BEC-6 The self-fertilization rate of a model species for fern biology: Intragametophytic selfing and gametophytic isolate potential of Ceratopteris richardii
Abstract
Most fern gametophytes are haploid and hermaphroditic, which means they face a challenging tradeoff: the ability of gametophytes to self-fertilize (i.e. intragametophytic selfing) allows establishment of a new population from a single spore; however, self-fertilization results in extreme inbreeding because resulting sporophytes are homozygous at all loci. Gametophytes with high selfing abilities have high gametophytic isolate potential, which refers to their ability to produce sporophytes in isolation. Some fern species undergo intragametophytic selfing at high rates while others do so at exceptionally low rates. Ceratopteris richardii is a model species used to study fern development and genetics, but their intragametophytic selfing and gametophytic isolate potential are unknown. In this study we investigated the intragametophytic selfing and gametophytic isolate potential of this species. We hypothesized that they will have high intragametophytic selfing and gametophytic isolate potential because they inhabit ephemeral water sources and must frequently establish new populations. To investigate this, we took advantage of a recessive mutation (cp1) in the C-Fern® cultivar that causes chloroplasts to clump in the gametophyte and sporophyte giving them a polka-dot appearance (“polka dot”), contrary to the wild-type dominant phenotype that is homogenously green. In the laboratory, we cultured gametophytes and transplanted immature polka-dot gametophytes to individual Petri dishes with three treatments: (1) isolated (no neighbor), (2) with one hermaphrodite wild-type gametophyte, and (3) with one male wild-type gametophyte. We watered dishes weekly to allow for fertilization and observed the number and phenotypes of sporophytes produced on the polka-dot gametophytes. According to preliminary data, the rate of gametophytic isolate potential was high, with 100% of polka-dot gametophytes in isolation producing sporophytes. The preliminary data indicate that intragrametophytic selfing rates with a neighbor were also high, with 78% of polka-dot gametophytes with a hermaphrodite neighbor producing polka-dot sporophytes and 56% of polka-dot gametophytes with a male neighbor producing polka-dot sporophytes. Overall, these results suggest that the rates of gametophytic isolate potential and intragametophytic selfing tell a similar story. Both suggest that C. richardii self-fertilize at high rates and therefore are capable of populating new locations from a single spore.
Keywords
C-Fern, cpi mutation, inbreeding, Polypodiophyta, reproductive assurance, selfing potential
BEC-6 The self-fertilization rate of a model species for fern biology: Intragametophytic selfing and gametophytic isolate potential of Ceratopteris richardii
University Readiness Center Greatroom
Most fern gametophytes are haploid and hermaphroditic, which means they face a challenging tradeoff: the ability of gametophytes to self-fertilize (i.e. intragametophytic selfing) allows establishment of a new population from a single spore; however, self-fertilization results in extreme inbreeding because resulting sporophytes are homozygous at all loci. Gametophytes with high selfing abilities have high gametophytic isolate potential, which refers to their ability to produce sporophytes in isolation. Some fern species undergo intragametophytic selfing at high rates while others do so at exceptionally low rates. Ceratopteris richardii is a model species used to study fern development and genetics, but their intragametophytic selfing and gametophytic isolate potential are unknown. In this study we investigated the intragametophytic selfing and gametophytic isolate potential of this species. We hypothesized that they will have high intragametophytic selfing and gametophytic isolate potential because they inhabit ephemeral water sources and must frequently establish new populations. To investigate this, we took advantage of a recessive mutation (cp1) in the C-Fern® cultivar that causes chloroplasts to clump in the gametophyte and sporophyte giving them a polka-dot appearance (“polka dot”), contrary to the wild-type dominant phenotype that is homogenously green. In the laboratory, we cultured gametophytes and transplanted immature polka-dot gametophytes to individual Petri dishes with three treatments: (1) isolated (no neighbor), (2) with one hermaphrodite wild-type gametophyte, and (3) with one male wild-type gametophyte. We watered dishes weekly to allow for fertilization and observed the number and phenotypes of sporophytes produced on the polka-dot gametophytes. According to preliminary data, the rate of gametophytic isolate potential was high, with 100% of polka-dot gametophytes in isolation producing sporophytes. The preliminary data indicate that intragrametophytic selfing rates with a neighbor were also high, with 78% of polka-dot gametophytes with a hermaphrodite neighbor producing polka-dot sporophytes and 56% of polka-dot gametophytes with a male neighbor producing polka-dot sporophytes. Overall, these results suggest that the rates of gametophytic isolate potential and intragametophytic selfing tell a similar story. Both suggest that C. richardii self-fertilize at high rates and therefore are capable of populating new locations from a single spore.