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Farmer NA, Doerr JC. Limiting factors for queen conch (Lobatus gigas) reproduction: A simulation-based evaluation. PLoS One 2022; 17:e0251219. [PMID: 35263325 PMCID: PMC8906866 DOI: 10.1371/journal.pone.0251219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 02/21/2022] [Indexed: 11/18/2022] Open
Abstract
Queen conch are among the most economically, socially, and culturally important fishery resources in the Caribbean. Despite a multitude of fisheries management measures enacted across the region, populations are depleted and failing to recover. It is believed that queen conch are highly susceptible to depensatory processes, impacting reproductive success and contributing to the lack of recovery. We developed a model of reproductive dynamics to evaluate how variations in biological factors such as population density, movement speeds, rest periods between mating events, scent tracking, visual perception of conspecifics, sexual facilitation, and barriers to movement affect reproductive success and overall reproductive output. We compared simulation results to empirical observations of mating and spawning frequencies from conch populations in the central Bahamas and Florida Keys. Our results confirm that low probability of mate finding associated with decreased population density is the primary driver behind observed breeding behavior in the field, but is insufficient to explain observed trends. Specifically, sexual facilitation coupled with differences in movement speeds and ability to perceive conspecifics may explain the observed lack of mating at low densities and differences between mating frequencies in the central Bahamas and Florida Keys, respectively. Our simulations suggest that effective management strategies for queen conch should aim to protect high-density reproductive aggregations and critical breeding habitats.
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Affiliation(s)
- Nicholas A. Farmer
- NOAA Fisheries Southeast Regional Office, St. Petersburg, Florida, United States of America
| | - Jennifer C. Doerr
- NOAA Fisheries Southeast Fisheries Science Center, Galveston, Texas, United States of America
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O’Connell LA, Crews D. Evolutionary insights into sexual behavior from whiptail lizards. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:88-98. [PMID: 33929097 PMCID: PMC8556411 DOI: 10.1002/jez.2467] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 04/03/2021] [Indexed: 01/03/2023]
Abstract
Is the brain bipotential or is sex-typical behavior determined during development? Thirty years of research in whiptail lizards transformed the field of behavioral neuroscience to show the brain is indeed bipotential, producing behaviors along a spectrum of male-typical and female-typical behavior via a parliamentary system of neural networks and not a predetermined program of constrained behavioral output. The unusual clade of whiptail lizards gave these insights as there are several parthenogenetic all-female species that display both male-typical and female-typical sexual behavior. These descendant species exist alongside their ancestors, allowing a unique perspective into how brain-behavior relationships evolve. In this review, we celebrate the over 40-year career of David Crews, beginning with the story of how he established whiptails as a model system through serendipitous behavioral observations and ending with advice to young scientists formulating their own questions. In between these personal notes, we discuss the discoveries that integrated hormones, neural activity, and gene expression to provide transformative insights into how brains function and reshaped our understanding of sexuality.
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Affiliation(s)
| | - David Crews
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712
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Gore AC, Holley AM, Crews D. Mate choice, sexual selection, and endocrine-disrupting chemicals. Horm Behav 2018; 101:3-12. [PMID: 28888817 PMCID: PMC5845777 DOI: 10.1016/j.yhbeh.2017.09.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 08/26/2017] [Accepted: 09/05/2017] [Indexed: 12/30/2022]
Abstract
Humans have disproportionately affected the habitat and survival of species through environmental contamination. Important among these anthropogenic influences is the proliferation of organic chemicals, some of which perturb hormone systems, the latter referred to as endocrine-disrupting chemicals (EDCs). EDCs are widespread in the environment and affect all levels of reproduction, including development of reproductive organs, hormone release and regulation through the life cycle, the development of secondary sexual characteristics, and the maturation and maintenance of adult physiology and behavior. However, what is not well-known is how the confluence of EDC actions on the manifestation of morphological and behavioral sexual traits influences mate choice, a process that requires the reciprocal evaluation of and/or acceptance of a sexual partner. Moreover, the outcomes of EDC-induced perturbations are likely to influence sexual selection; yet this has rarely been directly tested. Here, we provide background on the development and manifestation of sexual traits, reproductive competence, and the neurobiology of sexual behavior, and evidence for their perturbation by EDCs. Selection acts on individuals, with the consequences manifest in populations, and we discuss the implications for EDC contamination of these processes, and the future of species.
