Growth or reproduction: Intrasexual competition in a colonial damselfishStegastes nigricans

Intrasexual competition within colonies of the damselfishStegastes nigricans was investigated. Both males and females held individual territories, and these territories were adjacently distributed, forming distinct conspecific colonies with different size compositions. In both large and small colonies, only relatively large individuals participated in reproduction. Breeding males and females left their territories to court, spawn and aggregate more frequently than non-breeders of the same colonies. Breeders were less frequently attacked by other fish during these excursions than were non-breeders. Most attacks were conducted by breeders of the same sex. This intrasexual aggression may suppress the reproduction of non-breeders at least in large colonies. Non-breeders in large colonies had smaller gonads than breeders of both large and small colonies, but they grew faster than breeders of the same body size in small colonies. This suggests that non-breeders in large colonies allocate energy to growth in order to be reproductively competitive in the future, although only a few of them remained in the same colonies upon maturity. Colony size thus has an effect on the reproductive life histories of individual damselfish.     

Higher resting metabolic rate in long-lived breeding Ansell’s mole-rats (<Emphasis Type="Italic">Fukomys anselli</Emphasis>)

Background

Reproduction is an energetically expensive process that supposedly impairs somatic integrity in the long term, because resources are limited and have to be allocated between reproduction and somatic maintenance, as predicted by the life history trade-off model. The consequence of reduced investment in somatic maintenance is a gradual deterioration of function, i.e. senescence. However, this classical trade-off model gets challenged by an increasing number of contradicting studies. Here we report about an animal model, which adds more complexity to the ongoing debate. Ansell’s mole-rats are long-lived social subterranean rodents with only the founder pair reproducing, while most of their offspring remain in the parental burrow system and do not breed. Despite of a clear reproductive trade-off, breeders live up to twice as long as non-breeders, a unique feature amongst mammals.

Methods

We investigated mass-specific resting metabolic rates (msRMR) of breeders and non-breeders to gain information about the physiological basis underlying the reproduction-associated longevity in Ansell’s mole-rats. We assessed the thermoneutral zone (TNZ) for breeders and non-breeders separately by means of indirect calorimetry. We applied generalized linear mixed-effects models for repeated measurements using the msRMR in the respective TNZs.

Results

TNZ differed between reproductive and non-reproductive Ansell’s mole-rats. Contrary to classical aging models, the shorter-lived non-breeders had significantly lower msRMR within the thermoneutral zone compared to breeders.

Conclusion

This is the first study reporting a positive correlation between msRMR and lifespan based on reproductive status. Our finding contradicts common aging theories, but supports recently introduced models which do not necessarily link reproductive trade-offs to lifespan reduction.

     

Karyological and chemotaxonomical studies of the hybridPelargonium incarnatum ×P. patulum (Geraniaceae) and its parents

Pelargonium incarnatum is a tetraploid species (2n = 40) andP. patulum is diploid (2n = 22). A natural hybrid, collected at the same locality as the parent species, has 2n = 42 chromosomes. The meiosis of the hybrid is practically normal and its pollen fertility corresponds to that ofP. incarnatum. The flavonoid patterns of the parent species and the hybrid are very similar. The origin and phylogenetic implications of this intersectional hybrid are discussed.     

Non-Breeding Eusocial Mole-Rats Produce Viable Sperm—Spermiogram and Functional Testicular Morphology of Fukomys anselli

