Genetic and Environmental Influences on Partial Self-Incompatibility in Lythrum salicaria (Lythraceae)

Abstract

Premise of research. Angiosperms are commonly classified as self-incompatible or self-compatible. This dichotomy has influenced research on the ecological and demographic consequences of colonization because of the predicted benefits of self-compatibility for establishment at low density. Some individuals of self-incompatible species, however, exhibit partial self-incompatibility (PSI), meaning that they set variable amounts of seed following self-pollination. Here, we investigate genetic and environmental components of PSI in tristylous Lythrum salicaria as a context for understanding colonization and the floral morph structure of invasive populations. Methodology. We surveyed variation in PSI using experimental self-and cross-pollinations on plants (n p 338) grown under glasshouse conditions. We compared the stability in expression of PSI over 2 yr (n p 80), and by pollinating selected clones (n p 12) grown under wet and dry conditions. We compared the compatibility status of mid-styled parents (n p 14) and their selfed offspring to determine whether there was a genetic component to PSI and whether the expression of PSI, measured as fruit set after self-pollination, differed between segregating long-and mid-styled plants. Pivotal results. Approximately 34% of plants set seed following self-pollination. The mid-styled morph produced more fruit following self-pollination in comparison with the remaining morphs. An index of self-compatibility (ISC) exhibited significant repeatability for individual plants over two successive flowering seasons. There was no systematic influence of wet and dry growing conditions at flowering on PSI, but significant genetic differences among clones in overall expression of PSI were evident. A heritable component to PSI was confirmed by parentoffspring regression, and compatibility values were significantly higher in mid-versus long-styled progeny. Conclusions. Our study demonstrated a weak but significant genetic component to morph-specific variation in PSI. The capacity of the M-morph to set seed after selfing may enable individuals to found populations and contribute to the occurrence of dimorphic populations missing the short-styled morph in the invasive range of L. salicaria.

The influence of floral morph ratios and low plant density on mating and fertility in a tristylous colonizing species

“…Among our study populations, population sizes ranged from 8-187 individuals with a wide range of morph frequencies (Table 1). Second, controlled pollination studies have consistently revealed that L. salicaria exhibits partial trimorphic incompatibility, with plants of the M-morph more often self-compatible and those of the S-morph most strongly self-incompatible (Darwin 1864;Stout 1923;O'Neil 1994;Mal et al 1999;Colautti et al 2010;Balogh and Barrett 2018). This variation in demography and incompatibility expression raised the question of whether these features might influence patterns of mating and fertility.…”

“…Populations of L. salicaria are commonly tristylous and the species possesses a trimorphic incompatibility system that generally prohibits self-and intramorph fertilization. However, populations commonly exhibit partial self-incompatibility, with the M-morph displaying the weakest incompatibility and the S-morph the strongest, based on controlled self-and cross-pollinations (Darwin 1877;Colautti et al 2010;Balogh and Barrett 2018). At present, it is unclear whether variation in partial self-incompatibility influences mating patterns in populations of L. salicaria.…”

“…In the summer of 2014 we selected 19 plants of each floral morph for use in a field experiment at the Koffler Scientific Reserve (KSR) near Newmarket, Ontario, Canada (44.0309N, 79.5389W). The plants were previously screened for partial self-incompatibility in the glasshouse and exhibited the typical pattern in which plants of the M-morph set variable numbers of fruit after selfpollination, and the L-and S-morphs set few if any fruit (Balogh and Barrett 2018). We grew these individuals in the glasshouse in pots 21.6 cm diameter by 21.6 cm height (8.5 × 8.5 inches) containing Promix BX soil with Osmocote slow-release fertilizer (Scotts Miracle-Gro Company, Marysville, Ohio, USA) added as per the manufacturer's instructions, until they were transferred to the field.…”

‘A most complex marriage arrangement’: recent advances on heterostyly and unresolved questions

“…Partial self‐incompatibility in the M‐morph also occurs in most populations of Lythrum salicaria (Colautti et al ., ) with considerable variation among plants in the degree of self‐compatibility. Individual variation is repeatable across years and has a weak heritable basis, and M‐morph offspring within segregating selfed families of M‐morph parents are significantly more self‐compatible than plants of the L‐morph (Balogh & Barrett, ). This difference in morph‐specific expression may result from the pleiotropic effects of genes controlling tristylous characters, with variation among individuals caused by genetic modifiers either linked or unlinked to the M ‐locus.…”

Lythrum salicaria L. Tohumlarının Morfolojik Özelliklerine Etki Eden İki Önemli Ekolojik Faktör: Tepe Tacı Kapalılığı ve Lokasyon

“…L. salicaria tohumları yaklaşık 1 mm boyunda olup olgun bireylerde yılda 2 milyonun üzerinde tohum elde edilmektedir [11]. Kendine tozlaşan tohumlar özellikle yağmur, rüzgar, sulak alanda yaşayan hayvanlar ve su kuşlarının dışkıları ile taşınırlar [12]. Tohumlar suyun yüzeyinde bulunur ve oluşan su akımlarıyla kolaylıkla taşınabilmektedir.…”