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Leeches and oligochaetes comprise a monophyletic group of annelids, the Clitellata, whose reproduction is characterized by simultaneous hermaphroditism. While most clitellate species reproduce by cross-fertilization, self-fertilization has been described within the speciose genus Helobdella. Here we document the reproductive life histories and reproductive capacities for three other Helobdella species. Under laboratory conditions, both H. robusta and H. octatestisaca exhibit uniparental reproduction, apparently reflecting self-fertility, and suggesting that this trait is ancestral for the genus. However, the third species, H. austinensis, seems incapable of reproduction by self-fertilization, so we inferred its reproductive life history by analyzing reproduction in breeding cohorts. Comparing the reproductive parameters for H. robusta reproducing in isolation and in cohorts revealed that reproduction in cohorts is dramatically delayed with respect to that of isolated individuals, and that cohorts of leeches coordinate their cocoon deposition in a manner that is not predicted from the reproductive parameters of individuals reproducing in isolation. Finally, our comparisons of reproductive capacity for individuals versus cohorts for H. robusta, and between different sizes of cohorts for H. austinensis, reveal differences in resource allocation between male and female reproductive roles that are consistent with evolutionary theory.

To date, the molecular mechanisms of the unique gonadal development mode known as protandric simultaneous hermaphroditism (PSH) are unclear in crustaceans. In this study, cDNA of a gonad-inhibiting hormone (Lv-GIH1) was isolated from the PSH peppermint shrimp Lysmata vittata, and its expression was exclusively found in the eyestalk ganglion. Real-time quantitative polymerase chain reaction (qRT-PCR) revealed that the expression of Lv-GIH1 increased during gonadal development of the functional male stages but decreased significantly at subsequent simultaneous hermaphroditism stage. Further in vitro experiment showed that recombinant GIH1 protein (rGIH1) effectively inhibited Vg expression in the cultured hepatopancreas tissues while the short-term injection of GIH1-dsRNA resulted in reduced expression of Lv-GIH1 and upregulated expression of Vg in the hepatopancreas. Moreover, long-term rGIH1 injection led to significantly reduced expression of Lv-Vg, Lv-VgR, and Lv-CFSH1, subdued growth of oocytes, and feathery setae as a secondary sexual characteristic in females. Interestingly, while germ cells in testicular part were suppressed by rGIH1 injection, the expression of Lv-IAGs showed no significant difference; and long-term GIH1-dsRNA injection results were contrary to those of rGIH1 injection. Taken together, the results of this study indicate that Lv-GIH1 is involved in gonadal development and might also participate in controlling secondary sexual characteristic development in L. vittata by inhibiting Lv-CFSH1 expression. Summary sentence The gonad-inhibiting hormone (Lv-GIH1) gene isolated from the PSH peppermint shrimp (Lysmata vittata) was not only involved in gonadal development and might also participate in controlling secondary sexual characteristic development by inhibiting Lv-CFSH1 expression.

The great pond snail Lymnaea stagnalis has served as a model organism for over a century in diverse disciplines such as neurophysiology, evolution, ecotoxicology and developmental biology. To support both established uses and newly emerging research interests we have performed whole genome sequencing (avg.176 × depth), assembly and annotation of a single individual derived from an inbred line. These efforts resulted in a final assembly of 943 Mb (L50 = 257; N50 = 957,215) with a total of 22,499 predicted gene models. The mitogenome was found to be 13,834 bp long and similarly organized as in other lymnaeid species, with minor differences in location of tRNA genes. As a first step towards understanding the hermaphroditic reproductive biology of L. stagnalis , we identified molecular receptors, specifically nuclear receptors (including newly discovered 2xDNA binding domain-NRs), G protein-coupled receptors, and receptor tyrosine kinases, that may be involved in the cellular specification and maintenance of simultaneously active male and female reproductive systems. A phylogenetic analysis of one particular family of GPCRs (Rhodopsin neuropeptide FMRFamide-receptor-like genes) shows a remarkable expansion that coincides with the occurrence of simultaneous hermaphroditism in the Euthyneura gastropods. As some GPCRs and NRs also showed qualitative differences in expression in female (albumen gland) and male (prostate gland) organs, it is possible that separate regulation of male and female reproductive processes may in part have been enabled by an increased abundance of receptors in the transition from a separate-sexed state to a hermaphroditic condition. These findings will support efforts to pair receptors with their activating ligands, and more generally stimulate deeper insight into the mechanisms that underlie the modes of action of compounds involved in neuroendocrine regulation of reproduction, induced toxicity, and development in L. stagnalis , and molluscs in general.

