Reproductive traits of riverine shrimps may explain the impact of altered flow conditions

1. The response of a species to environmental disturbance is largely mediated by its life history traits that have evolved within a particular habitat template. Altered flow seasonality, as a direct consequence of river regulation, is a major environmental disturbance and has been implicated in the redistribution of a range of riverine organisms. An understanding of the reasons for species‐specific responses, however, has proved elusive. 2. Here, we investigated the reproduction of three riverine shrimp species (Paratya australiensis, Caridina mccullochi and Macrobrachium australiense) that show contrasting patterns in distribution and abundance in regulated Australian rivers. 3. In all three species, breeding females were largest, and fecundity was greatest early in the breeding season (November–December). Fecundity and egg size subsequently declined, with lower investment (overall and per offspring) perhaps indicating that conditions for larvae were more favourable later in the breeding season (a time normally characterised by low flow, warm water and high productivity). 4. Interspecific differences in absolute values of reproductive traits were, however, striking. Paratya australiensis has typically ‘opportunistic’ traits (small body size, small eggs and high fecundity), whereas M. australiense has more ‘equilibrium’ traits (larger body size, larger eggs and moderate fecundity). Caridina mccullochi is intermediate, having neither high fecundity nor large size, and has limited swimming ability when young. This species is now absent from at least one heavily regulated river in south‐eastern Australia, and we hypothesise that its life history may explain this absence. 5. Studies involving aspects of life history, such as reproductive traits, are likely to improve our understanding of a range of organisms and assist in the management of disturbed or altered environments.     

Reproductive allocation and the fitness consequences of selfing in two sympatric species of Epilobium (Onagraceae) with contrasting mating systems

Selfing has evolved repeatedly in outcrossing taxa, and theory predicts that an increase in the level of self-fertilization should occur in concert with changes in reproductive allocation and the magnitude of inbreeding depression. Here we characterize the mating system of two sympatric congeners, Epilobium ciliatum and E. angustifolium, and compare the taxa for 1) reproductive allocation patterns and 2) the fitness consequences of self-fertilization. For E. ciliatum, autogamy rates were high, pollinator visitation was low, and electrophoresis revealed no genetic variation at 11 putative isozyme loci. For E. angustifolium, autogamy rates were low, pollinator visitation was relatively high, and electrophoresis generated an outcrossing rate estimate of t = 0.64 (SE = 0.08). The pollen/ovule ratio was ten times higher for E. angustifolium than for E. ciliatum, due to a decline in pollen production in the selfing species. The proportion of total flower biomass allocated to female function was significantly greater in E. ciliatum, while that allocated to male function and attractive structures was greater in E. angustifolium. We quantified the fitness consequences of selfing at three life stages: seed number, percent germination, and mature biomass. Relative performance (RP) measures indicated less inbreeding depression for E. ciliatum than for E. angustifolium at all stages; differences in RP between the species were significant for seed number and cumulative total, but not for germination or biomass. RP was correlated among life history stages for only one comparison, suggesting that the genetic basis of inbreeding depression differs among life history stages. Variation among maternal parents for RP was significant at almost all stages in both species, with the exception of seed number in E. ciliatum. The striking variation among maternal parents in E. angustifolium, ranging from strong inbreeding depression to strong outbreeding depression, may reflect both variation in the history of inbreeding and the long-distance migration of individuals from different populations.     

From the backyard to the backcountry: how ecological and biological traits explain the escape of garden plants into Mediterranean old fields

To explain current ornamental plant invasions, or predict future ones, it is necessary to determine which factors increase the probability of an alien species becoming invasive. Here, we focused on the early phases of ornamental plant invasion in order to identify which plant features and cultivation practices may favor the escape of ornamental plants from domestic gardens to abandoned agricultural land sites in the Mediterranean Region. We used an original approach which consisted in visiting 120 private gardens in an urbanizing rural area of the French Mediterranean backcountry, and then visited surrounding old fields to determine which planted species had escaped out of the gardens. We built a database of 407 perennial ornamental alien species (most of which were animal-dispersed), and determined nineteen features that depicted the strength of species’ propagule pressure within gardens, the match between species requirements and local physical environment, and each species’ reproductive characteristics. Using standard and phylogenetic logistic regression, we found that ornamental alien plants were more likely to have escaped if they were planted in gardens’ margins, if they had a preference for dry soil, were tolerant to high-pH or pH-indifferent, and if they showed a capacity for clonal growth. Focusing only on animal-dispersed plants, we found that alien plants were more likely to have escaped if they were abundant in gardens and showed preference for dry soil. This suggests that gardening practices have a primary impact on the probability of a species to escape from cultivation, along with species pre-adaptation to local soil conditions, and capacity of asexual reproduction. Our results may have important implications for the implementation of management practices and awareness campaigns in order to limit ornamental plants to becoming invasive species in Mediterranean landscapes.     

