Intraspecific cleaning behaviour in Cyprinus carpio in aquaria

Intraspecific cleaning behaviour of diseased juvenile Cyprinus carpio L, in experimental tanks in Wuxi, China has been observed and is described.     

Increasing temperature weakens the positive effect of genetic diversity on population growth

Genetic diversity and temperature increases associated with global climate change are known to independently influence population growth and extinction risk. Whether increasing temperature may influence the effect of genetic diversity on population growth, however, is not known. We address this issue in the model protist system Tetrahymena thermophila. We test the hypothesis that at temperatures closer to the species’ thermal optimum (i.e., the temperature at which population growth is maximal, or T _opt), genetic diversity should have a weaker effect on population growth compared to temperatures away from the thermal optimum. To do so, we grew populations of T. thermophila with varying levels of genetic diversity at increasingly warmer temperatures and quantified their intrinsic population growth rate, r. We found that genetic diversity increases population growth at cooler temperatures, but that as temperature increases, this effect weakens. We also show that a combination of changes in the amount of expressed genetic diversity (G) in r, plastic changes in population growth across temperatures (E), and strong G × E interactions underlie this temperature effect. Our results uncover important but largely overlooked temperature effects that have implications for the management of small populations with depauperate genetic stocks in an increasingly warming world.     

Analyses of Genetic Diversities in Chinese Fresh-water Fishes

1ChromosomalkaryotypesofChinesefresh-waterfishesThevastresourcesofnaturalwaterbodiesinChinaharboravarietyoffishesthathaveevolvedthroughalonghistoryofdiversification.BaseontheestimationmadebyLi(1981),therearemorethan800speciesandsubspeciesoffresh-waterfishesinChina.Mostofthembelongto32familiesin13forms.Theremaining(about60)speciesaremigratoryfishes,be-longingto21familiesin9forms.Approximatelyhalfofallthefishesarethecyprinids--thelargestdistributioncomparingtoothergeographicregionsintheworld.…     

Heterochronic differences in fin development between latitudinal populations of the medaka Oryzias latipes (Actinopterygii: Adrianichthyidae)

Heterochrony is believed to have played important roles in macroevolutionary morphological changes. However, few studies have focused on intraspecific heterochrony, although interspecific differences ultimately originated from variation within ancestral species. We have demonstrated heterochrony in fin development between two latitudinal populations of the medaka, Oryzias latipes . Comparisons of fin length (anal and dorsal) among wild individuals revealed that fins are shorter with respect to body length in the northern population, indicating that they are 'paedomorphic' compared with the southern population. Observations of fin ray formation and subsequent fin growth in the laboratory revealed that the timing of pterygiophore development occurs later, and that fins start to elongate later with respect to body length in the northern fish, indicating that fin growth is 'post-displaced' compared with the southern population. In addition, the rate of fin growth with respect to body length was lower in the northern males, indicating 'neoteny'. Given that all Oryzias except O. latipes are distributed in the tropics, it is likely that higher-latitude fish have evolved post-displacement and neoteny during northern extension of their geographic range. The delayed development in higher-latitude fish is probably a trade-off for faster body growth, which has evolved as an adaptation to seasonally time-constrained environments.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 571–580.     

Determination of ploidy and nuclear DNA content in populations of Atriplex halimus (Chenopodiaceae)

Nuclear DNA contents were determined by flow cytometry for 20 populations of the perennial C₄ shrub Atriplex halimus L. (Chenopodiaceae) originating from the Mediterranean basin and Fuerteventura (Canary Islands). Two populations were also analysed for chromosome number: one (from Ibiza, Spain), with a 2C nuclear DNA content of 2.40 pg, was shown to be diploid (2 n  = 2 x  = 18), whilst the other (from Sicily, Italy), with 5.11 pg, was tetraploid (2 n  = 2 x  = 36). With respect to nuclear DNA content, two groups of populations were detected, diploids with 2.40–2.44 pg and tetraploids with 4.77–5.13 pg. The diploid populations were mainly from the western Mediterranean (Spain and France) and Fuerteventura, whereas tetraploids were generally, but not exclusively, from more arid areas in North Africa and the eastern Mediterranean. In general, the diploid and tetraploid populations corresponded to the subspecies halimus and schweinfurthii , respectively. For certain populations having morphologies intermediate between those considered typical of these two subspecies, nuclear DNA contents showed them to be tetraploid. There was significant variation in nuclear DNA content among the tetraploid populations, with greater values in the more easterly populations.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 147 , 441−448.     

Morphological variation in the palaeonemertean Tubulanus annulatus (Montagu, 1804)

Previous studies on the palaeonemertean Tubulanus annulatus have hinted on possible geographic variation, or even a species complex. This study describes the variation in morphology, focusing on the characters that have been supposed to vary geographically. Specimens from the Swedish west coast (Tjärnö and Kristineberg), Scottish west coast (Millport), and the Mediterranean (Naples and Split) were included in the study. It is concluded that the pattern of variation in the studied characters do not correspond to geography and most of the character states previously thought to vary geographically are in fact found within one and the same population.     

