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1.
We investigated the predatory effects of Dytiscus alaskanus, a large predaceous diving beetle, on the biomass, species composition and diversity of fishless pond communities. The effects
were tested using presence and absence treatments of D. alaskanus in 24 mesocosms distributed among six ponds. We sampled phytoplankton, zooplankton and macroinvertebrates every two weeks
for a six week period. Periphyton was sampled from the mesocosm walls on the final day. Total macroinvertebrate biomass decreased
in the presence of dytiscids while species richness was not affected. Macroinvertebrate predators, snails and Gammarus lacustris decreased in the dytiscid treatments. Laboratory feeding experiments confirmed feeding preferences consistent with the mesocosm
results. Periphyton biomass was six times greater in the dytiscid enclosures, concomitant with the decreased grazing by gastropods
and other invertebrate primary consumers indicating a benthic trophic cascade. Top–down effects of dytiscids on other predatory
invertebrates led to increased total zooplankton biomass, largely due to increased abundances of large and small cladocerans.
Zooplankton species richness increased in the dytiscid enclosures. Inconsistent with trophic cascade theory, phytoplankton
did not respond to top–down effects of D. alaskanus within the study period. Overall, the results show D. alaskanus predation caused trophic effects via two distinct food chains, a dytiscid–snail–periphyton trophic cascade, and a dytiscid–predatory
macroinvertebrates–zooplankton partial trophic cascade. 相似文献
2.
The colour of the characteristic facial bands in the mangrove crabs Perisesarma eumolpe (De Man) and Perisesarma indiarum (Tweedie) were investigated in relation to species, sex and size. Quantitative red/blue/green (RBG) values extracted from
close-up digital photographs of 27 P. indiarum and 48 P. eumolpe specimens revealed significant differences between species and sexes. Males of both species possessed facial bands characterized
by a greater intensity of blue, whereas green was more pronounced in female facial bands. It is postulated that these colour
differences play a role in intra-specific sexual recognition. There existed a significant positive relationship between size
and the intensity of blue in the facial bands of females of both species, suggesting these traits function as an indicator
of their maturity (and possibly body condition). In large males, facial band colours contrast strongly against the surrounding
mudflat and may play an important role in conspecific signalling during territorial disputes or contests over access to females.
Handling editor: K. Martens 相似文献
3.
Maren Huck Marcelo Rotundo Eduardo Fernandez-Duque 《International journal of primatology》2011,32(5):1133-1152
Life history predicts that in sexually dimorphic species in which males are the larger sex, males should reach sexual maturity
later than females (or vice versa if females are the larger sex). The corresponding prediction that in sexually monomorphic
species maturational rates will differ little between the sexes has rarely been tested. We report here sex differences in
growth and development to adulthood for 70 female and 69 male wild owl monkeys (Aotus azarai). In addition, using evidence from natal dispersal and first reproduction (mean: 74 mo) for 7 individuals of known age, we
assigned ages to categories: infant, 0–6 mo; juvenile, 6.1–24 mo; subadult, 24.1–48 mo; adult >48 mo. We compared von Bertalanffy
growth curves and growth rates derived from linear piecewise regressions for juvenile and subadult females and males. Growth
rates did not differ between the sexes, although juvenile females were slightly longer than males. Females reached maximum
maxillary canine height at ca. 2 yr, about a year earlier than males, and females’ maxillary canines were shorter than males’. Thus apart from canine eruption
and possibly crown–rump length, the development of Azara’s owl monkeys conforms to the prediction by life history that in
monomorphic species the sexes should develop at similar paces. 相似文献
4.
Males of the solitary bee Amegilla (Asarapoda) paracalva employ two mate-locating tactics: aggressive defense of sites from which virgin females are emerging and patrolling flower
patches that are visited by conspecific females. At one study site, a single male was able to control an entire emergence
area for one or more days. Multiple males patrolled one flower patch, interacting aggressively on occasion but no one individual
was able to monopolize this resource. Territorial males at the emergence site secured mates by waiting by tunnels for receptive
virgin females to emerge after metamorphosis. Males patrolling the flower patch pounced upon flower visiting conspecifics
and mated with receptive females there. Territorial males at the emergence site were larger than average individuals, probably
because of the advantage larger males have when grappling with opponents. Flower patrolling males were smaller than territorial
males at the emergence sites, perhaps because of the advantages gained by these males from rapid, agile flight. 相似文献
5.
