Genetic diversity in adult and seedling populations of Primula vulgaris in a fragmented agricultural landscape

Abstract

Habitat fragmentation is known to generally reduce the size of plant populations and increase their isolation, leading to genetic erosion and increased betweenpopulation genetic differentiation. In Flanders (northern Belgium) Primula vulgaris is very rare and declining. Populations have incurred strong fragmentation for the last decades and are now restricted to a few highly fragmented areas in an intensively used agricultural landscape. Previous studies showed that small populations of this long-lived perennial herb still maintained high levels of genetic variation and low genetic differentiation. This pattern can either indicate recent gene flow or represent historical variation. Therefore, we used polymorphic microsatellite loci to investigate genetic variation and structure in adult (which may still reflect historical variation) and seedling (recent generation, thus affected by current processes) life stages. The recent generation (seedlings) showed a significant loss of observed heterozygosity (H o ) together with lower expected heterozygosity (H e ), a trend for higher inbreeding levels (F IS ) and higher differentiation (F ST ) between populations compared to the adult generation. This might result from (1) a reduction in effective population size, (2) higher inbreeding levels in the seedlings, (3) a higher survival of heterozygotes over time due to a higher fitness of heterozygotes (heterosis) and/or a lower fitness of homozygotes (inbreeding depression), (4) overlapping generations in the adult life stage, or (5) a lack of establishment of new (inbred) adults from seedlings due to degraded habitat conditions. Combining restoration of both habitat quality and gene flow between populations may be indispensable to ensure a sustainable conservation of fragmented populations.

Is the post-disturbance composition of a plant population determined by selection for outcrossed seedlings or by the composition of the seedbank?

“…seedling cohorts (Cabin et al, 1998;Asuka et al, 2004;Caldiz and Premoli, 2005;Mandák et al, 2006;Van Geert et al, 2008;Fuchs and Hamrick, 2010). Importantly, majority of these earlier studies used allozyme markers that might have been directly subject to natural selection, although similar patterns have also been observed in later studies using microsatellite markers (for example, Jones and Hubbell, 2006).…”

Contemporary and historic factors influence differently genetic differentiation and diversity in a tropical palm

“…Adults and seedlings can also show distinct responses to habitat loss and fragmentation (Van Geert et al, 2008). Genetic variability and differentiation of adults of perennial plants often show responses to past landscape conditions but not to recent habitat changes (Collevatti et al, 2001;Kramer et al, 2008).…”

“…Genetic variability and differentiation of adults of perennial plants often show responses to past landscape conditions but not to recent habitat changes (Collevatti et al, 2001;Kramer et al, 2008). Nevertheless, several studies found decreasing genetic variability and increasing inbreeding coefficients in the progeny (seedlings), suggesting that there may be a time lag before ongoing habitat fragmentation is observed in the genetic structure of adults (Kettle et al, 2007;Aguilar et al, 2008;Van Geert et al, 2008). Therefore, assessing genetic variability in seedlings instead of adults in fragmented landscapes is useful when evaluating the ongoing effects of habitat loss and fragmentation on genetic variability and differentiation.…”

Genetic Risk Assessment of a Threatened Remnant Population of Hairy Prairie-Clover (Dalea villosa var. villosa) in the Canadian Prairie

“…However, empirical studies of small, isolated populations have yielded variable results [9,12]. Cases have been reported in which fragmented populations of some widespread plant species promoted gene flow and were not detrimental [15][16][17]. Several factors responsible for such discrepancy have been proposed such as interspecific longevity differential, pre-fragmentation abundance, different mating system, the presence of seed banks, and interaction of animal population and seed dispersal [12].…”