scholarly journals The evolution of strong reproductive isolation between sympatric intertidal snails

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190545 ◽  
Author(s):  
Sean Stankowski ◽  
Anja M. Westram ◽  
Zuzanna B. Zagrodzka ◽  
Isobel Eyres ◽  
Thomas Broquet ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Biological Diversity ◽  
Demographic History ◽  
Egg Laying ◽  
Female Reproduction ◽  
Open Questions ◽  
Geographical Separation ◽  
Short Period ◽  
Littorina Arcana ◽  
Subsequent Effect

The evolution of strong reproductive isolation (RI) is fundamental to the origins and maintenance of biological diversity, especially in situations where geographical distributions of taxa broadly overlap. But what is the history behind strong barriers currently acting in sympatry? Using whole-genome sequencing and single nucleotide polymorphism genotyping, we inferred (i) the evolutionary relationships, (ii) the strength of RI, and (iii) the demographic history of divergence between two broadly sympatric taxa of intertidal snail. Despite being cryptic, based on external morphology, Littorina arcana and Littorina saxatilis differ in their mode of female reproduction (egg-laying versus brooding), which may generate a strong post-zygotic barrier. We show that egg-laying and brooding snails are closely related, but genetically distinct. Genotyping of 3092 snails from three locations failed to recover any recent hybrid or backcrossed individuals, confirming that RI is strong. There was, however, evidence for a very low level of asymmetrical introgression, suggesting that isolation remains incomplete. The presence of strong, asymmetrical RI was further supported by demographic analysis of these populations. Although the taxa are currently broadly sympatric, demographic modelling suggests that they initially diverged during a short period of geographical separation involving very low gene flow. Our study suggests that some geographical separation may kick-start the evolution of strong RI, facilitating subsequent coexistence of taxa in sympatry. The strength of RI needed to achieve sympatry and the subsequent effect of sympatry on RI remain open questions. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.

logjam Encodes a Predicted EMP24/GP25 Protein That Is Required for Drosophila Oviposition Behavior

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 173-186
Author(s):  
Ginger E Carney ◽  
Barbara J Taylor
Keyword(s):  
Intracellular Trafficking ◽  
Oviposition Behavior ◽  
Egg Laying ◽  
P Element ◽  
Female Reproduction ◽  
Multiple Functions ◽  
Cytoplasmic Vesicles ◽  
Egg Chambers ◽  
Low Levels ◽  
Overlapping Transcripts

Abstract A newly characterized Drosophila melanogaster gene, logjam (loj), functions in female reproduction by modulating oviposition behavior. The locus encodes at least six overlapping transcripts with unique 5′ ends. P-element mutants that express very low levels of loj transcripts are unable to oviposit mature eggs. This phenotype can be rescued by the introduction of a transgene expressing the most abundant loj transcript. As for many genes that specify behavioral outputs, loj is present in the adult central nervous system (CNS). Interestingly, it is also observed in vitellogenic egg chambers, suggesting that there may be multiple functions for this gene in egg-laying behavior. loj encodes a predicted protein with homology to the EMP24/GP25 transmembrane components of cytoplasmic vesicles and likely functions in intracellular trafficking.

scholarly journals Phenotypic Dimensions of Reproductive Isolation Between Northern and Melissa Blue Butterflies in the Rocky Mountains

2011 ◽  
Vol 33 ◽  
pp. 101-105
Author(s):  
Zachariah Gompert
Keyword(s):  
Reproductive Isolation ◽  
Biological Diversity ◽  
Butterfly Species ◽  
General Importance ◽  
Greater Yellowstone Area ◽  
Single Character ◽  
Character Variation ◽  
Greater Yellowstone ◽  
Species Speciation