Pigozzi MI 《Genetica》2011,139(6):771-777
All extant birds share the same sex-chromosome system: ZZ males and ZW females with striking differences in the stages of
sex-chromosome differentiation between the primitive palaeognathus ratites and the large majority of avian species grouped
within neognaths. Evolutionarily close to ratites is the neotropical order Tinamiformes that has been scarcely explored regarding
their ZW pair morphology and constitution. Tinamous, when compared to ratites, constitute a large group among Palaeognathae,
therefore, exploring the extent of homology between the Z and W chromosomes in this group might reveal key features on the
evolution of the avian sex chromosomes. We mapped MLH1 foci that are crossover markers on pachytene bivalents to determine
the size and localization of the homologous region shared by the Z and W chromosomes in two tinamous: Eudromia elegans and Crypturellus tataupa. We found that the homologous (pseudoautosomal) region differ significantly in size between these two species. They both
have a single recombination event on the long arm of the acrocentric Z and W chromosomes. However, in E. elegans the pseudoautosomal region occupies one-fourth of the W chromosome, while in C. tataupa it is restricted to the tip of the long arm of the W. The W chromosomes in these two species differ in their heterochromatin
content: in E. elegans it shows a terminal euchromatic segment and in C. tataupa is completely heterochromatic. These results show that tinamous have ZW pairs with more diversified stages of differentiation
compared to ratites. Finally, the idea that the avian proto-sex chromosomes started to diverge from the end of the long arm
towards the centromere of an acrocentric pair is discussed. 相似文献
6.
Claudio Quezada-Romegialli Mabel Fuentes David Véliz 《Environmental Biology of Fishes》2010,89(2):173-186
To describe comparative population genetic structure of the Chilean silverside Basilichthys microlepidotus and the catfish Trichomycterus areolatus, four rivers and three sites within each river were investigated by the analysis of haplotype polymorphisms of the mitochondrial
Control Region. For both species, analyses revealed significant differentiation among rivers and low differences within rivers.
However, the species differ in haplotype composition; individuals of B. microlepidotus shared some haplotypes in all four rivers, while individuals of T. areolatus showed a different haplotype composition in most rivers. This difference may be explained by the different ecological features
of the species. Assuming that both silversides and catfish were present before the separation of the rivers, B. microlepidotus migrated after river isolation, probably using coastal water, while T. areolatus has probably never migrated between these rivers. The long times that the studied rivers have been separated should be taken
into account in future conservation plans for the freshwater fish of Chile. 相似文献
7.
Yuki Nakamura Fumiko Yukuhiro Masaya Matsumura Hiroaki Noda 《Applied Entomology and Zoology》2012,47(3):273-283
Cytoplasmic incompatibility (CI) is a reproductive phenotype induced by bacterial endosymbionts in arthropods. Measured as a reduction in egg hatchability resulting from the crossing of uninfected females with bacteria-infected males, CI increases the frequency of bacteria-infected hosts by restricting the fertilization opportunities of uninfected hosts in populations. Wolbachia, a type of alpha-proteobacteria, is well known as a CI inducer in a wide range of arthropod species, while Cardinium, a member of the phylum Bacteroidetes, is known to cause CI in one wasp and three spider mite species. In this study, dual infection with Cardinium and Wolbachia induced strong CI in a single host, Sogatella furcifera (Horváth), a planthopper species that is naturally infected with both bacteria. Specifically, infection with Cardinium alone was found to cause a 76 % reduction in egg development, and dual infection with Cardinium and Wolbachia a 96 % reduction, indicating that Cardinium induces CI and the dual infection raises the CI level. This study was the first to document reproductive alteration by Cardinium in a diploid host species. 相似文献
8.