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Affiliation(s)
- Andrea C Gore
- Division of Pharmacology and Toxicology, College of Pharmacy, USA.
| | - Amanda M Holley
- Division of Pharmacology and Toxicology, College of Pharmacy, USA; Department of Integrative Biology, College of Natural Sciences, USA
| | - David Crews
- Department of Integrative Biology, College of Natural Sciences, USA.
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Abstract
Many, if not all, questions in biology and psychology today were formulated and considered in depth, though typically in a different language, from the 1700's to the early 1900's. However, because of politics or fashion, some topics fell out of favor or failed to recruit new scientists and hence languished. Despite greatly expanded scholarship in the history of the life sciences in the twentieth century, many such topics have had to be rediscovered in recent years, while much of the wisdom already accrued stays in the older literature and not in active minds. This is particularly true today when scientific advances appear at breakneck speed. It would not be an exaggeration to say that many 'breakthroughs' turn out really to be rediscoveries of forgotten observations. Two areas of particular significance to the interdisciplinary study of behavior are the Norms of Reaction (from Biology) and the concept of Plasticity (from Psychology). These and related fields benefit from the perspective of epigenetics so long as rigorous operational definitions are implemented. It is also important to revive Hogben's admonition that the interaction of hereditary and environment cannot be understood outside of the context of development. Five examples of increasing complexity in phenotypic plasticity in brain and behavior are presented to illustrate this perspective.
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Affiliation(s)
- David Crews
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Seth A Weisberg
- Institute of Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA
| | - Sahotra Sarkar
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
- Departments of Integrative Biology and Philosophy, The University of Texas at Austin, Austin, TX 78712, USA
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Meirmans S, Meirmans PG, Kirkendall LR. The costs of sex: facing real-world complexities. QUARTERLY REVIEW OF BIOLOGY 2012; 87:19-40. [PMID: 22518931 DOI: 10.1086/663945] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Understanding the maintenance of sexual reproduction constitutes a difficult problem for evolutionary biologists because of the immediate costs that sex seems to incur. Typically, general benefits to sex and recombination are investigated that might outweigh these costs. However, several factors can strongly influence the complex balance between costs and benefits of sex; these include constraints on the evolution of asexuality, ecological differentiation, and certain lif-history traits. We review these factors and their empirical support for the first time in a unified framework and find that they can reduce the costs of sex, circumvent them, or make them inapplicable. These factors can even tip the scales to a net benefit for sex. The reviewed factors affect species and species groups differently, and we conclude consequently that understanding the maintenance of sex could turn out to be more species-specific than commonly assumed. Interestingly, our study suggests that, in some species, no general benefits to sex and recombination might be needed to understand the maintenance of sex, as in our case study of dandelions.
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Affiliation(s)
- Stephanie Meirmans
- Centre for the Study of the Sciences and the Humanities and Department of Biology, University of Bergen 5020 Bergen, Norway.
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Kramer MG, Templeton AR. LIFE-HISTORY CHANGES THAT ACCOMPANY THE TRANSITION FROM SEXUAL TO PARTHENOGENETIC REPRODUCTION IN DROSOPHILA MERCATORUM. Evolution 2007. [DOI: 10.1111/j.0014-3820.2001.tb00811.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Neiman M. Physiological dependence on copulation in parthenogenetic females can reduce the cost of sex. Anim Behav 2004. [DOI: 10.1016/j.anbehav.2003.05.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Kramer MG, Templeton AR, Miller KG. Evolutionary implications of developmental instability in parthenogenetic Drosophila mercatorum. II. Comparison of two strains with identical genotypes, but different modes of reproduction. Evol Dev 2002; 4:234-41. [PMID: 12054296 DOI: 10.1046/j.1525-142x.2002.02009.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Developmental instability is particularly pronounced in parthenogenetic strains of Drosophila mercatorum. All parthenogenetically produced eggs in a given strain have the same genotype, but even when reared in the same environment, only approximately 5% of the eggs initiating development ever reach adulthood. A sexual analogue of a parthenogenetic strain was created to investigate the basis of this developmental instability. The two strains have identical genotypes (except for the Y chromosome in males of the sexual strain) and differ only in mode of reproduction. The sexual strain had a much lower rate of developmental instability than the parthenogenetic strain, suggesting that the instability is caused by the mode of reproduction per se and is not due to homozygosity, disruption of coadapted gene complexes, or any other feature of the parthenogenetic genome. The increased rate of abortion with parthenogenetic reproduction is caused by a proportional increase in the normal panoply of errors that occur in sexual reproduction but at a much lower rate. Attempts to establish other sexual analogues of laboratory parthenogenetic strains revealed different male sterility factors within several parthenogenetic genomes that could potentially act to prevent hybridization with sexually reproducing ancestors during the incipient stages in the evolution of an entirely parthenogenetic lineage.
