– in biology an organism occurring in only a specific region or environment, being naturally absent from all other locations.
The last week or so has been quite busy with starting on field work and traveling to another island. But the constant theme in all of this is the endemic species of plants and animals that we see. It’s really why we are here and why biologists want to study in the Galapagos Islands. Of course being restricted to only one place has its troubles too and thus most studies on the evolution of endemic species by necessity have a component on conservation.
After some wait all the permitting came through and I’m able to go in the field and start collecting of samples. Most of this is being done with my principal collaborator Dr. Gonzalo Rivas of the Universidad San Francisco de Quito. My work in endemic Amaranthaceae is contributing to a larger project he is spearheading on detailed characterization of plant communities and long-term monitoring of plant species of special interest. The research is based on a series of vegetation plots set up in different habitats around the islands in which basic species data and measurements associated with biomass are collected. This is combined with detailed aerial photos obtained from a drone to more extensively characterize the area. Monitoring of individuals in plots will take place in 5-10 years to understand individual persistence and recruitment – important aspects for understanding vegetation dynamics in response to changes in climate, management, and biotic interactions.
In addition to providing assistance with plot establishment (not necessarily my favorite part – taking DBH measurement of cactus trees is a little, well, prickly) my major focus is on understanding the unique evolution and current conservation status of some of the endemic members of the family Amaranthaceae. In terms of species diversity the family Amaranthaceae is the fourth most species-rich vascular plant family in the Galapagos archipelago. While relatively diverse they are not however a dominant form of vegetation in terms of numbers (expect for some members of Alternanthera [A. filifolia and A. echinocephala]) and most are quite rare only occurring in very restricted locations or habitats and many are considered endangered. Five extant genera contain endemic species and three of these are particularly unique either for the number of forms they have developed or for the vastly divergent forms from their continental ancestors the plants have evolved.
Alternanthera is the most species-rich genus with 9 species and 7 subspecies. Among these is a mix of widespread and highly localized taxa. As is seen in a number of endemics just because you are endemic does not make you very rare – at least in your specific habitat. This week I got to see the species Alternanthera flavicoma which is endemic to a small area around one bay on the west side of the island of San Cristobal. You can find it growing naturally in old weathered lava flows but it’s also used in town as a common garden planting – and has been trimmed into topiary – I think the only such example of this horticultural use for an Amaranthaceae I have ever seen!
Froelichia, the subject of most of my studies, is represented in the islands by 2 species and 5 subspecies. Its habit is particularly unique. I’ve seen the genus from the northern United States to Paraguay and on the continent they are all pretty similar – taprooted annuals (in the north) and taprooted perennial herbs in the tropics and subtropics. But here they can be sprawling shrubs over a meter in height to 3 meters in width with large woody “trunks”. Here is a slightly better photo of Froelichia juncea subsp. alata endemic to the island of Santa Cruz (I had promised a better photo – this is getting there – it’s just not very photogenic and I’m not a really good photographer either).
The last of the particularly interesting Galapagos Amaranthaceae is the genus Lithophila which is currently represented by two species (although stay tuned as I think there may be more variation than had previously been recognized). The genus has a very unique form and is quite rare. It was greatly affected by introduced goats which apparently decimated its populations, particularly on the islands of Floreana and Santiago. With the control of these introduced herbivores the plants seem to be recovering.
Outside of work related endemics we have had the chance to see a few others as well. On San Cristobal we visited the breeding laboratory from the Galapagos National Park focused on the reestablishment of the endemic tortoise Geochelone chatamensis. This species was greatly reduced in numbers due to direct exploitation for meat and oil, habitat change, and the effects of introduced animals including feral dogs and goats. Here eggs are kept protected and the young are kept in pens for 5-6 years to protect them from threats in the environment. As they grow they are transferred to larger protected areas until they are large enough to not be threatened in the wild. At that point they are transplanted outside of the breeding area. Such a conservation project is not for the impatient. Tortoises take about 20 years to reach sexual maturity and can probably live about 150 years if not more. Seeing the young of 1-2 years and knowing that if they survive they will surely outlive you and your children gives a sobering yet hopeful feeling. Our conservation efforts can make a difference if we realize our folly before it’s too late to act.
We’ve continued to have encounters with other Galapagos endemics. The Galapagos Sea Lion (Zalophus wollebacki) was I think our favorite on San Cristobal. You can see them all over the islands but they were particularly abundant there.
Darwin’s Finches continue to be a favorite to see. And it probably doesn’t hurt that both Aurea and I have been reading the book “The Beak of the Finch” – a very good non-technical read on evolutionary biology, particularly clearly visible instances of natural history focusing of course on Darwin’s Finches.
As we’ve spent lots of time by the beach and wanted something different, we spent a day climbing into the highlands of the island of Santa Cruz. These highlands consist mostly of a community type known as the Miconia zone due to the abundance of the endemic species Miconia robinsoniana (Melastomataceae). Trails lead to two high points, El Puntudo and Cerro Crocker. We went to old volcanic cone of El Puntudo which was a great walk. While not always clear due to frequent clouds in the highlands the day we went was clear allowing for a view out to the ocean. It is a wonderful break from the heat of the coast and surprisingly there are very few people – we only saw a couple people, all from the local area during the entire day. Due to the wetter climate and presence of more soil in the highland regions these areas historically suffered more impact from man. While now mostly protected there are more invasive plant species in this region and species such as Chinchona succiruba (Quinine), Psidium guajava (Guava), and Rubus niveus (Mora) are particularly troublesome and difficult to control.
Above the Miconia zone there is a small zone known as the Pampa or Fern Sedge Zone. Here there is little tall vegetation and an abundance of ferns and mosses.