Work In Progress:

Robyn J. Burnham

Department of Ecology & Evolutionary Biology

 and Museum of Paleontology

University of Michigan

Contact Robyn: rburnham@umich.edu

 

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Overview

I am interested in the origin, diversification, and maintenance of plant diversity in northern South America. I am concerned about conservation and wise management of ecosystems in tropical areas of the Western Hemisphere, and I approach those ecosystems with goals of identifying processes of diversification, specialization, migration, and distribution of plants.  The organisms I study are climbing plants: vines and lianas.  Rooted at the ground level, but traversing the canopy with the support of trees, climbers have a unique life style that appears to be  sensitive to small and large perturbations.  Recently I have extended my interests in climbers to North America under the CLIMBERS project.

 

Academic Research

My research is focused on several topics (click one to read more):

 

 

Ecology and Systematics of Neotropical Lianas

FOSSIL RECORD of CLIMBERS (FRC) – a database

CLIMBERS in temperate North America

Paleoecology and Systematics of Neogene plants from northern South America

 

 

Ecology and Systematics of Neotropical Lianas

My interests in modern forests have focused on a group of plants that are not phylogenetically allied: the woody climbers, or lianas. Lianas are found in about 140 families of plants and have probably existed on earth almost as long as there were trees up which to climb. Lianas are often excluded from large tree plot censuses (BCI, Yasuní, Pasoh, etc.) because of time and funding limitations involved in these studies. They are often included in smaller area plots but at the diameter limit of >10cm, a large stem for a liana. So we know relatively little about tropical liana communities, compared to tropical tree communities. Lianas contribute roughly 10-35% of the species diversity to tropical and temperate forests (if we count just the woody species), and usually less than 10% of the biomass, based on litter fall or stem diameter estimates.

I have worked primarily in two areas in the neotropics: Yasuní National Park in eastern Ecuador and Madre de Dios Department / Manu National Park in eastern Peru. Both areas are reasonably well-protected parks, with adequate access and biological stations out of which a large group of biologists can work.

In Yasuní, the objectives of my project are:

** provide species lists and identification guides for the lianas of the park

** provide census information on species that are rarely encountered

** determine the pattern of ecological and geographic distribution of liana species in the park: who is the king, who are the oligarchs, and who are the proletariat?

** how are species added and subtracted from communities by human impacts: what matters?

** what is the population structure of the dominant species (Machaerium cuspidatum [Fabaceae] is king) based on analysis of genetic variation among individuals.  I am currently approaching this using AFLP methods (see below under Machaerium project).

** monitor changes over time in forest communities within Yasuní to assess the ecological impact of the current land use practices:   oil extraction by multinational companies, including road construction;  expansion of indigenous populations (both Quichua and Huaorani); and scientific and ecotourism study of forested communities.

In Manu, the project has only just begun:

I intend to duplicate the type of sampling I have undertaken in Yasuní in order to ask similar questions about this analogous forested ecosystem. Once the system of plots is complete, I will compare the known distributions of the various importance classes of lianas (king, oligarchs, and proletariat) both within Manu and then to Yasuní. Although Manu and Yasuní represent similar kinds of physiographic settings: base of the eastern Andes, relatively rich soils, dominated by terra firme habitats, I expect that the lianas will be highly influenced by the individual dynamics of the two systems. Manu forest dynamics may be strongly influenced by an highly-active, migrating river, whereas Yasuní may be more influenced by particularly high turnover.

Sampling Scheme

I have used the following sampling scheme in Yasuní National Park and Manu National Park.

Plots are selected based on prior establishment of one hectare tree inventory plots (dbh > 10cm) censused and maintained by Nigel Pitman (Yasuní) or John Terborgh (Manu). Not all of my liana plots have a corresponding tree plot, but most do. Not all of their tree plots have a corresponding liana plot.

Each one hectare plot is sampled using five 4 x 100m transects. Total sample area = 0.2 ha. If the hectare is set up as 100 x 100, then the transect are located every 16 meters (parallel to one another) within the plot. A few plots are hectares established as 10 x 1000 m plots, and in these cases my five transects are lain end to end for the first 500 meters of the hectare. A sketch of the set up is archived here (as a pdf file).

All lianas > 1cm diameter are counted, identified, collected as necessary, and located within the 10m segment of the transect. Stems are measured at the widest part of the stem, exclusive of abnormal bulges and nodes. Each stem is measured only once, so a great deal of following individual lianas through the forest to determine their point of rooting and connection to other individuals is involved.

Lianas are counted if they enter the transect anywhere from 0 to 2 m in height, such that some stems can be rooted outside the 4 x 100m transect. Lianas are not counted if they are not climbing or dependent on another plant in any way. This eliminates the possibility of preferential recognition of some distinctive species over others. It rarely does exclude some reasonably large (up to 2 cm) stems.

In addition to the counting of all liana stems > 1cm diameter, I keep a tally of all other climbing species less than 1 cm in diameter that I find in the transects. These tallies are kept on a "every 10 m" basis, such that I start a new list every 10 meters of a transect. Although these data cannot be considered quantitative because I do not keep a count of how many stems of an individual species I find every 10 meters, it adds a good sense of the density of the smallest stems and gives me a complete species list per plot.

All data are compiled into Excel worksheets on a per hectare basis, recording stem diameter, names, notes on stem characteristics, and collection status. In recent revisits of plots in Ecuador, I found that I could relocate almost every stem I had originally censused (one year previously), in spite of the fact that I do not mark stems with aluminum tags.

