O father where art thou? Paternity analyses in a natural population of the haploid–diploid seaweed Chondrus crispus

Abstract

The link between life history traits and mating systems in diploid organisms has been extensively addressed in the literature, whereas the degree of selfing and/or inbreeding in natural populations of haploid-diploid organisms, in which haploid gametophytes alternate with diploid sporophytes, has been rarely measured. Dioecy has often been used as a proxy for the mating system in these organisms. Yet, dioecy does not prevent the fusion of gametes from male and female gametophytes originating from the same sporophyte. This is likely a common occurrence when spores from the same parent are dispersed in clumps and recruit together. This pattern of clumped spore dispersal has been hypothesized to explain significant heterozygote deficiency in the dioecious haploid-diploid seaweed Chondrus crispus. Fronds and cystocarps (structures in which zygotes are mitotically amplified) were sampled in two 25 m 2 plots located within a high and a low intertidal zone and genotyped at 5 polymorphic microsatellite loci in order to explore the mating system directly using paternity analyses. Multiple males sired cystocarps on each female, but only one of the 423 paternal genotypes corresponded to a field-sampled gametophyte. Nevertheless, larger kinship coefficients were detected between males siring cystocarps on the same female in comparison with males in the entire population, confirming restricted spermatial and clumped spore dispersal. Such dispersal mechanisms may be a mode of reproductive assurance due to nonmotile gametes associated with putatively reduced effects of inbreeding depression because of the free-living haploid stage in C. crispus.

Higher reproductive success for chimeras than solitary individuals in the kelp Lessonia spicata but no benefit for individual genotypes

“…Chimerism is a common phenomenon in many different kinds of organisms, including amoebas (Foster et al 2002), fungi (Aanen et al 2008), bacteria (Velicer and Vos 2009), sponges (Maldonado 1998), bryozoans (Buss 1982), hydrozoans (Hart and Grosberg 1999), corals (Raymundo and Maypa 2004), ascidians (Bishop and Sommerfeldt 1999;Rinkevich 2005), vertebrates (Rinkevich 2001;Ross et al 2007), marine algae (Santelices et al 1999;Wernberg 2005;González and Santelices 2008;Krueger-Hadfield et al 2015;Segovia et al 2015) and angiosperms (Thomson et al 1991;McIntire and Fajardo 2011). Relatedness within chimeras is thought to be high due to developed kin recognition systems that allow successful fusion only between related conspecifics (e.g.…”

Chondrus crispus – A Present and Historical Model Organism for Red Seaweeds

“…Fredericq, Brodie, and Hommersand (1992) found female gametophytes bearing cystocarps, which contained small patches of elongate surface cells near the apex which appeared to function as spermatangial initial cells. However, paternity analyses in natural populations of C. crispus revealed the presence of male alleles in cystocarpic DNA, with the exception of 11 cystocarps (<2%) that only exhibited one allele at all microsatellite loci (Krueger-Hadfield et al, 2014).…”

“…The resulting diploid carpospores are an additional dispersive stage in comparison to other algal life cycles and germinate into the free-living tetrasporophyte. Krueger-Hadfield, Roze, Destombe, Correa, and Valero (2014) were the first to demonstrate cross fertilisation using genetic markers in the field and in the laboratory. Chen and McLachlan (1972) observed an increase in the number of cystocarps produced when male and female gametophytes obtained from cultured tetraspores were crossed in aerated culture chambers.…”

Development and characterization of microsatellite markers in two agarophyte species, Gracilaria birdiae and Gracilaria caudata (Gracilariaceae, Rhodophyta), using next-generation sequencing

“…Irvine, and W.F. Farnham and in Chondrus crispus Stackhouse (Krueger-Hadfield et al 2015). These markers are also efficient for describing intraspecific genetic diversity, and are used to estimate population size or connectivity for conservation genetics purposes (for review, see Sunnucks 2000).…”