RFLP analysis of the mitochondrial DNA of otters (Lutra lutra) from Europe—implications for conservation of a flagship species

The distribution of otters (Lutra lutra) in Europe is largely fragmented, mainly due to historic anthropogenic causes. Nevertheless, in eastern Germany a large coherent area is inhabited by a viable otter population. In this paper, the mitochondrial genome of 81 otters is studied by RFLP analysis of PCR-amplified 1.5 and 2.5 kb long fragments, particularly to estimate the amount of genetic variability of European otters, and to identify possible geographical population subsets for conservation management. No restriction site polymorphism was detected within the control region (1.5 kb), but polymorphism of cleaving sites in the 2.5 kb fragment could be assigned to three haplotypes. Two occurred exclusively in a comparatively small area northwest and west of Berlin, which may be considered a region of increased genetic variability in otters. The low level of mtDNA variability in European otters might be due to genetic drift in postglacial founder populations with long-term low densities, and continuous historical overhunting.     

Genome sizes and ploidy levels in Mexican cactus pear species Opuntia (Tourn.) Mill. series Streptacanthae Britton et Rose, Leucotrichae DC., Heliabravoanae Scheinvar and Robustae Britton et Rose

The ploidy levels and amounts of DNA of 23 Opuntia species from Mexico were determined by flow cytometry. Four different ploidy levels (2n = 2x, 2n = 4x, 2n = 6x, 2n = 8x) with 2C-DNA amount ranging from 4.17 pg (Opuntia incarnadilla Griffiths) to 6.53 pg (Opuntia heliabravoana Scheinvar) were determined among the samples analyzed. Polyploidy is widespread (93%) among these Opuntia species. Opuntia heliabravoana Scheinvar was the sole diploid species. Opuntia leucotricha DC. (2C = 5.71 pg), Opuntia spinulifera Salm-Dyck (2C = 5.51 pg), Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F. A. C. Weber) Bravo (2C = 4.98 pg), and Opuntia elizondoana E. Sánchez et Villase?or (2C = 5.29 pg) were tetraploids. Opuntia oligacantha C.F. F?rst. (2C = 5.33 pg), Opuntia incarnadilla Griffiths and Opuntia matudae Scheinvar (2C = 5.25 pg) were hexaploids. Opuntia zamundioi Scheinvar (2C = 4.35 pg), Opuntia lasiacantha Pfeiff. (2C = 4.88 pg), Opuntia hyptiacantha F.A.C. Weber (2C = 4.84 pg), Opuntia streptacantha Lem. ssp. streptacantha (2C = 4.64 pg) and Opuntia streptacantha Lem. subsp. aguirrana Scheinvar et A.␣Rodríguez (2C = 4.43 pg), Opuntia megacantha Salm-Dyck (2C = 5.01 pg), Opuntia joconostle F.A.C. Weber. ex Diguet (2C = 4.70 pg), Opuntia ficus-indica (L.) Miller (2C = 4.90 pg), Opuntia albicarpa Scheinvar (2C = 4.80 pg), Opuntia␣amarilla Griffiths (2C = 4.84 pg), Opuntia chavena Griffiths (2C = 4.70 pg), Opuntia cochinera Griffiths (2C = 5.10 pg), Opuntia fuliginosa Griffiths (2C = 4.64 pg), Opuntia pachona Griffiths (2C = 4.70 pg), Opuntia cretochaeta Griffiths (2C = 4.35 pg), Opuntia rzedowskii Scheinvar (2C = 4.77 pg), Opuntia robusta Wendl. ex Pfeiff. ssp. robusta (2C = 4.98 pg) and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sánchez-Mejorada (2C = 5.05 pg) were all octoploids. The series Streptacanthae Britton et Rose showed a high level of ploidy with octoploid species except for Opuntia heliabravoanae Scheinvar (2n = 2x), Opuntia elizondoana E. Sánchez and Villase?or (2n = 4x) and O. matudae Scheinvar (2n = 6x). Opuntia spinulifera Salm-Dyck was determined to be as a tetraploid species. Series Leucotrichae DC. grouped tetraploid and hexaploid species. The monospecific series Heliabravoanae Scheinvar has one species: Opuntia heliabravoana Scheinvar diploid (2n = 2x). The monospecific series Robustae Britton et Rose seems to be a contradictory group; containing three varieties: Opuntia robusta Wendl. ex Pfeiff. ssp. robusta and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sánchez-Mejorada as octoploid taxa and: Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F.A.C. Weber) Bravo which is tetraploid. In earlier report Rafael del Castillo and Mario González-Espinosa (1988) indicate that the arborescent varieties of this species are diploid and the postrate variety tetraploid. Implications for botanical systematics, genetic resources and breeding are discussed.     

