Evidence for coloration plasticity in the yellow‐bellied toad,Bombina variegata

Phenotypic adaptation in terms of background color matching to the local habitat is an important mechanism for survival in prey species. Thus, intraspecific variation in cryptic coloration is expected among localities with dissimilar habitat features (e.g., soil, vegetation). Yellow‐bellied toads (Bombina variegata) display a dark dorsal coloration that varies between populations, assumed to convey crypsis. In this study, we explored I) geographic variation in dorsal coloration and II) coloration plasticity in B. variegata from three localities differing in substrate coloration. Using avian visual modeling, we found that the brightness contrasts of the cryptic dorsa were significantly lower on the local substrates than substrates of other localities. In experiments, individuals from one population were able to quickly change the dorsal coloration to match a lighter substrate. We conclude that the environment mediates an adaptation in cryptic dorsal coloration. We suggest further studies to test the mechanisms by which the color change occurs and explore the adaptive potential of coloration plasticity on substrates of varying brightness in B. variegata and other species.     

Physiological epistasis, ontogenetic conflict and natural selection on physiology and life history

Ontogenetic conflict arises when optima for alleles governingfitness variation differ between juveniles and adults or betweenadult sexes. Loci that govern development of alternative phenotypesin the sexes, hereafter termed morph-determining loci, mediatedevelopment through the endocrine system. Morphotypic selectionis defined to be multivariate selection favoring discrete alternativemorphotypes (e.g., optima). When the optimal combinations ofalleles for alternative morphs differ between the sexes, itgenerates conflicting selection pressure and thus ontogeneticconflict. Selection on morph alleles promotes ontogenetic conflictbecause it perturbs physiological epistasis that governs theexpression of male versus female traits. Expression of physiologicaltraits arises from homeostasis that maintains trait expressionwithin a normal range. The genetic basis of homeostasis is likelyto arise from interactions among several genes (e.g., geneticepistasis) or protein products (e.g., physiological epistasis).For example, endocrine regulation arises from interactions betweengondatropins, which are protein hormones produced by the hypothalamic-pituitaryglands, and steroid hormones, which are produced by the gonads(e.g., HPG axis). The side-blotched lizard system is discussedwith respect to physiological bases of ontogenetic conflict.We also describe a novel molecular marker strategy for uncoveringgenome-wide physiological epistasis in nature. Finally, ontogeneticconflict exerts selection on females to evolve mate selectionor cryptic choice that is reflected in different sires beingchosen for son versus daughter production. We describe how side-blotchedlizard females ameliorate ontogenetic conflict by cryptic choiceof male genotypes to produce sons versus daughters.     

Cryptic plumage signaling in Aphelocoma Scrub-Jays

Recent studies of avian vision and plumage coloration have revealed a surprising degree of cryptic sexual dimorphism, with many examples of male–female differences in UV reflectance that are invisible to humans. We examined the potential for male–female and adult–subadult differences in plumage coloration in the genus Aphelocoma. This group of jays comprises 10 phylogenetic species, which are found across southern and central North America and include cooperatively breeding species, as well as species that form socially monogamous pair-bonds typical of most species of birds. Our goal was to determine whether male–female and adult–subadult differences in plumage coloration were more common in species with complex social systems (i.e., cooperative breeders). We collected a series of reflectance measurements from hundreds of museum specimens and analyzed the results using a model of an avian visual system. We found that age- and sex-related differences were not more frequent in species that practice cooperative breeding. Hence, plumage signaling relating sex and age may not be strongly associated with complex social systems. Rather, the relative lack of a stable and familiar social environment, as well as other selective pressures and constraints (e.g., habitat use and plumage complexity), may have favored a greater degree of age- and sex-related differences in plumage coloration in jays that practice simple biparental care.     

Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration hasbeen suggested to be an important source of diversifying selectionin the radiation of Lake Victoria cichlid fish. Initial variationin female preference is a prerequisite for diversifying selection;however, it is rarely studied in natural populations. In clearwater areas of Lake Victoria, the sibling species Pundamiliapundamilia with blue males and Pundamilia nyererei with redmales coexist, intermediate phenotypes are rare, and most femaleshave species-assortative mating preferences. Here, we studya population of Pundamilia that inhabits turbid water wheremale coloration is variable from reddish to blue with most malesintermediate. We investigated male phenotype distribution andfemale mating preferences. Male phenotype was unimodally distributedwith a mode on intermediate color in 1 year and more blue-shiftedin 2 other years. In mate choice experiments with females ofthe turbid water population and males from a clearer water population,we found females with a significant and consistent preferencefor P. pundamilia (blue) males, females with such preferencesfor P. nyererei (red) males, and many females without a preference.Hence, female mating preferences in this population could causedisruptive selection on male coloration that is probably constrainedby the low signal transduction of the turbid water environment.We suggest that if environmental signal transduction was improvedand the preference/color polymorphism was stabilized by negativefrequency-dependent selection, divergent sexual selection mightseparate the 2 morphs into reproductively isolated species resemblingthe clear water species P. pundamilia and P. nyererei.     

FOUR NEW SPECIES OF TAMBJA BURN, 1962 (NUDIBRANCHIA: POLYCERIDAE) FROM THE INDO-PACIFIC

The genus Tambja previously included 24 described species. Fournew species, T. tentaculata n. sp., T. gabrielae n. sp., T.zulu n. sp. and Tambja victoriae n. sp., from the Indo-Pacificare described. Tambja tentaculata n. sp., from Guam, is theonly known species in the genus with well developed, dorsolaterallygrooved, oral tentacles. Its inner lateral teeth have a bifidinner cusp with two long, sharp denticles. The oral tentaclesof T. tentaculata are more typical of Roboastra species, whilethe shape of the inner lateral teeth is more typical of Tambja.Nevertheless, the arrangement of the two cusps of the innerlateral teeth and the presence of a rachidian tooth withoutdenticles and with a central notch at the anterior edge, typicalof the species of the genus Tambja, suggest the placement withinthis genus. Tambja gabrielae n. sp., from Indonesia and PapuaNew Guinea, has dark green to dark brown ground colour withbright yellow patches scattered on the body. Tambja zulu n.sp. from Durban, South Africa, is characterized by a black groundcolour with slender yellow longitudinal lines. Tambja victoriaen. sp. is a new species from Papua New Guinea and Australiathat has frequently been misidentified as Roboastra arika, characterizedby its blue body colour and yellow lines. The four species aredistinguishable based on differences in body coloration, ofcharacters of the radula and of the reproductive system. Anoverview on distinguishing features of all known Indo-PacificTambja species is presented. (Received 21 June 2004; accepted 20 January 2005)     

Bioenergetic prediction of climate change impacts on northern mammals

Climate change will likely alter the distribution and abundanceof northern mammals through a combination of direct, abioticeffects (e.g., changes in temperature and precipitation) andindirect, biotic effects (e.g., changes in the abundance ofresources, competitors, and predators). Bioenergetic approachesare ideally suited to predicting the impacts of climate changebecause individual energy budgets integrate biotic and abioticinfluences, and translate individual function into populationand community outcomes. In this review, we illustrate how bioenergeticscan be used to predict the regional biodiversity, species rangelimits, and community trophic organization of mammals underfuture climate scenarios. Although reliable prediction of climatechange impacts for particular species requires better data andtheory on the physiological ecology of northern mammals, tworobust hypotheses emerge from the bioenergetic approaches presentedhere. First, the impacts of climate change in northern regionswill be shaped by the appearance of new species at least asmuch as by the disappearance of current species. Second, seasonallyinactive mammal species (e.g., hibernators), which are largelyabsent from the Canadian arctic at present, should undergo substantialincreases in abundance and distribution in response to climatechange, probably at the expense of continuously active mammalsalready present in the arctic.     

