Tuesday, July 16, 2013

Elvia Melendez-Ackerman, plant-plant feedbacks



Elvia Melendez-Ackerman, UPR Rio Piedras, gave us a seminar wednesday talking about plant-plant interactions on Mona Island, an island in between Puerto Rico and the Dominican Republic. It's an interesting looking island, without many beaches as you might suspect, the coastline is dominated by jagged looking cliffs, like the photo on your left. There is a cactus, threatened species Harrisia portoriscensis, is now endemic to the island that used to colonize Puerto Rico as well but no longer does. (endemic to = only found in that area, for example, the hellbender salamander is endemic to the eastern US)
For this project, her work, along with graduate student Julissa Rojas-Sandoval, focuses on the interaction between african grass Megathyrsus maximus and H. portorscensis. To begin, they tried to understand first how this flower is pollinated, and which type of pollination, (natural, cross, self, autogamy or agamospermy) produced the highest amount of fruit set. They initially thought that it was a bat or bee pollinated flower, but turns out, after monitering 200 hours of the flower, it was only visited 5 times! So what is driving the pollination of these cacti flowers? Well, turns out it's wind. 

See here, to the left, the cactus has really long flowers, Elvia and Julissa found that on average, they were 21 cm from the main stalk of the cactus, allowing the flower to be out in the open where wind could freely whirl it around. It flowers all year long, yet this species has become extinct in Puerto Rico and is in fear of the same on Mona Island. So the task at hand was to get information on the population, specifically, whether or not it was threatened in Mona Island. Plant censuses brought about interest in the invasive african guinea grass, M. Maximus that was beginning to take over the southeastern portion of the Island. It's no small wonder that it's fire and drought resistant and is taking over. They found that the population is slowly but surely decreasing and that it's likely due to the presence of this invasive grass, but that is still up for debate. Shade was found to affect the juvenile stage of the cacti, specifically, shade from the grass hinders the growth while shade from other plants native to the island does not hinder their growth. It's a strange situation. I thought that the next step in an experiment like this would be to do lab growth of cacti in soils collected underneath different types of plants found on the island. Plant-plant feedback turned plant-soil feedback. Sounds like fun :)

This post is sufficiently late by a week but I've been so busy.. We had a great weekend on the southwest portion of the island, and I will eventually maybe this weekend post about that. I began collecting and processing my samples this week so it has been quite insane.

3 more weeks or so.

Brandy 

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