Analysis of the relationship between allozyme heterozygosity and fitness in the rare Gentiana pneumonanthe L.

Abstract

Especially for rare species occurring in small populations, which are prone to loss of genetic variation and inbreeding, detailed knowledge of the relationship between heterozygosity and fitness is generally lacking. After reporting on allozyme variation and fitness in relation to population size in the rare plant Gentiana pneumonanthe, we present a more detailed analysis of the association between heterozygosity and individual fitness. The aim of this study was to test whether increased fitness of more heterozygous individuals is explained best by the 'inbreeding' hypothesis or by the 'overdominance' hypothesis. Individual fitness was measured during 8 months of growth in the greenhouse as the performance for six life-history parameters. PCA reduced these parameters to four main Fitness Components. Individual heterozygosity was scored for seven polymorphic allozyme loci. For some of these loci (e.g. Aat3, Pgml and 6Pgdh2) heterozygotes showed a significantly higher relative fitness than homozygotes. To test the inbreeding model, regression analyses were performed between each Fitness Component and the number of heterozygous loci per individual. Multiple regressions with the adaptive distance of five loci as independent variables were used to test the overdominance model. Only the inbreeding model was a statistically significant explanation for the relationship between heterozygosity and fitness in G. pneumonanthe. The number of heterozygous loci was significantly negatively correlated with the coefficients of variation of three of the six initially measured fitness parameters. This suggests a lower developmental stability among more homozygous plants and may explain the higher phenotypic variation in small populations of the species observed earlier. The importance of the results for conservation biology is discussed.

Isozyme variability of the wetland specialistSwertia perennis(Gentianaceae) in relation to habitat size, isolation, and plant fitness

“…Because reduced leaf size or vegetative plant mass can lead to reduced reproductive success (e.g., Calvo, 1990;Schmid et al, 1994), long-term viability of populations with reduced genetic variability could become destabilized. Indications for positive relationships between population size and genetic variability on the one hand and/or between genetic variability and fitness on the other were found in Gentiana pneumonanthe (Oostermeijer, van Eijck, and den Nijs, 1994;Oostermeijer et al, 1995), Gentianella germanica (Willdenow) Börner (Fischer and Matthies, 1998), Pedicularis palustris L. (Schmidt and Jensen, 2000), Rutidosis leptorrhynchoides (Young et al, 2000), and Ranunculus reptans L. (Fischer, van Kleunen, and Schmid, 2000), but not in Salvia pratensis (Ouborg and van Treuren, 1994), Lychnis flos-cuculi L. (Hauser and Loeschcke, 1994), and Arnica montana L. (Luijten et al, 2000). In L. flos-cuculi only one of four examined populations was small (300 ramets; Hauser and Loeschcke, 1994), and the self-incompatibility system of A. montana may have reduced the importance of inbreeding depression (Luijten et al, 2000).…”

The variability of Gentiana pneumonanthe L. subpopulations in different habitat conditions

“…Other researchers have concentrated on the investigations of the fitness of individuals (Oostermeijer et al 1994b(Oostermeijer et al , 1995a, abundance and structure of populations (Chapman et al 1989;Oostermeijer et al 1992Oostermeijer et al , 1994aOostermeijer et al , 1996Rose et al 1998;Kesel & Urban 1999;Kostrakiewicz-Gierałt 2013), as well as the genetic variability of populations (Raijmann et al 1994;Oostermeijer et al 1995b).…”

Evidence for ancient genetic subdivision among recently fragmented populations of the endangered shrub Grevillea caleyi (Proteaceae)

“…Consequently, in recent years much attention has been focused on the potentially deleterious genetic consequences of habitat fragmentation for plants. A growing body of empirical evidence provides support for some of these predictions (eg, Oostermeijer et al, 1995;Newman and Pilson, 1997;Morris et al, 2002), but many studies have failed to find the predicted consequences of habitat fragmentation (Montgomery et al, 2000), or have even found evidence to directly counter this theory (Foré et al, 1992).…”