Genetic diversity within and among two Argentinean and one Mexican species of Acacia (Fabaceae)

Acacia is a pantropical genus comprising > 1450 species. Following Vassal's treatment Acacia is considered as a single genus with three subgenera (Acacia, Aculeiferum and Phyllodineae). Acacia caven, A. curvifructa and A. farnesiana belong to subgenus Acacia and the relationship between them is controversial. The aim of this study was to elucidate the relationship between the three species using amplified fragment length polymorphism, analysing 15 populations of these species, and to compare the results obtained with those from a morphological analysis. Genetic diversity indices (percentage of polymorphic loci, genetic diversity) showed that genetic variation in A. caven is higher than that in A. curvifructa and A. farnesiana. Of the total genetic diversity in A. caven and A. farnesiana, most is found within populations (∼70%). Analysis with STRUCTURE showed that the optimal number of clusters (K) was ten, and in all cases where populations were grouped they were geographically close and/or belong to the same variety. The morphological canonical discriminant analysis did not result in a separation between all individuals, indicating that they do not harbour consistent morphological discontinuities. Altogether, the results of our molecular analyses showed the existence of significant differences between A. caven, A. curvifructa and A. farnesiana, which argues for recognizing them as different species. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 593–606.     

Polymorphism and geographic variation of flower color in chilean populations ofEschscholzia californica

In twelve populations ofEschscholzia californica from central Chile, where it was introduced in the latter part of the 19th century, there is a regular gradient in frequency of the allelesJ andj, which control orange vs. yellow flowers, ranging from a maximum value of 0.531 to a minimum of 0.160 forJ. Populations having higher values ofJ occupy more mesic sites. In addition, the great majority of the populations have significant excess of heterozygotes over those expected on the basis of theHardy-Weinberg equilibrium, and so exhibit balanced polymorphism for theJ-j pair of alleles, probably associated with heterosis ofJj genotypes. Evidence is presented which suggests that this locus serves as a marker for adaptative gene complexes rather than being itself associated with adaptation. In Chile, the association ofJJ genotypes with cooler, moister habitats is the opposite of the condition existing in California, and suggests that extensive reorganization of the gene pool, through changed linkage relationships, took place asE. californica populations were being established in Chile.     

The Chilean Espinal: Restoration for a Sustainable Silvopastoral System

The mediterranean habitats of central Chile are rich in endemic species, but threatened by land‐use changes. In this context, we suggest that restoration of the traditional espinal silvopastoral system could improve its sustainability and conservation value. Past research on the espinal embraced negative stereotypes of peasants, the tree Acacia caven, and the semiarid landscape to recommend abandoning the silvopastoral system. We think that recommendation is premature and ignores the value of the espinal as a classical Chilean cultural landscape. Drawing on lessons from silvopastoral systems in Latin America and the Mediterranean, here we suggest several management interventions and incentives that could be developed to restore the espinal. Particular challenges in espinal include low biomass production due to the semiarid climate and the lack of a traditional sustainable timber or non‐timber product of A. caven. Our recommendations include sustainable production and use of biochar and bark extracts from A. caven to improve espinal soils, the promotion of shrubs and the use of small mammal disturbances, and their artificial analogs to improve A. caven reproduction, and rotational livestock herding to form mosaic landscapes. These techniques could lead to higher forage biomass and increased livestock weights. Incentive structures to implement these management activities could include tax benefits for private protected area (IUCN category VI) creation, REDD+ and PES programs, along with promotion of the cultural value of the espinal. Further research is urgently called for on ecosystem services, ecological baselines, biochar, and other management and incentive structures that could be applied in the espinal.     

Nanism and ephemerism as reasons for a hidden abundance in vernal pool plants: The example of Lepuropetalon spathulatum in Chile

