal aspects of ABS is their long-running internship program, which gives aspiring young scientists a chance to work at a top field station while also conducting their own research project, which is a very rare form of employment! I was fortunate enough to have this opportunity, and in February I headed south to begin work in Archbold's Plant Ecology Lab.

The Plant Lab investigating Florida Rosemary (Ceratiola ericoides), adding to an extensive data set on this species' population dynamics going back to 1996. This data allows investigators to look at key demographic rates (survival, recruitment, etc.), analyze its response to fire regimes and climatic variables, and look at populations' spatial distribution.

 Calamintha asheii, a beautiful scrub mint

The ABS plant lab has more ongoing projects than I could list here, but some of the more prominent research areas include long-term demography of scrub endemics, population viability analyses, fire ecology and habitat restoration. From demography of an endangered scrub mint, to germination experiments, to scrub restoration and working to save what is likely the rarest plant in Florida (Ziziphus celata), my internship allowed me to participate in a range of ecological inquiry greater than that experienced by many in grad school! As in all ecology jobs, field work ran the spectrum of exciting to monotonous (counting hundreds of Lyonia stems certainly fell toward the latter), but all of the projects addressed interesting questions, stimulated discussion amongst labmates and made me think about environmental processes at multiple scales. Living and working at a field station like Archbold is a complete immersion in science, and being surrounded by so many brilliant people in such a unique ecosystem for six months was an invaluable period in my ecology career.

 

Florida Rosemary (Ceratiola ericoides) is a fascinating shrub. A dioecious species (plants are either male or female), it is killed by fire but recovers, steadily but slowly, from an established seed bank. In the photo at right, you see the charred "skeleton" of an adult rosemary in the background, and new recruits in the foreground. Because rosemary is allelopathic (producing compounds which inhibit the recruitment and growth of plants surrounding an individual), fires that kill large adult plants enable many endemic and endangered herbs to colonize these recently-cleared patches. As the rosemary population increases, these herbs persist in the gaps between the rosemary plants, but as these gaps close over time the optimal conditions for herb recruitment (low amounts of leaf litter and shrub competition) deteriorate. These gaps are opened again by fire, but wildfire suppression means that historic fire regimes are disrupted; prescribed burns are now necessary to perform this vital ecosystem process. 

Visitors learn about amphibians during the Save the Frogs Day event at ABS (in the background is Dr. Mark Deyrup, head of the Archbold Entomology Lab). Below, you can see one who entered a staring contest with an American Bullfrog (Rana catesbeiana). Two herpetology interns, Jeremy (above-right) and Cori, organized the event, which was a great success! Exposing kids to ecology and fascinating organismal biology at this age is of paramount importance to the conservation movement, and helps ensure an appreciation of the sciences in future generations.

 Watermelon polo at Lake Annie, a 90-acre paradise at the north end of the station.

 Tread-softly (Cnidoscolus stimulosus). Don't let the pretty flower fool you -- as its species epithet implies, the rest of the plant is covered in stinging hairs! Though "stimulating" isn't exactly the adjective I would use...perhaps "painful" or "expletive-inducing"...

A dragonfly larva emerging on Lake Annie 

Above, the larval form of the Echo Moth (Seirarctia echo), whose adult form can be seen below. Quite a striking transformation.

Rhexia mariana, often found in seasonal ponds on the station

A Strangalia strigosa exploring the bloom of a Prickly Pear (Opuntia humifusa). Though this cactus is always a major impediment during scrub travel, its large flowers put on quite a display and attract a host of insects. Opuntia flowers have remarkable thigmotactic (responsive to touch) outer stamens which curl inward when touched (see video below). Though this adaptation has not been thoroughly explained, it has been proposed that it protects the plant from pollen thieves (who don't actually pollinate) and helps to guide actual pollinators past the stigma toward the lower, inner anthers. These anthers hold ~80% of the bloom's pollen and are tightly shielded when the outer anthers curl inward in response to a visiting insect's (or prodding ecologist's) movement.

 A Southern Black Racer (Coluber constrictor priapus) resting in a Lyonia fruticosa

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"The number of species thus far recorded on the Station’s main property includes 21 amphibians, 27 fishes, 44 mammals, 48 reptiles, 208 birds, 593 vascular plants, and more than 6,000 insects and other invertebrates, including the greatest diversity of ants (117 species) known from a single site in North America." -- www.archbold-station.org. Forty-three of these species are listed as endangered or threatened.

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 A nighthawk nest is always a neat find in the scrub, though you're very likely to step on them before you see them! I only found these because I saw the mother bird fly off when I approached. Instead of building nests in shrubs, trees or other vegetation like many birds, the Common Nighthawk (Chordeiles minor) and its eggs rely on crypsis (camouflage) to avoid predation. Unfortunately I don't have a photo of the adult bird to show you, but suffice it to say that you could walk within three feet of them and not take notice. If you get close enough to startle the mother, however, she will often fly off awkwardly, feigning injury, to draw attention away from her eggs.

