Araneae Biodiversity in the Ecuadorian Chocó: Impact of Altitude and Land Use on Spider Diversity

Abstract

In the neotropical cloud forests, spiders are severely understudied despite their diversity, importance as bioindicators, and threats facing their habitat. The Tumbes-Chocó-Magdalena bioregion in the Ecuadorian Andes is one of the most biodiverse areas in the world. This ecosystem is threatened by agricultural deforestation and climate change that disproportionately affect mountainous biomes. The objectives of this study were to investigate 1) which spider genera are found within the private reserve, La Hesperia Reserva Natural; 2) how elevation affects spider diversity; and 3) how land use affects spider diversity. Four nocturnal visual transects (150m long) at three elevations were sampled via macro-photography. Over 12 days, 1,318 individuals in 16 families, 33 genera, and 188 morphospecies were identified. The most abundant families were Theridiidae (n=624, 47.2%), Araneidae (n=322, 24.4%), and Ctenidae (n=87, 6.6%). Families were assigned to guilds based on hunting strategy. The orb web guild (Araneidae, Tetragnathidae, Uloboridae, Synotaxidae) was most diverse while the space web guild (Theridiidae, Pholcidae) was most abundant but one of the least diverse due to the disproportionate abundance of one subsocial species in the Theridion genus. The transect with mild land use was the most diverse possibly due to more complex vegetation, however, this is not definitive due to lack of replicates. This study established a baseline spider biodiversity survey of La Hesperia Reserva Natural, and the findings support the hypotheses that spider diversity is found to generally decrease with increasing elevation, and subsocial spiders are found to be more common at higher elevations.