It remains a major challenge to identify the genes and mutations that lead to plant sexual differentiation. Here, we study the structure and evolution of the sex-determining region (SDR) in Vitis species. We report an improved, chromosome-scale Cabernet Sauvignon genome sequence and the phased assembly of nine wild and cultivated grape genomes. By resolving twenty Vitis SDR haplotypes, we compare male, female, and hermaphrodite haplotype structures and identify sex-linked regions. Coupled with gene expression data, we identify a candidate male-sterility mutation in the VviINP1 gene and potential female-sterility function associated with the transcription factor VviYABBY3 . Our data suggest that dioecy has been lost during domestication through a rare recombination event between male and female haplotypes. This work significantly advances the understanding of the genetic basis of sex determination in Vitis and provides the information necessary to rapidly identify sex types in grape breeding programs.

Mating in seed plants arises from interactions between plant traits and the environmental and demographic context in which individuals reside. These interactions commonly cause nonrandom mating, including selfing and promiscuous outcrossing within local neighborhoods. Shared features of seed plants, specifically immobility, hermaphroditism, and modularity, shape the essential character of mating mediated by animals, wind, and water. In addition, diverse floral strategies promote cross- and self-mating, depending on environmental circumstances. Extrinsic ecological factors influence all stages of the mating process-pollination, pollen-tube growth, ovule fertilization-as well as seed development, determining offspring quantity and quality. Traditionally, measures of plant mating systems have focused on a single axis of variation, the maternal outcrossing rate. Instead, we argue for an expanded perspective encompassing mating portfolios, which include all offspring to which individuals contribute genetically as maternal or paternal parents. This approach should expose key ecological determinants of mating-system variation and their evolutionary consequences.

A major reason for studying plant sex chromosomes is that they may often be ‘young’ systems. There is considerable evidence for the independent evolution of separate sexes within plant families or genera, in some cases showing that the maximum possible time during which their sex-determining genes have existed must be much shorter than those of several animal taxa. Consequently, their sex-linked regions could either have evolved soon after genetic sex determination arose or considerably later. Plants, therefore, include species with both young and old systems. I review several questions about the evolution of sex-determining systems and sex chromosomes that require studies of young systems, including: the kinds of mutations involved in the transition to unisexual reproduction from hermaphroditism or monoecy (a form of functional hermaphroditism); the times when they arose; and the extent to which the properties of sex-linked regions of genomes reflect responses to new selective situations created by the presence of a sex-determining locus. I also evaluate which questions are best studied in plants, vs other suitable candidate organisms. Studies of young plant systems can help understand general evolutionary processes that are shared with the sex chromosomes of other organisms.