Effects of larval movement behavior and density on emergence success and adult body size in a commensal midge

Changes in larval density and movement behavior of a commensal midge, Nanocladius (Plecopteracoluthus) sp. #4, were monitored for 26 weeks in recirculating laboratory streams. Adults were captured at emergence, sexed, and weighed to assess the effect of larval density and movement behavior on emergence success and adult size. The density of midges on hosts declined with time and coincided with a springtime increase in larval movement frequency. Midges residing on hosts with high spring densities emerged significantly less than midges on hosts with low densities. Resident midge density on hosts did not influence the likelihood of successful colonization by commensals and colonizers showed no preference for initial attachment site on hosts. However, colonizing midges emerged significantly less than resident midges. Similarly, successful emergers changed tube positions significantly less often as larvae relative to non-emergers. There was no difference in adult body weight of resident midges and colonists/movers, but adult males which emerged from commensal-laden (high density) hosts were significantly smaller than males from low density hosts. These data indicate larval density and movement behavior may have strong fitness consequences for commensal midges.     

The Content of Light-Harvesting Complexes in Different Maize (Ze mays L.) Genotypes

Genetic analysis of the content of light-harvesting complexes of thylakoid membranes was accomplished for the first time during the study of intraspecific variation in photosynthetic characteristics. The existence of genetically determined differences between genotypes together with positive heterosis in F₁ generation was demonstrated. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cytology of lepidoptera. III. Giant cysts: A morphological trait of apyrene spermatogenesis in an Ephestia kuehniella strain

A comparative investigation of testicular eupyrene cysts (in larvae) and apyrene cysts (in pupae) of Ephestia kuehniella laboratory strains was conducted using light and electron microscopy. Eupyrene cysts in the first meiotic division contained 64 spermatocytes, which showed only moderate asynchrony. In one of the strains, a wild-type strain, L, normal-sized cysts occurred together with abnormally large cysts. These are called giant cysts in this article. One of the premeiotic cysts, early giant cysts, studied in detail, contained approximately a fourfold number of cells compared with the number in a eupyrene cyst of the same stage. In cysts harboring spermatocytes and spermatids, late giant cysts, cell differentiation was highly asynchronous. Failure in one of two control mechanisms in early cyst development may have caused the appearance of the cysts. Control of cell division might have been sloppy in apyrene spermatogonia. Hence, the spermatogonia within the cyst could have passed through additional division cycles. Alternatively, the giant cysts may have originated from more than one predefinitive gonial cell enclosed in a common envelope of sheath cells. As a third possibility, giant cysts could have arisen by fusion of normal cysts at a later stage. In either case, this is evidence that separation of eupyrene and apyrene pathways is earlier than was previously expected. In two other Ephestia strains, apyrene sperm development proceeded without formation of giant cysts. One was a mutant strain, a, and the other one was a recently established wild-type strain, Sbr. Apyrene sperm development is considered an example of degenerate evolution in which enhanced variability between species and even between populations of one species is a common phenomenon.     

Genetic Identity of Populus tremuloides Litter Influences Decomposition and Nutrient Release in a Mixed Forest Stand

Recent research has shown that genetic variation can directly impact community and ecosystem level processes. Populus tremuloides (trembling aspen) is an extremely widespread and genetically diverse tree species important to many North American forest ecosystems. Using leaf litter from five genotypes grown in a common garden under two nutrient treatments, we tracked litter decomposition in a natural aspen stand for 1 year. Here we show that aspen leaf litter decomposes and releases carbon, nitrogen, and sulfur in relation to its genetic identity. In a secondary experiment, we show that the genetic diversity of aspen litter mixtures can influence decomposition, however weakly so. Overall, nutrient treatments influenced leaf litter decomposition the most, followed by genetic identity, and then by genetic diversity (if at all in some cases). In this widespread, genetically diverse, and dominant species, genetic variation within a single species is important to ecosystem functioning. The relatively weak effect of genetic diversity on the processes measured here does not preclude its importance to ecosystem functioning, but does suggest that genetic identity and composition are more important than genetic diversity per se.     

