Figure 3.1 – Genetic analysis can help quantify whether a conservation collection holds the majority of genetic diversity of a wild population. Griffith et al. (2015) compared the number of alleles measured in 10 microsatellite markers of the cycad Zamia decumbens to the numbers captured in 205 ex situ plants held in botanical garden collections. A single-accession collection (smallest points) would capture between 27% and 57% of in situ alleles, while the entire ex situ collection (7 accessions, 205 plants) captures 78% of wild population alleles.
The general rationale is that in highly outcrossing species with extensive gene flow (large neighborhood size), populations are more similar (so one can collect from fewer populations). Whereas in a selfing species or one with limited gene flow (small neighborhood size), we expect populations to be very different, therefore we advise collecting from more populations.
Outcrossing leads to higher diversity within a population than across populations, so focus collection efforts on collecting more individuals within a population. In a highly selfing species, you expect individuals to be similar, so you might be fine to collect from fewer individuals.
– Kay Havens
Figure 3.2 – Summary of Collecting Recommendations for Numbers of Populations to Sample. CPC recommends collecting from at least 5 populations across the range of a species. You can use the row factors in this figure to refine your decision. If any of the row factors falls into the red zone, we recommend collecting from all populations. If factors fall into the yellow or green zone, then it is reasonable to collect from fewer populations. (Adapted from Falk and Holsinger 1991.)
Figure 3.3 – Summary of Collecting Recommendations for Numbers of Individuals to Sample within a Population. CPC recommends collecting from 50 unique maternal plants within a population. You can use the row factors in this figure to refine your decision. If any of the row factors falls into the red zone, we recommend collecting from all individuals. If factors fall into the yellow or green zone, then it is reasonable to collect from fewer individuals. (Adapted from Falk and Holsinger 1991.)