Ecological Studies of Seaweeds in McMurdo Sound, Antarctica

Three species of benthic marine macroalgae comprise the chiefcomponents of the seaweed flora of McMurdo Sound, Antarctica.Quantitative studies at Cape Evans demonstrate a depth-relateddistribution pattern, with Iridaea cordata (Turner) Bory inshallow water, Phyllophora antarctica A. and E. S. Gepp abundantand fertile at intermediate depths, and Leptophytum coulmanicum(Foslie) Adey dominant below 20 m. The vertical distributionof species is correlated with irradiance levels. At sites withthinner annual sea ice and less snow accumulation (e.g., CapeEvans, Cape Royds, and Granite Harbor), vertical distributionsare shifted downward relative to those at sites that remaincovered most of the year with thick or snow-covered fast ice(e.g., Cape Armitage and New Harbor). Disturbance caused byice scour and anchor ice probably determines the upper limitof algal distribution; herbivory is apparently absent. There is a disproportionate representation of cystocarpic femalegametophytes in populations of I. cordata and P. antarctica.Perennation via persistent basal crusts and apogamic recyclingof gametophytes are suggested as factors structuring phase distribution.Although the overall size of I. cordata blades is greater (andcystocarpic plants more abundant) at Cape Royds than at CapeEvans, cystocarpic blades are similar in minimum size at bothsites, indicating a threshhold size or age for the onset ofreproduction in this species.     

Experimental manipulation of shell color and morphology of the limpets Lottia asmi (Middendorff) and Lottia digitalis (Rathke) (Mollusca: Patellogastropoda)

We experimentally show that substratum can determine an individual patellogastropod's color and morphology. Lottia asmi (Middendorff), previously considered a high-domed, black stenotopic species on trochid gastropods, is similar to other northeastern Pacific limpet species with low profile and tessellated color patterns, when it is translocated to rock substrata. Lottia digitalis (Rathke), a highly variable species with at least two ecological variants that have been considered to be genetically determined, changes between these two forms when translocated from stalked barnacles to rocks. Color changes because the ingested pigments (algal, periostracal, etc.) and other materials (e.g., calcium carbonate) vary between substrata; morphological changes occur as responses to the topographical complexity and constraints of substrata. The geographical distribution of ecological variants of polytypic limpet species, and the ability to achieve cryptic coloration, may be determined by the geographic distributions of algae on which the limpets feed rather than by intrinsic characteristics of the limpets.     

An Experimental Investigation into the Response of Some New Zealand Sand Dune Species to Salt Spray

The tolerance to salt spray of 29 species, mainly from New Zealandsand dunes, was investigated. Plants were grown in water culturein a glasshouse and subjected to overhead salt spraying at intervals.Growth rates in many species were reduced by salt spray buta significant decrease occurred only in six native herbs. However,many species showed sensitivity in leaf necrosis. Tolerant speciesincluded Scirpoides nodosa, Elymus farctus and Desmoschoenusspiralis. Ammophila arenaria, tolerant of spray as an adult,was less so when younger. There was little correlation between tolerance to salt sprayand tolerance to root salinity. Some species were tolerant toboth, e.g. S. nodosa and E. farctus, and some intolerant toboth, e.g. Wahlenbergia congesta. One species, Lupinus arboreus,was glycophytic in respect to root salt but tolerant of aerialsalt. Other species, such as Senecio elegans L. and Austrofestucalittoralis, were intolerant of salt spray but tolerant of mediumroot salinities. For some species salt spray tolerance correlated well with fielddistribution, e.g. D. spiralis and Bromus diandrus. However,some species present in semi-fixed dunes close to the sea havemuch lower tolerance than would be expected from their fieldsituation, e.g. W. congesta. This apparent inconsistency couldbe explained by the ameliorating high rainfall on the West Coast,or protection by ridges. One environmental variable alone, suchas salt spray, could not explain the field distribution formany species. Salt spray, growth rate, live leaf area, New Zealand, dune species, root salinity     

Biotic Assemblages and Ecological Controls on Reefs and Banks of the Northwest Gulf of Mexico