Genetic variation for shell traits in a direct-developing marine snail involved in a putative sympatric ecological speciation process

Populations of the marine gastropod Littorina saxatilis from exposed rocky shores of NW Spain provide one of the few putative cases of sympatric ecological speciation. Two ecotypes with large differences in shell morphology and strong assortative mating are living at different vertical levels of the shore separated by a few meters. It has been hypothesized that shell size is the main determinant for the reproductive isolation observed between the ecotypes, and that several shell shape traits are subject to divergent natural selection and are responsible for the adaptation of each ecotype to its respective habitat. Using embryos extracted from wild females we obtain estimates of genetic variation for shell size and shape and compare them with those from neutral molecular markers. Estimates of heritability are significantly larger for the ecotype found in the upper shore than for that in the lower shore, in concordance with a similar result observed for heterozygosity of neutral markers. The large genetic differentiation between ecotypes for the shell traits, contrasting the smaller close to neutral differentiation between populations of the same ecotype, supports the implication of the traits in adaptation.     

Reproductive processes in sponges: a critical evaluation of current data and views

The nature of a number of fundamental processes occurring during reproduction in sponges still remains in doubt. Among the more significant of these are: the true status of sponges described as dioecious, namely whether some are actually successive hermaphrodites; the origin of oogonia, which have recently been claimed to be derived from choanocytes; the origin and mechanism of formation of large spermatogenic masses; the specific pathway leading to fertilization taken by sperm cells within the sponge tissue of viviparous species; the role played during larval metamorphosis by somatic cells which are incorporated into embryos; the cell lineage of choanocytes which form flagellated chambers during larval metamorphosis; the specific relationship of somatic growth and dormancy to gametogenesis; the role of budding and fragmentation in population maintenance; the role, if any, of gemmules in dispersion. It is considered mandatory that new techniques be developed in order to further elucidate these and other reproductive processes and to gather definitive data concerning them. The employment of only microscopic techniques is ultimately insufficient for investigating the dynamic relationships of reproductive processes.     

Genetic architecture of complex traits and accuracy of genomic prediction: coat colour, milk-fat percentage, and type in Holstein cattle as contrasting model traits

Prediction of genetic merit using dense SNP genotypes can be used for estimation of breeding values for selection of livestock, crops, and forage species; for prediction of disease risk; and for forensics. The accuracy of these genomic predictions depends in part on the genetic architecture of the trait, in particular number of loci affecting the trait and distribution of their effects. Here we investigate the difference among three traits in distribution of effects and the consequences for the accuracy of genomic predictions. Proportion of black coat colour in Holstein cattle was used as one model complex trait. Three loci, KIT, MITF, and a locus on chromosome 8, together explain 24% of the variation of proportion of black. However, a surprisingly large number of loci of small effect are necessary to capture the remaining variation. A second trait, fat concentration in milk, had one locus of large effect and a host of loci with very small effects. Both these distributions of effects were in contrast to that for a third trait, an index of scores for a number of aspects of cow confirmation ("overall type"), which had only loci of small effect. The differences in distribution of effects among the three traits were quantified by estimating the distribution of variance explained by chromosome segments containing 50 SNPs. This approach was taken to account for the imperfect linkage disequilibrium between the SNPs and the QTL affecting the traits. We also show that the accuracy of predicting genetic values is higher for traits with a proportion of large effects (proportion black and fat percentage) than for a trait with no loci of large effect (overall type), provided the method of analysis takes advantage of the distribution of loci effects.     

Differential functional traits underlying the contrasting salt tolerance in Lepidium species

Plant and Soil - To explore the mechanisms responsible for salt tolerance in Brassicaceae species, a multifactorial approach was used to clarify the functional traits underlying the differential...     

