Spatial genetic structure of two sympatric neotropical palms with contrasting life histories

The spatial genetic structure within sympatric populations of two neotropical dioecious palm species with contrasting life histories was characterized to evaluate the influence of life history traits on the extent of genetic isolation by distance. Chamaedorea tepejilote is a common wind-pollinated arboreal understory palm. Chamaedorea elatior is an uncommon climbing subcanopy palm with entomophilous pollination syndrome. A total of 59 allozyme alleles for C. tepejilote and 53 alleles for C. elatior was analyzed using both unweighted (Iu) and weighted (Iw) Moran's I spatial autocorrelation statistics. The spatial genetic structure detected within these populations is consistent with those reported for highly dispersed plants. A significance test for differences between mean Moran's I-coefficients revealed less spatial genetic structure within the C. tepejilote population than that in the C. elatior population. Adjacent individuals of C. elatior exhibited significant spatial genetic autocorrelation (Iu=0.039, Iw=0.034), indicating a Wright's neighborhood size of about 100 individuals. For C. tepejilote, nonrandom genetic distribution among nearest neighbors was detected, even from small spatial autocorrelation values (Iu=0.008, Iw=0.009), consistent with a neighborhood size of about 300 individuals. For both species, seed dispersal, mortality among life cycle stages, overlapping generations, and contrasting traits of mating and reproduction influence the standing spatial genetic structure within populations.     

Management units of brown trout from Galicia (NW: Spain) based on spatial genetic structure analysis

Population genetic structure approaches offer the possibility of defining management units in conservation activities of species. The genetic structure of the brown trout Salmo trutta in Galicia (NW Spain) was investigated by using microsatellites. We determined genetic variation across 10 microsatellite loci of 901 individuals from 30 geographical populations representing 18 river basins. The analysis of the spatial distribution of the genetic variation by using different methods clearly revealed strong genetic differentiation among two groups of populations living in the studied area. This result is concordant with previous work using allozymes and mtDNA markers, and confirms a secondary contact among two highly differentiated evolutionary lineages in Miño Basin. Although both lineages might be locally adapted, results suggest that they hybridize at the middle course of the river. The brown trout from the Upper Miño Basin belongs to the previously described Duero lineage, an Iberian endemism threatened by introgression with other Atlantic forms. The results support the recognition of the Upper Miño Basin as a particular biotic region in Galicia. This study illustrates how a multidisciplinary approach in spatial genetic analysis contributes to the delineation of conservation units as conspecific metapopulations.     

High levels of genetic variability and inbreeding in two Neotropical dioecious palms with contrasting life histories

We characterized the population genetics of two Neotropical dioecious palm species of Chamaedorea with contrasting life strategies from the region that is both the northernmost extent and most species rich of the genus. Chamaedorea tepejilote is a common, wind-pollinated arboreal understory palm. Although most adult plants reproduce each year, only a few individuals produce the majority of flowers and seeds. Chamaedorea elatior, conversely, is an uncommon climbing subcanopy palm with entomophilous flowers (insect-pollinated characteristics). Most of the mature palms do not reproduce in consecutive years and fruiting is episodic. Isozymes with a total of 107 alleles for 27 loci of 17 enzymes from six populations were assessed. For both species, co-occurrence of high levels of genetic variation and homozygosity was observed (C. tepejilote: He: 0.385-0.442, f: 0.431-0.486; C. elatior: He: 0.278-0.342, f: 0.466-0.535). Genetic differentiation of C. elatior was much lower (theta=0.0315) than that for C. tepejilote (theta=0.152). The contrast in differentiation may be influenced by differences in the spatial scale of the genetic neighborhoods of the two species. The simultaneous maintenance of inbreeding and of a large number of alleles within the populations is attributable to the low and variable number of mating pairs. Demographic studies indicate that this pattern could be explained by low reproductive frequency among individuals and over years in C. elatior and by reproductive dominance in C. tepejilote.     

Fine-spotted brown trout: genetic aspects and the need for conservation

In Lake Svartavasstjønn on the Hardangervidda plateau, a fine-spotted variant of brown trout has been found. The spotted variability shows a classical Mendelian mode of inheritance. In this population genetic variability was found in LDH-5 *, MDH-3 * and MDH-3 *. The fast allele at LDH-5 * had a frequency of 0,913. This is remarkable, as this allele has been found in frequencies above 0.4 in only five out of 50 investigated populations in Norway. The genetic characteristics of brown trout from Lake Svartavasstjønn were compared with 11 other populations sampled from a broad geographical area of Norway. Among these was Lake Setningen, where fine-spotted individuals occur at low frequency. Using a cluster analysis based on eight loci found to be polymorphic in brown trout, we found no indication of a close relationship between the fine-spotted brown trout from Lake Svartavasstjønn and the population in Lake Setningen. During a field survey in 1990 we found that the reproduction of fine-spotted trout in Lake Svartavasstjønn had terminated. The fine-spotted trout represents a valuable but threatened genetic resource, and attempts are carried out to conserve it.     

Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species'' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed.     

Brown hares on the edge: Genetic population structure of the Danish brown hare

Denmark lies on the edge of the distributional range of the brown hareLepus europaeus Pallas, 1778, where population differentiation is most likely to occur. A total of 369 brown hares from eight geographically distinct Danish European brown hare populations were used to study the genetic population structure. In all, 480bp of the mitochondrial D-loop were sequenced in both directions. Observed genetic diversity (π) was relatively low (π=0.41%) while haplotype diversity (h=0.808) and the number of unique haplotypes (19) were similar to levels found in other European brown hare populations. The observed population structure was pronounced (pairwise conventionalF _ST and ϕ _st ranged between 6.9–57% and 5–69.8%, respectively). There was no correlation between the geographic and the genetic distance. Population structure was influenced by genetic drift, anthropogenic effects (eg translocation and escapes from hare-farms) and by post-glacial recolonization from southern refuges or refuges north east of the Black Sea. Analysis of historical population expansion/fluctuation events indicated that the populations have experienced different demographic events in the recent past. Relatively high sequence divergence between some populations might be explained by multiple recolonization events after the last Pleistocene glaciations or by stocking effects. Colonization from southern refuges was supported by the observation that haplotype 2 in the Danish brown hare was identical to the central European ancestral haplotype c07.     

Experimental investigation of the success of stocked, domestic brown trout and their effects on wild brown trout in upland and lowland rivers

The stocking of adult, domestic brown trout (DBT)( Salmo trutta L.) to supplement angling catches is a common practice. There is increasing concern, however, over the effects of such stockings on indigenous wild brown trout (WBT) populations. This paper describes an experimental field trial to explore the success of stocked DBT and their effects on WBT growth and abundance. DBT adults were stocked into upland rain‐fed and lowland spring‐fed streams. Three stocking treatments and a control were replicated six times for each of the two stream categories. In spring, baseline adult (defined as >200 mm LF) WBT densities were increased by 25, 50 and 100% using equal quantities of two different strains of DBT from two large suppliers. All DBT were measured, weighed and tagged before being stocked. The stocking procedure approximated to current stocking practice. A total of 48 500 m experimental sites were used. The abundance of WBT was estimated at each survey site in the summer prior to stocking via electrofishing and the depletion method. All WBT captured were measured and weighed. In addition, all WBT >100 mm were tagged. Habitat was assessed using the HABSCORE model. Post‐treatment monitoring was undertaken in the summer following stocking. Data will be presented regarding the effects of the stocking treatments on the growth and abundance of WBT as well as the strain‐dependent performance of DBT across all sites and on a river type‐specific basis. The suitability of using HABSCORE to formulate appropriate stocking densities will be discussed.     

The distinction between brown trout and sea trout by the strontium content of their scales

A method is described for distinguishing the scales of sea trout from brown trout by their strontium content. Scales of brown trout contain less than 200 μgSr/g and those of sea trout more than 300 μgSr/g.     

Life at the edge: Roe deer occurrence at the opposite ends of their geographical distribution,Norway and Portugal

In the face of climate change and habitat fragmentation there is an increasingly urgent need to learn more about factors that influence species distribution patterns and levels of environmental tolerance. Particular insights can be obtained by looking at the edges of a species range, especially from species with wide distributions. The European roe deer was chosen as a model species due to its widespread distribution. By using pellet group counts, we studied summer and winter habitat use of this herbivore at two of the extreme edges of its distribution – southwest of Portugal, and northeast of Norway – in relation to a range of fine-scale environmental factors including forest structure, vegetation characteristics and human disturbance. Our first prediction that roe deer would respond differently to human activity in both counties was supported. While in Norway roe deer are always close to houses, in Portugal they are either far (in summer) or indifferent (winter). However, everywhere and in every season, roe deer are far from roads. Our second prediction that roe deer better tolerate anthropogenic disturbances in the area where the importance of limiting factors is higher (Norway) was validated. However, our third prediction that anthropogenic disturbance would be less tolerated by roe deer outside the limiting seasons in each country was not supported. Our results suggest that roe deer perceive human activities differently in the two countries and that roe deer better tolerate anthropogenic disturbances in Norway.     

