Does Sex Speed Up Evolutionary Rate and Increase Biodiversity?

Most empirical and theoretical studies have shown that sex increases the rate of evolution, although evidence of sex constraining genomic and epigenetic variation and slowing down evolution also exists. Faster rates with sex have been attributed to new gene combinations, removal of deleterious mutations, and adaptation to heterogeneous environments. Slower rates with sex have been attributed to removal of major genetic rearrangements, the cost of finding a mate, vulnerability to predation, and exposure to sexually transmitted diseases. Whether sex speeds or slows evolution, the connection between reproductive mode, the evolutionary rate, and species diversity remains largely unexplored. Here we present a spatially explicit model of ecological and evolutionary dynamics based on DNA sequence change to study the connection between mutation, speciation, and the resulting biodiversity in sexual and asexual populations. We show that faster speciation can decrease the abundance of newly formed species and thus decrease long-term biodiversity. In this way, sex can reduce diversity relative to asexual populations, because it leads to a higher rate of production of new species, but with lower abundances. Our results show that reproductive mode and the mechanisms underlying it can alter the link between mutation, evolutionary rate, speciation and biodiversity and we suggest that a high rate of evolution may not be required to yield high biodiversity

SEXUAL VS. ASEXUAL REPRODUCTION IN A STICK INSECT (MEGAPHASMA DENTRICUS)

The paradox of sex is one of biology’s great evolutionary questions, particularly in those species that are fully capable of sexual and asexual reproduction. To quantify how fitness varies between these two modes of reproduction, we explored lifetime fecundity in Megaphasma dentricus, the giant walking stick of North America. For the first 20 days of egg laying, there were no fecundity differences between mated and unmated females with respect to egg number or egg weight; all females laid a total of ~50 eggs and each egg weighed about 0.02g. For days 21-50 (the last 30 days of egg laying), unmated females laid significantly fewer (but not lighter) eggs than sexually reproducing females. Overall, lifetime fecundity in unmated females was about 5-10% less than mated females. Myriad factors remain unexplored in this species, including the ploidy of sexually and asexually produced eggs, the effects of parasites or other considerations of co-evolution (e.g., the Red Queen Hypothesis), and the accumulation of deleterious mutations (e.g., Muller’s Ratchet)

Genetic Similarity of Commerson’s Anchovy across Segara Anakan Cilacap Assessed Using Randomly Amplified Polymorphic DNA (RAPD) Markers

Segara Anakan areas can be divided into three different regions according to their salinity. Salinity differences suggested that Commerson’s anchovy population in that area can be divided into three subpopulations due to genetic differences. Genetic differences among subpopulation can be assessed through a population genetic study using random amplified polymorphic DNA. This study aims to evaluate the genetic variation and differences of Commerson's anchovy (Stolephorus commersonnii) collected at three different water salinities in Segara Anakan estuary Cilacap Indonesia. Total genomic DNA was isolated using the Chelex method. Genetic diversity and differences were assessed using RAPD markers and were analyzed statistically using an analysis of molecular variance, as implemented in Arlequin software.  The results showed that high genetic diversity was observed within the subpopulations. However, no significant genetic differences were observed among subpopulations which indicate genetic similarity. A high number of offspring are likely to cause high genetic variation within subpopulations.  Adult and larvae migration is the cause of genetics similarity across Segara Anakan. Another impressive result is that water salinity did not affect the genetic characteristic of Commerson,s anchovy. Genetic similarity of Commerson’s anchovy indicates that Segara Anakan forms a single genetic conservation unit