Ansell’s mole-rats (Fukomys anselli) are subterranean rodents living in families composed of about 20 members with a single breeding pair and their non-breeding offspring. Most of them remain with their parents for their lifetime and help to maintain and defend the natal burrow system, forage, and care for younger siblings. Since incest avoidance is based on individual recognition (and not on social suppression) we expect that non-breeders produce viable sperm spontaneously. We compared the sperm of breeding and non-breeding males, obtained by electroejaculation and found no significant differences in sperm parameters between both groups. Here, we used electroejaculation to obtain semen for the first time in a subterranean mammal. Spermiogram analysis revealed no significant differences in sperm parameters between breeders and non-breeders. We found significantly larger testes (measured on autopsies and on living animals per ultrasonography) of breeders compared to non-breeders (with body mass having a significant effect). There were no marked histological differences between breeding and non-breeding males, and the relative area occupied by Leydig cells and seminiferous tubules on histological sections, respectively, was not significantly different between both groups. The seminiferous epithelium and to a lesser degree the interstitial testicular tissue are characterized by lesions (vacuolar degenerations), however, this feature does not hinder fertilization even in advanced stages of life. The continuous production of viable sperm also in sexually abstinent non-breeders might be best understood in light of the mating and social system of Fukomys anselli, and the potential to found a new family following an unpredictable and rare encounter with an unfamiliar female (“provoked or induced dispersal”). Apparently, the non-breeders do not reproduce because they do not copulate but not because they would be physiologically infertile. The significantly increased testes volume of breeding males (compared to non-breeders) is in agreement with previously found higher testosterone levels of breeders.     

角堇与大花三色堇染色体核型分析

以2份角堇与4份大花三色堇自交系为试验材料,采用染色体常规压片方法,观察和分析了它们的细胞染色体数目、相对长度、平均臂比等核型指标,以明确两种植物细胞学特点,为分类以及育种提供理论依据。结果表明:(1)2份角堇自交系染色体数目均为2n=2x=26,染色体基数为x=13,染色体核型公式分别为2n=2x=26=8m+12sm+6st、2n=2x=26=4m+16sm+6st,核型不对称系数为67.20%~70.10%,核型分类均属于3B。(2)4份大花三色堇自交系均为四倍体,其中2份(EYO-1-2-1-4、DSRFY-1-1-2)染色体数目为44,核型公式为2n=4x=44=4m+16sm+6st、2n=4x=44=16m+24sm+4st;2份(G10-1-3-1-4、XXL-YB-1-1-1-1)染色体数目为48,核型公式分别为2n=4x=48=8m+20sm+20st、2n=4x=48=4m+36sm+8st,核型不对称系数为66.74%~71.77%,核型分类属于2B、3B。     

Monosomic and double monosomic substitutions of Hordeum bulbosum L. chromosomes into H. vulgare L.

Summary One of the aims of the interspecific crossing programme between Hordeum vulgare L. and H. bulbosum L. has been to introgress desirable genes into barley from the wild species. However, despite their close taxonomic relationship there have been few reports of achieving this objective using amphidiploid hybrids. In order to broaden the range of available hybrids, partially fertile triploids between H. vulgare (2n = 2x = 14) and H. bulbosum (2n = 4x = 28) were developed and crossed with H. vulgare as female parent. From 580 progeny which were screened, eight putative single monosomic chromosome substitution lines and one double monosomic substitution were identified by cytological analysis. These involved the substitution of H. vulgare chromosome 1 (two lines), 6 (four lines), 6L (one line), 7 (one line) and 1 + 4 (one line) by their respective H. bulbosum homoeologues. The H. bulbosum chromosome was frequently eliminated during plant development, but it was observed regularly in pollen mother cells of two lines. However, pairing between the H. bulbosum chromosome and its H. vulgare homoeologue was low. Several of the lines were more resistant than their H. vulgare parents to powdery mildew (Erysiphe graminis DC. f.sp. hordei Em. Marchai), net blotch (Drechslera teres Sacc.) and scald (Rhynchosporium secalis (Oudem.) Davis). Apart from their use in studying genome relationships, their value to plant breeders will depend on the ease of inducing translocations between the parental chromosomes.     

