Composición y estructura en agregaciones de moluscos terrestres en el Complejo de vegetación de mogote, Escaleras de Jaruco, Cuba / Structure and composition of terrestrial molluscs assemblages on the mogote vegetation complex of Escaleras de Jaruco, Cuba

ABSTRACT

Cuba has one of the richest land snail faunas of the world. This important fact has promoted different kind of studies on this group to promote conservation programs, from which many studies have directed their efforts to inventories, and population and community ecology. To contribute with this population knowledge, we studied land snails assemblages in three karstic elevations at the “Escaleras de Jaruco-Tapaste-Cheche” Natural Protected Landscape, Mayabeque, Cuba. We aimed to analyze the variation of the composition and structure of the assemblages between the rainy and little rainy months. The study was conducted from August to November 2009 and from January to April, 2010, in ten permanent square plots (9m²) separated for over 20m, on each elevation (Beluca, La Chirigota and La Jaula). In each plot, only live individuals were registered (physiologically active and at rest) to obtain species richness and abundance; besides, temperature (ºC) and relative humidity (%) were also considered in each plot. A total of 4 248 individuals were observed which comprised two subclasses, five orders, 11 families, 20 genera and 21 species of terrestrial molluscs. From the total, 19 were Cuban endemics and eight were exclusive from Mayabeque, Matanzas. The Jaula showed the greater riches with 19 species, followed of Beluca with 17, and The Chirigota with 15. In the rainy months, La Jaula, showed individual’s greater abundance with 1 707, followed of Beluca with 1 305 and La Chirigota with 1 236. We observed differences in the population density in the three elevations between the rainy and little rainy months, which can be due to the climatic adverse conditions that are shown at the little rainy months. Additionally, during the survey we observed dominance of prosobranch species over the pulmonates. The specific abundance curves showed a steep slope, although was major in the rainy months in relation to the little rain months, which indicates the presence of dominant, common and rare species in the assemblages. In this study, it was demonstrated than the riches and the abundance of land snails in all three elevations, was favored for the elevated relative humidity and the air temperature during the rainy months. These environmental conditions resulted fundamental for the survival of these terrestrial gastropods, as the reproduction and search of food were favored.

RESUMEN

Estudiamos las agregaciones de moluscos terrestres de tres elevaciones cársicas en el Paisaje Natural Protegido “Escaleras de Jaruco-Tapaste-Cheche”, Mayabeque, Cuba. Se analizaron las variaciones de la composición y la estructura de las agregaciones entre los meses lluviosos y poco lluviosos. El estudio fue realizado desde agosto a noviembre 2009 y entre enero y abril 2010 en diez parcelas cuadradas permanentes (9m²) en cada elevación. En cada parcela se registraron solamente los individuos vivos (fisiológicamente activos y en reposo), el estudio fue de observación/trabajo de campo. Dentro de cada parcela se registró la riqueza de especie y abundancia. En cada parcela se midió la temperatura (°C) y la humedad relativa (%), se observaron 4 248 individuos de dos subclases, cinco órdenes, 11 familias, 20 generos y 21 especies de moluscos terrestres; 19 son endémicos cubanos y ocho de ellos lo son de la región Mayabeque-Matanzas. Se observaron diferencias entre los meses lluviosos y poco lluviosos en la densidad poblacional entre las tres elevaciones, lo cual puede deberse a las condiciones climáticas adversas en los meses poco lluviosos. Durante los meses muestreados se detectó una dominancia de las especies operculadas sobre las pulmonadas. Las curvas de rango-abundancia se caracterizaron por tener una pendiente pronunciada, lo cual indica la presencia de especies dominantes, comunes y raras en las agregaciones.