Modelos espaciais de especiação

Orientador: Marcus Aloizio Martinez de AguiarTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: A impressionante diversidade observada na natureza nos faz pensar quais processos podem ser responsáveis por tamanha variedade. Responder esta questão foi o objetivo de muito biólogos evolutivos, que tentaram descobrir os processos olhando para os padrões que eles poderiam gerar. O desenvolvimento de modelos teóricos, em particular modelos baseados em indivíduo, é indispensável para lidar com esta questão, pois apenas com modelos podemos isolar processos específicos em um ambiente controlado, o que não é completamente possível em experimentos naturais, e em um tempo realizável. Nesta tese eu investiguei quais são os padrões gerados por um modelo de especiação baseado em indivíduo no qual apenas processos neutros e o espaço estão regulando a dinâmica populacional. A população evoluiu sob as influências combinadas de reprodução sexuada, mutação e dispersão. No primeiro capítulo, desenvolvemos um algoritmo que registra as relações de ancestralidade-descendência entre pares de indivíduos da comunidade final, e um algoritmo que registra os tempos exatos de especiação e extinção das espécies. Com ambas as informações foi possível construir genealogias e filogenias, a partir das quais padrões macroevolutivos foram obtidos, servindo como um referencial de evolução neutra. O segundo capítulo foi dedicado a usar esta nova informação filogenética do modelo para investigar se diferentes contextos geográficos de especiação (parapátrica e simpátrica) deixam assinaturas distintas nos padrões macroevolutivos de diversificação, como a simetria de árvores e a velocidade da diversificação. Os resultados das simulações foram comparados com dados empíricos de radiações evolutivas. O terceiro capítulo, por fim, incorporou barreiras espaciais ao modelo anterior, para buscar por possíveis assinaturas deixadas pela especiação alopátrica, com barreiras variando em tamanho e permitindo que indivíduos as cruzassem dependendo de seu tamanho. O modelo foi adaptado ao sistema particular dos macacos Platyrrhini, com o espaço modelado de modo a se ajustar à forma da América do Sul, e as barreiras representando os principais rios da região. O número de gerações foi adaptado a diferentes subfamílias e gêneros dos Platyrrhini, para examinar a "Riverine Hypothesis" com um enfoque de modelagem. Os resultados dos três capítulos mostraram que o espaço possui um papel fundamental na especiação quando processos neutros são os únicos a agir sob as populações, com o contexto geográfico da especiação deixando assinaturas nos padrões macroevolutivos emergentes. A incorporação de processos não neutros e a investigação do papel da extinção em moldar os padrões são possíveis passos seguintes para esta pesquisaAbstract: The impressive diversity observed in nature makes us wonder what processes could be responsible for so great variety. The answer to this question has been the goal of many evolutionary biologists, who have tried to discover the processes looking for the patterns they would generate. The development of theoretical models, particularly individual-based models, is imperative to address this question, as only with models we can isolate specific processes in a controled environment, something not completely possible in natural experiments, and in a feasible time. In this thesis I investigated what are the patterns generated by an individual-based model of speciation in which only neutral processes and the space are regulating the dynamics of the population. The population evolved under the combined influences of sexual reproduction, mutation and dispersal. In the first chapter, we developed an algorithm that records the ancestor-descendant relationships between each pair of individuals of the final community, and an algorithm which records the exact speciation and extinction times of species. With both information was possible to construct genealogies and phylogenies, from which macroevolutionary patterns could be derived, offering a neutral referential of evolution. The second chapter was dedicated to use this new phylogenetic information of the model to investigate if different geographical contexts of speciation (parapatric and sympatric) leave different signatures in the macroevolutionary patterns of diversification, like tree symmetry and the speed of diversification. The simulations results were compared with empirical data about evolutionary radiations. The third chapter, lastly, incorporated spatial barriers to the previous model with the goal of looking for possible signatures left by allopatric speciation, with barriers varying in sizes and allowing the crossing of individuals depending on the individual size. The model adapted to the particular system of Platyrrhini monkeys, with space modeled to fit the shape of South America, and spatial barriers representing the main rivers of the region. The number of generations was adapted to conform different subfamilies and genera of Platyrrhini monkeys, with the aim of examine the Riverine Hypothesis in a modeling approach. All results from the three chapters have showed that the space plays a fundamental role in speciation when neutral processes are the only acting upon populations, with the geographic context of speciation leaving signatures in the macroevolutionary patterns emerged. The incorporation of non neutral processes and the investigation of the role of extinction in shaping the patterns are possible next steps to this researchDoutoradoEcologiaDoutora em EcologiaCAPE

Does Sex Speed Up Evolutionary Rate and Increase Biodiversity?

