Luis G. Quintanilla

Impacts of changes in land use and fragmentation patterns on Atlantic coastal forests in northern Spain

Changes in forested landscapes may have important consequences for ecosystem services and biodiversity conservation. In northern Spain, major changes in land use occurred during the second half of the 20th century, but their impacts on forests have not been quantified. We evaluated the dynamics of landscape and forest distribution patterns between 1957 and 2003 in Fragas do Eume Natural Park (northwestern Spain). We used orthoimages and a set of standard landscape metrics to determine transitions between land cover classes and to examine forest distribution patterns. Eucalypt plantations showed the greatest increase in area (197%) over time. Furthermore, transitions to eucalypt plantations were found in all major land cover classes. Forest showed a net decline of 20% in total area and represented 30% of the landscape area in 2003. Forest losses were mainly due to eucalypt plantations and the building of a water reservoir, while forest gains were due to increases in shrubland, meadows and cultivated fields which had been recolonised. Forest patch size and core area decreased, and edge length increased over time. In turn, increases were obtained in mean distance between forest patches, and in adjacency to eucalypt plantations and to a water reservoir. These results suggest an increase in forest fragmentation from 1957 to 2003, as well as a change in the nature of the habitat surrounding forest patches. This study shows that land use changes, mostly from eucalypt plantation intensification, negatively affected forested habitats, although some regeneration was ongoing through ecological succession from land abandonment.

Microsatellites reveal substantial among-population genetic differentiation and strong inbreeding in the relict fern Dryopteris aemula

BACKGROUND AND AIMS A previous study detected no allozyme diversity in Iberian populations of the buckler-fern Dryopteris aemula. The use of a more sensitive marker, such as microsatellites, was thus needed to reveal the genetic diversity, breeding system and spatial genetic structure of this species in natural populations. METHODS Eight microsatellite loci for D. aemula were developed and their cross-amplification with other ferns was tested. Five polymorphic loci were used to characterize the amount and distribution of genetic diversity of D. aemula in three populations from the Iberian Peninsula and one population from the Azores. KEY RESULTS Most microsatellite markers developed were transferable to taxa close to D. aemula. Overall genetic variation was low (H(T) = 0.447), but was higher in the Azorean population than in the Iberian populations of this species. Among-population genetic differentiation was high (F(ST) = 0.520). All loci strongly departed from Hardy-Weinberg equilibrium. In the population where genetic structure was studied, no spatial autocorrelation was found in any distance class. CONCLUSIONS The higher genetic diversity observed in the Azorean population studied suggested a possible refugium in this region from which mainland Europe has been recolonized after the Pleistocene glaciations. High among-population genetic differentiation indicated restricted gene flow (i.e. lack of spore exchange) across the highly fragmented area occupied by D. aemula. The deviations from Hardy-Weinberg equilibrium reflected strong inbreeding in D. aemula, a trait rarely observed in homosporous ferns. The absence of spatial genetic structure indicated effective spore dispersal over short distances. Additionally, the cross-amplification of some D. aemula microsatellites makes them suitable for use in other Dryopteris taxa.

Development of a naturally miniaturised testing method based on the mitochondrial activity of fern spores: a new higher plant bioassay.

One of the main concerns of current environmental toxicology is the low number of taxa used for standard bioassays. Ferns, with more than 10,000 living species, are the second largest group of vascular plants and are important components of numerous plant communities. Fern spores and gametophytes have long been recognized as useful models for plant research since they constitute a naturally miniaturised and economic higher plant model. Mitochondria are the main energy source in eukaryotic cells and any toxic damage will affect the whole organism. The reduction of tetrazolium salts to water-insoluble coloured formazan salts by the respiratory chain has been used for more than 50 years as a measure of cell mitochondrial activity and viability in eukaryotic organisms. Here, the reduction of 2,3,5-triphenyltetrazolium chloride (TTC) by mitochondria is adapted and optimized to measure fern spore or gametophyte viability. Procedures selected as optimum in the model species Dryopteris guanchica are as follows: bleach sterilization, incubation without shaking at 20 degrees C in the dark for 1-4h with 0.05-1.5% TTC in Dyer medium supplemented with 0.001-0.005% Tween 20 at pH 8. We conclude that this method constitutes a promising low cost bioassay for higher plant toxicity during development.