Chromosome study of hybrid and gynogenetic offspring of artificial crosses between members of the catfish families Clariidae and Pangasiidae

Synopsis Artificial hybridization between species of the catfish families Clariidae (Clarias macrocephalus) and Pangasiidae (Pangasius sutchi) resulted in first generation offspring comprising two intermediate morphotypes and one morphotype indistinguishable from its clariid parent. The two intermediate morphotypes apparently correspond to hybrid morphotypes 2 and 4 resulting from earlier hybridization experiments between the same parent species (Tarnchalanukit 1986). We did not obtain morphotypes 1 and 3. Chromosome spreads of the relatively pangasiid-like morphotype 2 reveal a diploid number of 57, presumably comprising one set of Clarias (n=27) and one of Pangasius (n=30) chromosomes. The relatively clariid-like morphotype 4 is a triploid with 84 chromosomes, presumably comprising two sets from Clarias (2n=54) and one from Pangasius (n=30). Finally, the morphotype indistinguishable from Clarias, is a diploid with 54 chromosomes, apparently arising from gynogenesis.     

An apomictic polyhaploid obtained from a pearl millet x Pennisetum squamulatum apomictic interspecific hybrid

Summary In a research program to transfer apomixis from Pennisetum squamulatum Fresen to pearl millet, P. americanum L. Leeke, a polyhaploid plant (2n=21) was discovered in the uniform open-pollinated progeny of an apomictic interspecific hybrid (2n = 41) between pearl millet and P. squamulatum. The polyhaploid was shorter, less vigorous and was smaller morphologically than its maternal parent. It probably originated by parthenogenetic development of a reduced gametophyte in the apomictic interspecific hybrid. The most common metaphase I chromosome association in the polyhaploid was 4 bivalents plus 13 univalents. Irregular chromosome distribution, tripolar spindles, bridges and fragments were observed at anaphase I and telophase I. The polyhaploid was male-sterile and partially female- fertile having multiple aposporous embryo sacs in 95% of the ovules. Seed set was 3% when open-pollinated and 33% when pollinated with pearl millet pollen. Low seed set was due to competition among multiple embryos developing in the same ovule. Seventeen progeny from seed produced under open-pollination on the polyhaploid each had 2n=21 chromosomes and were morphologically uniform and identical to the female parent. The expression of obligate apomixis in the polyhaploid conditioned by the P. squamulatum genome between the simplex and duplex condition indicates that apomictic reproduction is possible in nonpolyploid plants.     

Nocturnal foraging by great skuas Stercorarius skua: implications for conservation of storm-petrel populations

At St Kilda, Outer Hebrides, a large colony of great skuas Stercorarius skua feed extensively on one of the largest colonies of Leach’s storm-petrels Oceanodroma leucorhoa in Europe, but little is known about the dynamics of this predator–prey system. Recently published population estimates of storm-petrels make it possible to estimate the impact of skua predation for the first time. Although skuas in the southern hemisphere catch petrels attending breeding colonies at night, it is not known whether congeners in the northern hemisphere also forage during the hours of darkness. We found (using radio-transmitters) that skuas regularly forage at night and (using light intensifying equipment) observed them catching storm-petrels at night. However, skuas also foraged during daylight hours, and it is unknown whether they might also catch storm-petrels at sea. Data on diet composition reveals that the proportion of storm-petrels in skua diet declined between 1996 and 1997, but remained constant thereafter. Although a large proportion of the storm-petrel prey is likely to consist of non-breeders, numbers consumed suggest that breeders and an unknown quantity of transients may also been eaten. The numbers of storm-petrels eaten are not sustainable and may result in substantial long-term population declines. Under current conditions, maintenance of large populations of both Leach’s storm-petrels and great skuas at St Kilda appears to be mutually exclusive.     

Sustainability of the South China tiger: implications of inbreeding depression and introgression

