Variation In Reproductive System Research Articles

Contraction and expansion: global geographical variation in reproductive systems of Primula is driven by different mechanisms

AbstractAimReproductive systems strongly influence plants' evolution and adaption, and the biogeographic pattern of its variation has intrigued biologists and ecologists. Here, to test the impacts of paleoglaciation on plants' reproductive system variation, we compared the geographical pattern and environmental drivers in the proportions of different reproductive systems in Primula in regions affected and unaffected by paleoglaciation.LocationGlobal.Time PeriodSince the Last Glacial Maximum (LGM).Major Taxa Studied Primula. MethodsUsing data on reproductive systems and distributions of 604 Primula taxa around the world and 221 along the elevational gradient of the Himalayas, we demonstrated the global pattern and the elevational pattern in the proportions of homostylous taxa. We employed general linear models to establish the relationship between the proportion of homostylous taxa and environmental variables and hierarchical partitioning to assess the relative contributions of these variables in both regions affected and unaffected by paleoglaciation, respectively.ResultsWe found a higher proportion of homostylous taxa in regions glaciated during the LGM than those unglaciated, with different latitudinal patterns and climate drivers. The proportion of homostylous taxa showed varying trends across different regions: increasing with latitude and temperature anomaly in glaciated regions while concentrating at lower latitudes with higher winter temperatures in unglaciated regions. Additionally, homostylous taxa were more prevalent at lower elevations in the Himalayas.Main ConclusionsOur study provides the first quantitative evidence for the hypothesis that selfers are more prevailing in regions affected by paleoglaciation facilitated by recolonization via comparing the geographic pattern and drivers in regions affected and unaffected by paleoglaciation. Our findings also reveal the concentrated distribution of homostylous taxa in Primula at low latitudes, which may be the result of population shrinkage caused by heat stress, facing a more severe survival crisis under the circumstances of global warming and increasing human activities.

Control of social status by sex steroids: insights from teleost fishes

Many animals live in highly social environments, in which individuals must behave in a way that enables them to survive and live harmoniously among conspecifics. Dominance hierarchies are typical among social species and are essential for determining and preserving stability within social groups. Although there is considerable evidence that sex steroid hormones regulate behaviors associated with dominance, such as aggression and mating, fewer studies have examined the role of these hormones in controlling social status, especially in species that exhibit social hierarchies. Furthermore, despite this research, we know remarkably little about the precise neural and molecular mechanisms through which sex steroids modulate traits associated with social rank. Here, we review the neuroendocrine regulation of social status by sex steroids in teleost fishes, the largest and most diverse vertebrate group that shows extensive variation in reproductive systems and social structures between species. First, we describe the function of sex steroids and novel steroid-related genes that teleost fishes possess due to a lineage-specific whole-genome duplication event. Then, we discuss correlational, pharmacological, and molecular genetic studies on the control of social status by sex steroids in teleost fishes, including recent studies that have implemented gene editing technologies, such as CRISPR/Cas9. Finally, we argue that gene editing approaches in teleost studies, within both integrative and comparative frameworks, will be vital for elucidating the role of sex steroids in controlling social rank and characterizing their neural and molecular mechanisms of action. Collectively, ongoing and future research in these species will provide novel insight into the evolution of the regulation of social status by sex steroids and other neuroendocrine substrates across vertebrates.

Comparative phylogeography of bromeliad species: effects of historical processes and mating system on genetic diversity and structure

Abstract A fundamental challenge in population genetics is to understand the role of ecological and historical processes in shaping genetic diversity patterns within and among species. Based on a set of nuclear microsatellite loci, we conducted a comparative study of the genetic diversity and structure of two epiphytic plant species: Vriesea simplex and V. scalaris (Bromeliaceae), endemic to the Brazilian Atlantic Rainforest. The results showed contrasting genetic diversity and structure patterns according to variation in reproductive systems of these species. High genetic diversity, high effective population sizes and low genetic differentiation were observed in the mainly outcrossing V. simplex populations. In contrast, low genetic diversity, low effective population sizes and high genetic differentiation were detected in the mainly selfing V. scalaris populations. Accordingly, the isolation-by-distance indicated stronger population structures in V. scalaris than in V. simplex. Both species showed a similar phylogeographic north-south split across the Atlantic Rainforest, suggesting possible multiple refugia in this biome. Historical climatic changes during the Pleistocene were possible determinants of the genetic diversity and structure of these species in the Atlantic Rainforest. Divergent mating systems (selfing vs. outcrossing), genetic drift and colonization history influenced the genetic diversity and structure of these Neotropical plant species.