A Comparative Study of the Gametophytic Generation in the Polystichum aculeatum Group (Pteridophyta)

The gametophytic generation of the allotetraploid Polystichum aculeatum and its diploid parents, Polystichum setiferum and Polystichum lonchitis, was studied in order to compare their morphology, gametangial ontogeny, and breeding system. Six populations, two of each species, were selected for spore collection. Germination, gender expression, and antheridiogen experiments were established on agar and soil culture media. Germination percentage in the tetraploid was higher, and the only morphological difference was found in the length of marginal hairs that were also longer in P. aculeatum. Gender expression in the allotetraploid was a mixture of the diploids. Differences in gender expression of both diploids, with many male prothalli in P. lonchitis and many female ones in P. setiferum, may favor the formation of the hybrid that originated the allotetraploid. An antheridiogen system was observed in both P. aculeatum and P. setiferum, and each species responded to one another’s antheridiogen. In contrast, exudates from P. lonchitis failed to induce precocious maleness within the species but did induce an antheridiogen response in gametophytes of P. setiferum.

Allozyme variation in the sympatric ferns Culcita macrocarpa and Woodwardia radicans at the northern extreme of their ranges

Isozymes were used to study genetic variation in the clonal ferns Culcita macrocarpa and Woodwardia radicans in the northwestern Iberian Peninsula, their northern distributional limit. Despite their high chromosome numbers, both species were isozymic diploids. In C. macrocarpa all 18 resolved loci were monomorphic, with the same allele in all ramets from all populations. In W. radicans only two of the 16 interpreted loci were polymorphic, with two alleles per locus; ramet-level genotypes showed Hardy-Weinberg equilibrium, indicating an intergametophytic mating system; the number of genets distinguished was 1–3 per population; and among-population variation was low (FST = 0.231), suggesting effective gene flow (i.e. spore exchange). More generally, the very low (W. radicans, HT = 0.012) or zero (C. macrocarpa) genetic diversity detected in the present study may be due to genetic drift associated with the reduction of populations in the last glaciation, and to founder effects in the subsequent Holocene expansion.

Genetic variation in the allotetraploid Dryopteris corleyi (Dryopteridaceae) and its diploid parental species in the Iberian Peninsula

Studies on genetic diversity help us to unveil the evolutionary processes of species and populations and can explain several traits of diploid-polyploid complexes such as their distributions, their breeding systems, and the origin of polyploids. We examined the allozyme variation of Dryopteris aemula and D. oreades, diploid ferns with highly fragmented habitats, and the allotetraploid D. corleyi to (1) analyze the putative relationship between both diploids and the tetraploid, (2) compare the levels of genetic variation among species and determine their causes, and (3) assess the breeding system of these taxa. The allozymic pattern of D. corleyi confirms that it derived from D. aemula and D. oreades. The lack of genetic diversity in D. aemula, a species of lowland habitats, may be due to genetic drift associated with the contraction of populations in the last glaciation. By contrast, the alpine D. oreades had moderate intrapopulation genetic variation, which may derive from the expansion of populations during the last glaciation. In the latter species, low interpopulational variation suggested effective gene flow (spore exchange), and genotype frequencies in Hardy-Weinberg equilibrium indicated cross-fertilization of gametophytes. Evolutionary history appears to be an essential element in the interpretation of genetic variation of highly fragmented populations.

Reproductive and competitive interactions among gametophytes of the allotetraploid fern Dryopteris corleyi and its two diploid parents.