Abundance and spatial distribution of aphids and scales select for different life histories in their ladybird beetle predators

Abstract:  Life history parameters tend to differ between aphidophagous and coccidophagous ladybird beetles. It seems that the nature of prey, in particular the abundance, number and size of the colonies and their spatial distribution, may have been selected for the evolution of the life histories in these two groups of coccinellids, leading the aphidophagous ladybird beetles to develop at a fast pace and the coccidophagous beetles at a slower pace. To study the abundance, number and size of the colonies and the spatial distribution of aphid and coccid species, 100 sampling plots regularly spaced along four parallel transects were surveyed in the summer of 2004. At each sampling plot, species abundance, and the number and size of colonies of aphid and coccid species were recorded. Iwao's patchiness regression was used to assess the spatial distribution of aphids and coccids. From this study, it was found that coccids are much rarer than aphids but formed more colonies. Whereas aphids display a stonger tendency to crowding, aphid colonies are randomly distributed in space while coccid groups are aggregated. So, it seems that the abundance and spatial distribution of prey distribution may be factors selecting for the evolution of different life histories among aphidophagous and coccidophagous ladybird beetles.     

Life at the edge: the nuclear envelope and human disease

A group of human diseases, known as 'laminopathies', are associated with defects in proteins of the nuclear envelope. Most laminopathy mutations have been mapped to the A-type lamin gene, which is expressed in most adult cell types. So, why should different mutations in a near-ubiquitously expressed gene be associated with various discrete tissue-restricted diseases? Attempts to resolve this paradox are uncovering new molecular interactions #151; both inside the nucleus and at its periphery -- which indicate that the nuclear envelope has functions that go beyond mere housekeeping.     

Assumed and inferred spatial structure of populations: the Scandinavian brown bears revisited

We reanalysed the spatial structure of the Scandinavian brown bear (Ursus arctos) population based on multilocus genotypes. We used data from a former study that had presumed a priori a specific population subdivision based on four subpopulations. Using two independent methods (neighbour-joining trees and Bayesian assignment tests), we analysed the data without any prior presumption about the spatial structure. A subdivision of the population into three subpopulations emerged from our study. The genetic pattern of these subpopulations matched the three geographical clusters of individuals present in the population. We recommend considering the Scandinavian brown bear population as consisting of three (instead of four) subpopulations. Our results underline the importance of determining genetic structure from the data, without presupposing a structure, even when there seems to be good reason to do so.     

Observations on the structure of brown trout, Salmo trutta Linnaeus, redds

This paper describes the gravel type and structure of brown trout spawning gravels in Teesdale, the flow characteristics of the spawning sites and the size of redds. Factors influencing redd size are investigated and it is concluded that female size is a major factor. Relationships are established between various redd characteristics and the fork length of female fish. The findings are discussed in relation to the existing literature concerning salmonid spawning sites.     

Life at the dry edge: Microorganisms of the Atacama Desert

The Atacama Desert, located in northern Chile, is the driest and oldest Desert on Earth. Research aimed at the understanding of this unique habitat and its diverse microbial ecosystems begun only a few decades ago, mainly driven by NASA's astrobiology program. A milestone in these efforts was a paper published in 2003, when the Atacama was shown to be a proper model of Mars. From then on, studies have been focused to examine every possible niche suitable for microbial life in this extreme environment. Habitats as different as the underside of quartz rocks, fumaroles at the Andes Mountains, the inside of halite evaporates and caves of the Coastal Range, among others, have shown that life has found ingenious ways to adapt to extreme conditions such as low water availability, high salt concentration and intense UV radiation.     

Life histories and habitat selection in Daphnia: divergent life histories of D. magna clones differing in phototactic behaviour

To test the hypothesis of co-adaptation of life histories and daytime vertical distribution (vertical migration behaviour) in Daphnia, life history characteristics were analysed for two positively, three negatively, and four intermediately phototactic Daphnia magna clones. Clones with different phototactic behaviour were found to have divergent life history strategies, with positively phototactic clones being good exploiters under the non-limiting conditions provided in the laboratory, i.e. low density (1 ind./1), high food concentration (6,5–7 10⁵ Scenedesmus cells/ml, restored daily) and high temperature (20° C). They realized a high intrinsic rate of increase at a small adult body size through rapid development, at a cost of producing small neonates. Negatively and intermediately phototactic clones had larger adult body sizes, and produced larger neonates that were more starvation-resistant than those of positively phototactic clones. Selection for high intrinsic rate of increase in intermediately phototactic clones was mediated through the production of large clutches.