Grazing preferences of diadematid echinoids in Fiji

Grazing preferences of two species of Diadema and two species of Echinothrix, including two colour morphs of Echinothrix calamaris, were investigated by gut contents analysis, in situ feeding observations, and grazing preferences trials in aquaria. Grazing preferences were compared to the distribution and abundance of diadematid sea urchins and the percentage cover of algal and seagrass species throughout Sosoikula Reef and Nukubuco Reef, Fiji. Results showed that grazing was selective, with distinct preferences between sea urchin genera, species, and colour morphs of E. calamaris. Preferred species of algae were non-calcareous, with reportedly low concentrations of tannins, phenols and bioactive compounds. Both Diadema savignyi and D. setosum selected Codium geppiorum as their most preferred species, followed by Hydroclathrus clathratus. All Echinothrix favoured Hy. clathratus, with both colour morphs of E. calamaris next selecting Padina pavonica and E. diadema selecting green filamentous algae. The seagrass species Syringodium isoetifolium was only grazed in significant quantities by E. calamaris (b) and E. diadema. This reflected species distributions in the seagrass bed. Peak abundances of diadematid sea urchins coincided with many of their grazing preferences at their maximum percentage cover. However, only E. diadema and D. savignyi had significant correlations with preferred algal/seagrass species (E. diadema with Co. geppiorum, and D. savignyi with G. marginata) throughout the subhabitats identified on the reefs.     

Taxonomic significance of spine morphology in the echinoid genera Diadema and Echinothrix

Abstract. The spine morphology of all established species of Diadema and Echinothrix, including 2 color morphs of E. calamaris, were examined externally and internally via transverse sectioning to identify diagnostic species features and to assess the morphological relationship between species. Forty‐nine different morphological characters were measured and analysed using ordination by multi‐dimensional scaling (MDS) and cluster analysis. Specimens of Diadema paucispinum and D. setosum had very distinct spine structures. In D. paucispinum, the spines were more robust than those of other species of Diadema. This was evident in the spine's internal structure, with large, closely packed solid wedges, a small axial cavity, and rings of trabeculae throughout the spine's length. The spines in D. setosum were distinctive because of their length in relation to test size and the reduced flaring of their verticillations. The spines of other members of this genus were very similar to each other. Without careful sectioning, the spines from specimens of D. antillarum, D. ascensionis, D. mexicanum and D. savignyi were difficult to differentiate. The internal structures of spines for each species did, however, possess a combination of features that differentiated the species. Such features included the shape, orientation, and number of solid wedges, the presence or absence of spokes and rings of trabeculae between the solid wedges, and the presence or absence of tissue within the axial cavity. Individuals of Diadema palmeri also had spines morphologically similar to other species, however, the red pigmentation of these spines (in life and when preserved) made them easily distinguishable. The spine structures of the 2 species of Echinothrix were starkly different, while the white and brown color morphs of E. calamaris had morphologically distinctive ambulacral and interambulacral spines. The blunt, open‐tipped interambulacral spines, with reticular tissue present in the axial cavity of the white color morph, were easily distinguished from the pointed, closed‐tipped spines, with a hollow axial cavity found in the brown color morph. Such differences indicate that the brown color morph is either a subspecies or a separate species. Taken together the data show that each species has significant morphological differences in the structure of the spines. It is evident from our data that spine morphology is a useful tool to differentiate these commonly confused species.     

Genetic differentiation between two color morphs of <Emphasis Type="Italic">Apogon taeniophorus</Emphasis> from southern Japan

The anterior half of the mitochondrial 16S rRNA gene (ca. 610bp) was compared for two color morphs (spotted and lined types) of a dark-striped cardinalfish, previously identified as Apogon taeniophorus. Phylogenetic analyses using maximum-parsimony (MP) and neighbor-joining (NJ) methods, with haplotypes of A. cookii as an outgroup, showed that the haplotypes of each color-morph were reciprocally monophyletic with 100% bootstrap values. In addition, the degree of sequence difference between the two morphs was comparable to that existing between the other clearly distinct congeneric species. These results, together with the differences in coloration and overlapped geographical ranges, indicated that the two color morphs of A. taeniophorus represent two distinct species.     

