Source population characteristics affect heterosis following genetic rescue of fragmented plant populations

Abstract

Understanding the relative importance of heterosis and outbreeding depression over multiple generations is a key question in evolutionary biology and is essential for identifying appropriate genetic sources for population and ecosystem restoration. Here we use 2455 experimental crosses between 12 population pairs of the rare perennial plant Rutidosis leptorrhynchoides (Asteraceae) to investigate the multi-generational (F 1 , F 2 , F 3 ) fitness outcomes of inter-population hybridization. We detected no evidence of outbreeding depression, with inter-population hybrids and backcrosses showing either similar fitness or significant heterosis for fitness components across the three generations. Variation in heterosis among population pairs was best explained by characteristics of the foreign source or home population, and was greatest when the source population was large, with high genetic diversity and low inbreeding, and the home population was small and inbred. Our results indicate that the primary consideration for maximizing progeny fitness following population augmentation or restoration is the use of seed from large, genetically diverse populations.

Extent and pattern of genetic diversity in Ethiopian white lupin landraces for agronomical and phenological traits

“…Genetic distance, as good indicator of transgression and heterosis, has been reported by several authors on many crops (Mulugeta et al, 2013;Pickup et al, 2013). Hence, the attempt to cluster Ethiopian white lupin accessions using multivariate analyses, in the present study, is a significant precursor to initiating a white lupin breeding programme.…”

Three types of rescue can avert extinction in a changing environment

“…Such individuals would solve both demographic and genetic challenges faced by the population that is at risk (24). However, such individuals typically are a limiting resource.…”

Genetic rescue versus outbreeding depression in Vallisneria americana: Implications for mixing seed sources for restoration

“…In another study, Pickup et al (2013) found no evidence of outbreeding depression in crosses between pairs of populations across multiple generations, but they did detect evidence of heterosis. In contrast to previous studies, Pickup et al (2013) found that heterosis was not limited to crosses between populations assigned to different genetic regions based on genetic dissimilarity. Therefore, empirical evidence for where natural populations lie along continua of genetic diversity and differentiation, and how that translates into risks for inbreeding or outbreeding depression, is essential to make informed decisions on what restoration stock to use to maximize fitness and long-term population persistence.…”

“…These studies furthermore concluded that spatial autocorrelation and genetic differentiation can be used to determine the optimal distances in which seeds can be mixed for restoration purposes (Forrest et al, 2011;Hufford et al, 2012). In another study, Pickup et al (2013) found no evidence of outbreeding depression in crosses between pairs of populations across multiple generations, but they did detect evidence of heterosis. In contrast to previous studies, Pickup et al (2013) found that heterosis was not limited to crosses between populations assigned to different genetic regions based on genetic dissimilarity.…”

“…Managing the risks of using local or disparate sources of restoration stock, therefore, needs to account for the genetic context of natural source populations. In general, it appears that mixing slightly differentiated, inbred populations can lead to increased fitness whereas mixing extremely differentiated, locally adapted populations can result in outbreeding depression (Forrest et al, 2011;Hereford, 2009;Hufford et al, 2012;Pickup et al, 2013;Waser, 1993). For example, recent studies by Forrest et al (2011) and Hufford et al (2012) found that plants crossed at intermediate-distances outperform within-population crosses in terms of germination success and survival while long-distance hybrids show signs of outbreeding depression.…”