Cross-amplification and characterization of microsatellite loci for three species of <Emphasis Type="Italic">Theobroma</Emphasis> (Sterculiaceae) from the Brazilian Amazon

This study reports on the cross-species amplification of 23 microsatellite markers previously developed for Theobroma cacao L. (Sterculiaceae), source of chocolate in three economically important Amazonian species of Theobroma (T. grandiflorum, T. subincanum, T. sylvestre). Thirteen of the 23 microsatellite loci tested were polymorphic across the three species at 2–13 alleles per locus. The observed heterozygosity per locus varied from 0.18 to 0.84 and expected heterozygosity ranged from 0.28 to 0.87. The high level of transferability and genetic information content of these microsatellite loci indicate their usefulness for population genetic, mating system and breeding studies of these economically important Amazonian fruit trees.     

Oleaster (var. sylvestris) and subsp. cuspidata are suitable genetic resources for improvement of the olive (Olea europaea subsp. europaea var. europaea)

The olive belongs to Olea, a complex genus and to a species with six subspecies. Subsp. europaea includes both the cultivated olive and the oleaster, the wild ancestor of the olive. Little is known on the phenotype of fruits from subsp. cuspidata. We aimed to compare europaea and cuspidata trees for oil content and composition and to verify whether natural hybrids may exist between the two subspecies. Specimens were from Kenya and putative natural hybrids between cuspidata and europaea were from Stellenbosch (South Africa). Cultivar and oleaster trees were sampled in France (continental and Corsica), Italy (Continental and Sardinia) and Tunisia. We have examined the fruit (drupe) structure between subsp. cuspidata and europaea and extracted oil from the pulp, seed and total drupe. Comparison for oil content was made between the cultivated olive and the oleaster and some cuspidata trees from Kenya. A few of cuspidata individuals from Botanical gardens do not enable phenotyping for oil content and composition. Oil composition analyses were performed for the main fatty acids to compare the three taxa. We used microsatellite markers at 11 loci to compute genetic distances between cuspidata, oleaster and cultivar trees and to reveal eventual hybrids. The SSR polymorphisms were huge between the two subspecies and they revealed that putative hybrids were true hybrids sampled around olive orchards. The whole comparison of oil content shows that olive cultivars display higher oil content than the subsp. cuspidata and that the oleaster trees are intermediate, whereas for oil composition of the drupe, cuspidata from Kenya shows less oleic acid than europaea. However, the cuspidata trees show seed oil composition similarities with the other two taxa. The discussion deals with possible reasons to explain the differences and of the possible uses of these taxa for breeding both the olive and brown olive. H. Hannachi and H. Sommerlatte have equal contribution in the article.     

Genetic diversity of core and peripheral Sitka spruce (Picea sitchensis (Bong.) Carr) populations: implications for conservation of widespread species

This study investigated levels of genetic diversity and population differentiation among Sitka spruce (Picea sitchensis) populations classified as core or peripheral based on ecological niche, and continuous or disjunct based on species distribution. Large numbers of trees (N = 200) were sampled from each of eight populations to evaluate the distribution of rare as well as common alleles across the species range. Codominant alleles for eight sequence-tagged site loci were classified based on frequency and geographic distribution in order to develop appropriate sampling strategies to target specific classes of alleles. An important finding of this study is the similarity in genetic diversity as measured by expected heterozygosity between core populations (mean H_E = 0.58) and peripheral populations (mean H_E = 0.56). However, there was significant inbreeding in peripheral (F_IS = 0.17) but not in core (F_IS = 0.03) populations. Large differences in gene flow estimates were observed between core (Nm = 9.0) and peripheral populations (Nm = 3.5). Irrespective of population classification, over 75% of the alleles were common and widespread. Only one allele was classified as rare and localized, and this allele was limited to one core, disjunct and two peripheral, disjunct populations. There was stronger evidence of past bottlenecks in peripheral, disjunct populations than in core, continuous populations. Results are used to suggest sampling strategies for capture of maximum level of genetic diversity and conservation of rare alleles. The conservation of peripheral, particularly disjunct, populations as well as populations in putative glacial refugia may present the best opportunity for conserving rare alleles.     

Decline of an isolated timber rattlesnake (Crotalus horridus) population: Interactions between climate change, disease, and loss of genetic diversity

Extinction of populations from anthropogenic forces rarely has a single cause. Instead, population declines result from a variety of factors, including habitat loss, inbreeding depression, disease, and climate change. These impacts often have synergistic effects that can lead to rapid decline in isolated populations, but case studies documenting such processes are rare. Here, we describe the recent decline of the last known population of timber rattlesnakes (Crotalus horridus) in the state of New Hampshire. We used polymorphic nuclear DNA markers to compare genetic diversity of this population to other populations in the region that are not isolated. We also compare results from ongoing field monitoring of these populations. Genetic analyses reveal that the New Hampshire population lacks genetic diversity and exhibits signs of a recent bottleneck. New Hampshire snakes also exhibited high levels of morphological abnormalities (unique piebald coloration, amelanistic tongues) indicative of inbreeding depression. Furthermore, after a year with exceptionally high summer rainfall, a skin infection of unknown etiology caused significant mortality in the New Hampshire population, whereas other surveyed non-inbred populations were unaffected. This case study demonstrates how different anthropogenic impacts on natural environments can interact in unexpected ways to drive threatened populations toward extinction.     

