Variation In Reproduction Research Articles

Complex Spatial Genetic Connectivity of Mussels Mytilus chilensis Along the Southeastern Pacific Coast and Its Importance for Resource Management

To ensure the maintenance of natural mussel beds along the southeastern Pacific coast of Chile, it is important to understand their population dynamics. This means evaluating their genetic population structure and gene flow, and the degree of connectivity among natural beds. To do this, the spatial genetic population structure of seven natural Mytilus chilensis beds within the mussels' present distribution range along the Chilean coast was evaluated. Genetic differences were established between populations with cytochrome oxidase I (COI) gene sequences (Fst = 0.099) and microsatellites (Fst = 0.048), showing that locations that consistently presented greater differentiation were those at the extremes of the geographical distribution. An “isolation by distance” pattern was not observed in the COI and microsatellite data. We suggest that because of the high resolution of these markers, the differences between locations may be explained by high reproductive variance, which determines local changes in each reproductive cycle of the species. These changes would account for the differences between the natural beds. Furthermore, differentiated genetic types were observed in some locations, demonstrating the presence of local processes in some cases, perhaps caused by gene flow restrictions resulting from the local geomorphological and oceanographic conditions. The gene structure and connectivity of natural beds in sessile species with larval dispersion are strongly determined by local retention characteristics. For this reason, the data generated in this study can be used to improve population management. These data can also be used to support and motivate the creation of a marine protected area containing natural beds of this species with sufficient levels of genetic diversity.

Reproductive plasticity in the invasive -Xenostrobus securis (Bivalvia: Mytiloidea) in northwestern Spain

The invasive mussel Xenostrobus securis was first recorded from Galicia (NW Spain) in 2007, within an area characterized by the commercial culture of Mytilus galloprovincialis. This study investigated the spatial variability in reproduction of X. securis at three adjacent locations over a period of twelve months and the temporal variation at one location over two consecutive years. This is the first such study conducted outside its native range and in which the influences of temperature and salinity on the reproductive cycle were also tested. The invader exhibited rapid gametogenesis, accumulation of mature gametes and an extended spawning period interspersed with gonad recovery, without resting periods. The onset of gametogenesis varied both spatial and temporally, starting 15-days later at the innermost location than at the outermost one. Such spatial variability resulted in an almost continuous breeding season (10 months), in contrast to the 7–8 months observed in the native range. Although the spatial variability in maturation and spawning in the native location is mainly attributable to variations in salinity, the variability in the Ría de Vigo was probably caused by temperature acting as a trigger for maturation and spawning. The almost continuous breeding season exhibited by X. securis potentially results in planktotrophic larvae being present in the water column for almost 10 months of the year. The reproductive plasticity of X. securis and the potential to adapt to local environmental conditions highlight the need for specific monitoring programmes focused on early detection in potential invasion hotspots.

Occurrence of Apomixis in Eleusine coracana

Eighteen different accessions of Eleusine coracana were subjected to detailed morphological analysis of female reproductive parts along with the phasic embryological analysis of the pathways for the formation of female gametophyte for evaluating the reproductive diversity and strategy. In this investigation all the accession possessed Polygonum type of sexual embryo sac. But a few accessions were also showing the formation of Panicum type of aposporic embryo sacs in addition to sexual embryo sac, signifying the presence of facultative apomixis. The aposporic embryo sac initials for the formation of Panicum type of embryo sac differentiated in nucellus. The aposporic embryo sac initial enlarged greatly. Vacuolization soon started because of which the young embryo sac took up unipolar organization with a prominent nucleus at one pole. This nucleus divided mitotically into two which subsequently divided to produce four nuclei, occupying only one pole of the embryo sac. The four nuclei organized into a Panicum type embryo sac having an egg, two synergids and a polar nucleus. Apomixis is an asexual method of propagation through seed in which both meiosis and fertilization are bypassed for the development of an embryo. It is a fascinating method to produce large genetically uniform populations of crop species in which heterozygosity and hybrid vigour can be maintained in successive seed generations.

