Exploring the intricacies of bryophyte reproduction:

Patterns of sexual and asexual reproduction were investigated in the lichen genus Parmotrema (Parmeliaceae). Most tropical species were found to produce either sexual or asexual reproductive structures, but not both. Temperate species were found to invest in mixed reproductive strategies. Mixed strategies may be selected for, not only because they maintain genetic variability, but also be- cause they may facilitate lichenization in habitats in which suitable algal-host diversity is low. Correlations were also observed between spore size, production of asexual structures and production of perforate apothecia in fertile species of Parmotrema that suggested a conservation of reproductive tissue in species in- vesting in large spores or asexual structures. Thus, there may be trade-offs in- volved in apportioning resources between growth, maintenance and reproduction in Parmotrema species from habitats that vary in environmental predictability. Lichen life history strategies are usually evaluated with regard to modes of reproduc- tion. Most lichens reproduce sexually by production of ascospores. Many lichen groups are also capable of reproducing asexually by production of specialized thallus fragments (isidia and soredia). Bowler and Rundel (1975) considered various modes of reproduction in the lichen order Lecanorales. From their investigations, they concluded that: (1) asexual groups are derived from sexual ancestors; (2) species rarely produce both sexual and asexual structures on the same thallus; and (3) species exhibiting asexual reproductive mechanisms generally exhibit a broader geographic distribution than sexual species. They suggested that the adaptive advantage of asexual strategies in lichens included increased survival of propagules and rapid invasion of new habitats. Williams (1975) made a number of predictions about the natural history characteristics of sexual and asexual species. A sexual strategy is expected when environmental condi- tions are unpredictable or selection is intense, or both. An asexual strategy is expected in predictable environments or when selection is less intense, or both. Since many organisms exhibit both sexual and asexual reproduction under various conditions during their-life histories, apportionment of resources- between the two mechanisms should reflect the degree to which production of genetically variable propagules by a sexual mechanism is successful. As Bowler and Rundel (1975) observed, lichen species seldom invest in both sexual and asexual mechanisms. They suggested that this reflected an energetic investment too costly to maintain with limited resources. However, in some lichen groups, fertile species also produce asexual structures. There has been no attempt to determine the adaptive advantage of mixed reproductive strategies in these lichen groups. Harper et al. (1970) predicted that seed plants exhibiting mixed (sexual and asexual) reproductive strategies would tend to be found in successional environments where the advantages of having both a high and a low intrinsic rate of increase outweigh the increased energetic cost. Joenje and During (1977) found that some colonizing moss species exhibit 007-2745/80/344-350$1.45/0

Multiple-scale environmental modulation of lichen reproduction

Reproductive strategy can play a significant role in invasion success and spread. Asexual and sexual reproduction may confer different advantages and disadvantages to a founding population, resulting in varying impacts on genetic diversity and the ability to invade. We investigate the role of reproductive mode in two species of non-native hydromedusae (Maeotias marginata and Moerisia sp.) in the San Francisco Estuary (SFE). Both species can reproduce asexually and sexually. We employed 7–8 microsatellite markers to determine overall genetic diversity and to investigate contributions of asexual and sexual reproduction to the populations. We found both species had high levels of genetic diversity (Average HE = 0.63 and 0.58, Number individuals sampled = 111 and 277, for M. marginata and Moerisia sp. respectively) but also detected multiple individuals in clonal lineages. We identified the same clones across sampling locations and time, and the index of asexual reproduction (R) was 0.89 for M. marginata and 0.91 for Moerisia sp. Our results suggest both species maintain high population genetic diversity through sexual reproduction, in combination with asexual reproduction, which allows rapid propagation. In addition, we conducted genetic sequence analyses at the ribosomal ITS1 marker, using samples of Moerisia sp. from the SFE and M. lyonsi from Chesapeake Bay. We found 100 % sequence similarity showing that Moerisia sp. in the SFE and Chesapeake Bay are the same species. The two hydromedusae studied here possess the means to propagate rapidly and have high genetic diversity, both of which may allow them to successfully adapt to changing environments and expand their invasions.