No-tillage drilling of Italian ryegrass (Lolium multiflorum L.): Crop residue effects, yields and economic benefits

Variable practical results have been observed for no-till (NT) drilling of grasslands in Galicia, northwest Spain. One of the possible explanations to this erratic behaviour could be the influence of different types of stubble on drill performance and grassland emergence. Because the rotation of silage corn (Zea mays L.) with grassland is the most popular rotation in the Galician dairy farms at present, NT drilling of Italian ryegrass on corn stubble and ryegrass stubble was evaluated. Results were compared with NT drilling after shredded stubble and with conventional drilling (with tillage) for 5 years. Annual ryegrass establishment, biomass production, and forage production were measured each year. Treatments considered were: (1) NT on shredded ryegrass stubble; (2) NT on ryegrass stubble; (3) NT on corn stubble; (4) NT on shredded corn stubble; (5) conventional tillage (CT). Better plant stands and more forage production were obtained on the CT and NT-shredded treatments. Allelopathic effects were not observed, and the differences in plant stands among treatments could be caused by the physical effects of stubble and not by its physiological effects. The shredding operation improved plant stands and forage production of Italian ryegrass, which were not influenced by the type of stubble. Years with abundant rainfall negatively affected crop development, which was more evident in NT treatments. NT methods had advantages in terms of timeliness and low economic costs, as compared to CT.     

Conservation of Himalayan medicinal plants: Harvesting patterns and ecology of two threatened species, Nardostachys grandiflora DC. and Neopicrorhiza scrophulariiflora (Pennell) Hong

Himalayan medicinal plants are threatened by large scale exploitation for trade. Research applicable to their sustainable use is largely lacking. We analyze the effects of different harvesting patterns on the population ecology of two highly threatened Himalayan medicinal plants, Nardostachys grandiflora (Valerianaceae) and Neopicrorhiza scrophulariiflora (Scrophulariaceae), in Shey-Phoksundo National Park and in its buffer zone in northwestern Nepal. We first documented local harvesting approaches of two major user groups, amchi (traditional doctors trained in Tibetan medicine), who harvest plants in a selective manner for local health care purposes, and commercial collectors, who harvest unselectively and at much higher intensity for trade. We then applied the selective harvesting approach of amchi in an experiment to test the effects of different harvesting levels on the population ecology of these two species. These experiments revealed a positive effect of low harvesting levels on plant density, but recruitment and survival rates decreased with increasing harvesting levels. We also analyzed the effect of high harvesting pressure for trade on the population ecology of N. grandiflora. Recruitment and survival rates were higher in N. scrophulariiflora than in N. grandiflora; the latter species is more vulnerable to harvesting than the former. The difference between them in sustainability of harvest is related to differences in their strategies of vegetative reproduction and in harvesting practices associated with these strategies. Management of Himalayan medicinal plants can be improved by taking harvesting patterns, plant life forms and growth patterns into consideration.     

Herbicides, weeds and endangered species: management of bitou bush (Chrysanthemoides monilifera ssp. rotundata) with glyphosate and impacts on the endangered shrub, Pimelea spicata

Environmental weed invasion threatens the biodiversity of native species. Unfortunately, managing these weeds may also affect biodiversity adversely. A recent example occurred when glyphosate, a herbicide used to control the highly invasive weed, bitou bush (Chrysanthemoides monilifera ssp. rotundata), accidentally drifted over a small population of an endangered shrub, Pimelea spicata. Following concerns that the affected population would not recover and, thereby, cause the local extinction of P. spicata, we conducted a series of glasshouse and field experiments to explore the impacts of glyphosate on this endangered species. Seedlings and young plants of P. spicata, in which the tap root was undeveloped, were killed by a single application of glyphosate. Older plants with a well developed tap root also died back initially, but about 50% of individuals re-sprouted. This re-growth was associated with a significant decrease in tap root diameter, implying that further disturbance, including repeated treatment with glyphosate, would kill plants by impairing their potential for recovery. Unlike some sclerophyllous native shrubs, the tolerance of P. spicata to glyphosate was limited, even when its growth was slowed artificially by limiting water availability. Winter applications of glyphosate to manage infestations of bitou bush will impact adversely on populations of P. spicata and may also affect the other rare and endangered species whose survival is threatened by this species, even though some natives are unaffected by the herbicide. Protecting native biodiversity from bitou bush will involve sustainable weed management that minimises impacts on non-target native species.