Viability of the vaquita, Phocoena sinus (Cetacea: Phocoenidae) population, threatened by poaching of Totoaba macdonaldi (Perciformes: Sciaenidae) / Viabilidad de la población de vaquita marina, Phocoena sinus (Cetacea: Phocoenidae), amenazada por la pesca ilegal de Totoaba macdonaldi (Perciformes: Sciaenidae)

Abstract Introduction: Despite extensive science-based conservation policy recommendations, with fewer than 20 individuals remaining, the vaquita (Phocoena sinus) -endemic to the Gulf of California- is the world's most endangered marine mammal due to incidental catch in fishing nets and whether it can recover is unclear. Objective: Assess expectations for vaquita over the next two decades. Methods: We identified factors affecting the vaquita, constructed life tables, derived demographic parameters for different scenarios and conducted a population viability analysis using stochastic age-structured matrix Leslie models. Results: Analytical results indicate that the vaquita net growth rate is particularly sensitive to juvenile survival. We find that intensive, ongoing bycatch in gillnets used to poach totoaba (Totoaba macdonaldi) over the past decade brought the vaquita population to its current critically low size. Currently this seems to be exacerbated by demographic stochasticity and a potential Allee effect. Conclusions: If totoaba poaching is eliminated immediately, demographically, vaquita can recover; its long-term survival will depend on its uncertain genetic status, although a recent study found encouraging results in this regard.

Resumen Introducción: Pese a las acciones de conservación basadas en la ciencia y las políticas recomendadas, con menos de 20 individuos sobrevivientes, la vaquita (Phocoena sinus) -endémica del Golfo de California- es el mamífero marino más amenazado del mundo debido a su muerte incidental en redes de pesca; una pregunta relevante es si su población se puede recuperar. Objetivo: Evaluar las expectativas para la vaquita marina durante los próximos 20 años. Métodos: Identificamos los factores que afectan a la vaquita marina, construimos tablas de vida, derivamos parámetros demográficos para diferentes escenarios y realizamos un análisis de viabilidad poblacional utilizando matrices estocásticas de Leslie, estructuradas por edad. Resultados: La tasa de crecimiento neto de la vaquita es muy sensible a la supervivencia de los juveniles. Encontramos que la captura incidental intensiva y continua en redes de enmalle para la pesca furtiva de totoaba (Totoaba macdonaldi) durante la última década llevó a la población de vaquitas a su actual estado crítico. Esto parece agravarse por la estocasticidad demográfica y un potencial efecto Allee. Conclusiones: Si la pesca furtiva de totoaba se elimina de inmediato, demográficamente la vaquita puede recuperarse; su supervivencia a largo plazo dependerá de su incierto estatus genético, aunque los resultados de un estudio reciente son alentadores en este sentido.

Stochastic developmental variation, an epigenetic source of phenotypic diversity with far-reaching biological consequences.

This article reviews the production of different phenotypes from the same genotype in the same environment by stochastic cellular events, nonlinear mechanisms during patterning and morphogenesis, and probabilistic self-reinforcing circuitries in the adult life. These aspects of phenotypic variation are summarized under the term‘stochastic developmental variation’ (SDV) in the following. In the past, SDV has been viewed primarily as a nuisance, impairing laboratory experiments, pharmaceutical testing, and true-to-type breeding. This article also emphasizes the positive biological effects of SDV and discusses implications for genotype-to-phenotype mapping, biological individuation, ecology, evolution, and applied biology. There is strong evidence from experiments with genetically identical organisms performed in narrowly standardized laboratory set-ups that SDV is a source of phenotypic variation in its own right aside from genetic variation and environmental variation. It is obviouslymediated bymolecular and higher-order epigeneticmechanisms. Comparison of SDV in animals, plants, fungi, protists, bacteria, archaeans, and viruses suggests that it is a ubiquitous and phylogenetically old phenomenon. In animals, it is usually smallest for morphometric traits and highest for life history traits and behaviour. SDV is thought to contribute to phenotypic diversity in all populations but is particularly relevant for asexually reproducing and genetically impoverished populations, where it generates individuality despite genetic uniformity. In each generation, SDV produces a range of phenotypes around a well-adapted target phenotype, which is interpreted as a bet-hedging strategy to cope with the unpredictability of dynamic environments. At least some manifestations of SDV are heritable, adaptable, selectable, and evolvable, and therefore, SDV may be seen as a hitherto overlooked evolution factor. SDV is also relevant for husbandry, agriculture, and medicine because most pathogens are asexuals that exploit this third source of phenotypic variation tomodify infectivity and resistance to antibiotics. Since SDV affects all types of organisms and almost all aspects of life, it urgently requires more intense research and a better integration into biological thinking.