Learning by the parasitoid wasp, Aphidius ervi (Hymenoptera: Braconidae), alters individual fixed preferences for pea aphid color morphs

Learning, defined as changes in behavior that occur due to past experience, has been well documented for nearly 20 species of hymenopterous parasitoids. Few studies, however, have explored the influence of learning on population-level patterns of host use by parasitoids in field populations. Our study explores learning in the parasitoid Aphidius ervi Haliday that attacks pea aphids, Acyrthosiphon pisum (Harris). We used a sequence of laboratory experiments to investigate whether there is a learned component in the selection of red or green aphid color morphs. We then used the results of these experiments to parameterize a model that examines whether learned behaviors can explain the changes in the rates of parasitism observed in field populations in South-central Wisconsin, USA. In the first of two experiments, we measured the sequence of host choice by A. ervi on pea aphid color morphs and analyzed this sequence for patterns in biased host selection. Parasitoids exhibited an inherent preference for green aphid morphs, but this preference was malleable; initial encounters with red aphids led to a greater chance of subsequent orientation towards red aphids than predicted by chance. In a second experiment, we found no evidence that parasitoids specialize on red or green morphs; for the same parasitoids tested in trials separated by 2 h, color preference in the first trial did not predict color preference in the second, as would be expected if they differed in fixed preferences or exhibited long-term (> 2 h) learning. Using data from the two experiments, we parameterized a population dynamics model and found that learning of the magnitude observed in our experiments leads to biased parasitism towards the most common color morph. This bias is sufficient to explain changes in the ratio of aphid color morphs observed in field sites over multiple years. Our study suggests that for even relatively simple organisms, learned behaviors may be important for explaining the population dynamics of their hosts.     

Adaptive photosynthetic strategies of the Mediterranean maquis species according to their origin

In consideration of their origin the adaptive strategies of the evergreen species of the Mediterranean maquis were analysed. Rosmarinus officinalis L., Erica arborea L., and Erica multiflora L. had the lowest net photosynthetic rate (P_N) in the favourable period [7.8±0.6 mol(CO₂) m^–2s^–1, mean value], the highest P_N decrease (on an average 86 % of the maximum) but the highest recovery capacity (>70 % of the maximum) at the first rainfall in September. Cistus incanus L. and Arbutus unedo L. had the highest P_N during the favourable period [15.5±5.2 mol(CO₂) m^–2s^–1, mean value], 79 % decrease during drought, and a lower recovery capacity (on an average 54 %). Quercus ilex L., Phillyrea latifolia L., and Pistacia lentiscus L. had an intermediate P_N in the favourable period [9.2±1.3 mol(CO2) m^–2s^–1, mean value], a lower reduction during drought (on an average 63 %), and a range from 62 % (Q. ilex and P. latifolia) to 39 % (P. lentiscus) of recovery capacity. The Mediterranean species had higher decrease in P_N and stomatal conductance during drought and a higher recovery capacity than the pre-Mediterranean species. Among the pre-Mediterranean species, P. latifoliahad the best adaptation to long drought periods also by its higher leaf mass per area (LMA) which lowered leaf temperature thus decreasing transpiration rate during drought. Moreover, its leaf longevity determined a more stable leaf biomass during the year. Among the Mediteranean species, R. officinalis was the best adapted species to short drought periods by its ability to rapidly recover. Nevertheless, R. officinalis had the lowest tolerance to high temperatures by its P_N dropping below half its maximum value when leaf temperature was over 33.6°C. R. officinalismay be used as a bioindicator species of global change.This revised version was published online in March 2005 with corrections to the page numbers.     