This paper summarizes the results of investigations of the ecologyof reefs and banks in the northwestern Gulf of Mexico. Nearshoresurface waters are turbid out to approximately the 10 m isobath.A turbid nepheloid layer up to 20 m in thickness exists beyondthis depth. Seasonal temperature and salinity variability ishigh in nearshore waters. At the shelf edge, the temperatureto 50 m depth remains above 19°C. Topographic prominencesare common in the region. Most are surface expressions of thediapirism of underlying salt domes derived from deeply buriedJurassic salt deposits. Biotic zonation on the banks is primarilydepth related. Zones of major reef-building include the Diploria-Montastrea-Porites Zone (15–36 m), the Madracis Zone (28–46m), the Stephanocoenia-Millepora Zone (36–52 m), and theAlgal-Sponge Zone (45–98 m). A zone of minor reefbuildingon some banks is the Millepora Zone (18–52 m). An AntipatharianTransitional Zone exists from 56 to over 100 m on some banks.The Nepheloid Zone near the base of the banks is a zone of noreef-building. Not all zones are present on all banks. The communitystructure and depths of these zones depend on and are modifiedby the regional current regime, depth of the bank crests, substratecharacteristics, winter temperature minima, river influences,and the relative depth and thickness of the nepheloid layer.Nearshore communities are warm temperate in nature, though tropicalorganisms are occasionally abundant. Progressing offshore, thebenthos becomes increasingly tropical. The northerly locationand isolated nature of the Flower Gardens have lead to reducedcommunity diversity (e.g., only 18 of the 55 Western Atlantichermatypic coral species exist), but not reduced abundancesor growth rates of the species present. Assemblages on otherbanks exist below the tolerance limits of thriving tropicalreefs due to their frequent immersion in turbid water, excessivecrest depths, or lower minimum winter temperatures.     

Short-term changes in the mesozooplanktonic community in theSeine ROFI (Region of Freshwater Influence)(eastern English Channel)

Discrete-depth, hourly mesozooplankton samples were collectedover a 92 h period in May 1992 at an anchor station within theSeine Region of Freshwater Influence (ROFI) (English Channel).The mesozooplankton community defined as a euryhaline marineassemblage was dominated by the calanoid copepods Acartia spp.,Temora longicornis and Centropages hamatus, the cladoceran Evadnenordmanni and the appendicularian Oikopleura dioica. The semi-diurnaltidal current was the dominant factor in determining the short-termtemporal changes in the community in terms of density and speciescomposition so that zooplankton patches displayed oscillatingmotion in relation to tidal advection. Although a few species(e.g. Pleurobrachia pileus) exhibited higher densities aroundlow tide, maximum densities were observed for most species (e.g.T.longicornis and E.nordmanni) around high tide, according tosalinity variations. Diurnal changes were only reported forcyclopoid copepods (i.e. Halicyclops sp. and Cyclopina sp.)which wer$$$ mainly endobenthic during the day and moved intothe water column at night. Besides temporal changes in depth-averageddensities, most species exhibited vertical migrations at dieland/or tidal periods. Tidal vertical migrations were reportedonly for a few taxa and could be the result of passive mechanisms(e.g. vertical mixing) rather than of active behaviour. Dielvertical migrations were observed in most of the abundant taxa.While this migration pattern did not appear to be an adaptationto predator avoidance within the Seine ROFI, it could regulatehorizontal transport of organisms and promote their retention.The consequences of the short-term mesozooplankton fluctuationsfor sampling designs are discussed.     

Nouvelles formulations des regles ecologiques connues sous le nom de reegle de Bergmann et loi de Jordan: Amendments of the ecological rules known as Bergmann's and Jordan's rules

Measurements of populations of planktonic and micronektonicspecies from the Atlanto-mediterranean region (about 10,000specimens) have lead to improvements in Bergmann's rule relatingto the increase in size with latitude. There are three cases : Mediterranean specimens may be smaller(e.g. the mysid Eucopia hansent), equal to (e.g. the decapodcrustacean Gennadas elegans) or larger than Atlantic ones (e.g.the thecosomatous genus Cymbulia). All the species in the last group have their principal distributionin warm ocean waters. In the Atlantic, tropical species (e.g.the euphausiid Euphausia gibboides) decrease in size in thenorthern parts of their range while temperate species (e.g.the decapod crustacean Sergesles corniculum) decrease in sizetowards both the pole and the equator. The comparison with the number of vertebrae of fish, which increasesas does the size according to Jordan's rule, is interesting:though correct for cold water species (e.g. Merlucdus merluccius),this rule cannot be applied to warm water species (e.g. Merlucciussenegalensis). Thus, these rules must be corrected like this:- "a species reachesits maximal size in high, intermediate or low latitudes of itsarea if it has a boreal, temperate or tropical distribution"; - "the number of vertebrae increases with latitude for borealfish and decreases for tropical ones".     

