Biomedical subjects

P J Wijngaarden

Publications and source records attributed to P J Wijngaarden.

3 recordsLinked to original sources

PubMed2001

Lack of response to artificial selection on the slope of reaction norms for seasonal polyphenism in the butterfly Bicyclus anynana.

The tropical butterfly Bicyclus anynana shows adaptive phenotypic plasticity in response to wet-dry seasonality. The wet season form (WSF) has a conspicuous wing pattern with large eyespots, whereas the dry season form (DSF) lacks eyespots and therefore has a more cryptic appearance. Temperature is the main factor controlling this difference: rearing larvae at a low (<19 degrees C) temperature in the laboratory results in the DSF, whereas rearing at a high (>23 degrees C) temperature induces the WSF. We applied truncation selection in opposite directions in successive generations reared at two alternating temperatures (18.5 degrees C and 23.5 degrees C) to increase (for two High Plasticity (HP) lines), and decrease (for two Low Plasticity (LP) lines) wing pattern plasticity. Plasticity was assessed by partitioning full-sib families over four rearing temperatures (18.5 degrees C, 20.5 degrees C, 21.5 degrees C and 23.5 degrees C). Several wing pattern elements were measured for which the first principal component (PC1) provides a useful summary. The slopes of reaction norms for PC1 were significantly steeper in the HP lines than in the LP lines; however, the selection lines did not always differ significantly from the unselected stock. The results of crosses between the replicates of the selection lines gave no indication for effects of inbreeding. We argue that high, positive genetic correlations across temperatures retard a response to selection in opposite directions in different environments. This is discussed with respect to potential evolutionary constraints in natural populations in these butterflies.

Adaptation, Biological↗

PubMed2000

The genetic basis of eyespot size in the butterfly Bicyclus anynana: an analysis of line crosses.

The tropical butterfly Bicyclus anynana shows wide variation in the size of the eyespots on the ventral side of its wings. Differences in the environmental temperature during late larval and early pupal stages are a major source of this variation, but variation also exists within temperatures. Using lines selected at a single temperature for large and small eyespots, and a number of crosses derived from these lines, we studied the genetic basis of eyespot size in B. anynana. We applied Lande's modification of the Castle-Wright (C-W) estimator to estimate the minimum number of genes contributing to the difference between the two lines. Estimates indicated that at least five genes are involved. As the C-W estimator is based on a number of simplifying assumptions, we tested to what extent one of these assumptions (additive gene action) is actually met. Joint-scaling tests indicated that the assumption of additivity is not satisfied and that dominance and probably epistasis play a role. Because reciprocal crosses were available we looked for evidence for sex-linkage and cytoplasmic effects. No evidence for cytoplasmic effects was found, but the data were consistent with the presence of one or more loci on the X-chromosome. The results are discussed in the context of the current model of eyespot formation.

Animals↗

PubMed1996

Development, plasticity and evolution of butterfly eyespot patterns.

The developmental and genetic bases for the formation, plasticity and diversity of eyespot patterns in butterflies are examined. Eyespot pattern mutants, regulatory gene expression, and transplants of the eyespot developmental organizer demonstrate that eyespot position, number, size and colour are determined progressively in a developmental pathway largely uncoupled from those regulating other wing-pattern elements and body structures. Species comparisons and selection experiments suggest that the evolution of eyespot patterns can occur rapidly through modulation of different stages of this pathway, and requires only single, or very few, changes in regulatory genes.

Adaptation, Biological↗