Minute size (nanism) and short live cycle (ephemerism) are characteristic features of many plants living in seasonal wetlands in Mediterranean biomes. Lepuropetalon (Celastraceae) is a monotypic genus with an antitropical distribution (disjunct in temperate regions of both Americas). L. spathulatum is the smallest vascular plant of Chile, not recorded in herbaria for decades. Its distribution, ecology and phytosociology were studied based on herbarium vouchers and field observations. L. spathulatum occurs in the fringes of vernal pools, on oligotrophic sandy soils and in grazed Acacia caven pseudo‐savannas. Its distribution is linked to the Mediterranean and Submediterranean bioclimates. Associated species are other dwarfish annuals, many of them originating from the Western Palearctic subkingdom and characteristic for the class Isoëto‐Nanojuncetea. Other floristic elements are Chilean endemics and species with a disjunction to California (character species of the Nanojuncetea australis). L. spathulatum is not a rare plant in Chile, but is often overlooked because of its dwarfish and ephemeral habit. Although most populations occurred in secondary habitats and the species can tolerate disturbance, intensification of agriculture, forest plantations and modification of the hydrological conditions may threaten the species in the long term. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

THE ANNUAL RHYTHM OF CAMBIAL ACTIVITY IN TWO WOODY SPECIES OF THE CHILEAN “MATORRAL”

The annual rhythm of cambial activity is compared in Proustia cuneifolia and Acacia caven, two typical shrubs of the “matorral” in the semiarid region of central Chile. Proustia, a drought deciduous shrub, shows a typical desert cambial rhythm, highly sensitive to rainfall. The growth activity of this species is limited to the periods of adequate moisture. Acacia is an evergreen whose cambial activity is observed almost throughout the year; it is not synchronous with rainfall. Adaptation in this species seems to consist in developing long roots able to tap underground water. These results indicate that both shrubs, although growing together, have different adaptive strategies to the same xerophytic conditions.     

Assessment of populations ofGracilaria chilensis (Graeilariales,Rhodophyta) utilizing RAPDs

Phenotypic variability and mixing of material due to massive cultivation for commercial purposes has contributed to the taxonomic confusion ofGracilaria in Chile. At least four species with cylindrical thalli and similar morphology have been recorded. However, since establishment ofG. chilensis, most of the collected thalli have been attributed to this species despite the lack of diagnostic features. In an attempt to resolve whetherGracilaria from 3 localities where it grows in natural and artificial populations belongs to the same species, gametophytic samples were compared by applying RAPD-PCR to their total DNA. This was analysed using 25 different 10-mer primers from which 21 revealed polymorphism within and between populations. Similarity matrices and cluster analyses were performed based on the presence/absence of bands representing fragments of DNA generated by random amplification. Similarity values between two of the populations were equivalent to those detected within a third, indicating the mixing of genetic material due to transplant between the two former localities. Similarities between samples of ChileanGracilaria andG. tenuistipitata from Sweden are considerably lower (0.45–0.53) than those between populations from Chile (0.74–0.88), confirming the existence of a single specific taxon,G. chilensis, in these three localities.     

Differential growth response to arbuscular mycorrhizal fungi and plant density in two wild plants belonging to contrasting functional types

The effect of arbuscular mycorrhizal fungi (AMF) on plant growth was examined in two wild plant species belonging to contrasting functional types: an annual forb (Bidens pilosa, Asteraceae) and a deciduous shrub (Acacia caven, Fabaceae) at three contrasting plant densities (one, two, and three individuals per pot). AMF had a slightly negative effect on B. pilosa when the species grew in isolation while they positively affected A. caven. Positive effects of AMF on shoot mass of A. caven decreased at higher plant densities, while shoot mass of individuals of B. pilosa showed less marked differences between plant densities. When considering total biomass per pot, AMF positively affected A. caven growth while negatively affecting B. pilosa, at all three plant densities. Root/shoot ratio per pot was negatively affected by AMF but not plant density in both species. These findings highlight the importance of including plants belonging to different life forms and/or traits in research regarding the interaction between AMF and intraspecific plant competition.     

Mating system parameters and genetic structure in Argentinean populations of Acacia caven (Leguminosae, Mimosoideae)

Acacia caven (Mol.) Mol. is native to South America. The species is a leguminous, woody small tree that is considered to have certain potential as a managed silvopastoral crop. Six varieties have been described for the species based on both morphological traits and molecular markers. Little information is available on its mating system. The main objectives of this work were to test the hypothesis that A. caven is an outcrosser and to estimate parameters of its mating system and population structure on the basis of isozyme markers. In the four populations studied, a high homozygote excess was found in the progeny population but not in the mother plant genotypes. The estimate for the multi-locus outcrossing rate (t _m) was high (??0.957) in all populations, indicating that Acacia caven is a predominantly outcrosser species. The results of genetic structure analysis within each population indicated that differences in allelic frequencies among families in all of the populations studied are highly significant. The difference in F estimates between progeny and mother plants suggests some selection favouring heterozygotes between the seedling and adult stages. Therefore, a strategy for ex situ conservation might emphasise sampling more populations with a relative large number of trees per site.     

