Hieracium × grofae — a rediscovered diploid hybrid from the Ukrainian Carpathians

Abstract

Diploid hybrid plants (2n = 18) between sexual diploid cytotypes of Hieracium alpinum and H. umbellatum were found in the Ukrainian Eastern Carpathians. They were identified with H. ×grofae WO L., originally used for the combination H. decipiens ×H. umbellatum var. lactaris. As H. decipiens sensu WO L. (non TAUSCH) does not produce viable pollen grains and is most probably a polyploid apomict, it is unlikely to produce diploid hybrid plants with diploid H. umbellatum. Both parent species, Hieracium alpinum and H. umbellatum are also given by WO LOSZCZAK from the original locality. Thus we conclude that H. ×grofae is result of hybridization between H. alpinum and high mountain form of H. umbellatum. Hybrid plants are morphologically intermediate between the parent species, and moreover resemble closely or they are identical with the experimental hybrids of the same parent combination. Hybrids produce rather high amount of homogeneously sized pollen grains (values of standard deviation and coefficient of variation lower then upper limits for diploids -3µm or 7.5%, respectively), and might probably serve as male parents in further crosses; on the other hand, they are fully seed-sterile. A lectotype of H. ×grofae, a second proved nothotaxon in the genus Hieracium s.str., is designated. Localities of H. ×grofae are located in subalpine belt of the Marmarosh Mts, the Svydovets' Mts and the Horhany Mts (all in the Ukrainian Eastern Carpathians). Biotopes of hybrid plants usually represent secondary formed and disturbed pastures allowing close contact of altitudinally vicariant parent taxa.

Interspecific hybridization in the genus Hieracium s. str.: evidence for bidirectional gene flow and spontaneous allopolyploidization

“…These rare diploid hybrids were found in the Romanian and Ukrainian Eastern Carpathians where their parental diploid taxa, though ecologically vicariant, co-occur. Although the hybrid plants did not differ in pollen size and pollen production from their parents, they were completely seed sterile (Mráz et al 2005;Chrtek et al 2006). Analyses of plastid DNA in the diploid nothotaxon H. 9krasani revealed that the maternal plant was H. transsilvanicum and the pollen donor was H. alpinum in both populations analyzed (Mráz et al 2005).…”

“…and H. 9 grofae Woł. (H. alpinum 9 H. umbellatum L.) are the only convincingly documented recent hybrids in the genus (Mráz et al 2005;Chrtek et al 2006). These rare diploid hybrids were found in the Romanian and Ukrainian Eastern Carpathians where their parental diploid taxa, though ecologically vicariant, co-occur.…”

“…Only two incidences of natural recent hybridization have been documented so far in the genus Hieracium (Mráz et al 2005;Chrtek et al 2006). In both cases, only diploid parental taxa were involved, although crossing between diploid and polyploid cytotypes is possible as was demonstrated by experimental crossing (Mráz 2003;Mráz and Tomčíková 2004).…”

Reconstruction of phylogenetic relationships in a highly reticulate group with deep coalescence and recent speciation (Hieracium, Asteraceae)

“…The genus has experienced extensive hybridization in the past (Fehrer et al, 2009, and references therein). In contrast, recent natural hybridization is very rare (Mráz et al, 2005;Chrtek et al, 2006); natural as well as experimental hybrids (Mráz and Paule, 2006) are either completely female sterile or produce only a few seeds. The basic chromosome number of Hieracium (and related genera) is x ¼ 9.…”

Geographical parthenogenesis, genome size variation and pollen production in the arctic-alpine species Hieracium alpinum

“…A large quantity of pollen of homogeneous size is characteristic for diploid H. alpinum (Chrtek 1997;Mráz et al 2002;Kovalčiková 2004;Chrtek et al 2006;Slade and Rich 2007). In contrast, most plants from the triploid range did not produce pollen at all (Table 4).…”