Meiosis I causes a high spontaneous mutation rate in a multicellular red alga (Pyropia yezoensis) with a complex life cycle

Populations of Allium vineale commonly include individuals with very different allocation patterns to three modes of reproduction: sexual flowers, aerially produced asexual bulbils, and belowground asexual offsets. If selection is currently acting to maintain these different allocation patterns there must be a genetic basis for variation in allocation to these three reproductive modes. In addition, negative genetic correlations between reproductive traits would imply evolutionary trade-offs among reproductive strategies. We evaluated the heritability of these allocation patterns by growing 16 clones from a single population in the greenhouse at two levels of fertilization. Bulb mass and the mass and number of bulbils, offsets, and flowers were used as response variables, in addition to the proportion allocated to each reproductive mode. We found evidence of substantial heritable variation in allocation to sexual reproduction and in allocation within the two modes of asexual reproduction, indicating high sensitivity of these allocation patterns to natural selection. We also found evidence of strong negative genetic correlations between bulbil and flower traits, as well as between bulbil and offset traits, with one group of genotypes allocating greater resources to aerial asexual bulbils and the second group allocating more resources to belowground asexual offsets and aerial flowers. Phenotypic plasticity in allocation to above- vs. belowground asexual reproduction and sexual vs. asexual aerial reproduction was limited, indicating that plants are unlikely to change reproductive mode in response to nutrient availability. Together, then, we have demonstrated strong heritability for, and trade-offs in, the reproductive allocation patterns within this plant population.

Abstract.Individuals of the recently described demospongeThoosa mismalolliare common on Mexican Pacific coral reefs, excavating burrows in living corals and in other calcareous substrata. To better understand the propagative abilities of this sponge, we conducted a histological study over an 18‐month period (May 2007–November 2008) to identify sexual and asexual reproductive structures. Members of the species are viviparous and hermaphroditic, with various developmental stages of oocytes, spermatic cysts, and embryos co‐occurring in the mesohyl for most of the year. This nearly continuous reproductive activity intensified during the warm season. Fertilization was internal, and embryos developed inside the parental sponge to produce an unciliated hoplitomella larva, characterized by a peculiar siliceous skeleton. In addition to the sexually generated larvae, adults ofT. mismalolliformed gemmules for asexual reproduction. Gemmules occurred within the mesohyl during all months of the year, but were most abundant in the coldest months. This combination of sexual and asexual processes enables individuals ofT. mismalollito reproduce almost continuously. This strategy may facilitate both long‐term persistence within reefs and effective dispersal between distant reefs.

Comparative analysis of the influence of arachidonic acid and its derivatives, 3-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic and 20-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic acids, on the formation of sexual and asexual reproductive structures in Neurospora crassa demonstrated that the presence and location of the hydroxyl group in unsaturated fatty acid determine the biological effect of the compound. In the presence of 5 μM of arachidonic acid, 20-HETE, and 3-HETE, vegetative spore formation in the light decreased by 45, 31, and 40%, respectively, indicating a similarity in the mechanisms of their action on the light-dependent asexual reproduction of the fungus. However, the effects of these compounds on the sexual process of N. crassa were radically different. Gas chromatography–mass spectrometry (GC–MS) revealed a fourfold increase in the monounsaturated oleic acid content in N. crassa cells after the addition of arachidonic acid. In the same time, the effect was not observed after the addition of 20-HETE. On the other hand, the increase in the linoleic acid content in the fungal mycelia was higher with 20-HETE.

