Seed morphological traits as a tool to quantify variation maintained inex situcollections: a case study inPinus torreyana(Parry)

Abstract

PREMISEOptimizing the amount of genetic diversity captured in seed collections is a long-standing objective of ex situ conservation. Particularly for rare species where limited genetic information is available, it poses a significant challenge. However, understanding the within and among population distribution of trait variation within seed collections may provide a means to approximate standing genetic variation and inform conservation efforts.METHODSWe quantified seed morphological variation and seedling emergence both within and among populations for existing seed collections of Torrey pine (Pinus torreyana), a critically endangered pine endemic to California. Using a simulation-based approach, we used estimates of within-population variance to estimate the number of maternal families required to captured 95% of trait variation within each existing seed collection.KEY RESULTSOn average, 21% and 22% of seed morphological variation in Torrey pine was explained by population origin and maternal family within populations respectively. Despite significant morphological differences, seedling emergence was similar across populations. Simulations revealed that 80% and 68% of all maternal families within island and mainland seed collection respectively needed to be resampled to ensure 95% of seed trait variation within existing collections was captured.CONCLUSIONSOverall, these results suggest that substantial structure exists for seed morphological traits both within and between populations. From a conservation perspective, this indicates that to optimize genetic diversity captured in Torrey pine ex situ conservation collections, maximizing the number of maternal families sampled within each population will be necessary.