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Affiliation(s)
- Melissa G Kramer
- Department of Biology, Washington University, St. Louis, MO 63130, USA.
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Kramer MG, Templeton AR. Life-history changes that accompany the transition from sexual to parthenogenetic reproduction in Drosophila mercatorum. Evolution 2001; 55:748-61. [PMID: 11392393 DOI: 10.1554/0014-3820(2001)055[0748:lhctat]2.0.co;2] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In spite of the predicted genetic and ecological costs of sex, most natural populations maintain sexual reproduction, even those capable of facultative parthenogenesis. Unfertilized eggs from natural populations of Drosophila mercatorum occasionally develop into viable adults, but obligately parthenogenetic populations are unknown in this species. To evaluate the microevolutionary forces that both favor and constrain the evolution of parthenogenesis in D. mercatorum, we have measured parthenogenetic rates across a natural, sexually reproducing population and characterized the life-history changes that accompany the transition from sexual to parthenogenetic reproduction in laboratory strains. A highly significant difference in parthenogenetic rate was found between two populations in close geographic proximity, with increased rate found with lower population density. Laboratory strains of parthenogenetic females suffered increased mortality and reduced egg viability relative to their virgin counterparts from a sexual strain. Lifetime egg production was similar across all strains, but a shift in peak egg production to an earlier age also occurred. The combination of these life-history traits resulted in a higher net reproductive value for sexual females, but because they also had a longer generation time, intrinsic rate of increase was not as dramatically different from parthenogenetic females. In environments with high early mortality, there may be no fitness disadvantage to parthenogenesis, but the predicted ecological advantage of a twofold increase in intrinsic rate of increase was not realized. These results support the theory of Stalker (1956) that parthenogenesis is favored in environments in which sexual reproduction is difficult or impossible.
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Affiliation(s)
- M G Kramer
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
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Takenaka-Dacanay JH, Carson HL. Sexual behavior in laboratory strains of Drosophila mercatorum that have spontaneously adopted parthenogenesis. Behav Genet 1991; 21:305-16. [PMID: 1863262 DOI: 10.1007/bf01065822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Three instances are described in which bisexual laboratory strains spontaneously adopted an exclusively parthenogenetic mode of reproduction, even in the presence of fertile, bisexual males. The few males produced by the parthenogenetic strains lack a Y chromosome and are sterile but, nevertheless, showed no correlated impairment of normal mating behavior. In contrast, females show a strong reluctance to accept copulation. This behavioral correlate of parthenogenesis also has been observed previously in experimentally produced parthenogenetic lines. We suggest that genetic breakdown in female mating behavior may contribute to an evolutionary stimulus that results in a selective increase in the frequency of diploidizing events in unfertilized eggs. This ultimately might lead to the origin of an exclusively parthenogenetic reproductive mode.