Phylogeography of colour polymorphism in the coral reef fish Pseudochromis fuscus, from Papua New Guinea and the Great Barrier Reef

Body colour has played a significant role in the evolution of coral reef fishes, but the phylogenetic level at which colour variation is expressed and the evolutionary processes driving the development and persistence of different colour patterns are often poorly understood. The aim of this study was to examine the genetic relationships between multiple colour morphs of Pseudochromis fuscus (family Pseudochromidae), both within and among geographic locations. Pseudochromis fuscus is currently described as a single species, but exhibits at least six discrete colour morphs throughout its range. In this study, P. fuscus from Papua New Guinea (PNG) and the Great Barrier Reef (GBR), Australia, formed three genetically distinct clades based on mitochondrial DNA (control region) sequence data: (1) yellow and brown morphs from the GBR and southern PNG, as well as an orange morph from southern PNG; (2) a pink morph from southern PNG; and (3) all three morphs (pink, orange and grey) found in Kimbe Bay, northern PNG. The three groups showed deep levels of divergence (d=14.6–25.4%), suggesting that P. fuscus is a complex of polychromatic species, rather than a single widespread species with many different colour morphs. Population genetic analyses indicate that the three clades have experienced unique evolutionary histories, possibly from differential effects of sea level fluctuations, barriers to gene flow and historical biogeography.     

The evolution of phally polymorphism in Bulinus truncatus (Gastropoda,Planorbidae): the cost of male function analysed through life-history traits and sex allocation

In the hermaphrodite freshwater snail Bulinus truncatus, two sexual morphs, euphallic (regular hermaphrodites) and aphallic individuals without a male copulatory organ, co-occur at various ratios in natural populations. Both aphallic and euphallic individuals can reproduce by selfing, but when outcrossing aphallic individuals can only play the female role. A comparison of life-history traits and sex allocation in these two forms provides the opportunity to investigate the evolution and maintenance of sexual polymorphisms. This study was performed to test whether a reallocation of resources from the lost male function to the female function occurs in aphallic snails at the level of both sex organs (sex allocation) and life-history traits. In a first experiment we compared life-history traits over a whole life-cycle under selfing between the two sexual morphs. In a second experiment, the sex organs were weighed to test for a difference in sex allocation between the two morphs. No difference in resource allocation to female function between the two morphs was observed in either experiment. This is in contrast to patterns frequently observed in sexually polymorphic plants, and in a previous study performed on aphally in the same snail species. We discuss the genetic and physiological hypotheses that could explain these results, and their consequences for the evolution and maintenance of phally polymorphism in B. truncatus.     

Diel patterns in sea urchin activity and predation on sea urchins on the Great Barrier Reef

Understanding diel patterns in sea urchin activity is important when assessing sea urchin populations and when interpreting their interactions with predators. Here we employ a combination of surveys and a non-invasive tethering technique to examine these patterns in an intact coral reef system on the Great Barrier Reef (GBR). We also assess local scale variation in relative diurnal predation pressure. Surveys revealed that sea urchins were active and exposed at night. Echinometra mathaei and Echinothrix calamaris were the most abundant species with significantly higher night densities (0.21 and 0.03 ind. m⁻², respectively), than daytime densities (0.05 and 0.001, respectively). Bioassays revealed that exposed adult E. mathaei (the most abundant sea urchin species) were 30.8 times more likely to be eaten during the day than at night when controlling for sites. This observation concurs with widely held assumptions that nocturnal activity is a risk-related adaptive response to diurnal predation pressure. Despite relatively intact predator communities on the GBR, potential predation pressure on diurnally exposed E. mathaei assays was variable at a local scale and the biomass of potential fish predators at each site was a poor predictive measure of this variation. Patterns in predation appear to be more complex and variable than we may have assumed.     

Sexual reproduction of Acropora reef corals at Moorea, French Polynesia

Little information is available on reproductive processes among corals in isolated central Pacific reef regions, including French Polynesia. This study examined the timing and mode of sexual reproduction for Acropora reef corals at Moorea. Spawning was observed and/or inferred in 110 Acropora colonies, representing 12 species, following full moon periods in September through November 2002. Gamete release was observed and inferred in four species of Acropora between 9 and 13 nights after the full moon (nAFM) in September 2002. Twelve Acropora spp. spawned gametes between 5 and 10 nAFM in October 2002, with six species spawning 7 nAFM and four species spawning 9 nAFM. In November 2002, spawning of egg and sperm bundles was observed and inferred in 27 colonies of Acropora austera, 6 nAFM. These are the first detailed records of spawning by Acropora corals in French Polynesia.     