Transposable elements are important factors driving plant genome evolution. Upon their mobilization, novel insertion polymorphisms
are being created. We investigated differences in copy number and insertion polymorphism of a group of Mariner-like transposable
elements Vulmar and related VulMITE miniature inverted-repeat transposable elements (MITEs) in species representing subfamily Betoideae. Insertion sites of these elements were identified using a modified transposon display protocol, allowing amplification of longer fragments representing
regions flanking insertion sites. Subsequently, a subset of TD fragments was converted into insertion site-based polymorphism
(ISBP) markers. The investigated group of transposable elements was the most abundant in accessions representing the section
Beta, showing intraspecific insertion polymorphisms likely resulting from their recent activity. In contrast, no unique insertions
were observed for species of the genus Beta section Corollinae, while a set of section-specific insertions was observed in the genus Patellifolia, however, only two of them were polymorphic between P. procumbens and P. webbiana. We hypothesize that Vulmar and VulMITE elements were inactivated in the section Corollinae, while they remained active in the section Beta and the genus Patellifolia. The ISBP markers generally confirmed the insertion patterns observed with TD markers, including presence of distinct subsets
of TE insertions specific to Beta and Patellifolia. 相似文献
9.
Fungi of the genus Aspergillus can infect all tissues and organs, causing invasive mycosis (aspergillosis). This disease can be fatal, especially in immunocompromised patients. Microbiological monitoring of these infectious agents is obligatory in modern medical facilities. Mobile elements can be used as markers to identify the Aspergillus species and strains found indoors as well as to diagnose aspergillosis. Genomic sequences of two Aspergillus species, A. fumigatus and A. nidulans, were analyzed in silico in order to detect LTR retrotransposons. These species were found to considerably differ in the composition of retrotransposon families. One of the families, present in both Aspergillus species, was phylogenetically quite different from all known fungal retrotransposons. The majority of its elements were damaged copies. Nevertheless, allegedly undamaged LTR retrotransposon copies were described that contained intact ORFs and might be active. 相似文献
10.
Sexually matured rainbow trout, Oncorhynchus mykiss, were experimentally infected with the pathogenic Cryptobia salmositica. Spawning female trout were more susceptible to cryptobiosis than sexually mature males. Most infected females (seven of nine)
with eggs died before or shortly after spawning while all (nine) infected males survived the disease. Also, none of the uninfected
females died. Males initially increased milt production and sperm concentration; however semen production declined as the
disease progressed. Sperm from infected males fertilized more eggs than those from non-infected males. No differences in weight
and survival were observed between progeny of infected and uninfected males. 相似文献
11.
Ke Gao Xiushan Li Fangying Chen Zhenying Guo Josef Settele 《Journal of Insect Conservation》2016,20(1):1-10
Many species of the butterfly genus Phengaris are regarded as endangered in many parts of their distribution. Several species are also widely distributed across northern China. Due to land use change and overgrazing, their habitats are declining and many patches have been lost. This paper investigates the distribution and habitats of the Chinese Phengaris species (of the subgenus Maculinea). Shrub-grassland near forests seem the most frequent habitat for Phengaris, while flat open grasslands are mostly over-grazed and thus survival for Phengaris butterflies there seems difficult. Throughout Europe, P. teleius is an endangered species, while there is still no information on its status in China. To improve the knowledge on the population ecology of P. teleius, its population structure, adult behaviour and movement were studied through mark–release–recapture methods in the Qinling Mountains of Taibai County. Eight grassland patches which were potentially suitable were found in the area in 2013. In total, 480 individuals (274 females) were marked, resulting in an overall recapture rate of 16 %. The average daily population size was 44 butterflies (±23 SD) during the adult flight period. Sixty-seven percent of the females and 38 % of the males moved less than 50 m, and 17 % of recaptured females and 38 % of males moved more than 200 m. The mean movement distance was 107 ± 177 m for males and 182 ± 122 m for females. The majority of the recaptures (86 %) were made within the patches, only a few individuals (14 %) moved between patches. Due to human disturbance and destruction, all of the eight potentially suitable patches are becoming smaller and increasingly isolated, thus these populations of P. teleius may face an increasing risk of extinction, which may well be a tip of the iceberg of habitat loss and fragmentation of P. teleius in Taibai County and possibly beyond. Hence we hope our initial study of P. teleius could have positive impacts on the conservation of Phengaris butterflies in China. 相似文献
12.
