Abstract
Little is known about the successional dynamics of insects in the highly threatened tropical dry forest (TDF) ecosystem. For the first time, we studied the response of carabid beetles to vegetal succession and seasonality in this ecosystem in Colombia. Carabid beetles were collected from three TDF habitat types in two regions in Colombia: initial successional state (pasture), early succession, and intermediate succession (forest). The surveys were performed monthly for 13 months in one of the regions (Armero) and during two months, one in the dry and one in the wet season, in the other region (Cambao). A set of environmental variables were recorded per month at each site. Twenty-four carabid beetle species were collected during the study. Calosoma alternans and Megacephala affinis were the most abundant species, while most species were of low abundance. Forest and pasture beetle assemblages were distinct, while the early succession assemblage overlapped with these assemblages. Canopy cover, litter depth, and soil and air temperatures were important in structuring the assemblages. Even though seasonality did not affect the carabid beetle assemblage, individual species responded positively to the wet season. It is shown that early successional areas in TDF could potentially act as habitat corridors for species to recolonize forest areas, since these successional areas host a number of species that inhabit forests and pastures. Climatic variation, like the El Niño episode during this study, appears to affect the carabid beetle assemblage negatively, exasperating concerns of this already threatened tropical ecosystem.
Highlights
Tropical dry forest (TDF) is considered the most threatened tropical ecosystem in South America and Africa (Janzen 1988; Miles et al 2006) and is simultaneously one of the lesser-known ecologically (Sánchez-Azofeifa et al 2005)
The study was performed in the tropical dry forest biome in the Valley of the Magdalena River region (Colombia), in the municipalities of Armero-Tolima (305 m a.s.l.) and Cambao-Cundinamarca (294 m a.s.l.), both of which consist of a matrix of forest, pasture, and crops (Fig. 1)
Calosoma alternans (Fabricius) and Megacephala affinis Dejean were the most abundantly collected species (113 and 21 individuals respectively), C. alternans occurring in all habitat types while M. affinis was not present in forest
Summary
Tropical dry forest (TDF) is considered the most threatened tropical ecosystem in South America and Africa (Janzen 1988; Miles et al 2006) and is simultaneously one of the lesser-known ecologically (Sánchez-Azofeifa et al 2005). An example is TDF in the Valley of the Magdalena River in Colombia, which has experienced intensive agriculture resulting in a heterogeneous landscape (FernándezMéndez et al 2014), with most forest patches reduced to less than 30 ha in size (Pizano et al 2016). This landscape mosaic is characterized by areas at various stages of succession, similar to other countries (Quesada et al 2009), which generate potential sources for spontaneous succession (Prach 2003). The application of conservation strategies and ecological restoration is of paramount importance (Vargas and Ramírez 2014), especially since TDF succession is slow compared to wet tropical forest (Murphy and Lugo 1986), because water is a limiting factor when it comes to recovery (Fajardo et al 2013)
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