Floral traits and pollinator constancy: Foraging by native bees among three sympatric legumes

Abstract The foraging constancy of the solitary bee, Trichocolletes sp., was documented in a semi-arid ecosystem where three morphologically similar legumes co-occur. To quantify the degree of floral similarity among the forage plants, Dillwynia hispida, Dillwynia uncinata and Pultenaea densifolia, discriminant function analysis of petal dimensions and a spectral analysis of corolla colour was undertaken. Petal size varied moderately among species resulting in 2–14% of specimens being misclassified, usually as D. uncinata. Subtle variation in corolla colour in the ultraviolet wavelengths contributed to the distinctiveness of each species. All three species exhibit an UV-absorbing region at the base of the standard petal which contrasts sharply with the rest of the UV-rerlecting petal. Between 450 nm and 470 nm, per cent reflectance drops for D. hispida and P. densifolia, but remains steady for D. uncinata. Above 480 nm, parts of the standard petal in all species reflect similar amounts of light with little variation exhibited among species. Nectar was only offered by D. hispida and D. uncinata, whereas P. densifolia produced an excess of pollen which may serve as a reward. Despite the subtle differences in floral morphology and rewards among these sympatric legumes, Trichocolletes bees only remained faithful to a given species in 43% of 183 interplant flights. Inconstant foraging by Trichocolletes sp. increases the pool of resources because rewards in all three legume species can be obtained in exactly the same manner.     

Natural radioactivity can explain clinal variation in the expression of melanin-based traits

A recent study shows that the expression of pheomelanin-based coloration in barn owls follows a continuous gradient across Europe as a result of local adaptation. The selective pressures that promote local adaptation remain, however, unknown. Here we hypothesize and test that natural radioactivity levels follow a similar spatial gradient to that of pheomelanin-based color in Europe and thus represents a potential selective pressure. The rationale is that the production of pheomelanin consumes glutathione (GSH), a key intracellular antioxidant, and that GSH is particularly susceptible to ionizing radiation, which depletes antioxidants. As predicted, the intensity of pheomelanin-based coloration in 18 populations of barn owls was negatively associated with terrestrial γ-dose rates across Europe. Therefore, we propose that natural selection acts against barn owls that present the molecular basis to produce large amounts of pheomelanin in those populations that are exposed to high levels of natural radioactivity, as in these populations individuals would require higher antioxidant resources to combat oxidative stress. This is the first time that natural radioactivity levels are related to the expression of a phenotypic trait.     

Fish eggs and pentacrinoids in Weddell Sea hexactinellids: further examples for the structuring role of sponges in Antarctic benthic ecosystems

 During the CS-EASIZ expedition (ANT XII/3) to the eastern Weddell Sea shelf with RF ‘Polarstern’ in January–March 1996, several hundred hexactinellids from trawl catches were inspected for associated fauna. At one station, fish egg masses were found in the suboscular cavities of 18 specimens of hexactinellid sponges belonging to four different species of the genus Rossella. Egg numbers in intact hexactinellids ranged from about 800 to more than 8000. At two stations, pentacrinoids, the sessile stage of comatulid crinoid development were found attached to the inner dermal membrane of hexactinellids. This is the first time pentacrinoids have been documented from the high Antarctic. The pentacrinoids mostly formed small groups, but single individuals were found as well. Neither fish eggs nor pentacrinoids were observed in or on other structures or animals; these findings stress the overall importance of sponges, especially hexactinellids, as substrates for developmental stages of other members of the ecosystem. Received: 25 May 1996/Accepted: 22 July 1996     

Thermal reaction norms in two Coenagrion damselfly species: contrasting embryonic and larval life-history traits

1. We studied the temperature‐dependence of important life‐history traits both at the embryonic (egg hatching success, embryonic development time and hatchling size) and the larval stage (larval growth rate, larval survival and larval size after 100 days) using full‐sib families of two congeneric damselflies, Coenagrion hastulatum and Coenagrion puella, that differ in latitudinal distribution. Larvae were reared in the laboratory from the egg stage at four temperatures (12, 17, 22 and 27 °C). 2. The observed patterns of thermal plasticity in embryonic traits showed that the northern species was more successful than the southern species at lower temperatures, in line with the pattern of temperature adaptation in thermal reaction norms. 3. At the larval stage, we found no consistent pattern of latitudinal compensation. The thermal family reaction norms indicate, however, the potential for latitudinal compensation to evolve. We observed an ontogenetic shift in thermal optima for larval growth rate, with a higher optimal temperature for growth rate during the first 2 weeks of the larval stage. 4. This is the first indication of the existence of latitudinal compensation at the interspecific level in an invertebrate; it is stage‐specific, being present only in the embryonic stage. We argue that compensation in the embryonic stage may be much more likely than in the larvae and stress the importance of including more then one life‐history stage when drawing conclusions about the adaptiveness of patterns in thermal reaction norms.     

