Spatial Distribution of Dominant Arboreal Ants in a Malagasy Coastal Rainforest: Gaps and Presence of an Invasive Species

We conducted a survey along three belt transects located at increasing distances from the coast to determine whether a non-random arboreal ant assemblage, such as an ant mosaic, exists in the rainforest on the Masoala Peninsula, Madagascar. In most tropical rainforests, very populous colonies of territorially dominant arboreal ant species defend absolute territories distributed in a mosaic pattern. Among the 29 ant species recorded, only nine had colonies large enough to be considered potentially territorially dominant; the remaining species had smaller colonies and were considered non-dominant. Nevertheless, the null-model analyses used to examine the spatial structure of their assemblages did not reveal the existence of an ant mosaic. Inland, up to 44% of the trees were devoid of dominant arboreal ants, something not reported in other studies. While two Crematogaster species were not associated with one another, Brachymyrmex cordemoyi was positively associated with Technomyrmex albipes, which is considered an invasive species—a non-indigenous species that has an adverse ecological effect on the habitats it invades. The latter two species and Crematogaster ranavalonae were mutually exclusive. On the other hand, all of the trees in the coastal transect and at least 4 km of coast were occupied by T. albipes, and were interconnected by columns of workers. Technomyrmex albipes workers collected from different trees did not attack each other during confrontation tests, indicating that this species has formed a supercolony along the coast. Yet interspecific aggressiveness did occur between T. albipes and Crematogaster ranavalonae, a native species which is likely territorially dominant based on our intraspecific confrontation tests. These results suggest that the Masoala rainforest is threatened by a potential invasion by T. albipes, and that the penetration of this species further inland might be facilitated by the low density of native, territorially dominant arboreal ants normally able to limit its progression

Disease Dynamics in a Specialized Parasite of Ant Societies

Coevolution between ant colonies and their rare specialized parasites are intriguing, because lethal infections of workers may correspond to tolerable chronic diseases of colonies, but the parasite adaptations that allow stable coexistence with ants are virtually unknown. We explore the trade-offs experienced by Ophiocordyceps parasites manipulating ants into dying in nearby graveyards. We used field data from Brazil and Thailand to parameterize and fit a model for the growth rate of graveyards. We show that parasite pressure is much lower than the abundance of ant cadavers suggests and that hyperparasites often castrate Ophiocordyceps. However, once fruiting bodies become sexually mature they appear robust. Such parasite life-history traits are consistent with iteroparity– a reproductive strategy rarely considered in fungi. We discuss how tropical habitats with high biodiversity of hyperparasites and high spore mortality has likely been crucial for the evolution and maintenance of iteroparity in parasites with low dispersal potential

Higher Level Phylogeny and the First Divergence Time Estimation of Heteroptera (Insecta: Hemiptera) Based on Multiple Genes

Heteroptera, or true bugs, are the largest, morphologically diverse and economically important group of insects with incomplete metamorphosis. However, the phylogenetic relationships within Heteroptera are still in dispute and most of the previous studies were based on morphological characters or with single gene (partial or whole 18S rDNA). Besides, so far, divergence time estimates for Heteroptera totally rely on the fossil record, while no studies have been performed on molecular divergence rates. Here, for the first time, we used maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) with multiple genes (18S rDNA, 28S rDNA, 16S rDNA and COI) to estimate phylogenetic relationships among the infraorders, and meanwhile, the Penalized Likelihood (r8s) and Bayesian (BEAST) molecular dating methods were employed to estimate divergence time of higher taxa of this suborder. Major results of the present study included: Nepomorpha was placed as the most basal clade in all six trees (MP trees, ML trees and Bayesian trees of nuclear gene data and four-gene combined data, respectively) with full support values. The sister-group relationship of Cimicomorpha and Pentatomomorpha was also strongly supported. Nepomorpha originated in early Triassic and the other six infraorders originated in a very short period of time in middle Triassic. Cimicomorpha and Pentatomomorpha underwent a radiation at family level in Cretaceous, paralleling the proliferation of the flowering plants. Our results indicated that the higher-group radiations within hemimetabolous Heteroptera were simultaneously with those of holometabolous Coleoptera and Diptera which took place in the Triassic. While the aquatic habitat was colonized by Nepomorpha already in the Triassic, the Gerromorpha independently adapted to the semi-aquatic habitat in the Early Jurassic

Low intraspecific aggression level in the polydomous and facultative polygynous ant Ectatomma tuberculatum

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