Reproduction Diversity of female local buffalo on the condition of smallholder farms in the eastern Seunagan sub-district of Nagan Raya district

The purpose of this study was to identify the female buffalo reproductive characteristics in eastern Seunagan sub-district of Nagan Raya district. This research used survey method in five villages within eastern Seunagan sub-district, namely: Lhok Pange, Sawang Manee, Tuwi Meuleusong and Blang Gedong. Fourty respondents of buffalo breeders were selected based on purposive sampling methods, with the minimum requirement of the breeders having experience more than one year and keeping two productive buffalos which had given birth twice. Data collection was done by interview and discussion techniques. The parameters observed were: (a) the age of the first mated; (b) the age of having the first calf; (c) calving interval and (d) the weaning period. The data obtained were processed and the average was calculated and then descended and described descriptively. The results showed that the reproduction characteristics of female buffalo in the eastern Seunagan sub-district of Nagan Raya district were good enough. The age of the first mated was at 39 months, while the age of having the first calf was at 53.4 months with calving interval 20.47 months and the weaning periods was 14.67 months. Extensive livestock raising systems were 90%, with only 10% of farmers raising semi-intensive livestock.

Investigating the relationship between climate, stand age, and temporal trends in masting behavior of European forest trees.

Masting—temporally variable seed production with high spatial synchrony—is a pervasive strategy in wind‐pollinated trees that is hypothesized to be vulnerable to climate change due to its correlation with variability in abiotic conditions. Recent work suggests that aging may also have strong effects on seed production patterns of trees, but this potential confounding factor has not been considered in previous times series analysis of climate change effects. Using a 54 year dataset for seven dominant species in 17 forests across Poland, we used the proportion of seed‐producing trees (PST) to contrast the predictions of the climate change and aging hypotheses in Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus petraea, and Quercus robur. Our results show that in all species, PST increased over time and that this change correlated most strongly with stand age, while the standardized precipitation–evapotranspiration index, a measure of drought, contributed to temporal trends in PST of F. sylvatica and Q. robur. Temporal variability of PST also increased over time in all species except P. sylvestris, while trends in temporal autocorrelation and among‐stand synchrony reflect species‐specific masting strategies. Our results suggest a pivotal role of plant ontogeny in driving not only the extent but also variability and synchrony of reproduction in temperate forest trees. In a time of increasing forest regrowth in Europe, we therefore call for increased attention to demographic effects such as aging on plant reproductive behavior, particularly in studies examining global change effects using long‐term time series data.

STOREFISH 2.0: a database on the reproductive strategies of teleost fishes.

Teleost fishes show the most outstanding reproductive diversity of all vertebrates. Yet to date, no one has been able to decisively explain this striking variability nor to perform large-scale phylogenetic analyses of reproductive modes. Here, we describe STrategies Of REproduction in FISH (STOREFISH) 2.0, an online database easing the sharing of an original data set on reproduction published in 2007, enriched with automated data extraction and presentation to display the knowledge acquired on temperate freshwater fish species. STOREFISH 2.0 contains the information for 80 freshwater fish species and 50 traits from the analysis of 1219 references. It is anticipated that this new database could be useful for freshwater biodiversity research, conservation, assessment and management. Database URL: www.storefish.org

Estrategias para la conservación de Zamia furfuracea L. f. (Zamiaceae, Cycadales): una especie “En Peligro” de extinción con un amplio potencial de uso.

Zamia furfuracea es una planta endémica del estado de Veracruz, que posee un gran valor ornamental y un alto potencial de uso. Se encuentra catalogada como una especie “En Peligro” de extinción, debido a que en las últimas cuatro décadas, fueron extraídas plantas, semillas e incluso individuos adultos de sus poblaciones naturales de forma ilegal, reduciéndolas hasta en un 40%. Por tal motivo, se desarrolló el presente trabajo con el objetivo de establecer un enfoque integral para su manejo y conservación, tanto a nivel local como regional. Para ello se identificaron y evaluaron diversos índices de fragmentación que están incidiendo en sus poblaciones y se realizaron estudios sobre su biología reproductiva, demografía y diversidad genética. Se encontró que aunque todas las poblaciones se encuentran afectadas por diferentes agentes de perturbación, todos ellos han estado afectando la viabilidad y germinación de las semillas así como la supervivencia de los individuos juveniles. Con base a los resultados obtenidos se proponen diferentes estrategias de conservación para cada una de las poblaciones estudiadas y aunque se concluye que la conservación ex situ es la mejor alternativa para la conservación de la especie, no se descarta la conveniencia de implementar acciones para su conservación y manejo in situ.

