Fagúndez, J. (2012). Study of some European wild hybrids of Erica L. (Ericaceae), with descriptions of a new nothospecies: Erica ×nelsonii Fagúndez and a new nothosubspecies: Erica ×veitchii nothosubsp. asturica Fagúndez. Candollea 67: 51–57. In English, English and French abstracts.
Wild hybrids issued from crossing European species of genus Erica L. are described. The close study of the type material of Erica ×lazaroana Rivas Goday & Bellot (Erica arborea L. × Erica umbellata L.) shows that it should be regarded as a new synonym of Erica arborea. Erica ×nelsonii Fagúndez (Erica cinerea L. × Erica tetralix L.), a new nothospecies from Ireland, is described from herbarium material. Erica ×veitchii nothosubsp. asturica Fagúndez (Erica arborea × Erica lusitanica subsp. cantabrica Fagúndez & Izco) is also described. A study of seed micromorphology shows evidence of hybridization between Erica tetralix L. and Erica ciliaris L.
Introduction
Erica L. (Ericaceae) is a large genus of over 850 species according to the most recent assessments (Oliver, 2000). The genus has a remarkable geographic distribution, with a northsouth range from Scandinavia to South Africa (Oliver, 2000; Stevens & al., 2004). There is also a high morphological variability on plant habit, vegetative characters, indumentum, corolla size and type, fruit type, pollen or seeds (Stevens & al., 2004). Hybridization on the genus has been known since the description by Bentham (1839: 665) of Erica ×watsonii Benth. as the cross of the European species E. ciliaris L. and E. tetralix L. Since then, three more hybrids have been described from wild populations and several others from garden plants or artificial crosses (Griffiths, 1985). Hybridization has been recorded for several species of the Cape (Oliver, 1986) and some hybrids between European species, Cape species and even between Cape and European species have been produced for gardening purposes (Nelson & Oliver, 2004). However, hybridization within Erica is low, and only few crosses have been described considering the large number of species of the genus with a sympatric geographic distribution. It is remarkable that most of the hybrids are formed by only a few species that are involved in more than one cross. This is the case for the Cape hybrids (Oliver, 1986), and also for the European species for which E. tetralix is one of the parents of three recognized hybrids. In this paper, the status of several crosses from the study of original material is discussed, and one new hybrid is described.
Results and discussion
1. Erica × lazaroana Rivas Goday & Bellot (E. arborea L. × E. umbellata L.) in Anal. J. Bot. Madrid 6: 152. 1946.
Lectotypus (designated by Pizarro Domínguez, 2007): SPAIN. Jaén: “Habitat cum E. arboreae et umbellatae, in quercetis suberis, inter Santa Elena et Aliseda, in montibus Marianis”, 11.V.1941, Rivas Goday & Bellot s.n. (MAF [20627]).
= Erica arborea L., Sp. Pl.: 353. 1753 (lectotypified by Jarvis & McClintock, 1990: 517).
The original description of this hybrid does not propose a type specimen. However, the authors' material is found in MAF, and one single specimen is labelled as E. ×lazaroana. The locality is the same as what is mentioned in the protologue, so there is no doubt that this specimen should be considered the type. A copy of the description, probably by the authors, is included with the specimen. It lacks a latin diagnosis, but the authors refer to E. umbellata var. subcampanulata DC. as a synonym of E. ×lazaroana. This variety was described as having a “Corola fauce apertiore, staminibus brevioribus” (Bentham, 1839: 666), from south Spain.
The main features to differentiate this hybrid from its parents are: (1) from E. arborea, shorter flower pedicels, exerted style with a subbifidous stigma, campanulate corolla and an oblong, congest synflorescence with flowers in umbels, and (2) from E. umbellata, the higher habit, included anthers and non urceolate corolla. There is also a description that mentions these characters and the apendiculate anthers and curved leaves. After a close study of the cited specimen and the description proposed, we conclude that E. ×lazaroana is a form of E. arborea, with no characters that could resemble E. umbellata other than the number of flowers in each umbel, which is high for E. arborea, and the congested synflorescence. Presence of divided hairs on the stems, coloured saccate calyx, the whitish, shortly campanulate corolla, included apendiculate anthers, capitate stigma and every other character are those of E. arborea. Therefore, a new synonymy is made here.