The South China tiger (Panther tigris amoyensis) is critically endangered with 73 remaining individuals living in captivity, all derived from six wild founders since 1963. The population shows a low level of juvenile survivorship and reproductive difficulties, and faces a huge conservation challenge. In this study, inbreeding depression and genetic diversity decline were examined by using pedigree data and 17 microsatellites. The constant B, which is related to the number of lethal equivalents, was estimated to be 0 for the offspring of noninbred parents, but was >0 for the offspring of inbred parents and for all offspring. Percentage of successfully breeding tigers inversely correlated with inbreeding level (r = −0.626, α = 0.05). Taken together, these findings suggest the population is suffering from inbreeding depression in juvenile survivorship and fecundity. No significant correlation was detectable for the mean litter size with f of either dams (r = −0.305, α = 0.46) or kittens (r = 0.105, α = 0.71), indicating litter size was not strongly subject to inbreeding depression. The average number of alleles per locus was 4.24 ± 1.03 (SE), but effective number of alleles was only 2.53 ± 0.91. Twenty-one alleles carried by early breeders at 13 loci were absent in the present breeders and potential breeders. Multilocus heterozygosity was inversely correlated with inbreeding levels (r = −0.601, α = 0.004). These findings suggest rapid allelic diversity loss is occurring in this small captive population and that heterozygosity is being lost as it becomes more inbred. Our phylogenetic analysis supports past work indicating introgression from northern Indochinese tigers in the population. As no wild representatives of the South China tiger can be added to the captive population, we may consider the alternate scenario of further introgression in the interest of countering inbreeding depression and declining genetic diversity.     

Fertile progeny of a hybridization between soybean [Glycine max (L.) Merr.] and G. tomentella Hayata

Summary A colchicine-doubled F₁ hybrid (2n=118) of a cross between PI 360841 (Glycine max) (2n=40) x PI 378708 (G. tomentella) (2n=78), propagated by shoot cuttings since January 1984, produced approximately 100 F₂ seed during October 1988. One-fourth of the F₂ plants or their F₃ progeny have been analyzed for chromosome number, pollen viability, pubescence tip morphology, seed coat color, and isoenzyme variation. Without exception, all plants evaluated possessed the chromosome number of the G. max parent (2n=40). Most F₂ plants demonstrated a high level of fertility, although 2 of 24 plants had low pollen viability and had large numbers of fleshy pods. One F₂ plant possessed sharp pubescence tip morphology, whereas all others were blunt-tipped. All evaluated F₂ and F₃ plants expressed the malate dehydrogenase and diaphorase isoenzyme patterns of the G. max parent and the endopeptidase isoenzyme pattern of the G. tomentella parent. Mobility variants were observed among progeny for the isoenzymes phosphoglucomutase, aconitase, and phosphoglucoisomerase. This study suggests that the G. Tomentella chromosome complement has been eliminated after genetic exchange and/or modification has taken place between the genomes.Journal Paper No. J-13776 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, USA, Project 2763     

Production,morphology, and cytogenetics of Triticum aestivum (L.) Thell × Elymus scabrus (R. Br.) Love intergeneric hybrids obtained by in ovulo embryo culture

Summary Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD), and an apomictic Triticeae species, Elymus scabrus (syn. Agropyron scabrum) (2n=6x=42, HHSSSS), the first successful report of this cross. Nine tiny, underdeveloped, and structureless embryos were obtained in vitro only by in ovulo embryo culture at 4 days after pollination, which gave rise to five mature hybrid plants. All the hybrid plants were vigorous and possessed a phenotype intermediate to the two parents. There were 2n=6x=42 (ABDHSS) somatic chromosomes in the hybrids. There was little or no homology between the parental genomes, as shown by an overall meiotic chromosome association of 32.83 I + 4.08 rod II + 0.21 ring II + 0.18 III + 0.02 IV. The hybrids were completely sterile and so far backcrosses to wheat parent have not been successful. Alternate approaches to induce gene transfer(s) from E. scabrus to wheat are being attempted.Agriculture Canada Contribution No. 398.     

Chromosome banding and pairing behaviour inFestuca andVulpia (Poaceae,Pooideae)

Giemsa C-banding patterns of the grassesFestuca rubra (2n = 6x = 42),Vulpia fasciculata (2n = 4x = 28) and their wild F1 hybrid ×Festulpia hubbardii (2n = 5x = 35) show marked differences between the chromosomes of the two parents that enable unequivocal identification ofFestuca andVulpia chromosomes in the hybrid. Moreover, meiotic banding patterns reveal that both homogenetic (Festuca-Festuca andVulpia-Vulpia) and heterogenetic (Festuca-Vulpia) pairing occurs in the F1. The significance of this in relation to the formation of backcrosses to theFestuca parent and to the evolution of theFestuca polyploid complex in general is discussed.     