<p>Understanding the evolutionary forces that shape populations in the marine environment is critical for predicting population dynamics and dispersal patterns for marine organisms. For organisms with complex reproductive strategies, this remains a challenge. Sponges fulfil many functional roles and are important components of benthic environments in tropical, temperate and polar oceans. They have evolved diverse reproductive strategies, reproducing both sexually and asexually, and thus provide an opportunity to investigate complicated evolutionary questions. This PhD thesis examines sexual and asexual reproduction in two common golf-ball sponges in central New Zealand (Tethya bergquistae and T. burtoni), with particular focus on how the environment influences these modes of reproduction, and further, how they shape species delineations and connectivity patterns. New Zealand waters are projected to experience increases in temperature and decreases in nutrients over the next century, and therefore these species may be experience changes in basic organismal processes like reproduction due to climate change, requiring adaptation to local environments. Therefore, this work has important implications when considering how reproductive phenology, genetic diversity and population structure of marine populations may change with shifts in climate. In my first data chapter, I highlight the difficulty in delineating sponge species by investigating the evolutionary relationship of Tethya spp. in central New Zealand using both morphological and molecular methods. Phylogenetic reconstructions based on two mitochondrial markers (rnl, COI-ext) and one nuclear marker (18S) revealed three genetic clades, with one clade representing T. bergquistae and two clades belonging to what was a priori thought to be a single species, T. burtoni. Morphological analysis based on spicule characteristics allowed T. bergquistae to be distinguished from T. burtoni, but revealed no apparent differences between the T. burtoni clades. These results indicate hidden genetic diversity within T. burtoni, which likely represents a group consisting of incipient species that have undergone speciation but have yet to express clear morphological differences. This chapter supports the notion that cryptic speciation in sponges may go undetected and diversity underestimated when using only morphology-based taxonomy, a result which has implications for conservation and management of marine systems. In my second data chapter, I characterize the reproductive biology for both species of Tethya in relation to potential environmental drivers, including sea surface temperature, chlorophyll-a concentration and rainfall. Using histological methods for sponges collected monthly over two years, Tethya spp. were found to be gonochoristic and oviparous sexual reproducers, with one annual reproductive event occurring in the austral summer from January to March. Differences in oocyte density and reproductive output between both species and sites highlighted both species-specific adaptive responses and environmental influences on reproduction. Temperature and rainfall were found to be correlated with instances of sexual reproduction, and the summer reproductive event occurred each year following the spring bloom of chlorophyll-a. These findings indicate that seasonal fluctuations in the environment may be important for triggering gametogenesis for these species. With shifts in temperature, productivity, and timing of seasons projected for New Zealand, there is a potential for reproductive phenology to become mismatched with the surrounding environment under future climate change scenarios, which has consequences for the frequency, duration and overall output of sexual reproduction for these sponges. My third data chapter characterizes asexual reproduction in both species of Tethya, exploring relationships between reproductive traits and potential environmental drivers that may influence asexual budding events. Two sponge populations, one for each species of Tethya, were monitored over two years by both monthly sampling and periodic in situ observations. Data revealed that budding occurred continuously throughout the year, but had a cyclic pattern where instances of budding and densities of buds were higher during the austral spring and summer. Asexual reproduction coincided with sexual reproduction, and some individuals were found to simultaneously reproduce using both modes. Instances of asexual reproduction were positively associated with temperature and rainfall, but distinct differences between species were difficult to identify. As temperature proved important, an experiment looking at bud production in relation to thermal stress was conducted, where sponges were subjected to stable temperatures treatments of 17°C (control), 19°C and 21°C. No instances of budding were observed under any temperature treatment, and high mortality occurred in the 21°C treatment. These results suggest that temperature changes (i.e., heterogeneous environments) may be more important than temperature alone in driving asexual reproduction, and further, indicate thermal stress will result in increased sponge mortality. Correlations to potential environmental drivers indicate that future shifts in climate may affect instances of asexual reproduction and thus sponge abundance, which has the potential to alter the genetic structure and overall diversity of these populations. In the final data chapter, I developed novel microsatellite markers for Tethya burtoni to characterize the genetic connectivity patterns among four populations in central New Zealand, with particular interest in the roles that sexual and asexual reproduction play in connectivity. I sampled three sites within 10 km of each other in the Wellington Region (WR), and another site on an island (Kapiti Island) approximately 50 km north of the WR. At one of the WR sample sites, I monitored a T. burtoni population over two years to examine the dispersal range of asexually reproduced buds and the ability of clones to sexually reproduce. The WR and Kapiti Island populations were strongly genetically differentiated, but within the WR region, two populations were genetically similar, indicative of high connectivity. For the monitored population, asexual bud dispersal was restricted to no greater than 1 m and clonal individuals had reduced sexual reproductive ability. Asexual reproduction did not appear to play an important role in interpopulation connectivity nor gene flow, as buds had low dispersal ability and rarely reproduced. Population structure and connectivity for T. burtoni appear to be largely driven by sexual reproduction, and asexual reproduction instead aids genotype survivorship and population maintenance. These findings highlight that different reproductive modes can differentially contribute to population dynamics in sessile marine organisms, suggesting that predictions about future population viability under changing environments may be difficult to make. In summary, this PhD thesis uses a combination of genetic, histological, field-based and experimental methods to examine species boundaries, reproduction and connectivity for Tethya spp. on rocky reefs of New Zealand. The sympatric nature, complex reproductive ecology and connectivity patterns observed likely shape the complex evolutionary processes occurring in these sponges, including introgressive hybridization and cryptic species. Individuals that showed evidence of possible introgressive events occurred mainly in populations with more restricted gene flow, while the presence of both cryptic species were more prevalent in well connected populations. Such a trend allows for discussion of under what circumstances both of these processes occur. Furthermore, environmental correlates to both sexual and asexual reproduction indicate that both of these modes of reproduction have the potential to be altered with future changes in the environment. As both modes were found to play different roles in gene flow within and between populations, future shifts in climate are also expected to alter population structure and connectivity for these sponges. Such shifts in gene flow will also likely result in changes to species boundaries and thus the overall diversity of this genus. Many other sessile, benthic marine organisms present reproductive traits and behaviours similar to those of Tethya spp., and therefore these results can aid in the interpretation of results for other marine taxa. Overall, this thesis describes the population dynamics of Tethya spp., which are abundant and ecologically important on New Zealand reefs, and provides insight on how temperate sponge populations may fare with climate change, which has important implications for management and conservation efforts.</p>

