Structure and genetic variability of the Costa Rican Paso horse.

The Costa Rican Paso Horse (CPC) is a breed developed in Costa Rica. The objectives were to estimate the genetic structure and evaluate the levels of genetic variability of the population. The genotypes of 14 microsatellites in 3654 records (2052 females and 1602 males) were analyzed. Expected (He) and observed (Ho) heterozygosity, polymorphic information content (CIP), fixation index (FIS), Shannon index, as well as Hardy-Weinberg disequilibrium (DHW) were evaluated. Kinship relationships (Rij) were estimated throughout the entire population. The effective population size (Ne) was calculated, alternating allele frequencies less than 0.05, 0.02 and 0.01. The Bayesian clustering study was carried out to infer how many lines are appropriate from the analysis of genotypes using multiple loci. The number of alleles per locus ranged from 7 to 17, with an average value of 9.6; nine loci presented DHW (P < 0.05); two loci presented negative FIS values, the same as Ho > He; the average of CIP, Ho and He was 0.254, 0.756 and 0.785, respectively. At the 12 loci where He > Ho, the differences ranged from 0.002 to 0.341 (0.036 on average). For Ne, the estimates were 201.9, 230.1, and 241.5. In the Rij, 54.86% of the estimates were in the interval of 0.01 to 77.7%. The number of lines that define the population corresponds to three, with an approximate composition of 33.1%, 32.4% and 34.5%, respectively. The CPC, as a subdivided population with DHW and a reduction in heterozygotes may be associated with possible Wahlund effects. Keywords: Wahlund effect, equines, genetic markers, synthetic breed, Hardy Weinberg.

Effectiveness of two treatments to promote tree regeneration: implications for forest restoration in the Isla del Coco National Park, Costa Rica

Introduction: Isla del Coco is the only island in the Eastern Tropical Pacific with humid tropical forests; 296 plant species are reported, of them, 22% are endemic. Their ecology is poorly understood. Deforestation and the introduction of rats, feral pigs and white-tailed deer are the primary agents of forest degradation. After more than 120 years, the deforested areas have never recovered the native forest. Objective: To analyse if the deforested area keeps its resilience, we evaluated the natural regeneration and ecological processes associated. Methods: From August 2016 to June 2018, we conducted a restoration experiment consisting of a randomized complete blocks design including vegetation cutting, vegetation uprooting and controls as treatments. Plots were protected with an exclusion fence to avoid herbivores. Results: There were no differences between plant cutting and uprooting in stimulating natural regeneration. We only recorded the seedlings of two tree species, 35 individuals of Cecropia pittieri and three of Sacoglottis holdridgei, both endemic. Their regeneration established during the first 15 months mainly. At the end of the experiment, the structure and composition of the vegetation changed from bushes dominated by Entada gigas (28%) and Clidemia strigillosa (12%) to grasses dominated by Paspalum conjugatum (39%). Entada gigas has a high recolonizing potential with a growing rate of 1.6±0.2m/month. Conclusions: As filters for restoration we determined herbivores, which pose a strong negative impact in the development of the forest; the exhausted seed bank of tree species and scarce or null seed dispersion.

Introducción: Isla del Coco es la única isla en el Pacífico oriental con bosques tropicales húmedos, albergando 296 especies de plantas, de las cuales un 22% son endémicas. De su ecología se conoce muy poco. El bosque fue degradado con la introducción de cerdos y venados cola blanca y por deforestación. Las áreas deforestadas hace más de 120 años nunca recuperaron el bosque nativo. Objetivo: Para analizar si el área deforestada mantiene su capacidad de recuperación, se evaluó la regeneración natural y los procesos ecológicos asociados. Metodología: Desde agosto de 2016 hasta junio de 2018, se monitoreó un ensayo de restauración, establecido como un diseño de bloques completos al azar. Los tratamientos incluyeron corte de vegetación, arranque de vegetación y controles. Se utilizó una cerca de exclusión para evitar los herbívoros. Resultados: No hubo diferencias en los tratamientos de corte y arranque de la vegetación para estimular la regeneración natural. Se registró la regeneración de dos especies de árboles: 35 individuos de Cecropia pittieri y tres de Sacoglottis holdridgei, ambas endémicas. La regeneración se estableció principalmente en los primeros 15 meses. Luego de aplicados los tratamientos, la estructura y composición de la vegetación cambió de arbustos dominados por Entada gigas (28%) y Clidemia strigillosa (12%), a pastos dominados por Paspalum conjugatum (39%). Entada gigas tiene el mayor potencial de recolonización por su tasa de crecimiento de 1.6±0.2m/mes. Conclusiones: Los filtros determinados asociados con la regeneración del bosque son los herbívoros; el banco de semillas de las especies arbóreas agotado y la dispersión de semillas escasa o nula, según la especie.

Asociación entre variables: correlación no paramétrica

Se describe la forma de estimar el coeficiente de correlación de Spearman y las condiciones en que resulta apropiada su utilización. También se describe como realizar una prueba de hipótesis para determinar si el coeficiente estimado es significativamente distinto de cero.