Species relationships within Diplotaxis (Brassicaceae) and the phylogenetic origin of D. muralis

Nineteen from the ca. 30 Diplotaxis species including all known haploid chromosome numbers have been analysed for isoelectric focusing patterns of Rubisco, allozymes and RAPDs. D. erucoides (n=7) was clearly separated from all other species as were D. harra and D. crassifolia (n=13 each). Taxa with n=8 had different IEF patterns, but allozyme data grouped D. siettiana, D. ibicensis and D. brevisiliqua together. Species with n=9 were characterised by different IEF patterns, and their position was neither resolved in the allozyme nor in the RAPD tree. Only the D. catholica accessions were strongly clustered together. D. viminea and D. siifolia (both n=10) were kept separate, whereas the n=11 taxa D. tenuifolia, D. cretacea and D. simplex grouped together. Data confirm D. viminea as maternal parent of the allotetraploid D. muralis, and D. tenuifolia as the likely parent.     

Interspecific hybridization between Vigna radiata (L.) Wilczek and V. glabrescens

Summary Interspecific hybrids of the mungbean, Vigna radiata (L.) Wilczek (2n=22) and V. glabrescens (2n=44) were generated with the aid of embryo culture. V. glabrescens x V. radiata hybrids were recovered via germination of the immature embryos. Reciprocal hybrids were obtained via shoot formation from embryonic callus. The authenticity of the hybrids was determined by morphological characteristics, chromosome number, and isozyme patterns. The hybrids were highly sterile upon selfing, but backcrossing to the diploid parent yielded viable seeds. Some of the plants resembled the diploid parent morphologically while others resembled neither parent. The backcross plants were sufficiently fertile to give a large number of mature, selfed seeds. Plants obtained differed morphologically and in their isozyme patterns from either parent, indicating introgression. These progeny populations will be used as bridging materials to transfer pest resistance from the wild tetraploid to the cultivated mungbean.     

我国原生植物假泽兰(菊科)的细胞学研究

该文研究了我国原生植物假泽兰(Mikania cordata)台湾花莲居群、苗栗居群、宜兰居群以及台北居群的染色体数目和染色体形态。结果表明:所有居群的染色体数目为2n=36,第一对染色体为近中部着丝粒染色体,其长臂中部具有次缢痕,显著大于其余染色体。各居群的核型公式皆为2n=18m+18sm,核型均为2B型,染色体内不对称性指数(A_1)的变化范围为0.38~0.39,染色体之间不对称性指数(A_2)的变化范围为0.30~0.32。此为我国假泽兰居群染色体数目的唯一报道,也是对该种核型的首次报道。结合前人对假泽兰染色体数目的研究结果,认为假泽兰存在种内非整倍性现象,但在中国台湾的居群中目前仅发现基于x=18的二倍体(2n=36)。假泽兰的第一对染色体的长臂中部具次缢痕,与假泽兰属已报道的核型相似,这一次缢痕可作为假泽兰属的细胞学标记。核型资料、野外观察以及ISSR数据显示薇甘菊(M.micrantha)在我国的成功入侵与入侵种和本土种之间的杂交渐渗无关。根据标本记录和野外考察结果,我国假泽兰现在的分布区与过去相比有了很大的缩减,推测生境的破坏和薇甘菊的侵入可能是导致假泽兰在中国台湾地区逐渐消失的主要原因。     

Production,morphology, and cytogenetic analysis of Elymus caninus (Agropyron caninum) x Triticum aestivum F1 hybrids and backcross-1 derivatives

