Mating system variation along a successional gradient in the allogamous and colonizing plant Crepis sancta (Asteraceae)

Abstract

We analysed mating system in an annual and colonizing plant, Crepis sancta, that occupies different successional stages in the French Mediterranean region. Based on a previous experiment, we hypothesized that low inbreeding depression measured in young successional stages should select for selfing whereas higher inbreeding depression in old stages should select for outcrossing. Nine populations of C. sancta (Asteraceae) from contrasting successional stages were used to analyse (1) Seed set after autonomous and enforced selfing in controlled conditions and (2) outcrossing rates in natural conditions using allozymes (progeny array analysis). We found that C. sancta possesses a pseudo-self-incompatibility system and that mating system varies among populations. Allozymes revealed that the population multilocus outcrossing rates vary from 0.77 to 0.99. The lowest outcrossing rates occur in the youngest successional stages and complete outcrossing is found in old stages. The data partially agree with the predictions we made and the results are more generally discussed in the light of factors changing during succession. We did not find any evidence of reproductive assurance in the nine populations, contrary to what is often assumed as a major factor governing mating system evolution in colonizing species. We propose that mating system variation can be interpreted as the result of the balance between the cost of outcrossing and inbreeding depression in a metapopulation context.

Variation in the timing of autonomous selfing among populations that differ in flower size, time to reproductive maturity, and climate

“…Plant was included as a random factor in each model. Ritland, 1990 ; three Amsinckia species, Johnston and Schoen, 1996 ;Collinsia heterophylla , Mayer et al, 1996 ; Crepis sancta , Cheptou et al, 2002 ;Collinsia verna , Kalisz etal., 2004). However, this variation has been linked to among-population differences in morphology (usually anther -stigma separation) less frequently (e.g., Eichhornia paniculata , Barrett and Husband, 1990 ;Leavenworthia crassa , Lyons and Antonovics, 1991 ;Clarkia tembloriensis , Holtsford and Ellstrand, 1992 ; Hibiscus laevis , Klips and Snow, 1997 ; Aquilegia canadensis , Herlihy and Eckert, 2004 ).…”

Effects of fragmentation on plant adaptation to urban environments

“…The two rural populations (CL, PSL) occurred within large, unfragmented habitats , 30 km from Montpellier. Population CL occurred in a vineyard (50 individuals per square metres [37]) while PSL occurred in a 5 years-abandoned vineyard (10 individuals per square metres [37]). Two of the four urban populations were unfragmented (BF and VV, reflecting a dense lawn and dense vineyard in the city) while two were highly fragmented (AI and JC [19,26,35]; 5 -10 individuals per square metre [36]).…”

Population size, self-incompatibility and genetic rescue in diploid and tetraploid races of Rutidosis leptorrhynchoides (Asteraceae)

“…Fluctuations in SI in response to dramatic declines in population size associated with colonization dynamics have also been observed in Crepis sancta (Cheptou et al, 2002). For species where there is inherent flexibility within the SI system (pseudo-selfcompatibility) (De Nettancourt, 1977;Levin, 1996), mate availability in populations with reduced S-allele diversity can be maintained by the action of modifier loci unlinked to the S-locus (Hiscock, 2000;Good-Avila and Stephenson, 2002) or by the action of a cryptic gametophytic SI system (Lewis et al, 1988;Hiscock, 2000).…”