Sources of Variation in Reciprocal Herkogamy in the Distyly Floral Syndrome of Linum tenue (Linaceae)

Abstract

Premise of the Research: Distyly is a floral polymorphism involving reciprocal herkogamy shaped by selection for pollen transfer efficiency. The variation of the floral organs involved in pollen transfer can be individually affected by environmental and genetic sources of variance, but the organ development will be canalised to minimize reciprocal inaccuracy between anthers and stigmas as this is the focus of selection.Methodology: We measured floral organ and cell length of both morphs of distylous Linum tenue (Linaceae) at different developmental stages of field-and glasshouse-grown plants. We analysed the results to measure reciprocal inaccuracy and identify sources of variance.Pivotal results: Flowers from the field were larger than those from the glasshouse due to both environmental and genetic (population) factors. Pistil and stamen length in adult flowers correlated with flower size, but reciprocal herkogamy was mostly invariant to the size individual floral organs. The length of short floral organs showed greater maladaptive bias, while the length of tall organs showed greater imprecision. During development, the pistils of pin flowers grew at a faster rate than in thrum flowers mostly due to cell elongation, while cell division was more important for male organ height.Conclusions: Distyly in L. tenue involves the interaction of multiple coordinated developmental and environmental mechanisms leading to limited but predictable patterns of variance in the expression of reciprocal herkogamy.

Incomplete partitioning of pollinators byLinum suffruticosumand its coflowering congeners

“…Similar differences have been found in other Mediterranean species in the Iberian Peninsula (Herrera, 1988;Gómez et al, 2007Gómez et al, , 2014. The diversity of visitors agrees with reports on other Linum species (Kearns, 1992;Simbaña and Tye, 2009;Seçmen et al, 2010;Harris and Koptur, 2022;Foroozani et al, 2023), although L. pubescens was visited almost entirely by Usia flies (Johnson and Dafni, 1998;Lebel et al, 2018). In our study, comparing floral visitors between Linum species from coflowering localities provided useful information about pollinator sharing and the potential for pollen transfer between species.…”

“…Reproductive interference could lead to lower inaccuracy and higher reciprocity, as observed in the short reproductive organs in coflowering localities. The current reports for heterostylous species show that there is a tendency of lower inaccuracy values for short organs, a pattern attributed to developmental variation, which is often smaller in short organs (Faivre, 2000;Faivre and Mcdade, 2001;Armbruster et al, 2017;Jacquemyn et al, 2018;Matias et al, 2020;Furtado et al, 2021;Foroozani et al, 2023). In the future, the combination of flower morphology data and pollen transfer rates from more populations will help in testing these hypotheses.…”

Development of microsatellite markers for sister species Linum suffruticosum and Linum tenuifolium in their overlapping ranges

“…These SSR markers will be a useful tool to investigate the mating patterns within and between L. suffruticosum and L. tenuifolium in their contact zone, and patterns of gene flow and spatial genetic structuring among and within pure and mixed populations. The genus Linum has been the object of renewed attention for the study of heterostyly, from macroevolutionary patterns [ 5 , 6 ] to finer scale processes within or across Linum species and populations [ 2 , 29 ], and polyploidy [25, Valdés et al, under review]. Given the full transferability success shown, these SSR markers could potentially be applied to other Linum species for studies of ecological genetics.…”