Floral morphology and reproductive biology in selected maple (Acer L.) species (Sapindaceae)

This study focuses on variation in reproductive systems in Acer (maple) species, and how Acer might be a useful genus for understanding floral morphology and the evolution of these highly variable systems. The goals were (1) to conduct a survey of reproductive characters in the genus Acer with an emphasis on floral morphometrics of A. ginnala Maxim., A. tataricum L., and the hybrid A. ginnala × tataricum and (2) present a compilation of the reproductive biology of Acer based on the literature and online information. Morphometric analyses showed that the hybrid A. ginnala × tataricum exhibits intermediacy in vegetative morphology and some floral traits compared to the parents. Literature and an online survey revealed some information on the reproductive biology of 40 Acer species, plus the hybrid, representing only 32.3% of the taxonomic diversity. The reproductive modes of Acer include monoecy, dioecy, trioecy, andromonoecy, androdioecy, and andropolygamy, with a trend towards unisexuality. Temporal patterns of maturation of reproductive parts revealed duodichogamy, heterodichogamy, simultaneous, and dichogamy. The pollination syndrome is entomophilous, anemophilous, and ambophilous. We conclude that the evolutionary and geographic success of Acer lie in the versatility of sexual systems, diverse modes of maturation of reproductive organs, reproductive success, and the ability to colonise wider areas.

Variation in reproductive systems facilitates species boundaries of sympatric Vriesea (Bromeliaceae)

Variation in reproductive systems facilitates species boundaries of sympatric Vriesea (Bromeliaceae)

The evolution of plant reproductive systems: how often are transitions irreversible?

Flowering plants are characterized by striking variation in reproductive systems, and the evolutionary lability of their sexual traits is often considered a major driver of lineage diversification. But, evolutionary transitions in reproductive form and function are never entirely unconstrained and many changes exhibit strong directionality. Here, I consider why this occurs by examining transitions in pollination, mating and sexual systems, some of which have been considered irreversible. Among pollination systems, shifts from bee to hummingbird pollination are rarely reversible, whereas transitions from animal to wind pollination are occasionally reversed. Specialized pollination systems can become destabilized through a loss of pollinator service resulting in a return to generalized pollination, or more commonly a reliance on self-pollination. Homomorphic and heteromorphic self-incompatibility systems have multiple origins but breakdown to self-compatibility occurs much more frequently with little evidence for subsequent gains, at least over short time-spans. Similarly, numerous examples of the shift from outcrossing to predominant self-fertilization are known, but cases of reversal are very limited supporting the view that autogamy usually represents an evolutionary dead-end. The evolution of dioecy from hermaphroditism has also been considered irreversible, although recent evidence indicates that the occurrence of sex inconstancy and hybridization can lead to the origin of derived sexual systems from dioecy. The directionality of many transitions clearly refutes the notion of unconstrained reproductive flexibility, but novel adaptive solutions generally do not retrace earlier patterns of trait evolution.

BACK-AND-FORTH HERMAPHRODITISM: PHYLOGENETIC CONTEXT OF REPRODUCTIVE SYSTEM EVOLUTION IN SUBDIOECIOUSDAPHNE LAUREOLA

Recent phylogenetic analyses of sexual reproductive systems supported the evolutionary pathway from hermaphroditism to dioecy via gynodioecy in different groups of angiosperms. In this study, we explore the evolution of sexual reproductive systems in Daphne laureola L. (Thymelaeaceae), a species with variation in reproductive system among population. Sequences from the ITS region of the nuclear ribosomal cistron and two plastid markers (psbA-trnH and ndhF) were analyzed and used to map the population reproductive system along the molecular phylogeny. Our results support D. laureola as a monophyletic lineage with three different clades within the Iberian Peninsula. The hermaphroditic populations belong to two different clades, whereas gynodioecy is ubiquitous but characteristic of the third clade, which grouped together all the North-Western Iberian populations sampled, including the apparently oldest haplotype sampled. Gynodioecy appears as the most likely basal condition of the 13 analyzed populations, but different evolutionary transitions in reproductive sexual system were traced within each D. laureola clade. Both ecological conditions and (meta)population dynamics may help explain plant reproductive system evolution at the microevolutionary scale. Phylogenetic studies in which the historical relationships between populations differing in reproductive system can be ascertained will help to clarify the process.

