When GIS zooms in: spatio-genetic maps of multipaternity in Armadillidium vulgare

Abstract

Geographic information system (GIS) tools are designed to illustrate, analyse and integrate geographic or spatial data, usually on a macroscopic scale. By contrast, genetic tools focus on a microscopic scale. Because in reality, landscapes have no predefined scale, our original study aims to develop a new approach, combining both cartographic and genetic approaches to explore microscopic landscapes. For this, we focused on Armadillidium vulgare, a terrestrial isopod model in which evolutionary pressures imposed by terrestrial life have led to the development of internal fertilisation and, consequently, to associated physiological changes. Among these, the emergence of internal receptacles, found in many taxa ranging from mammals to arthropods, allowed females to store sperm from several partners, enabling multipaternity. Among arthropods, terrestrial isopods like the polygynandrous A. vulgare present a female structure, the marsupium, in which fertilised eggs migrate and develop into mancae (larval stage). To test our innovative combined approach, we proposed different males to four independent females, and at the end of incubation in the marsupium, we mapped (using GIS methods) and genotyped (using 12 microsatellite markers) all the incubated mancae. This methodology permitted to obtain spatio-genetic maps describing heterozygosity and spatial distribution of mancae and of multipaternity within the marsupial landscape. We discussed the interest of this kind of multidisciplinary approach which could improve in this case our understanding of sexual selection mechanisms in this terrestrial crustacean. Beyond the interesting model-focused insights, the main challenge of this study was the transfer of GIS techniques to a microscopic scale and our results appear so as pioneers rendering GIS tools available for studies involving imagery whatever their study scale.

Fine-scale population structure analysis in Armadillidium vulgare (Isopoda: Oniscidea) reveals strong female philopatry

“…The sex-biased dispersal observed in this study could thus be an additional mechanism allowing avoiding costly inbreeding in this species. On the other hand, because females incubate their offspring in a ventral pouch for one month (Bech et al, 2017) and bear significant costs upon locomotion (Kight & Ozga, 2001, Suzuki & Futami, 2018 and likely food intake (Appel et al, 2011), our results are also in line with the predictions of the handicap hypothesis proposed by Trochet et al (2016).…”

“…Here we propose to test for sex-biased dispersal in the terrestrial isopod Armadillidium vulgare. In this crustacean, females display important maternal care by incubating their offspring during one month in a ventral pouch to allow their development (Bech et al, 2017), leading to high costs for females (Kight & Ozga, 2001;Appel et al, 2011). Females usually produce two to three broods per year between April and October (Vandel, 1962).…”

High Exploration Behavior of Termite Propagules Can Enhance Invasiveness

“…Pictures of the two-glass systems for each time were implemented as raster files. The RGF93/Lambert93 EPSG:2154 coordinate system was derived to scale the pictures (Bech et al, 2017). The spatial distribution was analyzed, using a point shape (on the neck) to spot each forager (individual dispersed away from the introduction area), as well as to calculate the shortest distance between foragers.…”