Strong phenological differences between two populations of a Neotropical funnel-web wolf spider

Abstract

Comparisons of phenological patterns among populations within a species are uncommon in arachnids. Aglaoctenus lagotis is a wolf spider that lives in funnelwebs across South America. The aim of this study was to describe the phenological patterns of two distant populations of A. lagotis (central Argentina, CA, and southern Uruguay, SU). Individuals of each population were sighted along transects, every month for two years. The CA and SU populations differed in their phenological patterns (Wald χ 2 = 966.94, df = 66; p <0.001). The CA population showed a spring-summer unified reproductive season and immature individuals overwintered. SU showed the sexual period during autumn, the maternal period during spring-summer and the females, mostly mated, overwintered. These strong differences imply temporal isolation in mating possibilities between both populations. The differences encountered could be due to phenotypic plasticity or have a phylogenetic basis. Interpopulation studies of other features of A. lagotis would show whether they also vary, suggesting speciation.

Funnel-web construction and estimated immune costs inAglaoctenus lagotis(Araneae: Lycosidae)

“…We chose this locality because both forms of the species, reported by Gonzá lez et al (2014) (''similar to SU'' form and ''similar to CA'' form), are present. Collecting at different periods of the year was done to ensure finding subadults of both forms because they present different phenologies (Gonzá lez et al 2014). Individuals were captured from their webs during daylight, by manually blocking the entrance of the silk tube.…”

“…The species is widely distributed, from Uruguay to Colombia (Piacentini 2011), being present in different environments (Sordi 1996;Santos & Brescovit 2001). The existence of two forms has been reported within the species, differing from each other at least in sexual behavior (Gonzá lez et al 2013) and phenology (Gonzá lez et al 2014), suggesting a divergence process (Gonzá lez et al 2015). One of the forms (the ''similar to southern Uruguay, SU'') constructs its webs exclusively on the herbaceous stratum, and the other (the ''similar to central Argentina, CA'') can construct them also on the arbustive and arboreal strata (Gonzá lez et al 2014).…”

Reproductive isolation between two populations ofAglaoctenus lagotis, a funnel-web wolf spider

“…We chose three localities (environmental characteristics given in González et al ., ) for collecting adult and subadult individuals of A. lagotis : Piedras de Afilar, Canelones, southern Uruguay (SU: 34°43′44″S, 55°30′46″W) and Sierras Chicas, western Córdoba, central Argentina (CA: 30°57′10″S, 64°15′28″W) as the two distant localities, and Fray Bentos, Rio Negro, western Uruguay bordering with Argentina (WU: 33°06′45″S, 58°17′11″W) as the third locality, geographically intermediate to the previous locations, where the distribution of the two populations overlap (Fig. ).…”

“…Copulation occurs with the male mounted on the female dorsum and opposite to her (the typical copulating position for all lycosid spiders), and males performed several ejaculations per insertion of their palps, which differed in duration and frequency between southern Uruguay and central Argentina individuals (González et al ., ). Additionally, a later study showed that those distant populations present marked differences in their phenological patterns, so much so that sexual periods occur in different seasons (González, Costa & Peretti, ). Individuals also seemed to differ in body‐pigmentation patterns (M. González, unpubl.…”

“…(), whereas no preferences based on silk cues are expected (as shown for other spiders by Barth & Schmitt, ). However, bearing in mind the differences encountered in previous studies (González et al ., , ), the intraspecific variation could not be homogeneously distributed, putting in doubt a single‐species hypothesis for A. lagotis . This study sheds light on the controversial taxonomic history of this subfamily of spiders and the speciation processes involved in these sedentary web‐living members of a family of wandering spiders.…”