Investigating South American biogeographic history using patterns of skull shape variation on Cerdocyon thous (Mammalia: Canidae)

Patterns of geographic variation of the canid Cerdocyon thous have historically been obscured by its remarkable intraspecific morphological variability. The observed distribution is highly associated with phytophysiognomy, a feature considered highly dynamic along geological time. In the present study, we tested whether vegetation distribution during the Holocene Glacial Maximum of South America (HGM) explains the patterns of morphological variation within Cerdocyon thous . The species was divided in groups according to paleohabitats that could support their presence during the HGM, and then tested for differences in skull morphometrics. The results obtained demonstrate that the climatic changes during the HGM influenced the population structure of this species, resulting in the establishment of geographical groups with different degrees of morphological cohesion. Higher morphological cohesion found in the Northern group might be explained by the marked discontinuity between its geographical range and the rest of the species'distribution. The Eastern and Southern morphological divergence is less striking and, although this could be related to past vegetation distribution, the disappearance of those barriers leads to a population structure that could be slowly breaking down.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 77–84.     

Mosaic pattern of genital divergence in three populations of Schistocerca lineata Scudder, 1899 (Orthoptera: Acrididae: Cyrtacanthacridinae)

Sexual selection theory predicts that genital structures in isolated populations are likely to diverge, but male genitalia are often species-specific, which led to the idea that male genitalia are relatively invariable within species. Previous allometric studies collectively suggested that male genitalia are intraspecifically invariable in size compared with external body parts. We investigated whether male genitalia are invariable in shape in three populations of a grasshopper Schistocerca lineata Scudder, 1899, using two independent methods of geometric morphometric analyses. Specifically, we focused on the idea that male genitalia are complex structures consisting of many functionally different components, and studied how these individual parts diverge among three populations. Individual components of male genitalia show different population-level divergence, resulting in the mosaic pattern of genital divergence. Individual components diverge independently from each other. Body size is positively correlated with genitalia size, but is significantly correlated with the shape of only one of the three genital structures we measured. Thus, different components of male genitalia may be influenced by different evolutionary processes. This study is the first to show that components of complex genitalia evolve separately within a species.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 289–301.     

Priority effects in a planktonic bloom-forming marine diatom

Priority effects occur when a species or genotype with earlier arrival has an advantage such that its relative abundance in the community or population is increased compared with later-arriving species. Few studies have dealt with this concept in the context of within-species competition. Skeletonema marinoi is a marine diatom that shows a high degree of genetic differentiation between populations over small geographical distances. To test whether historical events such as priority effects may have been important in inducing these patterns of population differentiation, we performed microcosm experiments with successive inoculation of different S. marinoi strains. Our results show that even in the absence of a numerical advantage, significant priority effects were evident. We propose that priority effects may be an important mechanism in initiating population genetic differentiation.     

Habitat‐driven life history variation in an amphibian metapopulation

Life‐history theory states that, during the lifetime of an individual, resources are allocated to either somatic maintenance or reproduction. Resource allocation tradeoffs determine the evolution and ecology of life‐history strategies and determine an organisms’ position along the fast–slow continuum. Theory predicts that environmental stochasticity is an important driver of resource allocation and therefore life‐history evolution. Highly stochastic environments are expected to increase uncertainty in reproductive success and select for iteroparity and a slowing down of the life history. To date, most empirical studies have used comparisons among species to examine these theoretical predictions. By contrast, few have investigated how environmental stochasticity affects life‐history strategies at the intraspecific level. In this study, we examined how variation in breeding site stochasticity (among‐year variability in pond volume and hydroperiod) promotes the co‐occurrence of different life‐history strategies in a spatially structured population, and determines life‐history position along the fast–slow continuum in the yellow‐bellied toad Bombina variegata. We collected mark–recapture data from a metapopulation and used multievent capture–recapture models to estimate survival, recruitment and breeding probabilities. We found higher survival and longer lifespans in populations inhabiting variable sites compared to those breeding in stable ones. In addition, probabilities of recruitment and skipping a breeding event were higher in variable sites. The temporal variance of survival and recruitment probabilities, as well as the probability to skip breeding, was higher in variable sites. Taken together, these findings indicate that populations breeding in variable sites experienced a slowing down of the life‐history. Our study thus revealed similarities in the macroevolutionary and microevolutionary processes shaping life‐history evolution.     

Isolation of polymorphic microsatellite loci in the Hawaii amakihi (Hemignathus virens) and their use in other honeycreeper species

We report the isolation and characterization of five polymorphic microsatellite loci in the Hawaii amakihi, Hemignathus virens, one of the most common native Hawaiian forest birds. These loci exhibit high levels of allelic diversity and heterozygosity in the three honeycreeper species we screened, and promise to be useful in our investigation of differences between honeycreeper populations at different elevations.     

Variations in cruropedal musculature

The comparative anatomy of primate musculature has been established frequently from single specimens or small samples which are assumed to be typical for their species. However, a series of dissections of platyrrhine monkeys reported here reveals considerable variation within species and genera. Selected muscles of the leg and foot were examined and compared for discrete variations in attachments. The results were supplemented by observations in the anatomical literature for these and other primates. The range of variation reported across the order also presents itself as widespread polymorphism within most taxonomic groups, down to the species level. Since correlations with phylogeny and positional behavior are expressed only weakly, adaptationist explanations can account for only a part of the variation. Functional redundancy among the muscles supports the conclusion that the behavioral significance of the variations is slight. It is apparent that both genetic and nongenetic factors influence muscle form, and it is likely that observed polymorphisms have been characteristic of populations throughout primate evolution. Therefore, traits involving muscular form, especially as observed on small samples, within species, should be used cautiously in phyletic and adaptationist analyses.     

