Selective spore germination on shoots of Homalothecium lutescens, a moss with dwarf males

Spores from three bryophyte species with dwarf males (Homalothecium lutescens, Homalothecium sericeum and Isothecium alopecuroides) were sown on shoots of H. lutescens in vitro. After 10 months, presence and fertility of dwarf plants were scored. Spores of the more distantly related I. alopecuroides were unable to develop into dwarf plants on H. lutescens. Spores of both H. lutescens and H. sericeum developed into dwarf plants. In fact, dwarf plants of H. sericeum were both more abundant and more often fertile than those of H. lutescens. The ability of H. sericeum spores to develop into dwarf males on shoots of H. lutescens suggests a possible pathway for hybridization between the two species. On the other hand, the inability of I. alopecuroides to develop into dwarf males on shoots of H. lutescens suggests that regulation of spore germination and dwarf male development on host shoots is associated with the degree of relatedness between species.本实验将三种具矮雄体（dwarf males）的苔藓植物（bryophyte）物种——黄扁藓（Homalothecium lutescens）、绢丝扁藓（Homalothecium sericeum）与狐尾同蒴藓（Isothecium alopecuroides）的孢子，接种于黄扁藓的茎枝上进行体外（in vitro）培养。培养10个月后，对矮雄植株的存在状态与育性（fertility）进行观测评分。结果显示：亲缘关系较远的狐尾同蒴藓孢子无法在黄扁藓茎枝上发育为矮雄体；黄扁藓与绢丝扁藓的孢子均可发育为矮雄体，且绢丝扁藓的矮雄植株不仅数量更为充裕，育性也显著高于黄扁藓的矮雄植株。绢丝扁藓孢子可在黄扁藓茎枝上发育为矮雄体这一发现，提示二者之间存在潜在的杂交途径。另一方面，狐尾同蒴藓无法在黄扁藓茎枝上形成矮雄体，表明宿主茎枝上的孢子萌发与矮雄体发育调控机制，与物种间的亲缘关系程度密切相关。