Landscape genetic structure of natural populations of Acacia caven in Argentina

Acacia caven is a South American species which shows remarkable climate tolerance and ecological adaptability; as such, this species is suitable for colonizing anthropogenically degraded sites. This species is widely distributed, and six varieties have been described based on both morphological traits and molecular markers. Moreover, Aronson (1992) suggests that, for this species, geographical separation could be associated with ecological differentiation. In this study, amplified fragment length polymorphisms were used to study genetic variation within and among 15 populations of A. caven from five eco-regions of Argentina and to investigate (1) whether the varieties are genetically coherent, (2) whether the varieties correspond consistently to a single eco-region, (3) the proportion of the species diversity explained within and among varieties and eco-regions. Eight of the 225 bands appear to be under positive selection. The remaining 217 neutral loci showed a high percentage of polymorphism (99.1%). The estimates of genetic diversity H _j were generally high. The F _ST (0.315) was highly significant, providing evidence for genetic structure among populations. Hierarchical analysis of molecular variance indicated that variation among eco-regions was 8.2% and highly significant. The higher component of variance was found within populations (67.5%). STRUCTURE analysis suggested that the optimal number of K?=?11. The results showed that, in most cases, geographic separation is associated with ecological differentiation. Since differentiation of A. caven populations studied here in eco-regions was highly significant, sampling should include a large number of trees within populations as well as covering the wide ecological diversity of the species.     

Intra- and interspecific variation in body size ofProtohermes (Megaloptera: Corydalidae)

The life history of three populations ofProtohermes grandis and two populations ofProtohermes immaculatus (Megaloptera: Corydalidae) was compared. In general, the larvae lived in stream riffles for 2 years and the adults appeared in summer. Adult body size differed between these closely related species and also between the populations ofP. grandis. Dwarfism occurred inP. immaculatus, a species that is endemic to the small, isolated island, Amami Island. The population ofP. grandis on Yaku Island, located between Amami Island and the mainland Kyushu, had an intermediate body size between that ofP. immaculatus and the mainland population ofP. grandis. Despite being an insular population,P. grandis on Tsushima Island had a similar body size to mainlandP. grandis. In these populations with large adults, some larvae lived in the streams for 3 years. The size distribution of benthic animals, which are the prey available toProtohermes larvae, differed between the streams studied. The density of large prey was lowest on Amami Island, intermediate on Yaku Island, and highest on the mainland and Tsushima Island. Different size distributions of available prey may be caused by the differences of benthic fauna; most of Ecdyonuridae and Ephemerellidae (large mayflies) and Perlidae (large stoneflies) were not found on Amami and Yaku Islands. Thus, there is a tendency to dwarfism in the populations ofProtobermes inhabiting streams where the density of large prey is low.     

The Miocene Architectonicidae (Gastropoda) of Chile

Three new species of Architectonicidae Heliacinae,Heliacus (Torinista) chonos, Heliacus (Grandeliacus) antu andSolatisonax bieleri, are described. These include the first reports ofGrandeliacus andSolatisonax from Chile.Solarium australe Philippi, 1887 is an earlier name forHeliacus (Torinista) bahamondei Frassinetti & Covacevich, 1981, but is a junior homonym ofS. australe Philippi, 1849. Type material and new specimens of the five previously described architectonicid species from Chile are described and figured for comparison. Together with other gastropod taxa from the same deposits, Architectonicidae provide evidence for tropical to subtropical water temperatures in central Chile during the early Miocene.     