Most empirical and theoretical studies have shown that sex increases the rate of evolution, although evidence of sex constraining genomic and epigenetic variation and slowing down evolution also exists. Faster rates with sex have been attributed to new gene combinations, removal of deleterious mutations, and adaptation to heterogeneous environments. Slower rates with sex have been attributed to removal of major genetic rearrangements, the cost of finding a mate, vulnerability to predation, and exposure to sexually transmitted diseases. Whether sex speeds or slows evolution, the connection between reproductive mode, the evolutionary rate, and species diversity remains largely unexplored. Here we present a spatially explicit model of ecological and evolutionary dynamics based on DNA sequence change to study the connection between mutation, speciation, and the resulting biodiversity in sexual and asexual populations. We show that faster speciation can decrease the abundance of newly formed species and thus decrease long-term biodiversity. In this way, sex can reduce diversity relative to asexual populations, because it leads to a higher rate of production of new species, but with lower abundances. Our results show that reproductive mode and the mechanisms underlying it can alter the link between mutation, evolutionary rate, speciation and biodiversity and we suggest that a high rate of evolution may not be required to yield high biodiversity.</p

Conditions For Neutral Speciation Via Isolation By Distance

The branching of new species from an ancestral population requires the evolution of reproductive isolation between groups of individuals. Geographic separation of sub-populations by natural barriers, if sustained for sufficiently long times, may lead to the accumulation of independent genetic changes in each group and to mating incompatibilities (Mayr, 2001; Fitzpatrick et al., 2009). A similar phenomenon may occur in the absence of barriers via isolation by distance if the population is distributed over large areas (de Aguiar et al., 2009; Etienne and Haegeman, 2011; Gavrilets et al., 2000). The first demonstration of this process was based on computer simulations employing agent-based models. Recently, analytical results were derived combining network theory, to model the spatial structure of the population, and an ansatz that accounts for the effect of forbidding mating between individuals that are too different genetically (de Aguiar and Bar-Yam, 2011). The main result obtained with this approach is an expression that indicates when speciation is possible as a function of the parameters describing the population. The aim of this work is to test this analytical result by comparing it with numerical simulations for a hermaphroditic population (de Aguiar et al., 2009) and for a population whose individuals are explicitly separated into males and females (Baptestini et al., 2013). We show that the analytical formula is indeed a very good overall description of the simulations and that the exponents describing dependence of the critical threshold of speciation with the parameters are in good agreement with the simulations. © 2013 Elsevier Ltd.3355156Ashlock, D., Clare, E.L., von Königslöw, T.E., Ashlock, W., Evolution and instability in ring species complexes. an in silico approach to the study of speciation (2010) J. Theor. Biol., 264, pp. 1202-1213Baptestini, E.M., de Aguiar, M.A.M., Bar-Yam, Y., The role of sex separation in neutral speciation (2013) J. Theor. Ecol.Cannings, C., The latent roots of certain Markov chains arising in genetics. a new approach, I. Haploid models (1974) Adv. Appl. Probab., 6, pp. 260-290Chinellato, D.D., de Aguiar, M.A.M., Epstein, I.R., Braha, D., Bar-Yam, Y., (2007), http://arxiv:0705.4607v2, Dynamical