Under the conditions of nitrogen starvation, illumination by blue light of wc-1 and wc-2 mutants of the ascomycete Neurospora crassa failed to stimulate the formation of protoperithecia and inhibit conidiation (contrary to what was observed in the mycelium of the wild-type fungus). The data obtained indicate that wc-1 and wc-2 genes of N. crassa are involved in light-dependent formation of protoperithecia and conidia. The effects of 5-azacytidine (an inhibitor of DNA methylation) under the same experimental conditions suggest that the balance between the formation of sexual and asexual reproductive structures, maintained in N. crassa, depends on genome methylation processes sensitive to the action of light, which is mediated by the photoreceptor complex of WC proteins.

Does reproductive assurance explain the incidence of polyploidy in plants and animals?

Chapter Four - Life cycles and reproduction of Rhizostomeae

温度和食物水平对海月水母螅状体无性繁殖的影响

Harpellales - The Harpellaceae and Legeriomycetaceae, commonly referred to as “harpellids,” have similar asexual and sexual reproductive structures and life cycles (Fig. 7.1). In the unbranched Harpellaceae, asexual reproduction commences after the maximum but limited number of cells has been produced. Each compartment becomes a generative cell, giving rise exogenously to an appendaged trichospore. In the branched Legeriomycetaceae, only the terminal parts of branches normally become fertile, and vegetative growth and sporulation may continue as trichospores are maturing on older branches of the thallus.

Competitive Exclusion and Coexistence of Species with Complex Life Cycles

Genetic diversity among biological entities, including populations, species, and communities, serves as a fundamental source of information for understanding their structure and functioning. However, many ecological and evolutionary problems arise from limited and complex datasets, complicating traditional analytical approaches. In this context, our study applies a deep learning-based approach to address a crucial question in evolutionary biology: the balance between sexual and asexual reproduction. Sexual reproduction often disrupts advantageous gene combinations favored by selection, whereas asexual reproduction allows faster proliferation without the need for males, effectively maintaining beneficial genotypes. This research focuses on exploring the coexistence patterns of sexual and asexual reproduction within a single species. We developed a convolutional neural network model specifically designed to analyze the dynamics of populations exhibiting mixed reproductive strategies within changing environments. The model developed here allows one to estimate the ratio of population members who originate from sexual reproduction to the clonal organisms produced by parthenogenetic females. This model assumes the reproductive ratio remains constant over time in populations with dual reproductive strategies and stable population sizes. The approach proposed is suitable for neutral multiallelic marker traits such as microsatellite repeats. Our results demonstrate that the model estimates the ratio of reproductive modes with an accuracy as high as 0.99, effectively handling the complexities posed by small sample sizes. When the training dataset’s dimensionality aligns with the actual data, the model converges to the minimum error much faster, highlighting the significance of dataset design in predictive performance. This work contributes to the understanding of reproductive strategy dynamics in evolutionary biology, showcasing the potential of deep learning to enhance genetic data analysis. Our findings pave the way for future research examining the nuances of genetic diversity and reproductive modes in fluctuating ecological contexts, emphasizing the importance of advanced computational methods in evolutionary studies.