Supporting long-term sustainability of ex situ collections using a pedigree-based population management approach

Abstract

Premise: Living collections maintained for generations are at risk of diversity loss, inbreeding, and adaptation to cultivation. To address these concerns, the zoo community uses pedigrees to track individuals and implement crosses that maximize founder contributions and minimize inbreeding. Using a pedigree management approach, we demonstrate how conducting strategic crosses can minimize genetic issues that have arisen under current practices.

Methods: We performed crosses between collections and compared progeny fitness, including plant performance and reproductive health. We genotyped the progeny and parental accessions to measure changes in diversity and relatedness within and between accessions.

Results: The mean relatedness values among individuals within each accession suggest they are full siblings, demonstrating that there was high inbreeding and low diversity within accessions, although less so among accessions. Progeny from the wider crosses had increased genetic diversity and were larger and more fertile, while self-pollinated accessions were smaller and less fertile.

Discussion: Institutions that hold exceptional species should consider how diversity is maintained within their collections. Implementing a pedigree-based approach to managing plant reproduction ex situ will slow the inevitable loss of genetic diversity and, in turn, result in healthier collections.

Keywords: Brighamia insignis; genetic diversity; inbreeding; pedigree; pollen viability; strategic crosses.

Figure 1

Plant height (A), pollen mass (B), and pollen viability (C) of Brighamia insignis progeny from a self‐pollination (SELF) and crosses using four different pollen donors (National Tropical Botanical Garden [NTBG], United States Botanic Garden [USBG2, USBG1], and San Diego Zoo [SDZ]) from three different institutions and a maternal plant at the Chicago Botanic Garden. Progeny from the different crosses are ordered by ascending genetic diversity (H _e). The violin plot shows the distribution of numeric data around the mean. The point represents the median, and the wider areas represent a higher density of that variable. nd = no data (i.e., no pollen was produced by SELF progeny plants from which to assess pollen viability).