Floral traits and isolation of three sympatric Aquilegia species in the Qinling Mountains, China

Floral isolation has been considered to be an important reproductive mechanism governing the species diversification in many genera. In a classic example Aquilegia, sympatric species from North America with diverse floral traits are generally associated with specialized pollinators that prohibit interspecific hybridization. It remains unclear whether species diversification in the genus from Eurasia is also maintained by floral isolation. We investigated floral phenology, floral characteristics and pollinators in three sympatric Aquilegia species (A. ecalcarata, A. incurvata and A. yabeana) in the Qinling Mountains, Shanxi Province, China from 2001 to 2005. The spurless A. ecalcarata flowers earlier than the other two species with nectar spurs but their floral phenology overlaps. Major pollinators of A. ecalcarata are syrphid flies while bumblebees are major for A. incurvata and A. yabeana. Therefore our observations confirm that mechanical isolation through differential pollinators could contribute reproductive isolation between spurless and spurred species, as demonstrated by studies from North America. Whether floral isolation plays a major role in the reproductive isolation between two spurred species (A. incurvata and A. yabeana), however, remains to be seen. Further studies are required to quantify the potential role of geographical isolation because they occupy different habitats.     

Heteroblastic development and the optimal partitioning of traits among contrasting environments in Acacia implexa

Background and Aims: Optimal partitioning theory (OPT) predicts plants will allocatebiomass to organs where resources are limiting. Studies of OPTfocus on root, stem and leaf mass ratios where roots and stemsare often further sub-divided into organs such as fine roots/taproots or branches/main stem. Leaves, however, are rarely sub-dividedinto different organs. Heteroblastic species develop juvenileand adult foliage and provide an opportunity of sub-dividingleaf mass ratio into distinct organs. Acacia implexa (Mimosaceae)is a heteroblastic species that develops compound (juvenile),transitional and phyllode (adult) leaves that differ dramaticallyin form and function. The aims of the present study were togrow A. implexa to examine patterns of plastic development ofwhole-plant and leaf traits under the OPT framework. Methods: Plants were grown in a glasshouse under contrasting nutrient,light and water environments in a full factorial design. Allocationto whole-plant and leaf-level traits was measured and analysedwith multivariate statistics. Key Results: Whole-plant traits strongly followed patterns predicted by OPT.Leaf-level traits showed a more complex pattern in responseto experimental treatments. Compound leaves on low nutrientplants had significantly lower specific leaf area (SLA) andwere retained for longer as quantified by a significantly greatercompound leaf mass ratio after 120 d. There was no significantdifference in SLA of compound leaves in the light treatment,yet transitional SLA was significantly higher under the lowlight treatment. The timing of heteroblastic shift from compoundto transitional leaves was significantly delayed only in thelow light treatment. Therefore, plants in the light treatmentresponded at the whole-plant level by adjusting allocation toproductive compound leaves and at the leaf-level by adjustingSLA. There were no significant SLA differences in the watertreatment despite strong trends at the whole-plant level. Conclusion: Explicitly sub-dividing leaves into different types providedgreater insights into OPT.     

Phylogenetic diversity and ecological features in the Egyptian flora

Until fairly recently, regional-scale ecological and evolutionarypatterns have tended to be ignored as conservation efforts have been concernedwith species and their habitats. Here we compare frequencies in the Egyptianflora of particular rank sizes (order, family and genus) with patterns ofspecies abundance (classified as very rare, rare, common, or very common) and anarray of life-history attributes. The angiosperm flora of Egypt is representedby 2446 taxa (2088 species), including taxa in 10 subclasses, 51 orders, 120families, and 742 genera. A high degree of monotypism was observed: four ordersare monotypic (each existing as single species), and have very rare overallabundances; 30 families are monotypic (17 of which are very rare or rare); and 354genera are monotypic (over 70% of which are very rare or rare). Fourteenfamilies (in particular the Resedaceae and Zygophyllaceae) have at leastone-fifth of their global species represented in the Egyptian flora. Introducedspecies in general, and tree, aquatic herb and liana life forms all are especially well represented among monotypic genera. Native taxa are highlyrepresented among rare and very rare abundance classes, while introduced taxadid not differ significantly in their abundance patterns, compared to overallflora values. Few large genera (>20 spp.) occur in the flora, with mostspecies concentrated in genera containing 8–19 species per genus.Similarly, few families were highly speciose. Annual and herbaceous species weresignificantly over-represented, mainly among large, speciose genera andfamilies. However, perennials, trees, shrubs, aquatic herbs, lianas and parasiticspecies were found mainly in families and genera having very few taxa.Life-history attributes may have important implications to speciation rates.Taxonomically based results, involving abundances and life-history attributes,are discussed in the context of biodiversity and conservation.