BACKGROUND AND AIMS Several models predict that the establishment of polyploids within diploid populations is enhanced by non-random mating (i.e. selfing and assortative mating) of cytotypes and by a higher relative fitness of polyploids. This report assesses the role that antheridiogens (i.e. maleness-inducing pheromones) and intercytotype differences in growth rate have on polyploid performance. METHODS Three buckler-fern species were studied: the allotetraploid Dryopteris corleyi and its diploid parents, D. aemula and D. oreades. In one experiment, gametophytes of these species were cultured under rich growth conditions to compare the timing of gametangia production. The substrata on which these gametophytes had grown were used as antheridiogen sources in a second experiment. The three species were combined as source and target of antheridiogen (i.e. nine species pairs). Timing of antheridia production and gametophyte size were determined after those antheridiogen treatments. KEY RESULTS Under rich growth conditions the allotetraploid produced archegonia earlier than those of diploid parents. Female gametophytes of the three species produced antheridiogens that inhibited growth and favoured maleness both within and among species. Gametophyte size was similar in the three species but antheridia formed earlier in the allotetraploid. CONCLUSIONS Unisexuality, promoted by non-specific antheridiogens, enhances random mating both within and among species. The resulting hybridization can favour the reproductive exclusion of the allopolyploid in sites where it is outnumbered by diploids. However, the earlier production of gametangia in the allotetraploid favours assortative mating and may thus counterbalance reproductive exclusion.

Spore Maturation and Release of Two Evergreen Macaronesian Ferns, Culcita macrocarpa and Woodwardia radicans, along an Altitudinal Gradient

Abstract The variables affecting spore phenology have been poorly studied in contrast with the abundant literature on leaf phenology. This paper deals with the influence of altitude and canopy cover on spore maturation and release of Culcita macrocarpa and Woodwardia radicans in the island of São Miguel, Azores. The study was conducted during one sporing season at three altitudes (400, 600, and 800 m). In both species spore maturation occurred in autumn and may be controlled by the previous accumulation of photosynthates. Spores were not released until late winter owing to a requirement for dry weather conditions. Dispersal took place later at higher altitude, due to lower temperature and higher humidity. This gradual liberation of spores along an altitudinal gradient is important for the endemic Azores bullfinch Pyrrhula murina (a bird that feeds on spores in winter), providing food over an extended period.

The nothofagus nitida (Phil.) Krasser woodlands of southern Chile in the northern half of their range: phytosociological position

Abstract A phytosociological study of the temperate rain forests dominated by an evergreen species endemic to Chile, one of the highest-rainfall woodland types of temperate South America, included within the geobotanical concept of North Patagonian Forest. Relevés were taken from throughout an area comprised between 40° and 44° 40′ South, in which these woodlands show highest floristic richness. The communitys floristic and structural diversity are described and proposed as an independent association, Luzuriago polyphyllae-Nothofagetum nitidae ass. nova. The ultrahyperhumid character of this association is evidenced by the number of Hymenophyllaceae species (filmy ferns) that may occur within it.

Isozymic Contribution to the Systematics of the Asplenium seelosii Group

Abstract The systematics of the Asplenium seelosii complex have been debated for a long time. This complex includes strictly rupicolous plants that live on limestone cliffs mainly in mountains of southwest Europe: the Alps, the Pyrenees, and several mountain ranges of the Eastern Iberian Peninsula. The disjunct distribution of the populations and several morphological characters, i.e., leaf indumentum and the structure of the perispore, have been used to distinguish species and subspecies. The goal of this study was to evaluate the different systematic treatments of this complex by means of isozyme electrophoresis. Seventeen populations throughout the range of the complex were studied, and 15 enzymatic systems were assayed. There was no within population genetic variation and genetic identity between populations varied widely. Analysis of isozymic data clearly differentiated two groups corresponding to the species proposed, Asplenium seelosii and A. celtibericum, but these data do not support the recognition of subspecies in this complex.