Targeted gene flow and rapid adaptation in an endangered marsupial.

Targeted gene flow is an emerging conservation strategy. It involves translocating individuals with favorable genes to areas where they will have a conservation benefit. The applications for targeted gene flow are wide-ranging but include preadapting native species to the arrival of invasive species. The endangered carnivorous marsupial, the northern quoll (Dasyurus hallucatus), has declined rapidly since the introduction of the cane toad (Rhinella marina), which fatally poisons quolls that attack them. There are, however, a few remaining toad-invaded quoll populations in which the quolls survive because they know not to eat cane toads. It is this toad-smart behavior we hope to promote through targeted gene flow. For targeted gene flow to be feasible, however, toad-smart behavior must have a genetic basis. To assess this, we used a common garden experiment, comparing offspring from toad-exposed and toad-naïve parents raised in identical environments, to determine whether toad-smart behavior is heritable. Offspring from toad-exposed populations were substantially less likely to eat toads than those with toad-naïve parents. Hybrid offspring showed similar responses to quolls with 2 toad-exposed parents, indicating the trait may be dominant. Together, these results suggest a heritable trait and rapid adaptive response in a small number of toad-exposed populations. Although questions remain about outbreeding depression, our results are encouraging for targeted gene flow. It should be possible to introduce toad-smart behavior into soon to be affected quoll populations.

Targeted gene flow for conservation.

Anthropogenic threats often impose strong selection on affected populations, causing rapid evolutionary responses. Unfortunately, these adaptive responses are rarely harnessed for conservation. We suggest that conservation managers pay close attention to adaptive processes and geographic variation, with an eye to using them for conservation goals. Translocating pre-adapted individuals into recipient populations is currently considered a potentially important management tool in the face of climate change. Targeted gene flow, which involves moving individuals with favorable traits to areas where these traits would have a conservation benefit, could have a much broader application in conservation. Across a species' range there may be long-standing geographic variation in traits or variation may have rapidly developed in response to a threatening process. Targeted gene flow could be used to promote natural resistance to threats to increase species resilience. We suggest that targeted gene flow is a currently underappreciated strategy in conservation that has applications ranging from the management of invasive species and their impacts to controlling the impact and virulence of pathogens.

A case study of bats and white-nose syndrome demonstrating how to model population viability with evolutionary effects.

Ecological factors generally affect population viability on rapid time scales. Traditional population viability analyses (PVA) therefore focus on alleviating ecological pressures, discounting potential evolutionary impacts on individual phenotypes. Recent studies of evolutionary rescue (ER) focus on cases in which severe, environmentally induced population bottlenecks trigger a rapid evolutionary response that can potentially reverse demographic threats. ER models have focused on shifting genetics and resulting population recovery, but no one has explored how to incorporate those findings into PVA. We integrated ER into PVA to identify the critical decision interval for evolutionary rescue (DIER) under which targeted conservation action should be applied to buffer populations undergoing ER against extinction from stochastic events and to determine the most appropriate vital rate to target to promote population recovery. We applied this model to little brown bats (Myotis lucifugus) affected by white-nose syndrome (WNS), a fungal disease causing massive declines in several North American bat populations. Under the ER scenario, the model predicted that the DIER period for little brown bats was within 11 years of initial WNS emergence, after which they stabilized at a positive growth rate (λ = 1.05). By comparing our model results with population trajectories of multiple infected hibernacula across the WNS range, we concluded that ER is a potential explanation of observed little brown bat population trajectories across multiple hibernacula within the affected range. Our approach provides a tool that can be used by all managers to provide testable hypotheses regarding the occurrence of ER in declining populations, suggest empirical studies to better parameterize the population genetics and conservation-relevant vital rates, and identify the DIER period during which management strategies will be most effective for species conservation.

Un Estudio de Caso sobre Murciélagos y el Síndrome de Nariz Blanca que Demuestra cómo Modelar la Viabilidad Poblacional con Efectos Evolutivos Resumen Los factores ecológicos afectan generalmente a la viabilidad poblacional en escalas rápidas de tiempo. Por esto los análisis tradicionales de viabilidad poblacional (AVP) se enfocan en aliviar las presiones ecológicas, lo que discontinúa los impactos evolutivos potenciales sobre los fenotipos individuales. Los estudios recientes del rescate evolutivo (RE) se enfocan en casos en los que cuellos de botella poblacionales inducidos por el ambiente disparan una respuesta evolutiva rápida, la que puede revertir potencialmente las amenazas demográficas. Los modelos de rescate evolutivo se han enfocado en la genética cambiante y la recuperación poblacional resultante, pero nadie ha explorado cómo incorporar estos hallazgos en los AVP. Integramos el RE a los AVP para identificar el intervalo de decisión crítica para el rescate evolutivo (IDRE), bajo el cual se deben aplicar las acciones de conservación enfocada para amortiguar a las poblaciones sometidas a RE ante la extinción por eventos estocásticos, y para determinar la tasa vital más apropiada para promover la recuperación de la población. Aplicamos este modelo a los pequeños murciélagos cafés (Myotis lucifugus) afectados por el síndrome de nariz blanca (SNB), una enfermedad micótica que causa declinaciones masivas en varias poblaciones norteamericanas de murciélagos. Bajo el escenario de RE, el modelo predijo que el periodo de IDRE para estos murciélagos estaba dentro de once años del surgimiento inicial del síndrome, después del cual se estabilizaban a una tasa positiva de crecimiento (λ = 1.05). Al comparar nuestros resultados del modelo con las trayectorias poblacionales de múltiples sitios de hibernación infectados a lo largo de la extensión del SNB, concluimos que el RE es una explicación potencial de las trayectorias observadas de pequeños murciélagos cafés a lo largo de múltiples sitios de hibernación dentro de la extensión afectada. Nuestra estrategia proporciona una herramienta que puede ser usada por todos los manejadores para proporcionar hipótesis comprobables con respecto a la aparición del RE en las poblaciones declinantes, sugerir estudios empíricos que mejoren los parámetros de la genética de poblaciones y las tasas vitales relevantes para la conservación, y para identificar el periodo IDRE durante el cual las estrategias de manejo serán más efectivas para la conservación de la especie.

Lesión tumoral músculo-esquelética de evolución rápida: a propósito de un caso / Lesion skeletal tumoral muscle of quick evolution: a purpose of a case

El Fibrosarcoma es un tumor maligno de partes blandas primario o secundario a lesiones benignas pre-existentes, pueden ser endostal o parostal, comprende aproximadamente el 6.2 por ciento de los tumores primarios del hueso, predomimante en hombres, entre la 3era y 6ta década de vida, tiene predilección por el fémur, húmero, tibia y pelvis. Se describe paciente masculino de 25 años de edad quien inicia enfermedad en noviembre 2002 con aumento de volumen progresivo y dolor en rodilla derecha, acompañandose de limitación funcional; consulta en mayo 2003 con clínica exacerbada iniciándose su estudio.