Chromosomal inversion polymorphism was characterized in Finnish Drosophila montana populations. A total of 14 polymorphic inversions were observed in Finnish D. montana of which nine had not been described before. The number of polymorphic inversions in each chromosome was not significantly
different from that expected, assuming equal chance of occurrence in the euchromatic genome. There was, however, no correlation
between the number of polymorphic inversions and that of fixed inversions in each chromosome. Therefore, a simple neutral
model does not explain the evolutionary dynamics of inversions. Furthermore, in contrast to results obtained by others, no
significant correlation was found between the two transposable elements (TEs) Penelope and Ulysses and inversion breakpoints in D. montana. This result suggests that these TEs were not involved in the creation of the polymorphic inversions seen in D. montana. A comparative analysis of D. montana and Drosophila virilis polytene chromosomes 4 and 5 was performed with D. virilis bacteriophage P1 clones, thus completing the comparative studies of the two species. 相似文献
13.
In the present study, the effect of chemical cues from two fish species (mosquitofish and pumpkinseed), at different concentrations,
was tested in life history experiments with Daphnia longispina. The two fish species used represent the most abundant planktivores of many Mediterranean shallow lakes (SW Europe), where
the indigenous fish communities have been replaced by such exotic assemblages. Results have shown a similar response of D. longispina to both fish species: kairomones stimulated daphnids to produce more offspring, which resulted in higher fitness (r), relatively to a fishless control. Fish presence also induced an earlier first reproduction, a smaller size at maturity
of daphnids, and the production of smaller-sized neonates. Significant correlations with fish concentration (indirect measure
of fish kairomone concentration) were found for size at maturity and neonate size, for both fish species. These results are
in accordance to the “positive response” observed by other authors, which represents a defence mechanism to face losses caused
by fish predators. The chemically mediated size reduction of mature females and neonates is an adaptive response to the size-selective
predation exerted by fish. Pumpkinseed introduction is very recent in the lake of origin of the daphnids used in the experiments
and its kairomone produced similar effects to mosquitofish in the life history of D. longispina. These results are contrary to the existence of a species-specific kairomone and support the hypothesis of a general fish
kairomone.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
14.
The evolution of reproductive isolation is a prerequisite in the formation of new species. Although there are numerous studies
on ejaculates in lepidopteran insects, ejaculate comparisons among sibling species have not been adequately addressed to understand
possible reproductive barriers to hybridization. Here, we examined the interspecific and intraspecific variations of ejaculates
in the sibling noctuid moths Helicoverpa armigera and Helicoverpa assulta. We found that there were considerable variations in the number of apyrene and eupyrene sperm and the length of eupyrene
sperm. Male pupal mass explained not only a significant proportion of the variation in apyrene sperm number in both H. armigera and H. assulta, but also a significant proportion of the variation in eupyrene sperm number in H. assulta. There was a significant positive relationship between the number of eupyrene sperm and the number of apyrene sperm in both
species. No difference in the length of eupyrene sperm was found between them; however, ejaculates of H. armigera had many more eupyrene sperm than H. assulta had. In H. armigera, large males generally mated with large females. The evolutionary consequences of these differences are discussed in this
paper. 相似文献
15.
The cephalic salivary glands of some species of bees are exclusive and well developed only in Apinae. These glands were studied
with light and scanning electron microscopy in workers, queens and males from the honey bee Apis mellifera, and the stingless bee Scaptotrigona postica in different life phases. The results show that the cephalic salivary glands are present in females of both the species,
and in males of S. postica. Nevertheless, they are poorly developed in young males of A. mellifera. In both species, gland growth is progressive from the time of emergence to the oldest age but, in A. mellifera males, the gland degenerates with age. Scanning electron microscopy shows that the secretory units of newly emerged workers
are collapsed while in older workers they are turgid. Some pits on the surface of the secretory units correspond to open intercellular
spaces. The possible functions of these glands in females and males of both species are discussed. 相似文献
16.
Pia Untalan Olafson Kevin B. Temeyer John H. Pruett 《Experimental & applied acarology》2011,53(2):147-165
17.