Evidências do efeito Moran na sincronia populacional: uma demonstração em microcosmo experimental / Evidences of Moran effect in the population synchrony: a demonstration in experimental microcosm

São propostas três causas principais para sincronia de populações: fatores exógenos, dispersão e interações interespecíficas. O presente trabalho teve por objetivo testar a influência dos fatores exógenos na sincronia de populações de Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae), isoladas espacialmente (sem dispersão), em microcosmos com diferentes condições ambientais (umidade e temperatura). Doze populações com 20 indivíduos cada, foram divididas, aleatoriamente, em dois tratamentos: com lâmpada e sem lâmpada. O censo dos indivíduos adultos foi realizado semanalmente, durante sete meses. A tendência de crescimento da abundância ao longo do tempo foi eliminada através do ajuste de modelos autoregressivos. A sincronia entre as populações, detectada por meio dos coeficientes de correlação de Pearson e Spearman, foi maior dentro do que entre tratamentos, embora as populações mantidas sem lâmpada tenham sido mais sincrônicas do que as populações com lâmpada. Além de evidenciarem a influência do ambiente nas flutuações populacionais, esses resultados sugerem que o metabolismo e as interações intraespecíficas são fatores importantes na dinâmica populacional. Organismos em ambientes desfavoráveis podem apresentar taxas metabólicas anormais, contribuindo pouco para o crescimento populacional. Logo, populações pequenas sofrem maior influência da estocasticidade demográfica, reduzindo a probabilidade de sincronia entre elas. Nos ambientes mais favoráveis, espera-se que os indivíduos desenvolvam funções metabólicas normais, levando as populações a apresentar taxas de crescimento mais elevadas. Nesse caso, a estocasticidade demográfica tem menor influência, levando as populações sem lâmpada a flutuar de forma mais sincrônica.

Three main causes to population synchrony are proposed: exogenous factors, dispersal and inter-specific interactions. This paper had as main goal to test the influence of the exogenous factors in the synchrony in spatially isolated (i.e., no dispersal) populations of Sitophilus zeamais (Mots.) (Coleoptera: Curculionidae), in microcosms with different environmental conditions (humidity, temperature and light intensity). Twelve populations of 20 individuals each, were randomly assigned between two treatment conditions: with or without light. Population size and environmental factors (temperature and relative humidity) were weekly assessed for seven months. Temporal trend in populations increase was eliminated adjusting autoregressive models. Population synchrony, detected by means of Pearson’s and Spearman’s correlation coefficients, was higher within than between treatments, although the populations kept without lamp were more synchronized than populations with lamp. Besides demonstrating the influence of environment on population fluctuations, these results suggest that metabolism and intra-specific interactions are important factors in population dynamic. Organisms exposed to unsuitable environmental conditions may have abnormal metabolic rates, which negatively influences the population grow. Thus, small populations are more likely to suffer from demographic stochasticity, decreasing the probability of the synchrony among populations. On the other hand, in more suitable environments, individuals are expected to have normal metabolic functions, and so, to achieve higher rates of population grow. In this case, the demographic stochasticity has smaller influence, leading populations without lamp to fluctuate synchronously.