Living in a Phaeocystis colony: a way to be a successful algal species

Evidence is provided showing that in two species of Phaeocystis (P. globosa and P. pouchetii) the colonial cells possess a much higher growth rate than the single cells when grown under identical conditions. Based on the DNA-cell-cycle method gross growth rate of colony cells exceeded those of co-occurring single cells by a factor 1.5 up to 3.8. The dominance of colonies in blooms of Phaeocystis can therefore be primarily due to their significantly high growth rate allowing a rapid bloom formation.Both Phaeocystis species showed ultradian growth but differed in timing of the initiation of the second DNA replication phase. In both species the first DNA-replication period started at the end of the (local) light period and was completed in the early dark period. In P. globosa this was immediately followed by the second DNA-replication period (first half of the dark period). In P. pouchetii this process was delayed by ca. 12 h until the middle of the light period (local noon).Flow cytometric analysis of the cell size and chlorophyll fluorescence showed little variation in colony and single cells of P. pouchetii. In contrast, colonies of P. globosa showed often the presence of two cell morphs, co-occurring in the same colony. The size of both morphs was identical but they differed in chlorophyll fluorescence up to a factor 4. In general the high chlorophyll cell morph dominated (>70% of the total colony cells). Both colony cell morphs were observed in cultures, mesocosms differing in N/P ratio but also in the field.     

Systematic significance of tridentate pedicellariae in the echinoid genera Diadema and Echinothrix

Abstract. The tridentate pedicellariae in all species of Diadema and Echinothrix recognized by Mortensen, plus species described later (to include D. palmeri and two color morphs of E. calamaris) were examined to identify diagnostic species characters, and to determine whether such characters are useful in inferring phylogenetic relationships between species. Nineteen morphological characters were measured and analyzed, and species‐specific characters were identified. The morphometric data were then transformed using gap coding and a parsimony analysis was undertaken. The resulting cladogram for the tridentate pedicellariae present in species of Diadema was compared with the mitochondrial DNA phylogeny of Lessios et al., with a good level of congruence observed. Very narrow forceps‐like tridentate pedicellariae were found to be basal among Recent species, present only in D. setosum and D. palmeri. Members of D. palmeri were found to be unique within the genus, having both the forceps‐like form and a broad form of tridentate pedicellaria. The very narrow forceps‐like form is absent in all subsequent divergent species, while the broad form of tridentate pedicellaria in D. palmeri is basal to the broad forms in D. antillarum, D. mexicanum, D. paucispinum, and both the broad and narrow forms of tridentate pedicellaria of D. savignyi. The greatest similarity was found between the broad forms of tridentate pedicellaria in D. antillarum and D. mexicanum. These species were also found to have narrow forms of tridentate pedicellaria that showed a reasonable level of association to one another and to the rostrate form in D. ascensionis. Since the work of Mortensen, D. ascensionis has been shown, using mitochondrial DNA, to be nested within D. antillarum. The results of this study show that the tridentate pedicellaria in D. ascensionis are distinctly different from all other forms within the genus, to the extent that they belong to a rostrate subclass. This indicates that, among Diadema species, the tridentate pedicellariae are one of the first morphological characters to diverge in genetically isolated populations. Unlike the tridentate pedicellariae in Diadema, the different forms of tridentate pedicellariae in E. calamaris and E. diadema showed a stronger association intraspecifically than between forms interspecifically. The small forms of tridentate pedicellaria of the white and brown color morphs in E. calamaris showed a high level of association, while the large forms showed only a moderate association, far lower than would be expected between color morphs of the same species. This suggests that they are either subspecies or recently diverged separate species. This study demonstrates the taxonomic value contained within the characters of the tridentate pedicellariae for both differentiating species (even subspecies) and inferring phylogenetic relationships between species.     

