| Popis: |
A new interspecific hybrid in Isoetes, Isoetes macrospora Dur. × riparia Engelm., is delineated and described from Papineau County, Quebec, Canada by means of cytology and scanning electron microscopy of spores. Isoetes ×jeffreyi D. M. Britton and D. F. Brunton, hyb.nov., is the name proposed for this taxon. It is a heptaploid (7x; 2n = 77) and is believed to be sterile. Hybrid plants demonstrate hybrid vigour and have polymorphic, frequently aborted spores that demonstrate size and surface ornamentation features intermediate between the putative parents. Five populations of the hybrid were found growing with either, neither, or both putative parents at the sand-bottomed outlet of a large lake. Active silt and sand erosion and deposition caused by swirling lake currents appears to facilitate opportunities for hybridization. Isoetes ×jeffreyi is expected to be a rare taxon owing to the restricted sympatric area of the putative parents and their contrasting habitat preferences. Key words: Isoetes, Isoetes macrospora, Isoetes riparia, Isoetes ×jeffreyi, hybrid, Quebec. |