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Crews D, Grassman M, Lindzey J. Behavioral facilitation of reproduction in sexual and unisexual whiptail lizards. Proc Natl Acad Sci U S A 1986; 83:9547-50. [PMID: 3467325 PMCID: PMC387177 DOI: 10.1073/pnas.83.24.9547] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
All-female, parthenogenetic species afford a unique test of hypotheses regarding the nature and evolution of sexuality. Mating behavior accomplishes the transfer of gametes and stimulates the coordination of reproductive activity of the male and female. Cnemidophorus uniparens, a parthenogenetic species, is believed to have resulted from the hybridization of two extant gonochoristic species, Cnemidophorus inornatus and Cnemidophorus gularis. C. uniparens regularly and reliably perform behaviors identical in form to those performed during mating by male C. inornatus. We have determined experimentally that individuals of the parthenogenetic species demonstrating male-like pseudosexual behavior also share a similarity in function with males of the sexually reproducing species. The number of female C. inornatus ovulating increases, and the latency to ovulation decreases, if a sexually active conspecific male is present. A similar facilitatory effect on ovarian recrudescence occurs in the all-female C. uniparens in the presence of a male-like individual. These results show that behavioral facilitation of ovarian recrudescence is important in sexual and unisexual species. This may represent a potent selection pressure favoring the maintenance of male-typical behaviors, thus accounting for the display of behavioral traits usually associated with males in unisexual species of hybrid origin.
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Abstract
The problem of the maintenance of anisogamous sex is addressed by considering the effect of fertilization on the fitness of parthenogenetic females when such fertilization yields inviable triploid progeny. We consider four types of parthenogenesis: (i) apomixis, (ii) homogametic amphimixis, (iii) heterogametic amphimixis, and (iv) homogametic automixis. Homozygous sexual populations are genetically stable if males or selection eliminate the excess females produced by heterozygous parthenogenetic genotypes. Homozygous parthenogenetic populations are stable if the parthenogenetic output of homozygotes exceeds that of heterozygotes. In turn, sex can only invade heterozygous parthenogenetic populations when sexual output of parthenogens is larger than their parthenogenetic output. The existence of interior stable equilibria generally requires the instability of at least one boundary and some degree of heterosis. In a two-locus model, we study the evolution of mechanisms protecting either sex or parthenogenesis in reproductively polymorphic populations. We find that males do not respond to the presence of parthenogenesis in such a way as to eliminate it, but parthenogenesis is subject to selective pressures increasing reproductive isolation, and thus the success of parthenogenesis. The results suggest that reproductively polymorphic populations are ephemeral.
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Abstract
The proximate mechanisms underlying mating behavior in naturally occurring species can be fundamentally different from those in more commonly studied laboratory and domesticated forms. In naturally occurring species, reproductive strategies are much more diverse, and mechanisms controlling behavior are correspondingly diverse. A variety of hormonal, environmental, and social cues can be used to activate mating behavior. Which cues are used by particular species depends on differences in environmental and physiological constraints imposed by particular reproductive strategies. Study of this diversity of mechanisms promises to identify specific selective forces that have shaped their evolution. This evolutionary perspective leads to widely applicable generalizations and provides a useful context within which to conceptualize differences between species, populations, and individuals.
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Gonda MA, Wong-Staal F, Gallo RC, Clements JE, Narayan O, Gilden RV. Sequence homology and morphologic similarity of HTLV-III and visna virus, a pathogenic lentivirus. Science 1985; 227:173-7. [PMID: 2981428 DOI: 10.1126/science.2981428] [Citation(s) in RCA: 334] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A study was conducted of the genetic relation between human T-cell lymphotropic retroviruses and visna virus. The human T-cell lymphotropic viruses include those associated with T-cell malignancies (HTLV-I and HTLV-II) as well as the etiologic agent of the acquired immune deficiency syndrome (HTLV-III). Visna virus, a slowly replicating and pathogenic but nononcogenic retrovirus of sheep, is a member of the subfamily Lentivirinae. Results obtained by molecular hybridization and heteroduplex analysis indicated that a greater extent of nucleotide sequence homology exists between HTLV-III and visna virus than between HTLV-III and any of the other viruses. The homology observed under conditions of low stringency spanned the entire genome, but was strongest in the gag/pol region. The morphogenesis and fine structure of HTLV-III and visna virus also demonstrated striking similarities. The data provide strong evidence for a close taxonomic and thus evolutionary relation between HTLV-III and the Lentivirinae subfamily.
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