Offspring performance and recruitment of the pioneer tree Acacia caven (Fabaceae) in a fragmented subtropical dry forest

The process of habitat fragmentation results in the breaking apart of originally continuous habitats, causing multiple changes in biotic and abiotic interactions. Alterations in resource availability and in mutualistic and antagonistic plant–animal interactions may impact plant offspring quantity and quality. Currently, several old fragmented systems evidence a process of flora homogenization, where shade‐tolerant species are replaced by pioneer light‐demanding species. Notably, the relationship between quantity and quality parameters of plant offspring production and the successful recruitment of pioneer species in fragmented forests has been poorly explored. Here, we assess population size, sapling recruitment and offspring performance of one of the most widespread tree species of subtropical South America, the native pioneer Acacia caven (Fabaceae). Population size of adults and saplings increased from small to continuous forests, whereas the sapling recruitment per adult tree (sapling/adult ratio) showed no significant differences among forests of different size. Seedling performance was negatively related to forest area and population size, implying potential superior competitive ability of seedlings produced in smaller populations compared to larger ones. Our results show that A. caven is resilient to habitat fragmentation effects, which may be ascribed to a set of advantageous ecological traits such as outcrossing, massive flowering, generalist pollination, drought resistance, rapid growth and re‐sprouting. Thus, this pioneer tree benefits from the availability of vacant sites and resources released by declining plant populations of other species, eventually becoming the dominant species in fragmented habitats. Pioneer native plant species with ecological traits such as A. caven may represent the silent successful survivors and new colonizers of fragmented habitats, the ubiquitous landscapes of the future.     

Genetic variability and interpopulational differentiation of Artemia strains from South America

Seven Artemia samples from three South American countries (Chile, Brazil, Peru) were studied by starch electrophoresis with the aim of comparing levels of genetic variation and genetic similarity to representative populations of A. franciscana (San Francisco Bay, California, USA) and A. persimilis (Buenos Aires, Argentina), which are species endemic to the New World. Based on the analysis of 22 loci, parameters measuring genetic variability were, for some populations, found to be among the highest reported for Artemia so far. The percentage of polymorphic loci varied from 31.8% (Piura, Peru; Buenos Aires) to 50% (Los Vilos and Salar de Atacama, Chile), while the observed heterozygosity varied from 0.025 (Piura) to 0.165 (Los Vilos, Chile). A dendrogram based on Nei's genetic distance (D) produced four major groups. The Argentinian form, A. persimilis; the San Francisco Bay strain together with samples from Brazil (Macau and Rio Grande do Norte) and Chile (Pichilemu and Salar de Atacama); two coastal populations from Chile (Los Vilos and Iquique) and the sample from Peru (Piura). These four groups have inter-group D values that are, in some cases, far above those normally associated with conspecific populations.     

Frequent fires do not affect sexual expression and reproduction in Vachellia caven

In environments with high fire frequency the impoverishment of abiotic resources may favour male sexual expression in plants as it is less costly than female expression. Also, fire can modify pollinator communities and thus affect plant reproduction. Here we evaluate the effect of frequent fires on sexual expression, pollination and reproductive success of Vachellia caven (Leguminosae), an andromonoecious tree that is highly dependent on animal pollination and is abundant in burned sites. We expect that increased fire frequency will favour maleness but it will decrease reproductive success due to abiotic resource depletion in repeated burned sites. To test this, we selected focal plants in three unburned sites and three frequently burned sites and measured their sexual expression, basal diameter, pollination and fruit set. The proportion of male inflorescences per plant was not affected by fire and it was negatively related with the diameter of the plant. The proportion of pollinated flowers was not affected by fire, and fruit set increased with maleness only in frequently burned sites. These results indicate that V. caven is adapted to regimes of high fire frequency: not only was there similar fruit set in both burned and unburned sites, but more male plants had higher fruit set in burned sites. Despite the soil impoverishment triggered by repeated fires, V. caven is able to maintain its sexual and reproductive functions, allowing it to persist and maintain viable populations in fire‐prone environments. Abstract in Spanish is available with online material.     

Ecological differences among Chilean populations of commercialGracilaria

Field farming ofGracilaria is gradually replacing use of the wild crop in Chile. The most popular planting method consists of establishing underground thallus systems for patches ofGracilaria on wave-sheltered, soft-bottom habitats. Commercial cultivation often involves transplanting vegetative material to distant places along the coast. This study shows that native populations possess some ecological differences that might affect cultivation success. Seven environmental factors were tested for their effects on growth of four geographically separated populations belonging to two species ofGracilaria. No specific or population differences were found under various temperature or salinity regimes. Specific differences occurred in responses to irradiance, daylength, sand burial and sand abrasion. Responses to epiphytes differed among both population and species. Epiphyte recruitment was inhibited by some populations and stimulated by others. Given the farming methods presently used in Chile, these results have ecological and economical importance, as they suggest that transplanting randomly from one to other type of habitat does not assure cultivation success.     