Dietary mineral content influences the expression of melanin-based ornamental coloration

Many animals develop bold patches of black or brown colorationthat are derived from melanin pigments and serve as sexual orsocial signals. At present, there is much debate among behavioralecologists over whether melanin-based color signals are costlyto produce. Studies that have manipulated crude aspects of nutrition(i.e., total food intake) or health have generally found melanin-basedplumage ornaments to be less responsive to such factors thanother types of extravagant color (e.g., carotenoid or structuralbased). However, a recently advanced hypothesis argues thatlimited minerals in the diet, such as calcium (Ca), zinc (Zn),and iron (Fe), may serve to increase melanin pigment productionand maintain signal honesty. Here, I experimentally tested whethervariation in the calcium content of the diet affects the colorand extent of melanin-based plumage in male zebra finches (Taeniopygiaguttata). Calcium supplementation increased the size, but notdarkness, of the black breast plumage patch in fledgling andadult males; however, sexually selected, carotenoid-based redbeak coloration was not affected by the diet manipulation. Theseresults are the first to support the idea that acquisition ofminerals from the diet is a unique, limiting factor for theexpression of ornamental melanin coloration in animals.     

Fitness correlates of male coloration in a Lake Victoria cichlid fish

Sexual selection by female choice has contributed to the rapidevolution of phenotypic diversity in the cichlid fish speciesflocks of East Africa. Yet, very little is known about the ecologicalmechanisms that drive the evolution of female mating preferences.We studied fitness correlates of male nuptial coloration ina member of a diverse Lake Victoria cichlid lineage, Pundamilianyererei. In this species, male red coloration is subject tointraspecific sexual selection by female mate choice. Male nuptialcoloration plays a critical role also in reproductive isolationbetween this species and the closely related sympatric speciesP. pundamilia. Here, we show that P. nyererei male colorationis carotenoid based, illustrating the potential for honest signalingof individual quality. In a wild population, we found that variationin male coloration was not associated with variation in a setof strongly intercorrelated indicators of male dominance: malesize, territory size, and territory location. Instead, the 2male characters that predominantly determine female choice,territory size and red coloration, may be independent predictorsof male quality: males with bright red coloration and largeterritories had lower parasite infestation rates. As a result,female preferences tended to select against heavily parasitizedmales. Consistent with parasite-mediated sexual selection, maleshad higher and more variable parasite loads than females.     

Temperature and the Vegetative Growth of Three Saudi Arabian Herbs

In Saudi Arabia, Artemisia abyssinica is a perennial, sand-stabilizingspecies which is common in the great inland deserts; Rumex nervosusis a medicinal herb of lowland distribution; Verbesina encelioidesis an arable weed of similar distribution to R. nervosus, butis also locally common in certain fertile inland and montanehabitats. Typical environments of these species are sharplycontrasted in climate. To see if temperature played any partin limiting these species to their respactive habitats, seedlingsof all three (including two potentiallyseparate lowland andmontane populations of V. encelioides) were grown under controlled-environmentconditions over a range of different temperatures. Artemisia abyssinica proved to be innately slow-growing andto exhibit a high temperature optimum, though with a shallowresponse-gradient in respect of growth over-all and of partitioningbetween root and shoot. Rumex nervosus and both populationsof V. encelioides were quite unlike this, being faster-growing,plastic, and with clear, low temperature-optima Despite certain morphological distinctions, the two populationsof V. encelioides differed little in their whole-plant physiology.However, previous work had established that the montane population,like A. abyssinica, was protected from germination at high constantor fluctuating temperatures. The lowland population, like R.nervosus, was not. Differential conbinations of germinativeand vegetative behaviour were thus postulated as facilitatingthe wide natural distribution of V. encelioides. General conclusions were also drawn concerning the locationon a mesic-xeric continuum of the three species, and also oftwo others studied in a set of experiments published previously. Artemisia abyssinica Sch. Bip., Rumex nervosus Vahl., Verbesina encelioides (Cav.) Benth. et Hook., F. ex A. Gray, growth analysis, temperature, rsponse surfaces, plant distribution     

