Genetic Structure, Nestmate Recognition and Behaviour of Two Cryptic Species of the Invasive Big-Headed Ant Pheidole megacephala

Abstract

BackgroundBiological invasions are recognized as a major cause of biodiversity decline and have considerable impact on the economy and human health. The African big-headed ant Pheidole megacephala is considered one of the world's most harmful invasive species.Methodology/Principal FindingsTo better understand its ecological and demographic features, we combined behavioural (aggression tests), chemical (quantitative and qualitative analyses of cuticular lipids) and genetic (mitochondrial divergence and polymorphism of DNA microsatellite markers) data obtained for eight populations in Cameroon. Molecular data revealed two cryptic species of P. megacephala, one inhabiting urban areas and the other rainforests. Urban populations belong to the same phylogenetic group than those introduced in Australia and in other parts of the world. Behavioural analyses show that the eight populations sampled make up four mutually aggressive supercolonies. The maximum distance between nests from the same supercolony was 49 km and the closest distance between two nests belonging to two different supercolonies was 46 m. The genetic data and chemical analyses confirmed the behavioural tests as all of the nests were correctly assigned to their supercolony. Genetic diversity appears significantly greater in Africa than in introduced populations in Australia; by contrast, urban and Australian populations are characterized by a higher chemical diversity than rainforest ones.Conclusions/SignificanceOverall, our study shows that populations of P. megacephala in Cameroon adopt a unicolonial social structure, like invasive populations in Australia. However, the size of the supercolonies appears several orders of magnitude smaller in Africa. This implies competition between African supercolonies and explains why they persist over evolutionary time scales.

Body size variation and caste ratios in geographically distinct populations of the invasive big-headed ant,Pheidole megacephala(Hymenoptera: Formicidae)

“…We chose P. megacephala because it has successfully invaded a wide range of geographical locations (Wetterer, , ) where different populations experience dramatically different ecological conditions. The native range of P. megacephala has not yet been determined although it is suspected to be from Africa (Ethiopian region) or Madagascar due to the richness of the megacephala species complex from these regions (Wheeler, ; Wetterer, , ; Fischer, Garcia & Peters, ; Fournier et al ., ; Fischer & Fisher, ). We collected workers of P. megacephala from five geographically distinct populations that vary considerably in terms of species richness within the ant community: Northern Territory, Australia; Hawaii, USA; Florida, USA; Sabi Sands, South Africa; and Mauritius (Table ).…”

“…In addition to the new sequence data collected for 33 new specimens, we incorporated 56 additional relevant sequences generated for other studies (Moreau, ; Smith & Fisher, ; Fournier et al ., ) for a total of 89 taxa included in this study (Table ). After sequence data were collected they were analysed and initially aligned using the computer program Geneious v6.1.2 (Drummond et al ., ).…”

High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence

“…However, estimates of species richness are often impaired by the occurrence of cryptic species (i.e. species that are impossible or difficult to distinguish based on their morphology) in diverse groups such as protists (Foissner, 2006), ants (Fournier et al, 2012), harvestmen (Arthofer et al, 2013), and rotifers (Gómez & Snell, 1996). Understanding how and why species occur is one of the fundamental aspects in ecology (Gaston, 2000).…”

Life history traits and demographic parameters in the Keratella cochlearis (Rotifera, Monogononta) species complex

“…With the advent of molecular techniques and the introduction of DNA taxonomy, many rotifer species, traditionally considered as one species, proved to be complexes of cryptic species. Cryptic species, defined as genetically distinct but morphologically difficult-to-distinguish species (Gomez et al, 2002;Fontaneto et al, 2009;Birky et al, 2011;Obertegger et al, 2012Obertegger et al, , 2014Cieplinski et al, 2017), appear to be widespread among both microorganisms and macroorganisms and have been reported in many groups such as protists (Foissner, 2006), ants (Fournier et al, 2012), harvestmen (Arthofer et al, 2013), and rotifers (Gomez & Snell, 1996;Gomez et al, 2002;Fontaneto et al, 2009;Birky et al, 2011;Obertegger et al, 2012Obertegger et al, , 2014Cieplinski et al, 2017). According to the niche conservatism theory, the closer the related species are, the more profound is their niche conservatism (i.e., a higher tendency to retain their ancestral traits) and the stronger is their competition (e.g., Darwin, 1859;Violle et al, 2011).…”