Reproductive isolation and sex-role reversal in two sympatric sand-dwelling wolf spiders of the genus Allocosa

Abstract

Allocosa brasiliensis (Petrunkevitch, 1910) is a nocturnal wolf spider inhabitant of coastal dunes. Pitfall-trap data suggested the occurrence of two sympatric and synchronic morphs, with differences in adult size and abdominal design (minor and major morphs). Previous studies performed with the major morph of A. brasiliensis, postulated courtship-role and sexual size dimorphism reversal for this spider. In the present study, we compare data on development and morphology and test reproductive isolation between morphs of A. brasiliensis, with the hypotheses that the two morphs are reproductively isolated and both show courtship-role reversal. As had been reported for the major morph of A. brasiliensis, the minor-morph females approached the burrows of minor-morph males, entered, initiated courtship, and after copulation, males closed their burrows with female cooperation from the inside. Females did not court or copulate with males belonging to the other morph and, in two cases, major-morph females cannibalised minor-morph males. Morphometrical and developmental data showed differences between morphs. The occurrence of copulation only between individuals of the same morph confirm reproductive isolation, supporting the occurrence of two species. Morphological and behavioural data are consistent with courtship-role-reversal hypotheses for the minor morph, constituting the second report in spiders of this atypical behaviour.

Habitat Preference and Effects of Coastal Fragmentation in the Sand-Dwelling Spider <i>Allocosa brasiliensis</i> (Lycosidae, Allocosinae)

“…In all the beaches, females were more abundant than males and they were the sex with higher recaptures ( Table 1, Table 6). This is in agreement with the sex-role reversal reported for this species [30] [31], and consequent higher mobility in this sex. Also, females of A. brasiliensis need to forage intensively before mating because after that they will remain buried in male burrows, ovipositing there and exiting for spiderling dispersal, approximately one month later [18] [29] [31].…”

“…This period was chosen because it coincided with the reproductive season where the species presents the highest surface activity [28] [30] [31]. Due to its crepuscular habits, we performed night samplings with visual detection of the exemplars by using head lamps.…”

Characterisation of burrow architecture under natural conditions in the sand-dwelling wolf spider Allocosa brasiliensis

“…Females reach maturity after 9.44 ± 1.01 moults and males after 9.83 ± 1.11 moults (Aisenberg and Costa 2008). Females and males mature in November-December and survive for two reproductive periods (1 year; Aisenberg and Costa 2008). This species shows a reversal in typical sex roles and expected sexual size dimorphism described for spiders (Aisenberg et al 2007).…”

“…During daylight, individuals stay inside their burrows, and they turn active during the night, when they forage and reproduce (Aisenberg 2014). Females reach maturity after 9.44 ± 1.01 moults and males after 9.83 ± 1.11 moults (Aisenberg and Costa 2008). Females and males mature in November-December and survive for two reproductive periods (1 year; Aisenberg and Costa 2008).…”

Handicap principle implies emergence of dimorphic ornaments

“…[24][25][26]). Figure 1 illustrates a classic example of ornament dimorphism, the horned dung beetle [24].…”