Ecological mechanisms for coexistence of colour polymorphism in a coral-reef fish: an experimental evaluation

The evolution of different colour morphs and how they are maintained in animal populations is poorly understood. We investigated the mechanisms maintaining yellow and brown morphs of a coral-reef fish, Pseudochromis fuscus, at Lizard Island, on the Great Barrier Reef. Histological examination of the gonads revealed that colour morphs were not sex-limited, therefore sexual selection does not appear to promote dichromatism in this species. The field distributions of the two colour morphs were spatially segregated, limiting the opportunity for negative frequency-dependent selection to operate. Our results support another ecological mechanism of coexistence. The yellow morph occurred in deeper areas, usually close to the reef edge, where there was a proportionally high cover of live branching corals. In contrast, the brown morph occurred in shallower areas, more distant from the reef edge, that were proportionally low in live branching corals. Within these habitats, each colour morph of P. fuscus displayed a close association with similar coloured damselfishes from the genus Pomacentrus. The yellow morph was associated with predominantly yellow damselfishes (P. moluccensis and P. amboinensis) and the brown morph with darker coloured species (P. adelus and P. chrysurus). Multiple-choice experiments in the laboratory revealed that: (1) each colour morph of P. fuscus preferentially selected habitat patches occupied by damselfishes with the same colouration; and (2) differences in microhabitat use between the two colour morphs of P. fuscus were due to the presence of different coloured damselfishes in these microhabitats. P. fuscus is a predator of newly recruited damselfishes and the striking resemblance between each morph of P. fuscus and the damselfish with which it was associated, suggests that aggressive mimicry may promote coexistence of P. fuscus colour morphs.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Male-Driven Evolution in Closely Related Species of the Mouse Genus Mus

Recently, other researchers have found that closely related primate species had a lower male-to-female mutation rate ratio (α) than distantly related species. To determine if this is a general phenomenon affecting other mammalian orders, eleven species or subspecies of the rodent genus Mus and two outgroup species were compared. Intron sequences from a gene in the nonrecombining region of the Y chromosome Jarid1d (Smcy) and its X chromosomal gametolog, Jarid1c (Smcx), were analyzed in a phylogenetic context. The male-to-female mutation rate ratio for all thirteen taxa is approximately 2.5, which is similar to previous estimates in more distantly related rodents. However, when branches with lengths of more than 2.5% were removed from the analysis, the male-to-female mutation rate ratio dropped to 0.9. Thus, in closely related rodents, as in closely related primates, the male-to-female mutation rate ratio is lower than expected. [Reviewing Editor: Dr. Deborah Charlesworth] An erratum to this article is available at.     

Freeze tolerance evolution among anurans: Frequency and timing of appearance

Despite numerous mechanistic studies on physiological responses supporting freeze tolerance in anurans, few have addressed the evolutionary significance of this trait. We thus investigated the phylogenetic relationships among anuran species whose freeze tolerance has been assessed and in combination with new data on freezing tolerance of two closely related species of the European brown frogs (Rana temporaria and Rana dalmatina). The species we studied exhibited short survival times in frozen state (around 8 h for both species). Phylogenetic analysis suggests that freeze tolerance evolved at least two times among Ranidae and one or two times among Hylidae and never in Bufonidae. Furthermore, in order to assess the timing of divergence of this character we used a relaxed molecular clock created, and found that the most recent separation between a freeze tolerant species and a freeze intolerant species dates from 15.9 ± 7.6 Myr (Rana arvalis and R. temporaria). The comparison between these two species thus represents the best current model to understand freeze tolerance evolution. Addressing the evolution of this trait with such large-scale approaches will not only improve our understanding of cold hardiness strategies, but might also create a framework guiding future comparative studies.     

Defensive Behavior in Primary- and Secondary-Host Generations of the Soldier-Producing Aphid, Pemphigus bursarius (Hemiptera: Aphididae)

The genus Pemphigus comprises several species that produce soldiers (defensive morphs) in galls on the primary host. At the moment, it is unclear if host-alternating species also produce defenders on their secondary host. We therefore examined how P. bursarius morphs of the secondary host generations respond to predators to test whether they show defensive behavior. We further examined how this response compares with the antipredator behavior of soldiers in P. bursarius and P. spyrothecae occurring on the primary host. We performed two manipulative experiments using two predatory species to quantify the behavior of the different morphs in response to predators. In both experiments, secondary host morphs of P. bursarius showed no attacking behavior and antipredator behavior in these morphs was limited to escaping natural enemies by walking away. In contrast, the first instars of the primary host generations in both Pemphigus species showed attacking behavior and were capable of killing the predators.     