Biological diversity results from speciation, which generally involves the splitting of an ancestral species into descendant species due to adaptation to different niches or the evolution of reproductive incompatibilities (Coyne and Orr 2004). The diverse flora and fauna of the world, including the native inhabitants of the Greater Yellowstone Area (GYA), exist as a result of the speciation process. The central role speciation plays in generating biological diversity imbues importance to our understanding of this process. The general importance of a thorough understanding of speciation is amplified because of the current high rates of extinction on the planet. This is because a long term solution to the present extinction crisis will require maintaining the processes that create species (speciation) not simply preventing extinction. However, many central questions regarding speciation remain to be answered. One fundamental question in speciation research is whether diverging species are isolated (i.e., prevented from interbreeding) due to differences in one, a few, or many characters and whether each of these character differences results from different alleles at a few or many genes. For example, speciation and reproductive isolation might involve divergence along multiple phenotypic axes, such as mate preference, habitat use or preference, and phenology (the timing of life-cycle events). Alternatively, isolation could result from differentiation of a single character. I propose to address this question by assessing patterns of variation for a suite of characters across a hybrid zone between two butterfly species. This is possible because patterns of character variation across hybrids zones allow for inferences about reproductive isolation (Barton and Hewitt 1985).

scholarly journals Phenotypic Dimensions of Reproductive Isolation Between Northern and Melissa Blue Butterflies in the Rocky Mountains

2009 ◽  
Vol 32 ◽  
pp. 97-100
Author(s):  
Zachariah Gompert
Keyword(s):  
Reproductive Isolation ◽  
Biological Diversity ◽  
Butterfly Species ◽  
General Importance ◽  
Greater Yellowstone Area ◽  
Single Character ◽  
Character Variation ◽  
Greater Yellowstone ◽  
Species Speciation

Biological diversity results from speciation, which generally involves the splitting of an ancestral species into descendant species due to adaptation to different niches or the evolution of reproductive incompatibilities (Coyne and Orr 2004). The diverse flora and fauna of the world, including the native inhabitants of the Greater Yellowstone Area (GYA), exist as a result of the speciation process. The central role speciation plays in generating biological diversity imbues importance to our understanding of this process. The general importance of a thorough understanding of speciation is amplified because of the current high rates of extinction on the planet. This is because a long term solution to the present extinction crisis will require maintaining the processes that create species (speciation) not simply preventing extinction. However, many central questions regarding speciation remain to be answered. One fundamental question in speciation research is whether diverging species are isolated (i.e., prevented from interbreeding) due to differences in one, a few, or many characters and whether each of these character differences results from different alleles at a few or many genes. For example, speciation and reproductive isolation might involve divergence along multiple phenotypic axes, such as mate preference, habitat use or preference, and phenology (the timing of life-cycle events). Alternatively, isolation could result from differentiation of a single character. I propose to address this question by assessing patterns of variation for a suite of characters across a hybrid zone between two butterfly species. This is possible because patterns of character variation across hybrids zones allow for inferences about reproductive isolation (Barton and Hewitt 1985).

scholarly journals Male-Female Interactions and the Evolution of Postmating Prezygotic Reproductive Isolation among Species of the Virilis Subgroup

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Nada Sagga ◽  
Alberto Civetta
Keyword(s):  
Reproductive Isolation ◽  
Egg Laying ◽  
Sperm Transfer ◽  
Geographic Locations ◽  
Future Studies ◽  
Egg Hatchability ◽  
Fertilization Rates ◽  
Postzygotic Barriers ◽  
Storage Organs

Reproductive isolation reduces breeding between species. Traditionally, prezygotic and postzygotic barriers to reproduction have been broadly studied, but in recent years, attention has been brought to the existence of barriers that act after copulation but before fertilization. Here, we show that when D. virilis females from different geographic locations mate with D. novamexicana males, egg laying is normal, but fertilization rates are severely reduced, despite normal rates of sperm transfer. This reduction in fertilization is probably due to lower retention of heterospecific sperm in female storage organs one-to-two days after copulation. An inspection of egg hatchability in crosses between females and males from other virilis subgroup species reveals that isolation due to poor egg hatchability likely evolved during the diversification of D. virilis/D. lummei from species of the novamexicana-americana clade. Interestingly, the number of eggs laid by D. virilis females in heterospecific crosses was not different from the numbers of eggs laid in conspecific crosses, suggesting that females exert some form of cryptic control over the heterospecific ejaculate and that future studies should focus on how female and female-sperm interactions contribute to the loss or active exclusion of heterospecific sperm from storage.

scholarly journals Mechanistic insight into how gonadotropin hormone receptor complexes direct signaling†

