Hitting the Road: Haplotype Diversity of Fire Ants Nesting on Disturbed Atlantic Forest Habitats.

Ants of the genus Solenopsis are globally distributed, presenting high diversity and many generalist species. In South America, the dominant species is Solenopsis saevissima (Smith, 1855), commonly found nesting in grassy fields surrounding humanized areas. In spite of being so common, there has been no research evaluating the effect of human disturbances on the mitochondrial DNA (mtDNA) haplotype diversity in this species. In this context, we here characterized the mtDNA haplotype diversity in S. saevissima nests by highway roadsides, dust roads, and forest borders of Atlantic Forest, based on partial sequences of cytochrome c oxidase subunit I (COI). Based on the facts that the species is a rapid colonizer of disturbed habitats, we specifically probed how the genetic diversity of native S. saevissima is impacted by highways and roads infrastructure expanding around the rainforest. Species diagnosis was established both by morphological characters and obtained mtDNA COI sequences. Overall, the species exhibited high haplotypes and nucleotide diversity, particularly around forest borders; though all haplotypes seemed closely related across the different habitats. We identified seven mitochondrial haplotypes (H1 to H7), where haplotype H1 was exclusively found in highway roadside nests, and H7 on dust roads; the remaining haplotypes were recorded from all habitats. Haplotype H1 was geographically isolated to the south of the Atlantic Forest, supporting previous suggestions that it acts as a biogeographical barrier. The pattern is suggestive of a recent species expansion, probably resulting from extensive habitat fragmentation. Taken together, our data demonstrates fire ant haplotypes prevailing in some anthropized habitats, characterizing how a native species lining the remnants of the Brazilian Atlantic Forest might be a concern for environmental conservation.

Winged ants (Hymenoptera: Formicidae) presence in twigs on the leaf litter of Atlantic Forest / Colônias de formigas (Hymenoptera: Formicidae) com alados em galhos na serapilheira de Floresta Atlântica

Abstract: In the leaf litter, ants have various nesting resources available, such as live or dead trunks, twigs, leaves, fruits and seeds. On the twigs, there are adults and immature individuals, but also the queen and winged. The production of wings requires time and energy from the colony. The objective of this study was to investigate the presence of winged in ant colonies in twigs on the leaf litter. Our prediction is that the richness and abundance of winged in twigs are the greatest in rainy months. We collected all twigs with ants in 552 plots with 16 m2, totaling 8,832 m2 of leaf litter, in areas located in the Brazilian Atlantic Domain. We compared the species richness and the number of colonies with and without winged, as well as the number of winged over a year. In total, we collected 1,521 twigs with colonies belonging to 92 species of ants. The rate of twigs with winged was low, about 12%. In colonies with winged, the total number of twigs, species and amount of winged does not differ between the months considered dry and rainy. The majority of winged species are leaf litter dwellers, such as Linepithema neotropicum, recorded with the highest amount of winged irrespective of the period. Arboreal species colonized 15% of the twigs and, in 1/3 of these species, winged were recorded as part of the composition of the colony. Although winged represent a small percentage of the colony in twigs, our results indicate that this feature is important for the life cycle of 44% of the species that occupy twigs, considering that winged are fundamental for the dispersion of the colony.

Resumo: Na serapilheira as formigas têm disponíveis diversos recursos de nidificação, como troncos e galhos vivos ou mortos, folhas, frutos e sementes. Nos galhos são encontrados indivíduos adultos e imaturos, mas também rainha e alados. A produção de alados exige tempo e energia por parte da colônia. O objetivo deste estudo foi investigar a presença de alados em colônias de formigas em galhos na serapilheira. Nossa hipótese é que a riqueza e abundância de alados em galhos são maiores nos meses chuvosos. Nós coletamos todos os galhos com formigas em 552 parcelas de 16 m2, totalizando 8.832 m2 de serapilheira em áreas localizadas no Domínio Atlântico brasileiro. Comparamos a riqueza de espécies e o número de galhos com e sem alados, bem como o número de alados ao longo de um ano. No total coletamos 1.521 galhos com colônias, pertencentes a 92 espécies de formigas; a taxa de galhos com alados foi baixa, cerca de 12%. Nas colônias com alados, o número total de galhos, espécies e quantidade de alados não diferem entre os meses secos ou chuvosos. A maioria das espécies com alados é habitante da serapilheira, como Linepithema neotropicum, registrada com a maior quantidade de alados, independente do período. Espécies arborícolas colonizaram 15% dos galhos e, em 1/3 dessas espécies, alados foram registrados fazendo parte da composição da colônia. Apesar de os alados representarem uma pequena porcentagem da colônia em galhos, nossos resultados indicam que este recurso é importante para o ciclo de vida de 50% das espécies que os ocupam, considerando que alados são fundamentais para a dispersão da colônia.