In this study, we applied geometric morphometrics to explore variations in the level and pattern of sexual size dimorphism
(SSD) and sexual shape dimorphism (SShD) of the ventral cranium in three different Modern Eurasian newt taxa (Ichthyosaura alpestris, Triturus species group and Lissotriton vulgaris). The ventral cranium is the part of the skull that is more directly related to foraging and feeding. Our results indicate
that the level and pattern of sexual dimorphism in the ventral cranium differ among Modern Eurasian newt taxa. Regarding sexual
dimorphism in skull size, Ichthyosaura alpestris and Triturus species show female-biased patterns (females are larger than males), whereas Lissotriton vulgaris appears to be non-dimorphic in skull size. In I. alpestris and Triturus species, SShD is mostly absent, whereas in L. vulgaris, SShD is more pronounced. A high level of variation between populations in both SSD and SShD indicates that local conditions
may have a profound effect on the magnitude and direction of sexual dimorphism. The significant sexual differences in ventral
cranium size and shape indicate possible subtle intersexual differences in ecological demands due to diet specialisation,
in spite of similar general ecological settings. 相似文献
18.
Transmission of conidia between mates of the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), was studied using two isolates of the entomopathogenic fungus Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) (formerly M. anisopliae). After one beetle was inoculated and caged with a mate for 6 h, conidia were rinsed off each beetle using Tween-80 and pentane
to count conidia transferred. Treated males transmitted more conidia to females than treated females transferred to males.
Untreated partners did not die as quickly as their inoculated mates, but died significantly faster than controls. For beetles
inoculated with ARSEF 7711, the difference in time to death between inoculated beetles and their untreated mates was shorter
when males were inoculated than when females were inoculated. We hypothesize that greater conidial transmission from males
to females was due to their relative positions during copulation and the prolonged post-copulatory mate-guarding characteristic
of males. 相似文献
19.
Within the bee family Halictidae there have been three origins of sociality. Although detection of origins and reversal from
sociality requires phylogenetic studies, at a behavioural level a predisposition to sociality can be detected by analysis
of intra-specific interactions. We studied aspects of nesting biology and behavioural interactions in Lasioglossum (Lasioglossum) majus, a poorly known halictine inhabiting temperate regions of Europe, which is suspected to be solitary. Nests were found to
be largely used by one female, but some were shared by more than one individual. These few nests, whose entrances were very
close to each other, were found to be connected underground. A few individuals were observed to enter in a nest where a female
was waiting, behaving as a guard and allowing the incoming bee to enter the nest. By use of circle-tube experiments, the behavioural
repertoire exhibited by females during encounters was assessed. Levels of withdrawal and cooperative events were comparable
with those observed in other solitary nesting species, but aggressive events were very rare, as in several observed communal
species. We conclude that L. (L.) majus females, despite general solitary nesting, possess behavioural components enabling them to adopt, probably in high nest-density
areas, nest-sharing strategies. A similar kind of local social polymorphism has been observed in two other species of the
subgenus Lasioglossum, but these are the first data available on a European species and the first record of subterranean connections among nests
of halictid bees. 相似文献
20.
Cristina Giacoma Viviana Sorrentino Clement Rabarivola Marco Gamba 《International journal of primatology》2010,31(4):539-551
In some primate species, males and females within a social group emit loud calls in a coordinated manner or chorus. Indri indri emits a very conspicuous loud call that elicits the loud calls of neighboring groups. Previous investigations have hypothesized
that the main functions of the indri chorus are related to territorial announcement, intergroup avoidance, and group cohesion.
We investigated sex differences in indri song. We recorded and analysed songs given by 10 different groups over 160 d. Overall
singing duration did not vary between the sexes. However, males emitted significantly fewer but longer notes. Adult males
and females of each group participated in the song with sex-specific repertoires. Females had a song repertoire of 8 note
types; males shared all of their 6 notes with females. Apart from the initial roars, in all note types shared by both sexes,
male notes were significantly longer than female ones, whereas variations in frequency parameters differed according to the
note type. These findings suggest that indri song may provide cues to conspecifics, such as group size and sex composition,
which could influence interactions between groups. 相似文献