 

 Paleoecology and Systematics of Miocene and Pliocene plants from northern South America

I have two on-going projects (click to see info):

Mio-Pliocene of Bolivia

Miocene of Ecuador

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Mio-Pliocene of Bolivia

We are in the process of getting this web-ready.  For starters take a look at the work Bonnie has done on the dominant Ficus species (pdf). CLICK

 

Miocene of Ecuador

In 1995, I was introduced to the Ecuadorian highlands by vertebrate paleontologist, Rick Madden. He had discovered a wealth of angiosperm fossil plants interbedded with Miocene mammalian fossils in several Miocene basins of southern Ecuador. With an Ecuadorian counterpart, we made a quick trip to the basins of Cuenca, Nabon, Loja, and Giron so that I could get a first-hand look at the outcrops and the potential of the plant fossils there. At the time I was skeptical that I would be interested in any plant fossils that were so young…

The fossils were beautiful, abundant as promised, and I was quickly won over by the interesting questions provided by the physical context of the fossils. By the time the intermontane basins of the Ecuadorian Andes were receiving sediments in their rivers, lakes and swampy areas, the continent had been isolated for at least 40 million years. The rising Andes and potential migration corridors provided to Central America during the later part of the Cenozoic call into question the age of both the extant Andean flora and the northern immigrants that made their way into Amazonia.

Over the past ten years I have collected plant fossils from three of the Andean basins.  Elizabeth Kowalski completed her dissertation on interpretation of paleoclimate, based on fossil plants from the Nabon Basin, while I am slowly working on the taxonomic identities of the 80+ species from the Cuenca and Loja Basins.  The taxonomy of the Nabon Basin has not been properly addressed either, at this point.  A preliminary family list is premature at this point, but keep your browser on this spot — you never know when species identities will fall into place. At least this I can say: In Cuenca we have found abundant remains of fossil palms — palmate palms, as usual. This will help us constrain the temperature to the warmer end of the spectrum. There we also find abundant specimens of the relatively dry forest genus, Loxopterygium (Anacardiaceae).  In Loja we find abundant Tipuana tipu (Burnham, 1995, Amer. J. Botany), a legume that is today found in subtropical Bolivia and northwestern Argentina. The only extant member of the genus is widely planted as a street tree in Southern California! From both Loja and Cuenca we find a large number of other members of the Fabaceae, with leaf sizes ranging from tiny Acacia/Mimosa-like leaflets up to larger Pithecellobium and Inga sized leaflets.

The identification of Miocene fossils from South America should not really be so terribly difficult. They are modern enough that we should find similarities with extant species, and the flora of South America is increasingly better known every day. However, the range of possibilities of species that just might occur at the range of elevation possible at these sites is daunting! We estimate that elevations could have been from 750 to 2000 meters, a range that includes all but those species that only like the Amazonian lowlands or the paramo. The current loss of habitat from these elevations in South America due to habitat destruction, development, landslides, and other human-exacerbated forest loss makes our job just that much harder. As paleobotanists we often feel removed from issues of conservation but this is a concrete example of why even the most academic-minded paleobotanist do take note of the current over-exploitation of natural habitats.

Over 1500 fossils have been collected by our projects in the three Miocene Basins. Roughly 30 localities in each basin have yielded identifiable fossils.

This link will lead you to photos of a few unidentified specimens from the Miocene of Ecuador. Our current guess or more information accompanies each specimen. If you have a suggestion on the identity of any of these, let me know! Please note the EPN number for the fossil you might recognize.

These links will lead you to composite pages of plant morphotypes from the Cuenca Basin of Ecuador. They are pdf files, so use your browser’s back button to return

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Population Structure of a modern Amazonian Liana Dominant: Machaerium cuspidatum

During my work in Yasuní Ecuador, it was clear that one dominant liana could easily be classified as THE KING.  This is Machaerium cuspidatum, a Fabaceae with single-seeded, winged fruits.  Here is a photo of Machaerium cuspidatum in fruit and flower.

 

File written by Adobe Photoshop® 5.2

One of the things that intrigued me was that I had actually rarely seen Machaerium cuspidatum in fruit or flower.  The collections in known herbaria were relatively few, given that M. cuspidatum was the dominant liana, and often the specimens were sterile (not fruits and flowers).  So I started to wonder whether many of the stems of Machaerium might actually be clones.  Lianas certainly do have a high propensity for clonality, and just how extensive that clonal nature might be was unknown. 

There have been some very interesting studies in Mexico on one or two species in which the extent of a single individual is known by laboriously following that individual throughout the forest.  I was hoping for something larger-scale and simpler.

 

It seemed like it might be possible to assess the genetic similarity among ramets using Amplified Fragment Length Polymorphisms (AFLP from DNA).  With a student assistant from University of Michigan, Mr. Ben Oxender , I made about 95 collections of different stems all over Yasuní in September of 2002.  I preserved leaf specimens in silica gel (made herbarium collections of all) and returned the material to Duke University where I extracted DNA from the samples and ran AFLP analyses on them.  The analysis is still underway, but the results are, so far, indicative of a very widely panmictic population, contrary to what I had expected.  We are still analyzing the material and data.  This did not come as a total shock because on one of our last days in the field, Ben and I stumbled upon the Machaerium cuspidatum depicted above and so I could no longer say I had never seen many fruits.  This specimen happened to be on the 50 ha plot administered by the CTFS system, so it is certain to attract some attention there.

 

 

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