Monotropaceae

This plant grows in the highland oak forests of the Talamanca mountain range in Costa Rica, at about 2700m altitude. While I don’t have a positive ID on the photo, the plant most likely belongs to the family Monotropaceae, the Indian Pipe family. Some taxonomists consider Monotropaceae a subfamily of Ericaceae (this was the family featured in my last post, which contains blueberries and cranberries).

Most monotropes are mycoheterotrophs. This means they parasitize fungi. In some cases, these same fungi parasitize the roots of other plants. For this reason, monotropes are often called ‘epiparasites’. Monotropes cannot photosynthesize on their own and depend entirely on fungi for nutrients and sugars. Moreover, there is evidence that monotropes are specialized, in that each species can parasitize only a narrow range of fungal species (Cullings et al. 1996, Kretzer et al. 2000).

The structure pictured here is called an inflorescence. It consists of a compact group of small white flowers. It is the only part of the monotrope that can be seen above ground. Like fungi, the monotropes spend most of their life cycle underground and only emerge for the purpose of sexual reproduction.

This plant from Costa Rica closely resembles Pleuricospora fimbriolata, the fringed pinesap, which is found in pine forests on the west coast of the United States.

References:
Cullings, K.W., T.M. Szaro and T.D. Bruns. 1996. Evolution of extreme specialization within a lineage of ectomycorrhizal epiparasites. Nature 379:63 – 66.

Kretzer, Annette M., Martin I. Bidartondo, Lisa C. Grubisha, Joseph W. Spatafora, Timothy M. Szaro and Thomas D. Bruns. 2000. Regional specialization of Sarcodes sanguinea (Ericaceae) on a single fungal symbiont from the Rhizopogon ellenae (Rhizopogonaceae) species complex. American Journal of Botany 87:1778-1782.

Ericaceae

Today’s 'plant' of the day is one of my favorite families, the Ericaceae. Blueberry bushes are among the 4000 species included in the Ericaceae. Other familiar plants like cranberries and rhododendrons are also found here. The family is worldwide in distribution, but its center of diversity is in the American tropics. Most members of this group are small bushes or shrubs that do well on acidic soils. The flowers often have a bell or urn shape. Leaves are often small and thick, adapted for dry conditions.

The plants pictured here are from Costa Rica. They grow above 3000m altitude (9000 feet) and are often pollinated by hummingbirds or bumble bees (usually Bombus epiphiatus - a VERY cute bee, but that's a whole other story...)

Ericaceae are most diverse in the Andes, with the highest species numbers in Colombia and Ecuador between 1000m and 3000m (Luteyn 2002). 70% of the genera and 94% of the species of Ericaceae are native to the Neotropics.

One remarkable aspect of Ericaceae is their symbiotic relationship with mycorrhizal fungi. In the case of Andean Ericaceae, the fungi are mostly basidiomycetes. They form a sheath around fine rootlets and aid the plant in deriving nutrients from poor, acidic soils (Setaro et al 2008).

The first photo on this post is wild blueberry (Vacinium sp.) from the paramo of Costa Rica. The second photo is Pernettia sp., also found on the paramo. It is smaller than Vacinium and produces tiny red fruits that are edible and taste great.

References:
Luteyn, JL. 2002. Diversity, adaptation and endemism in the neotropical Ericaceae: biogeographical patterns in the vacciniaea. Botanical Review. 68(1):55-87.

Setaro, Sabrina, Kathleen Kron and Ingrid Kottke. 2008. Neotropical Ericaceae and their mycorrhizal fungi. Botany Without Borders. University of British Columbia, Vancouver, BC. July 26-30.

Plant of the Day: Asteraceae (Compositae) in the Paramo

This Asteraceae is found in the highlands of Costa Rica around 3000m (or about 9000 feet). In tropical countries like Costa Rica, the ecosystem at this elevation is known as ‘paramo’. Paramo is characterized by dense shrubby plants with leaves and flowers adapted to endure extreme conditions. Temperatures can be relatively warm during the day, but they can drop precipitously within hours and fall below freezing at night. Although it rains often in the paramo, whenever the tropical sun shines at these altitudes desiccation is a real danger. Many creatures of the paramo exhibit adaptations that allow them to endure these extreme fluctuations on a daily basis.

I took this photo near Cerro de la Muerte, one of the highest peaks of Costa Rica. Unfortunately, I have not yet found a genus or species name for this flower, but I posted it anyway because it exhibits some of the very interesting adaptations that typify the paramo.

The plant grows very low to the ground, which keeps it out of the wind and helps conserve heat and water. Another adaptation for conserving water is the presence of succulent leaves.

For me, the most interesting adaptation shown here is the structure of the flower. The petals of this plant are reflective. In the photo they look whitish, but are in fact silvery. These reflective petals produce ‘hot spots’ in the center of the flower that are thought to provide a unique reward for insect pollinators. The plant produces no nectar, but instead offers a mini-sauna where the insect gets to warm up while it gathers pollen.

For a similar story about a related plant, there is an article on insect pollination and heliotropism in the paramo available on JStor at www.jstor.org/pss/2989741

If you’d like to know more interesting facts about the paramo and see some of the plants that inhabit it, check out the website of the Missouri Botanical Garden at http://www.mobot.org/MOBOT/research/paramo/welcome_english.shtml

Welcome to the blog ‘Expeditions: exploring environment and politics for the new millennium.’
The purpose of this blog is simple. It’s a place to express ideas. As a biologist by training and a writer at heart, I am most interested in issues connected to the environment, the natural world, and the political, economic and social forces that shape our present and determine our future. If you share an interest in these issues, I invite you to read what I have to say, and I would very much like to hear about your own experiences and insights.

This blog of mine will probably seem a bit scattered, with topics running the gamut from the natural history of some obscure tropical spider to informal time-to-get-on-my-virtual-soapbox moments when political events fire me up. I can’t guarantee a whole lot of answers, but I certainly intend to raise a lot of questions.

This is the first time I’ve put together a blog, so I’m going to ask for your patience as I figure things out. I believe I’ve set this up to allow readers to make comments on my posts, but the mechanics may not work the way I expect them to, at least not during these first few months.

Thanks for taking the time to visit this site, and please come back soon as more posts will follow shortly.

Photo: Lookout on the oak forest trail near Cuerici Biological Station, Costa Rica.