Our Conservation Effort: Sampling

home Gene Conservation Our Conservation Effort: Sampling

Caption: Difference in size and seed color illustrates the variability that exists within a species.

As mentioned already, Camcore collects seeds from trees that are threatened and plants them elsewhere to protect the populations ex situ. How do we know how many trees to sample per population and how many populations to sample across a species’ geographic range? We have studied the genetic diversity within a population using both chemical and molecular markers and have used this information plus results from field trials (provenance tests) to develop in situ and ex situ conservation strategies.

Caption: Fragmentation large population of Pinus tecunumanii in San Jerónimo, Guatemala

Caption: Fragmentation: a small population of Pinus tecunumanii in Ashigua, Guatemala

As an example, we looked at how gene frequencies varied within a small (5 hectare) and large (200 hectare) population of Pinus tecunumanii in Guatemala using chemical markers called allozymes. Even though the two populations were separated by 65 km, we found that the two populations carried a number of the same major genes. Where they differed was in their composition of rare genes, better known as alleles. Once we knew the frequency of major and minor alleles, we conducted statistical probability simulations to determine how many trees we would need to sample in the large and small population, using actual allele counts from our study, in order to sample all alleles at frequency of 5% or greater. We found that in the small populations we would need to sample about 20 trees, and in the large populations only 10 trees to conserve most of the diversity.

Camcore does much more than this by sampling 20 to 50 trees per population. We sample a number of populations throughout the species’ geographic range to ensure that we are also maintaining broad adaptability.