Location and characterization of CWR populations

Identify and document the target CWR populations

Target CWR taxa must be properly identified and documented. To do this it is necessary to collect herbarium specimens that should be deposited in two well-established public herbaria.

Complementarily or alternatively, you can document your target CWR taxa by sampling and conserving DNA for reference analysis. This will allow expert botanists not only to verify the actual taxonomic identification, but also to review the characteristics of the plants and update the taxon assignation should any revision occur in the corresponding taxonomic group.

Set the limits of the genetic reserve and each target CWR population area of occupancy

The area of the genetic reserve will include the whole area covered by the targeted CWR populations and a buffer area to protect their habitat.

The area covered by the target CWR population refers to the minimum polygon that encompasses all individuals of the populationitself. The best time to determine this area is during flowring season when plants are easier to find. Here is the process:

• Set the real limits of the population. Use flag stakes or similar marking material to mark the flowering individuals that occur at the perimeter of the target population you are working with. It is advisable to walk beyond the perceived limits to make sure that the population does not continue further away.
• Add a buffer zone to the real limits of the target population to protect both the actual CWR population and the associated biota (e.g. pollinators and seed dispersers)

Get the geographic coordinates of the area of occupancy by using a GPS tracker or a smartphone App (e.g. Mobile Topographer). When non of these are available, the accuracy of the delimitation of the area of occupancy can be improved by marking the boundaries with permanent survey marking stakes.

When the genetic reserve comprises various populations of the same target CWR species, the same process can be followed to obtain the area of occupancy of each single population. The total area of occupancy for that target CWR species can then be calculated by adding up all individual ones.

Population census: calculating the size of the population

Determining the population size is essential when characterizing CWR populations as it is a good indicator of its conservation status as well as of its genetic diversity and availability of propagating material for use in plant breeding.

The objetive of the census is to determine the number of reproductive or mature individuals of each target CWR population so the best time to do it will be during flowering season. All flowering or fruiting individuals will be considered as potentially reproductive individuals. However, those individuals without flowers or fruits but showing evidence of having flowered before or likely to flower later in the season should also be included.

Before carrying out a population census it isimportant to study the architecture of the plant to define what an individual plant is going to be. This is usually not a problem in plants that grow a single shoot from their roots. However, it can be confusing for vegetatively propagated adjacent plants when several shoots growing from underground rhizomes, tubers or bulbs intermingle difficulting the definition of a single individual plant. Here, the best approach could be to define an individual plant as a set of shoots (ramets) that grow together below certain distance from each other. Once the surveyors get their eye in, such distance will not have to be constantly measured for each plant.

Carrying out multiple observer sampling trials to determine the rates of observer recording variation and acting to reduce the error will help obtain a more accurate census. The idea is to adopt a pragmatic approach that will be systematically followed through the management of the population.

Methods

When the number of reproductive individuals is manageable the best way to proceed is to carry out a direct censusby counting all individuals one by one. For larger population sizes it is better to replace it for an estimation of the population size through sampling. Find here what to do and how:

A) Direct population census

Carefully scan the population. All reproductive plants must be marked using flag stakes which will then be counted as they are removed. Note that counting plants without previous marking can lead to error by omission or double counting. If possible, use also click counters.

It is essential to be very systematic when doing the counting and also collect all data in an appropiate data sheet.

B) Population size estimation through sampling

There are many ways of estimating the population size through sampling. Find below how to do it by setting a transect, one of the simplest methods:

• Strech a string from one end of the widest side of the population to the other and attach it to steel pegs, for example, at either end. You can use some more steel pegs in between to keep the string in place.
• Then, set a threshold distance along both sides of the string and mark/count all reproductive individuals. The threshold distance will depend on the type of plant (e.g. 1-2 m for herbaceous plants, 3-5 m for small shrubs, 5-10 (20) m for large shrubs)

An alternative option is to set a rectangular plot straightaway and count all individuals within.

Regardless of the option chosen, it is important to georeference the four corners so the same transect or plot can be set up in the future for monitoring purposes.

Finally, calculate the population size in two simple steps. First, estimate the population density. Divide the number of individuals counted by the transect/plot area, and second, multiply the population density by the area covered by the population.

If the population occurs in a heterogeneous habitat with great differences in plant density, you can set one or more rectangular plots in each type of habitat and estimate the density in each of them. Calculate the total population size by adding up all individual habitat census, which at the same time are the result of multiplying density by the area covered by the population in each specific habitat.

Find in Iriondo et al., 2008 or Elzinga et al., 2009 or Iriondo, 2011 (in spanish) some additional easy-to-apply approaches to obtain demographic information of plant populations.