The invasive Beaver Castor canadensis in Tierra del Fuego Archipelago: a mitochondrial DNA and spatial genetic structure analysis for controlling population expansion

FASANELLA MARIANA; LIZARRALDE MARTA SUSANA

Invasive species: Threats, Ecological Impacts and Control Methods

Nova Science Publishers

Año: 2012; p. 101 - 122

The Tierra del Fuego Archipelago (TDFA) contains numerous invasive species, of which Castor canadensis is the most abundant and important invasion. Beaver are responsible for the most drastic landscape alteration in Tierra del Fuego since the last glacial age, affecting not only the hydrology and composition of the southern beech forest, but more importantly allowing other exotic species to invade the ecosystem. From 25 pairs intentionally released in 1946, beavers have increased their numbers to a current population size of aprox.100,000 individuals. Here, we present the genetic variability and population structure of 222 mitochondrial DNA beaver samples. We detected 7 D-loop haplotypes, 3 of them resulted the most abundant and distributed all along the archipelago. To analyze the data, ATDF population was subdivided into five subpopulations and a slight structure was found (Fst =0.169). With these data we also identify management units (MUs) of the invasive beaver in the ATDF. Although, sea water and mountains could be considered barriers for beaver’s dispersion, we found no barriers to gene flow within the Isla Grande (IG), which may be due to the complex stream watershed network that allows beavers to easily disperse. These results indicate that the IG is a single management unit (MU) and every small island in the archipelago is a separate MU. It is important to consider that successful eradication programs of mammals always were conducted in small islands while invasive populations on larger islands or those that display no distinct structure are more problematic, so the eradication of Castor canadensis in the ATDF would be logistically very difficult or perhaps impossible. Therefore, we propose to (1) control the expansion from IG population to others areas through trapping beavers and (2) eradicate beaver populations of the adjacent small islands (small area comparative to IG) and especially from the continent. If the species is not early removed in the mainland, beavers will begin to invade the Patagonian forests very quickly and its future eradication in these continental areas will be almost impossible. To carry out the control of the species in Tierra del Fuego, is necessary to promote beaver extraction through the commercial trapping in a way to control this species in the short term. To achieve this important point, the classic control scheme must be change it stimulating new business development by incorporating new materials and products to market and also coordinate the participation of public and private actions to exploit species under control. In this work, we state three options for economic use of the beaver: 1) the government could pay a price for killing beavers, 2) to sell/export the beaver fur and 3) to sell beaver´s meat for human consumption. With these three options of beaver exploitation, we believe that the IG control may be feasible and logistically possible.