2019 ◽  
Vol 102 (4) ◽  
pp. 773-783
Author(s):  
Gillian P Johnson ◽  
Kim Carol Jonas
Keyword(s):  
Hormone Receptor ◽  
Future Research ◽  
Signal Pathways ◽  
Receptor Signaling ◽  
Female Reproduction ◽  
Differential Signal ◽  
Receptor Complexes ◽  
Open Questions ◽  
Future Research Directions ◽  
Pka Pathway

Abstract Gonadotropin hormones and their receptors play a central role in the control of male and female reproduction. In recent years, there has been growing evidence surrounding the complexity of gonadotropin hormone/receptor signaling, with it increasingly apparent that the Gαs/cAMP/PKA pathway is not the sole signaling pathway that confers their biological actions. Here we review recent literature on the different receptor–receptor, receptor–scaffold, and receptor–signaling molecule complexes formed and how these modulate and direct gonadotropin hormone-dependent intracellular signal activation. We will touch upon the more controversial issue of extragonadal expression of FSHR and the differential signal pathways activated in these tissues, and lastly, highlight the open questions surrounding the role these gonadotropin hormone receptor complexes and how this will shape future research directions.

Reproduction in the curly-tailed lizard Leiocephalus psammodromus from the Caicos Islands

1993 ◽  
Vol 71 (11) ◽  
pp. 2147-2151 ◽  
Author(s):  
Geoffrey R. Smith ◽  
John B. Iverson
Keyword(s):  
West Indies ◽  
Fat Body ◽  
Size Structure ◽  
Egg Laying ◽  
Egg Mass ◽  
British West Indies ◽  
Female Reproduction ◽  
Wet Season ◽  
Males And Females ◽  
Fat Body Mass

Reproduction and population structure were examined for the curly-tailed lizard Leiocephalus psammodromus from the Caicos Islands, British West Indies, from 1973 to 1978. Females and males mature at about 65–70 and 75–80 mm snout–vent length, respectively, and at about 1.5–2 years of age. Both male and female reproduction were seasonal, with egg-laying beginning late in the dry season (late April) and ending well into the wet season (September), with hatching during the wet season (late June to December). Multiple annual clutches are probably produced. Clutch size was typically two eggs (mean = 1.72 for 42 clutches). Eggs (preserved) averaged 19.9 × 9.2 mm, and mean preserved egg mass was 1.04 g. Fat-body mass in both males and females decreases with the onset of the reproductive season. The age/size structure of the population varied from month to month, depending on recruitment of hatchlings. Reproduction in Leiocephalus psammodromus is similar to that of other tropical lizards in seasonal environments.

Communal Nesting in the Digger Wasp Cerceris australis (Hymenoptera : Sphecidae)

1982 ◽  
Vol 30 (4) ◽  
pp. 557 ◽  
Author(s):  
HE Evans ◽  
AW Hook
Keyword(s):  
Body Size ◽  
Ovarian Development ◽  
Egg Laying ◽  
Nest Construction ◽  
Digger Wasp ◽  
Short Period ◽  
Eastern Australia ◽  
A Cell ◽  
Selection For ◽  
Successive Generations

Study of 39 nests of Cerceris australis at nine localities in eastern Australia has demonstrated that most nests are occupied by two or three successive generations of wasps and may ultimately contain well over 100 cells. Nests are dug deep in the soil and are provisioned with scarab beetles, which are allowed to accumulate in the burrow before from two to six are placed in a cell. Nests are usually occupied by several females, some of which are provisioners, bringing in beetles day after day and each time leaving the nest usually after only a few seconds, and others are non-provisioners, leaving the nest for a short period once a day and returning without prey. During the day, nest entrances are occupied by females (believed to be usually non-provisioners) stationed facing out; they are effective in deterring the entry of ants and mutillids. The factors that determine what role a female will play remain obscure. Both provisioners and non-provisioners show progressive mandibular wear as well as essentially similar ovarian development; there are no consistent differences in body size between members of the two groups. In any one nest, considerable variation in the appearance of the ovaries is apparent, and oosorption appears to be common. More than one female often appears to be in egg-laying condition, and the fact that cooperating provisioners bring in enough beetles each day to provision several cells suggests that more than one female lays an egg each day. However, the presence of oocytes in various stages of resorption suggests that in some individuals oviposition is suppressed. No correlation was found between extent of oosorption and the provisioner-nonprovisioner dichotomy. The necessity to guard these large, multicellular nests from parasitoids and predators has evidently brought about selection for the development of a caste of guards which, however, continue to play a role in nest construction and presumably in laying eggs on beetles provided by other females.