Influence of the Agulhas Current on the distribution of lanternfish larvae off the southeast coast of Africa

Spatial and temporal distribution patterns of lanternfish larvaealong the southeast coast of Africa were analysed in relationto oceanographic conditions. Investigations werebased on theplankton collections made during winter, spring and summer monthsof 1990–1991. The warm southward-flowing Agulhas Currentis the dominant large-scale oceanographic feature in the area.The number of species of myctophid larvae collected per cruiseranged from 35 to 38. The most abundant species differed fromone season to the other.Afew species showed marked seasonalityin their occurrence, e.g. Scopelopsis multipunclatiis only appearedin winter and Hygophum hygomii showed the highest abundancesin winter. The majority of species occurred in relatively lowconcentrations during all three periods. Relatively large concentrationsof lanternfish larvae of most species sometimes occurred veryclose inshore (especially in the north of thestudy area) inwater depths of 50–100 m. This was related to shorewardintrusions ofAgulhas Current surface water. Low numbers of larvaeof few species appeared on the inshore shelf of the southernsector of the study area, where cold central Indian Ocean wateris forced onto the shelf by kinematic upwelling.     

Spatial Separation of Ancestral Genomes in the Wild Grass Milium montianum Parl.

Previous work showed a strong tendency for genomes from twodifferent parents to be spatially separated in cell nuclei ofseveral man-made F₁ hybrids between grass species. An importantquestion therefore is whether similar nonrandom genome dispositionoccurs in wild species. Milium montianum Parl. (2n = 22) isa naturally occurring allopolyploid grass combining two geneticallydissimilar chromosome sets (V and M genomes), each originatingfrom a different ancestral species. These two ancestral genomeswere easily discriminated as all V genome chromosomes were largerthan all M genome chromosomes. In two-dimensional spread preparations,the V genome derived from M. vernale Bieb. (2n = 8), and theM genome (of different but uncertain origin) showed a highlysignificant tendency to lie apart. Generally, the V chromosomestended to surround the M chromosomes in both mitotic and meioticnuclei suggesting that this arrangement persists throughoutplant development. Such nuclear organization is probably undergenetic control and may facilitate some independent behaviourof ancestral genomes in allopolyploids. Indeed it may play asignificant role in plant evolution and speciation, especiallyif different intranuclear positions (e.g. central or peripheral)are correlated with preferential phenotypic expression of ancestralgenes. Milium montianum Parl., Gramineae, allopolyploid, spatial chromosome disposition, ancestral genome separation, plant speciation and evolution     

Water-column chlorophyll in an oligotrophic environment: correction for the sampling depths and variations of the vertical structure of density, and observation of a growth period

The chlorophyll content of a water column (WCC), which is commonlyused as an index of the phytoplankton abundance, is affectedby the choice of the sampling depths and by the variations ofthe vertical structure of density. For instance, the thicknessof the water layer, between two sigma-t values, which containsthe deep chlorophyll maximum, can vary with internal waves.The resulting noise often dominates the mesoscale variationsof the observed water-column chlorophyll (OWCC). Sigma-t dependentstatistics (mean, standard deviation) of the chlorophyll concentrationare computed using the observations at 29 casts from a 22-day-longfixed station in an oligotrophic environment at 15•S, 173°E.For each cast, these statistics, the sampling depths, and thewater density at these sampling depths, allow the estimationof a station-dependent ‘expected water-column chlorophyll’(EWCC). The ratio of EWCC to the overall likelihood of WCC duringthe fixed station (i.e. the mean of all OWCC) is a measure ofthe effect of sampling and variable density structure at eachcast. When this effect is removed, the noise in WCC estimatesdecreases significantly. The time variations of WCC during thefixed station then show a trend with relatively high valuesduring the first days, followed by a 12-day-long period withlow values. A regular increase occurred from 1 October, whichwas accompanied by high carbon fixation rates and was mainlydue to an increase of the chlorophyll concentration betweenthe surface and the deep chlorophyll maximum. New productionduring this active phase was estimated to be 535 mgC m^–2day^–1, corresponding to 62% of the total production. Breakingof internal waves which were recorded at the beginning of thegrowth phase and vertical mixing of nutrients can explain theobservation.     

