Population ecology of the orb-weaver spider Eustala taquara (Keyserling) (Araneidae)

ABSTRACT

The density and age structure of spider populations are affected by biotic and abiotic factors. The orb-web spider Eustala taquara (Araneidae) lives camouflaged on the dead vegetation of shrubs, especially in forest edges. Here, we describe the variation in the number of individuals over the year and the phenology of a population of E. taquara. We also tested whether these variables are influenced by temperature, precipitation or prey availability. We conducted the research in a tropical rainforest located in south-eastern Brazil. We recorded the number of spiders and their development stages (spiderling, young, juvenile, sub-adult and adult) monthly, for two years, along 1 km at the forest edge at an altitude of 1000 m above sea level. We estimated prey availability using 20 circular transparent plates containing tanglefoot on one side, exposed for 48 hours in the vegetation, sampled monthly for 18 months. We used circular statistics to assess the peaks of individuals during the study period, verifying the occurrence of time lags between the number of spiders with the climatic variables and prey availability. The population of E. taquara increased in periods of lower precipitation and temperature, and decreased during the rainy season. Thus, the population showed a negative correlation with the climatic variables and potential prey availability. All instars were present simultaneously, revealing that spiders can reproduce at any time of year. During the dry season, the higher number of spiders may be related to the increase in branches and dead plants that provide camouflage against visually oriented predators and sites for web building, increasing the likelihood of obtaining food.

KEYWORDS:

• population density
• phenology
• prey availability
• sex ratio

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (proc. 2011/15456-4); Conselho Nacional de Desenvolvimento Científico e Tecnológico (proc. 310477/2020-4); Fundação de Apoio à Pesquisa do Estado de Minas Gerais (APQ-02984-17); and Instituto Nacional de Ciência e Tecnologia dos Hymenoptera Parasitoides da Região Sudeste (INCT-HYMPAR/SUDESTE) (CNPq, FAPESP, CAPES).