There is increasing recognition that pollination deficits are limiting crop yields world‐wide. However, management strategies for optimal insect pollination are still unclear for most crops. Current management focuses on providing high densities of honeybees, but recommended densities are highly variable, even within single crops and cultivars. We performed an extensive literature search to record honeybee densities (colony density and/or flower visitation rates) and crop productivity (fruit set, seed set, fruit weight and/or yield). Effect sizes were represented as the difference in crop productivity between the two most extreme levels of honeybee densities. Out of 795 reviewed studies, only 22 analysed the effect of at least two levels of honeybee densities on crop productivity (reporting 60 resulting effect sizes in total). Moreover, few recommendations for crop pollination management are based on results from controlled experimental designs, and with comparable methodology. We found that both colony density and visitation rates increased all the productivity variables. However, effects were nonlinear for visitation rates, suggesting that there is an optimum (mean of 8–10 visits per flower) beyond which more honeybees are not beneficial (and can even be detrimental) for crop productivity. Effect sizes for visitation rates were greater than that for colony densities, suggesting that visitation rates are a more direct measure of the pollination process. Data on the relation between colony density and visitation rates are lacking. Interestingly, effect sizes for visitation rates were greater for crops with separate sexes than those with hermaphroditic flowers; therefore, the benefits of honeybee pollination vary according to the crop biology. Synthesis and applications. Current practices for crop pollination assume that more honeybees are always better for crop yield, even if the effect of this management on crop production still unclear. In contrast, our analyses suggest that there is an optimum for honeybee densities. Despite the importance of honeybees and pollinator‐dependent crops world‐wide, there is a lack of studies designed for finding such an optimal level of crop pollination. Our analyses further suggest that visitation rates could be used as a proxy to guide management recommendations such as colony density and spatial arrangement. Foreign Language Resumen Los déficits de polinización están limitando la productividad de los cultivos en todo el mundo. Para sustentar el servicio de polinización en zonas de agricultura intensiva, el manejo actual consiste en saturar los cultivos de flores con abejas melíferas proveyendo altas densidades de colmenas. Sin embargo, se sabe muy poco sobre la eficiencia de este manejo para poder alcanzar una polinización óptima y existe controversia respecto las densidades recomendadas. Realizamos una síntesis global de la literatura científica para registrar la densidad de abejas meliferas (tasa de visitas o densidad de colmenas) y la productividad de los cultivos (cantidad de frutos o de semillas por flor, peso del fruto, o rendimiento por hectárea o planta). Los tamaños de efecto se calcularon como la diferencia en la productividad entre los dos niveles más extremos de densidades de abejas. De los 795 estudios revisados, solo 22 analizaron el efecto de al menos dos niveles de densidad de abejas sobre la productividad de los cultivos (resultando en 60 tamaños de efecto en total). Además, pocos estudios se basan en los resultados de diseños experimentales controlados y con una metodología comparable. Encontramos que tanto la tasa de visita como la densidad de colmenas aumentaron todas las variables de productividad. Sin embargo, el efecto de la tasa de visita fue curvilíneo, lo que sugiere que hay un óptimo (8‐10 visitas por flor) más allá del cual mas abejas no es beneficioso (o incluso perjudicial) para la productividad de los cultivos. Los tamaños de efecto para la tasa de visitas fueron mayores que para la densidad de colmenas, lo que sugiere que la tasa de visitas es una medida más directa del proceso de polinización. Faltan datos sobre la relación entre la tasa de visitas y la densidad de colmenas. De modo interesante, el tamaño de efecto de la tasa de visitas fue mayor para cultivos con sexos separados que para aquellos con flores hermafroditas, lo que sugiere que los beneficios de la polinización por la abeja melífera dependen de la biología floral. Síntesis y aplicaciones. El manejo actual para la polinización de los cultivos asume que más abejas siempre aumenta la productividad de los cultivos. En cambio, nuestros análisis sugieren que existe un óptimo para la tasa de visita de abejas y que esa variable podría usarse como un proxy para guiar las recomendaciones de manejo, como la densidad de colmenas y su disposición espacial. Current practices for crop pollination assume that more honeybees are always better for crop yield, even if the effect of this management on crop production still unclear. In contrast, our analyses suggest that there is an optimum for honeybee densities. Despite the importance of honeybees and pollinator‐dependent crops world‐wide, there is a lack of studies designed for finding such an optimal level of crop pollination. Our analyses further suggest that visitation rates could be used as a proxy to guide management recommendations such as colony density and spatial arrangement.

Dioecy (gonochorism) is dominant within the Animalia, although a recent review suggests hermaphroditism is also common. Evolutionary transitions from dioecy to hermaphroditism (or vice versa) have occurred frequently in animals, but few studies suggest the advantage of such transitions. In particular, few studies assess how hermaphroditism evolves from dioecy or whether androdioecy or gynodioecy should be an \"intermediate\" stage, as noted in plants. Herein, these transitions are assessed by documenting the numbers of androdioecious and gynodioecious animals and inferring their ancestral reproductive mode. Both systems are rare, but androdioecy was an order of magnitude more common than gynodioecy. Transitions from dioecious ancestors were commonly to androdioecy rather than gynodioecy. Hermaphrodites evolving from sexually dimorphic dioecious ancestors appear to be constrained to those with female-biased sex allocation; such hermaphrodites replace females to coexist with males. Hermaphrodites evolving from sexually monomorphic dioecious ancestors were not similarly constrained. Species transitioning from hermaphroditic ancestors were more commonly androdioecious than gynodioecious, contrasting with similar transitions in plants. In animals, such transitions were associated with size specialization between the sexes, whereas in plants these transitions were to avoid inbreeding depression. Further research should frame these reproductive transitions in a theoretical context, similar to botanical studies.

The pen shell, Pinna nobilis L., is a critically endangered bivalve threatened by mass mortality events throughout the Mediterranean, but the Alfacs Bay (Ebro Delta) still hosts many healthy individuals. Herein, we study the main factors controlling recruitment patterns in this locality, including gonadal development and abundance of critical life-stages, as well as the effect of environmental factors. Growth records from empty shells suggested a single major peak of recruitment during a period of 11 years, although many juveniles were found in two very shallow sand bars possibly acting as a barrier for water circulation and as a trap for larvae. Collectors deployed outside these sand bar areas showed zero settlers, and the availability of planktonic larvae was very low. Gonadal examination evidenced breeding throughout the summer period with successive hermaphroditism, but 20% of individuals were simultaneous hermaphrodites, a condition that has been associated with environmental stress and that could lead to in-breeding depression and potentially reduced fertility. Yet, given the large size of the population and the wide breeding period observed, planktonic processes causing larval mortality such as freshwater discharges from rice locally important rice agriculture are also proposed as possible impacts accounting for patterns of low larval availability.