Genetic diversity and reproductive biology of the dioecious and epiphytic bromeliad Aechmea mariae-reginae (Bromeliaceae) in Costa Rica: implications for its conservation

AbstractEcological traits and pollination mode associated with dioecious sexual expression in plants are likely to influence their reproductive success and levels of genetic diversity. Dioecy is an uncommon condition in Bromeliaceae. Currently, there is limited information on the reproductive ecology and genetics of dioecious and epiphytic bromeliads. Therefore, we studied the reproductive biology and genetic diversity of the epiphytic and dioecious bromeliad Aechmea mariae-reginae in Costa Rica. Flowering of pistillate and staminate plants in one population showed high synchrony and were pollinated by non-hermit hummingbirds. Sex ratio was biased to males (3.5:1). Fruit set was relatively high (68%) but there was high female reproductive variance (C. V. = 59.7%). The species is capable of parthenocarpic fruit production. Using eight nuclear microsatellite markers and six populations, we found moderate to high levels of genetic variation (HE = 0.571–0.726). Populations showed significant genetic structure (G'ST = 0.385) and Bayesian population assignment grouped them into lowland and montane clusters. Isolated montane populations had slightly lower genetic diversity probably due to lower effective population size caused by biased sex ratios and recent habitat fragmentation that limits long-distance pollinator movements and results in isolation by distance. If habitat fragmentation and isolation persist, populations in montane habitats may be at higher risk of decline and extinction.

Rethinking power, production, and social reproduction: Toward variegated social reproduction

This special issue introduces new work, new perspectives, and engages in a dialogue to revisit, extend and go beyond the original central hypothesis of Power, Production and Social Reproduction (2003). That volume and its primary hypothesis focused upon the unfolding contradiction between the global accumulation of capital and the provision of stable and progressive conditions of social reproduction. It hypothesized a growing contradiction between the intensified power of capital and many life-making/sustaining processes, including the condition of bodies and the biosphere. Our original hypothesis conceptualized capital accumulation and social reproduction as interlinked although within different and contradictory moments in the same system or totality. We add to this here the concept of variegated social reproduction which refers to the historical and ontological variability of social reproduction - and its specific differentiations and varieties in contemporary globalized capitalism - stemming from concrete social, cultural, ecological and material practices and structures. Indeed, as the articles in the special issue reflect, the neoliberalization and commodification of social reproduction remains incomplete and not all-encompassing or determinant. As such, the introduction and the special issue also suggest new research agendas.

Sperm competition and the evolution of sperm form and function in mammals.

Sperm competition is a powerful selective force that has influenced many reproductive traits in males and females although additional evolutionary explanations may help to understand the diversity of mammalian reproduction. Sperm morphology varies considerably in mammals with extreme examples in several rodent lineages in which a wide range of sizes and complex head morphologies have been identified. Mammalian spermatozoa also differ in function, with swimming velocity and trajectory showing much divergence. Underlying processes mediating function have received little attention so far, but differences in timing and proportion of sperm undergoing capacitation or acrosomal exocytosis may be related to variation in signalling processes. Furthermore, energy required for sperm functions (such as motion, signalling and overall maintenance of cell integrity) can be produced and consumed, following different patterns among species and this could be the result of several selective forces. A more thorough understanding of the diversity in structure and function of sperm cells, and underlying selective forces, may help us develop better methods to assess them taking into account particulars and generalities of sperm form and performance. Such tests could then become more reliable in estimations of the impact of cryopreservation or effect of changes in the environment and their relevance for fertility.

Climate change, range shifts, and the disruption of a pollinator-plant complex

Climate change has significant impacts on the distribution of species and alters ecological processes that result from species interactions. There is concern that such distribution shifts will affect animal-plant pollination networks. We modelled the potential future (2050 and 2070) distribution of an endangered migratory bat species (Leptonycteris nivalis) and the plants they pollinate (Agave spp) during their annual migration from central Mexico to the southern United States. Our models show that the overlap between the Agave and the endangered pollinating bat will be reduced by at least 75%. The reduction of suitable areas for Agave species will restrict the foraging resources available for the endangered bat, threatening the survival of its populations and the maintenance of their pollination service. The potential extinction of the bat L. nivalis will likely have negative effects on the sexual reproduction and genetic variability of Agave plants increasing their vulnerability to future environmental changes.