Parent–offspring similarity in the timing of developmental events: an origin of heterochrony?

Understanding the link between ontogeny (development) and phylogeny (evolution) remains a key aim of biology. Heterochrony, the altered timing of developmental events between ancestors and descendants, could be such a link although the processes responsible for producing heterochrony, widely viewed as an interspecific phenomenon, are still unclear. However, intraspecific variation in developmental event timing, if heritable, could provide the raw material from which heterochronies originate. To date, however, heritable developmental event timing has not been demonstrated, although recent work did suggest a genetic basis for intraspecific differences in event timing in the embryonic development of the pond snail, Radix balthica. Consequently, here we used high-resolution (temporal and spatial) imaging of the entire embryonic development of R. balthica to perform a parent–offspring comparison of the timing of twelve, physiological and morphological developmental events. Between-parent differences in the timing of all events were good predictors of such timing differences between their offspring, and heritability was demonstrated for two of these events (foot attachment and crawling). Such heritable intraspecific variation in developmental event timing could be the raw material for speciation events, providing a fundamental link between ontogeny and phylogeny, via heterochrony.     

Factors influencing intraspecific variation and polymorphism in marine podocopid Ostracoda,with particular reference to Tertiary species from southeastern Australia

Work on intraspecific variation in ornate ostracods over the last 30 years is reviewed. Polymorphism (discontinuous variation) due to environmental and genetic factors (and combinations thereof) is discussed. Specimens of the ornate marine genera Cletocythereis, Hermanites, Notocarinovalva, Neobuntonia, Chapmanella, Actinocythereis, Spinobradleya and Loxoconcha, from Tertiary deposits of southeastern Australia, are examined for examples of significant intraspecific morphological variation. Variations in the degree of spinosity, the nature of spines, the degree and type of aggradation (celation), the occurrence of microreticulation, the shape of fossae, the form of eye tubercles and subcentral tubercles, combinations of reticulation and nodules, and the relationships between punctation, reticulation and spinosity, are described and illustrated. These variations are considered in relation to location, time, facies, inferred palaeoenvironment and assemblage. It is shown that the complex of factors connecting these variations with their expression by the phenotype does not allow their unqualified use in establishing palaeoecological parameters, especially where strict polymorphism is not established, or where the timescale of the variations may be several orders of magnitude out of step with the palaeoecological changes inferred from them. The necessity of high magnification illustrations is stressed. The entire range of research into intraspecific variation must be accessed if robust palaeoecological inferences are to be drawn.     

Intra- and interspecific variation in genome size in Lathyrus (Leguminosae)

2C nuclear DNA amounts for 24 species of Lathyrus (section Lathyrus ) were determined using flow cytometry. A greater than two-fold variation was observed, ranging from 10.2 pg in L. basalticus to 24.2 pg in L. latifolius. In general, the perennial species had greater DNA amounts than the annuals. Significant intraspecific variation was observed in five species of Lathyrus (from 10.1% in L. annuus to 28% in L. tingitanus). A positive correlation was observed between DNA values obtained by flow cytometry and those previously determined by microdensitometry. Finally, the distribution of DNA amounts in species within section Lathyrus appears to be continuous.     

Assessment of rampant genitalic variation in the spider genus Homalonychus (Araneae, Homalonychidae)

Abstract. Animal genitalia are often complex and thought to vary little within species but differ between closely related species making them useful as primary characters in species diagnosis. Spiders are no exception, with nearly all of the 40,462 (at the time of this writing) described species differentiated by genitalic characteristics. However, in some cases, the genitalia of putative species are not uniform, but rather vary within species. When intraspecific variation overlaps interspecific variation, it can be difficult (if not impossible) to place a name on a specimen. The quantification of shape variation in genitalia has not often been attempted, probably because until recently it was not a methodologically and computationally simple process. In the two currently recognized species of the spider genus Homalonychus , genitalic variation is rampant in both male and female structures, with some parts of the genitalia (e.g., the retrolateral tibial apophysis) differing in each specimen examined. In this study, geometric morphometric analysis employing landmark data is used to quantify both intra- and interspecific variation in this genus. The large amount of variation is condensed into two or three groups depending on the structures examined, and these groups correspond to either the two species or to previously established mitochondrial DNA clades within one of the species. The results also show that analyses of female structures do not separate the groups as readily as the analyses of the male structures. The large amount of variation present in some structures is not correlated with geography or population genetic structure.