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Monitoring CWR diversity

What is plant population monitoring and why it is important to monitor CWR populations?

Monitoring of plant populations is the systematic collection of data over time to detect changes, to determine the direction of those changes and to measure their magnitude (Iriondo et al. 2008). The monitoring of CWR populations and the habitats in which they occur has specific objectives:

  • To provide data for modelling population trends.
  • To assess trends in population size and structure and to detect changes that may indicate demographically unstable populations.
  • To assess trends in population genetic diversity.
  • To determine the outcomes of management actions on populations and to guide management decisions (Iriondo et al. 2008).
The management and monitoring cycle (from Maxted et al. 2016)

CWR can be monitored at different levels: (a) monitoring of specific target CWR populations conserved in situ (either informally or within formal genetic reserves) (addressed in this section), (b) monitoring of ex situ conserved accessions (addressed here  [2]), and (c) monitoring of higher level indicators of CWR conservation (see Monitoring CWR conservation implementation  [3]).

The aim of in situ genetic conservation of CWR populations is normally to maintain the original levels of genetic diversity in the target populations and to ensure the viability of the populations from a demographic, genetic and ecological perspective. However, where the original status of a conserved population is not at its optimum, or when the population has experienced a catastrophic event, the objectives may concentrate more on achieving specific targets regarding population size, structure and genetic diversity. Therefore, CWR populations need to be monitored regularly to assess any short-term and longer-term changes that could potentially lead to genetic erosion, or even species extinction (see Figure on the right). This information can then be used to help evaluate the effectiveness of management strategies in achieving the initial objectives, and it can also be used to provide supporting evidence to justify maintaining or modifying current management practices (Ringold et al. 1996).

The objectives of the monitoring to be undertaken, and the questions that need to be answered, will determine the appropriate method to use (i.e. whether demographic, ecological, anthropogenic and/or genetic data should be collected to monitor populations). Collection of demographic data is perhaps the most commonly used method for monitoring plant populations. However, in the absence of this type of data, ecological data can be collected in its place to infer population trends. Monitoring using ecological data identifies changes in the physical environment that shape the target CWR population and that affect the dynamics and composition of the living communities with which it is associated. Overall, a combined approach, using demographic, ecological and anthropogenic parameters, is desirable. In this way, the target species is monitored directly, but also the biotic and abiotic conditions and the human activities that might contribute to changes in population dynamics are examined and taken into account. Genetic diversity monitoring programmes may also be carried out. However, given that this type of monitoring requires staff with specific skills, specialized equipment and/or higher financial resources, it is recommended that it is only performed if needed, i.e. to answer very specific questions regarding population health and persistence in nature.

The table below provides an overview of these monitoring methods. For each method it outlines its main strengths and constraints, the representativeness of the sampling, its replicability and its sustainability in terms of long-term monitoring programmes.

Comparison of methods for monitoring of CWR populations.

In all cases, an efficient monitoring method for CWR populations or habitats should be reliable (will not lead to false conclusions), powerful (sensitive enough to detect changes) and robust (measurement techniques provide data that are independent of the technique used) (Brady et al. 1993). Finally, a monitoring programme should be able to distinguish between the significant biological changes that negatively impact target population health and normal seasonal variations that need not trigger changes in management.

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