Evolution of Anoline Lizard Display Behavior

Based on my conceptual framework of anoline display behavior,I am suggesting the following evolutionary trends. Lateral presentationduring display was probably promoted by monocular vision. Alongwith lateral presentation, postures evolved to increase lateraloutline. These postures which magnified body size were probablyof selective advantage within aggressive social contexts sincelarger animals tend to dominate smaller ones through bluff.Body movement evolved along with lateral orientation and size-enhancingpostures. These movements would be most effective if they complementedlateral orientation. Effectors available for such movementswere primarily pre-adapted for vertical motion. The patternsof movement generated were probably simple oscillatory bobbingmovements by the head which were weakly stereotyped, interspecificallysimilar, appearing in many contexts, and having a weakly definedinformation content. Events having selective advantage for speciesrecognition promoted stereotypy of bobbing behavior into species-uniquedisplays; each species had its unique signature display whichserved in a manifold communicatory capacity. The signature displayappeared in assertion, courtship, and challenge contexts. Itsinformation content varied depending upon context and recipientof the display (e.g., male or female). Besides the stereotypedaspects of the display, certain features remained variable withpotential information significance. Core variability (see text)promotes individual recognition and may be the origin of newunique display patterns as sibling species emerge. Display modifiers(see text) are variable display features shared by members ofa population (many being shared interspecifically) that providea graded appearance to display performance; modifiers can indicatelevel of arousal and facilitate interspecific communication.For some species display repertoire size seems to have evolvedfrom a single display (signature display) to repertoires ofmultiple displays; these subsequent displays are generally restrictedto aggressive interactions.     

The dynamic ups and downs of genome size evolution in Brassicaceae

Crucifers (Brassicaceae, Cruciferae) are a large family comprisingsome 338 genera and c. 3,700 species. The family includes importantcrops as well as several model species in various fields ofplant research. This paper reports new genome size (GS) datafor more than 100 cruciferous species in addition to previouslypublished C-values (the DNA amount in the unreplicated gameticnuclei) to give a data set comprising 185 Brassicaceae taxa,including all but 1 of the 25 tribes currently recognized. Evolutionof GS was analyzed within a phylogenetic framework based ongene trees built from five data sets (matK, chs, adh, trnLF,and ITS). Despite the 16.2-fold variation across the family,most Brassicaceae species are characterized by very small genomeswith a mean 1C-value of 0.63 pg. The ancestral genome size (ancGS)for Brassicaceae was reconstructed as ^anc1C = 0.50 pg. Approximately50% of crucifer taxa analyzed showed a decrease in GS comparedwith the ancGS. The remaining species showed an increase inGS although this was generally moderate, with significant increasesin C-value found only in the tribes Anchonieae and Physarieae.Using statistical approaches to analyze GS, evolutionary gainsor losses in GS were seen to have accumulated disproportionatelyfaster within longer branches. However, we also found that GShas not changed substantially through time and most likely evolvespassively (i.e., a tempo that cannot be distinguished betweenneutral evolution and weak forms of selection). The data revealan apparent paradox between the narrow range of small GSs overlong evolutionary time periods despite evidence of dynamic genomicprocesses that have the potential to lead to genome obesity(e.g., transposable element amplification and polyploidy). Toresolve this, it is suggested that mechanisms to suppress amplificationand to eliminate amplified DNA must be active in Brassicaceaealthough their control and mode of operation are still poorlyunderstood.