The relationship between flower size, inbreeding coefficient and inferred selfing rate in British Euphrasia species

Abstract

The genus Euphrasia in Britain comprises a taxonomically complex group of self-compatible, morphologically similar, hemi-parasitic, annual plant species of high conservation importance. The 19 diploid and tetraploid taxa currently recognised show striking variation in flower size. The objective of this paper is to determine whether a relationship exists between flower size and breeding system within Euphrasia. Following a survey of flower size variation among the 19 taxa, seven diploid populations, encompassing a broad range of flower sizes, were selected for detailed study. Four nuclear microsatellite loci were used to estimate the inbreeding coefficient F is within each population. F is values varied from to 0.17-0.77 and showed a significant, negative correlation with flower size. These results are best explained as the consequence of variation in selfing rate among the Euphrasia populations, with selfing rate increasing as flower size decreases. The potential factors influencing breeding system evolution in Euphrasia are discussed, together with the role of autogamy in generating taxonomic complexity and facilitating lineage differentiation within the genus. Heredity (2005) 94, 44-51.

Nunatak survival vs. tabula rasa in the Central Pyrenees: a study on the endemic plant species Borderea pyrenaica (Dioscoreaceae)

“…This is a surprising finding for a dioecious long‐lived perennial herb in which selfing is prevented by dioecy. High F IS values could be related to the presence of null alleles (French et al. , 2005); however, this does not hold true for B. pyrenaica , as no null homozygotes were detected at any of the microsatellite loci from the 804 individuals analysed.…”

Outcrossing rates in two self‐compatible, hybridising Rhinanthus species: implications for hybrid formation

“…Larger plants produce several flowering branches, and this strongly increases the number of simultaneously open flowers, thereby increasing the opportunities for geitonogamous selfing. We did not collect data on plant size, but in Euphrasia, no correlation was found between display size and F IS as a measure of selfing rate (French et al 2005). More surprising is the fact that one individual R. minor plant had an outcrossing rate of 0.41, overlapping with two R. angustifolius plants at the low end of the range of that species.…”

“…Larger plants produce several flowering branches, and this strongly increases the number of simultaneously open flowers, thereby increasing the opportunities for geitonogamous selfing. We did not collect data on plant size, but in Euphrasia , no correlation was found between display size and F IS as a measure of selfing rate (French et al. 2005).…”

Effects of plant sex on range distributions and allocation to reproduction

“…In addition, they have little need to attract pollinators to export pollen (Bell, 1985). Experimental tests of this aspect of sex allocation theory within (Schoen, 1982;Mazer et al, 1999; but see Mazer et al, 2007) and between (Cruden & Jensen, 1979;Ritland & Ritland, 1989;Parker et al, 1995;French et al, 2005) species generally support predictions. However, tests of this theory in a macroevolutionary context using molecular-based estimates of selfing rates and phylogenetically explicit analyses are rare (Michalski & Durka, 2009).…”