Response of Networks Under External Perturbations: Exact Results. [nlin.SI]de Aguiar, M.A.M., Bar-Yam, Y., Moran model as a dynamical process on networks and its implications for neutral speciation (2011) Phys. Rev. E, 84, p. 031901de Aguiar, M.A.M., Baranger, M., Baptestini, E.M., Kaufman, L., Bar-Yam, Y., Global patterns of speciation and diversity (2009) Nature, 460, pp. 384-387Etienne, R.S., Haegeman, B., The neutral theory of biodiversity with random fission speciation (2011) Theor. Ecol., 4, pp. 87-109Etienne, R.S., Alonso, D., McKane, A.J., The zero-sum assumption in neutral biodiversity theory (2007) J. Theor. Biol., 248, pp. 522-536Ewens, W.J., (1979) Mathematical Population Genetics I. Theoretical Introduction, Series. Biomathematics, 9. , Springer Verlag, New YorkFitzpatrick, B.M., Fordyce, J.A., Gavrilets, S., Pattern, process and geographic modes of speciation (2009) J. Evol. Biol., 22, pp. 2342-2347Gavrilets, S., (2004) Fitness Landscapes and the Origin of Species, , Princeton University PressGavrilets, S., The Maynard Smith model of sympatric speciation (2006) J. Theor. Biol., 239, pp. 172-182Gavrilets, S., Arnqvist, G., Friberg, U., The evolution of female mate choice by sexual conflict (2000) Proc. R. Soc. B, 268, pp. 531-539Gillespie, J.H., (2004) Population Genetics. a Concise Guide, , The Johns Hopkins University PressGladstein, K., The characteristic values and vectors for a class of stochastic matrices arising in genetics (1978) SIAM J. Appl. Math., 34, pp. 630-642Higgs, P.G., Derrida, B., Stochastic models for species formation in evolving populations (1991) J. Phys. A. Math. Gen., 24, pp. L985Higgs, P.G., Derrida, B., Genetic distance and species formation in evolving populations (1992) J. Mol. Evol., 35, pp. 454-465Hoelzer, G.A., Drewes, R., Meier, J., Doursat, R., Isolation-by-distance and outbreeding depression are sufficient to drive parapatric speciation in the absence of environmental influences (2008) PLoS Comput. Biol., 4, pp. e1000126Hubbell, S.P., (2001) The Unified Neutral Theory of Biodiversity and Biogeography, , Princeton University Press, New JerseyIrwin, D.E., Bensch, S., Price, T.D., Speciation in a ring (2001) Nature, 409, pp. 333-337Irwin, D.E., Irwin, J.H., Price, T.D., Ring species as bridges between microevolution and speciation (2001) Genetica, pp. 223-243Irwin, D.E., Bensch, S., Irwin, J.H., Price, T.D., Speciation by distance in a ring species (2005) Science, 307, pp. 414-416Kopp, M., Speciation and the neutral theory of biodiversity (2010) BioEssays, 32, pp. 564-570Lande, R., Kirkpatrick, M., Ecological speciation by sexual selection (1988) J. Theor. Biol., 133, pp. 85-98Manzo, F., Peliti, L., Geographic speciation in the Derrida-Higgs model of species formation (1994) J. Phys. A. Math. Gen., 27, p. 7079Martins, A.B., de Aguiar, M.A.M., Bar-Yam, Y., Evolution and stability of ring species (2013) Proc. Nat. Acad. Sci. USA 110.Mayr, E., (2001) What Evolution is. Basic BooksMelian, C.J., Alonso, D., Allesina, S., Condit, R.S., Etienne, R.S., Does sex speed up evolutionary rate and increase biodiversity? (2012) PLoS Comput. Biol., 8, pp. e1002414Moran, P.A.P., Maximum-likelihood estimation in non-standard conditions (1971) Math. Proc. Cambridge Philos. Soc., 70, pp. 441-450Rosenzweig, M.L., (1995) Species Diversity in Space and Time, , Cambridge University PressWake, D.B., What salamanders have taught us about evolution (2009) Annu. Rev. Ecol. Evol. Syst., 40, pp. 333-352Wakeley, J., (2009) Coalescent Theory, , Roberts and Company PublishersWatterson, G.A., Markov chains with absorbing states. a genetic example (1961) Ann. Math. Stat., 32, pp. 716-729Wright, S., Isolation by distance (1943) Genetics, 28, pp. 114-13