The authors also mention the occurrence of hybridisation between E. arborea and E. scoparia L. in the area but no description or new name is proposed for this cross. Moreover there is no material deposited at MAF identified by the authors as this possible hybrid. The locality of the type specimen, described in detail by Rivas Goday & Bellot Rodríguez (1946), was prospected in May 2009. No intermediates were found for any of these heathers.
Specimens examined. — (sub. E. arborea). SPAIN. Jaén: Santa Elena, road to La Aliseda, 38°20′21″N 3°34′1″W, 730 m, 9.V.2009, Fagúndez 3119, 3120, 3121 (SANT).
2. Erica × nelsonii Fagúndez (E. cinerea L. × E. tetralix L.), nothosp. nova (Fig. 1).
Hybrida ex E. cinerea et E. tetralix genita, caulibus pilis simplicibus, sine pilis multiseriatis glanduliferis, foliis marginibus partim revolutis, floribus in umbellis terminalibus axillarisque dispositis, corolla apice pubescenti, antheris appendiculis longis, ovario sparse pubescenti.
Holotypus: Ireland. Galway: West Galway (Watsonian vice H16) 1.5 miles from Roundstone junction along the link road to Clifden. Edge of eroded peat at side of lough, 31.VIII.1964, P. F. Hunt 1636 (K, upper left fragment).
Low shrub, ramified from the base. Stems glabrous or with some simple, woolly hairs at the apex. Leaves in whorls of 3 in young twigs and 4 in mature stems, patent or slightly erect in the upper part, 2–3 mm, ovate, with half-rolled margins on the base, some slightly curved, glabrous or almost in the adaxial surface, abaxial surface with some hairs on the midrib. Axillary fascicles of leaves sometimes present. Inflorescence a terminal umbel of 4–10 flowers. Synflorescence one to several umbels, these at the apex of long lateral branches and at the end of short branches below the apex. Hairy pedicels with simple hairs, bract and bracteoles leaf-like but reduced in size, the bract half way on the pedicel and bracteoles right below the calyx. Corolla pink, broadly urceolate, 6–7 mm with some long, simple hairs below the lobes. Ovary with some sparse hairs, mostly at the apex. Stamens with filaments geniculate below the anthers, these with slightly curved appendages, with some broad teeth on margins.
Dedicated to Ernest Charles Nelson (born in Belfast, 1951), a well-known Irish botanist with much interest and research done on European heathers.
The main differences between the new nothospecies and its parents are shown on Table 1. It can be easily distinguished from both by its sparsely hairy ovary, from E. cinerea by its corolla and leave shape and the hairs on its corolla and from E. tetralix by the synflorescence arrangement and the lack of glandular, multiseriate hairs on leaves and stems. Leaves are 3-nate as in E. cinerea or 4-nate as in E. tetralix, in some stems the number of leaves per whorl is not clear.
This material was originally labelled as E. cinerea by P. F. Hunt, but recognized as a possible hybrid by R. Ross in 1973. He stated in a note “probably a hybrid? E. cinerea × E. mackaiana or E. cinerea × E. tetralix”. A close study of the three plants on the sheet clearly shows that this is a hybrid. E. cinerea and E. mackayana Bab. both have a glabrous ovary therefore these cannot be the parents, as the hybrid has a hairy ovary although not as dense as in E. tetralix type. Leaves have some similarities with those of E. mackayana, with no simple hairs, but it lacks the pluricellular, multiseriate glandular hairs that characterize the leaves of E. mackayana. These are also found in E. tetralix, sometimes eglandular.
The locality of the type was intensely prospected in August 2009 but no plants with these intermediate characters were found.