A statistical inference in an epidemic model with combinational drug treatment: HIV as a case study

Stochastic models are the systems of stochastic differential equations (SDEs) that account the variability in cellular reproduction and death, the infection process, viral reproduction and the immune response against the infection. Generally, the stochastic models are derived based on the dynamics of deterministic models and they provide new insights, distinct from the basic deterministic models. In several years, few mathematical models have described the immunological survival against epidemiological diseases, like HIV. But complete cure to such diseases is still a problem to our human society. Here, we construct a three-compartmental system based on the HIV dynamics and apply the stochastic approach to the deterministic version of our mathematical model. The key feature of this research is to capture the probable time to extinction of infected cells by promoting antiretroviral treatment as well as in vitro monocyte-derived dendritic cell (moDC) vaccination in the population. We introduce the hypothesized transition rates for the stochastic model and the quasi stationary distribution of the infected immune cells. The aim of the analysis of this model is to identify the effect of such combinational drug treatments, to count the unsuccessful invasion of virus during the course of drug treatment and predict the time for complete extinction of the disease.

Evolutionary drivers of group foraging: A new framework for investigating variance in food intake and reproduction.

A proposed fundamental driver of group living is more reliable, predictable foraging and reproduction, i.e., reduced variance in food intake and reproductive output. However, existing theories on variance reduction in group foraging are simplistic, refer to variance at the level of individuals and groups without linking the two, and do not spell out crucial underlying assumptions. We provide a new, widely applicable framework for identifying when variance reduction conveys fitness benefits of group foraging in a wide range of organisms. We discuss critical limitations of established theories, the Central Limit Theorem and Risk-Sensitive Foraging Theory applied to group foraging, and incorporate them into our framework while addressing the confusion over the levels of variance and identifying previously unaddressed assumptions. Through a field study on colonial spiders, Cyrtophora citricola, we demonstrate the importance of evaluating the level of food sharing as a critical first step, previously overlooked in the literature. We conclude that variance reduction provides selective advantages only under narrow conditions and does not provide a universal benefit to group foraging as previously proposed. Our framework provides an important tool for identifying evolutionary drivers of group foraging and understanding the role of fitness variance in the evolution of group living.

Temporal reproduction within and across senses: Testing the supramodal property of the pacemaker-counter model.

The human ability to compare time between sensory modalities implies a supramodal representation of time. This notion is consistent with the pacemaker-counter model (PCM), the core architecture of prominent timing theories. Some theorists, however, have promoted modality-specific timing mechanisms, which might hamper crossmodal temporal comparison. This study tested whether PCM is sufficient to account for intra- as well as crossmodal timing. To account for modality-specific timing differences, we proceeded from the common assumption that the pacemaker runs faster for auditory than for visual stimuli. Participants reproduced short and long standards (800 vs. 2,400 ms) by terminating a comparison stimulus. In Experiment 1, in each trial the sensory modalities (auditory vs. visual) of the standard and the comparison were the same (congruent) or different (incongruent). PCM implies that timing performance depends on modality order. However, there should be virtually no congruency effects on overall performance. Although the results largely matched the predictions of PCM, there were substantial congruency effects on reproduction variability especially in the subsecond range. Three intramodal control experiments, however, showed that similar congruency effects can be observed when the standard and the comparison differ in intramodal characteristics. This suggests that temporal representations are not isolated from nontemporal stimulus characteristics, even when these are subtle and within the same modality. The present results can be interpreted as evidence for sensory timing within the subsecond range. Nevertheless, we used computer simulations to evaluate extensions of PCM that could account for the present result pattern, while retaining PCM's supramodal property. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Environmental Veto Synchronizes Mast Seeding in Four Contrasting Tree Species.

