Effect of quantity and quality of environmental stress on multilocus heterozygosity-growth relationships in Eisenia fetida (Annelida: Oligochaeta)

Abstract

The effects of environmental quantity (moderate soil moisture vs. low soil moisture) and quality (low soil moisture vs. low temperature) on multilocus heterozygosity (MLH)-growth relationships were tested in the earthworm Eisenia fetida. The control treatment was high soil moisture and high temperature. Fresh weight was measured weekly for 4 weeks; MLH was computed for eight polymorphic loci. Moderate moisture limited growth (change in fresh weight) to 50 per cent of control growth; both low moisture and low temperature limited growth to 25 per cent of control growth. MLH was not correlated with growth at any time in the control treatment. MLH was strongly correlated with growth (P < 0.01) in three out of four weekly intervals in the moderate moisture treatment; MLH was weakly correlated with growth (P < 0.05) in two out of four weekly intervals in the low moisture treatment. MLH was not correlated with growth at any time in the low temperature treatment. Moderate soil moisture produced significantly stronger MLH-growth relationships than high moisture or low temperature. Even though low soil moisture and low temperature depressed growth to the same extent, the former produced MLH-growth relationships whereas the latter did not. Thus both environmental quantity and quality affected the existence and recurrence of MLH-growth relationships.

Ontogenetic change in relative performance of allozyme genotypes influences detection of heterosis in the earthworm Eisenia andrei

“…Significant MLH-fresh weight relationships were only detected at the beginning of the life history (a negative correlation), and toward the end of the life history (positive correlations) for individuals pooled among environments. These patterns also differ from those studies that showed significant MLH-growth correlations early in ontogeny (about weeks 2-4) for this species (Audo and Diehl, 1995). The current patterns are compatible however with the selection reversal hypothesis of Gaffney et al (1990) to explain the frequent association of a heterozygote deficiency and heterosis in natural populations of marine bivalves.…”

“…Similarly, Pecon Slattery et al (1993) reported a significant relationship between heterozygosity and age class in the hard clam Mercenaria mercenaria, but the relationship was not consistent over a 3-year sampling period. Consistency of MLH-fitness relationships has also been lacking from a series of studies on Eisenia andrei (Diehl, 1988;Audo and Diehl, 1995;McElroy et al, 1999;McElroy and Diehl, 2001), although some of this inconsistency disappears when a common set of loci are used (Audo and Diehl, 1995). In the above studies, inbreeding, migration, selective mortality, and ontogenetic effects may have affected heterozygosity-fitness relationships.…”

“…Multilocus potence indices were averaged among loci for each week during ontogeny and were treated statistically as above. For comparison, correlations between MLH and fresh weight were also computed for each sample date as discussed by Audo and Diehl (1995). Where appropriate, corrections for Type I errors were made using the sequential Bonferroni test (Rice, 1989 …”

Genetic diversity-fitness correlation revealed by microsatellite analyses in European alpine marmots (Marmota marmota)

“…GDFC remains difficult to investigate in the wild, and few studies have considered ecological variables in their analysis. However, there is some evidence that GDFC may be related to the harshness of the environment (Danzmann et al 1988;Dudash 1990;Borsa et al 1992;Audo and Diehl 1995;Meagher et al 1997;Crnokrak and Roof 1999;Lesbarre`res et al 2005). In this context, the alpine marmot is particularly interesting because populations occur in high alpine meadows, and must cope with a harsh climate and occasionally stressful conditions.…”

The relationship between genetic variation and fitness in chinook salmon, Oncorhynchus tshawytscha (Walbaum): Implications for aquaculture and evolutionary theory.

“…There is considerable evidence to suggest that genetic variation and fitness relationships may be more apparent under stressful conditions (Samollow and Soule 1983;Mitton and Grant 1984;Gentili and Beaumont 1988;Ferguson 1990;Borsa et al 1992;Audo and Diehl 1995;Pogson and Fevolden 1998;Vazquez-Dominguez et al 1998), although too much stress has also been shown to suppress such relationships . W hether the fish in this study existed under 'stressful' conditions is unknown; however, various hatchery practices are known to induce stress responses (e.g., Sharpe et al 1998 Fourth, non-genetic maternal effects could mask genetic variation-fitness relationships.…”