Jaime Fagúndez

Heathlands confronting global change: drivers of biodiversity loss from past to future scenarios

BACKGROUND Heathlands are dynamic plant communities characterized by a high cover of sclerophyllous, ericoid shrubs that develop over nutrient-poor soils. Interest in the preservation of these habitats in Europe has increased over the last decades, but over this time there has been a general decline in habitat quality, affecting community structure, ecosystem functions and biodiversity. Negative drivers that trigger these changes include land-use changes (i.e. habitat destruction and fragmentation), pollution, climate change, natural succession and human management, as well as the presence of invasive exotic species. SCOPE Based on recent scientific literature, the effect of each of these potential drivers on a wide set of factors, including physiological traits, species richness and diversity, community structure, ecosystem functions and soil conditions, is reviewed. The effects of these drivers are generally understood, but the direction and magnitude of factor interactions, whenever studied, have shown high variability. CONCLUSIONS Habitat loss and fragmentation affect sensitive species and ecosystem functions. The nature of the surrounding area will condition the quality of the heathland remnants by, for example, propagule pressure from invasive species. The dominant ericoid shrubs can be out-competed by vigorous perennial grasses with increased atmospheric nitrogen deposition, although interactions with climate and management practices may either counteract or enhance this process. Grazing or periodic burning promotes heath loss but site-specific combined treatments maintain species diversity and community structure. Climate change alone moderately affects plant diversity, community structure and ecosystem functions. Combined with other factors, climatic changes will condition heath development, mainly with regard to key aspects such as seed set and seedling establishment, rare species occurrence and nutrient cycling in the soil. It is essential to address the effects of not only individual factors, but their interactions, together with land-use history, on heathland development and conservation in order to predict habitat response to future scenarios.

Testing reticulate versus coalescent origins of Erica lusitanica using a species phylogeny of the northern heathers (Ericeae, Ericaceae).

Whilst most of the immense species richness of heathers (Calluna, Daboecia and Erica: Ericeae; Ericaceae) is endemic to Africa, particularly the Cape Floristic Region, the oldest lineages are found in the Northern Hemisphere. We present phylogenetic hypotheses for the major clades of Ericeae represented by multiple accessions of all northern Erica species and placeholder taxa for the large nested African/Madagascan clade. We identified consistent, strongly supported conflict between gene trees inferred from ITS and chloroplast DNA sequences with regard to the position of Erica lusitanica. We used coalescent simulations to test whether this conflict could be explained by coalescent stochasticity, as opposed to reticulation (e.g. hybridisation), given estimates of clade ages, generation time and effective population sizes (Ne). A standard approach, comparing overall differences between real and simulated trees, could not clearly reject coalescence. However, additional simulations showed that at the (higher) Ne necessary to explain conflict in E. lusitanica, further topological conflict would also be expected. Ancient hybridisation between ancestors of northern species is therefore a plausible scenario to explain the origin of E. lusitanica, and its morphological similarities to E. arborea. Assuming either process influences the results of species tree and further evolutionary inference. The coalescence scenario is equivocal with regard the standing hypothesis of stepping stone dispersal of Erica from Europe into Africa; whereas reticulate evolution in E. lusitanica would imply that the colonisation of Tropical East Africa by E. arborea instead occurred independently of dispersals within the rest of the African/Madagascan clade.

Seed morphology of Erica L. sect. Chlorocodon Bentham

Abstract Seed morphology of the only species of Erica sect. Chlorocodon, E. scoparia, has been studied. Four subspecies are recognized: subsp. azorica, subsp. maderincola, subsp. platycodon and subsp. scoparia. Size and shape of seeds and size and shape of surface cells were measured. SEM pictures were performed for whole seeds and detail of the four taxa. Other minor characters such as weight of 100 seeds and seed colour were also studied. One way analysis of variance were performed for the different variables. Surface cells boundaries and anticlinal walls curvature are the main diagnostic characters. The continental subspecies (subsp. scoparia) is easily differentiated from the maca- ronesian taxa. Within these, subsp. azorica and subsp. maderincola have a similar seed type, different from subsp. platycodon seeds. The subspecific rank for these four taxa is recomended. A key to the subspecies is presented.

Systematic relevance of seed coat anatomy in the European heathers (Ericeae, Ericaceae)

The anatomy of the seed coat of the European species of tribe Ericeae (Calluna, Daboecia and Erica) of the Ericaceae family was studied, and the taxonomic importance of their characters was analyzed. The seed coat is mostly formed by a one-cell layer with thick, pitted inner walls and thin outer walls that collapse at maturity over the inner walls. The cell junctions are either raised with anticlinal walls up to four times the height of the periclinal walls or are not raised with similar values for the height of both the anticlinal and periclinal walls. Three main cell junction types were found and described. The thickness of the inner walls is variable, but there is a large overlap among the results for different species. Calluna vulgaris is the only species with no pits, and E. multiflora has a pitted pattern on its inner walls, which is distinctive from the rest of the species. Our main results agree with the external seed morphology, and valuable new data were obtained for certain groups such as the E. cinerea-E. terminalis or the E. scoparia complex. The similarities that are found in seed coat characters are not in accordance with the classical taxonomic delimitation of infrageneric groups within Erica.