Synchronized and variable reproduction by perennial plants, called mast seeding, is a major reproductive strategy of trees. The need to accumulate sufficient resources after depletion following fruiting (resource budget), the efficiency of mass flowering for outcross pollination (pollen coupling), or the external factors preventing reproduction (environmental veto) could all synchronize masting. We used seed production data for four species (Quercus ilex, Quercus humilis, Sorbus aucuparia, and Pinus albicaulis) to parametrize resource budget models of masting. Based on species life-history characteristics, we hypothesized that pollen coupling should synchronize reproduction in S. aucuparia and P. albicaulis, while in Q. ilex and Q. humilis, environmental veto should be a major factor. Pollen coupling was stronger in S. aucuparia and P. albicaulis than in oaks, while veto was more frequent in the latter. Yet in all species, costs of reproduction were too small to impose a replenishment period. A synchronous environmental veto, in the presence of environmental stochasticity, was sufficient to produce observed variability and synchrony in reproduction. In the past, vetoes like frost events that prevent reproduction have been perceived as negative for plants. In fact, they could be selectively favored as a way to create mast seeding.

Age-related changes in time production and reproduction tasks: Involvement of attention and working memory processes

ABSTRACT Several studies have reported age-related differences in time estimation, which have been attributed either to a slowing of the pacemaker rate with aging or to impaired attention and/or working resources in older adults. Here, we compared performance of young and older participants on time production/reproduction tasks and on working memory, divided attention, sustained attention and executive attention tasks. Results showed that relative to young participants, older adults significantly under-reproduced and tended to over-produce target durations. Neither attention nor working memory predicted time reproduction and production performance. Conversely, when temporal variability was considered, participants’ temporal variability in time production tasks was exclusively accounted for by age, whereas variability in temporal reproduction was also explained by divided attention and working memory. Overall, our results extend previous investigations on timing abilities in the elderly and underscore the importance of divided attention and working memory in the maintenance of a stable representation of durations.

Ecological, genetic, and reproductive features of Cenchrus species indicate evolutionary superiority of apomixis under environmental stresses

Many Cenchrus species are resilient to harsh environmental conditions and reproduce through apomixis (asexual seed production), and the resulting progeny is genetically identical to the mother plant. Although the apomictic mode of reproduction restricts the efforts of plant breeders to pyramiding desirable traits, it facilitates the fixation of genetic combinations over multiple generations. Eight Cenchrus species are found in India of which only four apomictic species are grown in sown pastures. We assessed the variability in the morphological, behavioral, ecological, reproductive, genetic and molecular features among the different Cenchrus species, and envisaged a relationship between apomixis and stress tolerance for survival and species propagation under unfavorable ecological conditions. Our findings revealed considerable variability among the Cenchrus species. Molecular diversity analysis grouped the Cenchrus species into two distinct clusters. The apomictic species exhibited a lower diversity than the sexual species. Reproductive pathway diversity (BII and BIII seed formation) among the apomictic Cenchrus species indicated segregation of the components of apomixis, namely parthenogenesis, apomeiosis and functional endosperm formation. For the first time we report partitioning of the components of apomixis in C. glaucus. The earlier reported correlation between apomixis and polyploidy was not observed in the genus Cenchrus. Apomictic Cenchrus species are usually perennial, highly productive and invasive, and adapted to yearly fluctuations in the weather. Sexual Cenchrus species are usually annual, relatively less productive and do not survive during winter. Therefore, we concluded that apomixis facilitates the expansion of species by enabling reproduction even under stressful conditions. The information on genetic and reproductive diversity among the Cenchrus species presented in this study might be useful for interspecific hybridization among these species, as well as to decipher the molecular basis of apomixis in plants.

A new biological species in the Mercurialis annua polyploid complex: functional divergence in inflorescence morphology and hybrid sterility.

