BayCEER Workshop 2026

What maintains co-existence of two bog-pine genotypes? Integrating genetics, cone morphology, climate and flowering phenology

P 4 in Posters

The bog pine, Pinus rotundata Link is a taxonomically unresolved and putatively hybridogenic member of the Pinus mugo complex, it has a scattered and relictual distribution in Bavaria in bogs and along pre-alpine river banks. We combined chloroplast genetics, cone morphology, climatic niche analyses and flowering observations to investigate the maintenance of variation within northern Bavarian populations. Two chloroplast variants, G and T, differing by a single SNP in the trnL–trnF region, frequently occurred sympatrically. Their cone morphologies overlapped, although G-type individuals tended to exhibit stronger, more asymmetric P. uncinata-like apophysis hooks, whereas T-type individuals more often had weakly hooked, P. mugo-like cones. G was more frequent under colder, high-elevation conditions, while T occurred relatively more often at warmer and drier sites.  
Multi-year phenological observations showed local differences in flowering onset, but no consistent separation between G and T across sites and years. Maximum pollen release and female receptivity overlapped within and between both variants, providing no evidence that flowering time constitutes a strong reproductive barrier. In contrast, flowering differed markedly among pine taxa: P. sylvestris flowered approximately five days earlier than P. rotundata, while putative hybrids were intermediate. Our findings indicate that ecological differentiation, rather than reproductive barriers (flowering-time Isolation), may contribute to the persistence of the two variants. Conservation measures and seed collections should therefore represent the full genetic and morphological diversity of the remaining bog-pine populations.

Keywords: Pinus mugo agg, Chloroplast haplotypes, cone morphology, flowering phenology, ecological differentiation, reproductive isolation, conservation genetics