Taxonomic value of seed characters in the Erica tetralix L. group (Ericaceae)

A study of the seed morphology of Erica tetralix and the related species E. mackaiana and E. andevalensis was performed to evaluate the taxonomic importance of seed characters. Size and shape of seeds and surface cells were studied, and area, perimeter, main axis lengths, elongation and sinuosity were measured. Levels of intraspecific variation were considered by means of nested analysis of variance. The study of the intraspecific variation of the characters shows significant differences for lower levels, higher than variations between species for most characters. Levels of variation must be based upon the numerical analysis of seed characters for a correct approach to determining systematic value. E. mackaiana and E. andevalensis group together versus E. tetralix for sinuosity of testa cells. This is a good taxonomic character because it shows significant differences between species and no significant differences between populations. E. tetralix has strongly undulated testa cells while E. mackaiana and E. andevalensis have slightly undulated or curved testa cells. These two species can be discriminated by size of the seed, with seeds of 0.37-0.38 mm for E. andevalensis and 0.4 - 0.45 mm for E. mackaiana. Similarities are found in seed morphology for E. mackaiana and E. andevalensis, but we nevertheless consider the species status for the three taxa as the most natural taxonomic assignment. A key to the species is provided.

Seed morphology of Erica L. sect. Loxomeria Salisb. ex Benth., sect. Eremocallis Salisb. ex Benth. and sect. Brachycallis I. Hansen, and its systematic implications

Abstract Several quantitative and qualitative seed characters of the seven European species of Erica sect. Loxomeria, Eremocallis and Brachycallis were studied. Two main seed types are found based on size and shape: regular ellipsoid or oblong seeds of ca. 0.4 mm for E. ciliaris and the E. tetralix group, and curved to kidney‐shaped seeds of 0.6–0.9 mm for E. cinerea, E. maderensis and E. terminalis. The testa surface in E. ciliaris is reticulate, with indented outer periclinal walls. Erica cinerea has inflated outer anticlinal walls. This character is exclusive for this species within the European (and nearby areas) species of the genus. The seeds of E. maderensis are similar to those of E. terminalis. According to seed morphology, the classical infrageneric classification, by which E. terminalis would be grouped with the E. tetralix group in sect. Eremocallis and E. maderensis in sect. Brachycallis with E. cinerea, is artificial.

Seed morphology of Erica L. sect. Callicodon Bentham. Taxonomic implications

ABSTRACT The seed morphology of the two species of Erica sect. Callicodon, E. carnea and E. erigena, was studied by examining several populations of each species. Photographs, including SEM pictures, of seeds were taken, and size and shape were recorded. Weight and seed colour were also analysed. Seed characters are constant within species, and therefore of high taxonomic value. Elongation of surface cells, number of cells in the main axis, and morphology of outer anticlinal walls are the main discriminant characters between these species. In our opinion, the specific level is the correct taxonomic treatment for these two taxa. E. erigena subsp. hibernica does not seem to differ from E. erigena.

Seed morphology and systematics of the European species of Erica L. sect. Gypsocallis Salisb. (Ericaceae)

Abstract The European heathers Erica manipuliflora, Erica multiflora and Erica vagans (sect. Gypsocallis) are related species characterized by a glabrous ovary, exerted, muticous anthers and a pale pink, urceolate corolla. The existence of three species is the most accepted treatment for this group, but there are uncertainties about this taxonomic interpretation. In this article, we used seed morphological characters to assess the systematics of the group. Seeds were studied by means of scanning electron microscopy techniques. E. multiflora has a distinct seed type, 1–1.5 mm long, flattened, yellowish with a striate-reticulate primary sculpture. E. vagans and E. manipuliflora have smaller seeds, brown with a reticulate pattern. Seeds of E. vagans are globose, 0.5 mm wide, while E. manipuliflora has mostly ellipsoid seeds 0.7 mm long. However, seeds of E. manipuliflora from the Adriatic coasts are closer to those of E. vagans, and this may support the existence of E. manipuliflora subsp. anthura.

Two wild hybrids of Erica L. (Ericaceae) from northwest Spain

Two hybrids of genus Erica L. are recorded from northwest Spain. Erica x stuartii (MacFarl.) Mast. (E. tetralix L. x E. mackaiana Bab.) is recorded from Aranga (A Coruna, NW Spain). Hitherto this hybrid was only known from Ireland and Asturias (N Spain). Erica x veitchii Bean (E. arborea L. x E. lusitanica Rudolphi) is recorded from Asturias for first time in the wild. E. lusitanica corresponds to the recently described subspecies cantabrica Fagundez & Izco, therefore a new name for the nothosubspecies is proposed: E. x veitchii nothosubsp. Asturica nothosubsp. nov.

Seed morphology of Erica L. sect. Tylospora Salisb. ex I. Hansen

Seed morphology of Erica australis L., the only species of section Tylospora, was studied. SEM pictures were taken of whole seeds and details. Quantitative characters were analyzed using one-way analysis of variance. Other secondary characters such as weight of 100 seeds and color were also recorded. Two main seed types were observed; the main discriminant characters were the caruncle length and the elongation of the seed body. This finding supports the existence of two subspecies, australis and aragonensis with a north-south gradient in morphological variation between the two subspecies, with intermediate populations in contact areas. The presence of a caruncle and the inconspicuous anticlinal walls of the surface cells are only found in this species within Erica genus in Europe.