Towards understanding the dynamics of hybridization and apomixis in the evolution of the genus Boechera (Brassicaceae)

We have reviewed past and recent research on the radiation of the North American genus Boechera (Brassicaceae), and discuss future prospects for our understanding of the evolutionary processes and patterns of differentiation in this highly polymorphic genus. Boechera comprises about 80 biennial to perennial species of exclusively North American and Greenlandic distribution. Hybridization and apomixis, in conjunction with polyploidy, were found to play a major role in the origin and maintenance of intraspecific and interspecific polymorphism. However, taxonomic classification within the genus has mainly been based on morphological characters, and diagnostic features discriminating between taxa are often limited. Molecular markers are promising tools for: the assessment of infrageneric phylogen‐etic relationships, the isolation of basal sexual taxa, the detection of hybridization and estimation of its frequency among lineages in time and space, the identification of centres of genetic and species diversity, and the comparison of various reproductive modes. We present and discuss the major achievements obtained since the introduction of molecular methods to Boechera research with respect to these aims, and point out possible shortcomings of specific marker systems. The distribution and transmission of apomixis, polyphyletic origin of genotypes and cytotypes, variation in reproductive system, and the lack of consensus between current taxonomic concepts and evolutionary evidence are the major topics discussed here in the context of hybridization.

Phenological Variation in Flowering and Fruiting of Asclepias

Phenological studies of flowering and fruiting in experimental plots and in field sites demonstrated variation within and between populations of Asclepias incarnata, A. verticillata and A. syriaca. Flowering of A. incarnata and A. verticillata occurred in July and August, and overlapped at least 30 days. In contrast, A. syriaca typically flowered in June or early July. Umbels of these species displayed open flowers for 5-9 days; 70-95 %o of marked flowers within umbels opened within 1 day of the first open flower. Individual variation in flowering within a species was considerable, and the times of initial flowering of individuals of A. incarnata were significantly correlated between years. Second-year plants varied more than 1st-year plants in peak flowering time, abundance and duration, but not in initial flowering date. Mean percentage fruit set per umbel for late-flowering plants was about twice that of early flowering plants for all species in 1978, despite shorter duration of flowering and lower average umbel abundance. The phenology of fruit maturation and seed release revealed greater synchrony in seed release, as well as longer periods for follicle maturation and dehiscence, for A. syriaca relative to the other species. INTRODUCTION Systematic studies routinely seek to detect and document diagnostic characters that are relatively invariant within species but are discontinuous among species. Reproductive characters are often considered the most useful taxonomically because of their general constancy (Jones and Luchsinger, 1985). Recently, though, we have been made aware of intraspecific, and even intrapopulational, variation in reproductive systems with respect to floral coloration (Paige and Whitham, 1985) and scent (Galen and Kevan, 1983), levels of self-compatibility (Denton, 1979; Kephart, 1981; Perkins et al., 1975), and even the relative placement of stamens and pistils (Waser and Price, 1984). Estes et al. (1983) further argue that monographers often have only cursorily examined potential floral variation, thus missing important factors contributing to species evolution and classification. Flowering time has been used as a reproductive character in taxonomic keys and in classification (Davis and Heywood, 1973); yet most studies have focused on its importance in species isolation (Gentry, 1974; Whitaker, 1944), and in competitive or mutualistic interactions (e.g., Mosquin, 1971; Waser and Real, 1979) rather than on intraspecific variability. Variational patterns among individuals are infrequently reported and only seldom are data available to ascertain the effect of the flowering time on seed production (e.g., Augspurger, 1981; Gross and Werner, 1983; Primack, 1980; Schemske et al., 1978). Few comparative studies of floral variation in both natural populations and experimentally planted areas exist. The present study measures individual and interpopulational variation in flowering and fruiting for three sympatric species (Asclepias incarnata L., A. syriaca L. and A. verticillata L.) grown in common experimental plots and observed in field populations for several seasons. Although flowering periods vary annually for these species (Willson and Price, 1977), little is known of intraspecific variability in flowering among populations and individuals within a local area. Because such variability in flowering time is known to be heritable in other taxa (e.g., Cruciferae, McIntyre and Best, 1978; Caprifoliaceae, McMillan and Pagel, 1958; Leguminosae, Stanford et al., 1962), it is of potential evolutionary significance.