Genetic and Ecological Characterisation of Colour Dimorphism in a Coral Reef Fish

Synopsis Many recognised species of coral reef fishes exhibit two or more colour variants, but it is unknown whether these represent genetically identical phenotypes, genetic polymorphisms or closely related species. We tested between these alternatives for two colour morphs of the coral reef fish, Pseudochromis fuscus, from Lizard Island (Great Barrier Reef). A molecular analysis using mtDNA did not detect any genetic differentiation between co-occurring ‘yellow’ and ‘brown’ colour morphs. A previous study proposed that these two colour morphs are aggressive mimics of yellow and brown damselfishes. Here, a manipulative field experiment was used to evaluate whether the colour dimorphism in P. fuscus is a phenotypic response to the presence of two different model species. Colonies of either yellow or brown damselfish species were established on different patch reefs, and each of the two different P. fuscus morphs was then placed on the different reefs. Contrary to expectations, all yellow individuals that stayed on the reefs changed to brown, regardless of the model species. No brown individuals changed to the yellow colouration. However, P. fuscus were more likely to emigrate from, or suffer higher mortality on, patch reefs where they were not matched with similarly coloured models. Clearly, yellow and brown P. fuscus are members of a single species with sufficient phenotypic plasticity to switch from yellow to brown colouration.     

Patterns of nocturnal movement of the long-spined sea urchin<Emphasis Type="Italic"> Diadema antillarum</Emphasis> (Philippi) in Gran Canaria (the Canary Islands,central East Atlantic Ocean)

We tagged individuals of the sea urchin Diadema antillarum (Philippi) around the island of Gran Canaria (The Canary Islands) during winter 2001–2002 using a new technique, consisting of the insertion of a hook fastened to a fishing line into the aboral pole (periproctal membrane). This allowed individual identification of tagged sea urchins. The goals were: (1) to quantify nocturnal movements and the homing behaviour of this echinoid on shallow rocky bottoms, and (2) to assess short term spatial and temporal variability of these movements. Tagged sea urchins displayed clear homing behaviour. The mean distance travelled at night was 3.7±1.2 m (range 1.0–5.1 m). Mean speed of nocturnal movement was 33±26 cm h^–1 (range 5–110 cm h^–1). We observed greater movement at midnight than at the beginning and the end of the night.Communicated by H.-D. Franke     

Annual cycle of gametogenesis and spawning in a tropical zoanthid,Protopalythoa sp.

Gametogenesis and spawning have been studied since 1986 in a population of Protopalythoa sp. (Anthozoa, Zoanthidea) from Orpheus Island, Great Barrier Reef. Fertile zooids were gonochoric or hermaphroditic with oocytes and sperm vesicles intermingled in the same mesentery; colonies were single sex or mixed. Oocytes arose in macrocnemes below the actinopharynx and were first observed in July. Their mean diameter increased from < 50 µm to 160–240 µm by November, by which time they contained zooxanthellae. Female zooids each produced 800–2400 ova. No testicular vesicles were visible before October but spermatozoa were present in November and December. Spawning in each of three years occurred in November (4th to 6th nights after full moon) simultaneously with mass spawning of scleractinian corals. The buoyant eggs (along with sperm in the hermaphroditic zooids) were released in bundles. Some large oocytes and mature sperm were still present in December.     

匙叶紫菀,中国菊科一未详知种的补充描述

报道中国菊科紫菀属一未详知种:匙叶紫菀(Aster spathulifolius Maxim.),发现于我国东海的舟山群岛,位于浙江嵊泗县的两个岛上,生于海滨岩石上,并提供特征描述和图片.该种与普陀狗娃花[Aster arenarius(Kitam.)Nemoto]比较近缘,提供了这2种的详细形态区别特征.