Palo Verde Biological Station, Costa Rica

I spent the week at Palo Verde Biological Station in Costa Rica for the OTS Tropical Plant Systematics course. This site is a stark contrast to the high elevation, cool forests at Cuericí, but has a variety of intriguing forests and habitat types. Now the wet season, these seasonally dry forests are green and full of life. 

The biological station looks south on a large marsh, and the Rio Tempisque. One of the class hikes involved examining the diversity of aquatic plants in the waist deep marsh.

Vachellia collinsii (Saff.) Seigler & Ebinger 
This plant is one of many with a fascinating ant symbiosis biology. This provides to the ants food via nectaries on the petiole, as well as a home in the large swollen thorns. These ants aggressively defend their host, and even weed out the competition in the understory. 

Guazuma ulmifolia Lam.
Recently placed in the subfamily Byttneroideae of Malvaceae, G. ulmifolia has peculiar stamen-like filaments that are actually modified petals. Relationships between subfamilies in Malvaceae remains obscure, and there is still much work to be done in this group. 

Polystemma guatemalense (Schltr.) W.D.Stevens

Tomorrow I'll be visiting a mangrove to do some botanizing, before heading to the La Selva Biological Station.