Background and AimsPolyploidy has played a major role in the origin of new plant species, probably because of the expansion of polyploid populations in the species’ ecological niche, and because reproductive isolation can be established between a new polyploid population and its diploid progenitor species. It is well established that most polyploid species are polyphyletic, with multiple independent origins, and that polyploid genomes may undergo rapid change after their duplication and hybridization associated with their origin. We considered whether multiple independent origins and rapid genomic change might lead to reproductive isolation between polyploid populations of the same ploidy but with potentially different evolutionary histories.MethodsWe tested our hypothesis by assessing differences in DNA content and morphology, the evolution of reproductive isolation, and the phylogenetic placement of two broadly sympatric hexaploid lineages of the wind-pollinated annual plant Mercurialis annua hitherto regarded as populations of the same species.Key ResultsThe two hexaploid lineages of M. annua have slightly divergent DNA content, and distinct inflorescence morphology. They also fall into largely different clades of a chloroplast phylogeny and are reproductively isolated from one another.ConclusionsThe distinct evolutionary histories of the two hexaploid lineages of M. annua have contributed to the remarkable reproductive diversity of the species complex. It seems likely that reproductive interference between them will eventually lead to the displacement of one lineage by the other via pollen swamping. Thus, whereas polyploidization can contribute to speciation, diversification might also be compromised by reproductive interference.

Evolutionary drivers of kype size in Atlantic salmon (Salmo salar): domestication, age and genetics.

The diversity of reproduction and associated mating patterns in Atlantic salmon (Salmo salar) has long captivated evolutionary biologists. Salmo salar exhibit strategies involving migration, bold mating behaviours and radical morphological and physiological change. One such radical change is the elongation and curvature of the lower jaw in sexually mature males into a hook-like appendage called the kype. The kype is a secondary sexual characteristic used in mating hierarchies and a prime candidate for sexual selection. As one of the core global aquaculture fish species, however, mate choice, and thus sexual selection, has been replaced by industrial artificial fertilization seeking to develop more commercially viable strains. Removal of mate choice provides a unique opportunity to examine the kype over successive generations in the absence of sexual selection. Here we use a large-scale common-garden experiment, incorporating six experimental strains (wild, farmed and wild × farmed hybrids), experiencing one to three sea winters, to assess the impact of age and genetic background. After controlling for allometry, fork length-adjusted kype height (AKH) was significantly reduced in the domesticated strain in comparison to two wild strains. Furthermore, genetic variation at a locus on linkage group SSA1 was associated with kype height, and a locus on linkage group SSA23 was associated with fork length-adjusted kype length (AKL). The reduction in fork length-AKH in domesticated salmon suggests that the kype is of importance in mate choice and that it has decreased due to relaxation of sexual selection. Fork length-AKL showed an increase in domesticated individuals, highlighting that it may not be an important cue in mate choice. These results give us insight into the evolutionary significance of the kype, as well as implications of genetic induced phenotypic change caused by domesticated individuals escaping into the natural environment.

Isolation and Characterization of Interspersed Repeated Sequences in the Common Lizard, Zootoca vivipara, and Their Conservation in Squamata

The common lizard (Zootoca vivipara) displays characteristic cytogenetic, reproductive, molecular, and biogeographic variability. This species comprises oviparous and viviparous populations with disjunct distribution and sex chromosome polymorphisms, from simple ZZ/ZW to complex Z₁Z₁Z₂Z₂/Z₁Z₂W systems with different morphologies of the W chromosome. In this study, we used the primers SINE A and SINE B and a newly designed primer pair to (1) obtain information on the presence and distribution of transposable elements (TEs) in 8 squamate families and (2) assess the chromosomal location of SINE Squam elements in Z. vivipara. PCR amplification with SINE A and SINE B produced single or multiple products in different Z. vivipara populations, subsequently used to design the SINE-Zv primers. Using the newly designed SINE-Zv primers, we identified 2 sequences of about 700 and 300 bp (SINE-Zv 700 and SINE-Zv 300) in all the investigated populations of Z. vivipara. Fluorescence in situ hybridizations showed a preferential localization of SINE-Zv sequences in the peritelomeric regions of almost all chromosomes, with the exception of the W. Both sequences contained a distinct segment of SINE Squam2. SINE-Zv 700 appeared to be restricted to Z. vivipara, while SINE-Zv 300 contained a partial Gypsy sequence that is highly conserved among Squamata and showed high identity values (72-93%) with several transcripts from different species. Using the same primers, we also highlighted the presence of another highly conserved Gypsy-like fragment in snakes which displayed significant similarity with the stomatin-like protein 2 of colubrids. Our results suggest that SINEs and the Gypsy-like elements are widely distributed among squamates and may have played an active role in their genomic evolution and differentiation.