scholarly journals Genetic and morphometric divergence in the Garnet-Throated Hummingbird Lamprolaima rhami (Aves: Trochilidae)

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5733 ◽  
Author(s):  
Luz E. Zamudio-Beltrán ◽  
Blanca E. Hernández-Baños
Keyword(s):  
Genetic Variation ◽  
El Salvador ◽  
Species Delimitation ◽  
Biological Diversity ◽  
Environmental Changes ◽  
Isolation By Distance ◽  
Demographic History ◽  
Cloud Forests ◽  
Divergence Time Estimates ◽  
Geographic Structure

Cloud forests are one of the most endangered ecosystems in the Americas, as well as one of the richest in biological diversity in the world. The species inhabiting these forests are susceptible to environmental changes and characterized by high levels of geographic structure. The Garnet-Throated Hummingbird, Lamprolaima rhami, mainly inhabits cloud forests, but can also be found in other habitats. This species has a highly restricted distribution in Mesoamerica, and five disjunct regions have been delimited within the current geographic distribution of the species from Mexico to Honduras. According to variation in size and color, three subspecies have been described: L. r. rhami restricted to the Mexican highlands and Guatemala, L. r. occidentalis distributed in Guerrero (Mexico), and L. r. saturatior, distributed in the highlands from Honduras and El Salvador. We analyzed the levels of geographic structure in L. rhami and its taxonomic implications. We used mitochondrial and nuclear DNA to analyze genetic variation, demographic history, divergence times, reconstructed a multilocus phylogeny, and performed a species delimitation analyses. We also evaluated morphological variation in 208 specimens. We found high levels of genetic differentiation in three groups, and significant variation in morphological traits corresponding with the disjunct geographic populations. L. rhami presents population stability with the highest genetic variation explained by differences between populations. Divergence time estimates suggest that L. rhami split from its sister group around 10.55 million years ago, and the diversification of the complex was dated ca. 0.207 Mya. The hypotheses tested in the species delimitation analyses validated three independent lineages corresponding to three disjunct populations. This study provides evidence of genetic and/or morphometric differentiation between populations in the L. rhami complex where four separate evolutionary lineages are supported: (1) populations from the Sierra Madre Oriental and the highlands of Oaxaca (rhami), (2) populations from the highlands of Guerrero (occidentalis), (3) populations from the highlands of Chiapas and Guatemala (this is a non-previously proposed potential taxon: tacanensis), and (4) populations from the highlands of Honduras and El Salvador (saturatior). The main promoters of the geographic structure found in the L. rhami complex are likely the Isthmus of Tehuantepec as a geographic barrier, isolation by distance resulting from habitat fragmentation, and climatic conditions during the Pleistocene.

scholarly journals Ancestral and neo-sex chromosomes contribute to population divergence in a dioecious plant

2019 ◽  
Author(s):  
Felix E.G. Beaudry ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Demographic History ◽  
Population Divergence ◽  
Effective Population ◽  
Dioecious Plant ◽  
Fusion Event ◽  
Contemporary Gene Flow

ABSTRACTEmpirical evidence from several animal groups suggests that sex chromosomes may disproportionately contribute to reproductive isolation. This occurs particularly when sex chromosomes are associated with turnover of sex determination systems resulting from structural rearrangements to the sex chromosomes. We investigated these predictions in the dioecious plant Rumex hastatulus, which is comprised of populations of two sex chromosome cytotypes. Using population genomic analyses, we investigated the demographic history of R. hastatulus and explored the contributions of ancestral and neo-sex chromosomes to population genetic divergence. Our study revealed that the cytotypes represented genetically divergent populations with evidence for historical but not contemporary gene flow between them. In agreement with classical predictions, we found that the ancestral X chromosome was disproportionately divergent compared with the rest of the genome. Excess differentiation was also observed on the Y chromosome, even when using measures of differentiation that control for differences in effective population size. Our estimates of the timing of the origin of the neo-sex chromosomes in R. hastatulus are coincident with cessation of gene flow, suggesting that the chromosomal fusion event that gave rise to the origin of the XYY cytotype may have also been a key driver of reproductive isolation.

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