Taxonomic similarity does not predict necessary sample size for ex situ conservation: a comparison among five genera

Abstract

Effectively conserving biodiversity with limited resources requires scientifically informed and efficient strategies. Guidance is particularly needed on how many living plants are necessary to conserve a threshold level of genetic diversity in ex situ collections. We investigated this question for 11 taxa across five genera. In this first study analysing and optimizing ex situ genetic diversity across multiple genera, we found that the percentage of extant genetic diversity currently conserved varies among taxa from 40% to 95%. Most taxa are well below genetic conservation targets. Resampling datasets showed that ideal collection sizes vary widely even within a genus: one taxon typically required at least 50% more individuals than another (though Quercus was an exception). Still, across taxa, the minimum collection size to achieve genetic conservation goals is within one order of magnitude. Current collections are also suboptimal: they could remain the same size yet capture twice the genetic diversity with an improved sampling design. We term this deficiency the ‘genetic conservation gap’. Lastly, we show that minimum collection sizes are influenced by collection priorities regarding the genetic diversity target. In summary, current collections are insufficient (not reaching targets) and suboptimal (not efficiently designed), and we show how improvements can be made.

Meta‐analysis of genetic representativeness of plant populations under ex situ conservation in contrast to wild source populations

“…Our results also showed that the collection size should be ≥30 or 50, and this is largely consistent with previous studies (Hoban & Schlarbaum 2014; Hoban et al. 2018, 2020). At each ex situ site, mixing collections from different sources within the nearby region is also an effective approach to increase genetic variation.…”

Using botanic gardens and arboreta to help identify urban trees for the future

“…However, this type of research is only possible if curators of collections consider facilitating future research opportunities as a key objective when introducing plant material to a garden. Consideration should also be given to the sampling design of plant collection trips so that a breadth of genetic material is represented in cultivation (Hoban et al., 2020). This will not only support conservation goals but will also facilitate the evaluation of intraspecific trait variability and help provide focus for plant selection.…”

Diversidade genética de Pilocarpus Microphyllus na Flona de Carajás – PA

“…Embora nossos valores sejam menores, Franklin (1980) sugere um Ne igual a 50 para conservação a curto e médio prazo para prevenir a perda de alelos raros, enquanto Hoban et al (2020a) recomendam que para reter o potencial adaptativo de espécies e populações um tamanho efetivo populacional maior que 500 é necessário. O número mínimo de 60 matrizes amostradas para propagação por população está de acordo com outros trabalhos que sugeriram número similares, como entre 30-60 para espécies cultiváveis (MARSHALL; BROWN, 1975), 40-80 para espécies virtuais estruturadas em 4 populações como no Jaborandi (HOBAN, 2019), ou entre 30-200 para 11 espécies de 5 gêneros de angiospermas diferentes (HOBAN et al, 2020b). Esse número de matrizes amostradas por população preservaria pelo menos uma cópia de 95% dos alelos de cada população.…”