Nuphar × porphyranthera Lansdown and Ruhsam

Lansdown, Richard & Ruhsam, Markus, 2022, YELLOW WATER LILIES (NUPHAR, NYMPHAEACEAE) IN GREAT BRITAIN: A NEW HYBRID, A REAPPRAISAL OF RECORDS, AND A REVISED STATUS OF N. ADVENA, Edinburgh Journal of Botany 79 (1925), pp. 1-15 : 7

Nuphar × porphyranthera Lansdown and Ruhsam , hybr. nov.

( N. lutea × N. advena )

The most useful characters for distinguishing Nuphar × porphyranthera from N. advena and N. lutea are anther sterility and the failure to develop capsules, the number of sepals, petiole shape in section, and the proportion of leaves that are emergent or floating. The early degradation of leaves in July, possibly caused by an invertebrate to which the hybrid may be more susceptible, is also a good indicator of populations of Nuphar × porphyranthera ( Figure 4 ), because N. lutea and N. advena leaves typically persist at least until September. Nuphar × porphyranthera populations that occur in lakes which are no longer maintained and drying out, typically have swards of upright leaves ( Figure 5 C ). Based on a limited amount of available material, it appears likely that Nuphar × porphyranthera can be distinguished from N. lutea , even when not flowering, by the shape of the petiole section ( Figure 6 B ). Holotype: United Kingdom. Middlesex. Small stand in shade of trees on margin of former gravel pit, Ferry Lane, Shepperton, TQ076663, 7 vii 2021, R.V. Lansdown RVL 21/1, E01080171 (E). Paratype: United Kingdom. Surrey. Glebe Water, Godstone, TQ3584851407, 16 vii 2022, R.V. Lansdown RVL 21/2 (BM). Figures 4 , 5 , 6B , 7B , 8B .

Most leaves emergent, vertical or at a steep angle ( Figure 5 ), leaves that lie flat on the water often forming a fringe around stands of emergent leaves, starting to decay in July with blade generally lost by August; petiole rounded or angular in section ( Figure 6 B ). Sepals

5 (or 6), the 2 or 3 outer mainly green, the 3 inner yellow with a green patch at the base, occasionally tinged reddish on the margins ( Figure 7 B ). Filaments 4.1–9.9 mm, typically yellow to whitish yellow; anthers 5–11 mm, typically deep purple, occasionally yellow

( Figure 8 B ), with two raised lines but no pollen formed; ratio of anther to filament length, 0.5–1.3. Capsules aborted (i.e. misshaped and shrunken).

Figures

Figure 4. Habit of Nuphar × porphyranthera, showing decaying leaves in July 2020, from NH4 population, Painshill Park. Photograph: R. V. Lansdown.

Figure 5. Nuphar × porphyranthera: A, leaf shape from NH12 population, Auchnagairn House; B, leaf shape from NH6 population, Shropham Ponds; C, habit from NH12 population in drying-out pond, Auchnagairn House. Photographs: R. V. Lansdown.

Figure 6. A, Petiole shape of Nuphar advena from NA1 population, Spottiswoode Loch. B, Petiole shape of Nuphar × porphyranthera from NH8 population, Oulten Park (left); NH6 population, Shropham Ponds (centre); and NH1 population, West Hoathly (right). C, Petiole shape of Nuphar lutea (no population code), Elterwater. Scale bars are approximate (no measurements of the photographed features were taken). Photographs: R. V. Lansdown.

Figure 7. Sepals of: A, Nuphar advena from NA1 population, Spottiswoode Loch; B, Nuphar × porphyranthera from NH8 population, Oulten Park (left), and NH2 population, Godstone (right); C, N. lutea (no population code), Norbotten, Sweden. Scale bars are approximate (no measurements of the photographed features were taken). Photographs: R. V. Lansdown.

Figure 8. Flowers and stamens of: A, Nuphar advena from NA1 population, Spottiswoode Loch; B, Nuphar × porphyranthera from NH8 population, Oulten Park (left), and NH1 population, West Hoathly (right); C, N. lutea (no population code), Elterwater (left) and Pop1 population, Ashtead (right). Scale bars are approximate (no measurements of the photographed features were taken). Photographs: R. V. Lansdown.