Tropical Ecology and Conservation [Monteverde Institute]

Alternative Title

Abundancia de población, expresión sexual y proporciones de género de Marchantia sp. a lo largo de un gradiente altitudinal en Monteverde, Costa Rica


Laura Garrison



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Publication Date

May 2007


Fisher’s theory on sex ratios states that a 1:1 ratio of males to females typically will result when both sexes are equally expensive to produce. Many bryophytes, however, tend to express female sex biases. I took two population censuses of Marchantia sp. during dry season and the transition from wet to dry season along the Sendero Principal in Monteverde, Costa Rica, to determine population abundance and sex ratios. Elevation did not significantly correlate with population abundance (Spearman rank correlation census one: rho = -0.213, P = 0.372; census two: rho = -0.118, P = 0.409). I found local female proportions to vary at different sites in both censuses (Chi-squared test for independence census one: χ2 = 175.861, df = 7, P < 0.0001; census 2: χ2 = 292.349, df = 7, P < 0.0001) and, although non-significant, I noticed a trend towards increasing gemmae presence with elevation in census two (Spearman rank correlation rho = 0.405, P = 0.28). Finally, I found a strong female meta-population bias to become more pronounced as the rainy season progressed. Small dispersal ranges of Marchantia sp. are likely preventing higher abundance; its ability to colonize an area can be attributed more to micro-habitat resource availability than elevational conditions, although trends of gemmae increase are likely due to stable moist conditions at high elevations. Marchantia sp. may display a higher proportion of females in the meta- and local populations due to higher male nutrient requirements, prompting local mate competition to act between males for limited resources in micro-habitats. La teoría de Fisher sobre la proporción de sexos indica que una proporción de 1:1 de los varones a las hembras cuando ambos sexos son igualmente caros para producir. Sin embargo, muchos briofitos tienden a expresar sesgo hacia la expresión femenina del sexo. Hice dos censos de la población de una especie de Marchantia durante la estación seca y de la transición de la estación seca a la estación lluviosa, cerca del Sendero Principal en Monteverde, Costa Rica para determinar la abundancia de la población y las proporciones de los sexos.


Bryophytes, Briofitas, Marchantia, Environmental impact analysis, Analisis de impacto ambiental, Costa Rica--Puntarenas--Monteverde Zone, Costa Rica--Puntarenas--Zona de Monteverde, CIEE Spring 2007, CIEE Primavera 2007


Student affiliation : Department of Biology, Northern Michigan University Born Digital

Subject: topical

Bryophytes; Briofitas; Marchantia; Environmental impact analysis; Analisis de impacto ambiental; CIEE Spring 2007; CIEE Primavera 2007

Subject: geographic

Costa Rica--Puntarenas--Monteverde Zone; Costa Rica--Puntarenas--Zona de Monteverde



Holding Location

Monteverde Institute MVI



Population abundance, sexual expression, and gender ratios of Marchantia sp. along  an elevational gradient in Monteverde, Costa Rica



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