Summary Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD) and wheatgrass, Etymus caninus (Agropyron caninum) (2n=4x=28, SSHH) — the first successful report of this cross. Reciprocal crosses and genotypes differed for percent seed set, seed development and F₁ hybrid plant production. With E. caninus as the pollen parent, there was no hybrid seed set. In the reciprocal cross, seed set was 23.1–25.4% depending upon wheat genotype used. Hybrid plants were produced only by rescuing embryos 12–13 days post pollination with cv Chinese Spring as the wheat parent. Kinetin in the medium facilitated embryo germination but inhibited root development and seedling growth. The hybrids were vigorous, self sterile, and intermediate between parents. These had expected chromosome number (2n=5x=35, ABDSH), very little chromosome pairing (0.51 II, 0.04 III) and some secondary associations. The hybrids were successfully backcrossed with wheat. Chromosome number in the BC₁ derivatives varied 54–58 with 56 as the modal class. The BC₁ derivatives showed unusually high number of rod bivalents or reduced pairing of wheat homologues. These were sterile and BC₂ seed was produced using wheat pollen.     

Over-wintering strategies of the Lesser Sheathbill Chionis minor in an impoverished and insular environment

Summary The Lesser Sheathbill Chionis minor is an opportunistic predator and scavenger that breeds on sub-Antarctic islands during the summer season, when many other seabirds are present, especially penguins on which it is kleptoparasitic. It is a poor flyer and over-winters on its breeding grounds, where it faces a diminished food supply and low temperatures. Its foraging behaviour was suspected to be plastic enough to respond to such a variable environment, and we show how this species enlarged its niche to survive in winter. Population movements, dietary changes and monthly weight gains were quantified during a 13-month period of observation. Mortality rates, calculated over a 19-year period of banding, appeared to be age dependent: they decrease, due to competition, from juveniles to subadults, adult non-breeders, and breeders. One of the survival strategies described here is, to our knowledge, unique among birds. After the Crested Penguin colonies have been deserted, some adult sheathbills (mainly females) remained territorial, extending their territory size and diet while their partners moved to previously undefended zones in King Penguin colonies (permanent and large in the Crozet archipelago), where they competed for a winter territory and subsequently associated with another mate. After this winter mating, mobile sheathbills returned the following summer to their breeding territory and previous mate.     

Karyomorphological analyses and heterochromatin characteristics disclose phyletic relationships among 2n = 32 and 2n = 36 species ofOrchis (Orchidaceae)

The karyotypes of eight taxa ofOrchis L. with 2n = 32 and 2n = 36 have been investigated using morphometrical measurements following staining with Feulgen, Giemsa (C-banding) and the DNA specific fluorochrome Hoechst 33258. The karyotypes ofO. coriophora subsp.fragrans, andO. papilionacea proved to be the most asymmetrical, whileO. morio andO. longicornu exhibited the most symmetrical karyotypes. Using C-banding and the fluorochrome H33258 only the taxa with high asymmetry indices showed the presence of differentially stained chromatin bands. In most chromosomes heterochromatin bands were present at the telomeric position. The present results seem to indicate that the analysed species do not form a homogeneous group and further subdivisions are possible, which, in turn, do not always correlate with divisions based on morphological characters. Both karyomorphology and heterochromatin distribution coincide in indicating a possible evolutionary pathway.     

Lazy group members are substitute helpers in carrion crows

In many cooperatively breeding societies, helping effort varies greatly among group members, raising the question of why dominant individuals tolerate lazy subordinates. In groups of carrion crows Corvus corone corone, helpers at the nest increase breeders'' reproductive success, but chick provisioning is unevenly distributed among non-breeders, with a gradient that ranges from individuals that work as much as the breeders to others that completely refrain from visiting the nest. Here we show that lazy non-breeders represent an insurance workforce that fully compensates for a reduction in the provisioning effort of another group member, avoiding a decrease in reproductive success. When we temporarily impaired a carer, decreasing its nest attendance, the laziest non-breeders increased their provisioning rate and individuals that initially refrained from visiting the nest started helping. Breeders, in contrast, did not increase chick provisioning. This shows that lazy non-breeders can buffer a sudden unfavourable circumstance and suggests that group stability relies on the potential contribution of group members in addition to their current effort.