Several natural hybrids involve E. tetralix: E. ×watsonii (E. ciliaris × E. tetralix), E. ×stuartii (MacFarl.) Mast. (E. mackayana × E. tetralix) or E. ×williamsii Druce (E. vagans L. × E. tetralix). The only one that may involve E. cinerea is the artificial hybrid raised by K. Kramer E. ×arendsiana E. C. Nelson (Nelson, 2008) formed with E. terminalis Salisb., a species with no clear systematic position, but somewhat close to E. cinerea according to some features such as seed morphology (Fagúndez & Izco, 2009). Sturm ( 1901: 219) mentions the existence of the E. tetralix and E. cinerea cross in England but this is most probably a mistaken record (Griffiths, 1985).
Specimens examined. — (sub. E. tetralix). IRELAND. Co Galway: Connemara, North margin of Ballynalinch Lake, 53°27.993′N 9°49.858′W, 110 m, 2.VIII.2009, Fagúndez 3172, 3173, 3175 (SANT); “The bog road” between Roundstone and Clifden, 53°26.625′N 9°55.707′W, 70 m, 2.VIII.2009, Fagúndez 3182, 3183 (SANT); North face of Mnt. Errisbeg, near Nawleney Lake, 53°24.363′N 9°58.531′W, 40 m, 3.VIII.2009, Fagúndez 3188, 3189 (SANT); South margin of Ballynalinch Lake, road side near the castle, 53°27.096′N 9°52.194′W, 170 m, 2.VIII.2009, Fagúndez 3191 (SANT).
(sub. E. cinerea). Ireland. Co Galway: Connemara, North margin of Ballynalinch Lake, 53°27.993′N 9°49.858′W, 110 m, 2.VIII.2009, Fagúndez 3171, 3174 (SANT); North face of Mnt. Errisbeg, near Nawleney Lake, 53°24.363′N 9°58.531′W, 40 m, 3.VIII.2009, Fagúndez 3185 (SANT); South margin of Ballynalinch Lake, road side near the castle, 53°27.096′N 9°52.194′W, 170 m, 2.VIII.2009, Fagúndez 3190 (SANT).
Fig. 1.
Erica ×nelsonii Fagúndez. A. Synflorescence of upper left fragment (typus) ; B. General view of upper right fragment.
[P. F. Hunt 1636, K] [Drawn by the author]
Table 1.
Main differences between Erica ×nelsonii Fagúndez and its parents.
3. Erica × veitchii nothosubsp. asturica Fagúndez (E. arborea L. × E. lusitanica subsp. cantabrica Fagúndez & Izco), nothosubsp. nova
Typus: SPAIN. Oviedo: (sub. E. arborea), Candamo, Laracha, 29TQJ4010, 105 m, 8.IV.2002, J. J. Lastra s.n. (holo-: SANT [47856]; iso-: LIST!).
Hybrida ex E. arborea et E. lusitanica subsp. cantabrica genita, caulibus pilis simplicibus non pilis divisis, floribus bractea et bracteola ad basim pedicelli instructis, corolla 3–3.5 mm, filamentis staminorum glabris, antheris 0.8 -1 mm appendiculis spinulosis.
This hybrid was proposed in Fagúndez (2006) but the name E. lusitanica subsp. cantabrica Fagúndez & Izco was only validly published one year later (Fagúndez & Izco, 2007). The type for E. ×veitchii Bean has been proposed by Nelson (2008) and it should apply to nothosubsp. veitchii. E. ×veitchii was described by Bean (1905) based on a plant discovered in a nursery in Exeter (UK). Its parents were plants cultivated at the nursery; none of the species are native in the UK. The first reference to this cross was provided by Laguna (1883), but there is no reference material and no name was proposed. I have studied some material labelled as the cross of E. arborea and E. lusitanica Rudolphi from different herbaria. All of these turned out to be within the variability of E. arborea.
Specimens examined. — (sub. E. arborea). SPAIN. León: Ancares, 1973, Benítez (COA [21331] [labelled Erica ×veitchii, det. Pujadas 1996]). Jaén: Valles del Linarejo, 5.III.1967, Ladero (MAF [118272] [labelled Erica arborea × E. lusitanica]). Cáceres: Sierras de Altamira y Carbonera, 5.IV.1967, Ladero (MAF [147963 [labelled Erica arborea × E. lusitanica]).