Low genetic differentiation betweenAdiantum capillusveneris L. andA. ogasawarense Tagawa (Adiantaceae), an endemic pteriodophyte of the bonin (ogasawara) islands

Genetic differentiation was examined betweenAdiantum capillus-veneris L. andA. ogasawarense Tagawa. A total of 136 individuals from two populations ofA. ogasawarense and three populations ofA. capillus-veneris were sampled. Allozymes encoded by 19 putative loci for nine enzyme systems were observed. The populations ofA. ogasawarense are genetically differentiated from those ofA. capillus-veneris; conspecific populations cluster together. However, genetic identity between two species was estimated to be 0.815, and indicates that the degree of allozyme differentiation is lower than those between endemic flowering plants and their progenitors. It is possible that the low genetic differentiation observed betweenA. ogasawarense andA. capillus-veneris results from a recent origin of the endemic species,A. ogasawarense.     

Worldwide occurrence of virus-infections in filamentous marine brown algae

Virus infections were detected inEctocarpus siliculosus andEctocarpus fasciculatus on the coasts of Ireland, California, Peru, southern South America, Australia and New Zealand; in threeFeldmannia species on the coasts of Ireland, continental Chile and Archipelago Juan Fernandez (Chile); and inLeptonematella from Antarctica. Natural populations on the Irish coast contained 3% infected plants inE. fasciculatus, and less than 1% inFeldmannia simplex. On the Californian coast, 15 to 25% ofEctocarpus isolates were infected. Virus symptoms were absent inE. siliculosus from Peru, but appeared after meiosis in laboratory cultures. The virus particles inE. fasciculatus are identical in size and capsid structure to those reported forE. siliculosus, while the virus inF. simplex is smaller and has a different envelope. Our findings suggest that virus infections are a common and worldwide phenomenon in filamentous brown algae.     

Tracking the origin of an invasive species: Drosophila subobscura in Argentina

Biological invasions are excellent opportunities to study the evolutionary forces leading to the adaptation of a species to a new habitat. Knowledge of the introduction history of colonizing species helps tracking colonizing routes and assists in defining management strategies for invasive species. The Palearctic species Drosophila subobscura is a good model organism for tracking colonizations since it was detected in Chile and western North America three decades ago and later on in the Atlantic coast of Argentina. To unravel the origin of the Argentinean colonizers two populations have been analysed with several genetic markers. Chromosomal arrangements and microsatellite alleles found in Argentina are almost similar to those observed in Chile and USA. The lethal allelism test demonstrates that the lethal gene associated with the O₅ inversions in Argentina is identical to that found in Chile and USA, strongly supporting the hypothesis that all the American colonizing populations originated from the same colonization event. A secondary bottleneck is detected in the Argentinean populations and the genetic markers suggest that these populations originated from the invasion of 80–150 founding individuals from Chile.     

In vitro recruitment of Ulva sp. and Enteromorpha sp. on gametophytic and tetrasporophytic thalli of four populations of Chondracanthuschamissoi from Chile

Chondracanthus chamissoi is a red alga which is acquiring an increasing economic importance in Chile and becoming a target species for cultivation. Because epiphytism is a major problem in the mariculture of seaweeds, the recruitment of Ulva sp. and Enteromorpha sp. on gametophytic (cystocarpic) and tetrasporophytic thalli of C. chamissoi was tested in vitro on four populations from different locations in Chile. For Ulva sp., the density, cover and length of the recruits varied between the reproductive phases of the host and among the studied populations of C. chamissoi. In most experiments, a larger number of epiphytic thalli was observed on gametophytic plants of C. chamissoi; populations from Calderilla and Lechagua had a higher resistance to epiphytism. For Enteromorpha sp., its ability to grow epiphytically on both phases of the host showed a greater variability, but was inferior to that of Ulva sp. The differential resistance to epiphytism in both reproductive phases and in plant origin indicates the possibility of obtaining selected strains of C. chamissoi with lower susceptibility to epiphytism that could be utilized in planning maricultural programs.