However, within the studied Hl ‐range, a t test for Ed was highly significant ( p < .001) revealing a true change in SS eye diameter over time. 3.2 Molecular data The analysis with structure based only on microsatellite genotypes yielded highest likelihood for two genetic clusters ( K = 2; Figure A7 ).
Among possible explanations for a proportionally stronger decline in SS , there is no obvious candidate in the data presented by Thörne and Carlsson ( 2004 ), although a slight trend toward increased eutrophication and temporary acidification combined with some changes in the Fegen fish community may have affected Baltic ciscoes negatively.
A series of biplots (Figure A6 ) on morphometric characters ( Hl against Tl and Ed against Hl ) for the recent and historical materials separately showed a trend toward less distinction between SS and AS for Ed over time, particularly in females (Figure 7 ).