4. Cross-pollination of Erica tetralix and E. ciliaris
During the study of seed morphology of E. tetralix and related species (Fagúndez & Izco, 2009) one of the samples collected from an E. tetralix population clearly differed from the rest of the population with respect to the shape of the seeds and secondary sculpture. The seed morphology and details of the secondary ornamentation of this sample and a regular population of E. tetralix and E. ciliaris are shown in Fig. 2. The seeds of E. tetralix are ovoid or ellipsoid, of ca. 0.4 mm, with a reticulate primary ornamentation and a smooth to vermiculate secondary sculpture of outer periclinal walls (Fagúndez & Izco, 2009). The seeds of E. ciliaris are similar in size, but with an oblong-ellipsoid shape, a very faintly reticulate pattern and an indented secondary ornamentation (Fagúndez & Izco, 2009). In this intermediate population, seeds are largely ellipsoid or ovoid, with a slightly reticulate pattern and an indented secondary ornamentation.
The parent plants were studied and the population was visited at the same locality in flowering time (Cercedo, July 2007, see specimens studied). This population is part of a humid heathland with Ulex L. where Erica ciliaris is abundant and E. tetralix occurs whenever soils are moist. The plants are E. tetralix with no intermediate characters. Thus, we conclude that these seeds are product of the pollination of E. tetralix plants with pollen from E. ciliaris.
Erica ×watsonii (E. ciliaris × E. tetralix) is the most common of the European hybrids, described by Bentham (1839: 665) from plants found by H. Watson and well known in the British Isles (Hooker & Arnott, 1850: 255) and France (Neyraut, 1900; Rouy, 1908: 109). There are also references from the Iberian Peninsula (Pereira-Coutinho, 1939: 550; Bayer, 1993: 506) although we have not found any material or precise localities. In the British populations of E. ciliaris, where E. ×watsonii is common, a very low percentage of seedlings have intermediate values for E. ciliaris and E. tetralix and may produce hybrid plants (Rose, 2007). In Spain no intermediates are commonly found although both species coexist in many localities (pers. obs.).
The indented surface in the secondary sculpture of the E. ciliaris seeds is uncommon for the European species of the genus. We have only recorded this feature in E. ciliaris and some populations of E. sicula Guss. (Fagúndez & Izco, 2011). The outer periclinal walls of the testa cells are collapsed to the inner walls that present pits, allowing the cell surface to display this indented pattern.
Specimens examined. — (sub. E. tetralix). Spain. Pontevedra: Cercedo, Quireza, 42°34′48″N 8°27′54″W, 690 m, 28.IX.2006, 2.VIII.2007, Fagúndez 3266 (SANT). A Coruña: Carnota, O Pindo, 11.XI.1999, Fagúndez s.n. (SANT-BG [119]). Ciudad Real: Cabañeros, 2.X.2000, Fagúndez s.n. (SANT-BG [211]).
(sub. E. ciliaris). SPAIN. Cádiz: Los Alcornocales, 25.IX. 2002, Fagúndez & Reyes s.n. (SANT-BG [266]).
Portugal: Matas de Faia, 11.IX.2001, s.coll. (SANT-BG [273]).
Fig. 2.
Seeds of different species of Erica L. A: Erica tetralix L.; B: E. tetralix (detail of surface cells) ; C: E. tetralix × E. ciliaris ; D: E. tetralix × E. ciliaris (detail of surface cells) ; E: E. ciliaris L.; F: E. ciliaris (detail of surface cells).
[A: Fagúndez s.n., SANT-BG [119]; B: Fagúndez s.n., SANT-BG [211]; C–D: Fagúndez 3266, SANT; E: Fagúndez & Reyes s.n., SANT-BG [266]; F: Fagúndez & Reyes s.n., SANT-BG [273]]
Acknowledgements
I wish to acknowledge the curators of the consulted herbaria and J. Izco from University of Santiago de Compostela. Latin translation by M. A. Garland. The journal reviewers and editor made useful comments. This work was partially supported by the Science and Education ministry of Spain (project CGL2006-06890).