Tarflower (Bejaria racemosa) puts on a stunning display, its seven petals splayed outward as a bold invitation to pollinators. But don't try to nibble on the flower buds or steal nectar! As you can see in the photos at right and below, several insects have been trapped by the sticky substance that gives this plant its common name. Found only on the outside of the petals, this "glue" deters florivory and perhaps nectar robbing. Though this theory has yet to be tested, this entrapment might also attract spiders and other insect predators, giving the plant a few extra "bodyguards" to deter insect antagonists.

 An American Alligator (Alligator mississippiensis) in the Everglades, ~6.5 ft long

 The Lubber Grasshopper (Romalea guttata) is one of the largest and most distinctive grasshopper species in the U.S. This one is ~3 inches long, with what I think is an egg case on the tip of her abdomen.

 Central Florida has a surprisingly large black bear population, and though I never spotted one in the scrub, their tracks were excitingly frequent.

 This is a prime example of flatwoods, peninsular Florida's most widespread habitat. The understory is dominated by saw palmetto (Serenoa repens), with slash pines (Pinus elliottii) reigning as king (and lone citizen) of the canopy. In natural fire regimes, flatwoods will burn several times per decade; note the char marks on the pine in the photo.

 Robust Blue-eyed Grass (Sisyrinchium xerophyllum) is actually an Iris

Chapmannia floridana is a member of the pea family, whose standard petal color is yellow, as seen above-left. In the photo above-right you'll see a mutant Chapmannia with white petals, induced by changes in the genetic code that controls petal color in this individual's DNA. It is changes like these that drive the evolution of new floral morphs and, over time, species, as both the white mutants and yellow morphs are subjected to selection. An elementary example: Chapmannia is mainly pollinated by Bombus and Augochloropsis bees, who are especially attracted to yellow (and blue). Thus, the regular yellow morph serves Chapmannia well. But if we had an exotic pathogen reduce these bee species' populations, Chapmannia would likely see a consequent reduction in seed production due to decreased pollination. But if the white-petaled mutant successfully attracted an abundant moth pollinator (who are known to be partial to white flowers), we might see the mutant individuals begin to produce more seed than their yellow counterparts, with the mutant now receiving a relatively higher rate of pollination than the yellow morph. Over time, if ecological factors continue to favor the white mutant, we would theoretically see a greater number of white Chapmannias, and their mutualism with moths could result in reproductive isolation from the yellow Chapmannia, the evolution of morphological changes in floral structure to better suit their moth pollinators, and maybe even a new species! Of course, we're ignoring certain key questions like, "Could a moth successfully pollinate a Chapmannia in the first place?" and "Are the genetic changes that give the species white petals linked to any other deleterious traits?", but this simplified example illustrates one of the key mechanisms influencing the evolution of floral traits, pollinator mutualisms.

       Interns! Projects ranged from vegetation structure's influence on avian predation, to spatially explicit fire modeling, to grazing effects on endangered herbs, to anole intelligence, to how scrub jay kinship relates to territorial patterns, and more. Click here for more information about internships at Archbold. 

 In April, the largest delegation of Cuban scientists ever to visit the U.S. came to ABS for two weeks. Amongst other, more academic things, they taught us to salsa.

My independent research focused on the pollination ecology of Lyonia lucida, a common southeastern shrub in the blueberry family. Despite the large floral display of this species, pollinator visits have been noted as surprisingly rare -- actually, almost non-existent. My project investigated this mystery and tested for potential pollination by thrips, miniscule insects often found in flowers. Though I found thrips pollination to be unlikely, preliminary data suggest that we may just not be looking for pollinators during the right time -- there is a whole lot going on out in the scrub at night that we don't know about. I'll be returning to ABS this April to investigate this further; you're sure to see a blog post about it!

 A juvenile Gopher Tortoise (Gopherus polyphemus). Yes, that is a nickel beside him, and yes, it is the cutest thing you ever saw. (The first photo in this post is an adult tortoise.) Like many scrub species, these tortoises burrow to escape the summer heat, winter cold, predation and fire. These burrows can extend over 40 feet and may be over 10 feet below ground level. As you might guess, these large tunnels are important structures within this ecosystem and are known to be utilized by over 300 other species, including the threatened Eastern Indigo snake, gopher frogs, foxes, rabbits, and many more.

Well, it was hard to condense six months of life into one blog post, but then again, this post isn't all that condensed, is it? Thanks for reading; next we'll head to the Southwest and climb some trees!